Yosuke Furuya

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.

High Fat Diet Reduces the Expression of Glutathione Peroxidase 3 in Mouse Prostate

High fat diets are known to be a risk factor for prostate cancer. In this study, we investigated the effect of high fat diet on mouse prostate gene expression.

Low-density lipoprotein receptors play an important role in the inhibition of prostate cancer cell proliferation by statins

Background There are some reports about the antitumor effects of statins in these days. Statins decrease the level of cholesterol in the blood by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Inhibition of this enzyme decreases intracellular cholesterol synthesis. Thus, the expression of low-density lipoprotein receptor (LDLr) is increased to import more cholesterol from the bloodstream. In this study, we assessed the effects of statins on the proliferation of prostate cancer cells, and studied the relationship between the expression of LDLr and the effects of statins. Methods Simvastatin was used in the experiments. We studied the effect of simvastatin on PC-3 and LNCaP cell proliferation using the MTS assay, and evaluated the expression of LDLr after administration of simvastatin by quantitative polymerase chain reaction and Western blotting. Intracellular cholesterol levels in the prostate cancer cells were measured after administration of simvastatin. Furthermore, small interfering RNA (siRNA) was used to knockdown the gene expression of LDLr. Results In PC-3 cells, simvastatin inhibited cell proliferation. In LNCaP cells, only a high concentration of simvastatin (100μM) inhibited cell proliferation. In LNCaP cells, the protein level of LDLr was increased by simvastatin. In PC-3 cells, the protein levels of LDLr were unregulated. In PC-3 cells, but not in LNCaP cells, intracellular cholesterol levels were significantly decreased by simvastatin. After knocking down LDLr expression by siRNA, intracellular cholesterol levels were decreased, and cell proliferation was inhibited by simvastatin in LNCaP cells. Conclusion Simvastatin inhibited prostate cancer cell growth by decreasing cellular cholesterol and could be more effective in androgen-independent prostate cancer, where there is loss of regulation of LDLr expression. LDLr was shown to play an important role in the statin-induced inhibition of prostate cancer cell proliferation. These results suggest that future studies evaluating the cholesterol-lowering effects of statin may lead to new approaches to the prevention and treatment of prostate cancer.

YM155 reverses rapamycin resistance in renal cancer by decreasing survivin

PurposeMammalian target of rapamycin inhibitor has exhibited promising anticancer activity for the treatment of renal cell carcinoma (RCC). However, many patients acquire resistance to therapeutic agents leading to treatment failure. The objective of this study was to determine whether treatment with YM155, a novel small molecule inhibitor of survivin, could reverse rapamycin resistance in a rapamycin-resistant RCC.MethodsWe induced a rapamycin-resistant clear cell carcinoma cell line (Caki-1-RapR). We showed that survivin gene expression was significantly up-regulated in Caki-1-RapR compared with that in its parent cells (Caki-1). Therefore, we hypothesized that targeting of survivin in Caki-1-RapR could reverse the resistant phenotype in tumor cells, thereby enhancing the therapeutic efficacy of rapamycin. We used both in vitro and in vivo models to test the efficacy of YM155 either as a single agent or in combination with rapamycin.ResultsIn Caki-1-RapR cells, YM155 significantly decreased survivin gene and protein expression levels and cell proliferation in a dose-dependent manner in vitro. In addition, YM155 treatment significantly reversed rapamycin resistance in cancer cells. In a nude mouse tumor xenograft model, YM155 significantly inhibited the growth of Caki-1-RapR tumor. In addition, YM155 significantly enhanced the antitumor effects of rapamycin in Caki-1-RapR tumor.ConclusionsOur results suggest a potentially novel strategy to use YM155 to overcome the resistance in tumor cells, thereby enhancing the effectiveness of molecular target therapy in RCC.

Clinical endocrinological evaluation of the gonadal axis (testosterone, LH and FSH) in prostate cancer patients switched from a GnRH antagonist to a LHRH agonist

ObjectivesTo investigate the levels of testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prostate-specific antigen (PSA) in prostate cancer patients before and after the switch from degarelix to leuprolide treatments.MethodsWe enrolled 40 treatment-naïve prostate cancer patients who were treated initially with degarelix and were later switched to leuprolide. The subjects were divided into three groups depending on when they were switched to leuprolide: the 3-month group (3m; switched after 84 days, n=10), the 2-month group (2m; 56 days, n=10), and the 1-month group (1m; 28 days, n=20). Patient symptoms and hormone levels were measured after switching therapy. The castration level was defined as a serum testosterone level ≤50 ng/dl.ResultsThirty-nine subjects (97.5%) achieved castration levels of testosterone (11±5.8 ng/dl) 2 weeks after degarelix was first administered, and the characteristics of these patients were investigated. Testosterone levels increased and exceeded the castration level in one subject each of the 3m (142 ng/dl), 2m (72 ng/dl), and 1m groups (63 ng/dl). All subjects achieved the castration level by day 5. In contrast to testosterone levels, the LH and FSH surge on day 2 was significantly higher in the 1m group than in the other groups. The clinical symptoms were not exacerbated before or after switching in any patients.ConclusionsA testosterone surge was observed in 8.3 % of the study patients; however, it was very short-lived and mild. LH and FSH levels were significantly higher 1 month after administration compared with 2 or 3 months after degarelix administration.

Simvastatin up-regulates annexin A10 that can inhibit the proliferation, migration, and invasion in androgen-independent human prostate cancer cells

Statins have recently been studied for their proapoptotic and antimetastatic effects. However, the exact mechanisms of their anticancer actions remain unclear. Using microarrays, we discovered up‐regulation of annexin A10 (ANXA10) in PC‐3 cells after simvastatin treatment. ANXA10 reportedly has antitumor effects. In this study, we evaluated the effects of simvastatin on ANXA10 signaling in androgen‐independent prostate cancer cells.

Simvastatin in combination with meclofenamic acid inhibits the proliferation and migration of human prostate cancer PC‑3 cells via an AKR1C3 mechanism

Statins have become of interest in research due to their anticancer effects. However, the exact mechanism of their anticancer properties remains unclear. The authors previously reported that statins decrease intracellular cholesterol levels in androgen-independent prostate cancer cells. In de novo androgen synthesis, cholesterol is the primary material and certain enzymes have important roles. The present study aimed to determine whether simvastatin alters the expression of androgen synthesis-associated enzymes in androgen-independent prostate cancer cells. A novel combination therapy of statins and other drugs that inhibit the overexpression of enzymes involved in androgen synthesis was explored. The cytotoxicity of simvastatin and meclofenamic acid was assessed in prostate cancer cells using MTS and migration assays. Testosterone and dihydrotestosterone concentrations in the culture medium were measured using liquid chromatography-tandem mass spectrometry. RAC-α-serine/threonine-protein kinase (Akt) phosphorylation was detected by western blot analysis. Following treatment with simvastatin, aldo-keto reductase family 1 member C3 (AKR1C3) expression increased in PC-3 (>60-fold) and LNCaP-LA cells, however not in 22Rv1 cells. Small interfering (si)RNA was used to clarify the effects of AKR1C3 expression. The reduction in AKR1C3 expression in PC-3 cells following siRNA transfection was not associated with basal cell proliferation and migration; however, treatment with simvastatin decreased cell proliferation and migration. The combination of simvastatin and meclofenamic acid, an AKR1C3 inhibitor, further enhanced the inhibition of cell proliferation and migration compared with treatment with either drug alone. Furthermore, treatment with simvastatin attenuated insulin-like growth factor 1-induced Akt activation; however, the combination of simvastatin and meclofenamic acid further inhibited Akt activation. These results suggest that the combination of simvastatin and meclofenamic acid may be an effective strategy for the treatment of castration-resistant prostate cancer.

Abstract B50: LDL receptor plays an important role in inhibition of prostate cancer cell proliferation by statin

Abstract Object: Statins have been studied for their proapoptic and antimetastatic effects, which may make them relevant to cancer prevention or treatment. Some studies have shown a decreased risk of developing cancer in general. Concerning prostate cancer, the anticancer effect of statins is controversial. In vitro, some reports showed that statins have biological activities which inhibit PC proliferation, lowering the raft cholesterol content and inhibition of cyclin-dependent-kinase- 2 activity. However, the exact mechanisms of their anticancer action are still unclear. Statins lower cholesterol by inhibiting the enzyme HMG-CoA reductase, which is the rate-limiting enzyme of the mevalonate pathway of cholesterol synthesis. In normal cells, a decrease of intracellular cholesterol level induces an expression of low-density lipoprotein receptor (LDLR). On the other hand, it is reported that the regulation of LDLR expression is lacking in androgen-independent prostate cancer. We assessed the effect of several statins on the proliferation of prostate cancer cells, and studied the relationship between the expression of LDLR and the effect of statins. Methods: Simvastain, lovastatin, NK104, fluvastatin, pravastatin were used for our experiments. We examined the effect of statins on LNCaP and PC-3 cell proliferations by MTS assay, and evaluated the expression of LDLR after administrations of statins by Western blotting. Intracellular cholesterol levels of LNCaP and PC-3 cells were measured after administration of simvastatin. Furthermore, small interfering RNA (siRNA) were used to knock down the gene expression of LDLR. Results: In both prostate cancer cell lines, lipophilic statins inhibited cell proliferations. But pravastatin, water-soluble statin, did not significantly inhibit cell proliferations. In PC-3 cells, low dose statins (1 μM) inhibited cell proliferation. Otherwise, in LNCaP cells, only high dose statins (100 μM) inhibited cell proliferation. In LNCaP cells, the protein expression of LDLR was increased after treatment of statins. On the other hand, In PC-3 cells, statin did not regulate the expression of LDLR. In PC-3 cells, intracellular cholesterol levels were significantly decreased by simvastatin, but not in LNCaP cells. After knocking down of LDLR expression by LDLR siRNA, cell proliferation was inhibited by 10 μM of simvastatin in LNCaP cells. Conclusion: Statins inhibited proliferation of PC-3 cells and LNCaP cells after transfection of LDLR siRNA. These findings suggested that LDLR plays an important role in inhibition of prostate cancer cell proliferation by statin, and statins could be more effective in androgen-independent prostate cancer which lacks an ability to regulate an expression of LDLR. Future studies on the effect of diet and lipid-modulating drugs may uncover new approaches for the prevention and treatment of prostate cancer. Citation Format: Yosuke Furuya, Yoshitaka Sekine, Hidekazu Koike, Hiroshi Matsui, Kazuhiro Suzuki. LDL receptor plays an important role in inhibition of prostate cancer cell proliferation by statin [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr B50.