Cell killing and radiosensitizing effects of atorvastatin in PC3 prostate cancer cells

Recent studies have indicated that autophagy may be one of the important pathways induced by ionizing radiation. Atorvastatin (statin), an inhibitor of 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase, may exhibit anticancer effects as an autophagy inducer. In our study, the cell killing and radiosensitizing effects of statin were analyzed in PC3 cell line. Activation of the autophagy pathway was analyzed using the GFP-LC3 assay and western blot to determine LC3-II expression. The radiosensitivity of PC3 cells was determined using the clonal survival assay, TUNEL assay, and the Annexin V apoptosis assay. The expression profiles of autophagy related genes were analyzed using a pathway specific real-time polymerase chain reaction (PCR) array. Autophagic response was induced in PC3 cells after exposure to statin and/or gamma rays. Inhibition of the autophagic process using small interfering RNAs (siRNA) targeting Atg7 and/or Atg12 significantly reduced radiosensitivity of PC3 cells. Statin also exhibited a significant apoptosis-inducing effect in PC3 cells, which can be partially suppressed by Atg7 siRNA. Cells treated with statin and gamma irradiation showed significantly reduced colony forming efficiency and increased number of Annexin V positive early apoptotic cells. Analysis of autophagy and its regulatory gene profile showed that the expressions of 22 genes out of 86 genes assessed were significantly altered in the cells exposed to combined treatment or statin alone. The data indicate that activation of the autophagy pathway may be responsible for apoptosis inducing effect of statin. Furthermore, combined treatment with radiation and autophagic inducer, such as statin, may be synergistic in inducing cell death of PC3 cells.     

Influence of genistein isoflavone on matrix metalloproteinase-2 expression in prostate cancer cells

We investigated the expression of matrix metalloproteinase (MMP)-2 in human LNCaP and PC3 prostate cancer cell lines in response to genistein exposure. Initially we studied the phytosensitivity of the cells to genistein using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay to determine percentage cell viability/inhibition and the terminal deoxynucleotidyl transferase-mediated fluorescein-dUTP nick end-labeling apoptosis assay to assess the type of cell death. The results revealed that genistein inhibited growth and proliferation in both PC3 (hormone-dependent) and LNCaP (hormone-independent) prostate cancer cell lines, that there was no significant difference in sensitivity to genistein between PC3 and LNCaP cells, and that the effect of genistein on the cells was dose- and time-dependent. The results also revealed that inhibition of cell growth in both PC3 and LNCaP cells was predominantly due to apoptotic cell death. These results were consistent with data in previous studies. This was followed by determination of the MMP-2 profile in response to genistein treatment. The results indicated a significant dose- and time-dependent inhibition of MMP-2 expression levels in both cells, with a highly significant negative correlation between MMP-2 levels and concentration of genistein. This is of phytotherapeutic significance in view of the pivotal role of MMP-2 expression in the pathogenesis of prostate cancer. Increasing expression of MMPs has been identified in many human cancers, including prostate cancer. Our findings indicate that genistein could be a potent therapeutic inhibitor of MMP-2 in line with current concepts of targeted treatment.     

Effects of Selenite and Genistein on G2/M Cell Cycle Arrest and Apoptosis in Human Prostate Cancer Cells

Combination of chemopreventive agents with distinct molecular mechanisms is considered to offer a potential for enhancing cancer prevention efficacy while minimizing toxicity. Here we report two chemopreventive agents, selenite and genistein, that have synergistic effects on apoptosis, cell cycle arrest, and associated signaling pathways in p53-expressing LNCaP and p53-null PC3 prostate cancer cells. We show that selenite induced apoptosis only, whereas genistein induced both apoptosis and G ₂ /M cell cycle arrest. Combination of these two agents exhibited enhanced effects, which were slightly greater in LNCaP than PC3 cells. Selenite or genistein alone upregulated protein levels of p53 in LNCaP cells only and p21 ^waf1 and Bax in both cell lines. Additionally, genistein inhibited AKT phosphorylation. Downregulation of AKT by siRNA caused apoptosis and G ₂ /M cell cycle arrest and masked the effects of genistein. Treatment with insulin-like growth factor I (IGF-I) elevated levels of total and phosphorylated AKT and suppressed the effects of genistein. Neither downregulation of AKT nor IGF-I treatment altered the cellular effects of selenite. Our study demonstrates that selenium and genistein act via different molecular mechanisms and exhibit enhanced anticancer effects, suggesting that a combination of selenium and genistein may offer better efficacy and reduction of toxicity in prostate cancer prevention.     

Lycopene differentially induces quiescence and apoptosis in androgen-responsive and -independent prostate cancer cell lines

BACKGROUND & AIMS: Lycopene has been credited with a number of health benefits including a decrease in prostate cancer risk. Our study investigates the molecular mechanism underlying anti-cancer activity of lycopene-based products in androgen-responsive (LNCaP) and androgen-independent (PC3) cells. METHODS: The effect of lycopene-based agents on prostate cancer growth and survival were examined using proliferation assays, bromodeoxyuridine incorporation and flow cytometric analysis of cellular DNA content. Biochemical effects of lycopene treatment were investigated by immunoblotting for changes in the absolute levels and phosphorylation states of cell cycle regulatory and signalling proteins. RESULTS: LNCaP and PC3 cells treated with the lycopene-based agents undergo mitotic arrest, accumulating in G0/G1 phase. Immunoblot screening indicated that lycopene's antiproliferative effects are likely achieved through a block in G1/S transition mediated by decreased levels of cyclins D1 and E and cyclin dependent kinase 4 and suppressed Retinoblastoma phosphorylation. These responses correlated with decreased insulin-like growth factor-I receptor expression and activation, increased insulin-like growth factor binding protein 2 expression and decreased AKT activation. Exposure to lycopene at doses as low as 10 nM for 48 h induced a profound apoptotic response in LNCaP cells. In contrast PC3 cells were resistant to apoptosis at doses up to 1 microM. CONCLUSIONS: Lycopene exposure can suppress phosphatidylinositol 3-kinase-dependent proliferative and survival signalling in androgen-responsive LNCaP and androgen-independent PC3 cells suggesting that the molecular mechanisms for the cytostatic and cytotoxic actions of lycopene involve induction of G0/G1 cell cycle arrest. This study supports further examination of lycopene as a potential agent for both the prevention and treatment of prostate cancer.     

阿魏蘑菇提取物对肿瘤细胞p53表达的影响

目的 探讨新疆阿魏蘑菇提取物对体外培养的肿瘤细胞p53蛋白表达的影响，从细胞凋亡角度研究其抗肿瘤机制。方法 采用肿瘤细胞体外培养技术及流式细胞技术，观察阿魏蘑菇不同剂量的水提物及醇提物对体外培养的4种肿瘤细胞p53蛋白表达的影响。结果 MTT实验结果显示，受试物对4种类型肿瘤细胞均具有较强的杀伤作用，尤其以0．1g／m1剂量组为明显；HT实验结果表明，经受试物处理后，4种类型肿瘤细胞均观察到细胞核固缩，DNA浓缩并向核膜靠拢形成浓染致密颗粒，并有典型凋亡小体出现。提示，受试物可能通过诱导肿瘤细胞凋亡而发挥抗肿瘤作用；流式细胞仪检测结果显示，受试物处理后，4种类型肿瘤细胞p53蛋白表达水平均有不同程度的上调，尤其以醇提物作用24h后对Q3细胞p53蛋白表达水平的影响最为明显。结论 阿魏蘑菇提取物中的各组分可协同作用诱导肿瘤细胞促凋亡基因的表达，从而达到抗肿瘤的目的，有关阿魏蘑菇通过何种途径提高p53蛋白表达水平尚待深入探讨。     

Delayed expression of apoptosis in X-irradiated human leukemic MOLT-4 cells transfected with mutant p53

The effects of X-rays on cell survival, apoptosis, and long-term response in the development of cell death as measured by the dye exclusion test were studied in human leukemic MOLT-4 cells (p53 wild-type) stably transfected with a mutant p53 cDNA expression vector. Cell survival, as determined from colony-forming ability, was increased in an expression level dependent manner, but the increase was partial even with the highest-expressing clone (B3). This contrasts with the prior observation that cell death and apoptosis in B3 are completely inhibited at 24 h after irradiation with 1.8 Gy of X-rays. The examination of B3 cells incubated for longer than 24 h after X-irradiation showed a delay in the induction of cell death and apoptosis. Western blot analysis revealed that the time required to reach the highest level of wild-type p53 protein in B3 was longer than the time in MOLT-4 and that the p53 may be stabilized by the phosphorylation at Ser-15. These results suggest that the introduction of mutant p53 into MOLT-4 merely delays the development of apoptosis, during which the cells could repair the damage induced by X-rays, and results in the partial increase in cell survival.     

Zyflamend, a unique herbal preparation with nonselective COX inhibitory activity, induces apoptosis of prostate cancer cells that lack COX-2 expression

Cyclooxygenase (COX) inhibitors have suppressive effects on several types of cancer cells including prostate cancer. In this study, we considered the potential COX-inhibitory activity of a unique anti-inflammatory herbal preparation (Zyflamend; New Chapter, Inc., Brattleboro, VT) and analyzed its effects on the human prostate cancer cell line LNCaP. COX inhibitory activity of Zyflamend was determined by a spectrophotometric-based assay using purified ovine COX-1 and COX-2 enzymes. Effects of Zyflamend on LNCaP cell growth and apoptosis in vitro were assessed by cell counting, Western blot detection of poly ADP-ribose polymerase (PARP) cleavage, and measurement of caspase-3 activity in treated and control cell extracts. Western blotting techniques were conducted to determine the effects of this herbal preparation on the expression of the cell signaling proteins, p21, androgen receptor (AR), phospho-protein kinase C (pPKC)(alpha/beta), and phospho (p)Stat3. The phospohorylation status of several signal transduction phosphoproteins was profiled using a high-throughput phosphoprotein screening assay in treated cells and compared to controls. Zyflamend dramatically decreased COX-1 and COX-2 enzymatic activity. Elevated p21 expression coincided with attenuated cell growth following treatment of LNCaP cells with Zyflamend. PARP cleavage fragments were evident, and caspase-3 activity was upregulated over the control indicating the ability of Zyflamend to induce apoptosis of these cells. Androgen receptor expression levels declined by 40%, and decreases were observed in the active forms of Stat3 and PKC(alpha/beta) in Zyflamend-treated LNCaP cells. Zyflamend inhibited both COX-1 and COX-2 enzymatic activities, suppressed cell growth, and induced apoptosis in LNCaP cells. However, our data suggests that the effects are likely due to COX-independent mechanisms potentially involving enhanced expression of p21 and reduced expression of AR, pStat3, and pPKC(alpha/beta).     

The Bioactive Compounds α-Chaconine and Gallic Acid in Potato Extracts Decrease Survival and Induce Apoptosis in LNCaP and PC3 Prostate Cancer Cells

We recently reported that colored potato extracts and an anthocyanin rich fraction suppressed lymph-node carcinoma of the prostate (LNCaP) and prostate cancer-3 (PC-3) prostate cancer cell proliferation and induced apoptosis via caspase-dependent and caspase-independent pathways. Chlorogenic acid, caffeic acid, gallic acid, catechin, malvidin, and glycoalkaloids (α-chaconine and solanine) have now been identified as the major bioactive components of potato, and their effects on LNCaP and PC-3 cell proliferation and apoptosis have been investigated. α-chaconine (5 μg/ml) and gallic acid (15 μg/ml) exhibited potent antiproliferative properties and increased cyclin-dependent kinase inhibitor p27 levels in both cell lines. Both α-chaconine and gallic acid induced poly [adenosine diphosphate (ADP)] ribose polymerase cleavage and caspase-dependent apoptosis in LNCaP cells; however, caspase-independent apoptosis through nuclear translocation of endonuclease G was observed in both LNCaP and PC-3 cells. α-chaconine and gallic acid activated c-Jun N-terminal protein kinase (JNK), and this response played a major role in induction of caspase-dependent apoptosis in LNCaP cells; whereas modulation of JNK and mitogen-activated protein kinase did not affect α-chaconine- and gallic acid-induced caspase-independent apoptosis. These results suggest that apoptosis induced by whole potato extracts in prostate cancer cell lines may be in part due to α-chaconine and gallic acid.     

Molecular mechanism of anti-prostate cancer activity of Scutellaria baicalensis extract

Scutellaria baicalensis is a widely used Chinese herbal medicine historically used in antiinflammatory and anticancer therapy. The goals of the study were to 1) determine its in vitro and in vivo anti-prostate cancer activity, 2) investigate its molecular mechanism directed at cell proliferation control including cyclooxygenase-2(COX-2) prostaglandin E2 (PGE2) and cyclins/cdks pathways, and 3) compare it with those of PC-SPES (PC stands for prostate cancer and spes is Latin for hope), a former herbal mixture for prostate cancer treatment of which S. baicalensis is a major constituent. Two human prostate cancer cell lines (LNCaP, androgen dependent, and PC-3, androgen independent) were assessed for growth inhibition. S. baicalensis exerted dose- and time-dependent increased growth inhibition in both cell lines. However, the PC-3 cells IC50 (50% growth inhibition concentration) were slightly more sensitive than LNCaP cells (IC50=0.15 mg/ml), although the former is androgen independent. S. baicalensis was more effective in inhibition of cell growth compared with PC-SPES (IC50=0.38 mg/ml for PC-3 cells). Significant reduction of PGE2 synthesis in both cells after treatment with S. baicalensis resulted from direct inhibition of COX-2 activity rather than COX-2 protein suppression. S. baicalensis also inhibited prostate-specific antigen production in LNCaP cells. Finally, S. baicalensis suppressed expression of cyclin D1 in LNCaP cells, resulting in a G1 phase arrest, while inhibiting cdk1 expression and kinase activity in PC-3 cells, ultimately leading to a G2/M cell cycle arrest. Animal studies showed a 50% reduction in tumor volume after a 7-wk treatment period. This study demonstrated that S. baicalensis may be a novel anticancer agent for the treatment of prostate cancer.     

Wine antioxidant polyphenols inhibit the proliferation of human prostate cancer cell lines

The effect of different wine antioxidant polyphenols (catechin, epicatechin, quercetin, and resveratrol) on the growth of three prostate cancer cell lines (LNCaP, PC3, and DU145) was investigated. A dose- and time-dependent inhibition of cell growth by polyphenols was found at nanomolar concentrations. The proliferation of LNCaP and PC3 cells was preferentially inhibited by flavonoids (catechin, epicatechin, and quercetin), whereas resveratrol was the most potent inhibitor of DU145 cell growth. Possible mechanisms of action were investigated: 1) The competition of polyphenols for androgen binding in LNCaP cells revealed significant interaction only in the case of high concentrations of quercetin, at least at five orders of magnitude higher than the concentrations needed for cell growth inhibition. All other phenols showed low interactions. 2) Oxygen species production after mitogen stimulation and H2O2 sensitivity of these cell lines did not correlate with the observed antiproliferative effects, ruling out such a mode of action. 3) NO production revealed two different patterns: LNCaP and DU145 cells produced high concentrations of NO, whereas PC3 cells produced low concentrations. Phorbol ester stimulation of cells did not reveal any additional effect in LNCaP and DU145 cells, whereas it enhanced the secretion of NO in PC3 cells. Polyphenols decreased NO secretion. This effect correlates with their antiproliferative action and the inhibition of inducible NO synthase. It is therefore proposed that the antiproliferative effect of polyphenols is mediated through the modulation of NO production. In conclusion, our data show a direct inhibitory effect of low concentrations of antioxidant wine phenols on the proliferation of human prostate cancer cell lines mediated by the production of NO, further suggesting potential beneficial effects of wine and other phenol-containing foods or drinks for the control of prostate cancer cell growth.     

Wine Antioxidant Polyphenols Inhibit the Proliferation of Human Prostate Cancer Cell Lines

The effect of different wine antioxidant polyphenols (catechin, epicatechin, quercetin, and resveratrol) on the growth of three prostate cancer cell lines (LNCaP, PC3, and DU145) was investigated. A dose- and time-dependent inhibition of cell growth by polyphenols was found at nanomolar concentrations. The proliferation of LNCaP and PC3 cells was preferentially inhibited by flavonoids (catechin, epicatechin, and quercetin), whereas resveratrol was the most potent inhibitor of DU145 cell growth. Possible mechanisms of action were investigated: 1) The competition of polyphenols for androgen binding in LNCaP cells revealed significant interaction only in the case of high concentrations of quercetin, at least at five orders of magnitude higher than the concentrations needed for cell growth inhibition. All other phenols showed low interactions. 2) Oxygen species production after mitogen stimulation and H²O²2 sensitivity of these cell lines did not correlate with the observed antiproliferative effects, ruling out such a mode of action. 3) NO production revealed two different patterns: LNCaP and DU145 cells produced high concentrations of NO, whereas PC3 cells produced low concentrations. Phorbol ester stimulation of cells did not reveal any additional effect in LNCaP and DU145 cells, whereas it enhanced the secretion of NO in PC3 cells. Polyphenols decreased NO secretion. This effect correlates with their antiproliferative action and the inhibition of inducible NO synthase. It is therefore proposed that the antiproliferative effect of polyphenols is mediated through the modulation of NO production. In conclusion, our data show a direct inhibitory effect of low concentrations of antioxidant wine phenols on the proliferation of human prostate cancer cell lines mediated by the production of NO, further suggesting potential beneficial effects of wine and other phenol-containing foods or drinks for the control of prostate cancer cell growth.     

新疆阿魏菇提取物对不同肿瘤细胞p53、fas基因表达的调节

目的 从细胞凋亡角度探讨新疆阿魏菇提取物抗肿瘤机制。方法 采用肿瘤细胞体外培养技术及RT—PCR技术，观察阿魏菇不同剂量的水提物及醇提物对体外培养的四种肿瘤细胞p53及fas基因表达的影响。结果 以β—actin的表达及表达量作为内对照，四种类型肿瘤细胞均出现不同程度的p53基因、fas基因表达水平的上调。结论 受试物可能通过诱导促进肿瘤细胞凋亡基因(p53基因、fas基因)的转录及表达，从而发挥抗肿瘤作用。     

前列腺癌PC3细胞中恢复Nkx3.1表达提高17β-雌二醇抗肿瘤作用

目的调查恢复同源转录因子Nkx3.1在前列腺癌PC3细胞中表达可否提高17β-雌二醇抗肿瘤作用。方法构建Nkx3.1真核表达质粒pc DNA3.1-Nkx3.1-His,转染PC3细胞获得稳定表达Nkx3.1细胞系。MTT分析Nkx3.1对PC3细胞增殖影响。进一步通过MTT分析细胞增殖、流式细胞仪分析细胞凋亡来验证恢复PC3细胞Nkx3.1是否可提高17β-雌二醇抗肿瘤作用。此外,Western blot分析在PC3细胞中单独使用17β-雌二醇或结合Nkx3.1对凋亡相关蛋白表达影响。结果 Nkx3.1真核表达质粒在PC3细胞中获得高表达。外源性Nkx3.1表达对PC3细胞增殖无明显影响,但可明显提高17β-雌二醇抗增殖作用及诱导细胞凋亡。进一步分析凋亡相关蛋白表达显示,结合Nkx3.1与17β-雌二醇可使bcl-2表达下降、bax表达升高、caspase-3激活、PARP劈裂片段增加。结论恢复PC3细胞Nkx3.1表达可明显提高17β-雌二醇抗肿瘤作用,提示在雌激素治疗激素抵抗前列腺癌中恢复Nkx3.1表达是一值得尝试方法。     

Enhanced induction of apoptosis by combined treatment of human carcinoma cells with X rays and death receptor agonists

The death receptors Fas and DR5 are known to be expressed not only in immune cells but also in various tumor cells. The aim of the present study was to determine whether X irradiation enhanced induction of apoptosis in Tp53 wild type and Tp53-mutated tumor cell lines treated with agonists against these death receptors. We showed that 5 Gy of X irradiation significantly up-regulated the expression of death receptors Fas and DR5 on the plasma membrane in gastric cancer cell lines MKN45 and MKN28, lung cancer cell line A549, and prostate cancer cell line DU145, and that subsequent treatments with agonistic molecules for these death receptors, Fas antibody CH11 and TRAIL, increased the formation of active fragment p20 of caspase 3 followed by the induction of apoptosis. This death-receptor-mediated apoptosis was independent of Tp53 status since MKN28 and DU145 were Tp53-mutated. The post-irradiation treatment of the cells with N-acetyl-L-cysteine (NAC) abolished the up-regulation of the expression of Fas and DR5 on the plasma membrane. NAC also attenuated the increase in the formation of p20 and the induction of apoptosis by agonistic molecules. These results suggested that the increase in the induction of apoptosis by combined treatment with X irradiation and CH11 or TRAIL occurred through a change of the intracellular redox state independent of Tp53 status in human carcinoma cell lines.