Withaferin A Induces Cell Death Selectively in Androgen-Independent Prostate Cancer Cells but Not in Normal Fibroblast Cells

PLoS One. 2015 Jul 31;10(7):e0134137. doi: 10.1371/journal.pone.0134137. eCollection 2015.

Abstract

Withaferin A (WA), a major bioactive component of the Indian herb Withania somnifera, induces cell death (apoptosis/necrosis) in multiple types of tumor cells, but the molecular mechanism underlying this cytotoxicity remains elusive. We report here that 2 μM WA induced cell death selectively in androgen-insensitive PC-3 and DU-145 prostate adenocarcinoma cells, whereas its toxicity was less severe in androgen-sensitive LNCaP prostate adenocarcinoma cells and normal human fibroblasts (TIG-1 and KD). WA also killed PC-3 cells in spheroid-forming medium. DNA microarray analysis revealed that WA significantly increased mRNA levels of c-Fos and 11 heat-shock proteins (HSPs) in PC-3 and DU-145, but not in LNCaP and TIG-1. Western analysis revealed increased expression of c-Fos and reduced expression of the anti-apoptotic protein c-FLIP(L). Expression of HSPs such as HSPA6 and Hsp70 was conspicuously elevated; however, because siRNA-mediated depletion of HSF-1, an HSP-inducing transcription factor, reduced PC-3 cell viability, it is likely that these heat-shock genes were involved in protecting against cell death. Moreover, WA induced generation of reactive oxygen species (ROS) in PC-3 and DU-145, but not in normal fibroblasts. Immunocytochemistry and immuno-electron microscopy revealed that WA disrupted the vimentin cytoskeleton, possibly inducing the ROS generation, c-Fos expression and c-FLIP(L) suppression. These observations suggest that multiple events followed by disruption of the vimentin cytoskeleton play pivotal roles in WA-mediated cell death.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Androgens / metabolism*
  • Autophagy
  • Cell Death / drug effects*
  • Cell Line, Tumor
  • Culture Media, Serum-Free
  • Drug Resistance, Neoplasm
  • Endoplasmic Reticulum / drug effects
  • Fibroblasts / cytology
  • Fibroblasts / metabolism
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Male
  • Mitochondria / drug effects
  • Prostatic Neoplasms / metabolism
  • Prostatic Neoplasms / pathology*
  • Proto-Oncogene Proteins c-fos / metabolism
  • Subcellular Fractions / metabolism
  • Up-Regulation
  • Vimentin / metabolism
  • Withanolides / pharmacology*

Substances

  • Androgens
  • Culture Media, Serum-Free
  • Proto-Oncogene Proteins c-fos
  • Vimentin
  • Withanolides
  • withaferin A

Grant support

This work was supported in part by Grants-in-aid for Scientific Research S (No. 15101006), Scientific Research B (No. 20370081 and 23370086) and Exploratory Research (No. 21651085) to H.N. and Scientific Research C (No. 22570185) to N.Y. from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (http://www.mext.go.jp/english/).