Project description:Poly (ADP-ribose) Polymerase (PARP) inhibitors (PARPi) are approved to treat recurrent ovarian cancer with BRCA1 or BRCA2 mutations, and as maintenance therapy for recurrent platinum sensitive ovarian cancer (BRCA wild-type or mutated) after treatment with platinum. However, the acquired resistance against PARPi remains a clinical hurdle. Our previous study has demonstrated that PARPi can enhance the Aldehyde dehydrogenase (ALDH) activity in ovarian cancer cells, mainly through inducing expression of ALDH1A1, an isoform of the ALDH family. In addition, an ALDH1A1 selective inhibitor can synergize with olaparib in killing EOC cells carrying BRCA2 mutation in both in vitro cell culture and the in vivo xenograft animal model. In order to elucidating the mechanism by which ALDH1A1 renders PARPi resistance to ovarian cancer, we performed RNA-seq analysis to identify genes whose expression can be regulated by ALDH1A1.
Project description:We have previously established an in vitro model of PARPi-resistant ovarian cancer by long-term exposure of UWB1.289 ovarian cancer cells (and their isogenic derivatives UWB1.289+BRCA1) to incrementally ascending olaparib concentrations. After finalizing this model, we performed RNA-seq, in order to identify differentially expressed transcript in the PARPi-resistant cells, with a focus on genes related to DNA-repair, multi-drug resistance and EMT. As a result, we show that the phenotype of PARPi resistance is associated with EMT-like traits and up-regulation of selective multi-drug related transcripts.
Project description:Cancer-associated fibroblasts (CAFs) play significant roles in drug resistance through different ways. Antitumor therapies, including molecular targeted interventions, not only effect tumor cells but also modulate the phenotype and characteristics of CAFs, which can in turn blunt the therapeutic response. Little is known about how stromal fibroblasts respond to poly (ADP-ribose) polymerase inhibitors (PARPis) in ovarian cancer (OC) and subsequent effects on tumor cells. This is a study to evaluate how CAFs react to PARPis and their potential influence on PARPi resistance in OC. We discovered that OC stromal fibroblasts exhibited intrinsic resistance to PARPis and were further activated after the administration of PARPis. PARPi-challenged fibroblasts displayed a specific secretory profile characterized by increased secretion of CCL5, MIP-3α, MCP3, CCL11, and ENA-78. Mechanistically, increased secretion of CCL5 through activation of the NF-κB signaling pathway was required for PARPi-induced stromal fibroblast activation in an autocrine manner. Moreover, neutralizing CCL5 partly reversed PARPi-induced fibroblast activation and boosted the tumor inhibitory effect of PARPis in both BRCA1/2-mutant and BRCA1/2-wild type xenograft models. Our study revealed that PARPis could maintain and improve stromal fibroblast activation involving CCL5 autocrine upregulation. Targeting CCL5 might offer a new treatment modality in overcoming the reality of PARPi resistance in OC.
Project description:Ovarian cancer (OC) is the leading cause of death from gynecologic malignancies in the US. Ovarian cancer stem cells (OCSCs) have been shown to drive chemoresistance and tumor progression but the mechanism remains incompletely understood. Aldehyde Dehydrogenase 1A1 (ALDH1A1) is a robust marker for cancer stem cells in ovarian and other cancers. We demonstrate that ALDH1A1 inhibition suppresses stemness, chemoresistance and senescence in ovarian cancer.
Project description:Spheroids are 3D multi-cell aggregates formed in non-addherent culture conditions. In ovarian cancer (OC), they serve as a vehicle for cancer cell dissemination in the peritoneal cavity. We investigated genes and networks upregulated in three dimensional (3D) versus two-dimensional (2D) culture conditions by Affymetrix gene expression profiling and identified ALDH1A1, a cancer stem cell marker as being upregulated in OC spheroids. Network analysis confirmed ALDH1A1 upregulation in spheroids in direct connection with elements of the beta-catenin pathway. A parallel increase in the expression levels of beta-catenin and ALDH1A1 was demonstrated in spheroids vs. monolayers an in successive spheroid generations by using OC cell liness and primary OC cells. The percentage of Aldefluor positive cells was significantly higher in spheroids vs. monolayers in IGROV1, A2780, SKOV3, and primary OC cells. B-catenin knock-down decreased ALDH1A1 expression and chromatin immunoprecipitation demonstrated that beta-catenin directly binds to the ALDH1A1 promoter. Both siRNA mediated beta-catenin knock-down and a novel ALDH1A1 small molecule enzymatic inhibitor described here for the first time, decreased the number of OC spheroids (p<0.001) and cell viability. These data strongly support the role of beta-catenin regulated ALDH1A1 in the maintenance of OC spheroids and of a stem cell phenotype and propose new ALDH1A1 inhibitors targeting this cell population. Different gene profiles were observed in ovarian cancer spheroids versus ovarian cancer monolayers. Nine samples were analyzed in triplicate. Each group is a reference.
Project description:PARP inhibitor olaparib induces the formation of polyploid giant cancer cells (PGCCs) in ovarian and breast cancer cell lines, human high-grade serous ovarian cancer (HGSC)–derived organoids, and HGSC patient-derived xenografts (PDXs). Time-lapse tracking of ovarian cancer cells revealed that PGCCs primarily developed from endoreplication of cancer cells after exposure to sublethal concentrations of olaparib. PGCCs exhibited features of senescent cells but, after olaparib withdrawal, could escape senescence via restitutional multipolar endomitosis and other modes of cell division to generate mitotically competent resistant daughter cells. The contraceptive drug mifepristone blocked PGCC formation and daughter cell production. Mifepristone/olaparib combination therapy substantially reduced tumor growth in PDX models without previous olaparib exposure, while mifepristone alone decreased tumor growth in PDX models with acquired olaparib resistance. Thus, targeting PGCCs may represent a promising approach to potentiate the therapeutic response to PARPi and overcome PARPi-induced resistance.
Project description:Chemical modifications of RNAs have emerged as a new layer of epigenetic gene regulation. N6-methyladenosine (m6A) is the most abundant chemical modification of messenger RNA (mRNA). The m6A modification affects RNA fate and functions such as RNA stability. Despite the high initial response rates to PARP inhibitors in BRCA1/2-mutated epithelial ovarian cancers (EOC), PARP inhibitor (PARPi) resistance remains a major challenge. The role of m6A modification in PARPi resistance has not previously been explored. Here we show that m6A modification of FZD10 mRNA contributes to PARPi resistance by upregulating the Wnt/-catenin pathway in BRCA-mutated EOC cells. Global m6A profile reveals a significant increase in m6A modification in FZD10 mRNA. This correlates with an increase in FZD10 mRNA stability and an upregulation of the Wnt/-catenin pathway in PARPi resistant cells. FZD10 knockdown or inhibition of the Wnt/-catenin sensitizes the resistant cells to PARPi. Mechanistically, downregulation of m6A demethylases FTO and ALKBH5 is sufficient to increase FZD10 mRNA m6A modification and reduce PARPi sensitivity, which correlates with an increase in homologous recombination activity. Moreover, PAPRi and Wnt/-catenin inhibitor showed synergistic suppression of growth of PAPRi resistant cells both in vitro and in vivo in a xenograft ovarian cancer mouse model. Our results show that m6A contributes to PAPRi resistance in BRCA-deficient EOC cells by upregulating the Wnt/-catenin pathway through stabilizing FZD10. They also suggest that inhibition of Wnt/-catenin pathway represents a potential strategy to overcome PARPi resistance.