Poly(adenosine diphosphate ribose) polymerase inhibitors induce autophagy‐mediated drug resistance in ovarian cancer cells, xenografts, and patient‐derived xenograft models

Abstract

BACKGROUND: Poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors exhibit promising activity against ovarian cancers, but their efficacy can be limited by acquired drug resistance. This study explores the role of autophagy in regulating the sensitivity of ovarian cancer cells to PARP inhibitors. METHODS: Induction of autophagy was detected by punctate LC3 fluorescence staining, LC3I to LC3II conversion on Western blot analysis, and electron microscopy. Enhanced growth inhibition and apoptosis were observed when PARP inhibitors were used with hydroxychloroquine, chloroquine (CQ), or LYS05 to block the hydrolysis of proteins and lipids in autophagosomes or with small interfering RNA against ATG5 or ATG7 to prevent the formation of autophagosomes. The preclinical efficacy of the combination of CQ and olaparib was evaluated with a patient-derived xenograft (PDX) and the OVCAR8 human ovarian cancer cell line. RESULTS: Four PARP inhibitors (olaparib, niraparib, rucaparib, and talazoparib) induced autophagy in a panel of ovarian cancer cells. Inhibition of autophagy with CQ enhanced the sensitivity of ovarian cancer cells to PARP inhibitors. In vivo, olaparib and CQ produced additive growth inhibition in OVCAR8 xenografts and a PDX. Olaparib inhibited PARP activity, and this led to increased reactive oxygen species (ROS) and an accumulation of γ-H2AX. Inhibition of autophagy also increased ROS and γ-H2AX and enhanced the effect of olaparib on both entities. Treatment with olaparib increased phosphorylation of ATM and PTEN while decreasing the phosphorylation of AKT and mTOR and inducing autophagy. CONCLUSIONS: PARP inhibitor-induced autophagy provides an adaptive mechanism of resistance to PARP inhibitors in cancer cells with wild-type BRCA, and a combination of PARP inhibitors with CQ or other autophagy inhibitors could improve outcomes for patients with ovarian cancer. Cancer 2020;126:894-907.

Drugs Targeting Tumor-Initiating Cells Prolong Survival in a Post-Surgery, Post-Chemotherapy Ovarian Cancer Relapse Model

“…In this study we sought to identify strategies for this OC patient population that could be used in the setting of first remission, with the goal of eradicating putative TICs and preventing relapse. We used OC cell lines that form spheres, have been reported to be resistant to platinum and PARP inhibitors, and do not carry BRCA mutations: OV90, OVCAR8 and CAOV3 [ 37 , 45 , 46 ]. We showed the efficacy of these drugs in models of relapse after chemotherapy treatment in vitro and in vivo for their ability to prolong survival.…”

Synthesis and Biological Evaluation of HDAC Inhibitors With a Novel Zinc Binding Group

“…Cancers with increasing incidence and mortality have been the leading cause of death, seriously threating the public health and making the design and discovery of chemotherapeutic agents particularly important (Evans et al, 2017). Although substantial progress has been made in the antitumor drugs, drug resistance and high toxicity limit their clinical application (Hughes and Andersson, 2015;Yan and Li, 2018;Santiago-O'farrill et al, 2019). In addition, various factors are involved the development of the tumorigenesis, especially the changes in gene expression associated with mutation, loss, and rearrangement, making the mechanism much more complicated (Wenbo and Wang, 2017).…”

The Application of Patient-Derived Xenograft Models in Gynecologic Cancers

“…Consistently, it was identified that combined use of PARPi and ATR/CHK1 inhibitor exhibited a more effective antitumor activity than PARPi monotherapy in the established recurrent BRCA-mutant (BRCAMUT) HGS-OC PDX models [66]. Whilst, olaparib and chloroquine (CQ) were shown to induce synergistic antitumor activity and promoted drug resistance via autophagy in ovarian cancer PDX models [67]. In contrast, AlHilli et al [68] developed five homologous recombination deficiency HGS-OC PDX models intraperitoneally in 35 female SCID mice to evaluate the antitumor role of niraparib, and found that niraparib monotherapy in one of two PDX models with deficient BRCA2 and in one PDX with Rad51C promoter methylation induced cancer regression, although these models were failed to promote response to carboplatin/paclitaxel chemotherapy.…”