Combination of chloroquine and GX15-070 (obatoclax) results in synergistic cytotoxicity against pancreatic cancer cells

Oncol Rep. 2014 Dec;32(6):2789-94. doi: 10.3892/or.2014.3525. Epub 2014 Oct 3.

Abstract

Pancreatic cancer is an aggressive disease with a poor prognosis. Therefore, new treatment is urgently required. GX15-070 is a pan-Bcl-2 inhibitor which has shown promising antitumor activity in different malignancies. We previously demonstrated that clinically achievable concentrations of GX15-070 caused growth arrest in pancreatic cancer cell lines. However, they only induced minimal levels of apoptosis. We hypothesized that GX15-070 induced autophagy in pancreatic cancer cells which blocked apoptosis. In this study, we investigated the effects of GX15-070 on autophagy and the antitumor activities of the combination of GX15-070 and chloroquine (CQ), an autophagy inhibitor, in six pancreatic cancer cell lines. We found that GX15-070 treatment indeed induced autophagy in 5 of the 6 pancreatic cancer cell lines, reflected by the conversion of LC3B-I to LC3B-II and detection of autophagosomes by transmission electron microscopy. Furthermore, we found additive to synergistic antitumor interactions in all six cell lines by MTT assays. CQ significantly enhanced GX15-070-induced apoptosis in the cell line models, possibly due to downregulation of Bcl-2, Bcl-xL and Mcl-1 in the cells by the two agents. These results provide compelling evidence for the further development of the combination of GX15-070 and CQ in pancreatic cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Combined Chemotherapy Protocols / administration & dosage
  • Apoptosis / drug effects
  • Autophagy / drug effects
  • Cell Line, Tumor
  • Chloroquine / administration & dosage*
  • Drug Synergism*
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Indoles
  • Myeloid Cell Leukemia Sequence 1 Protein / biosynthesis
  • Pancreatic Neoplasms / drug therapy*
  • Pancreatic Neoplasms / genetics
  • Pancreatic Neoplasms / pathology
  • Proto-Oncogene Proteins c-bcl-2 / biosynthesis
  • Pyrroles / administration & dosage*
  • bcl-X Protein / biosynthesis

Substances

  • BCL2L1 protein, human
  • Indoles
  • MCL1 protein, human
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Proto-Oncogene Proteins c-bcl-2
  • Pyrroles
  • bcl-X Protein
  • Chloroquine
  • obatoclax