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Cancer is a major cause of death in patients with diabetes. Incretin therapy has received much attention because of its tissue-protective effects. We have previously reported an anti-breast cancer effect of glucagon-like peptide-1 receptor agonist exendin-4 (Ex-4). An anti-cancer effect of metformin is well recognized. Therefore, we examined the effect of combined treatment with Ex-4 and metformin in breast cancer cells. In human breast cancer cell lines MCF-7, MDA-MB-231, and KPL-1, 0.1-10 mM metformin significantly reduced the cell number in growth curve analysis in a dose-dependent manner. Furthermore, combined treatment with 0.1 mM metformin and 10 nM Ex-4 additively attenuated the growth curve progression of breast cancer cells. In a bromodeoxyuridine (BrdU) assay, Ex-4 or metformin significantly decreased breast cancer cell proliferation and further reduction of BrdU incorporation was observed by combined treatment with Ex-4 and metformin, which suggested that Ex-4 and metformin additively decreased DNA synthesis in breast cancer cells. Although apoptotic cells were not observed among Ex-4-treated breast cancer cells, apoptotic cells were clearly detected among metformin-treated breast cancer cells by apoptosis assays. Furthermore, metformin decreased BCL-2 expression in MCF-7 cells. In vivo experiments using a xenograft model showed that Ex-4 and metformin significantly decreased the breast tumor weight and Ki67-positive proliferative cancer cells, and metformin reduced the serum insulin level in mice. These data suggested that Ex-4 and metformin attenuated cell proliferation and metformin induced apoptosis in breast cancer cells. Combined treatment of Ex-4 and metformin may be an optional therapy to inhibit breast cancer progression.

Understanding of the mechanism of adipogenesis is essential for the control of obesity, which predisposes toward numerous health problems. High-mobility group box protein 2 (HMGB2) is a non-histone chromosomal protein that facilitates DNA replication, transcription, recombination, and repair. Here, we studied the role of HMGB2 in adipogenic differentiation. The expression of HMGB2 was measured at the mRNA and protein levels in cultured 3T3-L1 pre-adipocyte cells and during the process of adipogenic differentiation induced bya cocktail of insulin, 3-isobutyl-1-methylxanthine, and dexamethasone. This increased in the early phase and decreased in the late phase of differentiation. However, 3T3-L1 pre-adipocyte cells did not differentiate into adipocytes after the knockdown of HMGB2 expression by small interfering RNA (siRNA). Similarly, mesenchymal stem cells (MSCs) isolated from Hmgb2-/- mice did not express peroxisome proliferator-activated receptor gamma (PPARγ) in response to the adipocyte differentiation cocktail and did not differentiate. Wnt/β-catenin signaling is a negative regulator of adipogenic differentiation. We found that β-catenin expression was downregulated during 3T3-L1 adipogenic differentiation, as expected, but not when endogenous HMBG2 expression was knocked down using siRNA. These results indicate that HMGB2 plays an essential role in the early phase of the differentiation of pre-adipocytes and MSCs, and probably interacts with other regulators, such as PPARγ and Wnt/β-catenin signaling.

Aims/Introduction Incretin therapy is a common treatment for type 2 diabetes mellitus. We have previously reported an anti‐prostate cancer effect of glucagon‐like peptide‐1 receptor (GLP‐1R) agonist exendin‐4. The attenuation of cell proliferation in the prostate cancer cell line was dependent on GLP‐1R expression. Here, we examined the relationship between human prostate cancer severity and GLP‐1R expression, as well as the effect of forced expression of GLP‐1R using a lentiviral vector. Materials and Methods Prostate cancer tissues were extracted by prostatectomy and biopsy. GLP‐1R was overexpressed in ALVA‐41 cells using a lentiviral vector (ALVA‐41‐GLP‐1R cells). GLP‐1R expression was detected by immunohistochemistry and quantitative polymerase chain reaction. Cell proliferation was examined by growth curves and bromodeoxyuridine incorporation assays. Cell cycle distribution and regulators were examined by flow cytometry and western blotting. In vivo experiments were carried out using a xenografted model. Results GLP‐1R expression levels were significantly inversely associated with the Gleason score of human prostate cancer tissues. Abundant GLP‐1R expression and functions were confirmed in ALVA‐41‐GLP‐1R cells. Exendin‐4 significantly decreased ALVA‐41‐GLP‐1R cell proliferation in a dose‐dependent manner. DNA synthesis and G1‐to‐S phase transition were inhibited in ALVA‐41‐GLP‐1R cells. SKP2 expression was decreased and p27Kip1 protein was subsequently increased in ALVA‐41‐GLP‐1R cells treated with exendin‐4. In vivo experiments carried out by implanting ALVA‐41‐GLP‐1R cells showed that exendin‐4 decreased prostate cancer growth by activation of GLP‐1R overexpressed in ALVA41‐GLP‐1R cells. Conclusions Forced expression of GLP‐1R attenuates prostate cancer cell proliferation by inhibiting cell cycle progression in vitro and in vivo. Therefore, GLP‐1R activation might be a potential therapy for prostate cancer., Forced expression of glucagon‐like peptide‐1 receptor attenuates prostate cancer cell proliferation by inhibiting cell cycle progression both in vitro and in vivo. Glucagon‐like peptide‐1 receptor activation might be a potential therapy for not only type 2 diabetes, but also prostate cancer.

Aims: Recently, incretin therapy has attracted increasing attention because of its potential use in tissue-protective therapy. Neuron-derived orphan receptor 1 (NOR1) is a nuclear orphan receptor that regulates vascular smooth muscle cell (VSMC) proliferation. In the present study, we investigated the vascular-protective effect of Exendin-4 (Ex-4), a glucagon-like peptide-1 receptor agonist, by inhibiting NOR1 expression in VSMCs. Methods: We classified 7-week-old male 129X1/SvJ mice into control group and Ex-4 low- and high-dose-treated groups fed normal or high-fat diets, respectively. Endothelial denudation injuries were induced in the femoral artery at 8 weeks of age, followed by the evaluation of neointima formation at 12 weeks of age. To evaluate VSMC proliferation, bromodeoxyuridine incorporation assay and cell cycle distribution analysis were performed. NOR1 and cell cycle regulators were detected using immunohistochemistry, western blotting, quantitative reverse-transcription polymerase chain reaction, and luciferase assays. Results: Ex-4 treatment reduced vascular injury-induced neointima formation compared with controls. In terms of VSMCs occupying the neointima area, VSMC numbers and NOR1-expressing proliferative cells were significantly decreased by Ex-4 in a dose-dependent manner in both diabetic and non-diabetic mice. In vitro experiments using primary cultured VSMCs revealed that Ex-4 attenuated NOR1 expression by reducing extracellular signal-regulated kinase-mitogen-activated protein kinase and cAMP-responsive element-binding protein phosphorylations. Furthermore, in the cell cycle distribution analysis, serum-induced G1–S phase entry was significantly attenuated by Ex-4 treatment of VSMCs by inhibiting the induction of S-phase kinase-associated protein 2. Conclusion: Ex-4 attenuates neointima formation after vascular injury and VSMC proliferation possibly by inhibiting NOR1 expression.

Cancer is a major cause of death in patients with type 2 diabetes mellitus (T2DM) and lung cancer is one of the most prevalent cancers in patients with T2DM. In the present study, we examined the anti-cancer effect of the Sodium-glucose cotransporter 2 (SGLT2) inhibitor, canagliflozin, using a lung cancer model. In lung cancer tissues from non-T2DM human subjects, SGLT2 was detected by immunohistochemistry. SGLT2 mRNA and protein were also detected in A549, H1975 and H520 lung cancer cell lines by RT-PCR and immunohistochemistry, respectively. Canagliflozin at 1–50 µM significantly suppressed the growth of A549 cells in a dose-dependent manner. In BrdU assays, canagliflozin attenuated the proliferation of A549 cells, but did not induce apoptosis. In cell cycle analysis, S phase entry was attenuated by canagliflozin in A549 cells. In in vivo experiments, a xenograft model of athymic mice implanted with A549 lung cancer cells was treated with low and high dose oral canagliflozin. Despite the results of the in vitro experiments, tumor weight was not decreased by canagliflozin. In addition, the serum insulin level, but not body weight or blood glucose level, was decreased by canagliflozin. The number of cells positive for Ki67 was slightly decreased by canagliflozin, but this was not statistically significant. In conclusion, SGLT2 is expressed in human lung cancer tissue and cell lines, and the SGLT2 inhibitor, canagliflozin, attenuated proliferation of A549 lung cancer cells by inhibiting cell cycle progression in vitro but not in vivo.

The high-mobility group A protein 1a (HMGA1a) protein is known as an oncogene whose expression level in cancer tissue correlates with the malignant potential, and known as a component of senescence-related structures connecting it to tumor suppressor networks in fibroblasts. HMGA1 protein binds to DNA, but recent studies have shown it exerts novel functions through RNA-binding. Our previous studies have shown that sequence-specific RNA-binding of HMGA1a induces exon-skipping of Presenilin-2 exon 5 in sporadic Alzheimer disease. Here we show that HMGA1a induced exon-skipping of the estrogen receptor alpha (ERα) gene and increased ERα46 mRNA expression in MCF-7 breast cancer cells. An RNA-decoy of HMGA1a efficiently blocked this event and reduced ERα46 protein expression. Blockage of HMGA1a RNA-binding property consequently induced cell growth through reduced ERα46 expression in MCF-7 cells and increased sensitivity to tamoxifen in the tamoxifen-resistant cell line, MCF-7/TAMR1. Stable expression of an HMGA1a RNA-decoy in MCF-7 cells exhibited decreased ERα46 protein expression and increased estrogen-dependent tumor growth when these cells were implanted in nude mice. These results show HMGA1a is involved in alternative splicing of the ERα gene and related to estrogen-related growth as well as tamoxifen sensitivity in MCF-7 breast cancer cells.

We previously identified the selective androgen receptor (AR) modulator S42, which does not stimulate prostate growth but has a beneficial effect on lipid metabolism. In the prostate cancer (PC) cell line LNCaP, S42 did not induce AR transactivation but antagonized 5α-dihydrotestosterone (DHT)‒induced AR activation. Next, we investigated whether S42 suppresses the growth of PC cell lines. Basal growth of LNCaP cells was significantly suppressed by treatment with S42 compared with vehicle, as determined by cell counting and 5-bromo-2'-deoxyuridine assays. The suppressive effect of S42 on cell growth was evident in the AR-positive PC cells LNCaP and 22Rv1 and was slightly observed even in the AR-negative PC-3 cells. However, S42 did not induce apoptosis as determined by the terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling assay. S42 had an even greater suppressive effect on DHT-dependent LNCaP cell proliferation than on basal proliferation (P < 0.05). DHT treatment increased the expression of phosphorylated extracellular signal-regulated kinase (ERK)-mitogen-activated protein kinase (MAPK), a major signaling molecule for PC proliferation, and this was significantly inhibited by S42. DHT also significantly upregulated AR, insulinlike growth factor-1 receptor (IGF-1R), and insulin receptor (IR)-β protein levels, which were similarly reduced by S42 treatment. Importantly, S42 administration to mice attenuated the growth of LNCaP tumors and reduced tumor expression of the prostate-specific antigen, P504S, Ki67, and phosphorylated ERK-MAPK. These data suggest that S42 attenuates LNCaP tumor growth not by inducing apoptosis but by inhibiting the expression of proliferation-related receptors, including IGF-1R, IR, and AR, and by suppressing ERK-MAPK activation. S42 may thus be a feasible candidate for PC treatment.

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.

Cancer is a major cause of death in patients with diabetes. Incretin therapy has received much attention, because of its tissue protective effects beyond glycemic control. We have previously reported anti-prostate cancer effect of Ex-4 and metformin (Diabetes 2014, PLOS ONE 2015). In addition, we have recently reported that Ex-4 attenuates breast cancer growth (Endocrinology 2017). Then, we next examined the effect of combined treatment of Ex-4 with Metformin in breast cancer. In human breast cancer cell lines, MCF-7, MDA-MB-231 and KPL-1 cells, Ex-4 or metformin reduced cell number in a dose-dependent manner. Further, combined treatment of Metformin and Ex-4 additively attenuated the growth curve progression of breast cancer cells. In BrdU assay, Ex-4 or Metformin significantly decreased breast cancer cell proliferation, and further reduction of BrdU incorporation was observed by combined treatment with Ex-4 and Metformin, suggesting that Ex-4 and Metformin additively decreased DNA synthesis in breast cancer cells. Although apoptotic cells were not observed in Ex-4 treated breast cancer cells, apoptotic cells were clearly detected in metformin treated breast cancer cells in TUNEL assay. Further, the experiments using xenograft model mice transplanting MCF-7 cells into athymic mice revealed that Ex-4 and metformin additively attenuated breast cancer growth in vivo also. These data suggest that Ex-4 and metformin attenuates breast cancer cell proliferation and metformin induces apoptosis in breast cancer cells and combined treatment with Ex-4 and metformin could be an optional therapy to inhibit breast cancer progression. Disclosure Y. Fujimura: None. T. Nomiyama: None. C. Iwaya: None. T. Kawanami: None. Y. Hamaguchi: None. T. Tanaka: None. T. Yanase: None.

Incretin therapy is one of the most popular treatment for type 2 diabetes. We have previously reported anti-prostate cancer effect of GLP-1R agonist Exendin-4(Ex-4) (Diabetes 2014, PLOS ONE 2015), and LEADER trial suggested that GLP-1R agonist could reduce prostate cancer. In our previous report, the attenuation of prostate cancer cell proliferation was depending on GLP-1R expression, and Ex-4 did not attenuate cell proliferation in ALVA-41, a prostate cancer cell without intrinsic GLP-1R expression. Then, we next examined anti-prostate cancer effect in ALVA-41 forced expressed GLP-1R using lentivirus vector (ALVA-41-GLP-1R). We confirmed abundant GLP-1R expression in ALVA-41-GLP-1R using RT-PCR and immunohistochemistry, and intracellular cAMP level was increased by Ex-4 in ALVA-41-GLP-1R. Ex-4 significantly decreased the proliferation of ALVA-41-GLP-1R in a dose dependent manner, but not in ALVA-41-control. BrdU assay revealed that DNA synthesis was attenuated in ALVA-41-GLP-1R, and G1 to S phase entry was inhibited in cell cycle distribution in flow cytometry analysis. Further, p27kip protein was increased and Skp2, ubiquitin ligase for p27kip, expression was decreased in ALVA-41-GLP-1R treated by Ex-4. In vivo experiments using xenograft model mice transplanting ALVA-41-GLP-1R revealed that Ex-4 decreased prostate cancer growth via activation of GLP-1R forced expressed in ALVA41. Further, GLP-1R expression level in human prostate cancer tissues was inversely associated with Gleason grading system of human prostate cancer. These data suggested that forced expressed GLP-1R attenuated prostate cancer cell proliferation via inhibiting cell cycle progression in vivo and in vitro, and GLP-1R activation could be one of optional therapy for prostate cancer. Disclosure T. Shigeoka: None. T. Nomiyama: None. T. Kawanami: None. Y. Hamaguchi: None. T. Tanaka: None. S. Irie: None. K. Nabeshima: None. M. Tanaka: None. T. Yanase: None. Funding Japan Society for the Promotion of Science

Recently, the prevention of cardiovascular events has become one of most important purpose of diabetes care. We have previously reported that GLP-1 receptor agonist exendin-4 (BBRC 2011) and DPP-4 inhibitor linagliptin (Cardiovasc Diabetol 2014) attenuate neiontima formation after vascular injury. On the other hand, PPAR agonist is also reported its vascular protective effect. Then, we examined whether selective PPAR alpha agonist pemafibrate could attenuate neointima formation after vascular injury and vascular smooth muscle cell (VSMC) proliferation. We performed endothelial denudation injury in mice treated with high fat diet (HFD) or normal chow. Orally administered pemafibrate significantly attenuated neointima formation after vascular injury in both HFD and normal chow mice. Interestingly, pemafibrate increased serum FGF-21 concentration and decreased serum insulin concentration in HFD mice. In addition, body weight was slightly but significantly decreased by pemafibrate in HFD mice. In vitro experiments, pemafibrate attenuated VSMC proliferation in growth curve in a dose dependent manner, but not another PPAR alpha agonist bezafibrate. This suggested that the attenuation of VSMC proliferation by pemafibrate could be the drug effect, not class effect of PPAR alpha agonist. BrdU assay revealed that pemafibrate inhibited DNA synthesis in VSMC dose-dependently. In cell cycle distribution, G1 to S phase entry was significantly inhibited by pemafibrate in flow cytometry analysis. However, apoptosis was not induced by pemafibrate in VSMC in TUNEL assay. These data suggested that pemafibrate attenuates neiontima formation after vascular injury and VSMC proliferation inhibiting cell cycle progression. Disclosure T. Horikawa: None. T. Nomiyama: None. H. Takahashi: None. T. Kawanami: None. Y. Hamaguchi: None. T. Tanaka: None. T. Yanase: None.

Introduction: In an effort to develop a selective androgen receptor modulator (SARM) with beneficial activity in energy homeostasis, we previously screened 119 steroid analogs for the ability to induce uncoupling protein-1 (UCP-1) mRNA without increasing prostate-specific antigen promoter activity in human prostate cancer cell line, LNCap. As a result, we identified a novel SARM, S42, which is structural analog of testosterone. S42 dose not stimulate prostate growth but has a beneficial effect on lipid metabolism and also increased muscle weight of lavator ani in orchiectomized Sprague-Dawley rats. These findings prompted us to investigate whether S42 has a direct effect on cultured C2C12 myotubes. Method: Mouse myoblast C2C12 were seeded into 6well-plates at 2×105cells/well and maintained in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum (FBS). When the cultured cells became 80-90% confluent, the medium was changed to DMEM supplemented with 2% horse serum (HS) and cells were further cultured for 4 days to induce differentiation into myotubes. Next, the medium was changed to DMEM containing 2% dextran-coated-stripped HS from one day before treatment with various drugs: S42, 5α-dihydrotestosterone (DHT), insulin and rapamycin were tested. Protein and mRNA expression levels were detected by Western blotting and Real time RT-PCR, respectively. Results: Muscle atrophy is mainly controlled by two specific genes encoding muscle ubiquitin ligase, atrogin1 and Muscle RING-Finger Protein1 (MuRF1). S42 significantly lowered expression levels of atrogin1 and MuRF1 in C2C12 myotubes, as determined by Real time RT-PCR. Phosphorylation of p70 S6 kinase (p70S6K), an essential factor for promoting protein synthesis in skeletal muscle, was significantly increased by S42 to almost the same extent as by insulin, but this was prevented by treatment with rapamycin, an inhibitor of mechanistic target of rapamycin complex 1 (mTORC1). However, phosphorylation of Akt upstream regulator mTORC1, was not changed by S42. S42 did not increase insulin-like growth factor 1 (IGF1) mRNA levels in C2C12 myotubes. Conclusion: These results suggest that S42 may have an anabolic effect through activation of mTORC1-p70S6K signaling, independent of IGF1-Akt signaling and may exert an anti-catabolic effect through inhibition of the degradation pathway in cultured C2C12 myotubes.

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.

Pleiotropic benefits of incretin therapy beyond glycemic control have been reported and receiving much attention. Cancer is one of major causes of death in patients with type 2 diabetes. We have previously reported Exendin-4(Ex-4), a glucagon-like peptide-1 receptor agonist, attenuates prostate cancer growth by the inhibition of ERK-MAPK phosphorylation (Diabetes 2014). On the other hand, it is well known that MAPK is inactivated and tightly regulated by MAPK phosphatase (MKP) family. Then, we next examined whether MKP could be involved in the anti-proliferative effect of Ex-4 in the prostate cancer cell. In a human prostate cancer cell line, LNCaP cell, MKP-1 was abundantly expressed. Knocking down of MKP-1 using siRNA abolished Ex-4 induced-reduction of LNCaP cell number in growth curve. In addition, Ex-4 treatment significantly increased MKP-1 mRNA expression. To activate its phosphatase activity, Ser359 in the C terminus of MKP-1 is specifically phosphorylated. Ex-4 significantly phosphorylated Ser359 of MKP-1along with time course of dephosphorylating ERK-MAPK. Using Immunoprecipitation assay, we further confirmed that Ex-4 exactly phosphorylated Ser359 of MKP-1. In addition, if we transiently transfected GFP conjugated MKP-1 into LNCaP cells, nuclear translocation of MKP-1 induced by Ex-4 treatment was observed in early phase stimulation. These data suggest that Ex-4 attenuates prostate cancer cell proliferation via phosphorylation of MKP-1 followed by inhibition of ERK-MAPK activation. Disclosure T. Kawanami: None. T. Nomiyama: Research Support; Self; MSD K.K., Sanofi-Aventis, Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceuticals, Japan. Y. Hamaguchi: None. T. Tanaka: None. T. Yanase: Research Support; Self; MSD K.K., Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceuticals, Japan.

Incretin therapy is one of the most popular treatment for type 2 diabetes. GLP-1R agonist has received much attention, because of its tissue protective effects beyond glycemic control. We have previously reported anti-prostate and anti-breast cancer effect of GLP-1R agonist Exendin-4(Ex-4) (Diabetes 2014, PLOS ONE 2015, Endocrinology 2017). In our previous report, the attenuation of cancer cell proliferation was depending on GLP-1R expression, and Ex-4 did not attenuate cell proliferation in ALVA-41, prostate cancer cell line without GLP-1R expression. Then, we next examined anti-prostate cancer effect in ALVA-41 forced expressed GLP-1R using lentivirus vector (ALVA-41-GLP-1R). We confirmed abundant GLP-1R expression in ALVA-41-GLP-1R using RT-PCR and immunohistochemistry. Ex-4 significantly decreased the proliferation of ALVA-41-GLP-1R in a dose dependent manner, but not in ALVA-41 transfected with control vector (ALVA-41-control), suggesting that forced expressed GLP-1R was intact. In the growth curve, cell number of ALVA-41-GLP-1R was significantly decreased compared with ALVA-41-control. BrdU assay revealed that cell proliferation was attenuated in ALVA-41-GLP-1R, and S Phase entry was inhibited in cell cycle distribution. Further, p27(CDKN1B) expression was increased in ALVA-41-GLP-1R compared with ALVA-41-control in Western Blotting analysis. These data suggest that forced expressed GLP-1R attenuated prostate cancer cell proliferation via inhibiting cell cycle progression. Disclosure T. Shigeoka: None. T. Nomiyama: Research Support; Self; MSD K.K., Sanofi-Aventis, Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceuticals, Japan. T. Kawanami: None. Y. Hamaguchi: None. T. Tanaka: None. T. Yanase: Research Support; Self; MSD K.K., Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceuticals, Japan.

Cancer is a major cause of death in patients with diabetes. Incretin therapy has received much attention, because of its tissue protective effects beyond glycemic control. We have previously reported anti-prostate cancer effect of Ex-4 and metformin (Diabetes 2014, PLOS ONE 2015). In addition, we have recently reported that Ex-4 attenuates breast cancer growth (Endocrinology 2017). Then, we next examined the effect of combined treatment of Ex-4 with Metformin in breast cancer cells. In human breast cancer cell lines, MCF-7, MDA-MB-231 and KPL-1 cell, Ex-4 or metformin reduced cell number in a dose-dependent manner. Further, combined treatment of 0.1mM Metformin and 10nM Ex-4 additively attenuated the growth curve progression of breast cancer cells. In BrdU assay, Ex-4 or Metformin significantly decreased breast cancer cell proliferation, and further reduction of BrdU incorporation was observed by combined treatment of Ex-4 and Metformin, suggesting that Ex-4 and Metformin additively decreased DNA synthesis in breast cancer cells. Although apoptotic cells were not observed in Ex-4 treated breast cancer cells similar to our previous study, apoptotic cells were clearly detected in metformin treated breast cancer cells using TUNEL assay. These data suggest that Ex-4 and metformin attenuates breast cancer cell proliferation and metformin induces apoptosis in breast cancer cells. Combined treatment of Ex-4 and Metformin could be an optional therapy to inhibit breast cancer progression. Disclosure C. Iwaya: None. T. Nomiyama: Research Support; Self; MSD K.K., Sanofi-Aventis, Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceuticals, Japan. T. Kawanami: None. Y. Hamaguchi: None. T. Tanaka: None. T. Yanase: Research Support; Self; MSD K.K., Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceuticals, Japan.

Objectives: The high-mobility group A protein 1a (HMGA1a) protein is known as a transcription factor that binds to DNA, but recent studies have shown it exerts novel functions through RNA-binding. We were prompted to decipher the mechanism of HMGA1a-induced alternative splicing of the estrogen receptor alpha (ERα) that we recently reported would alter tamoxifen sensitivity in MCF-7 TAMR1 cells. Methods: Endogenous expression of full length ERα66 and its isoform ERα46 were evaluated in MCF-7 breast cancer cells by transient expression of HMGA1a and an RNA decoy (2'-O-methylated RNA of the HMGA1a RNA-binding site) that binds to HMGA1a. RNA-binding of HMGA1a was checked by RNA-EMSA. In vitro splicing assay was performed to check the direct involvement of HMGA1a in splicing regulation. RNA-EMSA assay in the presence of purified U1 snRNP was performed with psoralen UV crosslinking to check complex formation of HMGA1a-U1 snRNP at the upstream pseudo-5' splice site of exon 1. Results: HMGA1a induced exon skipping of a shortened exon 1 of ERα in in vitro splicing assays that was blocked by the HMGA1a RNA decoy and sequence-specific RNA-binding was confirmed by RNA-EMSA. RNA-EMSA combined with psoralen UV crosslinking showed that HMGA1a trapped purified U1 snRNP at the upstream pseudo-5' splice site. Conclusions: Regulation of ERα alternative splicing by an HMGA1a-trapped U1 snRNP complex at the upstream 5' splice site of exon 1 offers novel insight on 5' splice site regulation by U1 snRNP as well as a promising target in breast cancer therapy where alternative splicing of ERα is involved.

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.

Recently, pleiotropic benefits of incretin therapy beyond glycemic control have been reported. Although cancer is one of the main causes of death in diabetic patients, few reports describe the anticancer effects of incretin. Here, we examined the effect of the incretin drug exendin (Ex)-4, a GLP-1 receptor (GLP-1R) agonist, on prostate cancer. In human prostate cancer tissue obtained from patients after they had undergone radical prostatectomy, GLP-1R expression colocalized with P504S, a marker of prostate cancer. In in vitro experiments, Ex-4 significantly decreased the proliferation of the prostate cancer cell lines LNCap, PC3, and DU145, but not that of ALVA-41. This antiproliferative effect depended on GLP-1R expression. In accordance with the abundant expression of GLP-1R in LNCap cells, a GLP-1R antagonist or GLP-1R knockdown with small interfering RNA abolished the inhibitory effect of Ex-4 on cell proliferation. Although Ex-4 had no effect on either androgen receptor activation or apoptosis, it decreased extracellular signal–regulated kinase (ERK)-mitogen-activated protein kinase (MAPK) phosphorylation in LNCap cells. Importantly, Ex-4 attenuated in vivo prostate cancer growth induced by transplantation of LNCap cells into athymic mice and significantly reduced the tumor expression of P504S, Ki67, and phosphorylated ERK-MAPK. These data suggest that Ex-4 attenuates prostate cancer growth through the inhibition of ERK-MAPK activation.

Background Recently, glucagon-like peptide-1 (GLP-1)-based therapy, including dipeptidyl peptidase-4 (DPP-4) inhibitors and GLP-1 receptor agonists, has emerged as one of the most popular anti-diabetic therapies. Furthermore, GLP-1-based therapy has attracted increased attention not only for its glucose-lowering ability, but also for its potential as a tissue-protective therapy. In this study, we investigated the vascular-protective effect of the DPP-4 inhibitor, linagliptin, using vascular smooth muscle cells (VSMCs). Methods Six-week-old male C57BL/6 mice were divided into control (n =19) and linagliptin (3 mg/kg/day, n =20) treated groups. Endothelial denudation injuries were induced in the femoral artery at 8 weeks of age, followed by evaluation of neointima formation at 12 weeks. To evaluate cell proliferation of rat aortic smooth muscle cells, a bromodeoxyuridine (BrdU) incorporation assay was performed. Results Linagliptin treatment reduced vascular injury-induced neointima formation, compared with controls (p