Effect of dual inhibition of apoptosis and autophagy in prostate cancer

Ahamed Saleem, Dmitri Dvorzhinski, Urmila Santanam, Robin Mathew, Kevin Bray, Mark Stein, Eileen White, Robert S. Dipaola

Research output: Contribution to journalArticlepeer-review

56 Scopus citations

Abstract

PURPOSE Targeting multiple anti-apoptotic proteins is now possible with the small molecule BH3 domain mimetics such as ABT-737. Given recent studies demonstrating that autophagy is a resistance mechanism to multiple therapeutic agents in the setting of apoptotic inhibition, we hypothesized that hydroxychloroquine (HCQ), an anti-malarial drug that inhibits autophagy, will increase cytotoxicity of ABT-737. EXPERIMENTAL DESIGN Cytotoxicity of ABT-737 and HCQ was assessed in vitro in PC-3 and LNCaP cells, and in vivo in a xenograft mouse model. The role of autophagy as a resistance mechanism was assessed by siRNA knockdown of the essential autophagy gene beclin1. ROS was measured by flow cytometry, and mitophagy assessed by the mCherry-Parkin reporter. RESULTS Induction of autophagy by ABT-737 was a mechanism of resistance in prostate cancer cell lines. Therapeutic inhibition of autophagy with HCQ increased cytotoxicity of ABT-737 both in vitro and in vivo. ABT-737 induced LC-3 and decreased p62 expression by immunoblot in cell lines and by immunohistochemistry in tumors in vivo. Assessment of ROS and mitochondria demonstrated that ROS production by ABT-737 and HCQ was a mechanism of cytotoxicity. CONCLUSIONS We demonstrated that autophagy inhibition with HCQ enhances ABT-737 cytotoxicity in vitro and in vivo, that LC-3 and p62 represent assessable markers in human tissue for future clinical trials, and that ROS induction is a mechanism of cytotoxicity. These results support a new paradigm of dual targeting of apoptosis and autophagy in future clinical studies.

Original languageEnglish
Pages (from-to)1374-1381
Number of pages8
JournalProstate
Volume72
Issue number12
DOIs
StatePublished - Sep 1 2012

Keywords

  • ABT-263
  • ABT-737
  • BH3
  • Bcl-2
  • autophagy
  • metabolism
  • prostate cancer

ASJC Scopus subject areas

  • Oncology
  • Urology

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