Poly(adenosine diphosphate ribose) polymerase inhibitors induce autophagy‐mediated drug resistance in ovarian cancer cells, xenografts, and patient‐derived xenograft models. Issue 4 (12th November 2019)

• Record Type: Journal Article
• Authors: Santiago‐O'Farrill, Janice M.; Weroha, S. John; Hou, Xiaonan; Oberg, Ann L.; Heinzen, Ethan P.; Maurer, Matthew J.; Pang, Lan; Rask, Philip; Amaravadi, Ravi K.; Becker, Sarah E.; Romero, Ignacio; Rubio, Ma Jesús; Matias‐Guiu, Xavier; Santacana, Maria; Llombart‐Cussac, Antonio; Poveda, Andrés; Lu, Zhen; Bast, Robert C.
• Is Part Of: Cancer. Volume 126:Issue 4(2020)
• Page Start: 894
• Page End: 907
• Publication Date: 2019-11-12
• Subjects: autophagy -- ovarian cancer -- poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors -- resistance; Cancer -- Periodicals; Cancer -- Cytopathology -- Periodicals; 616.99405
• DOI: 10.1002/cncr.32600
• Languages: English
• ISSNs: 0008-543X

Abstract

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. Abstract : The data presented in this article show that poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors induce autophagy in 6 BRCA wild‐type ovarian cancer cells, which provides an adaptive mechanism of drug resistance. A combination of PARP inhibitors and autophagy inhibitors can overcome resistance and improve survival in different experimental models of ovarian cancer. These findings provide evidence of unique combinations of therapy for improving drug therapeutic efficacy, decreasing resistance, and extending the use of PARP inhibitors in the clinic.