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Following the publication of the above article, the authors noted an error in Figure 4, panel B. The colours of the localized and mCRPC samples were accidentally switched. The authors have corrected the colour scheme and added a key to the figure. They have also updated the colour scheme of panel C, both bars are now red instead of one red and one blue. The authors wish to apologize for any inconvenience caused.

The propensity of cancer cells to transition between epithelial and mesenchymal phenotypic states via the epithelial-mesenchymal transition (EMT) program can regulate metastatic processes, cancer progression, and treatment resistance. Transcriptional investigations using reversible models of EMT, revealed the mesenchymal-to-epithelial reverting transition (MErT) to be enriched in clinical samples of metastatic castrate resistant prostate cancer (mCRPC). From this enrichment, a metastasis-derived gene signature was identified that predicted more rapid cancer relapse and reduced survival across multiple human carcinoma types. Additionally, the transcriptional profile of MErT is not a simple mirror image of EMT as tumour cells retain a transcriptional "memory" following a reversible EMT. This memory was also enriched in mCRPC samples. Cumulatively, our studies reveal the transcriptional profile of epithelial-mesenchymal plasticity and highlight the unique transcriptional properties of MErT. Furthermore, our findings provide evidence to support the association of epithelial plasticity with poor clinical outcomes in multiple human carcinoma types.

Hedgehog (Hh) is an oncogenic signaling pathway that regulates the activity of Gli transcription factors. Canonical Hh is a Smoothened- (Smo-) driven process that alters the post-translational processing of Gli2/Gli3 proteins. Though evidence supports a role for Gli action in prostate cancer (PCa) cell growth and progression, there is little indication that Smo is involved. Here we describe a non-canonical means for activation of Gli transcription in PCa cells mediated by the binding of transcriptionally-active androgen receptors (ARs) to Gli3. Androgens stimulated reporter expression from a Gli-dependent promoter in a variety of AR + PCa cells and this activity was suppressed by an anti-androgen, Enz, or by AR knockdown. Androgens also upregulated expression of endogenous Gli-dependent genes. This activity was associated with increased intranuclear binding of Gli3 to AR that was antagonized by Enz. Fine mapping of the AR binding domain on Gli2 showed that AR recognizes the Gli protein processing domain (PPD) in the C-terminus. Mutations in the arginine-/serine repeat elements of the Gli2 PPD involved in phosphorylation and ubiquitinylation blocked the binding to AR. β-TrCP, a ubiquitin ligase that recognizes the Gli PPD, competed with AR for binding to this site. AR binding to Gli3 suppressed its proteolytic processing to the Gli3 repressor form (Gli3R) whereas AR knockdown increased Gli3R. Both full-length and truncated ARs were able to activate Gli transcription. Finally, we found that an ARbinding decoy polypeptide derived from the Gli2 C-terminus can compete with Gli3 for binding to AR. Exogenous overexpression of this decoy suppressed Gli transcriptional activity in PCa cells. Collectively, this work identifies a novel pathway for non-canonical activation of Hh signaling in PCa cells and identifies a means for interference that may have clinical relevance for PCa patients.

In order to identify gene products associated with the development of acquired therapeutic resistance by prostate cancer cells, we created two novel apoptosis-resistant prostate cancer cell lines, LNCaP-TR (phorbol-ester [TPA]-Resistant) and LNCaP-SSR (Serum Starvation-Resistant) by repeated transient exposure of cultured human LNCaP cells to apoptotic stimuli followed by expansion of surviving cell populations. These cell lines were found to be cross-resistant to the alternative selective agent and also hormone-resistant when xenografted into castrated male immunodeficient mice. RNA from the LNCaP-TR line was comparatively screened using a subtractive hybridization-PCR procedure. This allowed us to identify a 249 bp cDNA fragment that hybridized to a 4.8 kb mRNA preferentially expressed by the apoptosis-resistant cells. Using RACE procedures, we cloned and sequenced the complete 4.8 kb cDNA. It is an unusual member of the protocadherin gene family containing two large overlapping open reading frames encoding homologous polypeptides, one having a signal sequence and the other lacking a signal sequence and we refer to it as protocadherin-PC. LNCaP cells directly transformed with protocadherin-PC cDNA were comparatively resistant to phorbol-ester induced apoptosis. Antibody recognition studies demonstrating the cytoplasmic nature of the protcadherin-PC translation product and its propensity to bind beta-catenin suggest that it might influence the apoptotic sensitivity of prostate cancer cells through a unique mechanism.

Several in vitro studies have provided evidence that the tumor suppressor protein, p53, is involved in the cell death process referred to as apoptosis. The recent development of p53 knock-out mice has enabled further investigation into the function of p53 for apoptosis, in vivo. Radiation-induced apoptosis is suppressed in such mice, yet other forms of apoptosis do not seem to be significantly affected. In this report, we present evidence that such male p53 nullizygous mice have less apoptosis in the prostate glands associated with the first 4 days following castration. Ventral prostate glands were obtained from normal, heterozygous p53-null and p53 nullizygous mice at daily intervals after castration. These tissues were stained for apoptosis with the use of the in situ and labeling method and apoptotic bodies were quantified by microscopy. Although labeled apoptotic bodies were observed in post-castrated tissues from all of these genetic variant mice, the onset of apoptosis was delayed and the occurrence of apoptosis was significantly reduced in the p53 nullizygous mice when compared to normal controls. Heterozygous p53-null mice were intermediate for these criteria. Examination of the internucleosomal DNA fragmentation pattern at 2 days of castration supports a significant diminution of prostate cell apoptosis in nullizygous p53 mice. Additionally, large nucleated and multinucleated cells were detected in the prostate epithelium of noncastrated p53 nullizygous mice and these abnormal cells were increased after castration. Flow cytometric analysis of these tissues confirmed a high number of 4C and 8C DNA content cells in the p53 nullizygous prostates and their frequency was increased by castration. In concordance with an earlier study, we conclude that functional p53 protein is not essential for prostate epithelial cells to undergo castration-induced apoptosis. However, wild-type p53 does appear to enhance this process, especially in the early period following castration, and this protein may regulate an aberrant prostate cell cycling activity that follows castration.