Prostate cancer screening

Hsp27 promotes insulin-like growth factor-I survival signaling in prostate cancer via p90Rsk-dependent phosphorylation and inactivation of BAD

Hsp27 is highly expressed in castrate-resistant prostate cancer. Although its overexpression confers resistance to androgen ablation and chemotherapy, the mechanisms by which Hsp27 inhibits treatment-induced apoptosis are incompletely defined. Castrate-resistance often correlates with increased activity of autocrine and/or paracrine growth/survival stimulatory loops including the mitogen-activated protein kinase (MAPK) and Akt pathways and insulin-like growth factor (IGF) axis components. Because Hsp27 can be activated by both MAPK and Akt pathways, it is possible that interactions between IGF-I signaling and Hsp27 phosphoactivation function to promote castrate-resistant progression. Here, we report that Hsp27 expression and phosphorylation levels correlate with IGF-I signaling and castrate-resistant progression in human prostate cancer specimens and cell lines. IGF-I induces Hsp27 phosphorylation in a time- and dose-dependent manner via p90Rsk, which interacts directly with and phosphorylates Hsp27 in vitro and in vivo. Conversely, p90Rsk inhibition using short interfering RNA or a dominant negative mutant abolishes IGF-I-induced Hsp27 phosphorylation. Hsp27 overexpression increases IGF-I-induced phosphorylation of Erk, p90Rsk, and Akt. Conversely, Hsp27 knockdown abrogates IGF-I-induced phosphorylation of Erk, p90Rsk, and Akt, thereby destabilizing Bad/14-3-3 complexes and increasing apoptotic rates. These data elucidate the interactions between Hsp27 phosphorylation and the IGF-I receptor signaling pathway and support targeting Hsp27 as a therapeutic strategy for castrate-resistant prostate cancer.

Effect of the Synthetic Retinoid Fenretinide on Circulating Free Prostate-Specific Antigen, Insulin-Like Growth Factor-I, and Insulin-Like Growth Factor Binding Protein-3 Levels in Men with Superficial Bladder Cancer

PURPOSE

Fenretinide (4-HPR) is a synthetic retinoid that has shown a preventive activity in prostate cancer animal models.

EXPERIMENTAL DESIGN

We measured the changes in total and free prostate-specific antigen (PSA) and its association with insulin-like growth factor I (IGF-I) and IGFBP-3 levels after 1 year of treatment in 24 subjects given 4-HPR and 24 control subjects enrolled in a randomized bladder cancer prevention trial.

RESULTS

No significant effect of 4-HPR was observed on total and free fraction of PSA levels. The median percentage [95 confidence interval (95% CI)] change for % free PSA and total PSA in the 4-HPR and the control group were, respectively, 7.6 (95% CI, -4.0 to 69.3) versus 5.1 (95% CI, -21.4 to 59.8) and -7.8 (95% CI, -18.2 to 52.5) versus -12.3 (95% CI, -44.6 to 9.6). However, in patients ages <60 years, there was a trend to an increase of total free PSA and % free PSA after treatment with 4-HPR that was different from a trend to a decrease in the control group (P = 0.002 and 0.052, respectively). The interaction between age and treatment was statistically significant on free PSA (P = 0.001). A similar pattern was noted with smoking status (P = 0.011 for the interaction on free PSA). No association was observed between PSA levels and IGF-I or IGFBP-3 levels.

CONCLUSIONS

We conclude that 4-HPR has no significant effect on circulating PSA, but it increases significantly free PSA levels in subjects younger than 60 years and in nonsmokers. These effects might support an activity in prostate cancer prevention but further studies are required.

Vitamin E and the Y4 agonist BA-129 decrease prostate cancer growth and production of vascular endothelial growth factor

BACKGROUND

A biologically active form of vitamin E, alpha-tocopherol succinate (ATS), has been shown to induce apoptosis of hormone-refractory prostate cancer in vitro and inhibit cell growth in vivo. The gastrointestinal hormone peptide YY (PYY) has growth inhibitory activity against multiple cancer cell lines and is synergistic with ATS against breast and pancreatic cancer growth. BA-129, a specific Y4 receptor agonist, has growth inhibitory effects on pancreatic cancer in vitro. We investigated the effects of BA-129 and ATS on prostate cancer growth and evaluated their effects on vascular endothelial growth factor (VEGF) production.

METHODS

A hormone-refractory human prostate cancer cell line, PC-3, was treated with ATS alone at 10 pg/ml, PYY or BA-129 alone at doses of 75 and 500 pmol/ml, or a combination of the two agents. Cell growth was measured by MTT assay and hemocytometry using trypan blue. Quantitative measurement of VEGF was performed by ELISA. Statistical analysis was achieved by ANOVA.

RESULTS

ATS exhibited significant (P < 0.05) growth inhibitory effects in prostate cancer cells. PYY also inhibited growth (P < 0.05). ATS treatment reduced VEGF production (P < 0.05). PYY treatment increased VEGF. When ATS was given in combination with BA-129, VEGF production was further reduced (P < 0.05).

CONCLUSIONS

Both PYY and ATS inhibit growth in hormone-refractory prostate cancer, with augmentation when used in combination. VEGF production is inhibited by vitamin E, but increased by PYY. ATS abolishes the augmented VEGF response to PYY. Our data suggest that PYY is involved in the regulation of VEGF production and prostate cancer growth.