miR-1272 Exerts Tumor-Suppressive Functions in Prostate Cancer via HIP1 Suppression.

The development of novel therapies or the improvement of currently used approaches to treat prostate cancer (PCa), the most frequently diagnosed male tumor in developed countries, is an urgent need. In this regard, the functional characterization of microRNAs, molecules shown to regulate a number of cancer-related pathways, is instrumental to their possible clinical exploitation. Here, we demonstrate the tumor-suppressive role of the so far uncharacterized miR-1272, which we found to be significantly down-modulated in PCa clinical specimens compared to normal tissues. Through a gain-of-function approach using miRNA mimics, we showed that miR-1272 supplementation in two PCa cell models (DU145 and 22Rv1) reverted the mesenchymal phenotype by affecting migratory and invasive properties, and reduced cell growth in vitro and in vivo in SCID mice. Additionally, by targeting HIP1 encoding the endocytic protein HIP1, miR-1272 balanced EGFR membrane turnover, thus affecting the downstream AKT/ERK pathways, and, ultimately, increasing PCa cell response to ionizing radiation. Overall, our results show that miR-1272 reconstitution can affect several tumor traits, thus suggesting this approach as a potential novel therapeutic strategy to be pursued for PCa, with the multiple aim of reducing tumor growth, enhancing response to radiotherapy and limiting metastatic dissemination.

Gene expression dataset of prostate cells upon MIR205HG/LEADR modulation.

Although the role of miR-205 has been widely elucidated, the function of its host gene (MIR205HG) is yet to be clarified. We have recently investigated whether this gene is a simple endorsement for miRNA production or it may act independently, demonstrating its action as nuclear long noncoding RNA able to control basal-luminal differentiation in the human prostate context, thus deserving the reannotation as LEADR, Long Epithelial Alu-interacting Differentiation-related RNA. Here, we describe the loss and gain of function approaches experimentally used to modulate LEADR expression, and the bioinformatic procedures employed to analyze microarray data in our published article "LEADeR role of miR-205 host gene as long noncoding RNA in prostate basal cell differentiation" [1]. The high reproducibility of replicates, the strong concordance with a validation technique, and the coherent behavior observed for differentially expression features, both in terms of single genes and deregulated pathways, not only support the quality of the data, but also endorse their potential reuse. Very relevant are the diverse silencing and overexpression strategies employed (all of which analyzed in multiple biologically independent replicates), which should allow other scientists to analyze our dataset for the specific purpose of their research, may it be the study of MIR205HG function as miRNA host gene, the investigation of its miRNA-independent biological role or again the dissection of Alu sequence involvement in the mechanism of action of long noncoding RNAs, which is a hot topic in the field.

LEADeR role of miR-205 host gene as long noncoding RNA in prostate basal cell differentiation.

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).