Previous studies documented the ability of quinazoline-based a1-adrenoceptor antagonists to induce apoptosis in prostate cancer cells via an a1-adrenoceptor-independent mechanism. In this study we investigated the molecular events initiating this apoptotic effect. Since transforming growth factor-b1 (TGF-b1) mediates prostate epithelial cell apoptosis, we hypothesised that the activation of the TGF-b1 pathway underlies the quinazoline-based apoptotic effect in prostate cancer cells. Treatment of the androgenindependent human prostate cancer cells PC-3 with doxazosin resulted in a strong caspase-3 activation within 24 h, whereas tamsulosin, a sulphonamide-based a1-adrenoceptor antagonist, had no significant apoptotic effect against prostate cancer cells. To identify the molecular components involved in this quinazoline-mediated apoptosis, cDNA microarray analysis of PC-3 prostate cancer cells treated with doxazosin (3 h) was performed. Induced expression of several genes was observed including p21 WAF-1 and IkBa (inhibitor of NF-kB alpha). Relative quantitative reverse transcription -polymerase chain reaction analysis revealed induction of several TGF-b1 signalling effectors: Induction of mRNA for Smad4 and the TGF-b1-regulated apoptosis-inducing transcription factor TGF-b1-inducible early gene (TIEG1) was detected within the first 6 h of doxazosin treatment. Upregulation of IkBa at both the mRNA and protein level was also detected after 6 h of treatment. Furthermore, doxazosin resulted in a considerable elevation in Smad4 and TIEG protein expression (6 h). A 'latent' increase in TGF-b mRNA expression was detected after 48 h of treatment. These findings suggest that the quinazoline-based doxazosin mediates prostate cancer apoptosis by initially inducing the expression of TGF-b1 signalling effectors and subsequently IkBa. The present study provides an initial insight into the molecular targets of the apoptotic action of quinazolines against prostate cancer cells.

Runx transcription factors regulate viral growth, hematopoiesis, bone formation, angiogenesis, and gastric epithelial development through specific DNA-binding motifs on target gene promoters. Vascular endothelial cells (ECs) express RUNX genes that are activated by angiogenic factors. The RUNX2 gene also activates the vascular endothelial growth factor promoter. Alternatively spliced forms of RUNX genes have been described, but their functions in angiogenesis have not been elucidated. In this study, expression of a novel alternatively spliced variant of RUNX2 (RUNX2D8), lacking the region encoded by exon 8, was detected in aortic tissue undergoing angiogenesis in vitro and in ECs. Expression of RUNX2 and RUNX2D8 increased in vascular sprouts concomitant with expression of cellular proteases and cytokines known to mediate angiogenesis. RUNX2 DNA-binding activity was expressed in proliferating but not quiescent ECs. Ectopic expression of RUNX2 in ECs increased cell sprouting, cell proliferation, DNA synthesis, and phosphorylation of phosphorylated retinoblastoma relative to control transfectants while RUNX2, but not RUNX2D8 transfectants, acquired resistance to growth inhibition by transforming growth factor (TGFb 1 ). Furthermore, RUNX2D8-transfected cells were more sensitive to TGFb 1 -induced apoptosis than RUNX2 transfectants. Consistent with these data, the RUNX2 gene was a strong repressor of the promoter of the cyclin-dependent kinase inhibitor, p21 CIP1 , while RUNX2D8 was a competitive inhibitor of RUNX2 and exhibited weak repression activity. These results support the hypothesis that ECs regulate growth and apoptosis, in part, by alternative splicing events in the RUNX2 transcription factor to affect the TGFb 1 signaling pathway. The exon 8 domain of RUNX2 may contribute to the strong repression activity of RUNX2 for some target gene promoters.

a 1 -Adrenoceptor antagonists, have been documented to induce apoptosis and reduce prostate tumor vascularity in benign and malignant prostate cells. The quinazoline based a 1 -antagonists, doxazosin and terazosin but not tamsulosin (a sulphonamide derivative) suppress prostate growth without affecting cell proliferation. These quinazoline-mediated apoptotic effects occur via an a 1 -adrenoceptor independent mechanism potentially involving activation of the TGF-b signal transduction pathway. This review discusses the current knowledge of the action of quinazoline-derived a 1 -adrenoceptor antagonists in the benign and malignant prostate and their potential therapeutic use in the treatment of benign prostatic hyperplasia (BPH) and prostate cancer. Finally, a molecular pathway is proposed for their observed apoptotic function against prostate cells. Increased understanding of the action of these established and clinically accepted agents would provide a basis for the design of safe, effective therapeutic regimens in the treatment of prostatic diseases.

The Runt box domain DNA-binding transcription factors (RUNX) play key roles in hematopoietic, bone, and gastric development. These factors regulate angiogenesis and tumorigenic events, functioning as either activators or repressors of target genes. Although RUNX2 is an essential bone maturation factor, it has also been found to promote transformation in vivo and cell proliferation in vitro, perhaps by associating with specific coactivators or corepressors. Adenoviral-mediated overexpression of dominant negative RUNX2 or specific reduction of RUNX2 with RNA-interference inhibits cell proliferation. To determine whether RUNX2 also plays a role in cell transformation, RUNX2 interactions with the coactivator Yes-associated protein (YAP65) were examined. RUNX2 associated with YAP65 via a proline-rich segment in the C-terminal domain (PPPY) and coexpression of RUNX2 and YAP65 significantly increased foci formation and anchorage-independent growth relative to each factor alone. However, in contrast to wild-type RUNX2, a mutant RUNX2(P409A), which does not bind YAP65, did not cooperate with YAP65 to promote anchorage-independent growth. RUNX2 is a strong repressor of the cyclin-dependent kinase inhibitor p21(CIP1), which is known to mediate cell transformation. Overexpression of YAP65 prevented RUNX2-dependent downregulation of p21(CIP1) protein expression while promoting cell transformation. The RUNX2(P409A) mutant retained the ability to bind DNA and repress the p21(CIP1) promoter as shown by DNA precipitation and luciferase-reporter assays, respectively, but was not able to relieve repression of the p21(CIP1) promoter. Therefore, these results reveal a novel function of the RUNX2 and YAP65 interaction in oncogenic transformation that may be mediated by modulation of p21(CIP1) protein expression.

The tumor suppressor retinoblastoma protein (Rb) plays a pivotal role in the regulation of cell proliferation and sensitivity to apoptosis through binding to E2F transcription factors. Loss of Rb in response to genotoxic stress or inflammatory cytokines can enhance cell death, in part, by eliminating Rb-mediated repression of proapoptotic gene transcription. Here we show that calpain cleavage of Rb facilitates Rb loss by proteasome degradation and that this may occur during tumor necrosis factor A-induced apoptosis. The cytoprotective, Rb-binding protein SerpinB2 (plasminogen activator inhibitor type 2) protects Rb from calpain cleavage, increasing Rb levels and enhancing cell survival. Chromatin immunoprecipitation assays show that the increased Rb levels selectively enhance Rb repression of proapoptotic gene transcription. This cytoprotective role of SerpinB2 is illustrated by reduced susceptibility of SerpinB2-deficient mice to multistage skin carcinogenesis, where Rbdependent cell proliferation competes with apoptosis during initiation of papilloma development. These data identify SerpinB2 as a cell survival factor that modulates Rb repression of proapoptotic signal transduction and define a new posttranslational mechanism for selective regulation of the intracellular levels of Rb.