Valproic acid activity in androgen-sensitive and -insensitive human prostate cancer cells

Histone deacetylase (HDAC) inhibitors are currently undergoing clinical trials in cancer patients on the basis of their effect on proliferation, differentiation and apoptosis demonstrated in vitro. The goal of this study was to assess the effects of an HDAC inhibitor, valproic acid (VA), on proliferation, androgen-sensitivity, androgen receptor levels and E-cadherin (E-cad) expression in human prostate cancer cells. The effects of VA were evaluated in androgen-sensitive, LNCaP and -insensitive PC-3 human prostate cancer cell lines. Proliferation was assayed by cell counts and protein expression by Western blot analysis. Morphological changes were analysed under an inverted phase contrast microscope. High VA concentrations (1-25 mM) induced a very strong reduction in cell numbers ( approximately 90% with respect to control) of the two cell lines due to drug cytotoxicity. A low concentration (0.45 mM VA) slightly reduced (14%) LNCaP cell proliferation and abolished the response to androgen. In the PC-3 cells, the same concentration of VA had a more pronounced (40%) inhibitory effect and induced a response to dihydrotestosterone in terms of an enhancement in cell growth. These events were associated with morphological changes, an absence of cytotoxicity, an increase in androgen receptor levels, and, in PC-3 cells, an enhancement in E-cad expression which may be ascribed to VA differentiative action. Our findings, obtained with a VA dose (0.45 mM), which is consistent with plasma concentrations reached under oral administration of therapeutical doses in patients treated for different diseases, suggest that VA might have clinical value in prostate cancer therapy in androgen-sensitive and -insensitive tumors.     

Tributyrin induces differentiation, growth arrest and apoptosis in androgen-sensitive and androgen-resistant human prostate cancer cell lines

Progression to androgen independence remains the main problem that impacts on survival and quality of life in prostate cancer patients. We have investigated the potency of tributyrin, an orally available prodrug of butyrate, to induce growth arrest, differentiation and apoptosis in LNCaP, PC-3 and TSU-PR1 human prostate cancer cell lines. Cells were treated with 0.1 to 5 mM tributyrin or sodium butyrate. Growth inhibition, cell cycle arrest and apoptosis induction was assessed using standard methods. Both agents induced a more differentiated, fibroblast-like phenotype in androgen-sensitive as well as androgen-resistant cell lines. Expression of prostate-specific antigen was increased in LNCaP cells by tributyrin as a indicator of differentiation. The IC(50) for sodium butyrate was 2.5 mM in PC-3 and TSU-PR1 cells. LNCaP cells exhibited <50% growth inhibition at 5 mM sodium butyrate. However, the IC(50) for tributyrin was 0.8 mM in PC-3 cells, 1.2 mM in TSU-PR1 cells and 3.1 mM in LNCaP cells. Flow cytometry revealed a strong G1-arrest after exposure to tributyrin or sodium butyrate. Both agents resulted in a strong increase of apoptosis rates compared with mock-treated cells. Overall, tributyrin had a 2.5- to 3-fold growth inhibitory and apoptosis-inducing potency compared with equimolar concentrations of sodium butyrate. Our results demonstrate that tributyrin is more potent than butyrate in regard to cell growth inhibition and apoptosis induction at pharmacologically relevant concentrations. Hence, tributyrin may be a promising candidate for clinical protocols in prostate cancer.     

Influences of cyclooxygenase-1 and -2 expression on the radiosensitivities of human cervical cancer cell lines

We utilized three cervical cancer cell lines (HeLa, HT-3, and C33A) and clonogenic assays to determine whether cyclooxygenase (COX) expression is related to radiosensitivity. Using COX DNA transfection and COX inhibition by siRNA, we also examined changes in radiosensitivity caused by variations in COX expression. The survival fractions of HeLa and HT-3 cell lines, which both with COX-1 and COX-2 activity, were found to be significantly higher than that of the C33A cell line which had neither COX-1 nor COX-2 activity. Moreover, the acquisition of COX-1 in C33A cell line significantly reduced its radiosensitivity, but COX-2 transfection increased radiosensitivity in this cell line. In addition, the inhibition of COX-1 activity in HT-3 cell line using siRNA resulted in an increased radiosensitivity, but this phenomenon was not observed for COX-2 inhibition. The same experiment in HeLa cells using siRNA also showed no significant change in radiosensitivity. The results obtained during this study suggest that COX expression is associated with the radiosensitivity in uterine cervical cancer cell lines and COX-1 might have more important role than COX-2.     

Differential effects of blueberry proanthocyanidins on androgen sensitive and insensitive human prostate cancer cell lines

Blueberries are rich in health-promoting polyphenolic compounds including proanthocyanidins. The purpose of this study was to determine if proanthocyanidin-rich fractions from both wild and cultivated blueberry fruit have the same inhibitory effects on the proliferation of LNCaP, an androgen-sensitive prostate cancer cell line, and DU145, a more aggressive androgen insensitive prostate cancer cell line. When 20 μg/ml of a wild blueberry proanthocyanidin fraction (fraction 5) was added to LNCaP media, growth was inhibited to 11% of control with an IC₅₀ of 13.3 μg/ml. Two similar proanthocyanidin-rich fractions from cultivated blueberries (fractions 4 and 5) at the same concentration inhibited LNCaP growth to 57 and 26% of control with an IC₅₀ of 22.7 and 5.8 μg/ml, respectively. In DU145 cells, the only fraction that significantly reduced growth compared to control was fraction 4 from cultivated blueberries with an IC₅₀ value of 74.4 μg/ml, indicating only minor inhibitory activity. Differences in cell growth inhibition of LNCaP and DU145 cell lines by blueberry fractions rich in proanthocyanidins indicate that blueberry proanthocyanidins have an effect primarily on androgen-dependant growth of prostate cancer cells. Possible molecular mechanisms for growth inhibition are reviewed.     

Aryl hydrocarbon exposure induces expression of MMP-9 in human prostate cancer cell lines

Although aromatic hydrocarbons have been extensively studied with regard to tumor formation, there has been little investigation into effects of these environmental chemicals on regulation of genes involved in tumor invasion. We investigated effects of three arylhydrocarbons on expression of MMP-9 in PC-3 and DU145 human prostate cancer cells. TCDD exposure lead to dose and time dependent increases in MMP-9 expression. Benzo(a)pyrene and a PAH-containing soot (BDS) also induced this MMP. These hydrocarbons also stimulated MMP-9 protein secretion. Our data demonstrate that aryl hydrocarbons can stimulate the production of MMP-9 in human prostate cancer cells.     

The migration and invasion of human prostate cancer cell lines involves CD151 expression

The molecular mechanisms underlying prostate cancer metastasis remain poorly understood. The tetraspanin family member CD151 has been reported as an 'adaptor' between integrins and signal pathways. The role of CD151 in prostate cancer metastasis in vitro was investigated in this study. LNCap cells were transfected with wild-type CD151 cDNA, mutated CD151 cDNA and vector cDNA. The mutant (QRD194-196 to INF) CD151 cDNA was created using QuickChange 2 site directed Mutagenesis kit (Stratagene). siRNAs were also used to knock down the CD151 expression in the prostate cancer cell line PC3. Proliferation, migration and invasion properties were measured after gene transfection and gene knock-down. There was no difference in proliferation of untransfected or control transfected LNCap cells vs. CD151 transfected LNCap cells (P>0.05). There was greater motility of CD151-transfected vs. control cells, when transferring through migration chambers with or without matrigel-coated membranes (P<0.01, P<0.01). Fewer numbers of mutant-transfected cells were found on the membranes for both migration and invasion studies (P<0.01, P<0.01). CD151 knock-down PC3 cells showed decreased motility (P<0.01), but no change in proliferation (P>0.05). Our data show that CD151 does not change the proliferative properties of prostate cancer cells, but does promote migration and invasion, and suggest that CD151 plays a specific role in promoting prostate cancer cell motility.     

Differential effects of cholesterol and phytosterols on cell proliferation, apoptosis and expression of a prostate specific gene in prostate cancer cell lines

Background: The purpose of our study was to show the apoptotic and anti-proliferative effects of phytosterols as distinct from cholesterol effects on prostate cancer cell lines, and also their differential expression of caveolin-1, and a prostate specific gene, PCGEM1. Methods: PC-3 and DU145 cells were treated with sterols (cholesterol and phytosterols) for 48 h, followed by trypan blue dye exclusion measurement of cytotoxicity and MTT cell proliferation assays, respectively. Cell cycle analysis was carried out microscopically, and by propidium iodide uptake using flow cytometry. Sterol induction of oncogenic gene expression was evaluated by RT-PCR. Apoptotic cells were identified by immunocytochemistry using DNA fragmentation method, and by annexin V adhesion using flow cytometry. Results: Physiological doses (16 μM) of these sterols were not cytotoxic in these cells. Cholesterol-enrichment promoted mitosis (54 and 61% by microscopy; 40.8 and 34.08% by FACS analysis in PC-3 and DU145, respectively) and cell growth (P < 0.05), while phytosterols suppressed mitosis (29 and 35% by microscopy; 27.71 and 17.37% by FACS analysis in PC-3 and DU145, respectively), and significantly induced tumor-suppression (P < 0.05) and apoptosis. We demonstrated for the first time that cholesterols upregulated the expression of PCGEM1 even in androgen-insensitive prostate cancer cell lines. Phytosterols reversed this effect, while upregulating the expression of caveolin-1, a known mediator of androgen-dependent proto-oncogene signals that presumably control growth and anti-apoptosis. Conclusions: Phytosterol inhibition of PCGEM1 and cell growth and the overexpression of caveolin-1, suggests that poor disease prognosis anchors on the ability of caveolin-1 to regulate downstream oncogene(s) and apoptosis genes. Sterol intake may contribute to the disparity in incidence of prostate cancer, and elucidation of the mechanism for modulation of growth and apoptosis signaling may reveal potential targets for cancer prevention and/or chemotherapeutic intervention. Sterol regulation of PCGEM1 expression suggests its potential as biomarker for prediction of neoplasms that would be responsive to chemoprevention by phytosterols.     

Gene expression of human squamous cell carcinoma antigens 1 and 2 in human cell lines

The squamous cell carcinoma antigen (SCCA) serves as a serological marker for squamous cell carcinomas. Molecular cloning of the SCCA genomic region has revealed the presence of two tandemly arrayed genes, SCCA1 and SCCA2. SCCA1 is a papain-like cysteine proteinase inhibitor, while SCCA2 is a chymotrypsin-like serine proteinase inhibitor. Little is known concerning how expression of the SCCA1 and SCCA2 genes is regulated in human cell lines. The purpose of this study was to determine whether the SCCA1 gene or SCCA2 gene is more strongly expressed in human cell lines. Squamous cell carcinoma cell lines secreted respectively 4 times and 50 times as much SCCA proteins into medium as normal human keratinocyte and non-squamous cell carcinoma cell lines, as measured by enzyme-linked immunosorbent assay. Quantitative RT-PCR ELISA digoxigenin-labeling assay demonstrated that SCCA1 mRNA expression in squamous cell carcinoma cell lines was respectively 2.8 times and 42 times that in keratinocyte and non-squamous cell carcinoma cell lines. The ratio of SCCA1 to SCCA2 mRNA expression differed distinctly among squamous cell carcinoma, keratinocyte and non-squamous cell carcinoma cell lines (2.8, squamous; 24.1, keratinocyte; 11.0, non-squamous). These findings suggest that SCCA1 is mainly expressed in squamous cell carcinoma, keratinocyte and non-squamous cell carcinoma cell lines and that the ratio of SCCA1 to SCCA2 expression might be a novel marker for the detection of squamous cell carcinoma.     

雌激素对人乳腺癌细胞系基质细胞衍化因子-1影响的观察

目的:探讨雌激素对基质细胞衍化因子-1(SDF-1)的影响.方法:选取乳腺癌细胞系MCF-7和MDA-MB-231为研究对象,分成对照组、雌激素组和雌激素+雌激素受体阻断组,分别加入不同生理浓度的17-β雌二醇作用一定时间以及同一浓度17-β雌二醇作用不同时间点,用酶联免疫吸附实验(ELISA)方法测定培养液中SDF-1的浓度,半定量逆转录聚合酶链反应(RT-PCR)法检测细胞SDF-1 mRNA的表达.结果:MDA-MB-231细胞系加与未加雌激素,均未检测到SDF-1的分泌.而MCF-7细胞基础培养液中可检测到SDF-1分泌.不同生理浓度的17-β雌二醇均可增加MCF-7细胞SDF-1的分泌水平.当加入1×10-7 mol/L的生理高浓度17-β雌二醇时,细胞分泌SDF-1水平在2 h达到高峰,是对照组的6倍[(1 823.17±325.18)ρg/mL vs (307.23±5.42)ρg/mL,F=201.02,P<0.01],该作用可被雌激素受体拮抗剂(ICI182,780)消除.此外,SDF-1mRNA的表达水平与测得的SDF-1蛋白水平相一致.结论:在某些乳腺癌细胞系,生理浓度的雌激素可促进SDF-1的分泌,而这种作用主要是通过雌激素受体来实现.雌激素可通过SDF-1来影响乳腺癌的生物学特性.     

Synergistic cytotoxic effects of zoledronic acid and radiation in human prostate cancer and myeloma cell lines

PURPOSE: The clinical use of the potent bisphosphonate zoledronic acid has increased recently, especially for the treatment of bone metastases. Synergistic effects with chemotherapeutic agents (e.g., doxorubicin, paclitaxel) have been shown. It is not known whether similar synergistic effects exist with radiation. METHODS AND MATERIALS: IM-9 myeloma cells and C4-2 prostate cancer cells were treated with up to 200 microM concentrations of zoledronic acid, irradiated with single doses of up to 1,000 cGy, or exposed to combinations of both treatments. Cell viability was then determined via yellow dye 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide assay and the affected fractions analyzed using the median effect principal, a method developed and validated by Chou and Talalay. RESULTS: A statistically significant synergistic cytotoxic effect of the combination of zoledronic acid and radiation was documented. The extent of the effect was cell type-dependent, with the C4-2 cells showing a greater synergistic effect than the IM-9 cells. CONCLUSIONS: The combined use of zoledronic acid and radiotherapy shows enhanced in vitro cytotoxicity for two human prostate and myeloma cancer cell lines over that expected for a simple additive effect from each treatment alone. A clinical trial is under way to test this combination therapy.     

Androgen receptor gene expression in human prostate carcinoma cell lines

Responses to androgen vary widely among prostate cancers and prostatic carcinoma cell lines. We have explored the basis for this heterogeneity by examining the levels of androgen receptor expression in a prostate carcinoma cell line (LNCaP) that expresses the androgen receptor and two prostate carcinoma cell lines that do not contain detectable androgen receptor. We find that while the LNCaP cell line contains high levels of both the androgen receptor protein and mRNA, the receptor-negative cell lines DU-145 and PC-3 do not express androgen receptor protein as detected by immunoblotting or mRNA as detected by Northern analysis or S1 nuclease protection. These results indicate that the absence of androgen receptor expression in the androgen receptor-negative cell lines is caused by diminished androgen receptor mRNA levels. Genomic Southern analysis indicates that the differences in androgen receptor expression in each of these cell lines is not associated with detectable alterations in the structure of the androgen receptor gene.     

Radiosensitivity of human prostate cancer and malignant melanoma cell lines

The relative radioresponsiveness of human prostate cancer compared to malignant melanoma is well known. The effects of beta-estradiol or testosterone on the X-irradiation survival of several human cell lines were studied, including: human prostate carcinoma cell lines PC3 and DU145 and human malignant melanoma cell lines A375 and A875. Lines PC3 and DU145 demonstrated 55-61 fmol per 10(6) cells of androgen receptor with no detectable estrogen or progesterone receptor. Cells were irradiated at 120 cGy/min dose rate. There was no detectable toxicity of up to 10(-4) M testosterone or beta-estradiol on PC3 or DU145 cells in the absence of X-irradiation. At plating efficiencies from 11-13%, and plating densities of 1 x 10(4) cells per 60 cm2 flask, cell lines PC3 and DU145 demonstrated a Do of 108.5 +/- 6.5, n 2.1 +/- 0.7 cGy, and Do of 143.5 +/- 1.5 cGy, n 2.4 +/- 0.5, respectively. The addition of testosterone or beta-estradiol at 10(-4) to 10(-10) M prior to or after, X-irradiation did not alter radiosensitivity. At the same dose rate of 120 cGy/min, malignant melanoma cell lines A375 and A875 had a Do of 125 +/- 2.5 cGy, n 1.56 +/- 0.8 SF2 0.65 +/- 0.03 and line A875 demonstrated a Do of 129 +/- 4.5 cGy, n 1.58 +/- 0.4 SF2 0.55 +/- 0.04, respectively. The radiosensitivity of melanoma cell lines did not decrease at low dose rate 5 cGy/min. Thus, the in vitro radiosensitivity of androgen receptor positive prostate cancer cell lines is not necessarily altered by the presence of androgen before or after irradiation. The data support the concept that all malignant melanoma cell lines do not show a broad-shouldered cell survival curve in vitro and intrinsic cellular radioresistance.     

Bile acids induce cyclooxygenase-2 expression in human pancreatic cancer cell lines

To investigate a possible link between bile acids and the pathogenesis of pancreatic cancer, we determined whether conjugated or unconjugated bile acids induced cyclooxygenase-2 (COX-2) in two human pancreatic cancer cell lines, BxPC-3 and SU 86.86. Bile acids are known promoters of gastric and colon cancer. We demonstrated previously that COX-2, an enzyme that catalyzes the synthesis of prostaglandins, is over-expressed in human pancreatic adenocarcinoma. Both human pancreatic cell lines were treated with conjugated and unconjugated bile acids. COX-2 mRNA and protein were determined. In addition, prostaglandin E2 (PGE2) synthesis was measured. Treatment with conjugated or unconjugated bile acids for 3 h up-regulated COX-2 mRNA. Chenodeoxycholate (CD) or deoxycholate at concentrations ranging from 12.5 to 100 micro M caused a dose-dependent induction of COX-2 protein with a maximal effect at 100 micro M. Induction of COX-2 protein by CD and deoxycholate was detected after treatment for 6 h with maximal induction at 12 h. Taurochenodeoxycholate, a conjugated bile acid, also caused dose-dependent induction of COX-2 but higher concentrations of bile acid (200-1200 micro M) were required. Levels of cyclooxygenase-1 were unaffected by bile acid treatment. Unconjugated and conjugated bile acids caused 7- and 4-fold increases in PGE2 production, respectively. Taken together, these findings suggest a possible role for bile acids in the pathogenesis of pancreatic cancer.     

Curcumin down-regulates AR gene expression and activation in prostate cancer cell lines

Curcumin, traditionally used as a seasoning spice in Indian cuisine, has been reported to decrease the proliferation potential of prostate cancer cells, by a mechanism that is not fully understood. In the current study, we have evaluated the effects of curcumin in cell growth, activation of signal transduction, and transforming activities of both androgen-dependent and independent cell lines. Prostate cancer cell lines, LNCaP and PC-3, were treated with curcumin and its effects were further analyzed on signal transduction and expression of androgen receptor (AR) and AR-related cofactors using transient transfection assay and Western blotting. Our results show that curcumin down-regulates transactivation and expression of AR, activator protein-1 (AP-1), nuclear factor-kappaB (NF-kappaB), and CREB (cAMP response element-binding protein)-binding protein (CBP). Curcumin also inhibited the transforming activities of both cell lines as evidenced by the reduced colony forming ability in soft agar. The results obtained here demonstrate that curcumin has a potential therapeutic effect on prostate cancer cells through down-regulation of AR and AR-related cofactors (AP-1, NF-kappaB and CBP).     

Overexpression of caveolin-1 and -2 in cell lines and in human samples of inflammatory breast cancer

SummaryPurpose Inflammatory breast cancer (IBC) is the most aggressive form of locally advanced breast cancer (LABC). The IBC phenotype is characterized by an infiltrative growth pattern, increased (lymph)angiogenesis and the propensity to invade dermal lymphatics. In pancreatic cancer, interactions between caveolin-1 and RhoC GTPase, a key molecule in causing the IBC phenotype, regulate tumour cell motility and invasion. In this study we sought to investigate the role of caveolin-1 and -2 in IBC cell lines and in human IBC samples.Experimental design Differential methylation techniques identified the methylation status of the caveolin-1 and -2 promoters in human mammary epithelial cells (HMECs) and the SUM149 cell line. In cell line experiments, caveolin-1 and -2 mRNA and protein expression were compared in HMECs, MCF10A, the SUM102 non-IBC cell lines and 2 IBC cell lines (SUM149 and SUM190). Furthermore, caveolin-1 and -2 mRNA and protein expression were compared in human IBC and non-IBC samples using cDNA microarray, real-time qRT-PCR and immunohistochemistry. Results were correlated with RhoC protein expression data.Results In the SUM149 cell line, the caveolin-1 and -2 promoter sites were hypomethylated. A significantly increased expression of caveolin-1 and -2, both at the mRNA and protein level was found in IBC cell lines and in human samples of IBC: caveolin-1 and -2 mRNA were respectively 1.7 (p = 0.02) and 2.2 (p = 0.03) fold more expressed in IBC compared to non IBC and at the protein level, 41.4% of IBC specimens expressed either caveolin-1 or -2, compared to 15.6% of non-IBC specimens (p = 0.03). Furthermore a correlation was found between RhoC protein expression and caveolin-1 (p = 0.1) or caveolin-2 (p = 0.09) or either caveolin-1 or -2 protein expression (p = 0.04).Conclusions Although considered a tumour suppressor in breast cancer, we demonstrated overexpression of caveolin-1 and -2 in IBC cell lines and in human samples of IBC, most likely due to hypomethylation of their respective promoters. These results confirm the distinct molecular signature of IBC. Our data further suggest interaction between RhoC GTPase and the caveolins in IBC.