Increased Hsp27 after Androgen Ablation Facilitates Androgen-Independent Progression in Prostate Cancer via Signal Transducers and Activators of Transcription 3–Mediated Suppression of Apoptosis

Abstract

One strategy to improve therapies in prostate cancer involves targeting cytoprotective genes activated by androgen withdrawal to delay the emergence of the androgen-independent (AI) phenotype. The objectives of this study were to define changes in Hsp27 levels after androgen ablation and to evaluate the functional relevance of these changes in AI progression. Using a tissue microarray of 232 specimens of hormone-naïve and post-hormone ablation-treated prostate cancer, we found that Hsp27 levels increase after androgen ablation to become highly expressed (>4-fold, P V 0.01) in AI tumors. Hsp27 overexpression rendered LNCaP cells highly resistant to androgen withdrawal both in vitro and in vivo. Tumor volume and serum prostate-specific antigen levels increased 4.3-and 10-fold faster after castration when Hsp27 was overexpressed. Treatment of LNCaP tumor cells in vitro with Hsp27 antisense oligonucleotides (ASO) or shortinterfering RNA suppressed Hsp27 levels in a dose-dependent and sequence-specific manner increased the apoptotic sub-G 0 -G 1 fraction and caspase-3 cleavage >2-fold, as well as decreased signal transducers and activators of transcription 3 (Stat3) levels and its downstream genes, c-fos and sPLA-2. The cytoprotection afforded by Hsp27 overexpression was attenuated by Stat3 knockdown using specific Stat3 ASO. Coimmunoprecipitation and immunofluorescence confirmed that Hsp27 interacts with Stat3 and that Stat3 levels correlated directly with Hsp27 levels. Hsp27 ASO treatment in athymic mice bearing LNCaP tumors significantly delayed LNCaP tumor growth after castration, decreasing mean tumor volume and serum prostate-specific antigen levels by 57% and 69%, respectively. These findings identify Hsp27 as a modulator of Stat3-regulated apoptosis after androgen ablation and as a potential therapeutic target in advanced prostate cancer. (Cancer Res 2005; 65(23): 11083-93)

Hsp27 knockdown using nucleotide-based therapies inhibit tumor growth and enhance chemotherapy in human bladder cancer cells

“…Collectively, these findings show that Hsp27 helps mediate bladder cancer progression and development of treatment resistance to cytotoxic chemotherapy. The response to OGX-427 in UMUC-3 cells are similar to our previous reports of Hsp27 knockdown in LNCaP and PC-3 prostate cancer cell lines (18,37). In these studies, OGX-427 enhanced the in vivo effects of castration-induced regression to delay androgen-independent LNCaP and PC-3 tumor growth and also enhances chemotherapy in vivo, emphasizing the additive role this ASO has in combination therapy regimes.…”

“…Hsp27 can exert its antiapoptotic effects through the enhancement of nuclear factor-nB activity, by facilitating proteasomal degradation of its main inhibitor I-nB (36). Finally, we recently reported that Hsp27 interacts with and increases signal transducers and activators of transcription 3 levels and activity, a relevant transcription factor in many cancers, identifying yet another cytoprotective mechanism OGX-427 Down-regulation of Hsp27 in Bladder Cancer mediated by Hsp27 (37). Thus, Hsp27 is an attractive therapeutic target because its inhibition would affect multiple different pathways implicated in cancer cell survival and resistance as opposed to targeting a single pathway.…”

IL‐12, IL‐23, and IL‐27 enhance human β‐defensin‐2 production in human keratinocytes

“…Antisense oligonucleotides against NF-jB p50, NF-jB p65, STAT1, STAT3, and control scrambled oligonucleotides were synthesized by phosphoroamidite chemistry, as described previously [42,47,48]. The keratinocytes were transfected with the indicated oligonucleotides (each 0.2 lM) premixed with Fugene 6 in KGM for 6 h. The cells were treated with high-calcium KBM for 48 h, and then incubated with 10 ng/mL IL-1b and/or the indicated concentrations of IL-12, IL-23, or IL-27.…”

The Complex Role of AR Signaling After Cytotoxic Insult: Implications for Cell Cycle Based Chemotherapeutics

“…For example, protection from apoptotic stress can be elicited through AR-dependent induction of heat shock protein 27 (HSP27) phosphorylation, or via expression of the protease ADAM9. 60,61 In addition, AR is known to directly induce activation of the clusterin locus, which encodes a molecular chaperone whose actions can be either cytoprotective or pro-apoptotic, dependent on the isoform induced. Specifically, androgen induces expression of the cytoprotective isoform 2, yet downregulates isoform 1 expression.…”