PDEF (prostate-derived ETS factor, also known as SAM-pointed domain containing ETS transcription factor (SPDEF)) is expressed in luminal epithelial cells of the prostate gland and associates with luminal phenotype. The Hippo pathway regulates cell growth/proliferation, cellular homeostasis, and organ development by modulating phosphorylation of its downstream effectors. In previous studies, we observed decreased levels of PDEF during prostate cancer progression. In the present study, we evaluated the effects of the expression of PDEF on total/phosphoprotein levels of YAP1 (a downstream effector of the Hippo pathway). We observed that the PC3 and DU145 cells transfected with PDEF (PDEF-PC3 and PDEF-DU145) showed an increased phospho-YAP1 (Ser127) and total YAP1 levels as compared to the respective PC3 vector control (VC-PC3) and DU145 vector control cells (VC-DU145). We also observed an increased cytoplasmic YAP1 levels in PDEF-PC3 cells as compared to VC-PC3 cells. Moreover, our gene set enrichment analysis (GSEA) of mRNA expression in PDEF-PC3 and VC-PC3 cells revealed that PDEF resulted in inhibition of YAP1 target genes, directly demonstrating that PDEF plays a critical role in modulating YAP1 activity, and by extension in the regulation of the Hippo pathway. We also observed a decrease in YAP1 mRNA levels in prostate cancer tissues as compared to normal prostate tissues. Our analysis of multiple publicly available clinical cohorts revealed a gradual decrease in YAP1 mRNA expression during prostate cancer progression and metastasis. This decrease was similar to the decrease in PDEF levels, which we had reported earlier, and we observed a direct correlation between PDEF and YAP1 expression in CRPC data set. To the best of our knowledge, these results provide the first demonstration of inhibiting YAP1 activity by PDEF in any system and suggest a cross-talk between PDEF and the Hippo signaling pathway.
PDEF is expressed in luminal epithelial cells of the prostate gland and associates with luminal phenotype. Hippo pathway regulates cell growth/proliferation, cellular homeostasis, and organ development by modulating phosphorylation of its downstream effectors. In previous studies, we observed decreased levels of PDEF during prostate cancer progression. In the present studies, we evaluated the effects of PDEF on total and phospho (Ser-127)YAP1 protein(a downstream effector of the Hippo pathway) levels in PC3 cells, a line of castrate resistant prostate cancer. We observed that the expression of PDEF in PC3 cells resulted in increased increased phospho(Ser127) -YAP1 protein levels. Our immunofluorescence analysis for YAP1 revealed an increased cytoplasmic/nuclear ratio of YAP1 in PDEF-PC3 cells as compared to VC-PC3 cells, suggesting PDEF may play a critical role in modulating YAP1 phosphorylation, and by extension in the regulation of the Hippo pathway. We also observed a decrease in YAP1 protein levels in prostate cancer tissues as compared to normal prostate tissues. Our analysis of multiple publicly available clinical cohorts revealed a gradual decrease in YAP1 mRNA expression during prostate cancer progression and metastasis. This decrease was similar to the decrease in PDEF levels which we reported earlier. In addition we observed further decreased in PDEF and YAP1 expression in Neuro-Endocrine Prostate Cancer (NEPC), and a direct correlation between PDEF and YAP1 expression. To the best of our knowledge, these results provide the first demonstration of modulation of YAP1 by PDEF in any system and suggest a cross-talk between PDEF and the Hippo pathway.
Background: The Hippo TEAD-transcriptional regulators YAP1 and TAZ play essential role in cancer cell growth and metastasis. However, the function of YAP1 and TAZ in prostate cancer is not well characterized. We discovered that expression of PDEF is decreased during prostate cancer progression and re-expression of PDEF limits prostate cancer metastasis in part by promoting luminal epithelial phenotype, but mechanisms of PDEF action are not completely understood. In the present study, we evaluated the effects of the SPDEF on YAP1/TAZ levels and expression of YAP1/TAZ regulated genes in prostate cancer (PCa) cells. We also evaluated expression of SPDEF, YAP1, TAZ and YAPTAZZ-Tead regulated genes in clinical cohorts of prostate cancer patients. Material & Method: Prostate cancer (PC3 and DU145) cells were transfected with PDEF or respective vector control. shRNA was used to knock down SPDEF in AR positive and androgen responsive LNCaP cells. Protein levels were analyzed by western blotting. Gene expression was monitored by microarray analysis/RNA seq and confirmed by RTPCR assays. Cell migration and invasion were measured by scratch wound healing and by trans well migration though Matrigel assays respectively. We analyzed publicly available gene expression data in several prostate cancer cohorts. Results: We observed that the two well-characterized metastatic PCa cells (PC3 and DU145 cells) express both YAP1 and TAZ, but do not express SPDEF. Expression of PDEF in PC3 and DU145 cells resulted in an increased phospho-YAP1 and phospho-TAZ protein levels and inhibition of YAP1/TAZ target genes, as compared to the respective vector control, directly demonstrating that PDEF plays a critical role in modulating YAP1/TAZ-TEAD transcriptional activity, and by extension in the regulation of the Hippo pathway. Analysis of publicly available PCa data sets revealed a significant increase in TAZ mRNA levels in prostate cancer tissues as compared to normal prostate tissues (p=4.95E-08). Furthermore, we also found a significant gradual increase in TAZ mRNA expression and concomitant decrease in YAP1 mRNA during disease progression and metastasis and in neuroendocrine PCa. Conclusions: Taken together these data suggest that SPDEF limits prostate cancer metastasis in part by targeting YAP1/TAZ driven transcriptional output. Citation Format: Hari K. Koul, Praveen K. Jaiswal, Suman Mohajan, Mousa Vatanmakanian, Fengtian Wang, Sweaty Koul. PDEF restricts prostate cancer cellular plasticity in part by modulating YAP1/TAZ-TEAD transcriptional network [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1457.
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