STAG2

Gene Summary

Gene:STAG2; stromal antigen 2
Aliases: SA2, SA-2, SCC3B, NEDXCF, bA517O1.1
Location:Xq25
Summary:The protein encoded by this gene is a subunit of the cohesin complex, which regulates the separation of sister chromatids during cell division. Targeted inactivation of this gene results in chromatid cohesion defects and aneuploidy, suggesting that genetic disruption of cohesin is a cause of aneuploidy in human cancer. Alternatively spliced transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Sep 2013]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:cohesin subunit SA-2
Source:NCBIAccessed: 29 August, 2019

Ontology:

What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 29 August 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 29 August, 2019 using data from PubMed, MeSH and CancerIndex

Latest Publications: STAG2 (cancer-related)

Mondal G, Stevers M, Goode B, et al.
A requirement for STAG2 in replication fork progression creates a targetable synthetic lethality in cohesin-mutant cancers.
Nat Commun. 2019; 10(1):1686 [PubMed] Free Access to Full Article Related Publications
Cohesin is a multiprotein ring that is responsible for cohesion of sister chromatids and formation of DNA loops to regulate gene expression. Genomic analyses have identified that the cohesin subunit STAG2 is frequently inactivated by mutations in cancer. However, the reason STAG2 mutations are selected during tumorigenesis and strategies for therapeutically targeting mutant cancer cells are largely unknown. Here we show that STAG2 is essential for DNA replication fork progression, whereby STAG2 inactivation in non-transformed cells leads to replication fork stalling and collapse with disruption of interaction between the cohesin ring and the replication machinery as well as failure to establish SMC3 acetylation. As a consequence, STAG2 mutation confers synthetic lethality with DNA double-strand break repair genes and increased sensitivity to select cytotoxic chemotherapeutic agents and PARP or ATR inhibitors. These studies identify a critical role for STAG2 in replication fork procession and elucidate a potential therapeutic strategy for cohesin-mutant cancers.

Han Y, Zheng Q, Tian Y, et al.
Identification of a nine-gene panel as a prognostic indicator for recurrence with muscle-invasive bladder cancer.
J Surg Oncol. 2019; 119(8):1145-1154 [PubMed] Related Publications
BACKGROUND AND OBJECTIVES: Bladder cancer is one of the most common and highly recurrent cancers worldwide. Recurrence-associated genes may potentially predict cancer recurrence. We aimed to construct a recurrence-associated gene panel to improve the prognostic prediction of bladder cancer.
METHODS: Based on DNA sequencing and clinical data from the TCGA-BLCA project, we identified 10 potential driver genes significantly associated with recurrence of bladder cancer. We performed multivariable logistic regression analysis to construct an optimized recurrence prediction model with nine recurrence-associated genes (EME1, AKAP9, ZNF91, PARD3, STAG2, ZFP36L2, METTL3, POLR3B, and MUC7) and clinical information as the independent variables.
RESULTS: The area under the receiver operating characteristic (ROC) curve was 0.80 in this model, much higher than that of the baseline model (AUC = 0.73) and the same trend was also validated in its subset. Decision curve analysis also revealed that there is a significant net benefit gained by adding nine genes mutation to the baseline model. Furthermore, Kaplan-Meier survival analysis showed that eight out of the nine genes (excluding MUC7) had good effects on the overall prognosis of patients.
CONCLUSIONS: This nine-gene panel will most likely be a useful tool for prognostic evaluation and will facilitate the personalized management of patients with bladder cancer.

Meisenberg C, Pinder SI, Hopkins SR, et al.
Repression of Transcription at DNA Breaks Requires Cohesin throughout Interphase and Prevents Genome Instability.
Mol Cell. 2019; 73(2):212-223.e7 [PubMed] Free Access to Full Article Related Publications
Cohesin subunits are frequently mutated in cancer, but how they function as tumor suppressors is unknown. Cohesin mediates sister chromatid cohesion, but this is not always perturbed in cancer cells. Here, we identify a previously unknown role for cohesin. We find that cohesin is required to repress transcription at DNA double-strand breaks (DSBs). Notably, cohesin represses transcription at DSBs throughout interphase, indicating that this is distinct from its known role in mediating DNA repair through sister chromatid cohesion. We identified a cancer-associated SA2 mutation that supports sister chromatid cohesion but is unable to repress transcription at DSBs. We further show that failure to repress transcription at DSBs leads to large-scale genome rearrangements. Cancer samples lacking SA2 display mutational patterns consistent with loss of this pathway. These findings uncover a new function for cohesin that provides insights into its frequent loss in cancer.

Vizcaino MA, Palsgrove DN, Yuan M, et al.
Granular cell astrocytoma: an aggressive IDH-wildtype diffuse glioma with molecular genetic features of primary glioblastoma.
Brain Pathol. 2019; 29(2):193-204 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Granular cell astrocytoma (GCA) is a rare adult infiltrating glioma subtype. We studied a series of 39 GCAs. Median age of presentation was 57.8 years and most cases developed in the frontal or temporal lobes. Tumors included grade II (n = 14), grade III (n = 11), and grade IV (n = 14) by WHO criteria. Granular cell morphology was diffuse in 31 (79%) cases and partial in eight (21%). Immunohistochemistry showed frequent positivity for GFAP (28 of 31), OLIG2 (16 of 16), and CD68 (27 of 30), but HAM56, CD163, and IBA-1 histiocytic markers were all negative (22 of 22). IDH1(R132H) was negative in all the cases tested (16 of 16), while ATRX expression was retained (12 of 12). Cytogenetics demonstrated monosomy 10 (6 of 6) cases, +7 in 4 (of 6), -13q in 4 of 6, and -14 in 4 of 6. Next-generation sequencing demonstrated mutations in PTEN/PIK3 genes in 6/13 (46%), NF1 in 3 of 10 (30%), TP53 in 3 of 13 (23%), PALB2 in 3 of 10 (30%), STAG2 in 3 of 10 (30%), EGFR mutation/amplification in 3 of 13 (23%), and AR in 2 of 10 (20%). CDKN2A/B deletion was identified in 5 of 13 (30%) cases (homozygous deletion in 4). The TERT C228T mutation was identified in 9 of 13 (69%). No mutations were encountered in IDH1, IDH2, CIC, FUBP1, H3F3A, BRAF or ATRX genes. The mean overall survival was 11.3 months. Patients >60 years old at diagnosis had a worse survival than patients <60 years (P = 0.001). There were no statistically significant differences in survival by WHO grade, extent of granular cell change, sex or MIB-1 (P > 0.05). GCA is a variant of IDH-wildtype diffuse glioma with aggressive behavior irrespective of grade and extent of granular cell morphology, and with molecular genetic features corresponding to primary glioblastoma.

Győrffy B, Pongor L, Bottai G, et al.
An integrative bioinformatics approach reveals coding and non-coding gene variants associated with gene expression profiles and outcome in breast cancer molecular subtypes.
Br J Cancer. 2018; 118(8):1107-1114 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
BACKGROUND: Sequence variations in coding and non-coding regions of the genome can affect gene expression and signalling pathways, which in turn may influence disease outcome.
METHODS: In this study, we integrated somatic mutations, gene expression and clinical data from 930 breast cancer patients included in the TCGA database. Genes associated with single mutations in molecular breast cancer subtypes were identified by the Mann-Whitney U-test and their prognostic value was evaluated by Kaplan-Meier and Cox regression analyses. Results were confirmed using gene expression profiles from the Metabric data set (n = 1988) and whole-genome sequencing data from the TCGA cohort (n = 117).
RESULTS: The overall mutation rate in coding and non-coding regions were significantly higher in ER-negative/HER2-negative tumours (P = 2.8E-03 and P = 2.4E-07, respectively). Recurrent sequence variations were identified in non-coding regulatory regions of several cancer-associated genes, including NBPF1, PIK3CA and TP53. After multivariate regression analysis, gene signatures associated with three coding mutations (CDH1, MAP3K1 and TP53) and two non-coding variants (CRTC3 and STAG2) in cancer-related genes predicted prognosis in ER-positive/HER2-negative tumours.
CONCLUSIONS: These findings demonstrate that sequence alterations influence gene expression and oncogenic pathways, possibly affecting the outcome of breast cancer patients. Our data provide potential opportunities to identify non-coding variations with functional and clinical relevance in breast cancer.

Aquila L, Ohm J, Woloszynska-Read A
The role of STAG2 in bladder cancer.
Pharmacol Res. 2018; 131:143-149 [PubMed] Related Publications
Stromal Antigen 2 (STAG2) is one of four components of the cohesin complex and predominantly functions in sister chromatid cohesion and segregation. STAG2 is the most frequently mutated cohesin subunit and was recently identified as a gene that is commonly altered in bladder cancer. The significance of these mutations remains controversial. Some studies associate loss of STAG2 expression with low stage and low grade bladder tumors, as well as with improved clinical outcomes. In other cases, STAG2 inactivation has been shown to be a predictor of worse outcome for these patients. The role of STAG2 in aneuploidy also remains controversial. Loss of STAG2 is associated with significant changes in chromosome number in certain cell lines, while in others, aneuploidy is not induced or results remain inconclusive. At this time, little is known about the influence of STAG2 on cellular migration, invasion, proliferation, and cell death, and such studies are required to determine the role of STAG2 in bladder cancer and other malignancies.

Viny AD, Levine RL
Cohesin mutations in myeloid malignancies made simple.
Curr Opin Hematol. 2018; 25(2):61-66 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
PURPOSE OF REVIEW: Recurrent loss of function mutations within genes of the cohesin complex have been identified in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). STAG2 is the most commonly mutated cohesin member in AML as well as solid tumors. STAG2 is recurrently, mutated in Ewing's Sarcoma, bladder cancer, and glioblastoma, and is one of only ten genes known to be recurrently mutated in over four distinct tissue types of human cancer RECENT FINDINGS: The cohesin complex, a multiprotein ring, is canonically known to align and stabilize replicated chromosomes prior to cell division. Although initially thought to lead to unequal chromosomal separation in dividing cells, data in myeloid malignancies show this is not observed in cohesin mutant MDS/AML, either in large patient cohorts or mouse models. Mounting evidence supports a potential alternate mechanism whereby drivers of cell-type specific gene expression and hematopoietic development are impaired through alteration in three-dimensional nuclear organization and gene structure.
SUMMARY: Understanding the functional consequences of cohesin mutations in regulating lineage-specific and signal-dependent defects and in myeloid transformation will identify novel pathophysiologic mechanisms of disease and inform the development of novel therapeutic targets.

Ribeiro IP, Marques F, Barroso L, et al.
Genomic profile of oral squamous cell carcinomas with an adjacent leukoplakia or with an erythroleukoplakia that evolved after the treatment of primary tumor: A report of two cases.
Mol Med Rep. 2017; 16(5):6780-6786 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Oral leukoplakia and erythroleukoplakia are common oral potentially malignant disorders diagnosed in the oral cavity. The specific outcome of these lesions remains to be elucidated, as their malignant transformation rate exhibits great variation. The ability to predict which of those potentially malignant lesions are likely to progress to cancer would be vital to guide their future clinical management. The present study reported two patients with tongue squamous cell carcinoma: Case study 1 was diagnosed with a simultaneous leukoplakia and case study 2 developed an erythroleukoplakia following the primary tumor treatment. Whole genome copy number alterations were analyzed using array comparative genomic hybridization. The present study determined more genomic imbalances in the tissues from leukoplakia and erythroleukoplakia compared with their respective tumors. The present study also identified in tumor and potentially malignant lesions common alterations of chromosomal regions and genes, including FBXL5, UGT2B15, UGT2B28, KANSL1, GSTT1 and DUSP22, being some of these typical aberrations described in oral cancer and others are linked to chemoradioresistance. Several putative genes associated with hallmarks of malignancy that may have an important role in predicting the progression of leukoplakia and erythroleukoplakia to squamous cell carcinoma, namely gains in BNIPL, MCL1, STAG2, CSPP1 and ZNRF3 genes were also identified.

Daniloski Z, Smith S
Loss of Tumor Suppressor
Cancer Res. 2017; 77(20):5530-5542 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Sister chromatids are held together by cohesin, a tripartite ring with a peripheral SA1/2 subunit, where SA1 is required for telomere cohesion and SA2 for centromere cohesion. The

Ribera J, Zamora L, Morgades M, et al.
Copy number profiling of adult relapsed B-cell precursor acute lymphoblastic leukemia reveals potential leukemia progression mechanisms.
Genes Chromosomes Cancer. 2017; 56(11):810-820 [PubMed] Related Publications
The outcome of relapsed adult acute lymphoblastic leukemia (ALL) remains dismal despite new therapeutic approaches. Previous studies analyzing relapse samples have shown a high degree of heterogeneity regarding gene alterations without an evident relapse signature. Bone marrow or peripheral blood samples from 31 adult B-cell precursor ALL patients at first relapse, and 21 paired diagnostic samples were analyzed by multiplex ligation probe-dependent amplification (MLPA). Nineteen paired diagnostic and relapse samples of these 21 patients were also analyzed by SNP arrays. A trend to acquire homozygous CDKN2A/B deletions and a significant increase in the number of copy number alterations (CNA) was observed from diagnosis to first relapse. Evolution from an ancestral clone was the main pattern of clonal evolution. Relapse samples were extremely heterogeneous regarding CNA frequencies. However, CDKN2A/B, PAX5, ETV6, ATM, IKZF1, VPREB1, and TP53 deletions and duplications of 1q, 8q, 17q, 21, X/Y PAR1, and Xp were frequently detected at relapse. Duplications of genes involved in cell proliferation, drug resistance and stem cell homeostasis regulation, as well as deletions of KDM6A and STAG2 genes emerged as specific alterations at relapse. Genomics of relapsed adult B-cell precursor ALL is highly heterogeneous, although some recurrent lesions involved in essential pathways deregulation were frequently observed. Selective and simultaneous targeting of these deregulated pathways may improve the results of current salvage therapies.

Wang H, Zhong J, Wu C, et al.
Stromal antigen 2 functions as a tumor suppressor in bladder cancer cells.
Oncol Rep. 2017; 38(2):917-925 [PubMed] Related Publications
Stromal antigen 2 (STAG2) is a subunit of the cohesion complex that plays an important role in the normal segregation of sister chromatids during mitosis or meiosis. However, the effect of STAG2 on the bladder cancer cell proliferation, migration, and invasion has not yet been fully clarified. In this study, we aimed to characterize STAG2 expression and functional significance in BC and adjacent normal tissue. Notably, STAG2 expression was markedly lower in BC cells and tumor tissues than their normal counterparts at the gene and protein levels. Moreover, clinicopathological analysis showed that the low STAG2 expression is associated with TNM stage. Functional analysis demonstrated that STAG2 overexpression attenuated cell proliferation via G1-phase arrest, invasion, and migration, and promoted apoptosis in BC cell lines, while the opposite was observed with STAG2 knockdown cells. Furthermore, STAG2 overexpression upregulated E-cadherin, caspase-3, and caspase-7 and downregulated vimentin, matrix metalloproteinase (MMP)2, and MMP9. Collectively, these data suggest that STAG2 acts as a tumor suppressor gene in bladder cancer and may be a potential therapeutic target in BC.

Pietzak EJ, Bagrodia A, Cha EK, et al.
Next-generation Sequencing of Nonmuscle Invasive Bladder Cancer Reveals Potential Biomarkers and Rational Therapeutic Targets.
Eur Urol. 2017; 72(6):952-959 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
BACKGROUND: Molecular characterization of nonmuscle invasive bladder cancer (NMIBC) may provide a biologic rationale for treatment response and novel therapeutic strategies.
OBJECTIVE: To identify genetic alterations with potential clinical implications in NMIBC.
DESIGN, SETTING, AND PARTICIPANTS: Pretreatment index tumors and matched germline DNA from 105 patients with NMIBC on a prospective Institutional Review Board-approved protocol underwent targeted exon sequencing analysis in a Clinical Laboratory Improvement Amendments-certified clinical laboratory.
OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Comutation patterns and copy number alterations were compared across stage and grade. Associations between genomic alterations and recurrence after intravesical bacillus Calmette-Guérin (BCG) were estimated using Kaplan-Meier and Cox regression analyses.
RESULTS AND LIMITATIONS: TERT promoter mutations (73%) and chromatin-modifying gene alterations (69%) were highly prevalent across grade and stage, suggesting these events occur early in tumorigenesis. ERBB2 or FGFR3 alterations were present in 57% of high-grade NMIBC tumors in a mutually exclusive pattern. DNA damage repair (DDR) gene alterations were seen in 30% (25/82) of high-grade NMIBC tumors, a rate similar to MIBC, and were associated with a higher mutational burden compared with tumors with intact DDR genes (p<0.001). ARID1A mutations were associated with an increased risk of recurrence after BCG (hazard ratio=3.14, 95% confidence interval: 1.51-6.51, p=0.002).
CONCLUSIONS: Next-generation sequencing of treatment-naive index NMIBC tumors demonstrated that the majority of NMIBC tumors had at least one potentially actionable alteration that could serve as a target in rationally designed trials of intravesical or systemic therapy. DDR gene alterations were frequent in high-grade NMIBC and were associated with increased mutational load, which may have therapeutic implications for BCG immunotherapy and ongoing trials of systemic checkpoint inhibitors. ARID1A mutations were associated with an increased risk of recurrence after BCG therapy. Whether ARID1A mutations represent a predictive biomarker of BCG response or are prognostic in NMIBC patients warrants further investigation.
PATIENT SUMMARY: Analysis of frequently mutated genes in superficial bladder cancer suggests potential targets for personalized treatment and predictors of treatment response, and also may help develop noninvasive tumor detection tests.

Benedetti L, Cereda M, Monteverde L, et al.
Synthetic lethal interaction between the tumour suppressor STAG2 and its paralog STAG1.
Oncotarget. 2017; 8(23):37619-37632 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Cohesin is a multi-protein complex that tethers sister chromatids during mitosis and mediates DNA repair, genome compartmentalisation and regulation of gene expression. Cohesin subunits frequently acquire cancer loss-of-function alterations and act as tumour suppressors in several tumour types. This has led to increased interest in cohesin as potential target in anti-cancer therapy. Here we show that the loss-of-function of STAG2, a core component of cohesin and an emerging tumour suppressor, leads to synthetic dependency of mutated cancer cells on its paralog STAG1. STAG1 and STAG2 share high sequence identity, encode mutually exclusive cohesin subunits and retain partially overlapping functions. We inhibited STAG1 and STAG2 in several cancer cell lines where the two genes have variable mutation and copy number status. In all cases, we observed that the simultaneous blocking of STAG1 and STAG2 significantly reduces cell proliferation. We further confirmed the synthetic lethal interaction developing a vector-free CRISPR system to induce STAG1/STAG2 double gene knockout. We provide strong evidence that STAG1 is a promising therapeutic target in cancers with inactivating alterations of STAG2.

Lin DC, Mayakonda A, Dinh HQ, et al.
Genomic and Epigenomic Heterogeneity of Hepatocellular Carcinoma.
Cancer Res. 2017; 77(9):2255-2265 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Understanding the intratumoral heterogeneity of hepatocellular carcinoma is instructive for developing personalized therapy and identifying molecular biomarkers. Here we applied whole-exome sequencing to 69 samples from 11 patients to resolve the genetic architecture of subclonal diversification. Spatial genomic diversity was found in all 11 hepatocellular carcinoma cases, with 29% of driver mutations being heterogeneous, including TERT, ARID1A, NOTCH2, and STAG2. Similar with other cancer types, TP53 mutations were always shared between all tumor regions, that is, located on the "trunk" of the evolutionary tree. In addition, we found that variants within several drug targets such as KIT, SYK, and PIK3CA were mutated in a fully clonal manner, indicating their therapeutic potentials for hepatocellular carcinoma. Temporal dissection of mutational signatures suggested that mutagenic processes associated with exposure to aristolochic acid and aflatoxin might play a more important role in early, as opposed to late, stages of hepatocellular carcinoma development. Moreover, we observed extensive intratumoral epigenetic heterogeneity in hepatocellular carcinoma based on multiple independent analytical methods and showed that intratumoral methylation heterogeneity might play important roles in the biology of hepatocellular carcinoma cells. Our results also demonstrated prominent heterogeneity of intratumoral methylation even in a stable hepatocellular carcinoma genome. Together, these findings highlight widespread intratumoral heterogeneity at both the genomic and epigenomic levels in hepatocellular carcinoma and provide an important molecular foundation for better understanding the pathogenesis of this malignancy.

Patel JL, Schumacher JA, Frizzell K, et al.
Coexisting and cooperating mutations in NPM1-mutated acute myeloid leukemia.
Leuk Res. 2017; 56:7-12 [PubMed] Related Publications
NPM1 insertion mutations represent a common recurrent genetic abnormality in acute myeloid leukemia (AML) patients. The frequency of these mutations varies from approximately 30% overall up to 50% in patients with a normal karyotype. Several recent studies have exploited advances in massively parallel sequencing technology to shed light on the complex genomic landscape of AML. We hypothesize that variant allele fraction (VAF) data derived from massively parallel sequencing studies may provide further insights into the clonal architecture and pathogenesis of NPM1-driven leukemogenesis. Diagnostic peripheral blood or bone marrow samples from NPM1-mutated AML patients (n=120) were subjected to targeted sequencing using a panel of fifty-seven genes known to be commonly mutated in myeloid malignancies. NPM1 mutations were always accompanied by additional mutations and NPM1 had the highest VAF in only one case. Nearly all NPM1-mutated AML patients showed concurrent mutations in genes involved in regulation of DNA methylation (DNMT3A, TET2, IDH1, IDH2), RNA splicing (SRSF2, SF3B1), or in the cohesin complex (RAD21, SMC1A, SMC3, STAG2). Mutations in these genes had higher median VAFs that were higher (40% or greater) than the co-existing NPM1 mutations (median VAF 16.8%). Mutations associated with cell signaling pathways (FLT3, NRAS, and PTPN11) are also frequently encountered in NPM1-mutated AML cases, but had relatively low VAFs (7.0-11.9%). No cases of NPM1-mutated AML with a concurrent IDH2

Nazha A, Zarzour A, Al-Issa K, et al.
The complexity of interpreting genomic data in patients with acute myeloid leukemia.
Blood Cancer J. 2016; 6(12):e510 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Acute myeloid leukemia (AML) is a heterogeneous neoplasm characterized by the accumulation of complex genetic alterations responsible for the initiation and progression of the disease. Translating genomic information into clinical practice remained challenging with conflicting results regarding the impact of certain mutations on disease phenotype and overall survival (OS) especially when clinical variables are controlled for when interpreting the result. We sequenced the coding region for 62 genes in 468 patients with secondary AML (sAML) and primary AML (pAML). Overall, mutations in FLT3, DNMT3A, NPM1 and IDH2 were more specific for pAML whereas UTAF1, STAG2, BCORL1, BCOR, EZH2, JAK2, CBL, PRPF8, SF3B1, ASXL1 and DHX29 were more specific for sAML. However, in multivariate analysis that included clinical variables, only FLT3 and DNMT3A remained specific for pAML and EZH2, BCOR, SF3B1 and ASXL1 for sAML. When the impact of mutations on OS was evaluated in the entire cohort, mutations in DNMT3A, PRPF8, ASXL1, CBL EZH2 and TP53 had a negative impact on OS; no mutation impacted OS favorably; however, in a cox multivariate analysis that included clinical data, mutations in DNMT3A, ASXL1, CBL, EZH2 and TP53 became significant. Thus, controlling for clinical variables is important when interpreting genomic data in AML.

Chang JT, Wang F, Chapin W, Huang RS
Identification of MicroRNAs as Breast Cancer Prognosis Markers through the Cancer Genome Atlas.
PLoS One. 2016; 11(12):e0168284 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Breast cancer is the second-most common cancer and second-leading cause of cancer mortality in American women. The dysregulation of microRNAs (miRNAs) plays a key role in almost all cancers, including breast cancer. We comprehensively analyzed miRNA expression, global gene expression, and patient survival from the Cancer Genomes Atlas (TCGA) to identify clinically relevant miRNAs and their potential gene targets in breast tumors. In our analysis, we found that increased expression of 12 mature miRNAs-hsa-miR-320a, hsa-miR-361-5p, hsa-miR-103a-3p, hsa-miR-21-5p, hsa-miR-374b-5p, hsa-miR-140-3p, hsa-miR-25-3p, hsa-miR-651-5p, hsa-miR-200c-3p, hsa-miR-30a-5p, hsa-miR-30c-5p, and hsa-let-7i-5p -each predicted improved breast cancer survival. Of the 12 miRNAs, miR-320a, miR-361-5p, miR-21-5p, miR-103a-3p were selected for further analysis. By correlating global gene expression with miRNA expression and then employing miRNA target prediction analysis, we suggest that the four miRNAs may exert protective phenotypes by targeting breast oncogenes that contribute to patient survival. We propose that miR-320a targets the survival-associated genes RAD51, RRP1B, and TDG; miR-361-5p targets ARCN1; and miR-21-5p targets MSH2, RMND5A, STAG2, and UBE2D3. The results of our stringent bioinformatics approach for identifying clinically relevant miRNAs and their targets indicate that miR-320a, miR-361-5p, and miR-21-5p may contribute to breast cancer survival.

Chesnais V, Arcangeli ML, Delette C, et al.
Architectural and functional heterogeneity of hematopoietic stem/progenitor cells in non-del(5q) myelodysplastic syndromes.
Blood. 2017; 129(4):484-496 [PubMed] Related Publications
Myelodysplastic syndromes (MDSs) are hematopoietic stem cell disorders in which recurrent mutations define clonal hematopoiesis. The origin of the phenotypic diversity of non-del(5q) MDS remains unclear. Here, we investigated the clonal architecture of the CD34

Gaidzik VI, Teleanu V, Papaemmanuil E, et al.
RUNX1 mutations in acute myeloid leukemia are associated with distinct clinico-pathologic and genetic features.
Leukemia. 2016; 30(11):2160-2168 [PubMed] Related Publications
We evaluated the frequency, genetic architecture, clinico-pathologic features and prognostic impact of RUNX1 mutations in 2439 adult patients with newly-diagnosed acute myeloid leukemia (AML). RUNX1 mutations were found in 245 of 2439 (10%) patients; were almost mutually exclusive of AML with recurrent genetic abnormalities; and they co-occurred with a complex pattern of gene mutations, frequently involving mutations in epigenetic modifiers (ASXL1, IDH2, KMT2A, EZH2), components of the spliceosome complex (SRSF2, SF3B1) and STAG2, PHF6, BCOR. RUNX1 mutations were associated with older age (16-59 years: 8.5%; ⩾60 years: 15.1%), male gender, more immature morphology and secondary AML evolving from myelodysplastic syndrome. In univariable analyses, RUNX1 mutations were associated with inferior event-free (EFS, P<0.0001), relapse-free (RFS, P=0.0007) and overall survival (OS, P<0.0001) in all patients, remaining significant when age was considered. In multivariable analysis, RUNX1 mutations predicted for inferior EFS (P=0.01). The effect of co-mutation varied by partner gene, where patients with the secondary genotypes RUNX1

Fusco N, Geyer FC, De Filippo MR, et al.
Genetic events in the progression of adenoid cystic carcinoma of the breast to high-grade triple-negative breast cancer.
Mod Pathol. 2016; 29(11):1292-1305 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Adenoid cystic carcinoma of the breast is a rare histological type of triple-negative breast cancer with an indolent clinical behavior, often driven by the MYB-NFIB fusion gene. Here we sought to define the repertoire of somatic genetic alterations in two adenoid cystic carcinomas associated with high-grade triple-negative breast cancer. The different components of each case were subjected to copy number profiling and massively parallel sequencing targeting all exons and selected regulatory and intronic regions of 488 genes. Reverse transcription PCR and fluorescence in situ hybridization were employed to investigate the presence of the MYB-NFIB translocation. The MYB-NFIB fusion gene was detected in both adenoid cystic carcinomas and their associated high-grade triple-negative breast cancer components. Although the distinct components of both cases displayed similar patterns of gene copy number alterations, massively parallel sequencing analysis revealed intratumor genetic heterogeneity. In case 1, progression from the trabecular adenoid cystic carcinoma to the high-grade triple-negative breast cancer was found to involve clonal shifts with enrichment of mutations affecting EP300, NOTCH1, ERBB2 and FGFR1 in the high-grade triple-negative breast cancer. In case 2, a clonal KMT2C mutation was present in the cribriform adenoid cystic carcinoma, solid adenoid cystic carcinoma and high-grade triple-negative breast cancer components, whereas a mutation affecting MYB was present only in the solid and high-grade triple-negative breast cancer areas and additional three mutations targeting STAG2, KDM6A and CDK12 were restricted to the high-grade triple-negative breast cancer. In conclusion, adenoid cystic carcinomas of the breast with high-grade transformation are underpinned by the MYB-NFIB fusion gene and, akin to other forms of cancer, may be constituted by a mosaic of cancer cell clones at diagnosis. The progression from adenoid cystic carcinoma to high-grade triple-negative breast cancer of no special type may involve the selection of neoplastic clones and/or the acquisition of additional genetic alterations.

Shiba N, Yoshida K, Shiraishi Y, et al.
Whole-exome sequencing reveals the spectrum of gene mutations and the clonal evolution patterns in paediatric acute myeloid leukaemia.
Br J Haematol. 2016; 175(3):476-489 [PubMed] Related Publications
Acute myeloid leukaemia (AML) is a molecularly and clinically heterogeneous disease. Targeted sequencing efforts have identified several mutations with diagnostic and prognostic values in KIT, NPM1, CEBPA and FLT3 in both adult and paediatric AML. In addition, massively parallel sequencing enabled the discovery of recurrent mutations (i.e. IDH1/2 and DNMT3A) in adult AML. In this study, whole-exome sequencing (WES) of 22 paediatric AML patients revealed mutations in components of the cohesin complex (RAD21 and SMC3), BCORL1 and ASXL2 in addition to previously known gene mutations. We also revealed intratumoural heterogeneities in many patients, implicating multiple clonal evolution events in the development of AML. Furthermore, targeted deep sequencing in 182 paediatric AML patients identified three major categories of recurrently mutated genes: cohesion complex genes [STAG2, RAD21 and SMC3 in 17 patients (8·3%)], epigenetic regulators [ASXL1/ASXL2 in 17 patients (8·3%), BCOR/BCORL1 in 7 patients (3·4%)] and signalling molecules. We also performed WES in four patients with relapsed AML. Relapsed AML evolved from one of the subclones at the initial phase and was accompanied by many additional mutations, including common driver mutations that were absent or existed only with lower allele frequency in the diagnostic samples, indicating a multistep process causing leukaemia recurrence.

Repo H, Löyttyniemi E, Nykänen M, et al.
The Expression of Cohesin Subunit SA2 Predicts Breast Cancer Survival.
Appl Immunohistochem Mol Morphol. 2016; 24(9):615-621 [PubMed] Related Publications
Cohesin is one of the main regulators of sister chromatid separation during the metaphase/anaphase transition. It is a multiprotein complex consisting of 4 core subunits, one of those being the SA2 subunit. SA2 plays the final role in dismantling the cohesion complex from the sister chromatids and also functions in DNA double-strand break repair and gene regulation. There is increasing evidence regarding the involvement of both overexpression and underexpression of cohesin in cancer. Here, we present expression patterns of SA2 in different types of human breast tissue, and the prognostic analysis in the material from breast cancer patients with long-term follow-up. SA2 immunoexpression was evaluated in benign, precancerous, and malignant breast tissue, and was classified into low-intensity or high-intensity groups. The DNA content was determined by image cytometry on breast cancer cell imprints. Prognostic analyses were based on 445 breast cancer patients with upto 20 years' follow-up. SA2 immunoexpression was equally high in both benign and precancerous breast tissue. Instead, 72% of the invasive breast cancers showed deficient SA2 expression. These patients were also associated with an unfavorable outcome as indicated by a 1.6-fold risk of breast cancer death (P=0.0208). The majority (75%) of the patients with low SA2 expression were alive 6.0 years after the diagnosis, whereas the majority of the patients with high SA2 expression survived 17.6 years after the diagnosis. No statistically significant association could be detected between SA2 immunoexpression and DNA aneuploidy. Our results and previous literature indicate that decreased SA2 immunoexpression is associated with malignant breast disease and a particularly unfavorable course of disease.

Jung SH, Kim MS, Jung CK, et al.
Mutational burdens and evolutionary ages of thyroid follicular adenoma are comparable to those of follicular carcinoma.
Oncotarget. 2016; 7(43):69638-69648 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Follicular thyroid adenoma (FTA) precedes follicular thyroid carcinoma (FTC) by definition with a favorable prognosis compared to FTC. However, the genetic mechanism of FTA to FTC progression remains unknown. For this, it is required to disclose FTA and FTC genomes in mutational and evolutionary perspectives. We performed whole-exome sequencing and copy number profiling of 14 FTAs and 13 FTCs, which exhibited previously-known gene mutations (NRAS, HRAS, BRAF, TSHR and EIF1AX) and copy number alterations (CNAs) (22q loss and 1q gain) in follicular tumors. In addition, we found eleven potential cancer-related genes with mutations (EZH1, SPOP, NF1, TCF12, IGF2BP3, KMT2C, CNOT1, BRIP1, KDM5C, STAG2 and MAP4K3) that have not been reported in thyroid follicular tumors. Of note, FTA genomes showed comparable levels of mutations to FTC in terms of the number, sequence composition and functional consequences (potential driver mutations) of mutations. Analyses of evolutionary ages using somatic mutations as molecular clocks further identified that FTA genomes were as old as FTC genomes. Whole-transcriptome sequencing did not find any gene fusions with potential significance. Our data indicate that FTA genomes may be as old as FTC genomes, thus suggesting that follicular thyroid tumor genomes during the transition from FTA to FTC may stand stable at genomic levels in contrast to the discernable changes at pathologic and clinical levels. Also, the data suggest a possibility that the mutational profiles obtained from early biopsies may be useful for the molecular diagnosis and therapeutics of follicular tumor patients.

Albanell J, Svedman C, Gligorov J, et al.
Pooled analysis of prospective European studies assessing the impact of using the 21-gene Recurrence Score assay on clinical decision making in women with oestrogen receptor-positive, human epidermal growth factor receptor 2-negative early-stage breast cancer.
Eur J Cancer. 2016; 66:104-13 [PubMed] Related Publications
PURPOSE: The 21-gene Recurrence Score assay (Oncotype DX) provides prognostic/predictive information in oestrogen receptor positive (ER+) early breast cancer, but access/reimbursement has been limited in most European countries in the absence of prospective outcome data. Recently, two large prospective studies and a real-life 5-year outcome study have been reported. We performed a pooled analysis of prospective European impact studies to generate robust data on impact of use in different clinical subgroups.
METHODS: The analysis included four studies (French, German, Spanish, and British) in ER+ human epidermal growth factor receptor 2-negative breast cancer patients (n = 527). Node-positive patients were excluded.
RESULTS: The analysis demonstrated that treatment recommendations changed in 32% of patients post-testing; chemotherapy recommendation rate decreased from 55% to 34%. Change rates in the individual studies ranged from 30% to 37%. The highest change rates were in patients originally recommended chemotherapy and in grade II tumours; there was no subgroup without a treatment recommendation change. Notably, 31% of patients with an intermediate Recurrence Score result had a treatment recommendation change suggesting that testing provides actionable information in this group. With the exception of the German study (where chemotherapy rates remained high [41%] post-testing), between-study variability in treatment recommendations decreased post-testing (chemotherapy: from 36-52% to 26-29%; hormonal therapy: from 48-64% to 71-74%). Physicians' confidence regarding treatment recommendations improved in all the studies after testing.
CONCLUSION: Recurrence Score testing led to changes in adjuvant chemotherapy use in approximately a third of patients, to an overall reduced chemotherapy use, and to more homogeneous decision making.

Ganguly BB, Kadam NN
Mutations of myelodysplastic syndromes (MDS): An update.
Mutat Res Rev Mutat Res. 2016 Jul-Sep; 769:47-62 [PubMed] Related Publications
The plethora of knowledge gained on myelodysplastic syndromes (MDS), a heterogeneous pre-malignant disorder of hematopoietic stem cells, through sequencing of several pathway genes has unveiled molecular pathogenesis and its progression to AML. Evolution of phenotypic classification and risk-stratification based on peripheral cytopenias and blast count has moved to five-tier risk-groups solely concerning chromosomal aberrations. Increased frequency of complex abnormalities, which is associated with genetic instability, defines the subgroup of worst prognosis in MDS. However, the independent effect of monosomal karyotype remains controversial. Recent discoveries on mutations in RNA-splicing machinery (SF3B1, SRSF2, ZRSR2, U2AF1, U2AF2); DNA methylation (TET2, DNMT3A, IDH1/2); chromatin modification (ASXL1, EZH2); transcription factor (TP53, RUNX1); signal transduction/kinases (FLT3, JAK2); RAS pathway (KRAS, NRAS, CBL, NF1, PTPN11); cohesin complex (STAG2, CTCF, SMC1A, RAD21); DNA repair (ATM, BRCC3, DLRE1C, FANCL); and other pathway genes have given insights into the independent effects and interaction of co-occurrence of mutations on disease-phenotype. RNA-splicing and DNA methylation mutations appeared to occur early and are reported as 'founder' mutations in over 50% MDS patients. TET2 mutation, through altered DNA methylation, has been found to have independent prognostic response to hypomethylating agents. Moreover, presence of DNMT3A, TET2 and ASXL1 mutations in normal elderly individuals forms the basis of understanding that accumulation of somatic mutations may not cause direct disease-development; however, cooperation with other mutations in the genes that are frequently mutated in myeloid and other hematopoietic cancers might result in clonal expansion through self-renewal and/or proliferation of hematopoietic stem cells. Identification of small molecules as inhibitors of epigenetic mutations has opened avenues for tailoring targeted drug development. The recommendations of a Clinical Advisory Committee is being considered by WHO for a revised classification of risk-groups of MDS, which is likely to be published in mid 2016, based on the new developments and discoveries of gene mutations.

Sun QY, Ding LW, Tan KT, et al.
Ordering of mutations in acute myeloid leukemia with partial tandem duplication of MLL (MLL-PTD).
Leukemia. 2017; 31(1):1-10 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Partial tandem duplication of MLL (MLL-PTD) characterizes acute myeloid leukemia (AML) patients often with a poor prognosis. To understand the order of occurrence of MLL-PTD in relation to other major AML mutations and to identify novel mutations that may be present in this unique AML molecular subtype, exome and targeted sequencing was performed on 85 MLL-PTD AML samples using HiSeq-2000. Genes involved in the cohesin complex (STAG2), a splicing factor (U2AF1) and a poorly studied gene, MGA were recurrently mutated, whereas NPM1, one of the most frequently mutated AML gene, was not mutated in MLL-PTD patients. Interestingly, clonality analysis suggests that IDH2/1, DNMT3A, U2AF1 and TET2 mutations are clonal and occur early, and MLL-PTD likely arises after these initial mutations. Conversely, proliferative mutations (FLT3, RAS), typically appear later, are largely subclonal and tend to be unstable. This study provides important insights for understanding the relative importance of different mutations for defining a targeted therapeutic strategy for MLL-PTD AML patients.

França JA, Diniz MG, Bernardes VF, et al.
Cohesin subunits, STAG1 and STAG2, and cohesin regulatory factor, PDS5b, in oral squamous cells carcinomas.
J Oral Pathol Med. 2017; 46(3):188-193 [PubMed] Related Publications
BACKGROUND: Cohesin complex is responsible for sister chromatid cohesion. STAG1/STAG2 is part of the complex, which is regulated by PDS5B. Alterations in these genes were described in tumors. PDS5B is a negative regulator of cell proliferation. We aimed to assess molecular alterations in these genes in oral squamous cell carcinoma (OSCC) and predict their expression by the expression of 84 cell cycle genes. In addition, we investigated whether pds5b protein expression impacted ki-67 and p53 immunopositivity.
METHODS: We assessed loss of heterozygosity (LOH) at STAG1 and STAG2 loci in 15 OSCC using three polymorphic markers. Associations between the immunoexpression of pds5b and ki-67 and p53 were tested in 62 samples. Differences between transcriptional levels of STAG1, STAG2, and PDS5B between OSCC and normal oral mucosa (NM) were evaluated by qPCR. An 84 cell cycle genes qPCR array was carried with OSCC samples, and STAG1, STAG2, and PDS5B were independently used as response variables in multiple linear regression models.
RESULTS: Loss of heterozygosity in at least one marker was observed in three samples. pds5b, p53, and ki-67 were highly expressed, and no association was found between pds5b immunoexpression and ki-67 or p53 (P > 0.05). OSCC and NM showed similar transcriptional levels of STAG1, STAG2, and PDS5B. STAG1 and CUL3 expression seem to be related (P = 0.004).
CONCLUSIONS: There is LOH at STAG1 and STAG2 loci in OSCC, but OSCC and NM showed similar transcriptional levels of STAG1, STAG2, and PDS5B. pds5b immunoexpression in OSCC was high, but it was not associated with proliferation cell index.

Hill VK, Kim JS, Waldman T
Cohesin mutations in human cancer.
Biochim Biophys Acta. 2016; 1866(1):1-11 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Cohesin is a highly-conserved protein complex that plays important roles in sister chromatid cohesion, chromatin structure, gene expression, and DNA repair. In humans, cohesin is a ubiquitously expressed, multi-subunit protein complex composed of core subunits SMC1A, SMC3, RAD21, STAG1/2 and regulatory subunits WAPL, PDS5A/B, CDCA5, NIPBL, and MAU2. Recent studies have demonstrated that genes encoding cohesin subunits are somatically mutated in a wide range of human cancers. STAG2 is the most commonly mutated subunit, and in a recent analysis was identified as one of only 12 genes that are significantly mutated in four or more cancer types. In this review we summarize the findings reported to date and comment on potential functional implications of cohesin mutation in the pathogenesis of human cancer.

Morgado M, Sutton MN, Simmons M, et al.
Tumor necrosis factor-α and interferon-γ stimulate MUC16 (CA125) expression in breast, endometrial and ovarian cancers through NFκB.
Oncotarget. 2016; 7(12):14871-84 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Transmembrane mucins (TMs) are restricted to the apical surface of normal epithelia. In cancer, TMs not only are over-expressed, but also lose polarized distribution. MUC16/CA125 is a high molecular weight TM carrying the CA125 epitope, a well-known molecular marker for human cancers. MUC16 mRNA and protein expression was mildly stimulated by low concentrations of TNFα (2.5 ng/ml) or IFNγ (20 IU/ml) when used alone; however, combined treatment with both cytokines resulted in a moderate (3-fold or less) to large (> 10-fold) stimulation of MUC16 mRNA and protein expression in a variety of cancer cell types indicating that this may be a general response. Human cancer tissue microarray analysis indicated that MUC16 expression directly correlates with TNFα and IFNγ staining intensities in certain cancers. We show that NFκB is an important mediator of cytokine stimulation of MUC16 since siRNA-mediated knockdown of NFκB/p65 greatly reduced cytokine responsiveness. Finally, we demonstrate that the 250 bp proximal promoter region of MUC16 contains an NFκB binding site that accounts for a large portion of the TNFα response. Developing methods to manipulate MUC16 expression could provide new approaches to treating cancers whose growth or metastasis is characterized by elevated levels of TMs, including MUC16.

Ibáñez M, Carbonell-Caballero J, García-Alonso L, et al.
The Mutational Landscape of Acute Promyelocytic Leukemia Reveals an Interacting Network of Co-Occurrences and Recurrent Mutations.
PLoS One. 2016; 11(2):e0148346 [PubMed] Article available free on PMC after 01/03/2020 Related Publications
Preliminary Acute Promyelocytic Leukemia (APL) whole exome sequencing (WES) studies have identified a huge number of somatic mutations affecting more than a hundred different genes mainly in a non-recurrent manner, suggesting that APL is a heterogeneous disease with secondary relevant changes not yet defined. To extend our knowledge of subtle genetic alterations involved in APL that might cooperate with PML/RARA in the leukemogenic process, we performed a comprehensive analysis of somatic mutations in APL combining WES with sequencing of a custom panel of targeted genes by next-generation sequencing. To select a reduced subset of high confidence candidate driver genes, further in silico analysis were carried out. After prioritization and network analysis we found recurrent deleterious mutations in 8 individual genes (STAG2, U2AF1, SMC1A, USP9X, IKZF1, LYN, MYCBP2 and PTPN11) with a strong potential of being involved in APL pathogenesis. Our network analysis of multiple mutations provides a reliable approach to prioritize genes for additional analysis, improving our knowledge of the leukemogenesis interactome. Additionally, we have defined a functional module in the interactome of APL. The hypothesis is that the number, or the specific combinations, of mutations harbored in each patient might not be as important as the disturbance caused in biological key functions, triggered by several not necessarily recurrent mutations.

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