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The increased expression of phosphatase of regenerating liver-3 (PRL‑3) has been shown to be associated with the aggressive and metastatic phenotype of different solid tumors. However, it is not known whether PRL‑3 plays a similar role in the progression of prostate cancer (PCa). In this study, immunoblot analysis of androgen receptor (AR)-positive PCa lines (LNCaP and LNCaP‑SF) revealed the constitutive cytoplasmic expression of PRL‑3, and stimulation with R1881 (AR agonist) rapidly increased the nuclear translocation of PRL‑3. The AR-negative cell lines exhibited negligible PRL‑3 expression, and the ectopic overexpression of PRL‑3 increased both the proliferative and invasive potential of PC3 and DU145 cells. In addition, we measured PRL‑3 protein expression in human prostate tumor sections. A high-density prostate tumor microarray (TMA) was immunostained to assess whether PRL‑3 expression and its subcellular localization (cytoplasmic and nuclear levels) is associated with the Gleason score (GS), Gleason grade (GG) and tumor stage (T-stage). Digital image analysis (DIA) revealed that PRL‑3 expression was significantly higher in the malignant cores, as compared to the non‑malignant areas. Increases in both total and nuclear PRL‑3 levels were also associated with a higher GS and GG. Metastatic tumors (T4‑stage) had lower cytoplasmic, but higher nuclear PRL‑3 levels. Furthermore, the nuclear/cytoplasmic ratio for PRL‑3 in the tumors graded as GS7 could effectively distinguish between indolent (3+4) and aggressive (4+3) disease. Thus, our experiments using PCa lines suggested that PRL‑3 is an AR-regulated gene and its androgen-induced nuclear localization may increase the aggressive behavior of PCa cells. Furthermore, the digital analysis of immunostained tumor sections suggested that PRL‑3 may be an effective biomarker of high-grade PCa, and its nuclear/cytoplasmic ratio may be used to distinguish between indolent vs. aggressive tumors.

Prostate cancer (PCa) cells utilize androgen for their growth. Hence, androgen deprivation therapy (ADT) using anti-androgens, e.g. bicalutamide (BIC) and enzalutamide (ENZ), is a mainstay of treatment. However, the outgrowth of castration resistant PCa (CRPC) cells remains a significant problem. These CRPC cells express androgen receptor (AR) and utilize the intratumoral androgen towards their continued growth and invasion. Sulforaphane (SFN), a naturally occurring isothiocyanate found in cruciferous vegetables, can decrease AR protein levels. In the present study, we tested the combined efficacy of anti-androgens and SFN in suppressing PCa cell growth, motility and clonogenic ability. Both androgen-dependent (LNCaP) and androgen-independent (C4-2B) cells were used to monitor the effects of BIC and ENZ, alone and in combination with SFN. Co-exposure to SFN significantly (p

The melanocortin receptors (MCRs 1-5) are G protein coupled-receptors (GPCRs) that regulate food intake, inflammation, skin pigmentation, sexual function and steroidogenesis. Their peptide ligands, the melanocortins, are α-, β- and γ-melanocyte-stimulating hormone and adrenocorticotropic hormone (ACTH) all of which are secreted from the anterior pituitary gland under hypothalamic control. MC2R binds ACTH but has no affinity for the other melanocortins and is, thereby, pharmacologically different from MCRs that bind those ligands. Evidence suggests that elevated GPCRs transactivate the androgen receptor (AR), the critical mediator of prostate cell growth, and consequently promote prostate cancer cell proliferation. It may be that reduced central melanocortin signaling is coincidental with reversal of prostate cancer cachexia, but no data are available on the expression of, or the role for, MCRs in prostate cancer. Here, we show that MCR (1-5) mRNAs are expressed in androgen-dependent LNCaP and androgen-independent PC3 and DU-145 human prostate cancer cell lines. Further, MC2R, the specific target of ACTH, is expressed in LNCaP, PC3 and DU-145 cells. Among the several synthetic MCR peptide ligands that we used, only ACTH promoted concentration-dependent cell proliferation in the three cell lines as shown by MTT cell proliferation assay. In LNCaP cells, the effect was additive with testosterone stimulation and was partially blunted with SHU9119, a non-selective MCR antagonist. In the same cells, ACTH induced cAMP production and increased AR nuclear labeling in immunocytochemical assays. Our observations suggest that MC2R is involved in prostate carcinogenesis and that targeting MC2R signaling may provide a novel avenue in prostate carcinoma treatment.

The prostate cancer (PCa) cell lines LNCaP, PC-3, and DU-145 express peroxisome proliferator-activated receptor γ (PPARγ) but its role in PCa is unclear. Thiazolidinediones (TZDs), a family of PPARγ activators and type 2 anti-diabetic drugs, exhibit anti-tumor apoptotic effects in human PCa cell lines. Likewise, pharmacological inhibitors of fatty acid synthase (FASN), a metabolic enzyme highly expressed in PCa, induce apoptosis in prostate and other cancer cells. Here, we show positive correlation between PPARγ and FASN protein in PCa cell lines and synergism between TZDs and FASN blockers in PCa cell viability reduction and apoptosis induction. Combined TZDs/FASN has enhanced anti-tumor properties in both androgen-dependent LNCaP and androgen-independent PC-3 and DU-145 cells when compared with single drug exposure. Low concentrations (5-10 μM) of the TZD drug rosiglitazone failed to alter cell viability but, paradoxically, upregulated lipogenic genes [PPARγ, FASN, sterol regulatory element binding protein-1c (SREBP-1c) and acetyl-Co A carboxylase-1 (ACC1)], which diminish the apoptotic effects of rosiglitazone. The mean IC50 in all cell lines was 45 ± 2 μM for rosiglitazone compared with significantly lower 5 ± 1 μM for rosiglitazone plus the FASN blocker cerulenin, and 10.2 ± 2 μM for rosiglitazone plus the cerulenin synthetic analog C75. The IC50 for the combined rosiglitazone and FASN blockers contrasts with the relatively higher IC50 for rosiglitazone (45 ± 2 μM), the TZD drug troglitazone (13 ± 2 μM), cerulenin (32 ± 1 μM), or C75 (26 ± 3 μM) when these drugs were used alone. In summary, this study shows proof-of-principle for combining FASN blockers and TZDs for PCa treatment.

Acquirement of multi-drug resistance by tumor cells represents a major obstacle in the management of prostate cancer. Such resistance was demonstrated in the androgen-independent DU-145 cells in response to paclitaxel and the mechanisms by which these cell develops resistance was not understood. The objective of this study was to examine whether abrogation of the constitutively active NF-kappaB in the chemoresistant, androgen independent DU-145 prostate cancer cells will enhance their sensitivity to cytototoxic agents. Inhibition of NF-kappaB by a dominant negative super-repressor IkappaB mutant adenoviral construct enhanced the apoptotic potentials of paclitaxel and rhTNF-alpha in these cells. Using reporter assays and RT-PCR analysis, we demonstrate that paclitaxel-induced cell death was associated with an increase in NF-kappaB activation and MDR-1 gene expression. Abrogation of these effects by the dominant negative IkappaB adenoviral construct suggests that induction and/or constitutive activation of NF-kappaB can block the paclitaxel-induced apoptotic signaling pathways in this cell line, possibly by increasing the expression of anti-apoptotic and MDR-1 gene products, leading to development of chemoresistance in these cells. We conclude that inhibition of NF-kappaB activation may have therapeutic implications for prostate cancer.

Acquirement of multi-drug resistance by tumor cells represents a major obstacle in the management of prostate cancer. Such resistance was demonstrated in the androgen-independent DU-145 cells in response to paclitaxel and the mechanisms by which these cell develops resistance was not understood. The objective of this study was to examine whether abrogation of the constitutively active NF-kappaB in the chemoresistant, androgen independent DU-145 prostate cancer cells will enhance their sensitivity to cytototoxic agents. Inhibition of NF-kappaB by a dominant negative super-repressor IkappaB mutant adenoviral construct enhanced the apoptotic potentials of paclitaxel and rhTNF-alpha in these cells. Using reporter assays and RT-PCR analysis, we demonstrate that paclitaxel-induced cell death was associated with an increase in NF-kappaB activation and MDR-1 gene expression. Abrogation of these effects by the dominant negative IkappaB adenoviral construct suggests that induction and/or constitutive activation of NF-kappaB can block the paclitaxel-induced apoptotic signaling pathways in this cell line, possibly by increasing the expression of anti-apoptotic and MDR-1 gene products, leading to development of chemoresistance in these cells. We conclude that inhibition of NF-kappaB activation may have therapeutic implications for prostate cancer.

We describe the effects of tumor necrosis factor alpha-related apoptosis inducing ligand (TRAIL) on the induction of apoptosis in two related prostate cancer cell lines, PC3AR and PC3Neo. TRAIL is a potent drug, which induces apoptosis preferentially in cancer cells. Treatment of prostate cancer cells, reduced survival by approximately 41% in PC3AR, but only approximately 18% PC3Neo were killed. Western analysis demonstrated that increased apoptotic response of PC3AR cells may be due to differential response of death receptors DR4, DR5 and decoy receptors DcR1 and DcR2. Caspases-8, -9, -3 and Bid were highly activated in PC3AR cells compared to PC3Neo. Furthermore, lower apoptotic response of PC3Neo was probably due to higher expression of NFkappaB. Blocking the function of NFkappaB by adenoviral infection of mutated IkappaB, increased apoptotic response confirming the influence of NFkappaB. Thus, we have demonstrated the role of NFkappaB in the differential response of prostate cancer cells to TRAIL.

We describe the effects of tumor necrosis factor alpha-related apoptosis inducing ligand (TRAIL) on the induction of apoptosis in two related prostate cancer cell lines, PC3AR and PC3Neo. TRAIL is a potent drug, which induces apoptosis preferentially in cancer cells. Treatment of prostate cancer cells, reduced survival by approximately 41% in PC3AR, but only approximately 18% PC3Neo were killed. Western analysis demonstrated that increased apoptotic response of PC3AR cells may be due to differential response of death receptors DR4, DR5 and decoy receptors DcR1 and DcR2. Caspases-8, -9, -3 and Bid were highly activated in PC3AR cells compared to PC3Neo. Furthermore, lower apoptotic response of PC3Neo was probably due to higher expression of NFkappaB. Blocking the function of NFkappaB by adenoviral infection of mutated IkappaB, increased apoptotic response confirming the influence of NFkappaB. Thus, we have demonstrated the role of NFkappaB in the differential response of prostate cancer cells to TRAIL.