Project description:Background: Resistance to platinum-based chemotherapy remains a major impediment in the treatment of serous epithelial ovarian cancer. The objective of this study was to use gene expression profiling to delineate major deregulated pathways and biomarkers associated with the development of intrinsic chemotherapy resistance upon exposure to standard first-line therapy for ovarian cancer. Methods: The study cohort comprised 28 patients divided into two groups based on their varying sensitivity to first-line chemotherapy using progression free survival (PFS) as a surrogate of response. All 28 patients had advanced stage, high-grade serous ovarian cancer, and were treated with the same standard platinum-based chemotherapy. Twelve patient tumors demonstrating relative resistance to platinum chemotherapy corresponding to shorter PFS (< eight months) were compared to sixteen tumors from platinum-sensitive patients (PFS > eighteen months). Whole transcriptome profiling was performed using a Affymetrix high-resolution microarray platform to permit global comparisons of gene expression profiles between tumors from the resistant group and the sensitive group. Results: Microarray data analysis revealed a set of 204 discriminating genes possessing expression levels, which could influence differential chemotherapy response between the two groups. Robust statistical testing was then performed which eliminated a dependence on the normalization algorithm employed, producing a restricted list of differentially regulated genes, and which found IGF1 to be the most strongly differentially expressed gene. Pathway analysis, based on the list of 204 genes, revealed enrichment in genes primarily involved in the IGF1/PI3K/NFκB/ERK gene signalling networks. Conclusions: This study has identified pathway specific prognostic biomarkers possibly underlying a differential chemotherapy response in patients undergoing standard platinum-based treatment of serous epithelial ovarian cancer. Future studies to validate these markers are necessary to apply this knowledge to biomarker-based clinical trials. Total RNA from 12 chemotherapy resistant and 16 sensitive chemotherapy sensitive high-grade serous epithelial ovarian cancer samples was subjected to whole transcriptome profiling using Affymetrix U133 Plus 2.0 arrays

Project description:Background: Resistance to platinum-based chemotherapy remains a major impediment in the treatment of serous epithelial ovarian cancer. The objective of this study was to use gene expression profiling to delineate major deregulated pathways and biomarkers associated with the development of intrinsic chemotherapy resistance upon exposure to standard first-line therapy for ovarian cancer. Methods: The study cohort comprised 28 patients divided into two groups based on their varying sensitivity to first-line chemotherapy using progression free survival (PFS) as a surrogate of response. All 28 patients had advanced stage, high-grade serous ovarian cancer, and were treated with the same standard platinum-based chemotherapy. Twelve patient tumors demonstrating relative resistance to platinum chemotherapy corresponding to shorter PFS (< eight months) were compared to sixteen tumors from platinum-sensitive patients (PFS > eighteen months). Whole transcriptome profiling was performed using a Affymetrix high-resolution microarray platform to permit global comparisons of gene expression profiles between tumors from the resistant group and the sensitive group. Results: Microarray data analysis revealed a set of 204 discriminating genes possessing expression levels, which could influence differential chemotherapy response between the two groups. Robust statistical testing was then performed which eliminated a dependence on the normalization algorithm employed, producing a restricted list of differentially regulated genes, and which found IGF1 to be the most strongly differentially expressed gene. Pathway analysis, based on the list of 204 genes, revealed enrichment in genes primarily involved in the IGF1/PI3K/NFκB/ERK gene signalling networks. Conclusions: This study has identified pathway specific prognostic biomarkers possibly underlying a differential chemotherapy response in patients undergoing standard platinum-based treatment of serous epithelial ovarian cancer. Future studies to validate these markers are necessary to apply this knowledge to biomarker-based clinical trials.

Project description:summary Ovarian cancer is the leading cause of death among gynecologic malignancies. This is partly due to a non-durable response to chemotherapy. Prediction of resistance to chemotherapy could be a key role in more personalized treatment. In the current study we aimed to examine if microRNA based predictors could predict resistance to chemotherapy in ovarian cancer, and to investigate if the predictors could be prognostic factors for progression free and overall survival. Methods Predictors of chemotherapy-resistance were developed based on correlation between miRNA expression and differences in measured growth inhibition in a variety of human cancer cell lines in the presence of Carboplatin, Paclitaxel and Docetaxel (deposited under accession number E-MTAB-327 in the ArrayExpress database of the European Bioinformatics Institute, 2012). These predictors were then, retrospectively, blindly validated in a cohort of 170 epithelial ovarian cancer patients treated with Carboplatin and Paclitaxel or Docetaxel as first line treatment. Results In a multivariate cox proportional analysis the predictors of chemotherapy-resistance were not able to predict time to progression after end of chemotherapy (hazard ratio: 0.64, 95% CI: 0.36 – 1.12, P=0.117). However, in a multivariate logistic analysis, where time to progression was considered as either more or less than 6 months, the predictors match clinical observed chemotherapy-resistance (odds ratio: 0.19, 95% CI: 0.05-0.73, P=0.015). Neither univariate nor multivariate, time-dependent, cox analysis for progression free survival (PFS) or overall survival (OS) in all 170 patients showed to match predicted resistance to chemotherapy (PFS: hazard ratio: 0.69, 95% CI: 0.40-1.19, P=0.183, OS: hazard ratio: 0.76, 95% CI: 0.42-1.40, P=0.386). Conclusion In the current study, microRNA based predictors of chemotherapy-resistance did not demonstrate any convincing correlation to clinical observed chemotherapy-resistance, progression free survival, or overall survival, in patients with epithelial ovarian cancer. However the predictors did reflect relapse more or less than 6 months.

Project description:Changes in chromatin organization are associated with resistance to anti-cancer drugs, such as platinum-based chemotherapy used as the primary treatment of ovarian cancer. We have examined the genomic distribution of chromatin accessibility changes, and relationship to gene expression changes, occurring during acquisition of resistance in vivo of high grade serous ovarian cancer (HGSOC) patients and whether this associates with genomic DNA damage distribution. Using matched chemo-sensitive and chemo-resistant ovarian cell lines isolated from HGSOC patients before and following acquisition of clinical resistance to platinum-based chemotherapy, we have examined the relationship between chromatin accessibility by ATAC-seq, platinum-DNA adduct distribution by Pt-Exo-seq and gene expression by RNA-seq. We have correlated chromatin changes between the lines at gene promoters, CpG islands, enhancer sequences and other genomic regions with changes in gene expression and platinum-DNA adduct distribution. We observe chromatin conformation differences following acquisition of platinum-resistance, with the HGSOC resistant lines clustering together, separately from their respective sensitive counterparts. Resistant lines show altered chromatin accessibility at intergenic regions, but less so at gene promoters. Super-enhancers, as defined by clusters of cis-regulatory elements, at these intergenic regions show chromatin changes that are associated with altered expression of linked genes, with enrichment for genes involved in the Fanconi anemia/BRCA DNA damage response pathway. Genome-wide distribution of platinum adducts associates with the chromatin changes and distinguish sensitive from resistant lines. Regions incurring fewer platinum-adducts showed a significant reduction in accessibility the resistant HGSOC cell line PEO4 compared to the sensitive PEO1 counterpart. Surprisingly, regions showing increased damage in PEO4 had an even greater reduction in accessibility. In the resistant line, we observe fewer adducts around gene promoters and more adducts at intergenic regions. In cell lines derived from patients following acquisition of clinical resistance to platinum-based chemotherapy, chromatin changes at super-enhancers correlate with gene expression changes in DNA repair pathways known to influence platinum sensitivity. Although cisplatin is a relatively non-specific DNA damaging agent, there are consistent differences in distribution of adducts between the matched sensitive and resistant ovarian cell lines, which is independent of the overall level of adducts formed.

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Targeting meiotic recombination 11 (MRE11) nuclease for personalization of epithelial ovarian cancer therapy [2]

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