title: Down-modulation of Bcl-2 sensitizes PTEN-mutated prostate cancer cells to starvation and taxanes.
abstract: BACKGROUND
  The critical role of PTEN in regulating the PI3K/Akt/mTOR signaling pathway raises the possibility that targeting downstream effectors of the PI3K pathway, such as Bcl-2, might be an effective anti-proliferative strategy for PTEN-deficient prostate cancer cells.
  
  
  METHODS
  Four prostate cancer cell lines (LNCaP, PC3, DU145, 22Rv1) were assayed for their levels of total Akt and Ser473 phosphorylated Akt (p-Akt) by Western Blotting; their growth rates and sensitivity to different doses of paclitaxel were determined by cell counts after Trypan Blue dye exclusion assay. Cells were subjected to different combinations of starvation (growth factors and/or aminoacids withdrawal), paclitaxel treatment and Bcl-2 silencing by siRNA. Cell viability was evaluated by Trypan Blue dye exclusion assay, Propidium Iodide (PI) and Annexin-V/PI staining.
  
  
  RESULTS
  We assessed the sensitivity of different prostate cancer cell lines to starvation and we observed a differential response correlated to the levels of Akt activation. The four prostate cancer cell lines also showed different sensitivity to taxol treatments; LNCaP and 22Rv1 cells were more resistant to paclitaxel than DU145 and PC3 cells. Combining taxol with growth factors and aminoacids deprivation leaded to a more than additive reduction of cell viability compared to single treatments in PTEN-mutant LNCaP cells. Down-modulation of anti-apoptotic Bcl-2 protein by siRNA sensitized LNCaP cells to taxanes and starvation induced cell death.
  
  
  CONCLUSIONS
  Silencing Bcl-2 in PTEN-mutated prostate cancer cells enhances the apoptotic effects of combined starvation and taxol treatments, indicating that inhibition of Bcl-2 may be of significant value in PTEN-mutant tumor therapy.
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, Milan, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Calastretti
authors.forename: Giuliana
authors.initials: G
authors.lastname: Gatti
authors.forename: Carolina
authors.initials: C
authors.lastname: Quaresmini
authors.forename: Annamaria
authors.initials: A
authors.lastname: Bevilacqua
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D045744:Cell Line, Tumor; D015536:Down-Regulation; D006801:Humans; D008297:Male; D009154:Mutation; D051059:PTEN Phosphohydrolase / Q000235:genetics* / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D019253:Proto-Oncogene Proteins c-bcl-2; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D017239:Paclitaxel
keywords: Akt; Bcl-2; PTEN; chemosensitization; nutrient starvation; taxanes