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Diffuse malignant peritoneal mesothelioma (DMPM) is a rare and rapidly lethal tumor, poorly responsive to conventional treatments. In this regards, the identification of molecular alterations underlying DMPM onset and progression might be exploited to develop novel therapeutic strategies. Here, we focused on miR-550a-3p, which we found downregulated in 45 DMPM clinical samples compared to normal tissues and whose expression levels were associated with patient outcome. Through a gain-of-function approach using miRNA mimics in 3 DMPM cell lines, we demonstrated the tumor-suppressive role of miR-550a-3p. Specifically, miRNA ectopic expression impaired cell proliferation and invasiveness, enhanced the apoptotic response, and reduced the growth of DMPM xenografts in mice. Antiproliferative and proapoptotic effects were also observed in prostate and ovarian cancer cell lines following miR-550a-3p ectopic expression. miR-550a-3p effects were mediated, at least in part, by the direct inhibition of HSP90AA1 and the consequent downregulation of its target proteins, the levels of which were rescued upon disruption of miRNA-HSP90AA1 mRNA pairing, partially abrogating miR-550a-3p-induced cellular effects. Our results show that miR-550a-3p reconstitution affects several tumor traits, thus suggesting this approach as a potential novel therapeutic strategy for DMPM.

Background Radiotherapy is one of the main treatment options for non-metastatic prostate cancer (PCa). Although treatment technical optimization has greatly improved local tumor control, a considerable fraction of patients still experience relapse due to the development of resistance. Radioresistance is a complex and still poorly understood phenomenon involving the deregulation of a variety of signaling pathways as a consequence of several genetic and epigenetic abnormalities. In this context, cumulative evidence supports a functional role of microRNAs in affecting radioresistance, suggesting the modulation of their expression as a novel radiosensitizing approach. Here, we investigated for the first time the ability of miR-205 to enhance the radiation response of PCa models. Methods miR-205 reconstitution by a miRNA mimic in PCa cell lines (DU145 and PC-3) was used to elucidate miR-205 biological role. Radiation response in miRNA-reconstituted and control cells was assessed by clonogenic assay, immunofluorescence-based detection of nuclear γ-H2AX foci and comet assay. RNAi was used to silence the miRNA targets PKCε or ZEB1. In addition, target-protection experiments were carried out using a custom oligonucleotide designed to physically disrupt the pairing between the miR-205 and PKCε. For in vivo experiments, xenografts generated in SCID mice by implanting DU145 cells stably expressing miR-205 were exposed to 5-Gy single dose irradiation using an image-guided animal micro-irradiator. Results miR-205 reconstitution was able to significantly enhance the radiation response of prostate cancer cell lines and xenografts through the impairment of radiation-induced DNA damage repair, as a consequence of PKCε and ZEB1 inhibition. Indeed, phenocopy experiments based on knock-down of either PKCε or ZEB1 reproduced miR-205 radiosensitizing effect, hence confirming a functional role of both targets in the process. At the molecular level, miR-205-induced suppression of PKCε counteracted radioresistance through the impairment of EGFR nuclear translocation and the consequent DNA-PK activation. Consistently, disruption of miR-205-PKCε 3’UTR pairing almost completely abrogated the radiosensitizing effect. Conclusions Our results uncovered the molecular and cellular mechanisms underlying the radiosensitizing effect of miR-205. These findings support the clinical interest in developing a novel therapeutic approach based on miR-205 reconstitution to increase PCa response to radiotherapy.

Prostate cancer (PCa) ranges from indolent to aggressive tumors that may rapidly progress and metastasize. The switch to aggressive PCa is fostered by reactive stroma infiltrating tumor foci. Therefore, reactive stroma-based biomarkers may potentially improve the early detection of aggressive PCa, ameliorating disease classification. Gene expression profiles of PCa reactive fibroblasts highlighted the up-regulation of genes related to stroma deposition, including periostin and sparc. Here, the potential of periostin as a stromal biomarker has been investigated on PCa prostatectomies by immunohistochemistry. Moreover, circulating levels of periostin and sparc have been assessed in a low-risk PCa patient cohort enrolled in active surveillance (AS) by ELISA. We found that periostin is mainly expressed in the peritumoral stroma of prostatectomies, and its stromal expression correlates with PCa grade and aggressive disease features, such as the cribriform growth. Moreover, stromal periostin staining is associated with a shorter biochemical recurrence-free survival of PCa patients. Interestingly, the integration of periostin and sparc circulating levels into a model based on standard clinico-pathological variables improves its performance in predicting disease reclassification of AS patients. In this study, we provide the first evidence that circulating molecular biomarkers of PCa stroma may refine risk assessment and predict the reclassification of AS patients.

Though miR-205 function has been largely characterized, the nature of its host gene, MIR205HG, is still completely unknown. Here, we show that only lowly expressed alternatively spliced MIR205HG transcripts act as de facto pri-miRNAs, through a process that involves Drosha to prevent unfavorable splicing and directly mediate miR-205 excision. Notably, MIR205HG-specific processed transcripts revealed to be functional per se as nuclear long noncoding RNA capable of regulating differentiation of human prostate basal cells through control of the interferon pathway. At molecular level, MIR205HG directly binds the promoters of its target genes, which have an Alu element in proximity of the Interferon-Regulatory Factor (IRF) binding site, and represses their transcription likely buffering IRF1 activity, with the ultimate effect of preventing luminal differentiation. As MIR205HG functions autonomously from (albeit complementing) miR-205 in preserving the basal identity of prostate epithelial cells, it warrants reannotation as LEADeR (Long Epithelial Alu-interacting Differentiation-related RNA)., miR-205 is known to have context-dependent tumor suppressive or oncogenic roles. Here, the authors report the host gene of miR-205, MIR205HG as a nuclear lincRNA that maintains the basal identity of prostate cell and prevents luminal cell differentiation via the repression of interferon responsive genes.

Background Genomic characterization of prostate cancer (PCa) biopsies may improve criteria for the selection of patients suitable for active surveillance (AS). Objective To identify somatic genomic aberrations associated with adverse outcome as AS protocol exclusion indicators. Design, setting and participants Whole-exome sequencing profiles were generated for Gleason score (GS) = 3 + 3 biopsies obtained from 54 PCa patients enrolled in two AS protocols. Patients were selected as representative of a nonindolent population, consisting of 27 patients who dropped out from AS due to upgrading (ie, finding of GS > 3 + 3 at a follow-up biopsy) within 2 yr, and a potentially indolent population, consisting of 27 patients in AS for ≥4 yr without any evidence of reclassification. Outcome measurements and statistical analysis The genomic alteration landscape of core biopsies was analyzed using an integrated computational pipeline and correlated with patient reclassification due to upgrading. Results and limitations Of all the GS = 3 + 3 biopsies of the study cohort, 34% showed clear evidence of somatic copy number aberrations along the genome. Of these, 39% came from the potentially indolent and 61% from the nonindolent population. Single-nucleotide variants demonstrated low allelic fractions and included a common F133C mutation in the SPOP gene. The minimally altered genomic landscape of the study cohort presented a distinct set of monoallelic deletions, including on 8p, 13q, 16q, and 21q, and rare amplifications of 8q, which were observed in both AS patient populations. Concerning lesions typically associated with adverse outcome, PTEN deletions and MYC amplification, though observed in a small number of cases, were detected exclusively or preferentially, respectively, in nonindolent patients. Such molecular findings were confirmed by immunohistochemistry on the same tissue blocks. The small sample size and the retrospective nature of the analysis represent the main study limitations. Conclusions Genomic features enriched in aggressive tumors can be detected in GS = 3 + 3 core biopsies of AS patients. Patient summary PTEN and MYC alterations at the time of diagnosis would deserve investigation in larger cohorts of AS patients to assess their potential as biomarkers for a more precise/earlier identification of patients at risk of reclassification.

Metastatic prostate cancer is a lethal disease that remains incurable despite the recent approval of new drugs, thus making the development of alternative treatment approaches urgently needed. A more precise understanding of the molecular mechanisms underlying prostate cancer dissemination could lead to the identification of novel therapeutic targets for the design of efficient anti-metastatic strategies. MicroRNA (miRNAs) are endogenous, small non-coding RNA molecules acting as key regulators of gene expression at post-transcriptional level. It has been clearly established that altered miRNA expression is a common hallmark of cancer. In addition, emerging evidence suggests their direct involvement in the metastatic cascade. In this review, we present a comprehensive overview of the data generated in experimental tumor models indicating that specific miRNAs may impinge on the different stages of prostate cancer metastasis, including (i) the regulation of epithelial-to-mesenchymal transition and cell migration/invasion, (ii) the interplay between cancer cells and the surrounding stroma, (iii) the control of angiogenesis, (iv) the regulation of anoikis, and (v) the colonization of distant organs. Moreover, we show preliminary evidence of the clinical relevance of some of these miRNAs, in terms of association with tumor aggressiveness/dissemination and clinical outcome, as emerged from translation studies carried out in prostate cancer patient cohorts. We also discuss the potential and the current limitations of manipulating metastasis-related miRNAs, by mimicking or inhibiting them, as a strategy for the development of novel therapeutic approaches for the advanced disease.

Tumor microenvironment coevolves with and simultaneously sustains cancer progression. In prostate carcinoma (PCa), cancer associated fibroblasts (CAF) have been shown to fuel tumor development and metastasis by mutually interacting with tumor cells. Molecular mechanisms leading to activation of CAFs from tissue-resident fibroblasts, circulating bone marrow-derived fibroblast progenitors or mesenchymal stem cells are largely unknown. Through integrated gene and microRNA expression profiling, we showed that PCa-derived CAF transcriptome strictly resembles that of normal fibroblasts stimulated in vitro with interleukin-6 (IL6), thus proving evidence, for the first time, that the cytokine is able per se to induce most of the transcriptional changes characteristic of patient-derived CAFs. Comparison with publicly available datasets, however, suggested that prostate CAFs may be alternatively characterized by IL6 and TGFβ-related signatures, indicating that either signal, depending on the context, may concur to fibroblast activation. Our analyses also highlighted novel pathways potentially relevant for induction of a reactive stroma. In addition, we revealed a role for muscle-specific miR-133b as a soluble factor secreted by activated fibroblasts to support paracrine activation of non-activated fibroblasts or promote tumor progression. Overall, we provided insights into the molecular mechanisms driving fibroblast activation in PCa, thus contributing to identify novel hits for the development of therapeutic strategies targeting the crucial interplay between tumor cells and their microenvironment.