The tumour suppressor miR-34c targets MET in prostate cancer cells.

BACKGROUND: The microRNA, miR-34c, is a well-established regulator of tumour suppression. It is downregulated in most forms of cancers and inhibits malignant growth by repressing genes involved in processes such as proliferation, anti-apoptosis, stemness, and migration. We have previously reported downregulation and tumour suppressive properties for miR-34c in prostate cancer (PCa). METHODS: In this study, we set out to further characterize the mechanisms by which miR-34c deregulation contributes to PCa progression. The genes regulated by miR-34c in the PCa cell line PC3 were identified by microarray analyses and were found to be enriched in cell death, cell cycle, cellular growth, and cellular movement pathways. One of the identified targets was MET, a receptor tyrosine kinase activated by hepatocyte growth factor, that is crucial for metastatic progression. RESULTS: We confirmed the inhibitory effect of miR-34c on both MET transcript and protein levels. The binding of miR-34c to two binding sites in the 3'-UTR of MET was validated using luciferase reporter assays and target site blockers. The effect of this regulation on the miR-34c inhibition of the migratory phenotype was also confirmed. In addition, a significant inverse correlation between miR-34c expression levels and MET immunostaining was found in PCa patients. CONCLUSION: These findings provide a novel molecular mechanism of MET regulation in PCa and contribute to the increasing evidence that miR-34c has a key tumour suppressive role in PCa.

miR-205 negatively regulates the androgen receptor and is associated with adverse outcome of prostate cancer patients.

BACKGROUND: The microRNA-205 (miR-205) has been shown to be deregulated in prostate cancer (PCa). Here we continue to investigate the prognostic and therapeutic potential of this microRNA. METHODS: The expression of miR-205 is measured by qRT-PCR and in situ hybridisation in a well-documented PCa cohort. An AGO2-based RIP-Chip assay is used to identify targets that are verified with western blots, luciferase reporter assay, ELISA and immunohistochemistry. RESULTS: The expression of miR-205 is inversely correlated to the occurrence of metastases and shortened overall survival, and is lower in castration-resistant PCa patients. The miR-205 expression is mainly localised to the basal cells of benign prostate tissues. Genes regulated by miR-205 are enriched in, for example, the MAPK/ERK, Toll-like receptor and IL-6 signaling pathways. We demonstrate binding of miR-205 to the 3'UTR of androgen receptor (AR) and decrease of both AR transcript and protein levels. This finding was corroborated in the patient cohort were miR-205 expression inversely correlated to AR immunostaining in malignant prostate cells and to serum levels of prostate-specific antigen, an androgen-regulated protein. CONCLUSION: Taken together, these findings imply that miR-205 might have therapeutic potential, especially for the castration resistant and currently untreatable form of PCa.

A high-density tissue microarray from patients with clinically localized prostate cancer reveals ERG and TATI exclusivity in tumor cells.

BACKGROUND: Prostate cancer (PCa) is characterized by high tumor heterogeneity. In 2005, the fusion between the androgen-regulated gene TMPRSS2 and members of the ETS family was discovered in prostate cancer. In particular, fusion of TMPRSS2 with ERG was found in approximately 50% of prostate cancers and considered as an early event in the onset of the disease. The prognostic value of this fusion is still contradictory. Bioinformatics showed that overexpression of SPINK1 gene in a subset of fusion-gene-negative prostate cancers was associated with a poor prognosis. In theory, overexpression of the tumor-associated trypsin inhibitor (TATI) protein encoded by SPINK1 in fusion-gene-negative tumor cells opens the way to selected treatments for genotypically different cases. However, their expression has never been assessed at the cellular level in the same tissue samples. METHODS: As ERG expression has been shown to be a surrogate of fusion gene occurrence in prostate cancer, we have used double immunohistochemical staining to assess expression of ERG and TATI on a large tissue microarray comprising 4177 cases of localized prostate cancer. RESULTS: We did not detect any co-expression of ERG and TATI in the same cancer cells, which confirms previous suggestions from in silico studies. ERG was associated with Gleason score (GS), surgical margins and pathological stage, but had no prognostic value in this cohort. TATI was weakly associated with pathological stage but had no significant association with outcome. CONCLUSIONS: We here provide a morphological basis for ERG and TATI exclusivity in prostate cancer cells. Future therapies should be based on a combination of different targets in order to eradicate tumor cells with gene fusions and cells expressing other tumor-associated antigens. Further studies are needed to understand why ERG and TATI are not co-expressed in the same prostatic tumor cells.

Effect of androgen deprivation therapy on the expression of prostate cancer biomarkers MSMB and MSMB-binding protein CRISP3.

We have investigated the effects of short-term neoadjuvant and long-term androgen deprivation therapies (ADTs) on ß-microseminoprotein (MSMB) and cysteine-rich secretory protein-3 (CRISP3) expression in prostate cancer patients. We also studied if MSMB expression was related to genotype and epigenetic silencing. Using an Affymetrix cDNA microarray analysis, we investigated the expression of MSMB, CRISP3, androgen receptor (AR), KLK3 and Enhancer of Zeste Homologue-2 (EZH2) in tissue from prostate cancer patients receiving (n=17) or not receiving (n=23) ADT before radical prostatectomy. MSMB, CRISP3 and AR were studied in tissue from the same patients undergoing TURP before and during ADT (n=16). MSMB genotyping of these patients was performed by TaqMan PCR. MSMB and KLK3 expression levels decreased during ADT. Expression levels of AR and CRISP3 were not affected by short-term ADT but were high in castration-resistant prostate cancer (CRPC) and metastases. Levels of EZH2 were also high in metastases, where MSMB was low. Genotyping of the MSMB rs10993994 polymorphism showed that the TT genotype conveys poor MSMB expression. MSMB expression is influenced by androgens, but also by genotype and epigenetic silencing. AR and CRISP3 expression are not influenced by short-term ADT, and high levels were found in CRPC and metastases.

Differences in early and late responses between neurotrophin-stimulated trkA- and trkC-transfected SH-SY5Y neuroblastoma cells.

Despite their sympathetic neuroblast origin, highly malignant neuroblastoma tumors and derived cell lines have no or low expression of the neurotrophin receptor genes, trkA and trkC. Expression of exogenous trkA in neuroblastoma cells restores their ability to differentiate in response to nerve growth factor (NGF). Here we show that stable expression of trkC in SH-SY5Y neuroblastoma cells resulted in morphological and biochemical differentiation upon treatment with neurotrophin-3 (NT-3). To some extent, trkA- and trkC-transfected SH-SY5Y (SH-SY5Y/trkA and SH-SY5Y/trkC) cells resembled one another in terms of early signaling events and neuronal marker gene expression, but important differences were observed. Although induced Erk 1/2 and Akt/PKB phosphorylation was stronger in NT-3-stimulated SH-Y5Y/trkC cells, activation of the immediate-early genes tested was more prominent in NGF-treated SH-SY5Y/ trkA cells. In particular, c-fos was not induced in the SH-SY5Y/trkC cells. There were also phenotypic differences. The concentrations of norepinephrine, the major sympathetic neurotransmitter, and growth cone-located synaptophysin, a neurosecretory granule protein, were increased in NGF-treated SH-SY5Y/trkA but not in NT-3-treated SH-SY5Y/trkC cells. Our data suggest that NT-3/p145trkC and NGF/p140trkA signaling differ in some aspects in neuroblasoma cells, and that this may explain the phenotypic differences seen in the long-term neurotrophin-treated cells.