Research IndicatorsGraph generated 16 March 2017 using data from PubMed using criteria.
Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic. Tag cloud generated 16 March, 2017 using data from PubMed, MeSH and CancerIndex
Specific Cancers (1)
Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.
Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).
OMIM, Johns Hopkin University
Referenced article focusing on the relationship between phenotype and genotype.
International Cancer Genome Consortium.
Summary of gene and mutations by cancer type from ICGC
Cancer Genome Anatomy Project, NCI
COSMIC, Sanger Institute
Somatic mutation information and related details
GEO Profiles, NCBI
Search the gene expression profiles from curated DataSets in the Gene Expression Omnibus (GEO) repository.
Latest Publications: TAP2 (cancer-related)
BACKGROUND: Malignant B-cell clones are affected by both acquired genetic alterations and by inherited genetic variations changing the inflammatory tumour microenvironment.
METHODS: We investigated 50 inflammatory response gene polymorphisms in 355 B-cell non-Hodgkin's lymphoma (B-NHL) samples encompassing 216 diffuse large B cell lymphoma (DLBCL) and 139 follicular lymphoma (FL) and 307 controls. The effect of single genes and haplotypes were investigated and gene-expression analysis was applied for selected genes. Since interaction between risk genes can have a large impact on phenotype, two-way gene-gene interaction analysis was included.
RESULTS: We found inherited SNPs in genes critical for inflammatory pathways; TLR9, IL4, TAP2, IL2RA, FCGR2A, TNFA, IL10RB, GALNT12, IL12A and IL1B were significantly associated with disease risk and SELE, IL1RN, TNFA, TAP2, MBL2, IL5, CX3CR1, CHI3L1 and IL12A were, associated with overall survival (OS) in specific diagnostic entities of B-NHL. We discovered noteworthy interactions between DLBCL risk alleles on IL10 and IL4RA and FL risk alleles on IL4RA and IL4. In relation to OS, a highly significant interaction was observed in DLBCL for IL4RA (rs1805010) * IL10 (rs1800890) (HR = 0.11 (0.02-0.50)). Finally, we explored the expression of risk genes from the gene-gene interaction analysis in normal B-cell subtypes showing a different expression of IL4RA, IL10, IL10RB genes supporting a pathogenetic effect of these interactions in the germinal center.
CONCLUSIONS: The present findings support the importance of inflammatory genes in B-cell lymphomas. We found association between polymorphic sites in inflammatory response genes and risk as well as outcome in B-NHL and suggest an effect of gene-gene interactions during the stepwise oncogenesis.
Mehta AM, Spaans VM, Mahendra NB, et al.Differences in genetic variation in antigen-processing machinery components and association with cervical carcinoma risk in two Indonesian populations.
Immunogenetics. 2015; 67(5-6):267-75 [PubMed
] Free Access to Full Article Related Publications
Genetic variation of antigen-processing machinery (APM) components has been shown to be associated with cervical carcinoma risk and outcome in a genetically homogeneous Dutch population. However, the role of APM component single nucleotide polymorphisms (SNPs) in genetically heterogeneous populations with different distributions of human papillomavirus (HPV) subtypes remains unclear. Eleven non-synonymous, coding SNPs in the TAP1, TAP2, LMP2, LMP7 and ERAP1 genes were genotyped in cervical carcinoma patients and healthy controls from two distinct Indonesian populations (Balinese and Javanese). Individual genotype and allele distributions were investigated using single-marker analysis, and combined SNP effects were assessed by haplotype construction and haplotype interaction analysis. Allele distribution patterns in Bali and Java differed in relation to cervical carcinoma risk, with four ERAP1 SNPs and one TAP2 SNP in the Javanese population showing significant association with cervical carcinoma risk, while in the Balinese population, only one TAP2 SNP showed this association. Multimarker analysis demonstrated that in the Javanese patients, one specific haplotype, consisting of the ERAP1-575 locus on chromosome 5 and the TAP2-379 and TAP2-651 loci on chromosome 6, was significantly associated with cervical carcinoma risk (global P = 0.008); no significant haplotype associations were found in the Balinese population. These data indicate not only that genetic variation in APM component genes is associated with cervical carcinoma risk in Indonesia but also that the patterns of association differ depending on background genetic composition and possibly on differences in HPV type distribution.
Sheyhidin I, Hasim A, Zheng F, Ma HEpigenetic changes within the promoter regions of antigen processing machinery family genes in Kazakh primary esophageal squamous cell carcinoma.
Asian Pac J Cancer Prev. 2014; 15(23):10299-306 [PubMed
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The esophageal squamous cell carcinoma (ESCC) is thought to develop through a multi-stage process. Epigenetic gene silencing constitutes an alternative or complementary mechanism to mutational events in tumorigenesis. Posttranscriptional regulation of human leukocyte antigen class I (HLA-I) and antigen processing machinery (APM) proteins expression may be associated with novel epigenetic modifications in cancer development. In the present study, we determined the expression levels of HLA-I antigen and APM components by immunohistochemistry. Then by a bisulfite-sequencing PCR (BSP) approach, we identified target CpG islands methylated at the gene promoter region of APM family genes in a ESCC cell line (ECa109), and further quantitative analysis of CpG site specific methylation of these genes in cases of Kazakh primary ESCCs with corresponding non-cancerous esophageal tissues using the Sequenom MassARRAY platform. Here we showed that the development of ESCCs was accompanied by partial or total loss of protein expression of HLA-B, TAP2, LMP7, tapasin and ERp57. The results demonstrated that although no statistical significance was found of global target CpG fragment methylation level sof HLA-B, TAP2, tapasin and ERp57 genes between ESCC and corresponding non-cancerous esophageal tissues, there was significant differences in the methylation level of several single sites between the two groups. Of thesse only the global methylation level of LMP7 gene target fragments was statistically higher (0.0517±0.0357) in Kazakh esophageal cancer than in neighboring normal tissues (0.0380±0.0214, p<0.05). Our results suggest that multiple CpG sites, but not methylation of every site leads to down regulation or deletion of gene expression. Only some of them result in genetic transcription, and silencing of HLA-B, ERp57, and LMP7 expression through hypermethylation of the promoters or other mechanisms may contribute to mechanisms of tumor escape from immune surveillance in Kazakh esophageal carcinogenesis.
BACKGROUND: Partner of Sld five 3 (PSF3) is a member of the evolutionarily conserved heterotetrameric complex "Go-Ichi-Ni-San" (GINS), which consists of SLD5, PSF1, PSF2, and PSF3. Previous studies have suggested that some GINS complex members are upregulated in cancer, but the status of PSF3 expression in colorectal cancer has not been investigated.
METHODS: We investigated the status of PSF3 expression in 137 consecutive resected colorectal caners by quantitative reverse-transcription polymerase chain reaction. Univariable and multivariable Cox regression analyses were performed to assess independent prognostic factors for overall survival in colorectal cancer.
RESULTS: In 137 restected colorectal cancer samples, median messenger RNA (mRNA) expression levels of PSF3 were significantly higher in tumor tissues (1.35 × 10(-3), range 2.88 × 10(-4) to 3.16 × 10(-2)) than in adjacent normal tissues (2.94 × 10(-4), range 5.48 × 10(-5) to 1.27 × 10(-3)) (P < 0.05). Moreover, high expression of PSF3 in tumor tissues was associated with shorter disease-free survival and overall survival. When analyzed with a Cox regression model, the PSF3 expression was an independent prognostic factor for overall survival. In addition, in patients with early stage (stage I and II) colorectal cancer, the overall survival rate of the high PSF3 expression group was significantly lower than that of the low PSF3 expression group (P < 0.001).
CONCLUSIONS: The PSF3 expression plays an important role in the progression of colorectal cancer and acts as a factor significantly affecting the prognosis of patients.
VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_217.
BACKGROUND: Transporter associated with antigen processing (TAP) is responsible for peptide loading onto class I major histocompatibility complex (MHC-I) molecules. TAP seems to facilitate the detection of HPV by MHC-I molecules and contributes to successful eradication of HPV. TAP polymorphisms could have an important impact on the course of HPV infection.
OBJECTIVE: The aim of this study is to evaluate the association between five TAP gene polymorphisms and the risk of CIN. Methods. This case-control study investigated five common TAP polymorphisms in TAP1 (1341 and 2254) and TAP2 (1135, 1693, and 1993) in 616 women with CIN and 206 controls. Associations between gene polymorphisms and risk of CIN were analysed by univariate and multivariable models. The combined effect of the five TAP gene polymorphisms on the risk for CIN was investigated by haplotype analysis.
RESULTS: No significant difference in genotype distribution of the five TAP polymorphisms was observed in women with CIN and controls. Haplotype analysis revealed that women with haplotype mut-wt-wt-wt-wt (TAP polymorphisms t1135-t1341-t1693-t1993-t2254) had a significantly lower risk for CIN, compared to women with the haplotype wt-wt-wt-wt-wt (P = 0.006; OR 0.5 [0.35-0.84]).
CONCLUSION: Identification of this haplotype combination could be used to identify women, less susceptible for development of CIN following HPV infection.
Ozbas-Gerceker F, Bozman N, Gezici S, et al.Association of TAP1 and TAP2 gene polymorphisms with hematological malignancies.
Asian Pac J Cancer Prev. 2013; 14(9):5213-7 [PubMed
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Transporter associated with antigen presenting (TAP) 1 and TAP2 genes are localized in the major histocompatability complex (MHC) class II region and form a heterodimer playing a key role in endogenous pathways for antigen presentation. Defects of these genes have been reported to be common in different types of cancer. Polymorphisms identified in these loci have also been investigated and reported to be associated with several autoimmune disorders, viral infections and neoplasms. In the present study, for the first time, the allele and genotype frequencies of TAP1-333, TAP2-565, TAP2-651 and TAP2-665 were determined in patients with hematological malignancies (HM) using a PCR-RFLP method and compared with the frequencies in the control group. Our results suggested an association of TAP1-333 polymorphism with multiple myeloma-MM and TAP2- 565 polymorphism with chronic lymphoid leukemia-CLL. In addition, it could be concluded that the TAP2-665 GG genotype might be a risk factor for all types of hematological malignancies included in this study.
BACKGROUND: Hyaluronan (HA) an important component of the extracellular matrix, has been linked to tumor progression and drug resistance in several malignancies. However, limited data is available for ovarian cancer. This study investigated the role of hyaluronan (HA) and a potential link between the HA-CD44 pathway and membrane ATP binding cassette (ABC) transporter proteins in ovarian cancer chemoresistance.
METHODS: We investigated the ability of HA to block the cytotoxic effects of the chemotherapy drug carboplatin, and to regulate the expression of ABC transporters in ovarian cancer cells. We also examined HA serum levels in ovarian cancer patients prior to and following chemotherapy and assessed its prognostic relevance.
RESULTS: HA increased the survival of carboplatin treated ovarian cancer cells expressing the HA receptor, CD44 (OVCAR-5 and OV-90). Carboplatin significantly increased expression of HAS2, HAS3 and ABCC2 and HA secretion in ovarian cancer cell conditioned media. Serum HA levels were significantly increased in patients following platinum based chemotherapy and at both 1st and 2nd recurrence when compared with HA levels prior to treatment. High serum HA levels (>50 μg/ml) prior to chemotherapy treatment were associated with significantly reduced progression-free (P = 0.014) and overall survival (P = 0.036). HA production in ovarian cancer cells was increased in cancer tissues collected following chemotherapy treatment and at recurrence. Furthermore HA treatment significantly increased the expression of ABC drug transporters (ABCB3, ABCC1, ABCC2, and ABCC3), but only in ovarian cancer cells expressing CD44. The effects of HA and carboplatin on ABC transporter expression in ovarian cancer cells could be abrogated by HA oligomer treatment. Importantly, HA oligomers increased the sensitivity of chemoresistant SKOV3 cells to carboplatin.
CONCLUSIONS: Our findings indicate that carboplatin chemotherapy induces HA production which can contribute to chemoresistance by regulating ABC transporter expression. The HA-CD44 signaling pathway is therefore a promising target in platinum resistant ovarian cancer.
Leone P, Shin EC, Perosa F, et al.MHC class I antigen processing and presenting machinery: organization, function, and defects in tumor cells.
J Natl Cancer Inst. 2013; 105(16):1172-87 [PubMed
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The surface presentation of peptides by major histocompatibility complex (MHC) class I molecules is critical to all CD8(+) T-cell adaptive immune responses, including those against tumors. The generation of peptides and their loading on MHC class I molecules is a multistep process involving multiple molecular species that constitute the so-called antigen processing and presenting machinery (APM). The majority of class I peptides begin as proteasome degradation products of cytosolic proteins. Once transported into the endoplasmic reticulum by TAP (transporter associated with antigen processing), peptides are not bound randomly by class I molecules but are chosen by length and sequence, with peptidases editing the raw peptide pool. Aberrations in APM genes and proteins have frequently been observed in human tumors and found to correlate with relevant clinical variables, including tumor grade, tumor stage, disease recurrence, and survival. These findings support the idea that APM defects are immune escape mechanisms that disrupt the tumor cells' ability to be recognized and killed by tumor antigen-specific cytotoxic CD8(+) T cells. Detailed knowledge of APM is crucial for the optimization of T cell-based immunotherapy protocols.
El Hage F, Durgeau A, Mami-Chouaib FTAP expression level in tumor cells defines the nature and processing of MHC class I peptides for recognition by tumor-specific cytotoxic T lymphocytes.
Ann N Y Acad Sci. 2013; 1283:75-80 [PubMed
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We identified that the antigen preprocalcitonin (ppCT) is recognized on a human lung carcinoma by a cytotoxic T lymphocyte clone derived from autologous tumor-infiltrating lymphocytes. The antigenic peptide ppCT(16-25) is encoded by the gene calcitonin-related polypeptide alpha (CALCA), which codes for CT and is overexpressed in several lung carcinomas compared with normal tissues. The ppCT peptide is derived from the C-terminal region of the signal peptide and is processed independently of proteasomes and the transporter associated with antigen processing (TAP)1/TAP2 heterodimeric complexes. Instead, processing occurs within the endoplasmic reticulum by a novel mechanism involving signal pepsidase (SP) and signal peptide peptidase (SPP). Although lung cancer cells bearing the ppCT(16-25) epitope displayed low levels of TAP, restoration of TAP expression by interferon (IFN)-γ treatment or by TAP1/TAP2 gene transfer inhibited ppCT antigen presentation. Thus, the ppCT(16-25) human tumor epitope requires low TAP expression for efficient presentation. These results indicate that emerging SP-generated peptides represent alternative T cell targets that permit cytotoxic T lymphocytes to destroy TAP-impaired tumors, a process that helps to overcome tumor escape from CD8(+) T cell immunity. Additionally, our data suggest that ppCT is a promising candidate for cancer immunotherapy.
Skov V, Riley CH, Thomassen M, et al.Whole blood transcriptional profiling reveals significant down-regulation of human leukocyte antigen class I and II genes in essential thrombocythemia, polycythemia vera and myelofibrosis.
Leuk Lymphoma. 2013; 54(10):2269-73 [PubMed
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Gene expression profiling studies in the Philadelphia-negative chronic myeloproliferative neoplasms have revealed significant deregulation of several immune and inflammation genes that might be of importance for clonal evolution due to defective tumor immune surveillance. Other mechanisms might be down-regulation of major histocompatibility (MHC) class I and II genes, which are used by tumor cells to escape antitumor T-cell-mediated immune responses. We have performed whole blood transcriptional profiling of genes encoding human leukocyte antigen (HLA) class I and II molecules, β2-microglobulin and members of the antigen processing machinery of HLA class I molecules (LMP2, LMP7, TAP1, TAP2 and tapasin). The findings of significant down-regulation of several of these genes may possibly be of major importance for defective tumor immune surveillance. Since up-regulation of HLA genes is recorded during treatment with epigenome modulating agents (DNA-hypomethylators and DNA-hyperacetylators [histone deacetylase inhibitors]) and interferon-α2, our findings call for prospective transcriptional studies of HLA genes during treatment with these agents.
Eto M, Kamba T, Miyake H, et al.STAT3 polymorphism can predict the response to interferon-α therapy in patients with metastatic renal cell carcinoma.
Eur Urol. 2013; 63(4):745-52 [PubMed
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BACKGROUND: In our 2007 retrospective study, we reported that single nucleotide polymorphisms (SNPs) in the signal transducer and activator of transcription 3 (acute-phase response factor) (STAT3) gene were significantly associated with better response to interferon (IFN)-α in patients with metastatic renal cell carcinoma (mRCC).
OBJECTIVE: To prospectively confirm those results, the Japan Immunotherapy SNPs-Study Group for Kidney Cancer conducted this trial.
DESIGN, SETTING, AND PARTICIPANTS: In this multicenter, prospective study, 203 eligible patients were enrolled. We evaluated the correlation between the antitumor effects of IFN-α and 11 SNPs (STAT3-2, STAT3-0, SOCS3-1, IL4R-34, PTGS1-3, PTGS1-4, PTGS1-5, PTGS2-12, IRF2-67, ICSBP-38, and TAP2-5) in eight genes in 180 patients who received IFN-α for >12 wk.
INTERVENTIONS: Patients were treated with three doses per week of IFN-α 5 million IU.
OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: We analyzed the association of response to IFN-α and overall survival (OS) with genetic polymorphisms using a chi-square test and a logistic regression model.
RESULTS AND LIMITATIONS: The response rate of IFN-α was 13.8% (28 of 203 patients; 9 complete responses [CRs], 19 partial responses [PRs]). The CR rate of 4.4% was higher than we expected. Response to IFN-α was not associated with any of the 11 SNPs examined. However, when we assessed patients with CR, PR, and stable disease >24 wk as a group representing those with clinical response, a significant association was observed between STAT3-2 (rs1905341) and the clinical response of IFN-α (p=0.039). Namely, C/C genotype of STAT3-2 was significantly associated with the clinical response of IFN-α and OS. These results were generated in Japanese patients and should be studied in other ethnic groups.
CONCLUSIONS: This is the first prospective study demonstrating that a STAT3 polymorphism can be a predictive marker for treatment with IFN-α for patients with mRCC.
Human prostate tumor vaccine and gene therapy trials using ex vivo methods to prime dendritic cells (DCs) with prostate specific membrane antigen (PSMA) have been somewhat successful, but to date the lengthy ex vivo manipulation of DCs has limited the widespread clinical utility of this approach. Our goal was to improve upon cancer vaccination with tumor antigens by delivering PSMA via a CD40-targeted adenovirus vector directly to DCs as an efficient means for activation and antigen presentation to T-cells. To test this approach, we developed a mouse model of prostate cancer by generating clonal derivatives of the mouse RM-1 prostate cancer cell line expressing human PSMA (RM-1-PSMA cells). To maximize antigen presentation in target cells, both MHC class I and TAP protein expression was induced in RM-1 cells by transduction with an Ad vector expressing interferon-gamma (Ad5-IFNγ). Administering DCs infected ex vivo with CD40-targeted Ad5-huPSMA, as well as direct intraperitoneal injection of the vector, resulted in high levels of tumor-specific CTL responses against RM-1-PSMA cells pretreated with Ad5-IFNγ as target cells. CD40 targeting significantly improved the therapeutic antitumor efficacy of Ad5-huPSMA encoding PSMA when combined with Ad5-IFNγ in the RM-1-PSMA model. These results suggest that a CD-targeted adenovirus delivering PSMA may be effective clinically for prostate cancer immunotherapy.
Hasim A, Abudula M, Aimiduo R, et al.Post-transcriptional and epigenetic regulation of antigen processing machinery (APM) components and HLA-I in cervical cancers from Uighur women.
PLoS One. 2012; 7(9):e44952 [PubMed
] Free Access to Full Article Related Publications
Normal function of human leukocyte antigen class I (HLA-I) and antigen processing machinery (APM) proteins is required for T cell-mediated anti-tumor or antiviral immunity, whereas the tumor survival indicates a failure of the host in immune surveillance associated with the dysfunction in antigen presentation, mainly due to the deregulation in HLA-I and APM expression or function. The posttranscriptional regulation of HLA-I and APM expression may associate with epigenetic modifications in cancer development which was not described so far. Here we showed that the development of cervical intraepithelial neoplasia (CIN) and cervical squamous cell carcinoma (CSCC) in Uighur women was accompanied with the partial or total loss of protein expression of HLA-I, ß2-m and APM components, including the transporter associated with antigen processing (TAP1/2), low molecular mass protein (LMP2, LMP7), endoplasmic reticulum aminopeptidase 1(ERAP1), chaperone molecules include calreticulin (CLR), calnexin (CNX) and ERp57, and this was proved again by analysis of transcription of the same genes in addition to three genes HLA-A, B and C coding for HLA-I. By bisulfite sequencing approach, we identified target CpG islands methylated at the gene promoter region of TAP1, TAP2, LMP7, tapasin and ERp57 in cervical carcinoma cells. Further analysis of CpG site specific methylation of these genes in cases of CSCC and CIN demonstrated an inverse correlation of altered CpG island methylation of TAP1, LMP7, and ERp57 with changes in protein expression. Moreover, promoter methylation of these genes was significantly higher in cases positive for human papillomavirus 16 (HPV 16) than negative ones. Our results suggested that epigenetic modifications are responsible for the aberrant expression of certain HLA-I and APM genes, and may help to understand unrevealed mechanisms of tumor escape from immune surveillance in cervical carcinogenesis.
Qiu B, Huang B, Wang X, et al.Association of TAP1 and TAP2 polymorphisms with the outcome of persistent HBV infection in a northeast Han Chinese population.
Scand J Gastroenterol. 2012; 47(11):1368-74 [PubMed
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OBJECTIVE: Transporter associated with antigen processing (TAP) plays a central role in a cellular immune response against HBV. Polymorphisms exist at the coding region of TAP and alter its structure and function. The aim of this study was to evaluate the potential relationship between polymorphisms of TAP and different outcomes of persistent HBV infection in a Han population in northeastern China.
MATERIAL AND METHODS: 189 HBV spontaneously recovered (SR) subjects, 571 HBV-infected patients including 180 chronic hepatitis B (CHB), 196 liver cirrhosis (LC) and 195 hepatocellular carcinoma (HCC) individuals were included in this study. TAP1-333 Ile/Val and -637 Asp/Gly, TAP2-651 Arg/Cys and -687 Stop/Gln were genotyped in all the samples by using a PCR-RFLP method.
RESULTS: The frequency of TAP1-637-Gly (allele G) was significantly higher in persistently HBV-infected individuals (CHB and LC) than that of SR subjects (OR = 1.58, 95% CI 1.12-2.45, p = 0.024; OR = 1.78, 95% CI 1.27-2.68, p = 0.002) by a logistic regression analysis. In addition, the statistically significant difference in the distribution of TAP2-651-Cys (allele T) was observed between HCC cases and SR controls (OR = 2.30, 95% CI 1.51-3.72, p < 0.001), and TAP2-687-Gln (allele C) in CHB patients was more common than that in SR subjects (OR = 1.41, 95% CI 1.13-1.97, p = 0.021). The data also revealed that haplotype 687 Gln-651 Cys-637 Gly-333 Ile was strongly associated with persistent HBV infection (CHB, LC and HCC) (p < 0.001, < 0.05 and < 0.001, respectively).
CONCLUSION: These results suggested that TAP variants were likely to play a substantial role in different outcomes of persistent HBV infection in the studied population.
Cerhan JR, Fredericksen ZS, Novak AJ, et al.A two-stage evaluation of genetic variation in immune and inflammation genes with risk of non-Hodgkin lymphoma identifies new susceptibility locus in 6p21.3 region.
Cancer Epidemiol Biomarkers Prev. 2012; 21(10):1799-806 [PubMed
] Free Access to Full Article Related Publications
BACKGROUND: Non-Hodgkin lymphoma (NHL) is a malignancy of lymphocytes, and there is growing evidence for a role of germline genetic variation in immune genes in NHL etiology.
METHODS: To identify susceptibility immune genes, we conducted a 2-stage analysis of single-nucleotide polymorphisms (SNP) from 1,253 genes using the Immune and Inflammation Panel. In Stage 1, we genotyped 7,670 SNPs in 425 NHL cases and 465 controls, and in Stage 2 we genotyped the top 768 SNPs on an additional 584 cases and 768 controls. The association of individual SNPs with NHL risk from a log-additive model was assessed using the OR and 95% confidence intervals (CI).
RESULTS: In the pooled analysis, only the TAP2 coding SNP rs241447 (minor allele frequency = 0.26; Thr655Ala) at 6p21.3 (OR = 1.34, 95% CI 1.17-1.53) achieved statistical significance after accounting for multiple testing (P = 3.1 × 10(-5)). The TAP2 SNP was strongly associated with follicular lymphoma (FL, OR = 1.82, 95%CI 1.46-2.26; p = 6.9 × 10(-8)), and was independent of other known loci (rs10484561 and rs2647012) from this region. The TAP2 SNP was also associated with diffuse large B-cell lymphoma (DLBCL, OR = 1.38, 95% CI 1.08-1.77; P = 0.011), but not chronic lymphocytic leukemia (OR = 1.08; 95% CI 0.88-1.32). Higher TAP2 expression was associated with the risk allele in both FL and DLBCL tumors.
CONCLUSION: Genetic variation in TAP2 was associated with NHL risk overall, and FL risk in particular, and this was independent of other established loci from 6p21.3.
IMPACT: Genetic variation in antigen presentation of HLA class I molecules may play a role in lymphomagenesis.
Stölzel F, Hackmann K, Kuithan F, et al.Clonal evolution including partial loss of human leukocyte antigen genes favoring extramedullary acute myeloid leukemia relapse after matched related allogeneic hematopoietic stem cell transplantation.
Transplantation. 2012; 93(7):744-9 [PubMed
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BACKGROUND: Relapse of acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (HSCT) leaves few therapeutic options, and mechanisms of immune escape of recurring leukemic cells remain poorly understood. Recently, acquired loss of mismatched human leukocyte antigen (HLA) was demonstrated in patients with AML undergoing haploidentical allogeneic HSCT and was suggested not to occur in HLA-matched HSCT. We hypothesized that this mechanism applies to extramedullary AML relapse which occurs frequently after allogeneic HSCT and might also not be restricted to haploidentical HSCT.
METHODS: DNA from extramedullary AML relapse after HSCT was compared with bone marrow at diagnosis with array comparative genomic hybridization to investigate relapse-specific genomic aberrations in relapsing AML after allogeneic HSCT. Formalin-fixed, paraffin-embedded tissues from the same points of time were assessed for HLA, major histocompatibility complex class I chain-related gene A, and TAP2 immunohistochemistry staining to assess cell surface expression of deleted loci encoded on chromosome 6p.
RESULTS: Array comparative genomic hybridization revealed a partial loss of chromosome 6p in extramedullary myeloid sarcoma relapse of AML after sustained complete remission was achieved through matched related allogeneic HSCT. Among others, a deleted region 6p21.32-p21.33, which included several HLA class I genes, was detected.
CONCLUSIONS: These results suggest that the loss of HLA class I haplotype also occurs in AML relapse after HLA-matched related HSCT. Partial loss of several HLA class I genes and subsequent reduced presentation of minor histocompatibility antigens and reduced ligation of activating natural killer-cell receptors may explain the loss of graft-versus-leukemia response and extramedullary AML relapse in tissue with reduced immunologic surveillance.
Bernal M, García-Alcalde F, Concha A, et al.Genome-wide differential genetic profiling characterizes colorectal cancers with genetic instability and specific routes to HLA class I loss and immune escape.
Cancer Immunol Immunother. 2012; 61(6):803-16 [PubMed
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AIM: We compared the expression of genes related to inflammatory and cytotoxic functions between MSI and MSS (HLA-class I-negative and HLA-class I-positive) colorectal cancers (CRCs), seeking evidence of differences in inflammatory mediators and cytotoxic T-cell responses. Twenty-two CRCs were divided into three study groups as a function of HLA class I expression and MSI phenotype: 8 MSI tumours, 6 MSS/HLA- tumours and 6 MSS/HLA+ tumours (controls).
FINDINGS: A first comparison between eight MSI and six MSS/HLA-positive (control) cancers, based on microarray analysis on an Affymetrix(®) HG-U133-Plus-PM plate, identified 1974 differentially expressed genes (P < 0.05). We grouped genes in Gene Ontology functional categories: apoptotic programme (72 genes, P = 5.5·10(-3)), leucocyte activation (43 genes, P = 1.8·10(-5)), T-cell activation (24 genes, P = 6.3·10(-4)), inflammatory response (40 genes, 2.3·10(-2)) and cytokine production (10 genes, P = 1.9·10(-2)). Real-time PCR and immunohistochemical evaluation were used to validate the data, finding that increased mRNA levels of pro-inflammatory cytokines and cytotoxic mediators were associated with greater infiltration by CD8+T lymphocytes in the MSI group (P < 0.001). Finally, HLA-class I-negative tumours were not grouped together but rather in accordance with features of the gene expression profile of MSI or MSS tumours. As expected, genes associated with antigen processing machinery and MHC class I molecules (TAP2, B2m) were downregulated in MSS/HLA-class I-negative CRCs (n = 6) in comparison to controls.
CONCLUSIONS: In conclusion, microarray and immunohistochemical data may be useful to comprehensively assess tumour-host interactions and differentiate MSI from MSS cancers. The two types of tumour, MSI/HLA-class I-negative and MSS/HLA-class I-negative, showed marked differences in the composition and intensity of infiltrating leucocytes, suggesting that their immune escape strategies involve distinct pathways.
Fellerhoff B, Gu S, Laumbacher B, et al.The LMP7-K allele of the immunoproteasome exhibits reduced transcript stability and predicts high risk of colon cancer.
Cancer Res. 2011; 71(23):7145-54 [PubMed
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Destruction of cancer cells by cytotoxic T lymphocytes depends on immunogenic tumor peptides generated by proteasomes and presented by human leukocyte antigen (HLA) molecules. Functional differences arising from alleles of immunoproteasome subunits have not been recognized so far. We analyzed the genetic polymorphism of the immunoproteasome subunits LMP2 and LMP7 and of the transporters associated with antigen processing (TAP1 and TAP2) in two independently collected panels of colorectal carcinoma patients (N(1) = 112, N(2) = 62; controls, N = 165). High risk of colon cancer was associated with the LMP7-K/Q genotype (OR = 8.10, P = 1.10 × 10(-11)) and low risk with the LMP7-Q/Q genotype (OR = 0.10, P = 5.97 × 10(-13)). The basis for these distinct associations of LMP7 genotypes was functionally assessed by IFN-γ stimulation of colon carcinoma cell lines (N = 10), followed by analyses of mRNA expression of HLA class I, TAP1, TAP2, and LMP7, with real-time PCR. Whereas induction of HLA-B, TAP1, and TAP2 was comparable in all cell lines, transcript amounts of LMP7-Q increased 10-fold, but of LMP7-K only 3.8-fold. This correlated with a reduced transcript stability of LMP7-K (t(1/2) ≈ 7 minutes) compared with LMP7-Q (t(1/2) ≈ 33 minutes). In addition, LMP7-Q/Q colon carcinoma cells increased (the peptide based) HLA class I surface expression significantly after IFN-γ stimulation, whereas LMP7-Q/K and LMP7-K/K carcinoma cells showed minimal (<20%) changes. These results suggest that the presence of LMP7-K can reduce the formation of immunoproteasomes and thus peptide processing, followed by reduced peptide-HLA presentation, a crucial factor in the immune response against cancer.
Durgeau A, El Hage F, Vergnon I, et al.Different expression levels of the TAP peptide transporter lead to recognition of different antigenic peptides by tumor-specific CTL.
J Immunol. 2011; 187(11):5532-9 [PubMed
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Decreased antigenicity of cancer cells is a major problem in tumor immunology. This is often acquired by an expression defect in the TAP. However, it has been reported that certain murine Ags appear on the target cell surface upon impairment of TAP expression. In this study, we identified a human CTL epitope belonging to this Ag category. This epitope is derived from preprocalcitonin (ppCT) signal peptide and is generated within the endoplasmic reticulum by signal peptidase and signal peptide peptidase. Lung cancer cells bearing this antigenic peptide displayed low levels of TAP, but restoration of their expression by IFN-γ treatment or TAP1 and TAP2 gene transfer abrogated ppCT Ag presentation. In contrast, TAP upregulation in the same tumor cells increased their recognition by proteasome/TAP-dependent peptide-specific CTLs. Thus, to our knowledge, ppCT(16-25) is the first human tumor epitope whose surface expression requires loss or downregulation of TAP. Lung tumors frequently display low levels of TAP molecules and might thus be ignored by the immune system. Our results suggest that emerging signal peptidase-generated peptides represent alternative T cell targets, which permit CTLs to destroy TAP-impaired tumors and thus overcome tumor escape from CD8(+) T cell immunity.
Bormann F, Sers C, Seliger B, et al.Methylation-specific ligation detection reaction (msLDR): a new approach for multiplex evaluation of methylation patterns.
Mol Genet Genomics. 2011; 286(3-4):279-91 [PubMed
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A new sensitive method for multiplex gene-specific methylation analysis was developed using a ligation-based approach combined with a TaqMan-based detection and readout employing universal reporter probes. The approach, termed methylation-specific Ligation Detection Reaction (msLDR), was applied to test 16 loci in 8 different colorectal cancer cells in parallel. These loci encode immune regulatory genes involved in T-cell and natural killer cell activation, whose silencing is associated with the development or progression of colorectal cancer. Parallel analysis of HLA-A, HLA-B, STAT1, B2M, LMP2, LMP7, PA28α, TAP1, TAP2, TAPBP, ULBP2 and ULBP3 by msLDR in eight colorectal cancer cell lines showed preferential methylation at the HLA-B, ULBP2 and ULBB3 loci, but not at the other loci. MsLDR was found to represent a suitable and sensitive method for the detection of distinct methylation patterns as validated by conventional bisulphite Sanger sequencing and COBRA analysis. Since gene silencing by epigenetic mechanisms plays a central role during transformation of a normal differentiated somatic cell into a cancer cell, characterization of the gene methylation status in tumours is a major topic not only in basic research, but also in clinical diagnostics. Due to a very simple workflow, msLDR is likely to be applicable to clinical samples and thus comprises a potential diagnostic tool for clinical purposes.
Many cancers escape host immunity without losing tumor-specific rejection antigens or MHC class I expression. This study tracks the evolution of one such cancer that developed in a mouse following exposure to ultraviolet light. The primary autochthonous tumor was not highly malignant and was rejected when transplanted into naïve immunocompetent mice. Neoplastic cells isolated from the primary tumor were susceptible to the growth-inhibitory effects of IFNγ in vitro, but expressed very low levels of MHC I antigen and were resistant to tumor-specific T cells unless they were first exposed to IFNγ. Serial passage of the primary tumor cells in vivo led to a highly aggressive variant that caused fast-growing tumors in normal mice. In vitro, the variant tumor cells showed increased resistance to the growth-inhibitory effects of IFNγ but expressed high levels of immunoproteasomes and MHC I molecules and were susceptible to tumor-specific T cells even without prior exposure to IFNγ.
BACKGROUND: Picropodophyllin (PPP) is a promising novel anti-neoplastic agent that efficiently kills tumor cells in vitro and causes tumor regression and increased survival in vivo. We have previously reported that PPP treatment induced moderate tolerance in two out of 10 cell lines only, and here report the acquired genomic and expression alterations associated with PPP selection over 1.5 years of treatment.
METHODOLOGY/PRINCIPAL FINDINGS: Copy number alterations monitored using metaphase and array-based comparative genomic hybridization analyses revealed largely overlapping alterations in parental and maximally tolerant cells. Gain/amplification of the MYC and PVT1 loci in 8q24.21 were verified on the chromosome level. Abnormalities observed in connection to PPP treatment included regular gains and losses, as well as homozygous losses in 10q24.1-q24.2 and 12p12.3-p13.2 in one of the lines and amplification at 5q11.2 in the other. Abnormalities observed in both tolerant derivatives include amplification/gain of 5q11.2, gain of 11q12.1-q14.3 and gain of 13q33.3-qter. Using Nexus software analysis we combined the array-CGH data with data from gene expression profilings and identified genes that were altered in both inputs. A subset of genes identified as downregulated (ALDH1A3, ANXA1, TLR4 and RAB5A) or upregulated (COX6A1, NFIX, ME1, MAPK and TAP2) were validated by siRNA in the tolerant or parental cells to alter sensitivity to PPP and confirmed to alter sensitivity to PPP in further cell lines.
CONCLUSIONS: Long-term PPP selection lead to altered gene expression in PPP tolerant cells with increase as well as decrease of genes involved in cell death such as PTEN and BCL2. In addition, acquired genomic copy number alterations were observed that were often reflected by altered mRNA expression levels for genes in the same regions.
Milano F, Guarriera M, Rygiel AM, Krishnadath KKTrastuzumab mediated T-cell response against HER-2/neu overexpressing esophageal adenocarcinoma depends on intact antigen processing machinery.
PLoS One. 2010; 5(8):e12424 [PubMed
] Free Access to Full Article Related Publications
BACKGROUND: Esophageal adenocarcinoma (EAC) is a highly aggressive disease with poor prognosis, which frequently exhibits HER-2 gene amplification. Trastuzumab, the humanized antibody against HER-2, has potent growth inhibitory effects on HER-2 overexpressing cancers. One effect of trastuzumab is that it causes HER-2 receptor internalization and degradation, enhancing presentation of HER-2 epitopes on MHC-Class I molecules. This enhances the ability of HER-2 specific cytotoxic T lymphocytes (CTLs) to recognize and kill cancer cells. Novel strategies targeting the HER-2 receptor either directly by trastuzumab and/or indirectly by inducing a CTL response against HER-2 epitopes with, for instance, DC immunotherapy and consequently combining these strategies might prove to be very effective.
METHODOLOGY/PRINCIPAL FINDINGS: In this study we report that trastuzumab has potent growth inhibitory effects on two HER-2 overexpressing EAC cell lines OE33 and OE19. However, we found that trastuzumab and HER-2 specific CTLs act synergistically in inducing tumor lysis in OE33 but not in OE19. We discovered that in OE19 this deficient response is due to a down-regulation of the Transporter Associated with Antigen Processing-2 (TAP-2). TAP-2 is an important member of the Antigen Processing Machinery (APM), and is one of the essential elements for loading antigens on MHC class I molecules. Importantly, we demonstrated that by inducing re-expression of TAP-2 in OE19 with INF-γ treatment or by incubating the cells with INF-γ producing CTLs, the specific anti HER-2 CTL tumor lysis response and synergistic effect with trastuzumab can be restored.
CONCLUSION: An inefficient response of HER-2 overexpressing EAC to trastuzumab and/or DC immunotherapy can be due to a down-regulated TAP-2 expression and thus a deficient APM. Future studies combining trastuzumab with IFN-γ and/or immune-therapies inducing potent anti HER-2 CTL responses could lead to an effective combinatorial strategy for successful treatment of HER-2 overexpressing but APM defective cancers.
Bandoh N, Ogino T, Katayama A, et al.HLA class I antigen and transporter associated with antigen processing downregulation in metastatic lesions of head and neck squamous cell carcinoma as a marker of poor prognosis.
Oncol Rep. 2010; 23(4):933-9 [PubMed
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HLA class I antigen processing machinery plays a crucial role in the generation of peptides from endogeneously synthesized proteins and in their presentation to cytotoxic T lymphocytes. The purpose of this study was to analyze the downregulation of HLA class I antigen, transporter associated with antigen processing (TAP) and tapasin in primary and metastatic lesions of head and neck squamous cell carcinoma (HNSCC) and to compare TAP, tapasin and HLA class I antigen downregulation in metastatic lesions with that of primary lesions. We analyzed expression levels of TAP1, TAP2, tapasin and HLA class I antigen in 25 primary and autologous metastatic lesions by staining formalin-fixed, paraffin-embedded tissue sections in the immunoperoxidase reaction. We identified the expression levels of TAP1, TAP2, tapasin and HLA class I antigen were coordinately downregulated in both primary and metastatic lesions and were significantly lower in metastatic lesions than in autologous primary lesions tested. HLA class I antigen downregulation in metastatic lesion was significantly associated with reduced disease-free survival of patients (P<0.05). Multivariate Cox proportional hazards model analysis identified negativity of HLA class I antigen as an independent prognostic marker. HLA class I antigen and TAP are likely to be downregulated in metastatic lesions compared with primary lesions in HNSCC. The higher frequency of HLA class I antigen and TAP down-regulation in metastases play a role in the clinical course of the disease.
Nagahama Y, Ueno M, Haraguchi N, et al.PSF3 marks malignant colon cancer and has a role in cancer cell proliferation.
Biochem Biophys Res Commun. 2010; 392(2):150-4 [PubMed
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PSF3 (partner of Sld five 3) is a member of the tetrameric complex termed GINS, composed of SLD5, PSF1, PSF2, and PSF3, and well-conserved evolutionarily. Previous studies suggested that some GINS complex members are upregulated in cancer, but PSF3 expression in colon carcinoma has not been investigated. Here, we established a mouse anti-PSF3 antibody, and examined PSF3 expression in human colon carcinoma cell lines and colon carcinoma specimens. We found that PSF3 is expressed in the crypt region in normal colonic mucosa and that many PSF3-positive cells co-expressed Ki-67. This suggests that PSF3-positivity of normal mucosa is associated with cell proliferation. Expression of the PSF3 protein was greater in carcinoma compared with the adjacent normal mucosa, and even stronger in high-grade malignancies, suggesting that it may be associated with colon cancer progression. PSF3 gene knock-down in human colon carcinoma cell lines resulted in growth inhibition characterized by delayed S-phase progression. These results suggest that PSF3 is a potential biomarker for diagnosis of progression in colon cancer and could be a new target for cancer therapy.
Auner V, Sehouli J, Oskay-Oezcelik G, et al.ABC transporter gene expression in benign and malignant ovarian tissue.
Gynecol Oncol. 2010; 117(2):198-201 [PubMed
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OBJECTIVE: ATP-binding Cassette (ABC) transporters are thought to cause multiple drug resistance (MDR) in various carcinomas. Gene expression data from individual transporters in ovarian cancer tissue is contradictory and also scarce for some of them. RNA levels of a panel of ABC transporters were collected and analyzed to get a more detailed overview which transporters are of importance in resistance to chemotherapeutic agents in ovarian carcinoma.
METHODS: Real-time PCR was used to determine RNA expression levels of 9 ABC transporters in 50 benign tissue samples and 50 recurrent ovarian cancer samples. Genes exhibiting a significant difference between those two groups were further evaluated in 50 primary cancer samples. Data were analyzed with receiver operating characteristic (ROC) curves and multiple Wilcoxon-Mann-Whitney U-tests with Shaffer correction.
RESULTS: Gene expression of four transporters (ABCC1, ABCC2, ABCC3, and ABCB3) was significantly elevated in recurrent cancer lesions compared to benign tissue. Expression levels of these 4 ABC transporters were further analyzed in primary ovarian cancer lesions. A significant difference between primary and recurrent tumor tissue was found in all four genes. Changes in gene expression between benign samples and primary lesions were minor and not relevant.
CONCLUSIONS: Four of the examined ABC transporters are likely to play a role in the MDR of ovarian carcinoma. Gene expression of these transporters seems only up regulated through chemotherapy. The thesis that MDR in ovarian cancer is acquired through therapy itself and not present ab initio is supported by these findings.
Ability to cross-present exogenous antigens in the human leukocyte antigen class I pathway is key to the antigen presenting function of mature tumor cell-loaded dendritic cells (DC). Conditions of DC maturation have been shown to be important for DCs ability to produce proinflammatory cytokines and induce T cell effector functions. However, it remains unknown if the different pathways of maturation are associated with modulation of the ability of mature DCs to cross-present tumor antigens (TA). Here, we compare DC matured with 3 clinically relevant cytokine combinations including interleukin (IL)-1 beta, tumor necrosis factor-alpha, IL-6 (termed DC-0), DC-0 cells incubated with prostaglandin-2 (termed DC-0+prostaglandin-2), or DC treated with interferon-gamma, interferon-alpha, tumor necrosis factor-alpha, Poly I:C, and IL1-beta (termed DC-1). We found that these DC vary in their ability to cross-present TA to cytotoxic T lymphocytes (CTL), with the DC-1 cytokine combination being significantly more effective than the other 2. TA cross presentation and CTL priming were strongly correlated with level of expression of the antigen processing machinery components, TAP1 and TAP2, indicating that these components could be used as biomarkers to standardize DC preparations for optimal function. However, the up-regulation of TAP1/TAP2 was not sufficient to explain the enhanced cross-presentation ability of DC-1 cells, as the use of IFN-gamma alone to up-regulate TAP1/TAP2 did not generate DC as effective at cross-presentation as the full DC-1 maturation cytokine combination. These data indicate for the first time that the pathways of DC maturation modulate antigen processing machinery component expression to different extents and that differently matured DC vary in the ability to cross-present TA to human leukocyte antigen class I-restricted CTL.
BACKGROUND: MHC class I expression by cancer cells enables specific antigen recognition by the immune system and protection of the host. However, in some cancer types MHC class I expression is associated with an unfavorable outcome. We explored the basis of MHC class I association with unfavorable prognostic marker expression in the case of medulloblastoma.
METHODS: We investigated expression of four essential components of MHC class I (heavy chain, beta2m, TAP1 and TAP2) in 10 medulloblastoma mRNA samples, a tissue microarray containing 139 medulloblastoma tissues and 3 medulloblastoma cell lines. Further, in medulloblastoma cell lines we evaluated the effects of HLA class I engagement on activation of ERK1/2 and migration in vitro.
RESULTS: The majority of specimens displayed undetectable or low levels of the heavy chains. Medulloblastomas expressing high levels of HLA class I displayed significantly higher levels of anaplasia and c-myc expression, markers of poor prognosis. Binding of beta2m or a specific antibody to open forms of HLA class I promoted phosphorylation of ERK1/2 in medulloblastoma cell line with high levels, but not in the cell line with low levels of HLA heavy chain. This treatment also promoted ERK1/2 activation dependent migration of medulloblastoma cells.
CONCLUSION: MHC class I expression in medulloblastoma is associated with anaplasia and c-myc expression, markers of poor prognosis. Peptide- and/or beta2m-free forms of MHC class I may contribute to a more malignant phenotype of medulloblastoma by modulating activation of signaling molecules such as ERK1/2 that stimulates cell mobility.
Liu Q, Hao C, Su P, Shi JDown-regulation of HLA class I antigen-processing machinery components in esophageal squamous cell carcinomas: association with disease progression.
Scand J Gastroenterol. 2009; 44(8):960-9 [PubMed
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OBJECTIVE: Lack of human leukocyte antigen (HLA) presentation has been proposed to contribute to the immune evasion of cancer cells in some cancers including esophageal cancer. The aim of this study was to examine the expression of HLA class I antigen and the antigen-processing machinery (APM) components in esophageal squamous cell carcinoma (ESCC) lesions and to assess their association with histopathological characteristics.
MATERIAL AND METHODS: A total of 143 formalin-fixed, paraffin-embedded ESCC lesions collected in two hospitals in Shandong Province of China were studied. The expression levels were determined by immunohistochemistry.
RESULTS: TAP1, TAP2, LMP2, LMP7, beta2m, and HLA class I antigen were lost or down-regulated in 30.8%, 35.0%, 45.0%, 48.0%, 56.0%, and 60.8% of the ESCC lesions tested, respectively. The loss of or down-regulated expressions of HLA class I, beta2m, TAP1, LMP2, and LMP7 in tumor lesions were all significantly correlated to tumor grade and lymph node status. Expression of HLA class I antigens was strongly correlated to the expression levels of beta2m, TAP1, TAP2, LMP2, and LMP7, suggesting APM component defects as a mechanism underlying HLA class I antigen down-regulation in ESCC lesions. Expression of APM components and HLA class I antigens was significantly associated with the extent of intratumoral T-cell infiltration.
CONCLUSIONS: Our results indicate that lack or reduction of HLA class I antigens and expression of APM components in ESCC may render some tumor cells to escape the immunosurveillance mediated by CD8(+) T cells and contribute to the clinical course of ESCC.
de Miranda NF, Nielsen M, Pereira D, et al.MUTYH-associated polyposis carcinomas frequently lose HLA class I expression - a common event amongst DNA-repair-deficient colorectal cancers.
J Pathol. 2009; 219(1):69-76 [PubMed
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Human leukocyte antigen (HLA) class I expression defects frequently occur in colorectal cancers bearing mismatch repair (MMR) deficiencies and are interpreted as immune evasion mechanisms to avoid cancer cell recognition and elimination by the immune system. MMR-deficient tumours are thought to be more prone to lose HLA class I expression, due to their frequent generation of aberrant peptides which can stimulate a cytotoxic T-cell-mediated response. MUTYH-associated polyposis (MAP) is a colorectal cancer syndrome caused by defects in the MUTYH DNA repair enzyme. Impairment of MUTYH activity could lead to a surplus of mutated peptides which would be presented to cytotoxic T-cells through the HLA class I molecules. We have studied the frequency of HLA class I expression defects in MAP carcinomas and have compared it to those observed in MMR-deficient and -proficient colorectal tumours. Immunohistochemical detection of the expression of HLA class I, beta2-microglobulin (beta2m), and antigen-processing machinery molecules was performed in 37 primary MAP carcinomas and nine metastases resected from 29 MAP patients. Furthermore, we sequenced the beta2m, TAP1, and TAP2 genes. Defects in HLA class I expression were detected in 65% of primary MAP carcinomas, affecting 72% of patients. HLA class I expression abnormalities were often concomitant with beta2m expression loss and mutations in the beta2m gene. Loss of HLA class I expression is thus a frequent event in MAP carcinomas, similarly to MMR-deficient colorectal tumours. The extensive mutagenic background of these tumours most likely triggers a strong selective pressure, exerted by the immune system on the tumour, which favours the outgrowth of tumour cell clones with an immune evasive phenotype. Our data provide additional evidence for a link between DNA repair deficiencies and altered HLA class I phenotypes in colorectal cancer.