Effects of endoplasmic reticulum stress on the autophagy, apoptosis, and chemotherapy resistance of human breast cancer cells by regulating the PI3K/AKT/mTOR signaling pathway

Abstract

Nowadays, although chemotherapy is an established therapy for breast cancer, the molecular mechanisms of chemotherapy resistance in breast cancer remain poorly understood. This study aims to explore the effects of endoplasmic reticulum stress on autophagy, apoptosis, and chemotherapy resistance in human breast cancer cells by regulating PI3K/AKT/mTOR signaling pathway. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed to detect the cell viability of six human breast cancer cell lines (MCF-7, ZR-75-30, T47D, MDA-MB-435s, MDA-MB-453, and MDA-MB-231) treated with tunicamycin (5 µM), after which MCF-7 cells were selected for further experiment. Then, MCF-7 cells were divided into the control (without any treatment), tunicamycin (8 µ), BEZ235 (5 µ), and tunicamycin + BEZ235 groups. Cell viability of each group was testified by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Western blotting was applied to determine the expressions of endoplasmic reticulum stress and PI3K/AKT/mTOR pathwayrelated proteins and autophagy-and apoptosis-related proteins. Monodansylcadaverine and Annexin V-fluorescein isothiocyanate/propidium iodide staining were used for determination of cell autophagy and apoptosis. Furthermore, MCF-7 cells were divided into the control (without any treatment), tunicamycin (5 µM), cisplatin (16 µM), cisplatin (16 µM) + BEZ235 (5 µM), tunicamycin (5 µM) + cisplatin (16 µM), and tunicamycin (5 µM) + cisplatin (16 µM) + BEZ235 groups. Cell viability and apoptosis were also evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Annexin V-fluorescein isothiocyanate/propidium iodide staining. In MCF-7 cells treated with tunicamycin, cell viability decreased significantly, but PEAK, eIF2, and CHOP were upregulated markedly and p-PI3K, p-AKT, and p-MTOR were downregulated in dose-and time-dependent manners. In the tunicamycin + BEZ235 group, the cell viability was lower and the apoptosis rate was higher than those of the control and monotherapy groups. Compared with the cisplatin group, the tunicamycin + cisplatin group showed a relatively higher growth inhibition rate; the growth inhibition rate substantially increased in the tunicamycin + cisplatin + BEZ235 group than the tunicamycin + cisplatin group. The apoptosis rate was highest in tunicamycin + cisplatin + BEZ235 group, followed by tunicamycin + cisplatin group and then cisplatin group. Our study provide evidence that endoplasmic reticulum stress activated by tunicamycin could promote breast cancer cell autophagy and apoptosis and enhance chemosensitivity of MCF-7 cells by inhibiting the PI3K/AKT/ mTOR signaling pathway.

Heme oxygenase‐1 induction mediates chemoresistance of breast cancer cells to pharmorubicin by promoting autophagy via PI3K/Akt pathway

“…PI3K/Akt signalling pathway is one of the major upstream cellular signals in breast cancer cells . Zhong et al found that endoplasmic reticulum stress activation could promote breast cancer cell autophagy and apoptosis and enhance chemosensitivity of MCF‐7 cells by inhibiting the PI3K/AKT/mTOR signalling pathway . In current study, we found the HO‐1 up‐regulated by p‐Akt promoted autophagy and pharmorubicin resistance.…”

“…2 Zhong et al found that endoplasmic reticulum stress activation could promote breast cancer cell autophagy and apoptosis and enhance chemosensitivity of MCF-7 cells by inhibiting the PI3K/AKT/mTOR signalling pathway. 19 In current study, we found the HO-1 up-regulated by p-Akt promoted autophagy and pharmorubicin resistance. The result suggested that the inhibition of PI3K/Akt signalling pathway might contribute to the pharmorubicin resistance in breast cancers cells.…”

“…Breast cancer is a dominant cause of cancer‐associated death in women worldwide . Although surgery, systemic therapy and radiotherapy have been applied for the clinical treatment of breast cancer, these approaches are limited to some extent, because of potential complications or drug resistance . Thus, growing tumour cell sensitivity to chemotherapeutic drugs is an important goal towards enhancing the therapeutic efficacy of breast cancer, and regulation of tumour‐specific signalling is supposed to provide a complementary and different way .…”

“…3 Although surgery, systemic therapy and radiotherapy have been applied for the clinical treatment of breast cancer, these approaches are limited to some extent, because of potential complications or drug resistance. 19 Thus, growing tumour cell sensitivity to chemotherapeutic drugs is an important goal towards enhancing the therapeutic efficacy of breast cancer, and regulation of tumour-specific signalling is supposed to provide a complementary and different way. 7 In order to explore the molecular functions of autophagy, cell survival as well as drug resistance in breast cancer, this study examined the ability of HO-1 induction to cell survival and pharmorubicin resistance of breast cancer cells and delineated the connection between PI3K/Akt signalling and autophagy in breast cancer cells to offer evidence for the improvement of breast cancertargeted therapies.…”

Inhibiting ROS-TFEB-Dependent Autophagy Enhances Salidroside-Induced Apoptosis in Human Chondrosarcoma Cells

“…Autophagy can function as a cellular housekeeper by removing damaged organelles and recycling macromolecules; therefore, autophagy can protect cancer cells, particularly during malignant transformation and carcinogenesis [12]. A growing body of evidence indicates that autophagy can help human cancer cells survive by conferring apoptosis resistance, and inhibition of autophagy causes caspase-dependent apoptosis cell death, especially in the presence of other therapies [13, 14]. Understanding the interplay between apoptosis and autophagy in tumors is crucial to identify new targets for cancer therapy and improve the therapeutic efficiency.…”