Baicalein sensitizes triple negative breast cancer MDA-MB-231 cells to doxorubicin via autophagy-mediated down-regulation of CDK1.

Triple negative breast cancer (TNBC) is a kind of refractory cancer with poor response to conventional chemotherapy. Recently, the combination of baicalein and doxorubicin was reported to exert a synergistic antitumor effect on breast cancer. However, the underlying mechanism how baicalein sensitizes breast cancer cells to doxorubicin remains to be elucidated. Here, it was found that 20 µM baicalein increased the autophagy markers including the ratio of LC3B II/I, GFP-LC3 punctate aggregates and down-regulation of p62 expression, and up-regulated mitophagy marker PINK1 and Parkin in TNBC MDA-MB-231 cells as well. In contrast, doxorubicin decreased the levels of autophagy markers, and significantly up-regulated CDK1 in MDA-MB-231 cells. Pretreatment with baicalein markedly inhibited the doxorubicin-induced decrease in autophagy markers and up-regulation of CDK1, which was reversed by the autophagy inhibitor 3-Methyladenine. Moreover, baicalein alleviated the doxorubicin-induced expression and phosphorylation (at Ser616) of mitochondrial fission protein Drp1. Intriguingly, the autophagy inhibitor 3-Methyladenine also significantly weakened the effect of baicalein on doxorubicin-induced viability decrease and apoptosis in MDA-MB-231 cells. Taken together, our data indicate that baicalein improves the chemosensitivity of TNBC cells to doxorubicin through promoting the autophagy-mediated down-regulation of CDK1, also suggest a novel strategy for prevention of TNBC in the future.

IGF2 contributes to the immunomodulatory effects of exosomes from endometrial regenerative cells on experimental colitis.

BACKGROUND: Exosomes derived from endometrial regenerative cells (ERC-Exos) can inherit the immunomodulatory function from ERCs, however, whether ERC-Exos exhibit such effect on inflammatory bowel diseases with mucosal immune dysregulation has not been explored. Insulin-like growth factor-Ⅱ (IGF2) is considered to possess the potential to induce an anti-inflammatory phenotype in immune cells. In this study, the contribution of IGF2 in mediating the protective efficacy of ERC-Exos on colitis was investigated. METHODS: Lentiviral transfection was employed to obtain IGF2-specific knockout ERC-Exos (IGF2-/--ERC-Exos). Experimental colitis mice induced by dextran sulfate sodium (DSS) were divided into the phosphate-buffered saline (untreated), ERC-Exos-treated and IGF2-/--ERC-Exos-treated groups. Colonic histopathological analysis and intestinal barrier function were explored. The infiltration of CD4+ T cells and dendritic cells (DCs) were analyzed by immunofluorescence staining and flow cytometry. The maturation and function of bone marrow-derived dendritic cells (BMDCs) in different exosome administrations were evaluated by flow cytometry, ELISA and the coculture system, respectively. RESULTS: Compared with the untreated group, ERC-Exos treatment significantly attenuated DSS-induced weight loss, bloody stools, shortened colon length, pathological damage, as well as repaired the weakened intestinal mucosal barrier, including promoting the goblet cells retention, restoring the intestinal barrier integrity and enhancing the expression of tight junction proteins, while the protective effect of exosomes was impaired with the knockout of IGF2 in ERC-Exos. Additionally, IGF2-expressing ERC-Exos decreased the proportions of Th1 and Th17, increased the proportions of Treg, as well as attenuated DC infiltration and maturation in mesenteric lymph nodes and lamina propria of the colitis mice. ERC-Exos were also observed to be phagocytosed by BMDCs and IGF2 is responsible for the modulating effect of ERC-Exos on BMDCs in vitro. CONCLUSIONS: Exosomes derived from ERCs can exert a therapeutic effect on experimental colitis with remarkable alleviation of the intestinal barrier damage and the abnormal mucosal immune responses. We emphasized that IGF2 plays a critical role for ERC-Exos mediated immunomodulatory function and protection against colitis.

Metformin-induced AMPK activation promotes cisplatin resistance through PINK1/Parkin dependent mitophagy in gastric cancer.

Gastric cancer (GC) is one of the most common tumors worldwide, and cisplatin is a standard chemotherapeutic reagent for GC treatment. However, chemoresistance is an inherent challenge which limits its application and effectiveness in clinic. This study aims to investigate the mechanism of metformin-induced cisplatin resistance in GC. Intriguingly, the upregulation of mitophagy markers, mitochondrial fission, autophagy and mitophagosome were observed in SGC-7901/DDP cells compared to those in the SGC-7901 cells. Treatment with metformin significantly increased mitochondrial fission and mitophagy in both AGS and SGC-7901 cells, resulting in decreased ATP production, which unexpectedly protected GC cells against the cytotoxicity of cisplatin. In contrast, application of Chloroquine and 3-methyladenine, two inhibitors of autophagy, significantly alleviated the protective effect of metformin on SGC-7901 and AGS cells against cytotoxicity of cisplatin. Moreover, metformin also stimulated the phosphorylation of AMPK (Thr172) and increased the expression of mitophagy markers including Parkin and PINK1 in the AMPK signaling-dependent manner. Consistently, the cell viability and cell apoptosis assay showed that metformin-induced cisplatin resistance was prevented by knockdown of AMPKα1. Taken together, all data in this study indicate that metformin induced AMPK activation and PINK1/Parkin dependent mitophagy, which may contribute to the progression of cisplatin resistance in GC.