Project description:ARID1A, encoding a subunit of the SWI/SNF chromatin remodeling complex, is the most mutated epigenetic regulator in human cancers. ARID1A and TP53 mutations are typically mutually exclusive. Therapeutic approaches that correlate with ARID1A mutational status remain a challenge. Here, we show that HDAC6 activity is essential in ARID1A-mutated ovarian cancers. Inhibition of HDAC6 activity using a clinically applicable small molecule inhibitor significantly improved the survival of mice bearing ARID1A-mutated ovarian tumors. This correlated with the suppression of growth and dissemination of ARID1A-mutated, but not wild-type, tumors. The dependence on HDAC6 activity in ARID1A-mutated cells correlated with a direct transcriptional repression of HDAC6 by ARID1A. HDAC6 inhibition selectively promoted apoptosis of ARID1A-mutated cells. HDAC6 directly deacetylated the Lysine 120 residue of p53, a pro-apoptotic post-translational modification. Thus, ARID1A mutation inactivates p53’ apoptotic function by upregulating HDAC6. These results indicate that pharmacological inhibition of HDAC6 is a novel therapeutic strategy involving ARID1A-mutation
Project description:Background:This study was a hypothesis generating exploration of genomic data collected at diagnosis for 19 patients, who later participated in a clinical trial. BRCA1/2 germline mutation related hereditary cancers are candidates for new immune therapeutic interventions. However, contrary to what is expected of tumors with compromised DNA repair, a prominent tumor mutation burden (TMB) in hereditary breast and ovarian cancers in this cohort, was not correlated with high global immune activity in their microenvironments. More information is needed about the relationship between genomic instability, phenotypes and immune microenvironments of BRCA1/2 related hereditary tumors in order to find appropriate markers of immune activity and the most effective anticancer immune strategies. Methods:Mining and statistical analyses of the original DNA and RNA sequencing data and data available from The Cancer Genome Atlas (TCGA) were performed using the R computing environment. To interpret the data, we have used published literature and web available resources such as Gene Ontology Tools, The Cancer immunome Atlas (TCIA) and the Cancer Research Institute iAtlas. Results: We found that BRCA1/2 germline related breast and ovarian cancers do not represent a unique phenotypic identity, but that they express a range of phenotypes similar to sporadic cancers. Importantly, BRCA2 germline mutation related breast tumors have a different profile of genomic instability compared to those related to BRCA1. However, all breast and ovarian BRCA1/2 related tumors are characterized by high homologous recombination deficiency (HRD) and low aneuploidy. Interestingly, all sporadic high grade serous ovarian cancers (HGSOC) and most of the subtypes of triple negative breast cancers (TNBC), but not other types of breast cancer, also express a high degree of HRD. Conclusion: : Tumor mutation burdon (TMB) is not associated with the magnitude of the immune response in hereditary BRCA1/2 related breast and ovarian cancers or in sporadic TNBC and sporadic HGSOC. Hereditary tumors express phenotypes as heterogenous as sporadic tumors with various degree of “BRCAness” and various characteristics of the immune microenvironments. The subtyping criteria developed for sporadic tumors can be applied for the classification of hereditary tumors and possibly also characterization of their immune microenvironment. A high HRD score may be a good candidate biomarker for response to platinum, and potentially PARP-inhibition.
Project description:ARID1A, encoding a subunit of the SWI/SNF chromatin remodeling complex, is the most frequently mutated epigenetic regulators in human cancers. ARID1A is mutated in over 50% ovarian clear cell carcinoma, a disease currently has no effective therapy. Here we show that ARID1A-mutated ovarian cancer cells are selectively sensitive to inhibition of HDAC2 activity. HDAC2 interacts with EZH2 in an ARID1A status dependent manner. HDAC2 knockdown inhibits the growth of ARID1A inactivated by not proficient ovarian cancer cells. HDAC2 functions as a co-repressor of EZH2 to suppress the expression of EZH2/ARID1A target tumor suppressor genes such as PIK3IP1, an inhibitor of PI3K/AKT signaling, to inhibit proliferation and promote apoptosis. Indeed, a FDA-approved pan-HDAC inhibitor suberoylannilide hydroxamine (SAHA) significantly suppressed the growth and reduced the ascites of the ARID1A-inactivated ovarian cancers in both orthotopic and genetic mouse models. This correlated with a significant improvement of survival of mice bearing ARID1A-mutated ovarian cancers.
Project description:Somatic mutations in cancer are a potential source of cancer specific neoantigens. Acute myeloid leukemia (AML) has common recurrent mutations shared between patients in addition to private mutations specific to individuals. We hypothesized that neoantigens derived from recurrent shared mutations would be attractive targets for future immunotherapy and sought to study the Class I and II HLA ligandomes of thirteen primary AML tumor samples and two AML cell lines (OCI-AML3 and MV4-11) using mass spectrometry. We identified two endogenous, mutation-bearing HLA Class I ligands from NPM1, which are predicted to bind the common HLA haplotypes, HLA-A*03:01 and HLA-A*02:01 respectively. We further derived CD8+ T cells from healthy donor peripheral blood samples which bound mutant-peptide loaded A*03:01 and A*02:01 tetramers, suggesting a new source of NPM1 mutation-specific T cell receptors (TCRs) for future evaluation. Since NPM1 is mutated in approximately one-third of patients with AML, the finding of endogenous NPM1 neoantigens supports future studies evaluating immunotherapeutic approaches against this target, for this subset of patients with AML.
Project description:ARID1A, an epigentic modifier, is often mutated in ovarian clear cell carcinoma (OCCC). In addition, EZH2 is frequently upregulated in OCCC. Inhibtion of EZH2 with an inhibitor (GSK126) selectively inhibits ARID1A-mutated cells. This study was designed to understand changes in gene expression profiles following EZH2 inhibition or ARID1A restoration. Chromatin remodelers such as ARID1A are frequently mutated in a broad array of cancers. However, targeted cancer therapy based on ARID1A mutation status has not been described. Intriguingly, ARID1A mutated cancers typically lack genomic instability, suggesting significant involvement of epigenetic mechanisms. Here we show that inhibition of the EZH2 methyltransferase acts in a synthetic lethal manner in ARID1A mutated cells. Remarkably, ARID1A mutation status correlated with response to EZH2 inhibitor. Genome-wide profiling revealed antagonistic roles of ARID1A and EZH2 in gene regulation. Further, we identified PIK3IP1 as a direct ARID1A/EZH2 target gene whose upregulation contributes to the observed synthetic lethality in the EZH2 inhibitor treated ARID1A mutated cells. Significantly, EZH2 inhibitor caused the regression of established ARID1A mutated tumors in vivo. Together, this data demonstrate a synthetic lethality between ARID1A mutation and EZH2 inhibition. They indicate that pharmacological inhibition of EZH2 represents a novel treatment strategy for ARID1A mutated cancers.
Project description:To determine microRNA expression in chemoresistant ovarian cancer, we have employed whole microRNA microarray expression profiling as a discovery platform to identify genes with the potential to distinguish recurrent ovarian cancer. 8 recurrent ovarian cancer tissue and 8 primary ovarian cancer tissue and 4 normal ovarian tissue was used to identify miRNA profiling.
Project description:We hypothesized that the transcriptome of primary cultures of morphologically normal ovarian surface epithelial cells could be altered by the presence of a heterozygous BRCA1 or BRCA2 mutation. We aimed to discover early events associated to ovarian carcinogenesis, which could represent putative targets for preventive strategies of this silent killer tumor. We identified the first molecular signature associated with French Canadian BRCA1 or BRCA2 founder mutations in morphologically normal ovarian epithelial cells. We discovered that wild-type and mutated BRCA2 allelic transcripts were expressed not only in morphologically normal but also in tumor cells from 8765delAG BRCA2 carriers. Further analysis of morphologically normal ovarian and tumor cells from C4446T BRCA1 carriers lead to the same observation. Our data support the idea that one single hit in BRCA1 or BRCA2 is sufficient to alter the transcriptome of phenotypically normal ovarian epithelial cell. The highest level of BRCA2 mutated allele transcript expression was measured in cells originating from the most aggressive ovarian tumor. The penetrance of the mutation and the aggressiveness of the related tumor could depend on a dosage effect of the mutated allele transcript. We studied the molecular profiles associated with 5 a priori classes of samples : 4 non-familial morphologically normal ovarian surface epithelium (NOSEs) : NM class, 2 BRCA1-mutated NOSEs : M1 class, 3 BRCA2-mutated NOSEs : M2 class, 3 BRCA1-mutated ovarian tumor cells (TOVs) : TM1 class and one BRCA2-mutated TOV :TM2 class. No technical replicates were included in this study. The following contrasts were computed : NM vs. M1, NM vs. M2, M1 vs. M2, M1 vs. TM1 and M (M1 union M2) vs. TM (TM1 union TM2).