Abstract 1236: In vitro association of chloroquine with alkylating and antimicrotubule agents in patient derived cell lines of glioblastoma

Abstract

Abstract Autophagy is an important mechanism for cell survival after chemotherapy treatment. Many preclinical and clinical trials have tried to achieve tumor remission combining alkylating agents with autophagy inhibition. Chloroquine (CQ) has a long record as an autophagy inhibitor. In previous studies it was administered in vitro with mixed effects on central nervous system cell lines: while high doses of CQ were cytotoxic, low doses were neuroprotective. Preclinical studies showed that CQ could be used to treat glioblastoma, tumors derived from glial cells in the brain. In a phase I/II clinical trial combining CQ with the standard alkylating agent (temozolomide) plus radiotherapy treating patients with glioblastoma, a dose-limiting toxicity was observed at high doses. Although the authors reported that autophagy inhibition could not be achieved, they did not describe if this mechanism was involved in tumor resistance in that cohort of patients. In order to clarify if CQ can be used to block autophagy, we performed long term treatment combining low doses of CQ with chemotherapeutic agents. We used patient derived cell lines (PDCL) from glioblastoma tumors and treated them with therapeutic agents, using the reported plasma concentration of each drug. We measured acidic organelles with acridine orange incorporation 3, 5 and 7 days after addition of the treatment with flow cytometry. Additionally, 7 days after treatment surviving cells were counted. We did not observe significant increase in autophagy levels or decrease in cell number after temozolomide treatment. On the contrary, paclitaxel induced autophagy and decreased cell survival. Interestingly the combination of procarbazine, lomustine and vincristine (PCV), induced a broad range of results, ranging from high autophagy to increased cell death. We decided to combine PCV with CQ and perform long term analysis in order to evaluate the ability of cells undergoing or escaping apoptosis, senescence or mitotic catastrophe. After 5 days nuclear morphometric analysis demonstrated that out of 6 PDCL tested, only one presented an increase in senescence. The same PDCL also presented a decrease in total number of cells and increase in p62, although combining CQ with PCV was not better than PCV alone. Our results in vitro, using low concentrations of CQ corroborate the finding in clinical trials that chloroquine does not eliminate malignant cells in glioblastoma and better autophagy inhibitors need to be developed to achieve this goal. Citation Format: Franciele C. Kipper, Ajith Thomas, Guido Lenz. In vitro association of chloroquine with alkylating and antimicrotubule agents in patient derived cell lines of glioblastoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1236.