Project description:Aneuploidy is among the most common hallmarks of cancer, yet the underlying genetic mechanisms are still poorly defined. We have recently identified STAG2 as a gene that is mutated in human cancer and whose inactivation leads directly to chromosomal instability and aneuploidy. However, no single tumor type has yet been identified in which inactivation of a cohesin subunit represents a predominant mutational event. Here we used immunohistochemistry to screen a panel of 2,214 tumors from each of the major human tumor types to identify additional tumor types harboring somatic loss of STAG2. Strikingly, STAG2 expression was completely absent in 18% of urothelial carcinomas, the most common type of bladder cancer and the fifth most common cancer in the United States. DNA sequencing revealed that somatic mutations of STAG2 were present in 21% of urothelial carcinomas, which were found to be a group of highly aneuploid tumors. The acquisition of STAG2 mutations was shown to be an early event in the pathogenesis of urothelial carcinoma. STAG2 loss was significantly associated with lymph node invasion, increased disease recurrence, and reduced cancer-specific survival. These results identify STAG2 as one of the most commonly mutated genes in bladder cancer discovered to date, and demonstrate that STAG2 inactivation defines an aggressive subtype of bladder cancer with particularly poor prognosis. Affymetrix CytoScan HD Arrays were performed according to the manufacturer's directions on genomic DNA extracted directly from snap-frozen human urothelial carcinoma primary tumors. Copy number analysis using Affymetrix CytoScan HD Arrays was performed for 12 human urothelial carcinomas of the bladder with truncating mutations of the STAG2 gene.
Project description:Cohesin exists in two variants, containing either STAG1 or STAG2. STAG2 is one of the most commonly mutated genes in human cancer, and a major bladder cancer tumor suppressor. Little is known about how its inactivation contributes to tumor development. Here, we analyze the genomic distribution of STAG1 and STAG2 and perform STAG2 loss-of-function experiments using RT112 bladder cancer cells; we then analyze the resulting genomic effects by integrating gene expression and chromatin interaction data.
Project description:STAG2 is a novel UBC tumor suppressor acting through mechanisms that are different from its role to prevent aneuploidy Gene copy number analyses of STAG2 in urinary bladder tumors. R values were extracted from beadstudio and normalised using the pounds method. Log R Ratios were calculated using an average value of R from 200 cases and controls from the Epicuro study. WaviCGH was used to generate copy number calls and log R ratios in the region of STAG2 on the X chromosome were also visualised manually to determine STAG2 loss.
Project description:STAG2 is a novel UBC tumor suppressor acting through mechanisms that are different from its role to prevent aneuploidy Gene copy number analyses of STAG2 in urinary bladder tumors. R values were extracted from beadstudio and normalised using the pounds method. Log R Ratios were calculated using an average value of R from 200 cases and controls from the Epicuro study. WaviCGH was used to generate copy number calls and log R ratios in the region of STAG2 on the X chromosome were also visualised manually to determine STAG2 loss.
Project description:We have discovered frequent genetic inactivation of the STAG2 gene in diverse human cancers including glioblastoma, Ewing's sarcoma, and melanoma. STAG2 encodes a subunit of the sister chromatid cohesion complex called the "cohesin complex" that is responsible for the cohesion of sister chromatids following DNA replication and is cleaved at the metaphase to anaphase transition to enable chromosome segregation into daughter cells. Interestingly, the cohesin complex has also been implicated as a regulator of chromatin architecture and transcription. To determine the functional significance of STAG2 inactivation in cancer pathogenesis, we used somatic cell gene targeting to correct the endogenous mutations of STAG2 in two aneuploid human glioblastoma cell lines, H4 and 42MGBA. Similarly, somatic cell gene targeting was also used to introduce a nonsense mutation into codon 6 of the endogenous wild-type allele of STAG2 in HCT116 cells, a near-diploid human colorectal cancer cell line with stable karyotype. Expression profiling of these three paired sets of STAG2-proficient and deficient cells demonstrated that STAG2 does not play a global role in transcriptional regulation nor does it recurrently modulate the expression of specific tumor-promoting or suppressing genes. For further details, see Solomon et al., Mutational inactivation of STAG2 causes aneuploidy in human cancer.
Project description:Ewing sarcoma is an aggressive malignancy characterized by oncogenic rearrangements of the EWS gene with an ETS-family transcription factor, most commonly FLI. Recent comprehensive next-generation sequencing efforts have revealed few other highly recurrent mutations in this disease apart from loss-of-function mutations in STAG2 which occur in 15-20% of tumors. STAG2 is a member of the cohesin complex, which regulates sister chromatid alignment during mitosis and epigenetic regulation of gene expression. While some studies suggest that loss of STAG2 is associated with the development of aneuploidy, this is not the case in Ewing sarcoma. To investigate whether STAG2 loss effects epigenetic regulation of gene expression in Ewing sarcoma, we developed isogenic Ewing sarcoma cell lines with STAG2 knockout. We found that Ewing sarcoma cells engineered for loss of STAG2 maintain an intact cohesion complex that alternately incorporates STAG1.
Project description:Ewing sarcoma is an aggressive malignancy characterized by oncogenic rearrangements of the EWS gene with an ETS-family transcription factor, most commonly FLI. Recent comprehensive next-generation sequencing efforts have revealed few other highly recurrent mutations in this disease apart from loss-of-function mutations in STAG2 which occur in 15-20% of tumors. STAG2 is a member of the cohesin complex, which regulates sister chromatid alignment during mitosis and epigenetic regulation of gene expression. While some studies suggest that loss of STAG2 is associated with the development of aneuploidy, this is not the case in Ewing sarcoma. To investigate whether STAG2 loss affects epigenetic regulation of gene expression in Ewing sarcoma, we developed isogenic Ewing sarcoma cell lines with STAG2 knockout. We found that Ewing sarcoma cells engineered for loss of STAG2 maintain an intact cohesion complex that alternately incorporates STAG1.
Project description:Ewing sarcoma is an aggressive malignancy characterized by oncogenic rearrangements of the EWS gene with an ETS-family transcription factor, most commonly FLI. Recent comprehensive next-generation sequencing efforts have revealed few other highly recurrent mutations in this disease apart from loss-of-function mutations in STAG2 which occur in 15-20% of tumors. STAG2 is a member of the cohesin complex, which regulates sister chromatid alignment during mitosis and epigenetic regulation of gene expression. While some studies suggest that loss of STAG2 is associated with the development of aneuploidy, this is not the case in Ewing sarcoma. To investigate whether STAG2 loss effects epigenetic regulation of gene expression in Ewing sarcoma, we developed isogenic Ewing sarcoma cell lines with STAG2 knockout. We found that Ewing sarcoma cells engineered for loss of STAG2 maintain an intact cohesion complex that alternately incorporates STAG1.