Prostate cancer is a leading cause of tumor mortality. To characterize the underlying molecular mechanisms, we have compared the microRNA (miRNA) profile of primary prostate cancers and noncancer prostate tissues using deep sequencing. MiRNAs are small noncoding RNAs of 21 to 25 nucleotides that regulate gene expression through the inhibition of protein synthesis. We find that 33 miRNAs were upregulated or downregulated >1.5-fold. The deregulation of selected miRNAs was confirmed by both Northern blotting and quantitative reverse transcription-PCR in established prostate cancer cell lines and clinical tissue samples. A computational search indicated the 3′-untranslated region (UTR) of the mRNA for myosin VI (MYO6) as a potential target for both miR-143 and miR-145, the expression of which was reduced in the tumor tissues. Upregulation of myosin VI in prostate cancer was previously shown by immunohistochemistry. The level of MYO6 mRNA was significantly induced in all primary tumor tissues compared with the nontumor tissue from the same patient. This finding was matched to the upregulation of myosin VI in established prostate cancer cell lines. In luciferase reporter analysis, we find a significant negative regulatory effect on the MYO6 3′UTR by both miR-143 and miR-145. Mutation of the potential binding sites for miR-143 and miR-145 in the MYO6 3′ UTR resulted in a loss of responsiveness to the corresponding miRNA. Our data indicate that miR-143 and miR-145 are involved in the regulation of MYO6 expression and possibly in the development of prostate cancer. Mol Cancer Res; 8(4); 529-38. ©2010 AACR.

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BackgroundThis study evaluated the cytotoxic and antiproliferative efficacy of two well-characterized members of the Cecropin-family of antimicrobial peptides against bladder tumor cells and benign fibroblasts.MethodsThe antiproliferative and cytotoxic potential of the Cecropins A and B was quantified by colorimetric WST-1-, BrdU- and LDH-assays in four bladder cancer cell lines as well as in murine and human fibroblast cell lines. IC50 values were assessed by logarithmic extrapolation, representing the concentration at which cell viability was reduced by 50%. Scanning electron microscopy (SEM) was performed to visualize the morphological changes induced by Cecropin A and B in bladder tumor cells and fibroblasts.ResultsCecropin A and B inhibit bladder cancer cell proliferation and viability in a dose-dependent fashion. The average IC50 values of Cecropin A and B against all bladder cancer cell lines ranged between 73.29 μg/ml and 220.05 μg/ml. In contrast, benign fibroblasts were significantly less or not at all susceptible to Cecropin A and B. Both Cecropins induced an increase in LDH release from bladder tumor cells whereas benign fibroblasts were not affected. SEM demonstrated lethal membrane disruption in bladder cancer cells as opposed to fibroblasts.ConclusionCecropin A and B exert selective cytotoxic and antiproliferative efficacy in bladder cancer cells while sparing targets of benign murine or human fibroblast origin. Both peptides may offer novel therapeutic strategies for the treatment of bladder cancer with limited cytotoxic effects on benign cells.

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Sec62 is part of the protein translocation apparatus in the membrane of the endoplasmic reticulum (ER). In yeast, Sec62 participates in the post-translational translocation of proteins into the ER, but its function in mammals remains elusive. Previously we described the amplification and over-expression of the SEC62 gene in prostate cancer cell lines and the protein has been described as a potential target gene in prostate cancer. In the current study we show that in the tumor tissue of prostate cancer patients Sec62 protein levels are elevated compared with tumor-free tissue derived from the same patients or from prostates of control group patients and that the higher Sec62 protein content correlates with an increasing dedifferentiation of the cells. Therefore, up-regulation of Sec62 protein content indeed is a phenomenon associated with prostate cancer progression. Analysis of a multi-tissue tumor array showed that in addition to prostate cancer, overproduction of Sec62 is observed in various other tumors, most significantly in tumors of the lung and the thyroid. To examine the tumorrelated functions of Sec62, we silenced the SEC62 gene in the prostate cancer cell-line PC3 as well as in a set of other tumor cell-lines with two different siRNAs. In general, after silencing of SEC62 the cell migration and the invasive potential of the cells was blocked or at least dramatically reduced while cell viability was hardly affected. Thus, the SEC62 gene may indeed be considered as a target gene in the therapy of various tumors.In yeast, Sec62 is part of the tetrameric Sec62/Sec63-subcomplex of the Sec-complex, and functions as a docking site for posttranslational protein transport to the membrane or lumen of the endoplasmic reticulum (ER).1 A contribution to the secretory pathway for the mammalian ortholog has yet to be shown. As in yeast, mammalian Sec62 is also associated with the Sec61-complex, the main pore for protein translocation in the ER membrane, and with Sec63, an ER membrane protein containing a luminal J-domain.2 In contrast to the yeast protein, the mammalian protein can interact with ribosomes via two conserved peptide motifs in the N-terminal cytosolic domain. 3,4 These functional elements allow the protein to regulate translation, influence protein translocation to the ER, and to indirectly interact with the key regulator of the unfolded protein response (UPR), BiP (Grp78, HspA5), thereby affecting cells' responses to ER stress inducers. We previously characterized SEC62 as a probable target gene in prostate cancer because the copy number of the SEC62 gene is increased in DU145, DU145MN1 and PC3 cells; Sec62 mRNA is the most frequently over-expressed mRNA in prostate cancer samples; and the protein content level of Sec62 is increased in at least DU145 and DU145MN1 cells. 5 In the present study, we analyzed Sec62 protein levels in more detail by comparing prostate cancer tissue to normal tissue from the same patient, and to benign prostate tissue from glands without prostate cancer by western blot ...