Gene Summary

Gene:NPRL2; NPR2 like, GATOR1 complex subunit
Aliases: NPR2, NPR2L, TUSC4, FFEVF2
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:GATOR complex protein NPRL2
Source:NCBIAccessed: 01 September, 2019


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 01 September 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 01 September, 2019 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).

Latest Publications: NPRL2 (cancer-related)

Chen X, Chen Z, Zheng B, Tang W
Targeting NPRL2 to enhance the efficacy of Olaparib in castration-resistant prostate cancer.
Biochem Biophys Res Commun. 2019; 508(2):620-625 [PubMed] Related Publications
Castration-resistant prostate cancer (CRPC) lacks effective treatment, and studies have shown that PARPi inhibitors, such as Olaparib, are somewhat effective; however, the efficacy of Olaparib in CRPC still needs to be further improved. Nitrogen permease regulator-like 2 (NPRL2) is reported to be a tumor suppressor candidate gene and is closely related to the DNA repair pathway, which can affect the sensitivity of many chemotherapeutic drugs. However, there is no research on whether NPRL2 is associated with sensitivity to Olaparib. Hence, in the present study, we examined the NPRL2 expression levels in several PCa cell lines (LNCaP, PC3, and enzalutamide-resistant LNCaP, named LNPER) by Western blot. In addition, we investigated the role of NPRL2 expression and silencing in cell proliferation and in the regulation of ataxia telangiectasia mutated (ATM), which can mediate DNA repair and sensitivity to Olaparib. Furthermore, we performed in vitro and in vivo experiments to determine the mechanism of action of NPRL2 in adjusting Olaparib sensitivity. Our findings demonstrated that the NPRL2 expression level was upregulated in PCa cells, especially CRPC cells. NPRL2 overexpression promoted growth and resistance to Olaparib, and NPRL2 silencing inhibited proliferation, enhanced sensitivity to Olaparib, and increased CRRL2 expression in PCa cells. In addition, the Olaparib-induced growth delay in NPRL2-silenced PC3 tumors in mice correlated with ATM signaling downregulation, an apoptosis increase and migration/invasion suppression. Our results indicate that NPRL2 silencing enhances sensitivity to Olaparib treatment in CRPC and that NPRL2 may serve as a potential therapeutic target and predict resistance to Olaparib in CRPC.

Chen Z, Jiang Q, Zhu P, et al.
NPRL2 enhances autophagy and the resistance to Everolimus in castration-resistant prostate cancer.
Prostate. 2019; 79(1):44-53 [PubMed] Related Publications
BACKGROUND: Nitrogen permease regulator-like 2 (NPRL2) is reported to be a tumor suppressor candidate gene and involved in the mTOR signaling and drug resistance in several cancers. However, the role of NPRL2 in regulating the resistance to Everolimus (EVS), an inhibitor of the mTOR, in castration-resistant prostate cancer (CRPC) is still unclear. Therefore, in present study, we evaluated the role of NPRL2 and its potential resistance to EVS in CRPC.
METHODS: NPRL2 expression levels in prostate tissues, including benign prostate hyperplasia (BPH) tissues, primary prostate cancer (PCa) tissues, CRPC tissues, and several PCa cell lines (LNCaP, PC3, and enzalutamide-resistant LNCaP, named LNPER) were be evaluated by immunohistochemistry, RT-PCR, and Western blot. Furthermore, we employed the loss or gain function of NPRL2 to determine the role of NPRL2 in regulating the proliferation, sensitivity to EVS, the mTOR signaling, autophagy in CRPC. Lastly, relationship between NPRL2 expression level and the efficacy of EVS were evaluated in mice tumor xenograft models.
RESULTS: NPRL2 expression level is upregulated in PCa, particularly in the CRPC. NPRL2 over-expression promoted the proliferation, resistance to EVS, and NPRL2 silencing inhibited proliferation, enhanced sensitivity to EVS in PC3 and LNPER cells. Moreover, NPRL2-silencing increased the activity of mTOR signaling, and the autophagy attenuation induced by NPRL2-silencing in EVS-treated CRPC cells was associated with the increase of apoptosis. In addition, the growth prevention of NPRL2-silencing LNPER tumors in mice induced by EVS-treatment was associated with the autophagy attenuation and apoptosis increase.
CONCLUSIONS: NPRL2 may act as a pro-growth factor in PCa. The high levels of NPRL2 expression in CRPC promote resistance to EVS by enhancing autophagy. NPRL2 may be a new therapeutic target for intervention of CRPC and a biomarker for predicting resistance to EVS in CRPC.

Chen J, Ou Y, Yang Y, et al.
KLHL22 activates amino-acid-dependent mTORC1 signalling to promote tumorigenesis and ageing.
Nature. 2018; 557(7706):585-589 [PubMed] Related Publications
The mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of cell growth that responds to a diverse set of environmental cues, including amino acids

Wang X, Wang H, Liu W, et al.
High level of C-type natriuretic peptide induced by hyperandrogen-mediated anovulation in polycystic ovary syndrome mice.
Clin Sci (Lond). 2018; 132(7):759-776 [PubMed] Related Publications
Polycystic ovary syndrome (PCOS), which is characterized by hyperandrogenism, is a complex endocrinopathy that affects the fertility of 9-18% of reproductive-aged women. However, the exact mechanism of PCOS, especially hyperandrogen-induced anovulation, is largely unknown to date. Physiologically, the natriuretic peptide type C/natriuretic peptide receptor 2 (CNP/NPR2) system is essential for sustaining oocyte meiotic arrest until the preovulatory luteinizing hormone (LH) surge. We therefore hypothesized that the CNP/NPR2 system is also involved in PCOS and contributes to arresting oocyte meiosis and ovulation. Here, based on a dehydroepiandrosterone (DHEA)-induced PCOS-like mouse model, persistent high levels of CNP/NPR2 were detected in anovulation ovaries. Meanwhile, oocytes arrested at the germinal vesicle stage correlated with persistent high levels of androgen and estrogen. We further showed that ovulation failure in these mice could be a result of elevated

Liu S, Liu B
Overexpression of Nitrogen Permease Regulator Like-2 (NPRL2) Enhances Sensitivity to Irinotecan (CPT-11) in Colon Cancer Cells by Activating the DNA Damage Checkpoint Pathway.
Med Sci Monit. 2018; 24:1424-1433 [PubMed] Free Access to Full Article Related Publications
BACKGROUND Colorectal cancer (CRC) is the third most common cancer worldwide, making it is a serious threat to human health. It is imperative to develop new therapeutics to improve the CRC treatment efficiency. The aim of this study was to investigate the role of NPRL2 in improving sensitivity to CPT-11 in colon cancer cells. MATERIAL AND METHODS NPRL2 overexpression was established by transfecting the recombinant lentivirus-encoding NPRL2 gene into HCT116 colon cancer cells. Cell proliferation was identified using Cell Counting Kit-8 (CCK8) assay. Cell cycle and apoptosis were examined by flow cytometry. An immunofluorescence staining assay was conducted to examine the expression of γ-H2AX. Wound-healing and Transwell assays were utilized to show cell migration and invasion capability. The expression of apoptosis-related proteins (cleaved caspase-3, caspase-9, cleaved PARP, BAX, and Bcl-2), invasion-related proteins (MMP2, MMP9, p-PI3K, and p-AKT), and DNA damage checkpoint pathway proteins (p-ATM, p-Chk2, Cdc25C, Cdc2, and Cyclin B1) were quantified by Western blotting. RESULTS A CCK8 assay revealed that the overexpression of NPRL2 improved the sensitivity of CPT-11 in HCT116 cells (P<0.05). Functionally, NPRL2 overexpression elevated the sensitivity of CPT-11 by preventing colon cancer cell proliferation, cell movement, and invasion, and promoting cell apoptosis and G2/M cell cycle arrest. Mechanistically, NPRL2 overexpression enhanced CPT-11 sensitivity by activating the DNA damage checkpoint pathway. CONCLUSIONS NPRL2 overexpression enhances sensitivity to CPT-11 treatment in colon cancer cells, and it may serve as a molecular therapeutic agent to treat patients with CRC.

Chen Z, Luo S, Chen Y, et al.
High expression of NPRL2 is linked to poor prognosis in patients with prostate cancer.
Hum Pathol. 2018; 76:141-148 [PubMed] Related Publications
As a tumor suppressor candidate gene, NPRL2 has anticancer effects against several cancers, but its potential role in prostate cancer (PCa) has not been reported. The present study aimed to explore the expression of NPRL2 in PCa and its potential clinical significance. Our results showed that expression of NPRL2 in PCa tissues was significantly higher than that in non-PCa tissues (P < .001). High NPRL2 expression in PCa tissue was significantly correlated with a high Gleason grade group (P < .001), high pT stage (P < .001), and lymph node metastasis (P = .003). The overall survival of PCa patients with negative to weak NPRL2 expression was significantly higher than that of patients with moderate to strong positive NPRL2 expression. Furthermore, in vitro, we found that the up-regulated NPRL2 level in LNCaP and PC3 cells, and forced reexpression of NPRL2 significant promoted the growth of those cells and vice versa. Contrary to existing reports, our results interestingly showed, for the first time, that the expression level of NPRL2 was significantly up-regulated in PCa and its high expression was correlated with poor prognosis, suggesting its pivotal role in the progression of PCa. NPRL2 may serve as a potential prognostic biomarker for PCa patients.

Kordiak J, Czarnecka KH, Pastuszak-Lewandoska D, et al.
Small suitability of the DLEC1, MLH1 and TUSC4 mRNA expression analysis as potential prognostic or differentiating markers for NSCLC patients in the Polish population.
J Genet. 2017; 96(2):227-234 [PubMed] Related Publications
According to the latest data, lung cancer is one of the most common cancer worldwide, men contributing nearly 21.2% and women 8.6% of all diagnosed cancers. Late detection of tumour drastically reduces the chance for a cure. Thus, it is important to search for candidate biomarkers for screening of early stage nonsmall cell lung carcinoma (NSCLC). Tumour suppressor genes, DLEC1, TUSC4 and MLH1, localized on 3p21 are recognized to play a role in NSCLC carcinogenesis. The aim of this study was to assess the relationship between the DLEC1, TUSC4 and MLH1 mRNA expression, and clinical features of NSCLC patients, tobacco addiction, and tumour histopathological characteristics. The DLEC1, TUSC4 and MLH1 expression was analysed in lung tumour tissue samples obtained from 69 patients diagnosed with NSCLC: squamous cell carcinoma (n = 34), adenocarcinoma (n = 24), large cell carcinoma (n = 5), carcinoma adenosquamosum (n = 5). A decreased gene expression (RQ < 0.7) was observed for DLEC1 in 60.9% of tumour samples, for MLH1 in 50.7% and for TUSC4 in 26% of NSCLC samples. DLEC1 was decreased in more aggressive subtypes: large cell carcinoma and adenocarcinoma-squamous cell carcinoma. The simultaneous downregulation of two of the studied genes, DLEC1 andMLH1,was observed in 30.4% of NSCLCsamples, highlighting the importance of these two genes in lung carcinogenesis. We found no correlation between the DLEC1, TUSC4 and MLH1 gene expression and NSCLC patient characteristics (gender, age and smoking) or cancer histopathology. No significant differences in the gene expression among NSCLC subtypes indicate the weakness of DLEC1, TUSC4 and MLH1 expression analysis as potential differentiating markers of NSCLC subtypes in the Polish population.

Zeng Y, Shi XB, Yuan ZY, et al.
Biological characteristics of renal cancer cells after CTP-mediated cancer suppressor gene NPRL2 protein treatment.
Biol Chem. 2016; 397(11):1163-1171 [PubMed] Related Publications
Nitrogen permease regulator like-2 (NPRL2) has been proved to be a useful suppressor gene in treating many cancers containing renal cancer based on experiments. Transgenic technology which transfect exogenous NPRL2 gene into cancer cell was used in these experiments. However, this technology has defects, such as gene mutation and loss. Cytoplasmic transduction peptide (CTP) can be used to avoid these defects because it can directly mediate proteins to penetrate cell membrane and specifically locate in cytoplasm. In this article, CTP was used to directly mediate NPRL2 protein into the renal cancer cell line 786-O, then cell proliferation was detected by the CCK-8 method, cell cycle and apoptosis were detected by flow cytometry, cell invasion and migration ability were detected by the Transwell assay. Bcl-xl, Cyt-c and caspase-3 were detected by real-time fluorescent quantitative PCR and Western blot for the analysis of the related mechanism. The result showed that CTP successfully mediated NPRL2 protein into renal cancer cells and the growth of cells was significantly inhibited. The mechanism may be NPRL2 down-regulating the expression of Bcl-xl which can up-regulate Cyt-c and further activate caspase-3, and then a cascade reaction is caused for cell apoptosis on the classic mitochondrial apoptosis pathway.

Huang N, Cheng S, Mi X, et al.
Downregulation of nitrogen permease regulator like-2 activates PDK1-AKT1 and contributes to the malignant growth of glioma cells.
Mol Carcinog. 2016; 55(11):1613-1626 [PubMed] Related Publications
Nitrogen permease regulator like-2(NPRL2) is a candidate tumor suppressor gene(TSG) located on chromosome 3p21.3 and deletions frequently occur in this region, leading to canceration. Recently, molecular pathologic researches have provided valuable insights into the downregulation of NPRL2 in carcinogenesis in some types of cancers. However, very little is known about genetic changes of NPRL2 involved in glioma. Here, for the first time, we aimed to understand the expression levels, functions and mechanisms of NPRL2 for progression of glioma. We clearly demonstrated that NPRL2 expression was decreased in glioma and was negatively correlated with the histologic grade. The upregulation of NPRL2 expression in glioma cells inhibited proliferation by inducing G0/G1 cell cycle arrest in vitro and suppressed the growth of xenotransplanted tumors. In contrast, siRNA-mediated knockdown of NPRL2 promoted glioma growth. The anti-cancer effects of NPRL2 were involved in dephosphorylation of PDK1

Pastuszak-Lewandoska D, Kordiak J, Migdalska-Sęk M, et al.
Quantitative analysis of mRNA expression levels and DNA methylation profiles of three neighboring genes: FUS1, NPRL2/G21 and RASSF1A in non-small cell lung cancer patients.
Respir Res. 2015; 16:76 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Tumor suppressor gene (TSG) inactivation plays a crucial role in carcinogenesis. FUS1, NPRL2/G21 and RASSF1A are TSGs from LUCA region at 3p21.3, a critical chromosomal region in lung cancer development. The aim of the study was to analyze and compare the expression levels of these 3 TSGs in NSCLC, as well as in macroscopically unchanged lung tissue surrounding the primary lesion, and to look for the possible epigenetic mechanism of TSG inactivation via gene promoter methylation.
METHODS: Expression levels of 3 TSGs and 2 DNA methyltransferases, DNMT1 and DNMT3B, were assessed using real-time PCR method (qPCR) in 59 primary non-small cell lung tumors and the matched macroscopically unchanged lung tissue samples. Promoter methylation status of TSGs was analyzed using methylation-specific PCRs (MSP method) and Methylation Index (MI) value was calculated for each gene.
RESULTS: The expression of all three TSGs were significantly different between NSCLC subtypes: RASSF1A and FUS1 expression levels were significantly lower in squamous cell carcinoma (SCC), and NPRL2/G21 in adenocarcinoma (AC). RASSF1A showed significantly lower expression in tumors vs macroscopically unchanged lung tissues. Methylation frequency was 38-76%, depending on the gene. The highest MI value was found for RASSF1A (52%) and the lowest for NPRL2/G21 (5%). The simultaneous decreased expression and methylation of at least one RASSF1A allele was observed in 71% tumor samples. Inverse correlation between gene expression and promoter methylation was found for FUS1 (rs = -0.41) in SCC subtype. Expression levels of DNMTs were significantly increased in 75-92% NSCLCs and were significantly higher in tumors than in normal lung tissue. However, no correlation between mRNA expression levels of DNMTs and DNA methylation status of the studied TSGs was found.
CONCLUSIONS: The results indicate the potential role of the studied TSGs in the differentiation of NSCLC histopathological subtypes. The significant differences in RASSF1A expression levels between NSCLC and macroscopically unchanged lung tissue highlight its possible diagnostic role in lung cancer in situ recognition. High percentage of lung tumor samples with simultaneous RASSF1A decreased expression and gene promoter methylation indicates its epigenetic silencing. However, DNMT overexpression doesn't seem to be a critical determinate of its promoter hypermethylation.

Liu AY, Liu MN, Pei FH, et al.
Functional characterization of the nitrogen permease regulator-like-2 candidate tumor suppressor gene in colorectal cancer cell lines.
Mol Med Rep. 2015; 12(3):3487-3493 [PubMed] Free Access to Full Article Related Publications
The nitrogen permease regulator‑like‑2 (NPRL2) gene is a candidate tumor suppressor gene, which has been identified in the 3p21.3 human chromosome region. Decreased expression levels of NPRL2 have been observed in colorectal cancer (CRC) tissues, however, the function of NPRL2 in CRC progression remains to be fully elucidated. The present study investigated the biological characteristics of the HCT116 and HT29 CRC cell lines overexpressing exogenous NPRL2. NPRL2 recombinant lentiviral vectors were also constructed and transfected in the present study. Cell growth was determined using a Cell Counting Kit‑8 assay and a colony formation assay. The cell cycle and rate of apoptosis were assessed using flow cytometric analysis. Transwell assays were used to evaluate cell invasion. The protein expression of phosphorylated (p)‑AKT and caspase 3, B‑cell lymphoma 2 (Bcl2) and Bcl‑2‑associated X protein apoptosis‑associated genes, were detected using western blotting. The results revealed that NPRL2 overexpression inhibited cell growth, induced cell cycle G1 phase arrest, promoted apoptosis and inhibited invasion in the two human CRC cell lines. Furthermore, the protein expression levels of p‑AKT and Bcl2 were significantly reduced in the NPRL2‑transfected HCT116 and HT29 cells, compared with the mock‑transfected group and control group, while the protein expression of caspase‑3 was increased. Therefore, NPRL2 acted as a functional tumor suppressor in the CRC cell lines.

Peng Y, Dai H, Wang E, et al.
TUSC4 functions as a tumor suppressor by regulating BRCA1 stability.
Cancer Res. 2015; 75(2):378-86 [PubMed] Free Access to Full Article Related Publications
BRCA1 expression is lost frequently in breast cancers in which it promotes malignant development. In the present study, we performed a global expression analysis of breast cancer cells in which the tumor-suppressor candidate gene TUSC4 was silenced to gain insights into its function. TUSC4 silencing affected genes involved in cell cycle and cell death, which have broad reaching influence on cancer development. Most importantly, we found a cluster pattern of gene-expression profiles in TUSC4-silenced cells that defined a homologous recombination (HR) repair defect signature. Mechanistic investigations indicated that TUSC4 protein could physically interact with the E3 ligase Herc2, which prevents BRCA1 degradation through the ubiquitination pathway. TUSC4 silencing enhanced BRCA1 polyubiquitination, leading to its degradation and a marked reduction in HR repair efficiency. Notably, ectopic expression of TUSC4 suppressed the proliferation, invasion, and colony formation of breast cancer cells in vitro and tumorigenesis in vivo. Furthermore, TUSC4 silencing was sufficient to transform normal mammary epithelial cells and to enhance sensitivity to PARP inhibitors. Our results provide a set of genetic and biologic proofs that TUSC4 functions as a bona fide tumor suppressor by regulating the protein stability and function of BRCA1 in breast cancer.

Tang Y, Jiang L, Tang W
Decreased expression of NPRL2 in renal cancer cells is associated with unfavourable pathological, proliferation and apoptotic features.
Pathol Oncol Res. 2014; 20(4):829-37 [PubMed] Related Publications
The tumor suppressor gene nitrogen permease regulator-like 2(NPRL2) NPRL2 expressed obviously in many normal human tissues, but reduced in expression in many human tumors significantly. In this study, we detected the expression of NPRL2 in 78 clear cell renal cell carcinoma (ccRCC) by immunohistochemistry and correlated it with clinicopathological parameters. Meanwhile, the function of NPRL2 in human ccRCC was further explored after transfected recombinant expressing plasmids pEGFP-N1-NPRL2 into human renal cancer 786-0 cells. NPRL2 protein showed high expression in 67 of 78 cases of adjacent normal tissues (85.9 %), which was significantly higher than that in ccRCC tissues (23/78, 29.5 %). Clinic pathological analysis showed that NPRL2 expression was significantly correlated with histological grade (P = 0.044), TNM stage (P = 0.025) and lymph node metastasis (P = 0.028). MTT assay demonstrated that NPRL2 could obviously inhibit renal cancer cell proliferation. Flow cytometric analysis revealed that NPRL2 could induce renal cancer cells apoptosis and arrest the cell cycle in G0/G1 phase. In conclusion, NPRL2 is closely correlated to unfavourable pathological, proliferation and apoptotic features in ccRCC.

Liu AY, Liu DG, Du YJ, et al.
Relationship between tumor and peripheral blood NPRL2 mRNA levels in patients with colorectal adenoma and colorectal cancer.
Cancer Biol Ther. 2014; 15(5):489-95 [PubMed] Free Access to Full Article Related Publications
NPRL2 is a tumor suppressor gene involved in the progression of human cancer. The present study investigated whether NPRL2 expression correlates with colorectal cancer (CRC) progression. Colorectal tissue and peripheral blood samples were obtained from 62 patients with CRC, 38 patients with colorectal adenomas and 51 normal controls. NPRL2 mRNA levels in tissue samples and blood were measured using quantitative real-time PCR. NPRL2 protein expression was determined by immunohistochemistry. NPRL2 protein expression in CRCs was significantly lower than in the adenomas or normal colorectal tissue. NPRL2 mRNA expression was significantly decreased in adenomas compared with normal controls (P<0.0001) and it was further decreased in colorectal tumors compared with adenomas (P<0.0001). NPRL2 mRNA levels expression correlated with tumor stage. In addition, NPRL2 mRNA levels in the blood correlated with the levels detected in tumors. Furthermore, receiver operating characteristic (ROC) analysis showed that NPRL2 expression in blood could distinguish colorectal adenomas and CRCs from normal controls. NPRL2 mRNA expression in CRC tumor tissues and peripheral blood correlated with colorectal tumor progression. Based on our findings, we can conclude that NPRL2 mRNA blood levels could be a potentially useful marker for the detection of early stage adenomas and CRCs.

Gao Y, Wang J, Fan G
NPRL2 is an independent prognostic factor of osteosarcoma.
Cancer Biomark. 2012-2013; 12(1):31-6 [PubMed] Related Publications
NPRL2 is a tumor suppressor gene whose inactivation contributes to tumor development. However, NPRL2 expression in osteosarcoma remains unclear. This study aimed to assess NPRL2 expression in osteosarcoma and analyze its potential as a prognostic factor. NPRL2 expression in 48 cases of osteosarcoma and 40 cases of osteochondroma tumors was examined by immunohistochemistry. NPRL2 expression in 20 osteosarcoma and 20 osteochondroma specimens were detected by Real-time PCR and Western blot analysis. We found that 18 cases (37.5%) of osteosarcoma and 27 cases (67.5%) of osteochondroma showed positive NPRL2 expression. Real-Time PCR and Western blot analysis showed that NRPL2 expression was lower in osteosarcoma than in osteochondroma (p< 0.05). The positive rate of NPRL2 expression was 71.4% (10/14), 25% (4/16) and 16.7% (3/18) in stage I, II and III of osteosarcoma, respectively. The positive rate of NPRL2 was 19% (4/21) and 48.1% (13/27) for low grade and high grade of osteosarcoma, respectively, with significant difference (p< 0.05). Cox multivariate analysis showed that the value of NPRL2 for predicting the overall survival of osteosarcoma patients. Despite the small size of the samples, our results suggest that NPRL2 expression is negatively related with the survival of osteosarcoma patients, indicating its value as a prognosis factor of osteosarcoma.

Yogurtcu B, Hatemi I, Aydin I, Buyru N
NPRL2 gene expression in the progression of colon tumors.
Genet Mol Res. 2012; 11(4):4810-6 [PubMed] Related Publications
Genetic and epigenetic factors affecting DNA methylation and gene expression are known to be involved in the development of colon cancer, but the full range of genetic alterations and many key genes involved in the pathogenesis of colon cancer remain to be identified. NPRL2 is a candidate tumor suppressor gene identified in the human chromosome 3p21.3 region. We evaluated the role of this gene in the pathogenesis of colorectal cancer by investigating NPRL2 mRNA expression in 55 matched normal and tumor colon tissue samples using quantitative RT-PCR analysis. There was significantly decreased NPRL2 expression in 45% of the patients. Lower NPRL2 expression was observed significantly more frequently in poorly differentiated tumor samples than in highly or moderately differentiated tumors. We conclude that expression of NPRL2 contributes to progression of colon cancer.

Thompson IR, Chand AN, King PJ, et al.
Expression of guanylyl cyclase-B (GC-B/NPR2) receptors in normal human fetal pituitaries and human pituitary adenomas implicates a role for C-type natriuretic peptide.
Endocr Relat Cancer. 2012; 19(4):497-508 [PubMed] Related Publications
C-type natriuretic peptide (CNP/Nppc) is expressed at high levels in the anterior pituitary of rats and mice and activates guanylyl cyclase B receptors (GC-B/Npr2) to regulate hormone secretion. Mutations in NPR2/Npr2 can cause achondroplasia, GH deficiency, and female infertility, yet the normal expression profile within the anterior pituitary remains to be established in humans. The current study examined the expression profile and transcriptional regulation of NPR2 and GC-B protein in normal human fetal pituitaries, normal adult pituitaries, and human pituitary adenomas using RT-PCR and immunohistochemistry. Transcriptional regulation of human NPR2 promoter constructs was characterized in anterior pituitary cell lines of gonadotroph, somatolactotroph, and corticotroph origin. NPR2 was detected in all human fetal and adult pituitary samples regardless of age or sex, as well as in all adenoma samples examined regardless of tumor origin. GC-B immunoreactivity was variable in normal pituitary, gonadotrophinomas, and somatotrophinomas. Maximal transcriptional regulation of the NPR2 promoter mapped to a region within -214 bp upstream of the start site in all anterior pituitary cell lines examined. Electrophoretic mobility shift assays revealed that this region contains Sp1/Sp3 response elements. These data are the first to show NPR2 expression in normal human fetal and adult pituitaries and adenomatous pituitary tissue and suggest a role for these receptors in both pituitary development and oncogenesis, introducing a new target to manipulate these processes in pituitary adenomas.

da Costa Prando E, Cavalli LR, Rainho CA
Evidence of epigenetic regulation of the tumor suppressor gene cluster flanking RASSF1 in breast cancer cell lines.
Epigenetics. 2011; 6(12):1413-24 [PubMed] Free Access to Full Article Related Publications
Epigenetic mechanisms are frequently deregulated in cancer cells and can lead to the silencing of genes with tumor suppressor activities. The isoform A of the Ras-association domain family member 1 (RASSF1A) gene is one of the most frequently silenced transcripts in human tumors, however, few studies have simultaneously investigated epigenetic abnormalities associated with the 3p21.3 tumor suppressor gene cluster flanking RASSF1 (i.e., SEMA3B, HYAL3, HYAL2, HYAL1, TUSC2, RASSF1, ZMYND10, NPRL2, TMEM115, and CACNA2D2). This study aimed to investigate the role of epigenetic changes to these genes in seventeen breast cancer cell lines and in three non-tumorigenic epithelial breast cell lines (184A1, 184B5, and MCF 10A) and to evaluate the effect on gene expression of treatment with the demethylating agent 5-Aza-2'-deoxycytidine and/or Trichostatin A (TSA), a histone deacetylase inhibitor. We report that, although the RASSF1A isoform was determined to be epigenetically silenced in 15 of the 17 breast cancer cell lines, all the cell lines expressed the RASSF1C isoform. Five breast cancer cell lines overexpressed RASSF1C, when compared to the normal epithelial cell line 184A1. Furthermore, the genes HYAL1 and CACNA2D2 were significantly overexpressed after the treatments. After the combinated treatment, RASSF1A re-expression was accompanied by an increase in expression levels of the flanking genes. The Spearman's correlation coefficient indicated a positive co-regulation of the following gene pairs: RASSF1 and TUSC2 (r=0.64, p=0.002), RASSF1 and ZMYND10 (r=0.58, p=0.07), RASSF1 and NPRL2 (r=0.48, p=0.03), ZMYND10 and NPRL2 (r=0.71; p=0,0004), and NPRL2 and TMEM115 (r=0.66, p=0.001). Interestingly, the genes TUSC2, NPRL2 and TMEM115 were found to be unmethylated in each of the untreated cell lines. Chromatin immunoprecipitation using antibodies against the acetylated and trimethylated lysine 9 of histone H3 demonstrated low levels of histone methylation in these genes, which are located closest to RASSF1. These results provide evidence that epigenetic repression is involved in the down-regulation of multiple genes at 3p21.3 in breast cancer cells.

Dai Y, Wang J, Xia J, et al.
Genome-wide transcriptional profiling analysis of all trans retinoic acid-treated tongue carcinoma SCC-9 cells.
J Surg Oncol. 2011; 104(7):830-5 [PubMed] Related Publications
BACKGROUND: All trans retinoic acid (ATRA) is used as standard of care in promyelocytic leukemia. Not much is known about the gene expression profile in ATRA-treated tongue cancer cells. We performed a genome-wide transcriptional profiling of ATRA-treated tongue cancer cells to understand the pathways that mediate ATRA action in tongue cancer.
METHODS: We measured the effects of ATRA on the proliferation of SCC-9 human tongue carcinoma cells. The differential gene expression profile was measured by microarray analysis of untreated and ATRA-treated cells and expression of key genes was validated by real-time RT-PCR.
RESULTS: ATRA treatment (24 and 48 hr) significantly inhibited SCC-9 cell proliferation in a dose-dependent manner. SCC-9 cells treated for 48 hr with ATRA showed upregulation of 276 genes, including ANGPTL4, GDF15, ICAM1 and TUSC4, and downregulation of 43 genes, including CXCL10. Validation by real-time PCR showed a significant upregulation of intracellular adhesion molecule 1 (ICAM1) and downregulation of CXCL10 and IL32.
CONCLUSIONS: ATRA had an anti-tumor effect in tongue cancer cells. This effect is likely mediated via upregulation of ICAM1 and downregulation of CXCL10 and IL32.

Jayachandran G, Ueda K, Wang B, et al.
NPRL2 sensitizes human non-small cell lung cancer (NSCLC) cells to cisplatin treatment by regulating key components in the DNA repair pathway.
PLoS One. 2010; 5(8):e11994 [PubMed] Free Access to Full Article Related Publications
NPRL2, one of the tumor suppressor genes residing in a 120-kb homozygous deletion region of human chromosome band 3p21.3, has a high degree of amino acid sequence homology with the nitrogen permease regulator 2 (NPR2) yeast gene, and mutations of NPRL2 in yeast cells are associated with resistance to cisplatin-mediated cell killing. Previously, we showed that restoration of NPRL2 in NPRL2-negative and cisplatin-resistant cells resensitize lung cancer cells to cisplatin treatment in vitro and in vivo. In this study, we show that sensitization of non-small cell lung cancer (NSCLC) cells to cisplatin by NPRL2 is accomplished through the regulation of key components in the DNA-damage checkpoint pathway. NPRL2 can phosphorylate ataxia telangiectasia mutated (ATM) kinase activated by cisplatin and promote downstream gamma-H2AX formation in vitro and in vivo, which occurs during apoptosis concurrently with the initial appearance of high-molecular-weight DNA fragments. Moreover, this combination treatment results in higher Chk1 and Chk2 kinase activity than does treatment with cisplatin alone and can activate Chk2 in pleural metastases tumor xenograft in mice. Activated Chk1 and Chk2 increase the expression of cell cycle checkpoint proteins, including Cdc25A and Cdc25C, leading to higher levels of G2/M arrest in tumor cells treated with NPRL2 and cisplatin than in tumor cells treated with cisplatin only. Our results therefore suggest that ectopic expression of NPRL2 activates the DNA damage checkpoint pathway in cisplatin-resistant and NPRL2-negative cells; hence, the combination of NPRL2 and cisplatin can resensitize cisplatin nonresponders to cisplatin treatment through the activation of the DNA damage checkpoint pathway, leading to cell arrest in the G2/M phase and induction of apoptosis. The direct implication of this study is that combination treatment with NPRL2 and cisplatin may overcome cisplatin resistance and enhance therapeutic efficacy.

Senchenko VN, Anedchenko EA, Kondratieva TT, et al.
Simultaneous down-regulation of tumor suppressor genes RBSP3/CTDSPL, NPRL2/G21 and RASSF1A in primary non-small cell lung cancer.
BMC Cancer. 2010; 10:75 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The short arm of human chromosome 3 is involved in the development of many cancers including lung cancer. Three bona fide lung cancer tumor suppressor genes namely RBSP3 (AP20 region),NPRL2 and RASSF1A (LUCA region) were identified in the 3p21.3 region. We have shown previously that homozygous deletions in AP20 and LUCA sub-regions often occurred in the same tumor (P < 10-6).
METHODS: We estimated the quantity of RBSP3, NPRL2, RASSF1A, GAPDH, RPN1 mRNA and RBSP3 DNA copy number in 59 primary non-small cell lung cancers, including 41 squamous cell and 18 adenocarcinomas by real-time reverse transcription-polymerase chain reaction based on TaqMan technology and relative quantification.
RESULTS: We evaluated the relationship between mRNA level and clinicopathologic characteristics in non-small cell lung cancer. A significant expression decrease (> or =2) was found for all three genes early in tumor development: in 85% of cases for RBSP3; 73% for NPRL2 and 67% for RASSF1A (P < 0.001), more strongly pronounced in squamous cell than in adenocarcinomas. Strong suppression of both, NPRL2 and RBSP3 was seen in 100% of cases already at Stage I of squamous cell carcinomas. Deregulation of RASSF1A correlated with tumor progression of squamous cell (P = 0.196) and adenocarcinomas (P < 0.05). Most likely, genetic and epigenetic mechanisms might be responsible for transcriptional inactivation of RBSP3 in non-small cell lung cancers as promoter methylation of RBSP3 according to NotI microarrays data was detected in 80% of squamous cell and in 38% of adenocarcinomas. With NotI microarrays we tested how often LUCA (NPRL2, RASSF1A) and AP20 (RBSP3) regions were deleted or methylated in the same tumor sample and found that this occured in 39% of all studied samples (P < 0.05).
CONCLUSION: Our data support the hypothesis that these TSG are involved in tumorigenesis of NSCLC. Both genetic and epigenetic mechanisms contribute to down-regulation of these three genes representing two tumor suppressor clusters in 3p21.3. Most importantly expression of RBSP3, NPRL2 and RASSF1A was simultaneously decreased in the same sample of primary NSCLC: in 39% of cases all these three genes showed reduced expression (P < 0.05).

Otani S, Takeda S, Yamada S, et al.
The tumor suppressor NPRL2 in hepatocellular carcinoma plays an important role in progression and can be served as an independent prognostic factor.
J Surg Oncol. 2009; 100(5):358-63 [PubMed] Related Publications
BACKGROUND/AIMS: Hepatocarcinogenesis is a multifactorial, multistep process that involves the activation of oncogenes or the inactivation of tumor suppressor genes throughout the different stages of hepatocellular carcinoma (HCC) progression. NPRL2 is one of the candidate tumor suppressor genes identified on chromosome 3p21.3, a region which frequently contains genetic abnormalities found in the early stages of the development of various human cancers. In the current study, we aimed to evaluate NPRL2 expression in HCC and to explore the prognostic significance of NPRL2.
METHOD: We investigated NPRL2 mRNA expression in 70 HCC specimens, using quantitative real-time reverse transcription polymerase chain reaction analysis, and the correlation between NPRL2 expression and clinicopathologic parameters.
RESULTS: NPRL2 mRNA was found to be expressed equally in both HCC tissues and corresponding non-cancerous liver tissues. However, higher NPRL2 expression correlated significantly with tumor size (P = 0.0062) and serum PIVKA-II levels (P = 0.0002). Univariate and multivariate analyses revealed that higher NPRL2 mRNA expression was an independent prognostic factor for overall survival (risk ratio 0.39; P < 0.0001).
CONCLUSION: Our results suggest that NPRL2 mRNA expression has prognostic significance for the survival of patients with HCC.

Wang F, Grigorieva EV, Li J, et al.
HYAL1 and HYAL2 inhibit tumour growth in vivo but not in vitro.
PLoS One. 2008; 3(8):e3031 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: We identified two 3p21.3 regions (LUCA and AP20) as most frequently affected in lung, breast and other carcinomas and reported their fine physical and gene maps. It is becoming increasingly clear that each of these two regions contains several TSGs. Until now TSGs which were isolated from AP20 and LUCA regions (e.g.G21/NPRL2, RASSF1A, RASSF1C, SEMA3B, SEMA3F, RBSP3) were shown to inhibit tumour cell growth both in vitro and in vivo.
METHODOLOGY/PRINCIPAL FINDINGS: The effect of expression HYAL1 and HYAL2 was studied by colony formation inhibition, growth curve and cell proliferation tests in vitro and tumour growth assay in vivo. Very modest growth inhibition was detected in vitro in U2020 lung and KRC/Y renal carcinoma cell lines. In the in vivo experiment stably transfected KRC/Y cells expressing HYAL1 or HYAL2 were inoculated into SCID mice (10 and 12 mice respectively). Tumours grew in eight mice inoculated with HYAL1. Ectopic HYAL1 was deleted in all of them. HYAL2 was inoculated into 12 mice and only four tumours were obtained. In 3 of them the gene was deleted. In one tumour it was present but not expressed. As expected for tumour suppressor genes HYAL1 and HYAL2 were down-expressed in 15 fresh lung squamous cell carcinomas (100%) and clear cell RCC tumours (60-67%).
CONCLUSIONS/SIGNIFICANCE: The results suggest that the expression of either gene has led to inhibition of tumour growth in vivo without noticeable effect on growth in vitro. HYAL1 and HYAL2 thus differ in this aspect from other tumour suppressors like P53 or RASSF1A that inhibit growth both in vitro and in vivo. Targeting the microenvironment of cancer cells is one of the most promising venues of cancer therapeutics. As major hyaluronidases in human cells, HYAL1 and HYAL2 may control intercellular interactions and microenvironment of tumour cells providing excellent targets for cancer treatment.

Hesson LB, Cooper WN, Latif F
Evaluation of the 3p21.3 tumour-suppressor gene cluster.
Oncogene. 2007; 26(52):7283-301 [PubMed] Related Publications
Deletions of the 3p21.3 region are a frequent and early event in the formation of lung, breast, kidney and other cancers. Intense investigation of allelic losses and the discovery of overlapping homozygous deletions in lung and breast tumour-cell lines have defined a minimal critical 120 kb deletion region containing eight genes and likely to harbor one or more tumour-suppressor genes (TSGs). The candidate genes are HYAL2, FUS1, Ras-associated factor 1 (RASSF1), BLU/ZMYND10, NPR2L, 101F6, PL6 and CACNA2D2. Recent research indicates that several of these genes can suppress the growth of lung and other tumour cells. Furthermore, some genes (RASSF1A and BLU/ZMYND10) are very frequently inactivated by non-classical mechanisms such as promoter hypermethylation resulting in loss of expression. These data indicate that the 120 kb critical deletion region at 3p21.3 may represent a TSG cluster with preferential inactivation of particular genes depending on tumour type. The eight genes within this region and their potential role in cancer will be the focus of this review.

Ueda K, Kawashima H, Ohtani S, et al.
The 3p21.3 tumor suppressor NPRL2 plays an important role in cisplatin-induced resistance in human non-small-cell lung cancer cells.
Cancer Res. 2006; 66(19):9682-90 [PubMed] Related Publications
NPRL2 is one of the novel candidate tumor suppressor genes identified in the human chromosome 3p21.3 region. The NPRL2 has shown potent tumor suppression activity in vitro and in vivo and has been suggested to be involved in DNA mismatch repair, cell cycle checkpoint signaling, and regulation of the apoptotic pathway. In this study, we analyzed the endogenous expression of the NPRL2 protein and the cellular response to cisplatin in 40 non-small-cell lung cancer cell lines and found that expression of NPRL2 was significantly and reciprocally correlated to cisplatin sensitivity, with a Spearman correlation coefficient of -0.677 (P < 0.00001). Exogenously introduced expression of NPRL2 by N-[1-(2,3-dioleoyloxyl)propyl]-NNN-trimethylammoniummethyl sulfate:cholesterol nanoparticle-mediated gene transfer significantly resensitized the response to cisplatin, yielding a 40% greater inhibition of tumor cell viability and resulting in a 2- to 3-fold increase in induction of apoptosis by activation of multiple caspases in NPRL2-transfected cells compared with untransfected cells at an equal dose of cisplatin. Furthermore, a systemic treatment with a combination of NPRL2 nanoparticles and cisplatin in a human H322 lung cancer orthotopic mouse model significantly enhanced the therapeutic efficacy of cisplatin and overcame cisplatin-induced resistance (P < 0.005). These findings implicate the potential of NPRL2 as a biomarker for predicting cisplatin response in lung cancer patients and as a molecular therapeutic agent for enhancing response and resensitizing nonresponders to cisplatin treatment.

Yi Lo PH, Chung Leung AC, Xiong W, et al.
Expression of candidate chromosome 3p21.3 tumor suppressor genes and down-regulation of BLU in some esophageal squamous cell carcinomas.
Cancer Lett. 2006; 234(2):184-92 [PubMed] Related Publications
The expression of six chromosome 3p21.3 candidate tumor suppressor genes (BLU, FUS2, HYAL2, NPRL2, RASSF1A, and SEMA3B) in esophageal squamous cell carcinoma (ESCC) has been investigated. Reduced expression of BLU was detected in some ESCC cell lines and tumor tissues and the difference was quantitated by real-time quantitative polymerase chain reaction. Methylation specific-PCR revealed the down-regulation of BLU by epigenetic inactivation. However, exogenous expression of BLU did not functionally suppress tumorigenicity in nude mice. These results suggest that over-expression of BLU alone is not sufficient to inhibit tumorigenicity. Further studies on BLU interacting proteins are required to elucidate the possible role of BLU in the development of ESCC.

Li J, Wang F, Haraldson K, et al.
Functional characterization of the candidate tumor suppressor gene NPRL2/G21 located in 3p21.3C.
Cancer Res. 2004; 64(18):6438-43 [PubMed] Related Publications
Initial analysis identified the NPRL2/G21 gene located in 3p21.3C, the lung cancer region, as a strong candidate tumor suppressor gene. Here we provide additional evidence of the tumor suppressor function of NPRL2/G21. The gene has highly conserved homologs/orthologs ranging from yeast to humans. The yeast ortholog, NPR2, shows three highly conserved regions with 32 to 36% identity over the whole length. By sequence analysis, the main product of NPRL2/G21 encodes a soluble protein that has a bipartite nuclear localization signal, a protein-binding domain, similarity to the MutS core domain, and a newly identified nitrogen permease regulator 2 domain with unknown function. The gene is highly expressed in many tissues. We report inactivating mutations in a variety of tumors and cancer cell lines, growth suppression of tumor cells with tet-controlled NPRL2/G21 transgenes on plastic Petri dishes, and suppression of tumor formation in SCID mice. Screening of 7 renal, 5 lung, and 7 cervical carcinoma cell lines showed homozygous deletions in the 3' end of NPRL2 in 2 renal, 3 lung, and 1 cervical (HeLa) cell line. Deletions in the 3' part of NPRL2 could result in improper splicing, leading to the loss of the 1.8 kb functional NPRL2 mRNA. We speculate that the NPRL2/G21 nuclear protein may be involved in mismatch repair, cell cycle checkpoint signaling, and activation of apoptotic pathway(s). The yeast NPR2 was shown to be a target of cisplatin, suggesting that the human NPRL2/G21 may play a similar role. At least two homozygous deletions of NPRL2/G21 were detected in 6 tumor biopsies from various locations and with microsatellite instability. This study, together with previously obtained results, indicates that NPRL2 is a multiple tumor suppressor gene.

Chow LS, Lo KW, Kwong J, et al.
RASSF1A is a target tumor suppressor from 3p21.3 in nasopharyngeal carcinoma.
Int J Cancer. 2004; 109(6):839-47 [PubMed] Related Publications
Deletion on the short arm of chromosome 3 is one of the most important genetic abnormalities in the tumorigenesis of nasopharyngeal carcinoma (NPC). Both physical mapping and functional studies have targeted an NPC-related tumor suppressor gene(s) to chromosome 3p21.3. We have reported recently that RASSF1A gene, located on a 120-kb minimal deletion region on 3p21.3, was frequently inactivated by promoter hypermethylation in NPC. We further confirmed that RASSF1A is the critical target tumor suppressor from 3p21.3, with the evidence that loss of expression and aberrant methylation of the other 8 candidate genes/transcripts (HYAL2, FUS1, RASSF1C, BLU, NPRL2, 101F6, PL6 and CACNA2D2) in this 120-kb region were rare in NPC samples. The contribution of RASSF1A in NPC tumorigenesis was investigated by restoring its expression in a RASSF1A deficient cell line, C666-1. Transient transfection of wild-type RASSF1A resulted in marked growth inhibition in NPC cells. Isolated stable clones expressing wild-type RASSF1A demonstrated retarded cell proliferation in vitro. Soft-agar assay also showed decreased number and sizes of colony formed in these clones. In vivo nude mice assay demonstrated the dramatic reduction of tumorigenic potential in the RASSF1A-transfected clones. Our results provide strong evidence to support RASSF1A as a target tumor suppressor gene on 3p21.3 in NPC.

Ji L, Nishizaki M, Gao B, et al.
Expression of several genes in the human chromosome 3p21.3 homozygous deletion region by an adenovirus vector results in tumor suppressor activities in vitro and in vivo.
Cancer Res. 2002; 62(9):2715-20 [PubMed] Free Access to Full Article Related Publications
A group of candidate tumor suppressor genes (designated CACNA2D2, PL6, 101F6, NPRL2, BLU, RASSF1, FUS1, HYAL2, and HYAL1) has been identified in a 120-kb critical tumor homozygous deletion region (found in lung and breast cancers) of human chromosome 3p21.3. We studied the effects of six of these 3p21.3 genes (101F6, NPRL2, BLU, FUS1, HYAL2, and HYAL1) on tumor cell proliferation and apoptosis in human lung cancer cells by recombinant adenovirus-mediated gene transfer in vitro and in vivo. We found that forced expression of wild-type FUS1, 101F6, and NPRL2 genes significantly inhibited tumor cell growth by induction of apoptosis and alteration of cell cycle processes in 3p21.3 120-kb region-deficient (homozygous) H1299 and A549 cells but not in the 3p21.3 120-kb region-heterozygous H358 and the normal human bronchial epithelial cells. Intratumoral injection of Ad-101F6, Ad-FUS1, Ad-NPRL2, and Ad-HYAL2 vectors or systemic administration of protamine-complexed vectors significantly suppressed growth of H1299 and A549 tumor xenografts and inhibited A549 experimental lung metastases in nu/nu mice. Together, our results, coupled with other studies demonstrating a tumor suppressor role for the RASSSF1A isoform, suggest that multiple contiguous genes in the 3p21.3 120-kb chromosomal region may exhibit tumor suppressor activity in vitro and in vivo.

Lerman MI, Minna JD
The 630-kb lung cancer homozygous deletion region on human chromosome 3p21.3: identification and evaluation of the resident candidate tumor suppressor genes. The International Lung Cancer Chromosome 3p21.3 Tumor Suppressor Gene Consortium.
Cancer Res. 2000; 60(21):6116-33 [PubMed] Related Publications
We used overlapping and nested homozygous deletions, contig building, genomic sequencing, and physical and transcript mapping to further define a approximately 630-kb lung cancer homozygous deletion region harboring one or more tumor suppressor genes (TSGs) on chromosome 3p21.3. This location was identified through somatic genetic mapping in tumors, cancer cell lines, and premalignant lesions of the lung and breast, including the discovery of several homozygous deletions. The combination of molecular manual methods and computational predictions permitted us to detect, isolate, characterize, and annotate a set of 25 genes that likely constitute the complete set of protein-coding genes residing in this approximately 630-kb sequence. A subset of 19 of these genes was found within the deleted overlap region of approximately 370-kb. This region was further subdivided by a nesting 200-kb breast cancer homozygous deletion into two gene sets: 8 genes lying in the proximal approximately 120-kb segment and 11 genes lying in the distal approximately 250-kb segment. These 19 genes were analyzed extensively by computational methods and were tested by manual methods for loss of expression and mutations in lung cancers to identify candidate TSGs from within this group. Four genes showed loss-of-expression or reduced mRNA levels in non-small cell lung cancer (CACNA2D2/alpha2delta-2, SEMA3B [formerly SEMA(V), BLU, and HYAL1] or small cell lung cancer (SEMA3B, BLU, and HYAL1) cell lines. We found six of the genes to have two or more amino acid sequence-altering mutations including BLU, NPRL2/Gene21, FUS1, HYAL1, FUS2, and SEMA3B. However, none of the 19 genes tested for mutation showed a frequent (>10%) mutation rate in lung cancer samples. This led us to exclude several of the genes in the region as classical tumor suppressors for sporadic lung cancer. On the other hand, the putative lung cancer TSG in this location may either be inactivated by tumor-acquired promoter hypermethylation or belong to the novel class of haploinsufficient genes that predispose to cancer in a hemizygous (+/-) state but do not show a second mutation in the remaining wild-type allele in the tumor. We discuss the data in the context of novel and classic cancer gene models as applied to lung carcinogenesis. Further functional testing of the critical genes by gene transfer and gene disruption strategies should permit the identification of the putative lung cancer TSG(s), LUCA, Analysis of the approximately 630-kb sequence also provides an opportunity to probe and understand the genomic structure, evolution, and functional organization of this relatively gene-rich region.

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