Regulation of angiogenesis by histone chaperone HIRA-mediated incorporation of lysine 56-acetylated histone H3.3 at chromatin domains of endothelial genes.

Angiogenesis is critically dependent on endothelial cell-specific transcriptional mechanisms. However, the molecular processes that regulate chromatin domains and thereby dictate transcription of key endothelial genes are poorly understood. Here, we report that, in endothelial cells, angiogenic signal-mediated transcriptional induction of Vegfr1 (vascular endothelial growth factor receptor 1) is dependent on the histone chaperone, HIRA (histone cell cycle regulation-defective homolog A). Our molecular analyses revealed that, in response to angiogenic signals, HIRA is induced in endothelial cells and mediates incorporation of lysine 56 acetylated histone H3.3 (H3acK56) at the chromatin domain of Vegfr1. HIRA-mediated incorporation of H3acK56 is a general mechanism associated with transcriptional induction of several angiogenic genes in endothelial cells. Depletion of HIRA inhibits H3acK56 incorporation and transcriptional induction of Vegfr1 and other angiogenic genes. Our functional analyses revealed that depletion of HIRA abrogates endothelial network formation on Matrigel and inhibits angiogenesis in an in vivo Matrigel plug assay. Furthermore, analysis in a laser-induced choroidal neovascularization model showed that depletion of HIRA significantly inhibits neovascularization. Our results for the first time decipher a histone chaperone (HIRA)-dependent molecular mechanism in endothelial gene regulation and indicate that histone chaperones could be new targets for angiogenesis therapy.

Effects of short-term finasteride on apoptotic factors and androgen receptors in prostate cancer cells.

PURPOSE: We explored the molecular correlates of the effect of finasteride on prostate tissue in patients undergoing radical prostatectomy. MATERIALS AND METHODS: Patients undergoing radical prostatectomy for localized prostate cancer were eligible for study. After providing informed consent patients were randomized to receive 5 mg finasteride or placebo daily for at least 30 days before surgery. At surgery prostate tissue was harvested from the surgical specimen and sent for analysis. Tissue samples were analyzed for the pro-apoptotic factors caspase-3, caspase-7 and IGFBP-3. Samples were also analyzed for the tumor suppressor/proto-oncoproteins bcl-2, p53 and p21. Finally, tissues were analyzed for androgen receptor density and insulin growth factor-1. RESULTS: A total of 22 study and 20 placebo samples were collected and analyzed. Negligible staining for bcl-2 or caspase-3 was noted in each group. Statistical differences were not observed for bcl-2, p53, p21 or insulin growth factor-1 between the groups. There was a statistically significant difference in caspase-7 and IGFBP-3. A mean of 77% and 99.9% of cells stained for caspase-7 in the treatment and placebo groups, respectively (p = 0.007). In 3 patients caspase-7 staining disappeared completely and it was decreased by 70% and 50% in 1 patient each. Mean intensity staining for IGFBP-3 was 1.03 in the treatment group and 1.54 in the placebo group (p = 0.005). The staining intensity of nuclear androgen receptors on benign and cancerous cells was not significantly different between the treatment and placebo groups. However, there was a significant difference in androgen receptor staining between benign and cancer cells in the 2 populations. Mean nuclear androgen receptor staining intensity in all cancer and all benign tissue samples was 119.3 and 151.8, respectively (0.001). CONCLUSIONS: Finasteride administered 30 days before surgery appears to decrease the apoptotic factors caspase-7 and IGFBP-3 in cancer cells, while having little to no effect on caspase-3, insulin growth factor-1, bcl-2, p53 and p21. This short-term study may have interesting implications for interpreting Prostate Cancer Prevention Trial data on the molecular level. No differences were noted between the treatment and placebo groups in the expression of nuclear androgen receptor. However, decreased expression of androgen receptors was present in cancer cells compared to that in benign prostate cells in the 2 groups.