Therapeutic Target For Prostate Cancer Treatment Research Articles

MicroRNA-211 suppresses prostate cancer proliferation by targeting SPARC.

Dysregulation of microRNAs (miRNAs/miRs) is frequently associated with cancer progression. Altered expression of miR-211 has been observed in various types of human cancer; however, its expression and role in prostate cancer (PCa) remains unknown. In the present study, the expression of miR-211 in PCa cell lines and tissues was measured by reverse transcription-quantitative PCR (qPCR), revealing that miR-211 was downregulated in PCa cell lines and tissues. Further analysis revealed that low miR-211 was associated with the tumor stage and Gleason score. With the assistance of miR-211 mimics and inhibitor, it was also revealed that the overexpression of miR-211 could inhibit PCa cell proliferation in vitro. Conversely, downregulated miR-211 expression promotes PCa cell proliferation. In addition, the secreted protein acidic and rich in cysteine (SPARC) was identified as a target of miR-211 in the PCa cell lines, and SPARC expression was inversely associated with miR-211. In conclusion, it was demonstrated that the miR-211 expression was downregulated in PCa cell lines and tissues. Additionally, miR-211 could inhibit PCa cell proliferation partially by downregulating SPARC. Therefore, miR-211 may be a potential therapeutic target for PCa treatment in the future.

Downregulation of Rab23 in Prostate Cancer Inhibits Tumor Growth In Vitro and In Vivo.

Rab23, a novel member of the Rab GTPase family, was found to be implicated in the progression of some human cancers. However, what role Rab23 plays in prostate cancer (PCa) remains to be illustrated. In the present study, we investigated the expression pattern and roles of Rab23 in PCa. The study results showed that Rab23 was upregulated in PCa tissues and cell lines. Moreover, downregulation of Rab23 remarkably suppressed the proliferation, migration, and invasion of PCa cells. In addition, downregulation of Rab23 significantly downregulated the protein expression levels of Shh and Gli1. Furthermore, we found that the Gli1 inhibitor GANT-61 greatly enhanced the suppressive effect of Rab23 downregulation on PCa cells. In conclusion, we suggested Rab23 as a potential therapeutic target for PCa treatment.

PYK2 via S6K1 regulates the function of androgen receptors and the growth of prostate cancer cells.

Androgen receptor (AR) is a steroid hormone receptor that functions as a transcription factor for regulating cell growth and survival. Aberrant AR function becomes a risk factor for promoting the progression of prostate cancer (PCa). In this study, we examined the roles of proline-rich tyrosine kinase 2 (PYK2) and ribosomal S6 kinase 1 (S6K1) in regulating AR expression and activity and growth properties in PCa cells. Compared with normal prostate tissues, PCa tumors exhibited high levels of PYK2 and S6K1 expression. Furthermore, the expression levels of PYK2 and S6K1 were significantly correlated with nuclear AR expression in PCa tissues. We further found the association between PYK2, S6K1, and AR in their protein expression and phosphorylation levels among normal prostate PZ-HPV-7 cells and prostate cancer LNCaP and 22Rv1 cells. Overexpression of the wild-type PYK2 in PZ-HPV-7 and LNCaP cells promoted AR and S6K1 expression and phosphorylation as well as enhanced cell growth. In contrast, expression of the mutated PYK2 or knockdown of PYK2 expression in LNCaP or 22Rv1 cells caused reduced expression or phosphorylation of AR and S6K1 as well as retarded cell growth. Under an androgen-deprived condition, PYK2-promoted AR expression and phosphorylation and PSA production in LNCaP cells can be abolished by knocking down S6K1 expression. In summary, our data suggested that PYK2 via S6K1 activation modulated AR function and growth properties in PCa cells. Thus, PYK2 and S6K1 may potentially serve as therapeutic targets for PCa treatment.

Abstract 1651: Overexpression of hepatoma upregulated protein (HURP) promotes radioresistance in prostate cancer cells

Abstract Despite progression in diagnosis and treatment, prostate cancer (PCa) still represents major cause of cancer-related mortality and morbidity in men. Although radiation therapy offers clinical benefit over other therapeutic modalities, the success of this therapeutic modality is commonly hampered by significant resistance in advanced tumor. So far, the mechanisms governing the acquired resistance to radiotherapy have not been discussed in detail. Hepatoma Up-Regulated Protein (HURP) is a cell cycle-regulated and microtubule-associated protein. It functions as a Ran GTPase effector and is involved in the stabilization of the mitotic kinetochore fibers. The expression of this protein is elevated in different tumor types and associated with tumor progression and aggressiveness. We recently reported on the value of HURP as an independent prognostic factor for high-risk PCa. The aim of this study was to address the role of HURP in the modulation of PCa resistance to γ- irradiation. Cell lines (LNCaP, PC3, and DU145) with regulated expression of HURP protein using a Lent viral Tet-On 3G Inducible Expression System were irradiated using a Cs-137 γ-source. Overexpression of HURP suppressed γ- irradiation- induced apoptosis. This suppression was associated with the expression of E2F1, p53, p21 together with the phosphorylation of apoptosis signal-regulating kinase1 (ASK1), c-jun-N-terminal kinase (JNK) and Ataxia-telangiectasia mutated (ATM) and histone family member X (H2AX). Also, inhibition of γ- irradiation- induced- cytochrome c release, cleavage of caspase-9, caspase-3, PARP, and reactive oxygen species (ROS) was noted. The observed resistance was consequence of HURP's ability to trigger the ubiquitination of p53 and ATM that, in turn, resulted in the inhibition of downstream pathways, which are essential for the modulation of γ- irradiation-induced apoptosis. Our data provide evidence for the involvement of HURP in the modulation of PCa cell resistance to γ-irradiation via a mechanism mediated by ubiquitination of ATM and p53. Understanding of the biological mechanisms underlying HURP-mediated resistance of PCa to available therapies may help to improve the treatment strategy and emphasize HURP as therapeutic target for PCa treatment. Funding sources: Department of Defense Grant PC094680 and Prostate Cancer Foundation Creativity Award. Citation Format: Mohamed Hassan, Abdelouahid El Khattouti, Tangeng Ma, Ingrid Espinoza, W. Andrew Day, Srinivasan Vijayakumar, Christian R. Gomez. Overexpression of hepatoma upregulated protein (HURP) promotes radioresistance in prostate cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1651.

MiR-185 attenuates androgen receptor function in prostate cancer indirectly by targeting bromodomain containing 8 isoform 2, an androgen receptor co-activator

ObjectivesAberrant androgen receptor (AR) signaling functions are implicated in prostate cancer (PCa) pathogenesis. Here, we studied interactions between miR-185 and the bromodomain containing 8 isoform 2 (BRD8 ISO2) to investigate indirect mechanisms of miR-185 with respect to AR function through BRD8 ISO2 in PCa. MethodsPutative miRNA response element (MRE) of miR-185 in 3′-untranslated region (3′-UTR) of BRD8 ISO2 mRNA was predicted by software and confirmed using dual-luciferase assays and Ago2 immunoprecipitation. BRD8 and AR expression were determined by qRT-PCR and Western blot in PCa cells and tissues. MMTV-Fluc reporter plasmids and dual-luciferase assays were used to evaluate AR activity. ResultsMRE prediction, dual-luciferase assays and Ago2 immunoprecipitation confirmed that miR-185 is capable of binding the 3′-UTR of BRD8 ISO2 mRNA. QRT-PCR and Western blot indicated that BRD8 ISO2 expression is decreased by miR-185 mimic transfection while increased by miR-185 inhibitor transfection. MMTV-Fluc reporter assays revealed that miR-185 can attenuate AR function by suppressing BRD8 ISO2. Additionally, Pearson's correlation analyses confirmed that BRD8 ISO2 mRNA expression is inversely correlated with miR-185 expression in clinical specimens. ConclusionIn addition to suppression of AR expression, miR-185 can attenuate AR function indirectly by suppressing BRD8 ISO2. MiR-185 and BRD8 ISO2 may be possible therapeutic targets for PCa treatment.

P300 acetyltransferase regulates fatty acid synthase expression, lipid metabolism and prostate cancer growth

De novo fatty acid (FA) synthesis is required for prostate cancer (PCa) survival and progression. As a key enzyme for FA synthesis fatty acid synthase (FASN) is often overexpressed in human prostate cancers and its expression correlates with worse prognosis and poor survival. P300 is an acetyltransferase that acts as a transcription co-activator. Increasing evidence suggests that P300 is a major PCa promoter, although the underlying mechanism remains poorly understood. Here, we demonstrated that P300 binds to and increases histone H3 lysine 27 acetylation (H3K27Ac) in the FASN gene promoter. We provided evidence that P300 transcriptionally upregulates FASN expression and promotes lipid accumulation in human PCa cells in culture and Pten knockout prostate tumors in mice. Pharmacological inhibition of P300 decreased FASN expression and lipid droplet accumulation in PCa cells. Immunohistochemistry analysis revealed that expression of P300 protein positively correlates with FASN protein levels in a cohort of human PCa specimens. We further showed that FASN is a key mediator of P300-induced growth of PCa cells in culture and in mice. Together, our findings demonstrate P300 as a key factor that regulates FASN expression, lipid accumulation and cell growth in PCa. They also suggest that this regulatory pathway can serve as a new therapeutic target for PCa treatment.

Pituitary tumor-transforming gene 1 regulates invasion of prostate cancer cells through MMP13.

It is critical to understand the molecular mechanisms underlying the migration and invasiveness of prostate cancer (PC) for improving the outcome of therapy. A relationship of pituitary tumor-transforming gene 1 (Pttg1) and matrix metalloproteinase 13 (MMP13) in PC as well as their roles in the metastases of PC has not been studied. Here, we reported significantly higher levels of Pttg1 and MMP13 in the resected PC specimens, compared to the adjacent normal prostate tissue from the same patient. Interestingly, Pttg1 and MMP13 levels strongly correlated with each other. In vitro, Pttg1 activated MMP13, which determined PC cell invasiveness. However, Pttg1 levels were not significantly affected by MMP13. Furthermore, the Pttg1-activated MMP13 in PC cells was significantly suppressed by inhibition of PI3k/Akt, but not ERK/MAPK or JNK pathways. Together, our data suggest that Pttg1 may increase PC cell metastasis by MMP13, and highlight Pttg1/MMP13 axis as a promising therapeutic target for PC treatment.

AKT3 promotes prostate cancer proliferation cells through regulation of Akt, B-Raf, and TSC1/TSC2.

The qRT-PCR analysis of 139 clinical samples and analysis of 150 on-line database clinical samples indicated that AKT3 mRNA expression level was elevated in primary prostate tumors. Immunohistochemical staining of 65 clinical samples revealed that AKT3 protein expression was higher in prostate tumors of stage I, II, III as compared to nearby normal tissues. Plasmid overexpression of AKT3 promoted cell proliferation of LNCaP, PC-3, DU-145, and CA-HPV-10 human prostate cancer (PCa) cells, while knockdown of AKT3 by siRNA reduced cell proliferation. Overexpression of AKT3 increased the protein expression of total AKT, phospho-AKT S473, phospho-AKT T308, B-Raf, c-Myc, Skp2, cyclin E, GSK3β, phospho-GSK3β S9, phospho-mTOR S2448, and phospho-p70S6K T421/S424, but decreased TSC1 (tuberous sclerosis 1) and TSC2 (tuberous Sclerosis Complex 2) proteins in PC-3 PCa cells. Overexpression of AKT3 also increased protein abundance of phospho-AKT S473, phospho-AKT T308, and B-Raf but decreased expression of TSC1 and TSC2 proteins in LNCaP, DU-145, and CA-HPV-10 PCa cells. Oncomine datasets analysis suggested that AKT3 mRNA level was positively correlated to BRAF. Knockdown of AKT3 in DU-145 cells with siRNA increased the sensitivity of DU-145 cells to B-Raf inhibitor treatment. Knockdown of TSC1 or TSC2 promoted the proliferation of PCa cells. Our observations implied that AKT3 may be a potential therapeutic target for PCa treatment.

MiR-200b suppresses cell proliferation, migration and enhances chemosensitivity in prostate cancer by regulating Bmi-1

microRNAs (miRNAs) are a class of small non-coding RNAs that can post-transcriptionally regulate gene expression and play critical roles in many important biological processes. The role of miRNAs in prostate cancer (PCa) development and pathogenesis remains largely unknown. In the present study, we showed that miR-200b was downregulated in clinical prostatic tumors when compared to normal prostate tissue and in advanced PCa cell lines when compared to normal epithelial prostatic cells. Enforced miR-200b expression suppressed PCa cell proliferation and migration and enhanced chemosensitivity to docetaxel by targeting B-cell-specific Moloney murine leukemia virus insertion site 1 (Bmi-1). Bmi-1 was detected at higher levels in PCa, and knockdown of Bmi-1 showed similar effects as miR-200b overexpression in PCa cells. Moreover, we confirmed that these effects were correlated with increased levels of E-cadherin and P16 and a reduction in vimentin expression and expression of stem cell markers (CD44 and OCT4). These findings suggest that miR-200b plays vital roles as a tumor-suppressor by targeting Bmi-1 and may be a promising therapeutic target for PCa treatment.

Androgen Modulation of Coregulator Expression in Prostate Cancer Cells

Aberrant coregulator expression that occurs during prostate cancer (PCa) progression correlates with poor prognosis and aggressive disease. This has been attributed to the ability to regulate androgen receptor-mediated transcription. We have shown previously that the androgenic milieu regulates the expression of the coactivators p300 and FHL2, with severe consequences for PCa cell proliferation and androgen receptor transcriptional activity. To determine the extent of androgen dependency of coregulator genes, we designed a cDNA-mediated annealing, selection, extension, and ligation RNA profiling array that probes the expression of 186 coregulators. Using this assay, we demonstrated androgen control over approximately 30% of coregulator genes in PCa cells. For a subset of 15 functionally diverse coregulators, androgen regulation was confirmed using real-time RT-PCR and immunoblotting. The extent, dose dependency, and kinetics by which androgens affect coregulator expression differed widely, indicating diverse molecular mechanisms underlying these effects. Moreover, differences in coregulator expression were observed between isogenic androgen-dependent and castration-recurrent PCa cells. Small interfering RNA-mediated changes in coregulator expression had profound effects on cell proliferation, which were most pronounced in castration-recurrent cells. Taken together, our integrated approach combining expression profiling, characterization of androgen-dependent coregulator expression, and validation of the importance of altered coregulator expression for cell proliferation identified several potential novel therapeutic targets for PCa treatment.