Autophagy, a cellular self-eating process that is activated by several cancer drugs and appears to function as a protective mechanism, is a promising therapeutic target. Pancreatic ductal adenocarcinoma (PDAC) is highly resistant to chemotherapy, and has been described as requiring elevated autophagy for growth. To date, all preclinical reports and clinical trials investigating pharmacological inhibition of autophagy have used chloroquine or hydroxychloroquine, which block autophagy at a late stage. Verteporfin is a newly discovered autophagy inhibitor that blocks autophagy at an early stage by inhibiting autophagosome formation. Here, we report that PDAC cell lines show variable sensitivity to verteporfin in vitro and that verteporfin inhibits autophagy stimulated by gemcitabine, the current standard treatment for PDAC. Pharmacokinetic and efficacy studies in a BxPC-3 xenograft mouse model demonstrate that verteporfin accumulated in tumors at autophagy-inhibiting levels but did not reduce tumor volume or increase survival as a single agent. However, in combination with gemcitabine, verteporfin moderately reduced tumor growth and enhanced survival compared to gemcitabine alone. Our results do not agree with the premise that autophagy inhibition is effective against PDAC as a single-modality treatment, but they support autophagy inhibition as an approach to sensitize PDAC to gemcitabine.
Citation Format: Elizabeth Donohue, Anitha Thomas, Norbert Maurer, Irina Manisali, Magali Zeisser-Labouebe, Natalia Zisman, Hilary J. Anderson, Murray Webb, Marcel Bally, and Michel Roberge. The early autophagy inhibitor verteporfin moderately enhances the antitumor activity of gemcitabine in a pancreatic ductal adenocarcinoma model. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B11.