Incretin therapies have received much attention because of their tissue-protective effects, which extend beyond those associated with glycemic control. Cancer is a primary cause of death in patients who have diabetes mellitus. We previously reported antiprostate cancer effects of the glucagonlike peptide-1 (GLP-1) receptor (GLP-1R) agonist exendin-4 (Ex-4). Breast cancer is one of the most common cancers in female patients who have type 2 diabetes mellitus and obesity. Thus, we examined whether GLP-1 action could attenuate breast cancer. GLP-1R was expressed in human breast cancer tissue and MCF-7, MDA-MB-231, and KPL-1 cell lines. We found that 0.1 to 10 nM Ex-4 significantly decreased the number of breast cancer cells in a dose-dependent manner. Although Ex-4 did not induce apoptosis, it attenuated breast cancer cell proliferation significantly and dose-dependently. However, the dipeptidyl peptidase-4 inhibitor linagliptin did not affect breast cancer cell proliferation. When MCF-7 cells were transplanted into athymic mice, Ex-4 decreased MCF-7 tumor size in vivo. Ki67 immunohistochemistry revealed that breast cancer cell proliferation was significantly reduced in tumors extracted from Ex-4-treated mice. In MCF-7 cells, Ex-4 significantly inhibited nuclear factor κB (NF-κB ) nuclear translocation and target gene expression. Furthermore, Ex-4 decreased both Akt and IκB phosphorylation. These results suggest that GLP-1 could attenuate breast cancer cell proliferation via activation of GLP-1R and subsequent inhibition of NF-κB activation.

Cancer is currently one of the major causes of death in patients with type 2 diabetes mellitus. We previously reported the beneficial effects of the glucagon-like peptide-1 receptor agonist exendin-4 against prostate and breast cancer. In the present study, we examined the anti-cancer effect of the sodium-glucose cotransporter 2 (SGLT2) inhibitor ipragliflozin using a breast cancer model. In human breast cancer MCF-7 cells, SGLT2 expression was detected using both RT-PCR and immunohistochemistry. Ipragliflozin at 1-50 μM significantly and dose-dependently suppressed the growth of MCF-7 cells. BrdU assay also revealed that ipragliflozin attenuated the proliferation of MCF-7 cells in a dose-dependent manner. Because the effect of ipragliflozin against breast cancer cells was completely canceled by knocking down SGLT2, ipragliflozin could act via inhibiting SGLT2. We next measured membrane potential and whole-cell current using the patch clamp technique. When we treated MCF-7 cells with ipragliflozin or glucose-free medium, membrane hyperpolarization was observed. In addition, glucose-free medium and knockdown of SGLT2 by siRNA suppressed the glucose-induced whole-cell current of MCF-7 cells, suggesting that ipragliflozin inhibits sodium and glucose cotransport through SGLT2. Furthermore, JC-1 green fluorescence was significantly increased by ipragliflozin, suggesting the change of mitochondrial membrane potential. These findings suggest that the SGLT2 inhibitor ipragliflozin attenuates breast cancer cell proliferation via membrane hyperpolarization and mitochondrial membrane instability.

Currently, cancer is one of major cause of death in patients with type 2 diabetes. We have previously reported the anti-prostate and anti-breast cancer effect of GLP-1R agonist Exendin-4 (Diabetes 2014, Endocrinology 2017). In the present study, we examined the anti-cancer effect of SGLT2 inhibitor ipragliflozin (Ipra) using a breast cancer model. In human breast cancer cell line, MCF-7 cells, SGLT2 expression was detected using both RT-PCR and immunohistochemistry. 1-50nM Ipra significantly and dose-dependently suppressed the growth curve of MCF-7 cells. BrdU assay revealed that Ipra attenuates the proliferation rate of MCF-7 in a dose dependent manner. Further, apoptosis was also induced by Ipra in Tunel assay. Because the anti-breast cancer effect of Ipra was completely canceled by knocking down of SGLT2, this effect could be induced by SGLT2 inhibition by Ipra. We next measured membrane potential and whole cell current using the patch clamp technique. When we treated MCF-7 cell with Ipra or glucose free medium, membrane hyperpolarization was observed. In addition, the replacement of sodium with NMDG and knock-down of SGLT2 by siRNA suppressed glucose induced whole cell current of MCF-7 cell, suggesting that Ipra inhibits sodium and glucose incorporation through SGLT2. Further, mitochondrial membrane protein Bcl-2 was decreased and Bax was increased in western blotting, and JC-1 fluorescence was significantly increased, suggesting the change of mitochondrial membrane potential. These data suggest that SGLT2 inhibitor Ipra induces apoptosis in the breast cancer cell via membrane hyperpolarization and mitochondria dysfunction. Disclosure S. Komatsu: None. T. Nomiyama: Research Support; Self; MSD K.K., Sanofi-Aventis, Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceuticals, Japan.T. Numata: None.T. Kawanami: None.Y. Hamaguchi: None.T. Tanaka: None.R. Inoue: None. T. Yanase: Research Support; Self; MSD K.K., Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceuticals, Japan.

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