Influence of hypoxia on TRAIL-induced apoptosis in tumor cells

PURPOSE: Tumor hypoxia reduces the efficacy of radiotherapy, many types of chemotherapy, and tumor necrosis factor-alpha (TNF-alpha). TRAIL (TNF-alpha-related apoptosis-inducing ligand) is a ligand for death receptors of the TNF superfamily shown to be selectively toxic for tumor cells and thereby a promising antineoplastic tool. The impact of hypoxia on TRAIL-induced apoptosis was examined in this study. METHODS AND MATERIALS: Apoptosis induction and growth rates of various tumor cell lines under hypoxia were evaluated in vitro. Biologically effective induction of hypoxia was verified by determination of hypoxia-inducible factor-1 (HIF-1) activation. The efficacy of TRAIL- and radiation-induced apoptosis under different oxygen conditions was quantified in vitro. The impact of Bcl-2 on TRAIL-induced apoptosis under hypoxia or normoxia was evaluated by comparing cells expressing Bcl-2 with a vector control. RESULTS: Moderate hypoxia caused no growth retardation or apoptosis, but led to activation of HIF-1 as a prerequisite of hypoxic gene induction. Cellular responses to TRAIL differed considerably among the cell lines tested. Hypoxia reduced radiation-induced, but not TRAIL-induced, apoptosis in the tested cell lines. Hypoxia did not induce Bcl-2 expression. Bcl-2 had a minor impact on the efficacy of TRAIL-induced apoptosis. CONCLUSION: Taken together, the data indicate that TRAIL is clearly effective under conditions of proven hypoxia.     

一种新型增殖型腺病毒治疗肝癌的体外研究

目的 评价增殖腺病毒CNHK500对肝癌细胞的治疗效果。方法 利用病毒增殖实验、细胞活力实验(MTT)、蛋白印迹分析来检测增殖病毒CNHK500在端粒酶阳性的肝癌细胞株HepGⅡ、Hep3B、SMMC7721及正常细胞中选择性增殖和溶解细胞的特性。结果 CNHK500感染人肝癌细胞株HepGⅡ、Hep3B、SMMC7721细胞后大量增殖,在感染后96小时增殖倍数分别为52000、396984．9和632911．3倍,同野生型5型腺病毒(wtAd5)类似。然而在正常细胞中,CNHK500的增殖能力较wtAd5大大减弱,感染96小时后仅增殖3．1～100倍,而wtAd5却高达3160～17357倍。MTT实验观察到在肝癌细胞HepGⅡ和Hep3B中,感染后第7天达到半数杀伤的MOI值(IC50)分别为2和0．01,而在正常成纤维细胞BJ细胞中却高达1000。在常氧情况下,用蛋白印迹可在肿瘤细胞中检测到腺病毒ElA蛋白的表达,但在正常细胞却检测不到。EIB蛋白仅在缺氧条件下(0．1％O2)的肿瘤细胞中表达。结论 实验结果表明CNHK500能有效地选择性在肝癌细胞中增殖、复制、杀伤,而在正常细胞中增殖和溶解细胞能力却大大减弱。联合治疗基因,CNHK500可能为肝癌的治疗提供一种新的策略。     

Influence of hypoxia and an acidic environment on the metabolism and viability of cultured cells: potential implications for cell death in tumors

Hypoxia and an acidic environment are known to occur in regions of solid tumors and might be involved in the causation of necrosis. The viability and energy metabolism of cells in tissue culture were therefore investigated under hypoxic and/or acidic conditions. Acute exposure of Chinese hamster ovary (CHO) cells or human bladder cancer MGH-U1 cells to hypoxia plus low pH (6.5 to 6.0) was cytotoxic in a time- and pH-dependent manner; surviving fraction was reduced to approximately 10(-4) following a 6-h exposure to hypoxia at pH 6.0. There was no effect on viability when aerobic CHO cells were exposed for 6 h at pH 6.0, or when either cell line was rendered hypoxic for 6 h at pH 7.0; MGH-U1 cells showed slight sensitivity to acidic pH in air. Decrease in viability of CHO cells incubated under acid conditions was observed over the range of oxygen concentrations from 0.2 to 0.05%, similar to the range which causes change in cellular sensitivity to radiation. Glucose consumption and lactate production by both cell lines were inhibited at low pH under both aerobic and hypoxic conditions. Cellular adenosine triphosphate (ATP) levels and the energy charge [(ATP + 1/2 adenosine diphosphate)/(adenosine monophosphate + adenosine diphosphate + ATP)] of CHO cells were reduced by about 85 and 25%, respectively, after a 6-h exposure to hypoxia at pH 6.0 but were not influenced by hypoxia or acid pH alone. Inhibition of glycolysis by incubation of CHO cells under hypoxic conditions in the absence of glucose (at pH 7.0) led to a larger fall in cellular ATP and energy charge, but cell survival fell to only approximately 10(-2) at 6 h. These results demonstrate that hypoxia and an acid environment interact to cause marked toxicity. A decrease in energy charge of the cells may contribute to loss of viability, but additional mechanisms appear to be involved.     

Apoptosis is induced by the active metabolite of vitamin D3 and its analogue EB1089 in colorectal adenoma and carcinoma cells: possible implications for prevention and therapy

Vitamin D3 is believed to reduce the risk of colon cancer, and serum levels inversely correlate with colorectal cancer incidence. The active metabolite, 1alpha,25-dihydroxyvitamin D3, has previously been shown to inhibit growth and promote differentiation of colon cancer cells. The vitamin D analogue, EB1089, is currently under clinical trial in a variety of cancers because of its growth-inhibitory effects in vitro and reduced hypercalcemic effects in vivo. The mechanism of growth inhibition by EB1089, however, remained to be determined. In this study we examined the effects of alpha,25-dihydroxyvitamin D3 and EB1089 on five colorectal tumor cell lines (two adenoma and three carcinoma) to determine the mechanism of growth inhibition and to ascertain whether premalignant adenoma cells were responsive to these agents. 1alpha,25-Dihydroxyvitamin D3 and EB1089 induced p53-independent apoptosis in adenoma and carcinoma cell lines in a dose-dependent manner between 10(-10) and 10(-6) M. EB1089, as well as inducing apoptosis, increased the proportion of cells in the G1 phase, particularly in the adenoma cell lines. In two of the three carcinoma cell lines (SW620 and PC/JW), levels of apoptosis induced by EB1089 were similar or greater than those induced by 1alpha,25-dihydroxyvitamin D3. Although the carcinoma cell line HT29 was relatively resistant to apoptosis induced by EB1089 compared with 1alpha,25-dihydroxyvitamin D3, EB1089 markedly inhibited cell yields. These observations offer promise for the clinical use of EB1089. To determine whether the induction of apoptosis by 1alpha,25-dihydroxyvitamin D3 and EB1089 was potentially via a differentiation pathway, alkaline phosphatase activity was measured as a marker of differentiation. Induction of alkaline phosphatase was observed in the floating apoptotic cells as well as in the adherent population. A link between the induction of differentiation and apoptosis by 1alpha,25-dihydroxyvitamin D3 and EB1089 is suggested by the occurrence of apoptosis subsequent to the induction of differentiation. To investigate the molecular pathway to apoptosis induction, members of the Bcl-2 family of proteins were examined (Bcl-2, Bcl-x, Bax, and Bak). Decreased Bcl-2 was observed in some cell lines, particularly in response to EB1089, but was not essential for apoptosis. Levels of the proapoptotic protein Bak, however, were consistently increased in all of the five cell lines in association with apoptosis induced by either agent. The results implicate Bak protein in the induction of apoptosis by 1alpha,25-dihydroxyvitamin D3 or its analogue EB1089. The ability of EB1089 to induce apoptosis in colorectal carcinoma cells suggests that this or other vitamin D analogues may prove clinically effective for the treatment of colorectal cancer. Furthermore, the fact that it induces cell cycle arrest and apoptosis in the premalignant adenoma cells may suggest an application in colorectal cancer chemoprevention.     

Phosphorylation of eIF2alpha is required for mRNA translation inhibition and survival during moderate hypoxia.

BACKGROUND AND PURPOSE: Human tumors are characterized by temporal fluctuations in oxygen tension. The biological pathways that respond to the dynamic tumor microenvironment represent potential molecular targets for cancer therapy. Anoxic conditions result in eIF2alpha dependent inhibition of overall mRNA translation, differential gene expression, hypoxia tolerance and tumor growth. The signaling pathway which governs eIF2alpha phosphorylation has therefore emerged as a potential molecular target. In this study, we investigated the role of eIF2alpha in regulating mRNA translation and hypoxia tolerance during moderate hypoxia. Since other molecular pathways that regulate protein synthesis are frequently mutated in cancer, we also assessed mRNA translation in a panel of cell lines from different origins. MATERIALS AND METHODS: Immortalized human fibroblast, transformed mouse embryo fibroblasts (MEFs) and cells from six cancer cell lines were exposed to 0.2% or 0.0% oxygen. We assayed global mRNA translation efficiency by polysome analysis, as well as proliferation and clonogenic survival. The role of eIF2alpha was assessed in MEFs harboring a homozygous inactivating mutation (S51A) as well as in U373-MG cells overexpressing GADD34 (C-term) under a tetracycline-dependent promoter. The involvement of eIF4E regulation was investigated in HeLa cells stably expressing a short hairpin RNA (shRNA) targeting 4E-BP1. RESULTS: All cells investigated inhibited mRNA translation severely in response to anoxia and modestly in response to hypoxia. Two independent genetic cell models demonstrated that inhibition of mRNA translation in response to moderate hypoxia was dependent on eIF2alpha phosphorylation. Disruption of eIF2alpha phosphorylation caused sensitivity to hypoxia and anoxia. CONCLUSIONS: Disruption of eIF2alpha phosphorylation is a potential target for hypoxia-directed molecular cancer therapy.     

Fibronectin interaction with alpha4beta1 integrin prevents apoptosis in B cell chronic lymphocytic leukemia: correlation with Bcl-2 and Bax.

B cell chronic lymphocytic leukemia (B-CLL) consists of the accumulation of malignant cells that apparently escape normal apoptotic regulation. We have studied the role of alpha4beta1 integrin/fibronectin interaction in preventing apoptosis of these cells in vitro. B cells from 16 patients showed constant expression of alpha4beta1 and little or no alpha5beta1. B-CLL cells cultured on fibronectin or two previously described fibronectin recombinant fragments (H89 and H0) which contain the ligands for alpha4beta1, consistently showed higher viability than control cells cultured on poly-lysine. The H89 fragment, containing the high affinity ligand CS-1, was the most efficient substrate with mean cell viability values of 72, 60 and 35% at days 2, 5 and 8 of culture, respectively. For control cells these values were 40, 27 and 15%, respectively. Parallel cell cycle analysis confirmed these results. The anti-apoptotic effect required direct contact with immobilized substrata since it was not observed when using B-CLL conditioned media alone or when clustering alpha4beta1 with specific mAbs in suspension. Quantitation of the apoptosis regulatory proteins Bcl-2 and Bax revealed that cells cultured on the H89 fragment showed high/moderate levels of Bcl-2 (with some interpatient variation) and low levels of Bax resulting in an elevated Bcl-2/Bax ratio. These results indicate that adhesion of B-CLL cells to fibronectin upregulate the Bcl-2/Bax ratio and this may contribute to the anti-apoptotic effect induced via alpha4beta1 integrin.     

促红细胞生成素(EP0)对人肿瘤细胞株的增殖的影响

Objective:To investigated whether erythropoietin(EPO)would promote the proliferation of human caner cell line MCF-7,Panc-1 and HepG2 so as to determine whether EPO would result a worse prognosis to the patients with malignant diseases.Methods:We examined the growth inhibitory or promotional effect of EPO to MCF-7,Panc-1 and HepG2 by MTI assay.Then we examined lhe cell cycle of those cancer cell lines which was cultured with EPO and without EPO by FCM.Results:The results showed there was no significant growth inhibitory or promotional etfect of EPO to MCF-7,Panc-1 and HepG2.The cell cycle of those cancer cell lines cultured with EPO also has no significant different to that of those cancer cell lines cultured without EPO.Conclusion:It is concluded that EPO has no promotion effect to the caner cell lines'proliferation,and maybe will not result a worse prognosis to the patients with malignant diseases.     

p53-dependent radioresistance in ovarian carcinoma cell lines

In the present study, we investigated the radiosensitivity profiles of three established human ovarian carcinoma cell lines, PA-1, Caov-3, and SK-OV-3, using the adenosine triphosphate-cell viability assay (ATP-CVA). We have correlated radioresponsiveness with the p53 status and the p53 accumulation after irradiation as well as with the Bcl-2 expression and the growth rate of these cell lines. The p53 status was examined by immunocytochemistry and a functional assay (functional analysis of separated alleles in yeast, FASAY); the p53 accumulation was determined by immunocyotochemistry and flow cytometry. Futhermore, the Bcl-2 expression before and after irradiation was examined by immunocytochemistry. PA-1, expressing wild-type p53, showed an unequivocal accumulation of p53 protein following exposure to irradiation. This cell line was found to be strongly sensitive to irradiation. The two p53 mutant cell lines Caov-3 and SK-OV-3 showed radioresistance at different degrees and irradiation did not result in p53 accumulation. None of the cell lines examined expressed Bcl-2 protein and no change was seen after irradiation. Furthermore, the most sensitive cell line to irradiation, PA-1, showed the highest proliferative activity, while Caov-3 and SK-OV-3, the more resistant cell lines, exhibited lower growth rates. Our findings indicate that the presence of p53 protein is a possible determinant for the cytotoxicity induced by irradiation in the investigated ovarian carcinoma cell lines. Bcl-2 expression does not seem to determine the response to irradiation in these cell lines. Additionally, an association between radioresponsiveness and the growth rate is suggested in PA-1, Caov-3, and SK-OV-3.     

缺氧状况下Rho GTPases的表达和活性变化及其与肿瘤血管生成关系的研究

目的 探讨Rho GTPases在缺氧状态下的表达和活性变化以及与缺氧诱导的肿瘤血管生成的关系。方法 提取胃癌细胞AGS、SGC7901和肝癌细胞HepG2的总RNA,采用半定量RT-PCR检测缺氧状况下Rho GTPases家族分子的mRNA表达水平;应用Rho蛋白活性检测试验进一步检测其活性;Western blot检测肿瘤血管生成相关分子HIF-α、血管内皮细胞生长因子(VEGF)、P63和PIEN的表达水平。结果 缺氧状况下,多种肿瘤细胞系中Racl的mRNA表达水平均明显增高;Racl活性迅速升高,约3h达到高峰,且其活性与HIF-1α、VEGF呈正相关;而与P63、PFEN呈负相关。结论 Rho家族蛋白分子Rac1在缺氧诱导下被激活,且Rac1可能与缺氧诱导的肿瘤血管生成相关。     

Down-regulation of cobalt-induced HIF-1alpha expression correlates with cell proliferation and apoptosis in human gastric carcinoma cells

Previously we reported that the hypoxia-inducible factor-1alpha (HIF-1alpha) expression correlated with cell proliferation and apoptosis under 500 mM of CoCl2 treatment in a human gastric carcinoma cell line, MKN-1. Herein we report a similar correlation in other cell lines, MKN-45 and TMK-1. The dual-phase expression of HIF-1alpha was highest at 6 and 8 h of treatment in MKN-45 and TMK-1, respectively, while the peak in MKN-1 occurred at 4 h. The cell viability indices showed a similar dual phase to the HIF-1alpha expression, while the apoptotic indices started to increase as the level of the HIF-1alpha expression decreased. In our previous study, the FACS analysis showed a marked G2/M arrest and an increase of the pre-G1 area in MKN-1 after 36 h of treatment, whereas the G2/M arrest was not observed in MKN-45 and TMK-1. The expression of cell cycle and apoptosis-related proteins showed a correlation with the HIF-1alpha expression and the FACS results, which suggested that the level of HIF-1alpha correlated with proliferation and apoptosis in human gastric carcinoma cell lines with a possible cell-type specific pattern.     

Down-regulation of mitochondrial F1F0-ATP synthase in human colon cancer cells with induced 5-fluorouracil resistance

5-Fluorouracil (5-FU) is widely used for treatment of advanced colorectal cancer. However, it is common for such patients to develop resistance to 5-FU, and this drug resistance becomes a critical problem for chemotherapy. The mechanisms underlying this resistance are largely unknown. To screen for proteins possibly responsible for 5-FU resistance, cells resistant to 5-FU were derived from human colon cancer cell lines and two-dimensional gel electrophoresis-based comparative proteomics was done. Two-dimensional gel electrophoresis data showed there was lower expression of the alpha subunit of mitochondrial F(1)F(0)-ATP synthase (ATP synthase) in 5-FU-resistant cells compared with parent cells. Western blotting showed that expression of other ATP synthase complex subunits was also lower in 5-FU-resistant cell lines and that these resistant cells also showed decreased ATP synthase activity and reduced intracellular ATP content. The ATP synthase inhibitor, oligomycin A, strongly antagonized 5-FU-induced suppression of cell proliferation. When 5-FU sensitivity was compared with ATP synthase activity in six different human colon cancer cell lines, a positive correlation has been found. Furthermore, suppressed ATP synthase d-subunit expression by siRNA transfection increased cell viability in the presence of 5-FU. Bioenergetic dysfunction of mitochondria has been reported as a hallmark of many types of cancers (i.e., down-regulation of ATP synthase beta-subunit expression in liver, kidney, colon, squamous oesophageal, and lung carcinomas, as well as in breast and gastric adenocarcinomas). Our findings show that ATP synthase down-regulation may not only be a bioenergetic signature of colorectal carcinomas but may also lead to cellular events responsible for 5-FU resistance.     

选择性增殖腺病毒CNHK500治疗乳腺癌的实验研究

目的: 观察选择性增殖腺病毒CNHK500对乳腺癌的特异性杀伤作用.方法: 行病毒增殖实验和细胞生长抑制实验,验证CNHK500选择性复制和杀伤能力; Western blot检测腺病毒E1A和E1B在细胞中的表达.结果: CNHK500在乳腺癌细胞中复制能力与野生型腺病毒wtAd5相似,较ONYX-015增殖能力强.在正常成纤维细胞中CNHK500病毒增殖能力明显减弱, 较wtAd5增殖能力弱1 000倍左右.CNHK500可有效杀伤乳腺癌细胞株;而CNHK500对正常成纤维细胞的杀伤力较wtAd5减弱约100倍.CNHK500病毒的E1A可以选择性在端粒酶阳性的乳腺癌细胞株中表达,在端粒酶阴性的正常成纤维细胞株BJ中不表达, CNHK500可以选择性地在缺氧条件下表达E1B.动物实验结果显示,静脉注射CNHK500可以显著抑制MCF-7乳腺癌细胞裸鼠移植瘤的生长,治疗效果与给药剂量相关.结论: 肿瘤选择性增殖腺病毒CNHK500可选择性在端粒酶阳性的乳腺癌细胞中复制,并产生体内外杀伤作用.     

Predominant Bcl-XL knockdown disables antiapoptotic mechanisms: tumor necrosis factor-related apoptosis-inducing ligand-based triple chemotherapy overcomes chemoresistance in pancreatic cancer cells in vitro

Pancreatic cancer is lethal because of its invasiveness, rapid progression, and profound resistance to chemotherapy and radiation therapy. To identify the molecular mechanisms underlying this, we have examined the expression and potency of three major death receptors: tumor necrosis factor receptor (TNF-R), TNF-related apoptosis-inducing ligand receptor (TRAIL-R), and Fas in mediating cytotoxicity in four invasive pancreatic cancer cell lines. We have analyzed the expression of major antiapoptotic factors, cell cycle regulators and death receptor decoys (DcR) in comparison with normal pancreas tissues and five other human malignant tumor cell lines. We have found that different pancreatic cancer cell lines coexpress high-level TRAIL-R, Fas, and TNF-R1 but are strongly resistant to apoptosis triggered by the death receptors. DcR2 and DcR3 overexpression may partly contribute to the resistance of pancreatic cancer cells to TRAIL-R- and Fas-mediated cytotoxicity. Bcl-XL and Bcl-2 are predominantly overexpressed in pancreatic cancer cell lines, respectively. Bcl-XL is also predominantly overexpressed in prostate, colorectal, and intestinal cancer cells. The knockdown of the predominant Bcl-XL overexpression significantly reduces the viability of pancreatic cancer cells to TNFalpha- and TRAIL-mediated apoptosis by sublethal-dose single and combined antitumor drugs, including geldanamycin, PS-341, Trichostatin A, and doxorubicine. Geldanamyin and PS-341 synergistically block NFkappaB activation, suppress Akt/PKB pathway, and down-regulate Bcl-XL, Bcl-2, cIAP-1, and cyclin D1 expression. This combined regimen dramatically enhances TRAIL cytotoxic effects and breaks through chemoresistance. Bcl-XL plays a vital role in pancreatic cancer chemoresistance. Geldanamycin, PS-341, and TRAIL triple combination may be a novel therapeutic strategy for pancreatic cancer.     

XBP1 对低氧环境下胶质瘤细胞活力及糖酵解的影响*

目的:明确低氧应激对胶质瘤细胞X-盒结合蛋白1（X-box binding protein1,XBP 1）的作用;明确胶质瘤细胞XBP 1 表达与糖代谢之间的关系;抑制XBP 1 表达对胶质瘤细胞在常氧和低氧环境下细胞活力的影响;明确低氧环境中XBP 1 对胶质瘤细胞糖酵解的影响。方法:分别在常氧和低氧条件下培养人脑胶质瘤细胞系,检测XBP 1 激活情况;使用siRNA 技术抑制XBP 1 表达,使用氧化磷酸化抑制剂处理细胞,检测细胞活力及糖代谢方式的改变,在常氧和低氧条件下检测细胞存活及糖酵解产物。结果:低氧环境下XBP 1 活化增加。低氧环境下XBP 1 沉默降低胶质瘤细胞活力、ATP 和乳酸生成,葡萄糖消耗量减少。细胞氧化磷酸化受到抑制后,XBP 1 沉默降低胶质瘤细胞存活率。结论:低氧环境可诱导胶质瘤细胞XBP 1 的活化。在低氧环境下XBP 1 沉默降低胶质瘤细胞活力和糖酵解,胶质瘤细胞的糖酵解依赖于XBP 1 活化。      

Tumour Suppressive Effects of WEE1 Gene Silencing in Breast Cancer Cells

Background: WEE1 is a G2/M checkpoint regulator protein. Various studies have indicated that WEE1could be a good target for cancer therapy. The main aim of this study was to asssess the tumor suppressivepotential of WEE1 silencing in two different breast cancer cell lines, MCF7 which carries the wild-type p53 andMDA-MB468 which contains a mutant type. Materials and Methods: After WEE1 knockdown with specificshRNAs downstream effects on cell viability and cell cycle progression were determined using MTT and flowcytometry analyses, respectively. Real-time PCR and Western blotting were conducted to assess the effect ofWEE1 inhibition on the expression of apoptotic (p53) and anti-apoptotic (Bcl2) factors and also a growth marker(VEGF). Results: The results showed that WEE1 inhibition could cause a significant decrease in the viability ofboth MCF7 and MDA-MB-468 breast cancer cell lines by more than 50%. Interestingly, DNA content assaysshowed a significant increase in apoptotic cells following WEE1 silencing. WEE1 inhibition also induced upregulationof the apoptotic marker, p53, in breast cancer cells. A significant decrease in the expression of VEGFand Bcl-2 was observed following WEE1 inhibition in both cell lines. Conclusions: In concordance with previousstudies, our data showed that WEE1 inhibition could induce G2 arrest abrogation and consequent cell deathin breast cancer cells. Moreover, in this study, the observed interactions between the pro- and anti-apoptoticproteins and decrease in the angiogenesis marker expression confirm the susceptibility to apoptosis and validatethe tumor suppressive effect of WEE1 inhibition in breast cancer cells. Interestingly, the levels of the sensitivityto WEE1 silencing in breast cancer cells, MCF7 and MDA-MB468, seem to be in concordance with the level ofp53 expression.     

维生素D对乳腺癌细胞及乳腺癌干细胞凋亡的影响

目的:探究维生素D对人乳腺癌细胞及乳腺癌干细胞凋亡的影响。方法:MTT法检测维生素D对乳腺癌SUM159细胞活力的影响;Hoechst33258染色检测维生素D对乳腺癌SUM159细胞凋亡的影响;实时定量PCR法检测维生素D对乳腺癌SUM159细胞凋亡相关分子Bax和Bcl-2 mRNA表达水平的影响;无血清悬浮培养法（serum-free medium,SFM）富集乳腺癌干细胞,显微镜下观察维生素D对乳腺癌干细胞球大小和数量的影响;实时定量PCR法检测维生素D对乳腺癌干细胞凋亡相关分子Bax、Bcl-2 mRNA表达水平的影响。结果:MTT法检测结果显示,维生素D可显著抑制乳腺癌细胞活力,且随着维生素D浓度升高,乳腺癌SUM159细胞活力的下降具有一定的剂量依赖效应,单因素方差分析显示,差异具有统计学意义(P＜0.01);Hoechst33258染色结果显示,维生素D可诱导乳腺癌SUM159细胞发生细胞凋亡形态改变;进一步PCR法检测结果显示,维生素D可显著上调乳腺癌SUM159细胞促凋亡蛋白Bax mRNA的表达,下调抗凋亡蛋白Bcl-2 mRNA的表达,单因素方差分析显示,差异具有统计学意义(P＜0.01)。SFM培养可有效富集乳腺癌干细胞,维生素D干预可明显抑制SFM富集的乳腺癌干细胞球的大小和数量,且与对照组相比,维生素D可显著上调乳腺癌干细胞球Bax mRNA的表达水平,下调Bcl-2 mRNA的表达水平,单因素方差分析显示,差异具有统计学意义(P＜0.01)。结论:维生素D可抑制乳腺癌细胞及乳腺癌干细胞活力,诱导乳腺癌细胞凋亡。     

Excess glucose induces hypoxia-inducible factor-1α in pancreatic cancer cells and stimulates glucose metabolism and cell migration

Pancreatic cancer patients frequently show hyperglycemia, but it is uncertain whether hyperglycemia stimulates pancreatic cancer cells. We have investigated whether excess glucose induces hypoxia-inducible factor-1α (HIF-1α) and stimulates glucose metabolism and cell migration in pancreatic cancer cells. We studied wild-type (wt) MiaPaCa2 pancreatic cancer cells and a MiaPaCa2 subline (namely si-MiaPaCa2) that had HIF-1α-specific small interfering RNA. Wt-MiaPaCa2 cells are known to be HIF-1α-positive in hypoxia and HIF-1α-negative in normoxia, whereas si-MiaPaCa2 cells are devoid of HIF-1α in both normoxia and hypoxia. We incubated these cells with different amounts of glucose and determined HIF-1α mRNA and protein by real-time polymerase chain reaction and western blotting. We determined glucose consumption, lactate production and intracellular hexokinase-II and ATP to assess glucose metabolisms and determined pyruvate dehydrogenase kinase-1, reactive oxygen species and fumarate to assess mitochondrial activities. Further, we studied cell migration using a Boyden chamber. Excess glucose (16.7−22.2mM) increased HIF-1α in hypoxic wt-MiaPaCa2 cells. HIF-1α expression increased ATP contents and inhibited mitochondrial activities. Extracellular glucose and hypoxia stimulated glucose metabolisms independent of HIF-1α. Excess glucose stimulated the migration of wt- and si-MiaPaCa2 cells in both normoxia and hypoxia. Thus, glucose stimulated cell migration independent of HIF-1α. Nevertheless, hypoxic wt-MiaPaCa2 cells showed greater migrating ability than their si-MiaPaCa2 counterparts. We conclude that (1) excess glucose increases HIF-1α and ATP in hypoxic wt-MiaPaCa2 cells, (2) extracellular glucose and hypoxia regulate glucose metabolisms independent of HIF-1α and (3) glucose stimulates cell migration by mechanisms that are both dependent on HIF-1α and independent of it.