Beta-carotene is accumulated, metabolized, and possibly converted to retinol in human breast carcinoma cells (MCF-7)

The aims of the present study were to investigate the uptake, accumulation, and metabolism of beta-carotene by the human breast carcinoma cell line MCF-7. Beta-carotene uptake was time- and dose-dependent, and independent of cell polarity. Beta-carotene accumulation in cells was linear as a function of its concentration in medium (1.3-4.1 micromol/L). It was accompanied by increasing amounts of retinol, which accumulated in cells following a sigmoid pattern, and by other four putative metabolites. Beta-apocarotenals, epoxides, endoperoxides, retinal, retinoic acid, and retinyl esters were not detected in cell extracts. Beta-carotene and its metabolites did not induce alterations in cell morphology or subcellular localization of epithelial mucins. Beta-carotene and retinol were released from cells that had previously accumulated beta-carotene, and were further incubated in beta-carotene- and retinol-free medium, but intracellular retinol content remained constant whereas beta-carotene decreased. In conclusion, beta-carotene added to culture medium in physiological concentrations (1-6 micromol/L) is taken up and metabolized in MCF-7 cells, and is possibly converted to retinol.     

A comparative study of growth-inhibitory effects of isoflavones and their metabolites on human breast and prostate cancer cell lines

The possible growth-inhibitory properties of the recently synthesized novel metabolite 1-(2,4-dihydrobenzoyl)-1-(4-hydroxyphenyl)ethylene (2-de-O-DMA) and six other metabolites of isoflavones were investigated and compared with those of the major isoflavones genistein, daidzein, and glycitein on human breast noncancer and breast and prostate cancer cell lines in vitro. The novel metabolite 2-de-O-DMA was found to be a more potent inhibitor than genistein on human breast cancer MCF-7, MDA-MB-468, and SK-BR-3 cells and breast noncancer MCF-10A cells. In prostate cancer cell lines, LNCaP and DU145, 2-de-O-DMA elicited a six- to sevenfold more potent inhibition than genistein. Flow cytometric analysis showed that 2-de-O-DMA and genistein blocked cells at the G2/M phase of the cell cycle. Genistein and 2-de-O-DMA led to apoptosis of a variety of cancer cell lines. The rapid response of growth inhibition induced by 2-de-O-DMA compared with genistein strongly suggests that the observed antiproliferation effects elicited by this novel metabolite are mediated via a biological pathway different from that induced by genistein. 2-de-O-DMA, a novel metabolite of isoflavone, could have a potential role in chemopreventive and chemotherapeutic treatment of hormonal breast and prostate cancers.     

金雀异黄素对乳腺癌细胞iNOS表达影响

目的 研究金雀异黄素(Genistein，Gen)对人乳腺癌细胞MCF-7增殖和诱导型一氧化氮合酶(iNOS)基因表达的影响以及两者之间的关系。方法 采用MTT试验和^3H-TdR掺入法观察Gen抑制乳腺癌细胞的生长，免疫组化及RT-PCR方法检测iNOS的表达。结果 Gen显著抑制MCF-7细胞的增殖，细胞上清液中NO水平有升高的趋势，并显著增加iNOS的蛋白表达，对iNOS mRNA的表达无显著影响。结论 Gen抑制乳腺癌细胞增殖的机制之一可能与其上调iNOS基因表达有关。     

Phytoestrogen concentration determines effects on DNA synthesis in human breast cancer cells

Thirteen isoflavonoids, flavonoids, and lignans, including some known phytoestrogens, were evaluated for their effects on DNA synthesis in estrogen‐dependent (MCF‐7) and ‐independent (MDA‐MB‐231) human breast cancer cells. Treatment for 24 hours with most of the compounds at 20–80 μM sharply inhibited DNA synthesis in MDA‐MB‐231 cells. In MCF‐7 cells, on the other hand, biphasic effects were seen. At 0.1–10 μM, coumestrol, genistein, biochanin A, apigenin, luteolin, kaempferol, and enterolactone induced DNA synthesis 150–235% and, at 20–90 pM, inhibited DNA synthesis by 50%. Treatment of MCF‐7 cells for 10 days with genistein or coumestrol showed continuous stimulation of DNA synthesis at low concentrations. Time‐course experiments with genistein in MCF‐7 cells showed effects to be reversed by 48‐hour withdrawal of genistein at most concentrations. Induction of DNA synthesis in MCF‐7 cells, but not in MDA‐MB‐231 cells, is consistent with an estrogenic effect of these compounds. Inhibition of estrogen‐dependent and ‐independent breast cancer cells at high concentrations suggests additional mechanisms independent of the estrogen receptor. The current focus on the role of phytoestrogens in cancer prevention must take into account the biphasic effects observed in this study, showing inhibition of DNA synthesis at high concentrations but induction at concentrations close to probable levels in humans.     

灭活细胞周期检测点激酶增强乳腺癌细胞放疗敏感性

目的:乳腺癌是严重威胁妇女健康的重要疾病,放疗常常作为乳腺癌综合治疗的重要手段。研究表明,临床上产生放疗抵抗的主要原因是由于放疗激活细胞周期检测点信号传导通路引起细胞自我修复而逃避凋亡,因而目前通过抑制细胞周期检测点信号通路增强肿瘤放、化疗敏感性,已成为国际上抗肿瘤治疗的一个重要方向和研究热点。Chk1和Chk2是细胞周期检测点中最重要的丝氨酸/苏氨酸激酶,本研究通过反义封闭Chk1和/或Chk2基因,阻断细胞周期检测点信号传导通路,研究对乳腺癌MDA-MB-231细胞放疗后细胞周期和凋亡的影响,从而评价Chk1和Chk2基因作为肿瘤治疗靶点的有效性。方法:Western-Blot法检测转染Chk1和Chk2正、反义寡核苷酸后,细胞内Chk1和Chk2蛋白表达情况;流式细胞仪AnnexinV-PI法和SubG1法检测单转染或联合转染Chk1/2反义寡核苷酸对放疗后MDA-MB-231细胞凋亡和细胞周期的影响。结果:反义封闭Chk1或Chk2基因可解除G2/M期阻滞,增强放疗后凋亡敏感性,而同时反义封闭Chk1和Chk2基因具有协同作用。结论:阻断细胞周期检测点信号通路的关键激酶Chk1和Chk2可显著增强放疗后凋亡敏感性。     

用MCF-7细胞检测有机磷农药拟雌激素样活性

目的 观察常用有机磷农药对MCF-7细胞增殖以及对雌激素受体基因和pS2基因表达的影响。方法 选用乐果、乙酰甲胺磷、久效磷、马拉硫磷、对硫磷、对氧磷6种有机磷农药进行MCF-7人乳腺癌细胞增殖实验和转录活化实验。结果 6种有机磷农药不能诱导MCF-7人乳腺癌细胞增殖,但乐果却能使pS2基因表达上调。结论 乐果可能具有拟雌激素样活性,且引起pS2基因表达上调不通过雌激素受体介导。     

植酸对人胃癌细胞的生长抑制和凋亡诱导作用的研究

目的了解植酸对人胃癌SGC-7901细胞的生长抑制和诱导凋亡作用。方法MTT法检测植酸在体外对人胃癌SGC-7901细胞的生长抑制作用;AO/EB荧光染色和DNA Ladder实验检测细胞凋亡;免疫组化法检测凋亡调控基因P53蛋白的表达。结果植酸在体外可以明显抑制人胃癌细胞的生长,并诱导细胞发生凋亡。免疫组化实验结果表明,植酸可以抑制SGC-7901细胞中凋亡相关P53蛋白的表达。结论植酸在体外可以抑制人胃癌SGC-7901细胞的生长并诱导细胞发生凋亡,且对于P53蛋白表达的下调作用可能是其诱导细胞凋亡的机制之一。     

Genotoxic effects of green tea extract on human laryngeal carcinoma cells in vitro

Green tea (Camellia sinensis) contains several bioactive compounds which protect the cell and prevent tumour development. Phytochemicals in green tea extract (mostly flavonoids) scavenge free radicals, but also induce pro-oxidative reactions in the cell. In this study, we evaluated the potential cytotoxic and prooxidative effects of green tea extract and its two main flavonoid constituents epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) on human laryngeal carcinoma cell line (HEp2) and its cross-resistant cell line CK2. The aim was to see if the extract and its two flavonoids could increase the sensitivity of the cisplatin-resistant cell line CK2 in comparison to the parental cell line. The results show that EGCG and green tea extract increased the DNA damage in the CK2 cell line during short exposure. The cytotoxicity of EGCG and ECG increased with the time of incubation. Green tea extract induced lipid peroxidation in the CK2 cell line. The pro-oxidant effect of green tea was determined at concentrations higher than those found in traditionally prepared green tea infusions.     

FTY720对人乳腺癌MCF-7细胞、喉癌Hep-2细胞增殖的影响

目的:探讨FTY720抑制人乳腺癌MCF-7细胞和喉癌Hep-2细胞增殖作用。方法:将人乳腺癌MCF-7细胞和喉癌Hep-2细胞用不同浓度FTY720作用48 h,MTT法检测细胞活性,流式细胞术检测其对细胞周期及凋亡率的影响。结果:MTT结果显示,FTY720对乳腺癌MCF-7细胞和喉癌Hep-2细胞增殖均有抑制作用,而且对喉癌Hep-2细胞抑制作用的浓度依赖性高于对乳腺癌细胞的作用;流式细胞术检测结果显示,FTY720可将乳腺癌MCF-7细胞阻滞于G1期,将喉癌Hep-2细胞阻滞于G2/M期,并明显促进乳腺癌MCF-7细胞凋亡。结论:一定浓度的FTY720能明显抑制体外培养的乳腺癌和喉癌细胞增殖,调节其细胞周期,诱导乳腺癌MCF-7细胞凋亡。     

甲基硒酸对乳腺癌细胞增殖及生长影响的研究

目的 观察甲基硒酸对乳腺癌细胞系MCF-7体外增殖及生长的影响.方法 以不同浓度的甲基硒酸作用于乳腺癌细胞系MCF-7,在不同时间内观察不同浓度甲基硒酸对乳腺癌细胞体外增殖、形态、生长的影响.采用噻唑盐法测定细胞的增殖,用光学显微镜观察细胞形态及生长情况.结果 ①甲基硒酸可明显抑制乳腺癌细胞的体外增殖.随着药物浓度的增加,甲基硒酸对乳腺癌细胞体外增殖的抑制作用逐渐增强;随着药物作用时间的增加,甲基硒酸对乳腺癌细胞体外增殖的抑制作用也逐渐增强,但作用48小时后,甲基硒酸的作用不再增强;②甲基硒酸可抑制乳腺癌细胞的生长,使乳腺癌细胞发生核碎裂和核消失现象,随着药物浓度及作用时间的增加,对乳腺癌生长及形态改变的作用也逐渐增强.结论 甲基硒酸可抑制乳腺癌细胞的体外增殖、生长,改变乳腺癌细胞形态,甲基硒酸有望成为预防和治疗乳腺癌的一种新方法.     

Cytotoxic and genotoxic effects of the quercetin/lanthanum complex on human cervical carcinoma cells in vitro

Quercetin is the main flavonoid in diet with a potential in the treatment of cancer, cardiovascular, and neurodegenerative diseases. Due to its specific planar chemical structure, quercetin readily forms chelates with metal ions. Complexes of bioactive compounds and metal ions such as lanthanum often show strong cytotoxic and antitumour properties. The aim of this study was to compare the genotoxic effects of the quercetin/lanthanum complex on human cervical carcinoma cells with compare it to the effects of free ligands, quercetin, and lanthanum alone. The quercetin/lanthanum complex showed considerable cytotoxicity in the concentration range of (100 to 1000) mmol mL-1 and exposure time of three hours. The complex also induced a dose-dependent pro-oxidative effects and the formation of single-strand and double-strand DNA breaks. Although we obtained promising results on the cell level, future experiments should answer whether the quercetin/lanthanum complex is cancer-specific and stable enough in physiological conditions to make a potential new antitumour drug.     

Levels of vitamin a and cellular retinol binding protein in human hepatocellular carcinoma and adjacent normal tissue

The levels of vitamin A (retinol) and vitamin E were measured in the blood, in tissues of human hepatocellular carcinoma (HCC), and in adjacent liver parenchyma. The median values of vitamin A were 11.5 μg/g (ranging 0–82.5 μg/g) in HCC and 52.1 μg/g (ranging 0.4–895.2 μg/g) in normal liver tissues; the difference was statistically significant (p < 0.05). By contrast, there was no significant difference in vitamin E levels between the two tissues. Although the levels of vitamin A were significantly lower in HCC in 10 patients, no significant difference was noted in the cellular retinol binding protein levels in the normal and malignant tissues. These results suggest that the decreased levels of vitamin A in HCC are not due to altered cellular retinol binding protein levels in tumors end the different vitamin A blood supply system. We conclude that either the decreased uptake of vitamin A, but not vitamin E, by HCC cells or the lack of vitamin A‐storing cells in tumors might be responsible for the low levels of vitamin A in HCC.     

Levels of vitamin A and cellular retinol binding protein in human hepatocellular carcinoma and adjacent normal tissue

The levels of vitamin A (retinol) and vitamin E were measured in the blood, in tissues of human hepatocellular carcinoma (HCC), and in adjacent liver parenchyma. The median values of vitamin A were 11.5 micrograms/g (ranging 0-82.5 micrograms/g) in HCC and 52.1 micrograms/g (ranging 0.4-895.2 micrograms/g) in normal liver tissues; the difference was statistically significant (p less than 0.05). By contrast, there was no significant difference in vitamin E levels between the two tissues. Although the levels of vitamin A were significantly lower in HCC in 10 patients, no significant difference was noted in the cellular retinol binding protein levels in the normal and malignant tissues. These results suggest that the decreased levels of vitamin A in HCC are not due to altered cellular retinol binding protein levels in tumors and the different vitamin A blood supply system. We conclude that either the decreased uptake of vitamin A, but not vitamin E, by HCC cells or the lack of vitamin A-storing cells in tumors might be responsible for the low levels of vitamin A in HCC.     

Transport of esterified retinol in fasting human blood

The transport of retinyl palmitate in postabsorptive human blood has been investigated. For this purpose, lipoproteins were isolated from fasting serum of normal subjects as well as of patients with various diseases. The serum retinyl palmitate values of these individuals ranged from 2.0-30.3 micrograms/100 ml, with a mean value of 7.6 micrograms/100 ml. In the 14 human subjects investigated, 68.1% of the recovered retinyl palmitate was associated with the VLDL fraction and 28.9% with the LDL fraction. Nevertheless, the individual pattern of retinyl palmitate distribution among VLDL and LDL differed considerably within this group. No esterified retinol, however, was detected in the HDL as well as in the nonlipoprotein fraction (d greater than 1.21 g/ml) of human serum. It is concluded that the transport of esterified retinol in fasting blood is not restricted to chylomicron remnants. Nevertheless, in humans the serum transport of retinyl palmitate is preferentially mediated by lipoproteins of the VLDL fraction.     

番茄原汁对人前列腺癌PC-3细胞生长抑制作用的研究

目的　探讨番茄原汁对人前列腺癌PC -3细胞生长抑制作用及其可能机制。方法　不同浓度的番茄原汁作用于人前列腺癌PC- 3细胞4 8小时;采用噻唑蓝(MTT)法检测番茄原汁对人前列腺癌PC- 3细胞的生长抑制作用,彗星试验检测PC -3细胞DNA损伤作用。结果　番茄原汁能抑制人前列腺癌PC- 3细胞生长,与对照组相比差异有极显著性;引起PC-3细胞DNA单链断裂,出现拖尾的彗星细胞,拖尾率与尾长随着番茄原汁浓度增大而增加,表现明显的剂量反应关系。结论　番茄原汁对PC- 3细胞生长抑制作用的机理可能与其诱导人前列腺癌PC-3细胞DNA损伤的有关     

Genistein and β-carotene enhance the growth-inhibitory effect of trichostatin A in A549 cells

Background  

The combination of anti-cancer drugs with nutritional factors is a potential strategy for improving the efficacy and decreasing the toxicity of chemotherapy. However, whether nutritional factors enhance the effect of trichostatin A (TSA), a novel anti-cancer drug, is unclear.     

Dietary isothiocyanates inhibit the growth of human bladder carcinoma cells

Many isothiocyanates (ITCs), some of which are abundant in cruciferous vegetables, have been repeatedly shown to inhibit carcinogenesis in a variety of rodent organs. However, several naturally occurring ITCs also promoted bladder tumorigenesis in rodents, raising the question of whether ITCs behave differently in bladder cells. Alternatively, the observed carcinogenic effects of ITCs may result from prolonged exposure of the bladder epithelium, where the tumors originate, to high concentrations of electrophilic ITCs in the urine. Ingested ITCs are almost exclusively excreted and highly concentrated in the urine as N-acetylcysteine conjugates (NAC-ITC). While several NAC-ITCs also are known anticarcinogens, they are unstable and readily dissociate into parent ITCs. In this study, ITCs, including those that have carcinogenic potential in the rodent bladders, induced apoptosis and/or arrested cell-cycle progression in 2 human bladder carcinoma lines (UM-UC-3 and T24) at 7.5-30 micromol/L. Multiple caspases, including caspase-9, -8, and -3, as well as poly(ADP-ribose)polymerase, were cleaved upon ITC exposure. The ITCs blocked cell-cycle progression at the G(2)/M and/or S phases in these cells and downregulated several cell-cycle regulators. However, further increases in ITC concentrations abolished their activities, described above. These findings show that urinary ITC concentrations may need to be maintained at low micromolar concentrations for bladder cancer prevention.     

Beta-carotene uptake and bioconversion to retinol differ between human melanocytes and keratinocytes.

beta-Carotene is one of the carotenoids that has been considered to play a role in the natural defense against ultraviolet-induced skin cancer. It is not known whether epidermal cells are able to accumulate beta-carotene and, subsequently, convert it to vitamin A. We used normal cultured human keratinocytes and melanocytes to study the uptake, and possible bioconversion to retinol, of authentic or [14C]beta-carotene. The uptake was much higher in melanocytes than in keratinocytes, corresponding to a fivefold difference in the intracellular fraction after two days of incubation. An increased level of cellular retinol was noted after one day of beta-carotene incubation. The conversion of [14C]beta-carotene to [14C]retinol peaked at 24 hours of incubation in keratinocytes and melanocytes. The results suggest that beta-carotene can function as a local supply of vitamin A in the skin and that melanocytes are especially likely to store beta-carotene.