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Hindgut-derived endoderm can differentiate into rectal, prostatic, and bladder phenotypes. Stromal-epithelial interactions are crucial for this development; however, the precise mechanisms by which epithelium responds to stromal cues remain unknown. We have previously reported ectopic expression of peroxisome proliferator-activated receptor-γ2 (PPARγ2) increased androgen receptor expression and promoted differentiation of mouse prostate epithelium. PPARγ is also implicated in urothelial differentiation. Herein we demonstrate that knockdown of PPARγ2 in benign human prostate epithelial cells (BHPrEs) promotes urothelial transdifferentiation. Furthermore, in vitro and in vivo heterotypic tissue regeneration models with embryonic bladder mesenchyme promoted urothelial differentiation of PPARγ2-deficient BHPrE cells, and deficiency of both PPARγ isoforms 1 and 2 arrested differentiation. Because PTEN deficiency is cooperative in urothelial pathogenesis, we engineered BHPrE cells with combined knockdown of PPARγ and PTEN and performed heterotypic recombination experiments using embryonic bladder mesenchyme. Whereas PTEN deficiency alone induced latent squamous differentiation in BHPrE cells, combined PPARγ and PTEN deficiency accelerated the development of keratinizing squamous metaplasia (KSM). We further confirmed via immunohistochemistry that gene expression changes in metaplastic recombinants reflected human urothelium undergoing KSM. In summary, these data suggest that PPARγ isoform expression provides a molecular basis for observations that adult human epithelium can be transdifferentiated on the basis of heterotypic mesenchymal induction. These data also implicate PPARγ and PTEN inactivation in the development of KSM., (Copyright © 2013 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Introduction: Defects in the apoptosis pathway limit the effectiveness of radiation in non-small cell lung cancer (NSCLC) therapy. BV6 is an antagonist of cIAP1 and XIAP, members of the inhibitors of apoptosis (IAP) family. We investigated the potential of BV6 to sensitize NSCLC cell lines to radiation., Methods: HCC193 and H460 lung cancer cell lines were treated with BV6 to investigate the effects of drug administration on cell proliferation, apoptosis, inhibition of XIAP and cIAP1, and radiosensitivity. Subsequent immunoblotting and Hoechst staining were used to determine the role of apoptosis in radiosensitization. Finally, the pathway of apoptosis was characterized by Western blot analysis for cleaved caspase-8 and cleaved caspase-9 and enzyme-linked immunosorbent assays for TNF-α., Results: HCC193 was found to be more sensitive than H460 to BV6-induced apoptosis in a concentration-dependent and time-dependent manner. BV6 significantly sensitized both cell lines to radiation (HCC193-DER = 1.38, p < 0.05 at 1 μM BV6; H460-DER = 1.42, p < 0.05 at 5 μM BV6), but a higher concentration of and longer incubation time with BV6 was necessary for H460 cells. The BV6-induced radiosensitization of HCC193 favored the extrinsic pathway of apoptosis, whereas that of H460 favored the intrinsic pathway., Conclusions: BV6, an IAP antagonist, significantly enhanced the radiosensitization of HCC193 and H460 cells in vitro. More research is warranted to test the mechanism of action of BV6 and to assess its potential in vivo and in the clinical setting.