Project description:Epigenetic changes, particularly DNA methylation aberrations have been implicated in acquired resistance to platinum in ovarian cancer. A multi-institutional randomized clinical trial compared a regimen of a DNA methyl transferase (DNMT) inhibitor guadecitabine and carboplatin to physician’s choice chemotherapy for patients with recurrent platinum resistant ovarian cancer. Tumor biopsies or malignant ascites were collected at day 1 of cycle 1 (pre-guadecitabine) and after two cycles of treatment (post-decitabine). The goal of the current study was to analyze guadecitabine-induced DNA methylation and gene expression changes and correlate pretreatment levels with clinical outcomes. Epigenomic and transcriptomic profiling using the Infinium HumanMethylation450 BeadChip (HM450) and RNA sequencing revealed extensive methylation and gene expression changes induced by guadecitabine in ovarian tumors. Ninety-four gene promoters were significantly hypomethylated after treatment with guadecitabine and 949 genes were differentially expressed in pre vs. post-treatment tumors. Pathways associated with immune reactivation and DNA repair were significantly altered by guadecitabine treatment. Expression levels of 1155 genes involved in 25 networks on day 1 of cycle 1 correlated with progression free survival. Increased expression of selected genes (e.g. DOK2, miR193a) silenced through promoter methylation restored platinum sensitivity in ovarian cancer cells. Together, these results support that guadecitabine altered DNA methylation and expression of genes and gene networks correlate with re-sensitization to carboplatin in ovarian cancer patients.
Project description:Epigenetic changes, particularly DNA methylation aberrations have been implicated in acquired resistance to platinum in ovarian cancer. A multi-institutional randomized clinical trial compared a regimen of a DNA methyl transferase (DNMT) inhibitor guadecitabine and carboplatin to physician’s choice chemotherapy for patients with recurrent platinum resistant ovarian cancer. Tumor biopsies or malignant ascites were collected at day 1 of cycle 1 (pre-guadecitabine) and after two cycles of treatment (post-decitabine). The goal of the current study was to analyze guadecitabine-induced DNA methylation and gene expression changes and correlate pretreatment levels with clinical outcomes. Epigenomic and transcriptomic profiling using the Infinium HumanMethylation450 BeadChip (HM450) and RNA sequencing revealed extensive methylation and gene expression changes induced by guadecitabine in ovarian tumors. Ninety-four gene promoters were significantly hypomethylated after treatment with guadecitabine and 949 genes were differentially expressed in pre vs. post-treatment tumors. Pathways associated with immune reactivation and DNA repair were significantly altered by guadecitabine treatment. Expression levels of 1155 genes involved in 25 networks on day 1 of cycle 1 correlated with progression free survival. Increased expression of selected genes (e.g. DOK2, miR193a) silenced through promoter methylation restored platinum sensitivity in ovarian cancer cells. Together, these results support that guadecitabine altered DNA methylation and expression of genes and gene networks correlate with re-sensitization to carboplatin in ovarian cancer patients.
Project description:DNA repair competency is one determinant of sensitivity to certain chemotherapy drugs, such as cisplatin. Cancer cells with intact DNA repair can avoid the accumulation of genome damage during growth and also can repair platinum-induced DNA damage. We sought genomic signatures indicative of defective DNA repair in cell lines and tumors and correlated these signatures to platinum sensitivity. The number of subchromosomal regions with allelic imbalance extending to the telomere (NtAI) predicted cisplatin sensitivity in vitro and pathologic response to preoperative cisplatin treatment in patients with triple-negative breast cancer (TNBC). In serous ovarian cancer treated with platinum-based chemotherapy, higher levels of NtAI forecast a better initial response. We found an inverse relationship between BRCA1 expression and NtAI in sporadic TNBC and serous ovarian cancers without BRCA1 or BRCA2 mutation. Thus, accumulation of telomeric allelic imbalance is a marker of platinum sensitivity and suggests impaired DNA repair.
Project description:Platinum resistance is a clinical challenge in ovarian cancer. Platinating agents induce DNA damage which activate Mre11 nuclease directed DNA damage signalling and response (DDR). Upregulation of DDR may promote chemotherapy resistance. Here we have comprehensively evaluated Mre11 in epithelial ovarian cancers. In clinical cohort that received platinum- based chemotherapy (n=331), Mre11 protein overexpression was associated with aggressive phenotype and poor progression free survival (PFS) (p=0.002). In the ovarian cancer genome atlas (TCGA) cohort (n=498), Mre11 gene amplification was observed in a subset of serous tumours (5%) which correlated highly with Mre11 mRNA levels (p<0.0001). Altered Mre11 levels was linked with genome wide alterations that can influence platinum sensitivity. At the transcriptomic level (n=1259), Mre11 overexpression was associated with poor PFS (p=0.003). ROC analysis showed an area under the curve (AUC) of 0.642 for response to platinum-based chemotherapy. Pre-clinically, Mre11 depletion by gene knock down or blockade by small molecule inhibitor (Mirin) reversed platinum resistance in ovarian cancer cells and in 3D spheroid models. Importantly, Mre11 inhibition was synthetically lethal in platinum sensitive XRCC1 deficient ovarian cancer cells and 3D-spheroids. Selective cytotoxicity was associated with DNA double strand break (DSB) accumulation, S-phase cell cycle arrest and increased apoptosis. We conclude that pharmaceutical development of Mre11 inhibitors is a viable clinical strategy for platinum sensitization and synthetic lethality in ovarian cancer.
Project description:Platinum resistance is a clinical challenge in ovarian cancer. Platinating agents induce DNA damage which activate Mre11 nuclease directed DNA damage signalling and response (DDR). Upregulation of DDR may promote chemotherapy resistance. Here we have comprehensively evaluated Mre11 in epithelial ovarian cancers. In clinical cohort that received platinum- based chemotherapy (n=331), Mre11 protein overexpression was associated with aggressive phenotype and poor progression free survival (PFS) (p=0.002). In the ovarian cancer genome atlas (TCGA) cohort (n=498), Mre11 gene amplification was observed in a subset of serous tumours (5%) which correlated highly with Mre11 mRNA levels (p<0.0001). Altered Mre11 levels was linked with genome wide alterations that can influence platinum sensitivity. At the transcriptomic level (n=1259), Mre11 overexpression was associated with poor PFS (p=0.003). ROC analysis showed an area under the curve (AUC) of 0.642 for response to platinum-based chemotherapy. Pre-clinically, Mre11 depletion by gene knock down or blockade by small molecule inhibitor (Mirin) reversed platinum resistance in ovarian cancer cells and in 3D spheroid models. Importantly, Mre11 inhibition was synthetically lethal in platinum sensitive XRCC1 deficient ovarian cancer cells and 3D-spheroids. Selective cytotoxicity was associated with DNA double strand break (DSB) accumulation, S-phase cell cycle arrest and increased apoptosis. We conclude that pharmaceutical development of Mre11 inhibitors is a viable clinical strategy for platinum sensitization and synthetic lethality in ovarian cancer.
Project description:DNA repair competency is one determinant of sensitivity to certain chemotherapy drugs, such as cisplatin. Cancer cells with intact DNA repair can avoid the accumulation of genome damage during growth and also can repair platinum-induced DNA damage. We sought genomic signatures indicative of defective DNA repair in cell lines and tumors and correlated these signatures to platinum sensitivity. The number of subchromosomal regions with allelic imbalance extending to the telomere (NtAI) predicted cisplatin sensitivity in vitro and pathologic response to preoperative cisplatin treatment in patients with triple-negative breast cancer (TNBC). In serous ovarian cancer treated with platinum-based chemotherapy, higher levels of NtAI forecast a better initial response. We found an inverse relationship between BRCA1 expression and NtAI in sporadic TNBC and serous ovarian cancers without BRCA1 or BRCA2 mutation. Thus, accumulation of telomeric allelic imbalance is a marker of platinum sensitivity and suggests impaired DNA repair. SNP data from 27 and 40 primary triple negative breast cancer tumor samples from two clinical trials treated with cisplatin and cisplatin + bevacizumab. Labeling, hybridization and data processing was performed by Affymetrix using 70k MIP arrays and 330k MIP arrays. In the cisplatin trial, matched normal samples based on blood from all patients and an additional three samples based on FFPE negative lymph nodes were used as references (30 normal references in total). In the cisplatin+bevacizumab trial, mathed normal samples based on blood from 10 patients were used as references.
Project description:Ovarian cancer (OC) is the leading cause of death from gynecologic malignancies. The most difficult issue in the treatment of ovarian cancer is the eventual development of platinum resistance. Accumulating studies have shown that circRNAs are abnormally aberrantly expressed in tumors and play critical roles in tumor growth, metastasis, stemness and resistance to therapy.To identify circRNAs that play crucial roles in maintaining the platinum resistance of ovarian cacner, we performed RNA-seq analysis in platinum-resistant(n=9) and -sensitive(n=10) ovarian cacner tissues. Candidate genes were identified by bioinformatic analysis and literature review.