PI3K/Akt signaling regulates p27(kip1) expression via Skp2 in PC3 and DU145 prostate cancer cells, but is not a major factor in p27(kip1) regulation in LNCaP and PC346 cells

BACKGROUND: We compared the involvement of PI3K/PTEN/Akt signaling in the regulation of the cell-cycle regulator p27(kip1) and investigated the mechanism of PI3K/PTEN/Akt modulation of p27(kip1) in the prostate cancer cell lines LNCaP, PC346, PC3, and DU145. METHODS: PI3K/PTEN/Akt signaling was manipulated by wortmannin or specific siRNA. The effects on PI3K/Akt downstream effectors and p27(kip1) expression were monitored on RNA and protein levels. RESULTS: PI3K/Akt inhibition in LNCaP and PC346 cells hardly affected p27(kip1) expression. As shown in LNCaP cells, p27(kip1) expression inversely correlated with Skp2 expression, but Skp2 was not regulated by Akt. Blocking PI3K/Akt signaling in PC3 cells resulted in decreased Skp2 protein expression and increased p27(kip1). Downregulation of PTEN in DU145 cells also showed PTEN/Akt-dependent regulation of Skp2 and p27(kip1). CONCLUSIONS: In PC3 and DU145 cells, Skp2 is the main determinant in the PI3K/Akt-dependent regulation of p27(kip1). In LNCaP and PC346 cells, PI3K/Akt signaling is not a major factor in p27(kip1) regulation.     

Long-term androgen-ablation causes increased resistance to PI3K/Akt pathway inhibition in prostate cancer cells

BACKGROUND: In advanced stages of prostate cancer, the phosphatidylinositol-3' kinase (PI3K)/Akt signaling cascade, one of the major survival pathways in the cell, is frequently constitutively activated due to mutation or loss of the tumor suppressor protein phosphatase and tensin homolog deleted on chromosome 10 (PTEN). Using cell culture models representing different tumor stages, we explored the effect of inhibition of this survival pathway on the induction of apoptosis. METHODS: Inhibition of the survival kinase Akt and induction of apoptosis was analyzed in androgen-insensitive DU145 and PC-3 cells, in androgen-responsive LNCaP, and in androgen-independent long-term androgen-ablated LNCaP-abl cells representing therapy-resistant prostate cancer cells. Activated Akt was determined by immunoblotting using a phospho-Akt specific antibody. Induction of apoptosis was analyzed employing annexing V and propidium iodide staining and flow cytometry and measurement of cleavage of the caspases substrate poly-ADP-ribose polymerase (PARP). RESULTS: IGF-1, EGF, and heregulin but not PDGF or activators of protein kinase A induced phosphorylation of Akt in DU145 cells and activation was completely blocked by the PI3K inhibitor LY294002. In the hormone-responsive prostate cancer cell line LNCaP that has a constitutively switched-on Akt kinase, LY294002 caused a dose- and time-dependent Akt inhibition, which was absent in long-term androgen-ablated LNCaP sublines. In agreement with the resistance to inhibition of the PI3K/Akt pathway, long-term androgen-ablated LNCaP sublines remained relatively resistant to induction of cell death by LY294002 or the cytotoxic drug etoposide. Inhibition of the PI3K/Akt pathway restored the sensitivity of long-term androgen-ablated cells to induction of apoptosis by a cytotoxic drug almost completely. CONCLUSION: These results suggest that long-term androgen ablation therapy for prostate cancer reinforces the PI3K/Akt pathway and impedes its inhibition thus contributing to increased resistance of tumor cells to induction of apoptosis. With regard to treatment of therapy-refractory prostate cancer, these findings suggest effectiveness of a combination of cytotoxic treatment and inhibition of the PI3K-Akt survival pathway in tumor cells after failure of androgen-ablation therapy.     

Efficacy of microtubule-active drugs followed by ketoconazole in human metastatic prostate cancer cell lines

PURPOSE: Once a relapse occurs following primary endocrine treatment, metastatic prostate cancer is one of the most therapy-resistant human neoplasms. Ketoconazole is used for complete androgen deprivation, and recent data suggest it has direct activity against prostate cancer cells. MATERIALS AND METHODS: LNCaP, DU145, and PC3 cells, human prostate cancer cell lines, and HL60, a human leukemia cell line, were lysed and soluble proteins were harvested. Cells were plated in 96-well flat bottom plates and then exposed to the pharmacological agents, ketoconazole, vinblastine and paclitaxel. DNA synthesis was monitored by 3H-thymidine incorporation. RESULTS: We demonstrate that ketoconazole exerts a cytostatic effect on a panel of human prostate cancer cell lines, with IC50 of 4 to 5 microg./ml., 12 microg./ml., and 25 microg./ml. for LNCaP, PC3/PC3M, and DU145 cells, respectively. On the other hand, using microtubule-active drugs, vinblastine and paclitaxel, we found that PC3M and PC3 cells were more resistant than either DU145 or LNCaP cells. This resistance was associated with a lesser degree of Raf-1 and Bcl-2 phosphorylation following exposure to microtubule-active drugs. Combinations of microtubule-active drugs with ketoconazole were a beneficial treatment in DU145 cancer cells. Furthermore, ketoconazole blocked recovery of all the prostate cancer cell lines following 24 hours-pulse treatment with vinblastine. CONCLUSION: Pulse-administration of vinblastine followed by continuous administration of ketoconazole warrants investigation in the treatment of hormone-independent metastatic prostate cancer.     

The survival effect of prolactin on PC3 prostate cancer cells

OBJECTIVES: Recent studies suggest a paracrine/autocrine loop involving prolactin (PRL) within the human prostate. The aims of this study were to determine the effects of PRL on the growth and survival of prostate cancer cells and the intracellular signalling mechanisms underlying such effects. METHODS: The effect of PRL on proliferation of LNCaP, PC3 and DU145 was assessed by Coulter counting. The effect of PRL on TRAIL-, staurosporine- and flavopiridol-induced apoptosis was assessed by Timelapse microscopy and Annexin V binding. The status of the PRL receptor (PRL-R) and Akt/PKB (protein kinase B) activity were assessed by Western blotting. RESULTS: All three cell lines expressed both the short and long forms of the PRL receptor. Although, no significant effect of PRL on the proliferation of these cells was found, PRL partially inhibited TRAIL-induced apoptosis in PC3 cells. PRL also enhanced the phosphorylation of Akt/PKB in these cells. CONCLUSIONS: PRL had no significant effect on the proliferation of PC3, DU145 and LNCaP, but inhibited TRAIL-induced apoptosis in PC3 cells, possibly via enhanced Akt/PKB phosphorylation in PC3 cells. Further investigations are underway to determine the survival effect of PRL on the other two prostate cancer cell line.     

Mitogenic and anti-apoptotic actions of adipocyte-derived hormone leptin in prostate cancer cells

OBJECTIVE

To investigate the proliferative and anti‐apoptotic effects of leptin on human prostate cancer cells, and the role of related signalling pathways in mediating these actions, as obesity is a possible risk factor for prostate cancer and leptin, an adipocyte‐derived hormone, has mitogenic action in various cell types.

MATERIALS AND METHODS

Two human prostate cancer cell lines, DU145 and PC‐3, were treated with leptin (5–100 ng/mL) for up to 48 h. Under serum‐free conditions, cell proliferation was measured using a colorimetric tetrazolium assay and apoptosis by an enzyme‐linked immunosorbent assay measuring cell death. Also, the phosphorylation of ERK1/2 and Akt was detected by Western blotting, and specific inhibitors of mitogen‐activated protein kinase (MAPK) (PD98059; 40 µm ) and phosphatidylinositol 3‐kinase (PI3‐K, LY294002; 40 µm ) were used to evaluate the role of these signalling pathways.

RESULTS

Leptin dose‐dependently increased the cell number in both cell lines for up to 48 h of incubation, the mean (sem ) percentage of the control being 189 (4.3)% for DU145 and 173 (7.5)% for PC‐3 (100 ng/mL leptin, 48 h; P < 0.01). Leptin also significantly reduced the number of apoptotic cells after 24 h of treatment, dose‐dependently caused ERK1/2 and Akt phosphorylation; pretreatment with inhibitors of MAPK and PI3‐K inhibited these responses.

CONCLUSION

These results show that chronic increases in leptin might enhance the growth of prostate cancer via the MAPK and PI3‐K pathways. Further studies are needed to investigate whether the ability of leptin to stimulate mitogenic/anti‐apoptotic signal transduction pathways could represent a target for anticancer drug discovery.     

熊果酸对前列腺癌细胞雄激素非依赖性的逆转作用

目的 探讨中药成分熊果酸对雄激素非依赖性前列腺癌(AIPC)的治疗作用及其机制.方法 应用熊果酸处理体外培养的人雄激素依赖性前列腺癌(ADPC)细胞株LNCaP和AIPC细胞株DU145,噻唑蓝(MTT)比色法检测细胞活性及对人工合成雄激素R1881的反应性,免疫细胞化学检测熊果酸对雄激素受体(AR)、糖皮质激素受体(GR)、前列腺特异性抗原(PSA)及成活因子HSP90和白细胞介素(IL)-6表达的影响,逆转录.聚合酶链反应(RT-PCR)检测熊果酸对DU145细胞AR mRNA表达的影响.结果 熊果酸对不同浓度雄激素下的LNCaP细胞均呈浓度和时间依赖性生长抑制,20 mg/L的熊果酸作用96 h对LNCaP细胞的抑制率近50%.0.1 nmoL/L的R1881为最适生长浓度,熊果酸作用后,LNCaP细胞生长的最适雄激素浓度上升了10倍;熊果酸对DU145细胞的生长有浓度和时间依赖性抑制效应,DU145细胞对AR阻断剂羟氟他胺缺乏反应,熊果酸作用同时再应用氟他胺比单纯熊果酸的作用更明显,对细胞抑制率明显上升.熊果酸作用后,LNCaP和DUl45细胞IL-6、HSF90表达均明显下降(P＜0.05),DU145细胞GR表达明显降低(P＜0.01),AR和PSA蛋白及AR mRNA出现再表达.结论 熊果酸能改善前列腺癌细胞对雄激素的反应性,使LNCaP细胞对雄激素的依赖性加强,并诱发了DU145细胞对雄激素的反应性,其部分机制是降低了GR、HSP90、IL-6的表达并促进AR再表达.     

Effects of androgens on telomerase activity in normal and malignant prostate cells in vitro

BACKGROUND: Recent studies have shown that sex hormones regulate telomerase activity in endometrium and breast tissues. The present study was designed to clarify the effects of androgen on telomerase activity in normal and malignant prostate cells. METHODS: Androgen-sensitive (LNCaP) and -independent (TSU-Pr1 and DU145) prostate cancer cell lines and normal prostate cells including basal cells were cultured in the presence or absence of 5alpha-dihydrotestosterone (DHT). RESULTS: Prostate cancer cell lines exhibited high telomerase activity, and normal prostate cells showed low activity. Short or prolonged androgen-deprivation reduced telomerase activity in LNCaP cells, and DHT induced telomerase activity at the G(1) phase of the cell cycle. DHT did not modulate telomerase activity in TSU-Pr1, DU145, and normal cells. CONCLUSIONS: LNCaP cells had an androgen-dependent pathway to activate telomerase, whereas TSU-Pr1 and DU145 cells as well as normal prostate cells had an androgen-independent pathway. These findings suggest that the regulatory mechanism of telomerase varies during the progression of prostate cancers.     

The potential role of purine-rich element binding protein (PUR) alpha as a novel treatment target for hormone-refractory prostate cancer

BACKGROUND: Hormonal therapy for advanced prostate cancer is typically effective at first, but almost all men suffer refractory disease which often is life threatening. The nuclear matrix comprises not only of the structural elements of the nucleus, but is associated with many components of the molecular machinery. Our aim is to find novel targets for the treatment of hormone-refractory prostate cancer (HRPC) by focusing on the composition of the nuclear matrix proteins (NMPs). METHODS: LN96 cells were established at our Institution after long-term culturing of LNCaP cells under androgen deprived conditions. The composition of NMPs of LNCaP cells and LN96 cells were analyzed by two-dimensional (2D) electrophoresis and spots differentially expressed were investigated by mass spectrometry for identification. Among the spots identified, we analyzed the potential functional role of the identified proteins in prostate cancer cells by establishing stable overexpressed cells. RESULTS: We found that purine-rich element binding protein (PUR)alpha was significantly repressed not only in NMPs but also in total protein and mRNA levels of LN96 cells in comparison to LNCaP cells under the same steroid deprived conditions. Moreover, PURalpha was decreased in its expression both at the protein and mRNA levels in the androgen-independent prostate cancer cell lines, PC3 and DU145 in comparison to LNCaP cells. Stably overexpressing PURalpha in PC3 and DU145 cells negatively regulates cell proliferation, resulting in decreases in PCNA expression. CONCLUSION: Further dissection of the role of PURalpha in cell growth regulation may reveal a novel target for HRPC.     

Immunohistochemistry and biochemistry in detection of androgen, progesterone, and estrogen receptors in benign and malignant human prostatic tissue.

The relative distribution of androgen (AR), progesterone (PR), and estrogen receptors (ER) was localized and estimated in human prostate tissue by immunohistochemistry in five normal tissue samples, in eight benign hyperplastic (BPH) samples, in nine primary cancers, and in seven prostate cancer metastases. Moreover, three prostatic cancer cell lines (LNCaP, DU 145, and PC 3) were analyzed. A comparison between the results obtained by radioligand binding assays and immunohistochemistry was performed for the AR and PR. Using immunohistochemistry, the AR was exclusively detected in the nuclei of both benign and malignant prostatic epithelial cells. The highest proportion of AR-positive cells was found in BPH and in prostate cancer metastases as compared with normal prostatic tissue. In a majority of the cases, the PR was only present in the nuclei of stromal cells. Benign hyperplastic prostates contained higher proportions of PR-positive cells as compared with primary carcinoma. PR was sparse in epithelial cells. ER-positive stromal cell nuclei were only detected in carcinomatous prostates. A few ER-positive epithelial cell nuclei were found in one sample each of a BPH and normal prostate. All cells from the androgen-dependent, LNCaP, cell line and a majority of the cells from the androgen-independent, DU 145, cell line were AR-positive. In contrast, the cells from the androgen-independent, PC 3, cell line were all AR-negative. All three cell lines were PR- and ER-negative. The radioligand binding technique detected the AR in extracts from both the cytosol and the nucleus. Again BPH contained higher amounts of AR as compared with normal prostatic tissue. The LNCaP cells contained high amounts of cytosolic AR while cells from the DU 145 and PC 3 cell lines lacked detectable AR as estimated by biochemical techniques. There seemed to be a discrepancy between biochemically measured and immunohistochemically estimated receptor content.     

Inhibitors of apoptosis proteins in prostate cancer cell lines

BACKGROUND: The caspases are the central executioners of apoptosis. The inhibitors of apoptosis proteins (IAPs) are a family of recently described caspase inhibitors. We hypothesised that tumor resistance to apoptosis could be due in part to IAP expression. METHODS: The expression of NAIP, cIAP-1, cIAP-2, XIAP, and survivin was investigated in the prostate cancer cell lines LNCaP, PC3, and DU145. RNase protection assays and Western blotting were used to assess RNA and protein expression. Apoptotic susceptibility was determined using etoposide and assessed by propidium iodide (PI) DNA incorporation using flow cytometry. RESULTS: DU145 and PC3 cells were more resistant to apoptosis than LNCaP cells. All the IAPs were identified in the cell lines with variation in IAP expression between different cell types. Immunohistochemistry demonstrated cIAP-1 expression in PC3 cells was nuclear, while the expression of cIAP-2 and XIAP was perinuclear. Growing LNCaP cells in charcoal-stripped or androgen-supplemented medium resulted in no alteration in IAP expression. CONCLUSIONS: This study characterises the expression of IAP in three of the most commonly used prostate cancer cells. IAP may make an important contribution to apoptotic resistance in patients with prostate cancer.     

Inactivation of the NF2 tumor suppressor protein merlin in DU145 prostate cancer cells

BACKGROUND: The neurofibromatosis 2 (NF2) tumor suppressor gene product merlin is an important regulator of contact-dependent cell proliferation. Phosphorylation of merlin at serine 518 (Ser518) by the Rac effector p21-activated kinase (PAK) inactivates merlin's growth suppressing function, and is regulated by cell-culture conditions, including cell density, cell/substrate attachment, and growth factor availability. We examined the regulation of merlin expression and merlin phosphorylation in prostate cancer cells. METHODS: Phosphorylation of merlin in five prostate cancer cell lines (LNCaP, DU145, PC3, 22RV1, and LAPC-4) was examined by Western blotting using anti-phospho-merlin (Ser518) antibody. The activity of PAK, an upstream regulator of merlin phosphorylation, was measured by Western blotting using phospho-PAK (Ser141) antibody. The effects of various cell-culture conditions on the phosphorylation levels of merlin and PAK were analyzed. RESULTS: Both merlin expression and phosphorylation were low in LNCaP, PC3, 22RV1, and LAPC-4 prostate cancer cells. In DU145 cells, total and phosphorylated merlin were abundant, but phosphorylation was not inhibited by high cell density, serum withdrawal, the addition of hyaluronic acid or inhibition of CD44 expression, all of which are reported to inhibit merlin phosphorylation in non-neoplastic cells. PAK activation was elevated in DU145 cells and the addition of a PAK-specific inhibitor peptide but not the Rac1-specific inhibitor NSC23766 inhibited both PAK and merlin phosphorylation. CONCLUSIONS: Merlin is inactivated in DU145 prostate cancer cells by PAK-mediated constitutive phosphorylation, identifying a novel mechanism of merlin inactivation in neoplastic cells.     

Inhibitory effects of digitalis on the proliferation of androgen dependent and independent prostate cancer cells

PURPOSE: Digitalis or cardiac glycosides have been noted to induce tumor static or oncolytic effects in various types of cancer. We evaluated the effects and underlying mechanisms of cardiac glycosides, including digoxin, digitoxin and ouabain, on the proliferation of hormone dependent and independent prostate cancer cell lines. MATERIALS AND METHODS: Cell proliferation of the 3 human prostate cancer cell lines LNCaP, DU145 and PC3 was measured by 3-(4,5-dimethylthiazol-2-yle)2,5-diphenyltetralozium bromide (Sigma Chemical Co., St. Louis, Missouri) colorimetric assay. The cytotoxic effects of digitalis on prostate cancer cells were determined by lactate dehydrogenase measurements of the culture medium. Intracellular Ca2+ was measured by a dual wavelength spectrometer system. The percent of apoptotic cells after digitalis treatment was measured by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling and flow cytometry. RESULTS: Digoxin, digitoxin and ouabain significantly inhibited the proliferation of LNCaP, DU145 and PC3 cells at a dose of 1 or 10 microM. after 1 to 4 days of culture. Cytotoxicity of digitalis on the DU145 and LNCaP cells was dose dependent but cytotoxicity was not obvious in PC3. Digitalis (1 microM.) significantly increased intracellular Ca2+ in LNCaP and DU145 after 12 hours of culture but PC3 cells needed a 24-hour treatment to show any effect. In the apoptosis measurement digitalis at a dose of 1 and 10 microM. also significantly increased the percent of apoptotic cells in the LNCaP, DU145 and PC3 cell lines. Normal control human glomerular epithelial cells showed no response to digitalis treatment at all tested doses. CONCLUSIONS: Digitalis may inhibit the proliferation of prostate cancer cell lines, although the 3 cell lines showed varied sensitivity to digitalis. These effects are possibly the result of a mechanism involving sustained elevation of the concentration of intracellular Ca2+ and of apoptosis.     

Resveratrol sensitizes androgen independent prostate cancer cells to death-receptor mediated apoptosis through multiple mechanisms

BACKGROUND: A critical factor in prostate cancer development and progression is the altered expression of apoptotic regulatory proteins which renders cells resistant to both hormone- and chemo-therapies. Resveratrol, a dietary component with chemopreventive properties has been reported to resensitize a variety of cancer cell types to apoptosis. In the current study, the ability of resveratrol pre-treatment to sensitize hormone refractory prostate cancer cell lines (PC-3 and DU145) to apoptosis and the mechanisms involved were investigated. METHODS: Apoptosis was assessed using several established parameters and protein expression was analyzed by Western blot and flow cytometry. IAP knockdown was achieved using RNAi while inhibition of Akt phosphorylation was achieved by pre-incubation with the PI3-kinase inhibitor LY294002. RESULTS: Pre-treatment with resveratrol sensitized PC-3 and DU145 cells to agents that specifically target death receptors (TRAIL, Fas, TNFalpha) but not agents that initiate apoptosis through other mechanisms (Etoposide, Paclitaxel, Tunicamycin, Thapsigargin). Resveratrol pre-treatment altered the expression of IAPs and Bax, and decreased Akt phosphorylation in PC-3 cells, leading to increased caspase activation and apoptosis. While knockdown of IAPs using siRNA did not mimic the effects of resveratrol, inhibition of Akt phosphorylation using LY294002 sensitized PC-3 cells to TRAIL induced apoptosis but not to etoposide or tunicamycin. CONCLUSION: Altering apoptotic susceptibility in advanced androgen independent disease requires manipulation of a broad signaling pathway. Use of resveratrol or inhibition of Akt phosphorylation may represent an important therapeutic approach in combination with conventional therapies for the treatment of prostate cancer.     

Expression of cyclin DI in human prostate cancer cell lines

Deregulation of cyclin expression has been found in many tumors. In this report, we studied expression of cyclin DI in three human prostate cancer cell lines: the androgen-dependent LNCaP and the androgen-independent PC3 and DU 145 cell lines. Northern blot analysis showed that DU145 and PC3 cells expressed more abundant cyclin DI than LNCaP cells. Southern blot analysis showed no evident gene amplification or rearrangement of cyclin DI in any of these cell lines. Serum starvation and replenishment were used in the cell culture to study the regulation of expression of cyclin DI. Cyclin DI mRNA expression was detected by Northern blot analysis when LNCaP cells grew in medium with serum but was not detected after serum withdrawal; however, cyclin DI mRNA was induced after serum was added. Cyclin DI mRNA expression by PC3 and DU 145 cells was detected both when they grew in medium with serum and after serum withdrawal, although expression decreased greatly after 24 hours in the PC3 cell line. Immunoprecipitation and immunohistochemical staining also showed that cyclin D I protein was always expressed in PC3 and DU 145 cells under different growth factor environment, whereas it decreased significantly in LNCaP cells deprived of serum and the level resumed again when serum was re-added. This suggests that expression of cyclin DI is regulated by exogenous growth factors in LNCaP cell line and becomes constitutive in PC3 and DU 145 cell lines.     

Preferential chemosensitization of PTEN-mutated prostate cells by silencing the Akt kinase

BACKGROUND: In prostate cancer, mutations of the phosphatase PTEN can activate the kinase cascade PI3K/Akt/mTOR which induces drug resistance. METHODS: Chemosensitization by siRNA targeting Akt was studied in HEK293 cells forced to express CA-Akt or kinase-dead DN-Akt. To decrease drug resistance, Akt was silenced with siRNA in human prostate DU-145 cell line expressing the normal PTEN or in LNCaP and PC3 cell lines expressing mutated-PTEN. Taxol was used for the chemosensitization studies. RESULTS: Silencing Akt in the drug-resistant CA-Akt cells efficiently sensitized cells to antitubule agents, whereas silencing drug-responsive DN-Akt cells did not. Only minor effects were obtained in wild-type HEK293 cells. Potentiation by siRNA of taxol cytotoxicity was significantly greater in mutated-PTEN cells than in prostate cells expressing wild-type PTEN. The apoptotic program induced by taxol was preferentially potentiated by Akt siRNA in PTEN-mutated cell lines as regards the DU-145 cell line. CONCLUSIONS: Silencing Akt in PTEN-mutated prostate cancer cells enhances the antitumor effects of taxol. No siRNA chemosensitization was obtained in prostate cells with wild type PTEN.     

Effects of bufalin and cinobufagin on the proliferation of androgen dependent and independent prostate cancer cells

BACKGROUND: Cardiac glycosides may induce oncolytic effects in cancers. This study was to evaluate bufalin and cinobufagin effects on the proliferation of prostate cancer cell lines named LNCaP, DU145, and PC3. METHODS: Cell proliferation was measured by MTT assay. The cytotoxic effects were determined by lactate dehydrogenase measurements. The intracellular calcium concentration ([Ca(2+)](i)) was measured by a dual-wavelength spectrometer system. TUNEL assay and flow cytometry were performed to measure percentage of apoptotic cells. A colorimetric assay was to measure caspases activities. RESULTS: Bufalin and cinobufagin inhibited proliferation of cancer cells at doses of 0.1, 1, or 10 microM after 2-4 days of culture. Cytotoxicity of bufalin and cinobufagin on the DU145 and LNCaP cells was dose-dependent. Bufalin or cinobufagin increased [Ca(2+)](i) and apoptosis in cancer cells after a 24-hr culture as well as caspase 3 activities in DU145 and PC3 cells and caspase 9 activities in LNCaP cells. CONCLUSIONS: Bufalin and cinobufagin may inhibit the proliferation of prostate cancer cell lines associated with sustained elevation of the [Ca(2+)](i) and that of apoptosis.     

Monomethylated selenium inhibits growth of LNCaP human prostate cancer xenograft accompanied by a decrease in the expression of androgen receptor and prostate-specific antigen (PSA)

OBJECTIVES: Epidemiological studies and prevention trials suggest selenium is a promising preventive agent for prostate cancer. Selenium-containing compounds inhibited the growth of prostate cancer cell lines including androgen sensitive LNCaP and androgen insensitive DU145 and PC3 cells in vitro. Previous study revealed a novel mechanism of selenium action in which selenium (methylseleninic acid (MSA)) markedly reduced androgen receptor (AR) signaling in prostate cancer cells, suggesting that selenium might act as an antiandrogen, which could serve as a therapeutic agent for prostate cancer. In this study, we tested whether selenium (methylselenocysteine (MSC)) affects tumor growth of human prostate cancer cells by targeting AR signaling in vivo. METHODS: Prostate tumor xenografts were established in nude mice by co-inoculating LNCaP cells with Matrigel. The mice-bearing tumors were treated with or without MSC (100 microg/mouse/day) via intraperitoneal injection for 2 weeks. The effect of MSC on tumor growth, AR, and prostate-specific antigen (PSA) expression was examined. RESULTS: Methylselenocysteine (MSC) significantly inhibited LNCaP tumor growth (P < 0.05). AR expression in tumor tissues and serum PSA levels were considerably decreased in MSC-treated mice compared to the vehicle controls. CONCLUSIONS: Pharmacological dose of MSC inhibits the growth of LNCaP human prostate cancer in vivo accompanied by a decrease in the expression of AR and PSA. These findings suggest that selenium (MSC) can serve as a therapeutic agent aimed at disruption of AR signaling for prostate cancer.     

Prostate stromal cell-derived hepatocyte growth factor induces invasion of prostate cancer cell line DU145 through tumor-stromal interaction.

BACKGROUND: In prostate cancer, several growth factors derived from stromal cells regulate tumor cell growth. Hepatocyte growth factor (HGF) possesses biological activities that promote cancer proliferation and invasion through tumor-stromal interaction. We examined how prostate stromal cell-derived HGF affects invasion of prostate cancer cells through this interaction. METHODS: The effects of HGF, various growth factors (transforming growth factor (TGF)-alpha, TGF-beta1, basic fibroblast growth factor, keratinocyte growth factor, and platelet-derived growth factor), and conditioned medium (CM) from prostate stromal cells (PrSC) on prostate cancer cells (LNCaP, PC-3, and DU145) were determined by collagen gel invasion assay. DU145 cells and PrSC were cocultured for Matrigel invasion chamber assay. Induction activity of CM from cancer cells to stimulate HGF production by PrSC was studied by the ELISA method and Western blotting. RESULTS: LNCaP and PC-3 cells did not respond to any of the factors examined. Invasion of DU145 cells into the collagen gel matrix was induced by HGF and TGF-beta1, but not by any of the other factors tested. When DU145 cells were cultured in CM from PrSC or cocultured with PrSC, the cells acquired invasive potential, and this invasion was inhibited by an antibody against HGF, but not against TGF-beta1. Native-type HGF production in PrSC was enhanced by some unknown inducer(s) produced by cancer cells. CONCLUSIONS: PrSC-derived HGF enhanced invasive activity of the prostate cancer cell line DU145 through tumor-stromal interaction, wherein DU145 cells secreted some HGF-inducer(s) for PrSC.