Growth Of Prostate Carcinoma Cells Research Articles

MiR-96 promotes the growth of prostate carcinoma cells by suppressing MTSS1

Prostate carcinoma (PC) is one of the most common cancers for males. However, the molecular mechanisms of PC progression are still to be uncovered. MicroRNA (miRNA) has been shown to be associated with the initiation and progression of prostate cancer. Among the identified tumor-promoting miRNAs, miR-96 has been well established to contribute to PC by reducing FOXO1 expression. This study is aimed to study if miR-96 can promote the progression of PC through other pathways. Our data reinforced the finding that the level of miR-96 was higher in PC samples and cell lines than in non-cancerous tissues and normal prostate epithelial cells. In addition, serum miR-96 abundance was also found to be elevated in PC patients. Decreasing miR-96 expression was able to suppress the proliferation, clonogenicity, and invasion of PC cells. Overexpressing miR-96 led to increased proliferation and colony formation of normal prostate epithelial cells. miR-96 level was found to be inversely associated with the abundance of metastasis suppressor protein 1 (MTSS1) messenger RNA (mRNA), which has been proved to be a tumor suppressor for PC. Predictive analysis indicated that there was a potential miRNA response elements (MREs) located within 3'UTR of MTSS1 mRNA. The changes in miR-96 expression can affect the levels of MTSS1 both at mRNA and protein levels. miR-96 also suppressed the activity of luciferase reporter under the regulation of 3'UTR of MTSS1. Further studies showed that MTSS1 restoration accounted for the effect of miR-96 reduction on PC cells. The overexpression of a recombinant MTSS1 resistant against miRNA regulation was also demonstrated to abolish the transforming effect of miR-96 on prostate epithelial cells. Taken together, we found that miR-96 has a higher abundance in serum samples of PC patients than healthy controls, implying that it may be used as a prognostic marker. MTSS1 is a new authentic target of miR-96 in PC. The above findings suggested that targeting miR-96 may be a promising strategy for PC treatment.

Synergistic Impact of d‐δ‐Tocotrienol and Geranylgeraniol on the Growth and HMG CoA Reductase of Human DU145 Prostate Carcinoma Cells

d‐δ‐Tocotrienol and geranylgeraniol suppress the growth of diverse types of tumors in vitro and in vivo. Their growth‐suppressive effect is at least partially attributed to their impact on 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG CoA) reductase, the rate‐limiting enzyme in the mevalonate pathway that provides essential intermediates for the posttranslational modification of growth‐related proteins including RAS and nuclear lamins. d‐δ‐Tocotrienol blocks the processing and nuclear localization of sterol regulatory element binding protein 2, the transcriptional factor for HMG CoA reductase, while d‐δ‐tocotrienol and geranylgeraniol collaboratively enhance the proteasome‐mediated degradation of HMG CoA reductase. We hypothesize that these agents have synergistic inhibitory impact on cell growth based on their complementary mechanisms of action with HMG CoA reductase. d‐δ‐Tocotrienol (0 – 40 μmol/L) and geranylgeraniol (0 – 100 μmol/L) each induced concentration‐dependent suppression of the growth of human DU145 prostate carcinoma cells as measured by CellTiter 96® AQueous One Solution. Blends of the two agents synergistically suppressed the growth of DU145 cells, with combination index values in the range of 0.67–0.75. While 7.5 μmol/L d‐δ‐tocotrienol and 30 μmol/L geranylgeraniol individually had no impact on cell cycle distribution in DU145 cells, a blend of the agents at these concentrations induced cell cycle arrest at the G1 phase. The synergistic downregulation of the expression of HMG CoA reductase by 7.5 μmol/L d‐δ‐tocotrienol and 30 μmol/L geranylgeraniol was accompanied by a reduction in membrane RAS protein induced by the blend. Our finding lends further support to the cancer chemopreventive action of plant‐based diets and their isoprenoid constituents. Properly formulated isoprenoid combinations and their derivatives with complementary mechanisms may provide novel approaches in prostate cancer therapy.Support or Funding InformationTDA FFRP, TWU REP, and American River Nutrition, Inc.

Abstract 4009: Comparative microRNA profiling of prostate carcinomas with increasing tumor stage by deep-sequencing

Abstract Background: MicroRNAs (miRNAs) are short, non-coding RNAs that post-transcriptionally regulate gene expression and play an important role in tumorigenesis. Previous deep-sequencing identified the microRNA profile of prostate carcinoma (PCa) vs. non-malignant prostate tissue. As an extension of our recent analyses, we now compared organ-confined prostate tumors (pT2), tumors with extra capsular growth (pT3, pN0), and lymph node metastasizing (pN1) PCa relative to corresponding non-malignant prostate tissue and healthy prostate tissue. Material and Methods: We performed comparative miRNA expression profiling using deep sequencing of cDNA libraries. Potential target genes of deregulated miRNAs were identified by database analysis and subsequently validated in vitro using reporter gene constructs. miRNA and mRNA expression was determined using quantitative real-time PCR. Results: The miRNA expression from the healthy and non-malignant tissue is consistent with our previous findings, indicating a high fidelity of the method employed. Some miRNAs (miR-375, miR-148a, miR-141 and miR-21) are expressed at increasing levels with increasing tumor stage, while other miRNAs (miR-200b/c, miR-25, miR-17 or miR-93) are up-regulated only from organ-confined tumors (pT2) to tumors with extra-capsular growth (pT3) but then expressed at lower levels after the transition to lymph node metastasizing tumors (pN0 vs. pN1). The same trend was seen in qRT-PCR analysis but due to the limited sample number, no significance was reached. Interestingly, miR-375, found to be up-regulated in tumor vs. normal tissue, and miR-15a, found induced by sequencing in T2 and T3 tumors but not in lymph node metastasizing tumors, target the phosphatases PHLPP1 and PHLPP2, respectively. PHLPP1 and PHLPP2 dephosphorylate members of the AKT-family of signal transducers thereby inhibiting cell growth. Co-expression of miR-15a and miR-375 resulted in down-regulation of PHLPP1/2 and a strongly increased PCa cell growth. Conclusion: miRNA profiling of pT2 (pN0), pT3 (pN0), and lymph node metastasizing prostate carcinoma (pN1) by deep sequencing revealed clearly changed miRNA levels. Citation Format: Elke Nolte, Martin Hart, Sven Wach, Jaroslaw Szczyrba, Helge Taubert, Tilman Rau, Arndt Hartmann, Friedrich A. Grässer, Bernd Wullich. Comparative microRNA profiling of prostate carcinomas with increasing tumor stage by deep-sequencing. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4009. doi:10.1158/1538-7445.AM2015-4009

Silibinin Combination with Arsenic Strongly Inhibits Survival and Invasiveness of Human Prostate Carcinoma Cells

Effects of silibinin, a naturally occurring flavanone, on prostate carcinoma (PCa) cells in presence of arsenic are not known. Arsenic is clinically approved for leukemia treatment; however, studies are not enough to support its role in the management of solid tumors. In the present study, we observed that silibinin (100 µM) modulated the oxidative status of human PCa DU145 cells exposed to arsenic (0.5 or 5 µM) and inhibited cell growth and survival by primarily inducing autophagy and apoptosis. The silibinin–arsenic combination also inhibited the growth, survival, and clonogenic potential of 22Rv1 PCa cells. Silibinin with 0.5 or 5 µM arsenic induced G1 or G2/M phase arrest, respectively, and decreased the protein levels of CDK2, -4, and -6 and cyclin D1, D3, and E and increased CDK inhibitors p21 and p27. Arsenic alone increased cyclin B1 level and Cdc2 kinase activity which were reduced in silibinin combination. Cell motility and invasiveness along with expression of MMP-2 and vimentin were suppressed. Together, these in vitro findings suggest that in presence of arsenic, silibinin strongly inhibits tumorigenic and metastatic potential of PCa cells.

Association of increased levels of TGF-β1 and p14ARF in prostate carcinoma cell lines overexpressing Egr-1.

The present study examined the effect of the overexpression of early growth response gene (Egr-1) on transforming growth factor β-1 (TGF-β1) and p14ARF levels, in PC-3 and LNCaP prostate carcinoma cell lines. Amplification of EGR-1, TGF-β1 and p14ARF were observed in the two cell lines treated with different stimuli and resulted in a corresponding mRNA and protein expression. The downregulation of TGF-β1 and the attenuation of p14ARF expression by siRNA against Egr-1 predominantly suggested that TGF-β1 and p14ARF may be regulated by the transcription factor EGR-1. A marginal attenuation of cell growth in PC-3 and LNCaP prostate carcinoma cell lines overexpressing p14ARF was observed. Cells transfected with Egr-1 wild-type were able to grow and avoid cell cycle arrest and apoptosis in the presence or absence of p14ARF. In addition, EGR-1 stimulated the expression of TGF β-l as well as the accumulation of the p14ARF proteins. The results suggested that TGF-β1 and p14ARF activities in the presence of EGR-1 overexpression can exist independently of the presence of cells carrying a mutant p53 (PC-3 cells) or cells carrying a wild‑type p53 (LNCaP cells). Thus, the effect of EGR-1 on the growth of prostate carcinoma cells may occur through multiple mechanisms, but be independent of p53 expression control.

Comparative microRNA Profiling of Prostate Carcinomas with Increasing Tumor Stage by Deep Sequencing

MicroRNAs (miRNA) posttranscriptionally regulate gene expression and are important in tumorigenesis. Previous deep sequencing identified the miRNA profile of prostate carcinoma versus nonmalignant prostate tissue. Here, we generated miRNA expression profiles of prostate carcinoma by deep sequencing, with increasing tumor stage relative to corresponding nonmalignant and healthy prostate tissue, and detected clearly changed miRNA expression patterns. The miRNA profiles of the healthy and nonmalignant tissues were consistent with our previous findings, indicating a high fidelity of the method employed. In the tumors, quantitative real-time PCR (qRT-PCR) analysis of 40 paired samples of prostate carcinoma versus normal tissue revealed significant upregulation of miR-20a, miR-148a, miR-200b, and miR-375 and downregulation of miR-143 and miR-145. Hereby, miR-375 increased from normal to organ-confined tumors (pT2 pN0), slightly decreased in tumors with extracapsular growth (pT3 pN0), but was then expressed again at higher levels in lymph node metastasizing (pN1) tumors. The sequencing data for miR-375 were confirmed by Northern blotting and qRT-PCR. The regulation for other selected miRNAs could, however, not be confirmed by qRT-PCR in individual tumor stages. MiR-200b, in addition to miR-200c and miR-375 reduced the expression of SEC23A. Interestingly, miR-375, found by sequencing in pT2 upregulated by us and others in tumor versus normal tissue, and miR-15a, found by sequencing in pT2 and pT3 and in the metastasizing tumors, target the phosphatases PHLPP1 and PHLPP2, respectively. PHLPP1 and PHLPP2 dephosphorylate members of the AKT family of signal transducers, thereby inhibiting cell growth. Coexpression of miR-15a and miR-375 resulted in downregulation of PHLPP1/2 and strongly increased prostate carcinoma cell growth. These genomic data reveal relevant miRNAs in prostate cancer that may have biomarker and therapeutic potential.

A comparative study of glycoproteomes in androgen-sensitive and -independent prostate cancer cell lines

Prostate cancer is one of the most common malignancies in men and is predicted to be the second leading cause of cancer-related deaths. After 6–18 months, hormone ablation treatment results in androgen-independent growth of cancer cells, metastasis and progression. The mechanism of androgen-independent growth of prostatic carcinoma cells is still unknown. Identification of factors that facilitate the transition from androgen-dependent to independent states is crucial in designing future diagnostics and medication strategies. To understand the biochemical meaning of hormone dependency deprivation, glycoproteins enriched profiles were compared between DU145 (hormone non-responding) and LNCaP (hormone responding) prostate cancer cells. These results allow for anticipation on the important role of glycosylation in malignant transformation. Both Tn antigen and complex antennary N-oligosaccharides were recognized. Their occurrence might be involved in the development and progression of tumor, and failure of hormone ablation therapy. Among identified proteins in androgen-sensitive cells nucleolin (P19338) was found that is widely described as apoptosis inhibitor, and also transporter of molecules from the membrane to the cytoplasm or nucleus. In addition, 14-3-3 protein family (P27348, P31946, P61981, P63104, P62258, Q04917, and P31947) was investigated across available databases as it forms stable complexes with glycoproteins. Our studies indicate that isoforms: sigma and eta were found in androgen-dependent prostate cancer cells, while other isoforms were present in androgen non-responding cells. 14-3-3 binding partners are involved in cancer pathogenesis. These findings may contribute to a better understanding of prostate cancer tumorigenesis and to a more efficient prognosis and individual therapy in a future. However, it still remains to be revealed how important those changes are for androgen dependency loss in prostate cancer patients carried out on clinically relevant populations.

Prostate carcinoma cell growth-inhibiting hydrogel supports axonal regeneration in vitro

Prostate cancer is the most common malignant tumor in men. Radical prostatectomy, the most common surgical therapy, is typically accompanied by erectile dysfunction and incontinence due to severing of the axons of the plexus prostaticus. To date, no reconstructive therapy is available as the delicate network of severed nerve fibers preclude the transplantation of autologous nerves or synthetic tube implants. Here, we present an injectable hydrogel as a regenerative matrix that polymerizes in situ and thus, adapts to any given tissue topography. The two-component hydrogel was synthesized from a hydrolyzed collagen fraction and stabilized by enzymatic crosslinking with transglutaminase. Physical analysis employing osmolarity measurements and cryosectioning revealed an isotonic, microstructured network that polymerized within 2min and displayed pronounced adhesion to abdominal tissue. Cell culturing demonstrated the biocompatibility of the gel and a general permissiveness for various neuronal and non-neuronal cell types. No effect on cell adhesion, survival and proliferation of cells was observed. A chemotherapeutic drug was integrated into the hydrogel to reduce the risk of fibrosis and tumor relapse. Significantly, when the hydrogel was employed as a drug release depot in vitro, aversive fibroblast- and prostate carcinoma cell growth was inhibited, while axonal outgrowth from peripheral nervous system explants remained completely unaffected. Taken together, these results suggest that the gel's adequate viscoelastic properties and porous microstructure, combined with its tissue adhesion and neuritotrophic characteristics in the presence of a cell type-specific cytostatic, may constitute an appropriate hydrogel implant applicable to patients suffering from prostatectomy associated side effects.

LINE-1 ORF-1p functions as a novel androgen receptor co-activator and promotes the growth of human prostatic carcinoma cells

Widespread interest in the mechanism of transcriptional regulation by the androgen receptor (AR) has been stimulated by the finding that AR signaling is critically important in the progression of human prostate cancers. Co-factors, the co-repressors, or the co-activators are responsible for the regulation of AR activation. The pro-oncogene human Long Interspersed Nucleotide acid Element-1 (LINE-1) encodes LINE-1 ORF-1p and plays important roles in the development and progression of several human carcinomas. In this study, the results showed that LINE-1 ORF-1p increased the AR transcriptional activity and in turn enhanced the expression of prostate specific antigen (PSA) in the presence of R1881. A physical protein–protein interaction between the AR signaling and the LINE-1 ORF-1p was identified by the immunoprecipitation assays and GST pull-down assays. Furthermore, LINE-1 ORF-1p would function as a novel AR positive co-regulator through modulating its cytoplasm/nucleus translocation and the recruitment to the androgen response element in the PSA gene promoter. Our date also showed that the LINE-1 ORF-1p promoted the proliferation and anchor-independent growth of LNCaP (ligand dependent) and PC-3 (ligand independent) human prostatic carcinoma cells. By investigating a novel role of the LINE-1 ORF-1p in the androgen/androgen receptor signaling pathway regulation, our study identifies that LINE-1 ORF-1p may be a novel AR co-regulator and molecular target for human prostate carcinoma therapy.

Abstract 4903: D-alpha-tocopheryl polyethylene glycol succinate (TPGS) induces apoptosis and cell cycle arrest selectively in breast cancer cells by targeting aberrantly activated pathways engaging survivin signaling

Abstract D-alpha-tocopheryl polyethylene glycol succinate (TPGS) is a water-soluble derivative of natural vitamin E, formed by the esterification of vitamin E succinate with polyethylene glycol (PEG). TPGS is finding applications in nanoparticle formulations where it acts as an emulsifier and serves as a promising vehicle for the delivery of anticancer drugs with poor water solubility, bioavailability and cellular uptake. Furthermore, TPGS inhibited the growth of human prostate and lung carcinoma cells both in vitro and in vivo by promoting apoptosis. The objectives of the present study were to: a) determine if there are differences between normal and cancer cells in response to TPGS treatment and b) to elucidate the pathways leading to apoptosis. For this purpose we used multiple breast cancer cell lines as well as normal immortalized breast cells, in order to assess the ability of TPGS to induce cell death. In addition, we thoroughly investigated the mechanism of cell death induction in MDA-MB-231 cells and in MCF-7 cells. The results of our study clearly show that TPGS can effectively decrease cancer cell number by triggering apoptotic signaling pathways as well as by inducing G1-phase cell cycle arrest. In marked contrast, the cell number of “normal” immortalized MCF-10A and MCF-12F cell lines was not significantly affected by TPGS treatment. The decreased levels of full length PARP, in the presence and absence of the 89 kDa product, suggests that TPGS triggered both caspase -dependent and -independent pathways of programmed cell death, depending on the tissue context. Furthermore, we observed a decrease in the Bcl-2/Bax ratio and release of AIF and Endo G from the mitochondria to the cytoplasm in MCF-7 cells suggesting that these effectors are involved in the induction of caspase-independent apoptosis. The selective chemotherapeutic effects of TPGS may possibly be attributed to down regulation of the anti-apoptotic proteins Survivin and Bcl-2 that are overexpressed in most cancer cells. The inhibition of cell proliferation at G1 observed in MCF-7 and MDA-MB-231 cells may also relate to the two-fold decrease in Survivin mRNA and subsequent elimination of Survivin protein levels. In conclusion, our results show clearly that TPGS is selectively cytotoxic to cancer cells and suggest that this vitamin E derivative, in combination with other drugs, may be useful in the treatment of tumors that are resistant to caspase-activating therapeutic agents. The current use of TPGS as a vehicle for the delivery of anticancer drugs, and the insights gained from this study regarding its mode of apoptotic action provides unsurpassed opportunities for the “combination” cancer chemotherapy approach. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4903. doi:1538-7445.AM2012-4903

Abstract 3929: Differential targeting of androgen and glucocorticoid receptors induces ER stress and apoptosis in prostate cancer cells: A novel therapeutic modality

Abstract Androgen (AR) and glucocorticoid (GR) receptor signaling play opposing roles in prostate tumorigenesis: in prostate AR acts as an oncogene and GR is a tumor suppressor. Here we explored a novel strategy of simultaneous inhibition of AR and activation of GR signaling for prostate cancer treatment using non-steroidal AR/GR modulator Compound A (CpdA) in combination with proteasome inhibitor Bortezomib (BZ). We and others found that CpdA acts as anti-inflammatory anti-androgen. It inhibits basal and DHT-induced AR activity; does not induce GR dimerization and transactivation but induces GR transrepression via inhibition of several transcription factors, including NF-kB, AP-1, and others. We also previously reported that CpdA has high anti-PC potential (Yemelyanov et al., 2008). It is known that GR and AR are controlled by proteasomal degradation. Here we show that prolonged exposure of prostate carcinoma (PCa) cells PC3 (AR-/GR+), DU145 (AR-/GR+), LNCaP (AR+/GR-), and LNCaP-GR (AR+/GR+), to BZ caused AR degradation and GR accumulation. BZ enhanced CpdA ability to inhibit AR and to augment GR transrepression. We also found that CpdA+BZ cooperatively inhibited PCa cell growth and survival and induced endoplasmic reticulum stress (ERS) as was indicated by up-regulation of BIP/HSPA5, ATF2 phosphorylation and nuclear translocation, and by induction of downstream pro-apoptotic ERS effector CHOP/GADD153. In contrast, glucocorticoid fluocinolone acetate and androgen DHT down-regulated cytoplasmic and nuclear CHOP, pointing to the ability of the androgens and glucocorticoids to counteract ERS in PC cells. Using ChIP we showed that BIP/HSPA5 and CHOP regulation was due to effects of CpdA and CpdA+BZ on GR loading on their promoters. Since CHOP/GADD153 was differentially activated by CpdA and BZ+CpdA via GR, we analyzed its role in anti-cancer effect of CpdA+BZ. The cooperative CpdA+BZ growth suppression and induction of apoptosis were significantly stronger in LNCaP-GR-CHOP compared to LNCaP-GR cells with low endogenous CHOP expression. Growth suppression and apoptosis induction by CpdA+BZ were drastically diminished in LNCaP-GR-shCHOP cells with depleted endogenous CHOP. Finally, we found that AR and GR are abundant in advanced PCa from patients treated by androgen ablation and/or chemotherapy: 56% of carcinomas from treated patients expressed both receptors, and the other 27% expressed either GR or AR. Overall, our data validate the concept of dual AR/GR targeting in prostate cancer (PC), and suggest that BZ combination with dual-target steroid receptor modulator CpdA has high potential for PC therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3929. doi:1538-7445.AM2012-3929

The antioxidant phenylaminoethyl selenide reduces doxorubicin-induced cardiotoxicity in a xenograft model of human prostate cancer

Anthracyclines are potent anticancer agents, but cardiotoxicity mediated by free radical generation limits their clinical use. This study evaluated the anticancer activity of phenyl-2-aminoethyl selenide (PAESe) and its potential to reduce doxorubicin (DOX)-induced cardiotoxicity. Growth inhibitory effects of PAESe with DOX, and vincristine, clinically used anticancer agents, and tert-butylhydroperoxide (TBHP), a known oxidant, on the growth of human prostate carcinoma (PC-3) cells was determined. PAESe (⩽1μm) did not alter the growth of PC-3 cells, however, concomitant use of PAESe decreased the oxidative-mediated cytotoxicity of TBHP, but had limited effect on vincristine or DOX activity. Further, PAESe decreased the formation of intracellular reactive oxygen species from TBHP and DOX. The effect of PAESe on the activity of DOX was determined using a tumor (PC-3) xenograft model in mice. PAESe did not alter DOX antitumor activity and showed evidence of direct antitumor activity relative to controls. DOX treatment decreased mice body weight significantly, whereas concomitant administration of PAESe and DOX was similar to controls. Most importantly, PAESe decreased DOX-mediated infiltration of neutrophil and macrophages into the myocardium. These data suggest PAESe had in vivo antitumor activity and in combination with DOX decreased early signs of cardiotoxicity while preserving its antitumor activity.

Isolation, Structure, and Biological Activities of Fellutamides C and D from an Undescribed Metulocladosporiella (Chaetothyriales) Using the Genome-Wide Candida albicans Fitness Test

In a whole-cell mechanism of action (MOA)-based screening strategy for discovery of antifungal agents, Candida albicans was used, followed by testing of active extracts in the C. albicans fitness test (CaFT), which provides insight into the mechanism of action. A fermentation extract of an undescribed species of Metulocladosporiella that inhibited proteasome activity in a C. albicans fitness test was identified. The chemical genomic profile of the extract contained hypersensitivity of heterozygous deletion strains (strains that had one of the genes of the diploid genes knocked down) of genes represented by multiple subunits of the 25S proteasome. Two structurally related peptide aldehydes, named fellutamides C and D, were isolated from the extract. Fellutamides were active against C. albicans and Aspergillus fumigatus with MICs ranging from 4 to 16 μg/mL and against fungal proteasome (IC₅₀ 0.2 μg/mL). Both compounds showed proteasome activity against human tumor cell lines, potently inhibiting the growth of PC-3 prostate carcinoma cells, but not A549 lung carcinoma cells. In PC-3 cells compound treatment produced a G2M cell cycle block and induced apoptosis. Preliminary SAR studies indicated that the aldehyde group is critical for the antifungal activity and that the two hydroxy groups are quantitatively important for potency.

Inhibitory effects of megakaryocytic cells in prostate cancer skeletal metastasis

Prostate cancer cells commonly spread through the circulation, but few successfully generate metastatic foci in bone. Osteoclastic cellular activity has been proposed as an initiating event for skeletal metastasis. Megakaryocytes (MKs) inhibit osteoclastogenesis, which could have an impact on tumor establishment in bone. Given the location of mature MKs at vascular sinusoids, they may be the first cells to physically encounter cancer cells as they enter the bone marrow. Identification of the interaction between MKs and prostate cancer cells was the focus of this study. K562 (human MK precursors) and primary MKs derived from mouse bone marrow hematopoietic precursor cells potently suppressed prostate carcinoma PC-3 cells in coculture. The inhibitory effects were specific to prostate carcinoma cells and were enhanced by direct cell-cell contact. Flow cytometry for propidium iodide (PI) and annexin V supported a proapoptotic role for K562 cells in limiting PC-3 cells. Gene expression analysis revealed reduced mRNA levels for cyclin D1, whereas mRNA levels of apoptosis-associated specklike protein containing a CARD (ASC) and death-associated protein kinase 1 (DAPK1) were increased in PC-3 cells after coculture with K562 cells. Recombinant thrombopoietin (TPO) was used to expand MKs in the marrow and resulted in decreased skeletal lesion development after intracardiac tumor inoculation. These novel findings suggest a potent inhibitory role of MKs in prostate carcinoma cell growth in vitro and in vivo. This new finding, of an interaction of metastatic tumors and hematopoietic cells during tumor colonization in bone, ultimately will lead to improved therapeutic interventions for prostate cancer patients. © 2011 American Society for Bone and Mineral Research.

Effect of Capsaicin on Prostate Cancer Cells

In recent years, natural products have emerged as modulators of many cellular responses, with potential applications as therapeutic drugs in many disorders. Among them, capsaicin, the pungent agent in chili peppers, has been demonstrated to have a role as a tumor suppressor for prostate cancer. Capsaicin potently suppresses the growth of human prostate carcinoma cells in vitro and in vivo. The antiproliferative activity of capsaicin correlates with oxidative stress induction and apoptosis. Capsaicin also induces ceramide accumulation and endoplasmic reticulum stress in androgen-resistant prostate cells. In androgen-sensitive prostate cancer cells, capsaicin exerts a biphasic effect, promoting growth at low doses and inducing apoptosis at doses over 200 µM. This article will draw upon multiple lines of evidence to provide a comprehensive description on the current state of knowledge that implicates the effect of capsaicin on prostate cancer cells.

Mechanisms by Which Interleukin-6 Regulates Prostate-Specific Antigen Gene Expression in Prostate LNCaP Carcinoma Cells

Interleukin-6 (IL-6) is involved in regulation of cell growth and survival of prostate carcinoma cells. Previous studies suggest that IL-6 promotes prostate cancer progression through the induction of an androgen-independent response. In this study, we evaluated the mechanisms by which IL-6 regulates the gene expression of prostate-specific antigen (PSA) in human prostate LNCaP carcinoma cells. (3)H-thymidine incorporation assays revealed that IL-6 treatment inhibited the proliferation of LNCaP cells. Results of enzyme-linked immunosorbent assay (ELISA) and immunoblot assays indicated that IL-6 treatment enhanced PSA gene expression. Similar results were found in LNCaP cells that had been engineered to stably overexpress IL-6. Although forced overexpression of c-Myc-associated zinc finger protein (MAZ) induced PSA promoter activity, mutation of the MAZ response elements had little effect on IL-6-induced PSA promoter activity. Results from 5'-deletion reporter assays revealed that the effects of IL-6 appear to be mediated via an androgen enhancer region (24801 to 23933), which is dependent on the signal transducer and activator of the transcription 3 (STAT3) pathway, and a region located at 2193 to 241 base pairs upstream of the translational initiation site of the human PSA gene, which did not respond to androgen or STAT3. Results of reporter assays, immunoblot assays, and ELISA revealed that the heat shock protein 90 (Hsp90) inhibitors 17-allyamino-17-demethoxygeldanamycin and geldanamycin blocked IL-6-induced PSA gene expression. Those results suggest that IL-6 upregulates PSA gene expression and that Hsp90 plays a novel role in the activation of IL-6 on PSA gene expression in an androgen-independent manner.

Fibroblast Growth Factor Receptor 4 Regulates Tumor Invasion by Coupling Fibroblast Growth Factor Signaling to Extracellular Matrix Degradation

Aberrant expression and polymorphism of fibroblast growth factor receptor 4 (FGFR4) has been linked to tumor progression and anticancer drug resistance. We describe here a novel mechanism of tumor progression by matrix degradation involving epithelial-to-mesenchymal transition in response to membrane-type 1 matrix metalloproteinase (MT1-MMP, MMP-14) induction at the edge of tumors expressing the FGFR4-R388 risk variant. Both FGFR4 and MT1-MMP were upregulated in tissue biopsies from several human cancer types including breast adenocarcinomas, where they were partially coexpressed at the tumor/stroma border and tumor invasion front. The strongest overall coexpression was found in prostate carcinoma. Studies with cultured prostate carcinoma cell lines showed that the FGFR4-R388 variant, which has previously been associated with poor cancer prognosis, increased MT1-MMP-dependent collagen invasion. In this experimental model, knockdown of FGFR4-R388 or MT1-MMP by RNA interference blocked tumor cell invasion and growth in collagen. This was coupled with impaired phosphorylation of FGFR substrate 2 and Src, upregulation of E-cadherin, and suppression of cadherin-11 and N-cadherin. These in vitro results were substantiated by reduced MT1-MMP content and in vivo growth of prostate carcinoma cells after the FGFR4-R388 gene silencing. In contrast, knockdown of the alternative FGFR4-G388 allele enhanced MT1-MMP and invasive tumor cell growth in vivo and within three-dimensional collagen. These results will help to explain the reported association of the FGFR4-R388 variant with the progression and poor prognosis of certain types of tumors.

Shank-interacting protein–like 1 promotes tumorigenesis via PTEN inhibition in human tumor cells

Inactivation of phosphatase and tensin homolog (PTEN) is a critical step during tumorigenesis, and PTEN inactivation by genetic and epigenetic means has been well studied. There is also evidence suggesting that PTEN negative regulators (PTEN-NRs) have a role in PTEN inactivation during tumorigenesis, but their identity has remained elusive. Here we have identified shank-interacting protein-like 1 (SIPL1) as a PTEN-NR in human tumor cell lines and human primary cervical cancer cells. Ectopic SIPL1 expression protected human U87 glioma cells from PTEN-mediated growth inhibition and promoted the formation of HeLa cell-derived xenograft tumors in immunocompromised mice. Conversely, siRNA-mediated knockdown of SIPL1 expression inhibited the growth of both HeLa cells and DU145 human prostate carcinoma cells in vitro and in vivo in a xenograft tumor model. These inhibitions were reversed by concomitant knockdown of PTEN, demonstrating that SIPL1 affects tumorigenesis via inhibition of PTEN function. Mechanistically, SIPL1 was found to interact with PTEN through its ubiquitin-like domain (UBL), inhibiting the phosphatidylinositol 3,4,5-trisphosphate (PIP3) phosphatase activity of PTEN. Furthermore, SIPL1 expression correlated with loss of PTEN function in PTEN-positive human primary cervical cancer tissue. Taken together, these observations indicate that SIPL1 is a PTEN-NR and that it facilitates tumorigenesis, at least in part, through its PTEN inhibitory function.

Inhibition of Hsp90 activates osteoclast c-Src signaling and promotes growth of prostate carcinoma cells in bone

Hsp90 inhibitors are being evaluated extensively in patients with advanced cancers. However, the impact of Hsp90 inhibition on signaling pathways in normal tissues and the effect that this may have on the antitumor activity of these molecularly targeted drugs have not been rigorously examined. Breast and prostate carcinomas are among those cancers that respond to Hsp90 inhibitors in animal xenograft models and in early studies in patients. Because these cancers frequently metastasize to bone, it is important to determine the impact of Hsp90 inhibitors in the bone environment. In the current study, we show that, in contrast to its activity against prostate cancer cells in vitro and its inhibition of s.c. prostate cancer xenografts, the Hsp90 inhibitor 17-AAG stimulates the intraosseous growth of PC-3M prostate carcinoma cells. This activity is mediated not by a direct effect on the tumor but by Hsp90-dependent stimulation of osteoclast maturation. Hsp90 inhibition transiently activates osteoclast Src kinase and promotes Src-dependent Akt activation. Both kinases are key drivers of osteoclast maturation, and three agents that block osteoclastogenesis, the Src inhibitor dasatinib, the bisphosphonate alendronate, and the osteoclast-specific apoptosis-inducer reveromycin A, markedly reduced 17-AAG-stimulated tumor growth in bone. These data emphasize the importance of understanding the complex role played by Hsp90 in regulating signal transduction pathways in normal tissues as well as in cancer cells, and they demonstrate that drug-dependent modulation of the local tumor environment may profoundly affect the antitumor efficacy of Hsp90-directed therapy.

Geranylgeraniol suppresses the proliferation of murine melanoma cells and human prostate tumor cells

The rate‐limiting activity of the mevalonate pathway, 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG CoA) reductase, provides essential intermediates for the prenylation or dolichylation of growth‐related proteins including nuclear lamins, Ras and growth factor receptors. A diterpene geranylgeraniol accelerates HMG CoA reductase degradation and suppresses the growth of human liver, lung, ovary, pancreas, colon, stomach, and blood tumors. We evaluated geranylgeraniol in murine and human cells. Geranylgeraniol induced dose‐dependent suppression of the cell proliferation following 48 (murine B16 melanoma) or 72 (human DU145 prostate carcinoma) h incubations in 96‐well plates. Cell cycle arrest at the G1 phase, manifested by a dose‐dependent increase in G1/S ratio, and apoptosis detected by fluorescence microscopy following acridine orange and ethidium bromide dual staining, contribute to the growth suppression in DU145 cells. The impact of geranylgeraniol on B16 cell proliferation was attenuated by supplemental mevalonate. Geranylgeraniol also attenuated the growth of human LNCaP prostate carcinoma and PC‐3 prostate adenocarcinoma cells. Mouse 3T3‐L1 fibroblasts were more resistant than B16 cells to geranylgeraniol. The differential sensitivity between neoplastic and normal cells points to the potential application of geranylgeraniol to cancer prevention. TDA, TWU REP & Summer Stipend Award.