Hidekazu Koike

Genistein, a soy isoflavone, induces glutathione peroxidase in the human prostate cancer cell lines LNCaP and PC-3.

Genistein is a major component of soybean isoflavone and has multiple functions resulting in antitumor effects. Prostate cancer is 1 of the targets for the preventive role of genistein. We examined the effect of genistein on human prostate cancer (LNCaP and PC‐3) cells. Proliferation of both cell lines was inhibited by genistein treatment in a dose‐dependent manner. To obtain the gene expression profile of genistein in LNCaP cells, we performed cDNA microarray analysis. The expression of many genes, including apoptosis inhibitor (survivin), DNA topoisomerase II, cell division cycle 6 (CDC6) and mitogen‐activated protein kinase 6 (MAPK 6), was downregulated. Expression levels were increased more than 2‐fold in only 4 genes. The glutathione peroxidase (GPx)‐1 gene expression level was the most upregulated. Quantitative real‐time polymerase chain reaction revealed significant elevation of transcript levels of GPx‐1 in both LNCaP and PC‐3 cells. Upregulation of gene expression levels accompanied elevation of GPx enzyme activities. In contrast, no significant changes were observed in the gene expression levels and enzyme activities of the other antioxidant enzymes, superoxide dismutase and catalase. GPx activation might be one of the important characteristics of the effects of genistein on prostate cancer cells.

Regulation of metallothionein and zinc transporter expression in human prostate cancer cells and tissues.

Prostate glands contain heavy metals such as zinc and cadmium, and epidemiological studies showed that both metals were associated with prostate cancer development. To understand the heavy metal metabolism in prostate glands, we investigated the regulation of metallothionein (MT), metal-responsive promoter element-binding transcription factor (MTF) and zinc transporter (ZnT) in human prostate cells and tissues. Growth of human prostate cancer cells, LNCaP and PC-3 cells, was suppressed by zinc or cadmium treatment in a dose-dependent manner. LNCaP cells expressed MT-1A, 1X and 2A mRNA, and PC-3 cells expressed MT-1X and 2A mRNA. Zinc or cadmium treatment up-regulated MTs, MTF-1 and ZnT-1 gene expression levels in both cell lines. In PC-3 cells, ZnT-1 protein was detected, and was up-regulated by the metal treatment. Human prostate cancer tissues expressed significantly lower levels of ZnT-1 gene in comparison with hyperplastic tissues. We demonstrated the ZnT-1 expression in human prostate for the first time. The present study showed that heavy metal-metabolizing proteins were involved in human prostate homeostasis, and that the metal metabolizing system might be different in malignant tissues.

Genetic polymorphisms of estrogen receptor alpha, CYP19, catechol-O-methyltransferase are associated with familial prostate carcinoma risk in a Japanese population.

Estrogen is one of the crucial hormones participating in the proliferation and carcinogenesis of the prostate glands. Genetic polymorphisms in the estrogen metabolism pathway might be involved in the risk of prostate carcinoma development. The authors evaluated the association between genetic polymorphisms in estrogen‐related enzymes and receptors and the risk of developing familial prostate carcinoma.

A p53 codon 72 polymorphism associated with prostate cancer development and progression in Japanese

An association between the Pro/Pro genotype of p53 codon 72 and a lower risk of prostate cancer in Caucasians was recently reported. However, the association of this polymorphism with prostate cancer risk in a Japanese population has not been clarified. We performed a case-control study consisting of 114 prostate cancer patients and 105 noncancer controls. Sixty-nine percent (79 of 114) of the patients had a positive family history. The genotypic frequencies in the controls were 39.0% for Arg/Arg, 54.3% for Arg/Pro and 6.7% for Pro/Pro; they were in Hardy-Weinberg equilibrium. When a comparison of the distribution of the p53 codon 72 polymorphism was made between patients with a first-degree family history and all control subjects, the adjusted odds ratios (ORs) for prostate cancer associated with the Arg/Arg, Arg/Pro and Pro/Pro genotypes were 1.00, 0.99 [95% confidence interval (CI) 0.53-1.88] and 2.80 (95% CI 1.04-7.53), respectively. When stratification of cases was performed based on clinical stage (localized or metastatic cancer) and pathological grade (a Gleason score of <7 or > or =7), there tended to be a greater number of patients with localized cancers among those patients with the Arg/Pro genotype than among those with the Arg/Arg genotype (overall cases: age-adjusted OR 0.36, 95% CI 0.13-1.00, p = 0.049; positive family history cases: age-adjusted OR 0.25, 95% CI 0.075-0.84, p = 0.025). In addition, there tended to be a greater number of patients with low-grade cancers among those with the Pro/Pro genotype than among those with other genotypes (overall cases: age-adjusted OR 0.41, 95% CI 0.13-1.30, p = 0.13; positive family history cases: age-adjusted OR 0.20, 95% CI 0.004-0.89, p = 0.035). The present findings suggest that the Pro/Pro genotype of p53 codon 72 played a role in prostate cancer susceptibility in a Japanese population. However, the Pro allele did not appear to worsen such clinical parameters as clinical stage or pathological grade.

Vitamin D receptor gene polymorphism in familial prostate cancer in a Japanese population

Aim: Vitamin D acts as an antiproliferative agent against prostate cells. Epidemiological study has shown that a low level of serum vitamin D concentration is a risk factor for prostate cancer. Vitamin D acts via vitamin D receptor (VDR), and an association of genetic polymorphisms of the VDR gene has been reported. In the current study, we examined the association of VDR gene polymorphisms with familial prostate cancer in a Japanese population.

Simvastatin inhibits the proliferation of human prostate cancer PC-3 cells via down-regulation of the insulin-like growth factor 1 receptor.

Recently, statins have been being studied for their proapoptic and antimetastatic effects. However, the exact mechanisms of their anticancer action are still unclear. Dolichyl phosphate is a nonsterol isoprenoid derivative in the mevalonate pathway that affects the expression of the Insulin-like growth factor 1 receptor (IGF-1R). IGF-1R activation is required for prostate cell proliferation; therefore, IGF-1R inhibitory agents may be of preventive and/or therapeutic value. In this study, the effects of simvastatin on IGF-1R signaling in prostate cancer PC-3 cells were examined. Simvastatin suppressed proliferation and induced apoptosis of PC-3, and the expression of IGF-1R was suppressed by simvastatin. Knockdown of IGF-1R by siRNA led to inhibition of proliferation of PC-3. Simvastatin also inhibited IGF-1-induced activation of both ERK and Akt signaling and IGF-1-induced PC-3 cell proliferation. Our results suggest statins are potent inhibitors of the IGF-1/IGF-1R system in prostate cancer cells and may be beneficial in prostate cancer treatment.

High Density Lipoprotein Induces Proliferation and Migration of Human Prostate Androgen Independent Cancer Cells by an ABCA1-dependent Mechanism

Androgen deprivation therapy for prostate cancer leads to a significant increase of high-density lipoprotein (HDL), which is generally viewed as beneficial, particularly for cardiovascular disease, but the effect of HDL on prostate cancer is unknown. In this study, we investigated the effect of HDL on prostate cancer cell proliferation, migration, intracellular cholesterol levels, and the role of cholesterol transporters, namely ABCA1, ABCG1, and SR-BI in these processes. HDL induced cell proliferation and migration of the androgen-independent PC-3 and DU145 cells by a mechanism involving extracellular signal-regulated kinase (ERK) 1/2 and Akt, but had no effect on the androgen-dependent LNCaP cell, which did not express ABCA1 unlike the other cell lines. Treatment with HDL did not significantly alter the cholesterol content of the cell lines. Knockdown of ABCA1 but not ABCG1 or SR-BI by small interfering RNA (siRNA) inhibited HDL-induced cell proliferation, migration, and ERK1/2 and Akt signal transduction in PC-3 cells. Moreover, after treatment of LNCaP cells with charcoal-stripped fetal bovine serum, ABCA1 was induced ∼10-fold, enabling HDL to induce ERK1/2 activation, whereas small interfering RNA knockdown of ABCA1 inhibited HDL-induced ERK1/2 activation. Simvastatin, which inhibited ABCA1 expression in PC-3 and DU145 cells, attenuated HDL-induced PC-3 and DU145 cell proliferation, migration, and ERK1/2 and Akt phosphorylation. In human prostate biopsy samples, ABCA1 mRNA expression was ∼2-fold higher in the androgen deprivation therapy group than in subjects with benign prostatic hyperplasia or pretreatment prostate cancer groups. In summary, these results suggest that HDL by an ABCA1-dependent mechanism can mediate signal transduction, leading to increased proliferation and migration of prostate cancer cells. Mol Cancer Res; 8(9); 1284–94. ©2010 AACR.

Association of the genetic polymorphism in cytochrome P450 (CYP) 1A1 with risk of familial prostate cancer in a Japanese population: a case-control study

Association between genetic polymorphisms of CYP1A1 and familial prostate cancer risk was examined by a case-control study of 185 individuals. Although the individual analysis of m1 or m2 genotype of CYP1A1 showed no significant association with prostate cancer risk, the presence of any mutated alleles significantly increased prostate cancer risk in comparison with wild-type genotypes by combination analysis (odds ratio [OR]=2.38; 95% confidence interval [CI]=1.72-3.29; P=0.0069). Furthermore, metastatic cancer had a significant association with mutated alleles of m1 and m2. These finding suggested that CYP1A1 polymorphisms has an association with prostate cancer risk, especially with progression of prostate cancer.

Gene expression of survivin and its spliced isoforms associated with proliferation and aggressive phenotypes of prostate cancer.

OBJECTIVES To assess the effect of survivin gene expression on the proliferation of prostate cancer (PCa) cells and study the association of suvivin and its spliced isoforms gene expression levels with the pathologic grade of PCa. METHODS Gene expression of survivin and its spliced isoforms in the LNCaP and PC-3 PCa cell lines was determined using reverse transcriptase-polymerase chain reaction. We knocked down the gene expression of survivin using small interfering RNA and assessed the cell proliferation using the MTS assay. Next, we quantified the gene expression levels of survivin and its isoforms in prostate biopsy samples (PCa, n = 37; benign prostatic hyperplasia, n = 13; PCa after androgen deprivation therapy, n = 12) using the quantitative real-time polymerase chain reaction method. RESULTS In PCa cells, survivin and survivin-2alpha and survivin-2B were expressed more than survivin-DeltaEx3. The decrease in survivin gene expression by transfection of siRNA was accompanied by the inhibition of cell proliferation of PCa cells (31% and 25% decreased in LNCaP and PC-3 cells, P <0.01). In the prostate biopsy samples, the survivin expression in PCa was significantly greater than that in BPH or PCa after androgen deprivation therapy (PCa, 1; BPH, 0.16; PCa after androgen deprivation therapy, 0.27; P <0.01). In the PCa samples, the survivin expression level was associated significantly with high-grade cancer (Gleason score 8 or 9; Gleason score 7 versus 8 or 9, 1 versus 2.00, respectively; P <0.05). The survivin-2B/survivin ratio in high-grade cancer was lower than that in low-grade (Gleason score 7) cancer (Gleason score 7 versus 8 or 9, 1 versus 0.69; P <0.10). CONCLUSIONS These findings suggest that survivin and its spliced isoforms have associations with PCa cell proliferation and aggressive phenotypes.

Rapamycin enhances docetaxel-induced cytotoxicity in a androgen-independent prostate cancer xenograft model by survivin downregulation.

BACKGROUND Docetaxel is a first-line treatment choice in castration-resistant prostate cancer (CRPC). However, the management of CRPC remains an important challenge in oncology. There have been many reports on the effects of rapamycin, which is an inhibitor of the mammalian target of rapamycin (mTOR), in the treatment of carcinogenesis. We assessed the cytotoxic effects of the combination treatment of docetaxel and rapamycin in prostate cancer cells. Furthermore, we examined the relationship between these treatments and survivin, which is a member of the inhibitory apoptosis family. METHODS Prostate cancer cells were cultured and treated with docetaxel and rapamycin. The effects on proliferation were evaluated with the MTS assay. In addition, we evaluated the effect on proliferation of the combination treatment induced knockdown of survivin expression by small interfering RNA transfection and docetaxel. Protein expression levels were assayed using western blotting. PC3 cells and xenograft growth in nude mice were used to evaluate the in vivo efficacy of docetaxel and its combination with rapamycin. RESULTS In vitro and in vivo, the combination of rapamycin with docetaxel resulted in a greater inhibition of proliferation than treatment with rapamycin or docetaxel alone. In addition, in vitro and in vivo, rapamycin decreased basal surviving levels, and cotreatment with docetaxel further decreased these levels. Transfection siRNA against survivin enhanced the cytotoxicity of docetaxel in PC3 cells. CONCLUSION The rapamycin-dependent enhancement of the cytotoxic effects of docetaxel was associated with the downregulation of survivin expression. Our results suggest that the combination of docetaxel and rapamycin is a candidate for the improved treatment of advanced prostate cancer.