Inhibitory member of the apoptosis-stimulating protein of p53 (ASPP) family promotes growth and tumorigenesis in human p53-deficient prostate cancer cells

iASPP is a member of the apoptosis-stimulating protein of p53 (ASPP) family and an evolutionarily conserved inhibitor of p53. Higher levels of iASPP proteins were examined in paraffin-embedded sections collected from 30 patients with prostate cancer using an immunohistochemical method. We found that specially knocking down iASPP with lentivirus-mediated small interfering RNA inhibited the growth, in vitro colony-forming capacity and in vivo tumorigenesis of p53-defective prostate cancer cells. Importantly, inhibition of iASPP induced cell apoptosis, which confers the inhibitory effect on cell survival. We conclude that iASPP is essential for prostate cancer cellular proliferation and survival and may be a potential target for the gene therapy for prostate cancer.