Retinoblastoma protein and CCAAT/enhancer-binding protein beta are required for 1,25-dihydroxyvitamin D3-induced monocytic differentiation of HL60 cells

Derivatives of vitamin D (deltanoids) are well known to have the ability to induce differentiation of a variety of malignant cells, including human leukemia cells, but the signaling pathways that lead to such an outcome are unclear. In this study we investigated the role of the retinoblastoma protein (pRb) and the CCAAT/enhancer-binding protein (C/EBP) beta in 1,25-dihydroxyvitamin D(3) (1,25D(3))-induced monocytic differentiation of human leukemia HL60 cells. It was found that in this system, pRb is up-regulated within 12 h of exposure to the inducer, and the kinetics of its increase parallel the appearance of the early markers of differentiation, CD14 and monocyte-specific esterase. The increase in pRb expression was accompanied by a similar increase in C/EBPbeta protein, and these two proteins coimmunoprecipitated, suggesting formation of a complex. Oligonucleotides antisense to pRb or C/EBPbeta (but not to C/EBPalpha) or containing the C/EBP-binding sequence ("decoys"), all inhibited 1,25D(3)-induced differentiation. Inhibition of signaling by vitamin D receptor or by mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase and c-Jun-NH(2)-terminal kinase pathways using pharmacological inhibitors ZK159222, PD98059, or SP600125, respectively, inhibited pRb and C/EBPbeta expression and differentiation in a coordinate manner. In contrast, inhibition of the p38MAPK pathway by SB202190 potentiated differentiation and the up-regulation of pRb and C/EBPbeta. We suggest that 1,25D(3) may signal monocytic differentiation of HL60 cells in a vitamin D receptor-dependent manner that includes activation of extracellular signal-regulated kinase and c-Jun-NH(2)-terminal kinase MAPK pathways, which then up-regulate pRb and C/EBPbeta expression and in turn initiate the differentiation process.     

The iroquois homeobox gene 5 is regulated by 1,25-dihydroxyvitamin D3 in human prostate cancer and regulates apoptosis and the cell cycle in LNCaP prostate cancer cells.

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the most active metabolite of vitamin D3, has significant antitumor activity in a broad range of preclinical models of cancer. In this study, we show that the Iroquois homeobox gene 5 (Irx5) is down-regulated by 1,25(OH)2D3 in human prostate cancer samples from patients randomly assigned to receive weekly high-dose 1,25(OH)2D3 or placebo before radical prostatectomy. Down-regulation of Irx5 by 1,25(OH)2D3 was also shown in the human androgen-sensitive prostate cancer cell line LNCaP and in estrogen-sensitive MCF-7 breast cancer cells. Knockdown of Irx5 by RNA interference showed a significant reduction in LNCaP cell viability, which was accompanied by an increase in p21 protein expression, G2-M arrest, and an increase in apoptosis. The induced apoptosis was partially mediated by p53, and p53 protein expression was increased as a result of Irx5 knockdown. Cell survival was similarly reduced by Irx5 knockdown in the colon cancer cell line HCT 116 and in MCF-7 breast cancer cells, each being derived from clinical tumor types that seem to be inhibited by 1,25(OH)2D3. Overexpression of Irx5 led to a reduction of p21 and p53 expression. This is the first report that Irx5 is regulated by 1,25(OH)2D3 in humans and the first report to show that Irx5 is involved in the regulation of both the cell cycle and apoptosis in human prostate cancer cells. Irx5 may be a promising new therapeutic target in cancer treatment.     

Vitamin D receptor and p21/WAF1 are targets of genistein and 1,25-dihydroxyvitamin D3 in human prostate cancer cells

We investigated mechanisms by which genistein and 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] act synergistically to inhibit the growth of the human prostate cancer cell line LNCaP. We demonstrate that 1,25(OH)(2)D(3) and genistein cooperate to up-regulate the vitamin D receptor protein by increasing the stability of the vitamin D receptor. Genistein and 1,25(OH)(2)D(3) also cooperate to up-regulate the levels of p21/WAF1 (p21). Small interfering RNA-mediated knockdown of p21 expression showed that p21 is essential for significant growth inhibition of LNCaP cells in response to either compound or their combination. We conclude that one mechanism of synergism between genistein and 1,25(OH)(2)D(3) is through genistein modulation of vitamin D signaling.     

The combined treatment of 1,25-dihydroxyvitamin D3 and a non-steroid anti-inflammatory drug is highly effective in suppressing prostate cancer cell line (LNCaP) growth

BACKGROUND: The active metabolite of vitamin D3, 1,25(OH)2D3, is known to possess anti-proliferative and pro-differentiative activities in prostate cancer (PCa) cells. However, its clinical use is limited because of the risk of hypercalcemia. Concurrent administration of lower doses of 1,25(OH)2D3 together with other anticancer drugs may help to overcome this obstacle and lead to an effective and tolerable therapy. In the present in vitro study, we investigated the combined anti-cancer effect of 1,25(OH)2D3 and ibuprofen, a well-known non-steroidal anti-inflammatory drug (NSAID) that is also recognized for its ability to reduce prostate cancer development. MATERIALS AND METHODS: An androgen-sensitive prostate cancer cell line (LNCaP), grown in medium containing androgen (5alpha-dihydrotestosterone (DHT)) or without it, was treated with 1,25(OH)2D3 or ibuprofen alone or with a combination of both drugs. The effects of the treatments on LNCaP cell proliferation, cell cycle and apoptosis were evaluated by the thymidine incorporation method, the propidium iodide method and ELISA, respectively. The unpaired t-test was used for statistical analysis. RESULTS: Simultaneous treatment of LNCaP cells grown without DHT with 10 nM 1,25(OH)2D3 and 0.2 mM ibuprofen decreased cell growth by 42% (p<0.001, compared to the control cells). This effect was found to be additive since each single drug reduced cell proliferation by only 24%. On the other hand, highly significant synergistic cell growth inhibition (67%, p<0.001) was achieved by combined treatment of 1,25(OH)2D3 and ibuprofen in DHT-stimulated LNCaP cells. This combined treatment was also found to be effective in decreasing the cell transition from G1- to S-phase (p<0.003) and effective in enhancing apoptosis. CONCLUSION: Although both 1,25(OH)2D3 and ibuprofen demonstrate in vitro anti-carcinogenic activities as a single drug treatment, the present results showed that the combined use of 1,25(OH)2D3 with ibuprofen is superior to treatment with a single drug.     

In vitro and in vivo inhibition of liver cancer cells by 1,25-dihydroxyvitamin D3

Inhibitory effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on the proliferation of a variety of cancer cell lines have been extensively reported. We have studied the effect of 1,25-(OH)2D3 (10(-11)-10(-6) M) on the proliferation of a number of human and rat liver cancer cell lines. Additionally, the effect of 1,25-(OH)2D3 (0.02-0.5 microg/kg per day) on the rate of growth of liver cancer cell line xenografts in nude mice was also investigated. In vitro, proliferation of Hep-3B, PLC/PRF/5, and SKHEP-1 cells was significantly inhibited by 1,25-(OH)2D3, while HTC and Novikoff cells were more resistant to the inhibitory effects of the drug. In vivo, treatment of SKHEP-1 tumor bearing nude mice with different doses of 1,25-(OH)2D3 significantly retarded tumor growth without the development of hypercalcemia.     

The influence of 1,25-dihydroxyvitamin D3 and 1,24-dihydroxyvitamin D3 on alphavbeta3 integrin expression in cancer cell lines

Integrins are cell-surface receptors engaged in important cancer invasion processes, such as adhesion, migration, proliferation and differentiation. The aim of this study was to evaluate the effect of 1,25-dihydroxyvitamin D3 (calcitriol) and its metabolite 1,24-dihydroxyvitamin D3 (PRI-2191) on alphavbeta3 integrin expression in various cancer cell lines. The expression levels of the beta3 and alphav integrins were reduced only in the WEHI-3 and LLC cell lines by the two compounds. Calcitriol or PRI-2191 treatment caused differentiation of WEHI-3 mouse leukemia cells, but apoptosis of LLC cells. WEHI-3 and LLC cells exposed to calcitriol or PRI-2191 lost their migratory and adhesive potentials. The inhibition of migratory potential was higher in the LLC cells than in the WEHI-3 cells and appeared to correlate with the increased down-regulation of alphavbeta3 integrin by calcitriol or PRI-2191. The observed in vivo effects (antitumor and antimetastatic) in mice bearing subcutaneously transplanted LLC cancer are possibly associated with inhibited migratory potential as a consequence of the lowered integrin expression caused by calcitriol or PRI-2191.     

Complex regulation of the fibroblast growth factor-binding protein in MDA- MB-468 breast cancer cells by CCAAT/enhancer-binding protein beta

The fibroblast growth factor-binding protein (FGF-BP) binds and activates fibroblast growth factors in the extracellular matrix, and can have a rate-limiting role in tumor angiogenesis. Here we demonstrate high levels of FGF-BP expression in invasive human breast cancer, relative to normal breast and in situ carcinoma, and in MDA-MB-468 human breast cancer cells. In these cells, FGF-BP was up-regulated by treatment with epidermal growth factor (EGF), dependent on protein kinase C and p38 mitogen-activated protein kinase signaling. Mutational analysis revealed that the activator protein 1 and CCAAT/enhancer binding protein (C/EBP) sites on the FGF-BP gene promoter were required for the EGF effect, whereas deletion of the C/EBP site resulted in a significant increase in promoter basal activity indicating a basal repressive control mechanism. These data suggest that the C/EBP site is a central regulatory element for the regulation of FGF-BP promoter activity in MDA-MB-468 cells. We found that MDA-MB-468 cells express high endogenous levels of both the activating (LAP) and repressive (LIP) isoforms of C/EBPbeta. Overexpression of C/EBPbeta-LAP in MDA-MB-468 cells resulted in a large 80-fold increase in FGF-BP promoter basal activity, which was reversed by coexpression of LIP. Gel-shift analysis revealed that four LIP- and LAP-containing complexes (a-d) bind to the C/EBP site. DNA binding of the LIP and LAP-containing c complex and the b complex in the presence of EGF was modulated by inhibition of p38 mitogen-activated protein kinase, suggesting a role for these complexes in the EGF induction of the FGF-BP promoter. This study suggests that along with its well-defined role in mammary gland development, C/EBPbeta may well play a role in the pathology of breast cancer, in particular in the control of angiogenesis in the invasive phenotype.     

Dairy intake and 1,25-dihydroxyvitamin D levels in men at high risk for prostate cancer

Objective  

Dairy food intake has been associated with prostate cancer in previous work, but the mechanism by which this occurs is unknown. Dairy calcium may suppress circulating levels of potentially cancer-protective 1,25-hydroxyvitamin D (1,25(OH)₂D). We examined the associations of dairy, milk, calcium, and vitamin D intake with plasma 1,25(OH)₂D levels among 296 men (194 black, 102 non-black) enrolled in a high risk program for prostate cancer from 10/96 to 10/07.     

Inhibition of human cancer cell growth by 1,25-dihydroxyvitamin D3 metabolites

Specific high-affinity 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] receptors, which can undergo hormone-dependent activation and nuclear localization, have been demonstrated in a wide variety of established human cancer cell lines and surgically obtained human cancer tissues. 1,25-(OH)2D3 has been reported by some workers to stimulate cancer cell replication at low "physiological" concentrations and by ourselves and others to inhibit at higher concentrations. We report here that 1,25-(OH)2D3 had a biphasic effect on the replication of two distinct human cancer cell lines, i.e., the breast cancer T-47D and the malignant melanoma MM96, an effect analogous to that of estrogens on the breast cancer cell line MCF-7. These inhibitory effects were accompanied by marked morphological changes. Furthermore, two known metabolites of 1,25-(OH)2D3, i.e., 1,24,25-trihydroxyvitamin D3 and 1,25,26-trihydroxyvitamin D3, which compete for binding to the 1,25-(OH)2D3 receptor, did not stimulate but were almost equipotent with 1,25-(OH)2D3 in inhibiting the replication of both cell lines. The stimulatory but not the inhibitory effect of 1,25-(OH)2D3 was abolished by cortisone. These 1,25-dihydroxyvitamin D3 metabolites show promise for the inhibition of cancer growth, analogous to the effect of estrogens and antiestrogens in breast cancer but with potential application in a much wider range of human cancers.     

Regulation of epidermal growth factor receptor levels by 1,25-dihydroxyvitamin D3 in human breast cancer cells

Specific, high affinity receptors for 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] have been demonstrated in human breast cancer cells. In addition, 1,25-(OH)2D3 has been shown to inhibit replication in some human breast cancer cell lines, although the mechanism(s) of this anti-tumor activity remain undefined. There is currently considerable interest in the role of autocrine growth factors in the control of breast cancer cell proliferation and the effects of steroid hormones on their production, receptor binding, and action. Since the epidermal growth factor (EGF) receptor mediates the effects of both EGF and the autocrine growth factor, alpha-transforming growth factor, we investigated the effect of 1,25-(OH)2D3 on EGF receptor levels in several human breast cancer cell lines. Preincubation of T-47D cells with 1,25-(OH)2D3 for 24 h resulted in a significant concentration-dependent decline in the specific binding of [125I]EGF. The effect was observed when EGF binding was assayed at either 0 or 37 degrees C, both before and after treatment with acid to remove receptor bound endogenous ligand. This indicated that the effect on [125I]-EGF binding was not due to effects of 1,25-(OH)2D3 on receptor internalization and degradation or receptor occupancy. The half-maximal inhibitory concentration of 1,25-(OH)2D3 was approximately 2 nM. The decrease in EGF binding was due to a decrease in receptor number from 2,900 sites/cell in control cultures to 2,330 and 1,730 sites/cell in cells treated for 24 h with 10(-8) and 10(-6) M 1,25-(OH)2D3, respectively. There was no change in the affinity of the receptor for EGF following treatment with 1,25-(OH)2D3 [Kd = 0.075 +/- 0.006 nM (+/- SEM) for control and Kd = 0.083 +/- 0.004 nM for treated cells]. Decreased EGF receptor levels were also achieved with a number of analogues of 1,25-(OH)2D3 in accordance with their affinities for the 1,25-(OH)2D3 receptor, i.e., potencies for decreasing EGF binding in T-47D cells were in the order: 1,25-(OH)2D3 greater than 1,24,25-trihydroxyvitamin D3 greater than 1,25,26-trihydroxyvitamin D3 greater than 24,25-dihydroxyvitamin D3 greater than or equal to 25-hydroxyvitamin D3. Specific, saturable EGF binding to MCF-7 cells was also reduced by 1,25-(OH)2D3 while binding to BT-20 and HBL-100 cells was unaffected by this treatment.(ABSTRACT TRUNCATED AT 400 WORDS)     

Antiapoptotic signaling in LNCaP prostate cancer cells: a survival signaling pathway independent of phosphatidylinositol 3'-kinase and Akt/protein kinase B

Constitutive activation of the phosphatidylinositol 3'-kinase (PI3 kinase)-Akt/protein kinase B (PKB) "survival signaling" pathway is a likely mechanism by which many cancers become refractory to cytotoxic therapy. In LNCaP prostate cancer cells, the PTEN phosphoinositide phosphatase is inactivated, leading to constitutive activation of Akt/PKB and resistance to apoptosis. However, apoptosis and inactivation of Akt/PKB can be induced in these cells by treatment with PI3 kinase inhibitors. Surprisingly, androgen, epidermal growth factor, or serum can protect these cells from apoptosis, even in the presence of PI3 kinase inhibitors and without activation of Akt/PKB, indicating the activity of a novel, Akt/PKB-independent survival pathway. This pathway blocks apoptosis at a level prior to caspase 3 activation and release of cytochrome c from mitochondria.     

Expression of a novel factor, com1, is regulated by 1,25-dihydroxyvitamin D3 in breast cancer cells

Tumor cells and their surrounding microenvironment produce a variety of factors that promote tumor growth and metastasis. We recently identified a nuclear factor, termed com1, that is up-regulated in human breast carcinoma cells on formation of experimental metastatic tumors and is assumed to act as a growth-promoting factor in breast cancer. 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] is a potent inhibitor of growth in breast cancer both in vitro and in vivo. We compared the growth-regulatory mechanisms of nontumorigenic and estrogen-dependent MCF-7 cells with those of the tumorigenic and tamoxifen-resistant subline MCF7/ LCC2 in the presence of 1,25(OH)2D3. Proliferation of MCF7/LCC2 cells, which revealed constitutive com1 expression, was inhibited by 1,25(OH)2D3 (10(-7) M). This was strongly associated with cell cycle arrest in G1 phase, consistent with accumulation of the hypophosphorylated form of the retinoblastoma protein as well as the induction of the cyclin-dependent kinase inhibitor p21. These cell cycle events were preceded by a transient up-regulation (5-8-fold) of com1 mRNA. Furthermore, clonal growth of the MCF7/LCC2 cells was also inhibited by 1,25(OH)2D3 (10(-7) M), and when the com1-negative MCF-7 cells were stably transfected with com1, the resulting MCF7/com1 cells showed a significant decrease in colony formation. These results seem to indicate that rather than promoting growth, com1 may participate in the regulatory pathway involved in cellular growth inhibition when recruited by inhibitory signals.     

17beta-Estradiol differentially regulates androgen-responsive genes through estrogen receptor-beta- and extracellular-signal regulated kinase-dependent pathways in LNCaP human prostate cancer cells

The molecular mechanism underlying the actions of estrogens in normal prostate physiology and prostate cancer development remains unclear. In the present study we tested the hypothesis that estrogens modulate androgen-dependent events in prostate cells by examining the effects of 17beta-estradiol (E2) on androgen-responsive genes (ARGs) in the androgenresponsive LNCaP cells. We found that LNCaP cells express estrogen receptor-beta (ER-beta) as the major form of ER and ER treatment with E2 led to an increase in cell growth. The proliferative effect of E2 correlated with induction of several ARGs by E2. Interestingly, some other ARGs did not respond to E2. Consistent with involvement of ER-beta, the induction of both cell growth and ARG mRNA levels by E2 was attenuated by the pure antiestrogen ICI 182,780. Moreover, we found ER-beta small interfering RNA attenuated induction of ARG mRNAs by E2. However, the effect of E2 on ARG mRNA appeared also to require the androgen receptor and to be mediated through activation of the extracellular-signal regulated kinase (ERK) pathway. These results provide mechanistic evidence supporting a direct effect of estrogen, mediated through ER-beta- and ERK-dependent pathways, on specific molecular targets in human prostate cancer cells.     

Presence of 1,25-dihydroxyvitamin D3 receptors in established human cancer cell lines in culture

Receptors for 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] have been described in several human breast cancer cell lines and more recently in human melanoma. The presence of 1,25-(OH)2D3 receptor (1,25-DR) in two cultured breast cancer cell lines was associated with receptors for calcitonin, another hormone thought to have effects on calcium handling. Therefore, it seemed important to examine a range of established human cancer cell lines for the presence of receptors for 1,25-(OH)2D3 and calcitonin. Thirty-three cancer cell lines were examined. 1,25-DR was found to be present in 23 lines, while calcitonin receptors were not detected in any of them. The 1,25-DR from several cell lines sedimented at about 3.5S in sucrose density gradients, had the appropriate specificity for vitamin D metabolites, had Kds of 0.8 to 2.2 x 10(-11) M, and had receptor concentrations of 12 to 99 fmol/mg protein. Ten malignant melanoma and nine colonic carcinoma lines constituted the largest groups of carcinoma cell lines, and seven and eight, respectively, of these were 1,25-DR positive. The high frequency of 1,25-DR positivity in the cultured colonic carcinoma cells is quite different from the low frequency of 1,25-DR in primary colonic carcinomas. It was also interesting that both of two cell lines derived from patients who had had both bone metastases and malignant hypercalcemia were 1,25-DR positive. These various cell lines may provide useful models for the examination of 1,25-(OH)2D3 action in vitro.     

蛇床子素对人前列腺癌LNCaP细胞衰老的影响及其机制研究

目的:探讨天然化合物蛇床子素对人前列腺癌LNCaP细胞衰老的影响及分子机制。方法:采用CCK8法检测蛇床子素对LNCaP细胞增殖的影响；用EdU细胞增殖检测试剂盒检测细胞增殖情况；流式细胞仪检测蛇床子素对其周期阻滞情况；β-半乳糖苷酶染色法检测蛇床子素对LNCaP细胞衰老的影响；Western blot检测衰老相关蛋白SKP2、p27的表达情况。结果:CCK8结果显示蛇床子素对LNCaP细胞的增殖有明显的抑制作用，且呈现一定剂量依赖性（P＜0.05）；EdU结果发现药物处理组细胞在荧光电镜下观察增殖细胞数较空白对照组逐渐减少，当蛇床子素浓度为150 μmol/L时，增殖细胞数较空白对照组下降30%（P＜0.01）；流式细胞仪检测结果显示当蛇床子素浓度为100、150 μmol/L时，阻滞于G2/M期的细胞数明显增多，并且呈现一定的浓度依赖（P＜0.05）；药物处理组细胞于倒置显微镜观察可见，蛇床子素浓度为150 μmol/L时，β-半乳糖苷酶阳性染色细胞数较对照组明显增加（P＜0.01）；免疫印迹法结果显示随着蛇床子素浓度的增加，衰老相关蛋白SKP2的表达减少、p27的表达增加（P＜0.05）。结论:蛇床子素可以抑制前列腺癌LNCaP细胞增殖并进一步诱导其衰老。     

Significance of 1,25-dihydroxyvitamin D3 receptor in primary breast cancers

Specific high affinity receptors for 1,25-dihydroxyvitamin D3 are present in several human breast cancer cell lines, and this hormone can regulate the replication of these cells. These receptors are also present in primary breast carcinomas. The present study has resulted from the follow-up for up to 68 mo of 263 women, who had had 1,25-dihydroxyvitamin D receptor (1,25-DR) levels measured in their primary tumors. Survival data on 191 women were correlated with the levels of 1,25-DR and other steroid hormone receptors, menopausal status, and age by life table analysis. Survival was not affected by 1,25-DR level in either absolute terms or relative levels. However, the late development of lymph node metastases in eight of 47 individuals was correlated with the 1,25-DR level (P = 0.05). There was no correlation between 1,25-DR or other hormone receptor levels and the development of hypercalcemia or bone metastases in the small number of individuals so affected. As we had observed previously, there was no correlation between the level of 1,25-DR and that of the other steroid hormones. These data show that the presence of 1,25-DR in primary breast cancers is independent of other prognostic indicators and, inasmuch as it correlated with late lymph node metastasis, may be an adverse prognostic indicator.     

Suppression of in vivo growth of human cancer solid tumor xenografts by 1,25-dihydroxyvitamin D3

It has been demonstrated previously that several human cancer cell lines possess specific, high affinity receptors for 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3, calcitriol] and that 1,25-(OH)2D3 and certain of its metabolites inhibit the growth in vitro of several human breast cancer and malignant melanoma cell lines, i.e., analogous to the effect of estrogens on breast cancer. Furthermore, it has been shown that 1,25-(OH)2D3 and one of its synthetic analogues prolonged the survival in mouse leukemia, induced by inoculation of leukemic cells into syngeneic mice. However, until now no growth-inhibitory effect of 1,25-(OH)2D3 has been demonstrated in vivo for human cancer cells or for solid cancers. This paper describes the suppression by 1,25-(OH)2D3 of the growth of human cancer cell-derived xenografts in immune-suppressed mice. However, the 24-hydroxylated metabolite and the 24-difluorinated analogue of 1,25-(OH)2D3, both of which are active in vitro, were ineffective in this xenograft model system. The suppression by 1,25-(OH)2D3, which was achieved without significant toxicity, was observed with xenografts derived from two 1,25-(OH)2D3 receptor-positive cell lines (COLO 206F, derived from a colonic cancer, and COLO 239F from a malignant melanoma) but not in those from a receptor-negative line (RPMI 7932, also derived from a malignant melanoma). These studies demonstrate that pharmacological doses of 1,25-(OH)2D3 can be tolerated in the presence of a low calcium diet and that these doses can suppress the growth of human solid xenograft tumors in vivo. This is the first report of 1,25-(OH)2D3 growth suppression of solid tumors derived from human cancer cells in an in vivo model system, and it supports the hypothesized potential of the hormone in the treatment of 1,25-(OH)2D3 receptor-positive human cancers.     

TRPM8 channel as a novel molecular target in androgen-regulated prostate cancer cells

The cold and menthol receptor TRPM8 is highly expressed in prostate and prostate cancer (PC). Recently, we identified that TRPM8 is as an ionotropic testosterone receptor. The TRPM8 mRNA is expressed in early prostate tumors with high androgen levels, while anti-androgen therapy greatly reduces its expression. Here, from the chromatin-immunoprecipitation (ChIP) analysis, we found that an androgen response element (ARE) mediates androgen regulation of trpm8. Furthermore, using immunofluorescence, calcium-imaging and planar lipid bilayers, we identified that TRPM8 channel is functionally regulated by androgens in the prostate. Although TRPM8 mRNA is expressed at high levels, we found that the TRPM8 protein undergoes ubiquitination and degradation in PC cells. The mass-spectrometry analysis of TRPM8, immunoprecipitated from LNCaP cells identified ubiquitin-like modifier-activating enzyme 1 (UBA1). PYR-41, a potent inhibitor of initial enzyme in the ubiquitination cascade, UBA1, increased TRPM8 activity on the plasma membrane (PM) of LNCaP cells. Furthermore, PYR-41-mediated _PMTRPM8 activity was accompanied by enhanced activation of p53 and Caspase-9. Interestingly, we found that the trpm8 promoter possesses putative binding sites for p53 and that the overexpression of p53 increased the TRPM8 mRNA levels. In addition to the genomic regulation of TRPM8 by AR and p53, our findings indicate that the testosterone-induced _PMTRPM8 activity elicits Ca²⁺ uptake, subsequently causing apoptotic cell death. These findings support the strategy of rescuing _PMTRPM8 expression as a new therapeutic application through the regulation of PC cell growth and proliferation.