ABSTRACT
The purpose of this study was to verify that a combination of mild hyperthermia and docetaxel chemotherapy produces synergistic antitumor effects and to explore the action mechanisms of this treatment approach. The effects of docetaxel on the proliferation of cells from the estrogen receptor (ER)-positive human breast cancer cell line MCF-7 and the ER-negative human breast cancer cell line MDA-MB-453 were examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and effective experimental concentrations of docetaxel were determined. The effects of mild hyperthermia plus docetaxel therapy on apoptosis rate in the MCF-7 and MDA-MB-453 human breast cancer cell lines were analyzed by using flow cytometry with Annexin-V fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining. The effects of these combined treatments on cell cycle progression in the MCF-7 and MDA-MB-453 human breast cancer cell lines were examined by using flow cytometry. The effects of these combined treatments on the expression of apoptosis-related proteins and proteins in the mitogen-activated protein kinase (MAPK) pathways were analyzed by using Western blotting. The effects of these combined treatments on the expression of the heat shock protein 70 (HSP70) and the multi-drug resistance (MDR) gene product P-glycoprotein (Pgp) were examined by using Western blotting. The results showed that the half-maximal inhibitory concentration (IC50) of docetaxel for MCF-7 and MDA-MB-453 cells was 19.57±1.12 and 21.64±2.31 μmol/L respectively. Mild hyperthermia with docetaxel therapy could increase apoptosis rate in the MCF-7 and MDA-MB-453 cells. Apoptosis rate in MCF-7 and MDA-MB-453 cells was increased from (23.66±3.59)% and (18.51±3.17)% in docetaxel treatment group to (47.12±6.73)% and (55.16±7.42)% in mild hyperthermia plus docetaxel group, indicating that the mild hyperthermia and docetaxel therapeutic approaches exhibited significant synergistic antitumor effects. Treatments of mild hyperthermia plus docetaxel induced G2/M cell cycle arrest in the MCF-7 and MDA-MB-453 cells. Western blotting demonstrated that proteins in the MAPK pathway were expressed at higher levels in docetaxel-treated cells following mild hypothermia than those in cells treated with docetaxel alone. As compared with blank control group, cells from the mild hyperthermia plus docetaxel group exhibited significantly decreased B-cell lymphoma 2 (Bcl-2) protein expression but slightly increased Bcl-2-associated X protein (Bax) expression. Western blotting results revealed that HSP70 and Pgp expression levels were significantly increased following mild hypothermia. It was concluded that treatments of mild hyperthermia plus docetaxel inhibited the proliferation of human breast cancer cells, promoted apoptosis of breast cancer cells, and produced synergistic antitumor effects.
ABSTRACT
The purpose of this study was to verify that a combination of mild hyperthermia and docetaxel chemotherapy produces synergistic antitumor effects and to explore the action mechanisms of this treatment approach. The effects of docetaxel on the proliferation of cells from the estrogen receptor (ER)-positive human breast cancer cell line MCF-7 and the ER-negative human breast cancer cell line MDA-MB-453 were examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and effective experimental concentrations of docetaxel were determined. The effects of mild hyperthermia plus docetaxel therapy on apoptosis rate in the MCF-7 and MDA-MB-453 human breast cancer cell lines were analyzed by using flow cytometry with Annexin-V fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining. The effects of these combined treatments on cell cycle progression in the MCF-7 and MDA-MB-453 human breast cancer cell lines were examined by using flow cytometry. The effects of these combined treatments on the expression of apoptosis-related proteins and proteins in the mitogen-activated protein kinase (MAPK) pathways were analyzed by using Western blotting. The effects of these combined treatments on the expression of the heat shock protein 70 (HSP70) and the multi-drug resistance (MDR) gene product P-glycoprotein (Pgp) were examined by using Western blotting. The results showed that the half-maximal inhibitory concentration (IC50) of docetaxel for MCF-7 and MDA-MB-453 cells was 19.57±1.12 and 21.64±2.31 μmol/L respectively. Mild hyperthermia with docetaxel therapy could increase apoptosis rate in the MCF-7 and MDA-MB-453 cells. Apoptosis rate in MCF-7 and MDA-MB-453 cells was increased from (23.66±3.59)% and (18.51±3.17)% in docetaxel treatment group to (47.12±6.73)% and (55.16±7.42)% in mild hyperthermia plus docetaxel group, indicating that the mild hyperthermia and docetaxel therapeutic approaches exhibited significant synergistic antitumor effects. Treatments of mild hyperthermia plus docetaxel induced G2/M cell cycle arrest in the MCF-7 and MDA-MB-453 cells. Western blotting demonstrated that proteins in the MAPK pathway were expressed at higher levels in docetaxel-treated cells following mild hypothermia than those in cells treated with docetaxel alone. As compared with blank control group, cells from the mild hyperthermia plus docetaxel group exhibited significantly decreased B-cell lymphoma 2 (Bcl-2) protein expression but slightly increased Bcl-2-associated X protein (Bax) expression. Western blotting results revealed that HSP70 and Pgp expression levels were significantly increased following mild hypothermia. It was concluded that treatments of mild hyperthermia plus docetaxel inhibited the proliferation of human breast cancer cells, promoted apoptosis of breast cancer cells, and produced synergistic antitumor effects.
Subject(s)
Humans , ATP Binding Cassette Transporter, Subfamily B, Member 1 , Genetics , Metabolism , Antineoplastic Agents , Pharmacology , Apoptosis , Apoptosis Regulatory Proteins , Genetics , Metabolism , Breast Neoplasms , Metabolism , Cell Cycle , HSP70 Heat-Shock Proteins , Genetics , Metabolism , Hot Temperature , MAP Kinase Signaling System , MCF-7 Cells , Receptors, Estrogen , Genetics , Metabolism , Taxoids , PharmacologyABSTRACT
<p><b>OBJECTIVE</b>To elucidate the effect of hSav1 expression on Mst1-mediated apoptosis in HeLa cells.</p><p><b>METHODS</b>Plasmids pCMV-HA-hSav1 and pcDNA/4TO-Flag-Mst1 were constructed and cotransfected into HeLa cells. Triple immunofluorescent labeling of hSav1, Mst1 and nucleus was performed to determine their subcellular localization. Plasmids pCMV-HA-hSav1 and/or pcDNA/4TO-Flag-Mst1 were transfected into HeLa cells, and 36 hours later cisplatin (50 micromol/L) as a pro-apoptotic agent was added for 14 hours. Cell apoptosis was analyzed by annexin V/PI assay.</p><p><b>RESULTS</b>Plasmids pCMV-HA-hSav1 and pcDNA/4TO-Flag-Mst1 were constructed and the authenticity of constructs was verified by sequencing. The binding in vitro showed that hSav1 could be detect from the anti-Mst1 immunoprecipitation complex. The immunofluorescent labeling showed that hSav1 and Mst1 had the same localization in cells. Overexpressed protein hSav1 did not induce a significant cell apoptosis. However, co-expression of hSav1 with Mst1 resulted in a significant increase of apoptosis above the level seen with Mst1 alone (24.5% +/- 2.4% vs. 39.3% +/- 4.0%, P < 0.05).</p><p><b>CONCLUSION</b>Our findings indicate that hSav1 is a newly identified protein that interacts with Mst1 and augments Mst1-mediated apoptosis.</p>