Coleusin factor exerts cytotoxic activity by inducing G0/G1 cell cycle arrest and apoptosis in human gastric cancer BGC-823 cells

Coleusin factor (CF), a kind of diterpenoids, is isolated and purified from the root of a Chinese tropical plant Coleus forskohlii by our laboratory. Our previous studies have demonstrated that CF significantly inhibits growth in some kinds of cancer cell lines. Here, we found that CF remarkably inhibited growth in human gastric cancer BGC-823 cells by decreasing cell proliferation, inducing G(0)/G(1) cell cycle arrest and apoptosis. CF also decreased the mitochondrial membrane potential in BGC-823 cells. Immunoblotting analysis revealed that CF significantly decreased the expressions of cyclinD1, Bcl-2, and Bcl-x(L), increased the expressions of cytosol cytochrome c, p53, p21, and Rb. In addition, CF significantly increased the expressions and activities of caspase-3 and -9. More importantly, CF potently inhibited the growth of BGC-823 cells xenografted in athymic nude mice with negligible body weight loss and damage towards the spleen. These results indicate that CF exerts a cytotoxic effect on BGC-823 cells by inducing cell cycle arrest and apoptosis.     

Bee venom protects against pancreatic cancer via inducing cell cycle arrest and apoptosis with suppression of cell migration

BackgroundPancreatic cancer seriously threatens human health. Bee venom is a mixture of enzymes, peptides, and amines. Due to its biological activity, bee venom is widely used as an anti-inflammatory agent and pain reliever. However, little is known about the effect of bee venom on pancreatic cancer.MethodsFirstly, the Cell Counting Kit-8 (CCK-8) assay was conducted to analyze the cytotoxicity of bee venom on PANC-1 and AsPC-1 cells. Then, we evaluated the cell cycle and apoptosis by flow cytometry and the terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) assay. In addition, cell migration was analyzed by the cell scratch test and Transwell assay. Western blot was performed to assess the expression of proteins involved in the regulation of cell cycle arrest and apoptosis.ResultsResults demonstrated that bee venom significantly suppressed cell proliferation via inducing cell cycle arrest and apoptosis with suppression of cell migration. Bee venom induced S phase arrest and ameliorated the protein expression of cyclins and cyclin-dependent kinases (CDKs). At the same time, bee venom can activate the p53–p21 pathway. Experimental data also showed that bee venom induced cell apoptosis and impeded cell migration.ConclusionsThe present study revealed that bee venom could effectively inhibit tumor progression in pancreatic cancer cells, indicating the possibility of bee venom as an anti-tumor drug in pancreatic cancer.     

Anti-hepatoma cells function of luteolin through inducing apoptosis and cell cycle arrest

The aim of this study is to explore the apoptotic induction and cell cycle arrest function of luteolin on the liver cancer cells and the related mechanism. The liver cancer cell line SMMC-7721, BEL-7402, and normal liver cells HL-7702 were treated with different concentrations of luteolin. Cell proliferation ability was tested. Morphological changes of the apoptotic cells were observed under inverted fluorescence microscope after Hoechst33342 staining. We investigated the effect of luteolin on cell cycling and apoptosis with flow cytometry. The mitochondrial membrane potential changes were analyzed after JC-1 staining. Caspases-3 and Bcl-2 family proteins expression were analyzed by real-time PCR. Cell proliferation of SMMC-7721 and BEL-7402 were inhibited by luteolin, and the inhibition was dose–time-dependent. Luteolin could arrest the cells at G1/S stage, reduce mitochondrial membrane potential, and induce higher apoptosis rate and the typical apoptotic morphological changes of the liver carcinoma cells. Q-RT-PCR results also showed that luteolin increased Bax and caspase-3 expression significantly and upregulated Bcl-2 expression in a dose-dependent manner in liver carcinoma cells. However, the normal liver cells HL-7702 was almost not affected by luteolin treatment. Luteolin can inhibit SMMC-7721 and BEL-7402 cell proliferation in a time- and dose-dependent manner. And the mechanism maybe through arresting cell cycle at phase G1/S, enhancing Bax level, reducing anti-apoptotic protein Bcl-2 level, resulting in activating caspase-3 enzyme and decrease of mitochondrial membrane potential, and finally leading to cell apoptosis.     

Induction of apoptosis and cell cycle arrest by imexon in human pancreatic cancer cell lines

Imexon is an aziridine-containing small molecule currently in Phase I clinical trials. This agent has been shown to bind to thiols and increase intracellular oxidants, inducing apoptosis in hematologic cancer cells. Pancreatic cancers are known to be sensitive to oxidation, suggesting this disease may be an appropriate target for this agent. The current report examines the activity of imexon in pancreatic cells. Imexon induced concentration-dependent and time-dependent apoptosis in a panel of six human pancreatic carcinoma cell (PCC) lines. The mean IC₅₀ (SD) for growth inhibition by the SRB assay was 200 (101) µM for a 48 h exposure with a range of 64–358 µM. Cell killing was schedule-dependent, favoring exposure times ≥48 h. Imexon-treated MiaPaCa-2 cells underwent non-lethal growth arrest following exposure to concentrations ≤200 µM for 48 h. When concentrations were increased to 300 µM for ≥48 h, the MiaPaCa-2 cells arrested in G₂ phase and activated caspases 3, 8, and 9 were detected. After a 72 h exposure to the IC₈₀ concentration of imexon, cells exhibited a loss of mitochondrial membrane potential detected by CMXRos staining. However, there was no loss of reduced cellular thiols unless very high concentrations of ≥400 µM were used. In contrast, reactive oxygen species (ROS) were elevated in a dose-dependent fashion, starting at very low imexon concentrations. Imexon also significantly inhibited MiaPaCa-2 tumor growth in SCID mice at 100 mg/kg/d for 9 d. The tumor growth inhibition (% T/C) was 27% of control, and the tumor growth delay was 21 d, indicating an active agent by NCI standards. The levels of imexon that are cytotoxic in human PCC’s are achievable based on the preliminary results of the ongoing Phase I trial. Imexon appears to be active against PCCs in vitro and has an entirely novel mechanism of action involving G₂ arrest, accumulation of ROS, and the induction of apoptosis.     

TSA诱导胰腺癌BxPC-3细胞周期阻滞与凋亡的研究

目的观察曲古抑菌素A(tricho-statin A,TSA)对胰腺癌BxPC-3细胞增殖及凋亡的诱导作用,探讨TSA抗胰腺癌的作用机制。方法BxPC-3细胞应用TSA处理后采用流式细胞技术分析其细胞周期分布和细胞凋亡率,免疫组化方法检测细胞乙酰化组蛋白H4表达,Western blot分析p21 WAF1/CIP1蛋白表达。结果TSA对胰腺癌BxPC-3细胞具有生长抑制作用,且呈时间和剂量依赖性。TSA可将BxPC-3细胞阻滞于G0/G1期,TSA组G0/G1期细胞达(61.8±2.5)%,较空白对照组(42.5±2.2)%和乙醇对照组(47.3±3.4)%明显增多(P=0.004);三组细胞凋亡率分别为25.5%、5.5%和5.1%(P=0.000)。TSA组细胞p21 WAF1/CIP1蛋白表达及其相关染色质乙酰化组蛋白H4表达上调。结论TSA对胰腺癌BxPC-3细胞增殖和细胞周期具有影响作用并可诱导细胞凋亡,p21 WAF1/CIP1蛋白及其相关染色质乙酰化组蛋白H4表达上调可能是其抗胰腺癌作用机制之一。     

Inhibition of Aurora A promotes chemosensitivity via inducing cell cycle arrest and apoptosis in cervical cancer cells

Aurora kinase A (AurA) regulates genomic instability and tumorigenesis in multiple cancer types. Although some studies have reported that Aur A may predict cervical cancer outcomes, its precise function and molecular mechanism in cervical cancer pathogenesis remain unclear. In this study, by overexpression or silencing of Aur A in cervical cancer cell lines, we found that overexpression of Aur A promoted cell proliferation through G1/S cell cycle transition and anti-apoptosis, xenograft tumor growth and chemoresistance to Taxol. We further found that inhibition of Aur A with its specific inhibitor VX-680 enhanced the antitumor effect of Taxol via inducing apoptosis. Moreover, the clinical analysis from tissue samples demonstrated that Aur A was overexpressed, and the expression of Aur A and pERK1/2 was negatively correlated in cervical cancer tissues. The above results may provide some potential insights in treatment of cervical cancer in clinic.     

Gambogic acid inhibits the growth of osteosarcoma cells in vitro by inducing apoptosis and cell cycle arrest

The natural product gambogic acid (GA) has been demonstrated to be a promising chemotherapeutic drug for some cancers because of its ability to induce apoptosis and cell cycle arrest. Until now, no studies have looked at the role of GA in osteosarcoma. In this study, we observed the effects of GA on the growth and apoptosis of osteosarcoma cells in?vitro. We found that GA treatment inhibits the proliferation of osteosarcoma cells by inducing cell cycle arrest. Moreover, we found that GA induces apoptosis in MG63, HOS and U2OS cells. Furthermore, we showed that GA treatment elevates the Bax/Bcl-2 ratio. GA mediated the G0/G1 phase arrest in U2OS cells; this arrest was associated with a decrease in phospho-GSK3-β (Ser9) and the expression of cyclin D1. Similarly, in MG63 cells, GA mediated G2/M cell cycle arrest, which was associated with a decrease in phospho-cdc2 (Thr 161) and cdc25B. Overall, our findings suggest that GA may be an effective anti-osteosarcoma drug because of its capability to inhibit proliferation and induce apoptosis of osteosarcoma cells.     

Activation of ATM/Chk1 by curcumin causes cell cycle arrest and apoptosis in human pancreatic cancer cells

Curcumin has been shown to inhibit the growth of various types of cancer cells; however, at concentrations much above the clinically achievable levels in humans. The concentration of curcumin achieved in the plasma after oral administration in humans was estimated to be around 1.8 μM. Here, we report that treatment of BxPC-3 human pancreatic cancer cells with a low and single exposure of 2.5 μM curcumin for 24 h causes significant arrest of cells in the G2/M phase and induces significant apoptosis. Immunoblot studies revealed increased phosphorylation of H2A.X at Ser-139 and Chk1 at Ser-280 and a decrease in DNA polymerase-β level in curcumin-treated cells. Phosphorylation of H2A.X and Chk1 proteins are an indicator of DNA damage whereas DNA polymerase-β plays a role in the repair of DNA strand breaks. Normal immortalised human pancreatic ductal epithelial (HPDE-6) cells remained unaffected by curcumin treatment. In addition, we also observed a significant increase in the phosphorylation of Chk1 at Ser-345, Cdc25C at Ser-216 and a subtle increase in ATM phosphorylation at Ser-1981. Concomitant decrease in the expressions of cyclin B1 and Cdk1 were seen in curcumin-treated cells. Further, curcumin treatment caused significant cleavage of caspase-3 and PARP in BxPC-3 but not in HPDE-6 cells. Silencing ATM/Chk1 expression by transfecting BxPC-3 cells with ATM or Chk1-specific SiRNA blocked the phosphorylation of ATM, Chk1 and Cdc25C and protected the cells from curcumin-mediated G2/M arrest and apoptosis. This study reflects the critical role of ATM/Chk1 in curcumin-mediated G2/M cell cycle arrest and apoptosis in pancreatic cancer cells.     

Luteolin potentiates low-dose oxaliplatin-induced inhibitory effects on cell proliferation in gastric cancer by inducing G2/M cell cycle arrest and apoptosis

Although the reduction of oxaliplatin doses may alleviate deleterious side effects of gastrointestinal and gynecological cancer treatment, it also limits the anticancer therapeutic effects. As a high-efficient and low-priced herbal medicine ingredient, luteolin is an agent with a broad spectrum of anticancer activities and acts as a potential enhancer of therapeutic effects of chemotherapy agents in cancer treatment. This study focused on the antitumor effects and mechanism of combined treatment with luteolin and oxaliplatin on a mouse forestomach carcinoma (MFC) cell line. The study used CCK-8 assay, flow cytometry, Annexin V-FITC/PI double staining assay, reactive oxygen species testing assay, mitochondrial membrane potential testing assay, and western blot assay. The results showed that luteolin and oxaliplatin exerted synergistic effects on inhibiting MFC cell proliferation by inducing G₂/M cell cycle arrest and apoptosis. Inhibiting the tumor necrosis factor receptor-associated protein 1/phosphorylated-extracellular-regulated protein kinases1/2/cell division cycle 25 homolog C/cyclin-dependent kinase-1/cyclin B1 pathway was indispensable to the combined treatment with luteolin and oxaliplatin to induce G₂/M cell cycle arrest. In addition, luteolin increased oxidative stress in MFC cells treated with a low dose of oxaliplatin. The combined therapy damaged mitochondrial membrane potential and regulated BCL-2-associated X protein and B-cell lymphoma 2 protein expression, leading to apoptosis. Findings of the present study suggest that luteolin may be a qualified chemotherapy enhancer to potentiate the anticancer effects of low-dose oxaliplatin in MFC cells. This work provides a theoretical foundation for future research on applications of luteolin in clinical chemotherapy.     

Induction of cell cycle arrest and apoptosis in human breast cancer cells by quercetin

Quercetin, a widely distributed bioflavonoid, has been shown to induce growth inhibition in certain cancer cell types. In the present study we have pursued the mechanism of growth inhibition in MCF-7 human breast cancer cells. Quercetin treatment resulted in the accumulation of cells specifically at G2/M phase of the cell cycle. Mitotic index measured by MPM2 staining clearly showed that cells were transiently accumulated in M phase, 24 h after treatment. The transient M phase accumulation was accompanied by a transient increase in the levels of cyclin B1 and Cdc2 kinase activity. However, 24 h or longer treatment caused a marked accumulation of cells in G2 instead of M phase. Levels of cyclin B1 and cyclin B1-associated Cdc2 kinase activity were also decreased. We also found that quercetin markedly increased Cdk-inhibitor p21CIP1/WAF1 protein level after treatment for 48 h or longer, and the induction of p21CIP1/WAF1 increased its association with Cdc2-cyclin B1 complex, however, up-regulation of p53 by quercetin was not observed. Quercetin also induced significant apoptosis in MCF-7 cells in addition to cell cycle arrest, and the induction of apoptosis was markedly blocked by antisense p21CIP1/WAF1 expression. The present data, therefore, demonstrate that a flavonoid quercetin induces growth inhibition in the human breast carcinoma cell line MCF-7 through at least two different mechanisms; by inhibiting cell cycle progression through transient M phase accumulation and subsequent G2 arrest, and by inducing apoptosis.     

Effects on apoptosis and cell cycle arrest contribute to the antitumor responses of interleukin-27 mediated by retrovirus in human pancreatic carcinoma cells

Interleukin (IL)-27, composed of p28 and Epstein-Barr virus-induced gene 3 (EBI3) subunits, has diverse functions in regulating immune systems. Human melanoma cells have been shown to express both IL-27 receptor subunits, and growth inhibition by IL-27 was detected. We investigated whether forced expression of the p28-linked EBI3 gene in human pancreatic carcinoma cells (AsPC1) by retroviral vector would produce IL-27-mediated antitumor effects and the related mechanisms. The data demonstrated that AsPC1 cells expressed both IL-27 receptor subunits, and tumor growth of AsPC1/IL-27 in mice was retarded compared with vector DNA-transduced tumors and survival of the mice was prolonged. Expression of cytokines such as interferon-γ, tumor necrosis factor-α and IL-1β in tumor specimens increased, while the secretion of IFN-γ and TNF-α from spleen cells of mice bearing IL-27-transfected tumors increased. Moreover, cell cycle arrest was induced in AsPC1/IL-27 inoculated mice with upregulated p21 expression and downregulated survivin expression. The appearance of apoptotic cells increased in tumor specimens of mice bearing IL-27-transfected tumors compared with the mice bearing DNA-transfected tumors by confirming the expression of apoptosis-related proteins and activated apoptotic pathways through detection of cleaved PARP. These results suggest that transfection of the IL-27 gene into human pancreatic carcinoma cells could produce antitumor effects in?vivo and induction of cell cycle arrest and apoptosis could be the mechanism of IL-27 action in tumor regression.     

Adenovirus-mediated wt-p16 reintroduction induces cell cycle arrest or apoptosis in pancreatic cancer.

Pancreatic cancer has long carried poor prognosis. The development of new therapeutic approaches is particularly urgent. Inactivation of the tumor-suppressor gene p16(INK4a/CDKN2), a specific inhibitor of the cyclin-dependent kinases CDK4 and CDK6, is the most common genetic alteration in human pancreatic cancer, making it an ideal target for gene replacement. Here we transfected tumor cells using a recombinant adenovirus containing the wt-p16 cDNA (Ad5RSV-p16). The overexpression of p16 decreased cell proliferation in all four human pancreatic tumor cell lines (NP-9, NP-18, NP-29, and NP-31). However, G1 arrest and senescence were observed in only three. In contrast, the fourth (NP-18) showed a significant increase in apoptosis. This differential behavior may be related to the differences found in the expression level of E2F-1. Experiments on subcutaneous pancreatic xenografts demonstrated the effectiveness of p16 in the inhibition of pancreatic tumor growth in vivo. Taken together, our results indicate that approaches involving p16 replacement are promising in pancreatic cancer treatment.     

HIV-1Vpr体外诱导肿瘤细胞凋亡与细胞周期阻滞的研究

目的 研究HIV-1 Vpr诱导Hela、Lovo、HepG2细胞凋亡和G2期阻滞效果.方法 构建含有HIV-1 Vpr基因的pcDNA4-Vpr重组载体,体外转染Hela、Lovo、HepG2细胞,同时设pcDNA4-EGFP质粒转染对照组、FUGENE组和空白对照组.转染后24、48、72 h,通过甲臜化合物法检测...     

Acacetin-induced cell cycle arrest and apoptosis in human non-small cell lung cancer A549 cells

In this study, we examined acacetin (5,7-dihydroxy-4'-methoxyflavone), a flavonoid compound, for its effect on proliferation in human non-small cell lung cancer A549 cells. The results first reported that acacetin not only inhibited A549 cell proliferation but also induced apoptosis and blocked cell cycle progression in the G1 phase. ELISA assay demonstrated that acacetin significantly increased the expression of p53 and p21/WAF1 protein, which caused cell cycle arrest. An enhancement in Fas and its two forms of ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), might be responsible for the apoptotic effect induced by acacetin. Taken together, p53 and Fas/FasL apoptotic system may participate in the antiproliferative activity of acacetin in A549 cells.     

PPARγ活化诱导细胞凋亡和周期阻滞来抑制结肠癌细胞生长

目的探讨过氧化物酶体增殖物激活受体γ(peroxisome proliferator activated receptorγ,PPARγ)在结肠癌细胞株HT-29中的表达及其活化后对结肠癌细胞生长的影响。方法通过RT-PCR和Western blot检测HT-29中PPARγmRNA及蛋白质的表达,四甲基偶氮唑盐(MTT)微量酶反应比色法检测PPARγ配体罗格列酮(rosiglitazone,Rosi)和15d-PGJ2对HT-29细胞生长的影响,荧光显微镜、TUNEL法观察Rosi和15d-PGJ2激活PPARγ后诱导HT-29细胞凋亡形态和生化改变,流式细胞仪(FCM)以碘化丙啶(PI)单染法检测细胞周期。结果RT-PCR及Western blot检测结果表明结肠癌细胞HT-29中存在PPARγmRNA及蛋白质的表达。MTT结果显示Rosi和15d-PGJ2可抑制HT-29细胞生长,且具有时间、剂量依赖效应。荧光显微镜、TUNEL检测显示PPARγ活化后HT-29细胞出现典型的凋亡现象,10μmol/L Rosi或15d-PGJ2作用48h后的细胞凋亡率分别为(17.3±1.9)%及(20.8±2.9)%,与对照组(3.86±0.49)%相比差异均具有统计学意义(P<0.05)。FCM结果显示Rosi和15d-PGJ2激活PPARγ后诱导细胞周期阻滞于G0/G1期,与对照组相比差异有统计学意义(P<0.05)。结论结肠癌细胞HT-29表达PPARγ,其活化可通过诱导细胞凋亡及细胞周期阻滞,抑制结肠癌细胞增长。因此,PPARγ可能为结肠癌治疗的一个新靶点。     

2-Methoxyestradiol inhibits hepatocellular carcinoma cell growth by inhibiting Cdc25 and inducing cell cycle arrest and apoptosis

PURPOSE: 2-Methoxyestradiol (2-ME) is a physiological metabolite of estrogen, which can inhibit growth of many types of tumor cells, including hepatocellular carcinoma, both in vitro and in vivo. The exact mechanisms of its action are still unclear. We have studied the mechanisms of growth inhibition of several of human and rat hepatoma and normal liver cells by 2-ME. METHODS: Human (Hep3B, HepG2, PLC/PRF5) and rat (McA-RH7777, JM-1) hepatoma and normal rat (CRL-1439) and human (CRL-11233) liver cell lines were cultured in vitro, in presence of 2-ME, and its IC50s were determined. Cell cycle arrest, Cdc25 phosphatase inhibition and apoptosis induction were studied. Finally, the effect of 2-ME on the growth of JM-1 rat hepatoma cells in rat liver was determined in vivo. RESULTS: The IC50 range for growth inhibition of hepatoma cells was found to be between 0.5 and 3 muM. In contrast, normal rat hepatocytes and liver cell lines were resistant to 2-ME up to 20 muM. JM-1 cells were arrested in the G2/M phase of the cell cycle. Cdc25A and Cdc25B, cell cycle controlling phosphatases, activities were inhibited in vitro and 2-ME was found to likely bind to their catalytic site cysteines. As a consequence, their cellular substrates Cdk1 and Cdk2 were tyrosine phosphorylated. Caspase-3 was cleaved suggesting apoptotic cell death. Moreover, growth of JM-1 tumors, which were transplanted into rat liver, was also inhibited by treatment with 2-ME in vivo. CONCLUSIONS: 2-Methoxyestradiol is a selective, potent and relatively non-toxic hepatoma growth inhibitor both in vitro and in vivo. Cell cycle arrest of hepatoma cells was likely mediated by binding and inactivation of the Cdc25 phosphatases and induction of apoptosis.     

Modulation of docetaxel-induced apoptosis and cell cycle arrest by all- trans retinoic acid in prostate cancer cells

We report that all- trans retinoic acid (ATRA) enhanced the toxicity of docetaxel against DU145 and LNCaP prostate cancer cells, and that the nature of the interaction between ATRA and docetaxel was highly synergistic. Docetaxel-induced apoptotic cell death was associated with phosphorylation and hence inactivation of Bcl-2. ATRA enhanced docetaxel-induced apoptosis and combined treatment with ATRA and docetaxel resulted in down-regulation of Bcl-2. Docetaxel caused phosphorylation and hence inactivation of cdc2 kinase result ing in G2/M arrest. ATRA inhibited docetaxel-induced phosphorylation of cdc2 resulting in activation of cdc2 kinase and partial reversal of the G2/M arrest. ATRA also inhibited docetaxel-induced activation of MAPK indicating that the effects of docetaxel and ATRA on cdc2 phosphorylation are dependent on MAPK. We conclude that ATRA synergistically enhances docetaxel toxicity by down-regulating Bcl-2 expression and partially reverses the docetaxel-induced G2/M arrest by inhibiting docetaxel-induced cdc2 phosphorylation in a pathway that is dependent on MAPK.     

Triptolide-induced cell cycle arrest and apoptosis in human renal cell carcinoma cells

Renal cell carcinoma (RCC) is the most frequent type of renal-originated malignancy. Although nephrectomy is successfully used to save the lives of patients with localized RCC, treatment of advanced and other refractory RCCs is poor and still inadequate. Here, we show that triptolide, a small molecule and a well-known anti-inflammatory and anti-immunity agent used in the clinic, is capable of inducing cell apoptosis via the mitochondrial pathway in the 786-0 RCC cell line. This induction occurred in concert with reduced expression of genes related to the stabilization of mitochondria such as Bcl-2 and Bcl-XL. Cell cycle analysis showed that exposure to triptolide decreased the proportion of cells in the G0/G1 and G2/M phases, and increased the proportion of cells in the S phase. Cell accumulation in the S phase can be attributed to reduced expression of cell cycle checkpoint regulators such as cyclin A, cyclin B, CDK1, CDK2 and retinoblastoma proteins (Rb). These results raise the possibility that triptolide-induced apoptosis is mediated by cell cycle arrest. Similarly, in another human RCC cell line, OS-RC-2, triptolide-induced apoptosis and cell accumulation in S phase were also observed. Therefore, triptolide emerges as a stimulator of apoptosis by influencing coordinate regulation of proliferation and apoptosis, and may be applicable to the treatment of human renal cell carcinoma.     

Arginine deiminase inhibits proliferation of human leukemia cells more potently than asparaginase by inducing cell cycle arrest and apoptosis.

L-Asparaginase is used for the treatment of acute leukemias, but is sometimes ineffective or associated with severe side-effects. We report here that the enzyme arginine deiminase is approximately 100-fold more potent than L-asparaginase in inhibiting the proliferation of cultured human lymphatic leukemia cell lines while it appears to be less effective in leukemia cells of myeloid origin. The inhibition of cell proliferation involves cell growth arrest in the G1- and/or S-phase and eventually apoptotic cell death. Our results suggest the possibility of a future use of arginine deiminase for the therapy of leukemia.     

Selenomethionine induces p53 mediated cell cycle arrest and apoptosis in human colon cancer cells

While there is an increasing interest in selenium chemoprevention against human colon polyp recurrence and other cancers, the mechanism(s) by which these agents inhibit carcinogenesis are uncertain. Some of the proposed mechanisms include the inhibition of cytosine methyltransferases, carcinogen bioactivation, and inhibition of cyclooxygenase (COX). More recently, it has been suggested that selenium may exert growth inhibitory effects by activating p53. However, the molecular mechanisms of action of selenomethionine, an organoselenium compound present in selenized yeast and currently being investigated in human clinical trials for colon polyp prevention, are unclear. In the present study we tested the hypothesis that selenomethionine might affect colon cancer cell growth by p53 mediated apoptosis and/or cell cycle regulation. Four human colon cancer cell lines including HCT116 and RKO (wild type p53), HCT116-p53KO (isogenic control of HCT116 cells with p53 knocked out) and Caco-2 (mutant p53) were treated with 0-100 microM of selenomethionine for 24, 48 and 72 h. Cell viability rates were determined by the MTT assay. Cell cycle analysis was performed by flow cytometry and apoptosis measured by Annexin V-Cy5 staining. Expression of p53 protein was determined by Western blotting and immunofluorescence assays. All cell lines showed concentration and time dependent growth inhibition with selenomethionine, although HCT116 and RKO cells were the most sensitive to such treatments. Interestingly, although HCT116 and HCT116-p53KO are isogenic cell lines, selenomethionine caused a G2/M cell cycle arrest in HCT116 and RKO cells, but not in HCT116-p53KO cells. Similarly, both HCT116 and RKO demonstrated a significant increase in apoptosis (100-170%; p < 0.01) with 50-100 microM selenomethionine. Cell cycle arrest and apoptosis observed in HCT116 and RKO cell lines were accompanied by a marked increase in p53 protein expression following selenium treatment. These results clearly suggest that selenomethionine exerts p53 dependent growth inhibitory effects in colon cancer cells by inducing G2/M cell cycle arrest as well as apoptosis.