Anticancer property of sediment actinomycetes against MCF-7 and MDA-MB-231 cell lines

Objective:To investigate the anticancer property of marine sediment actinomvceles against two different breast cancer cell lines.Methods:In vitro anticancer activity was carried out against breast(MCF-7 and MDA-MB-231)cancer cell lines.Partial sequences of the 16s rRNA gene,phylogenetic tree construction,multiple sequence analysis and secondary structure analysis were also carried out with the actinomycetes isolates.Results:Of the selected five actinomycete isolates,ACT01 and ACT02 showed the IC_(50)value with(10.13±0.92)and(22.34±5.82)μg/mL concentrations,respectively for MCF-7 cell line at 48 h,but ACT01 showed the minimum(18.54±2.49μg/mL)level of IC_(50)value with MDA-MB-231 cell line.Further,the 16s rRNA partial sequences of ACT01,ACT02,ACT03,ACT04 and ACT05 isolates were also deposited in NCBI data bank with the accession numbers of GQ478246,GQ478247,GQ478248,GQ478249 and GQ478250.respectively.The phylogenetic tree analysis showed that,the isolates of ACT02 and ACT03 were represented in groupⅠandⅢ,respectively,but ACT01 and ACT02 were represented in groupⅡ.The multiple sequence alignment of the actinomycete isolates showed that,the maximum identical conserved regions were identified with the nucleotide regions of 125 to 221st base pairs,65 to 119th base pairs and 55,48 and 31st base pairs.Secondary structure prediction of the 16s rRNA showed that,the maximum free energy was consumed with ACT03 isolate(-45.4 kkal/mol)and the minimum free energy was consumed with ACT04 isolate(-57.6 kkal/mol).Conclusions:The actinomycete isolates of ACT01 and ACT02(GQ478246 and GQ478247)which are isolated from sediment sample can be further used as anticancer agents against breast cancer cell lines.

Sensitivity Evaluation of Two Human Breast Cancer Cell Lines to Tamoxifen through Apoptosis Induction

Tamoxifen citrate (TAM) has been used to treat breast cancer in women for many years. The com-parative effects of TAM in inducing apoptosis were evaluated in estrogen receptor-positive (ER- positive MCF-7) and estrogen receptor-negative (ER-negative MDA-MB-231) human breast cancer cell lines in vitro in order to determine if these two cell lines differ in their sensitivity to TAM. Mi-tochondrial membrane permeability potential disruption was assessed in both cell lines by a lip-ophilic cationic dye (DePsipher assay, Trevigen, Inc.) utilizing fluorescence microscopy. Using this specific fluorochrome, we were able to associate mitochondrial membrane disruption to early, mid-, and late apoptotic cells. TAM induced cell death via apoptosis in both ER-positive and ER- negative cells, however, apoptosis induction was more pronounced in ER-positive MCF-7 compared to ER-negative MDA-MB-231 breast cancer cells. These findings may have some therapeutic use in the treatment of estrogen dependent and estrogen independent breast cancer.

姜黄素纳米粒子抑制乳腺癌细胞MCF-7活性的光学检测

采用纳米材料两亲嵌段共聚物聚乙二醇-聚已内酯(MPEG-PCL)将姜黄素包裹形成一种新型姜黄素纳米粒子。然后基于光学显微成像技术,比较姜黄素和姜黄素纳米粒子抑制乳腺癌细胞MCF-7的活性.通过激光共焦显微成像观察和检测姜黄素在细胞中的荧光强度比较MCF-7细胞系对姜黄素和姜黄素纳米粒子的摄取效率.结果表明姜黄素纳米粒子抑制癌细胞活性效果比较明显(P<0.01),MCF-7细胞系对姜黄素纳米粒子的摄取量大约为未包裹姜黄素的4倍,研究结果有助于促进纳米药物的研发及其在癌症治疗中的应用.

Tetrandrine:A Potent Abrogator of G_2 Checkpoint Function in Tumor Cells and Its Mechanism

Objective To assess the ability of tetrandrine （Tet） to enhance the sensitivity to irradiation and its mechanism in cell lines of human breast cancer p53-mutant MCF-7/ADR, p53-wild-type MCF-7 and human colon carcinoma p53-mutant HT-29 as well as in C26 colorectal carcinoma-bearing BALB/c mice. Methods MCF-7/ADR, HT-29 and MCF-7 cells were exposed to irradiation in the absence or presence of tetrandrine. The effect of Tet on the cytotoxicity of X-irradiation in these three cells was determined and the effect of tetrandrine on cell cycle arrest induced by irradiation in its absence or presence was studied by flow cytometry. Moreover, mitotic index measurement determined mitosis of cells to enter mitosis. Western blotting was employed to detect cyclin B1 and Cdc2 proteins in extracts from irradiated or non-irradiated cells of MCF-7/ADR, HT-29 and MCF-7 treated with tetrandrine at various concentrations. Tumor growth delay assay was conducted to determine the radio-sensitization of tetrandrine in vivo. Results Clonogenic assay showed that tetrandrine markedly enhanced the lethal effect of X-rays on p53-mutant MCF-7/ADR and HT-29 cells and the sensitization enhancement ratio （SER） of tetrandrine was 1.51 and 1.63, but its SER was only 1.1 in p53-wt MCF-7 cells. Irradiated p53-mutant MCF-7/ADR and HT-29 cells were only arrested in G2/M phase while MCF-7 cells were arrested in G1 and G2/M phases. Radiation-induced G2 phase arrests were abrogated by tetrandrine in a concentration-dependent manner in MCF-7/ADR and HT-29 cells, whereas redistribution within MCF-7 cell cycle changed slightly. The proportion of cells in M phase increased from 1.3% to 14.7% in MCF-7/ADR cells, and from 1.5% to 13.2% in HT-29 cells, but 2.4% to 7.1% in MCF-7 cells. Furthermore, the levels of cyclin B 1 and Cdc2 expression decreased after X-irradiation in MCF-7/ADR and HT-29 cells, and the mitotic index was also lower. Tet could reverse the decrease and induce the irradiated cells to enter mitosis （M phase）. Endosomatic experiment showed that tetrandrine caused tumor growth delay in irradiated mice. Conclusion Tetrandrine boosts the cell killing activity of irradiation both in vitro and in vivo. Tetrandrine is a potent abrogator for G2 checkpoint control and can sensitize the cells to radiation.

MiR-142-3p enhances chemosensitivity of breast cancer cells and inhibits autophagy by targeting HMGB1

MiR-142-3p has been reported to act as a tumor suppressor in breast cancer.However,the regulatory effect of miR-142-3p on drug resistance of breast cancer cells and its underlying mechanism remain unknown.Here,we found that miR-142-3p was significantly downregulated in the doxorubicin(DOX)-resistant MCF-7 cell line(MCF-7/DOX).MiR-142-3p overexpression increased DOX sensitivity and enhanced DOXinduced apoptosis in breast cancer cells.High-mobility group box 1(HMGB1)is a direct functional target of miR-142-3p in breast cancer cells and miR-142-3p negatively regulated HMGB1 expression.Moreover,overexpres sion of HMGB1 dramatically reversed the promotion of apoptosis and inhibition of autophagy mediated by miR-142-3p up-regulation.In conclusion,miR-142-3p overexpression may inhibit autophagy and promote the drug sensitivity of breast cancer cells to DOX by targeting HMGB 1.The miR-142-3 p/HMGB1 axis might be a novel target to regulate the drug resistance of breast cancer patients.