Teppei Sakamoto

Effect of the anti-diabetic drug metformin in hepatocellular carcinoma in vitro and in vivo.

Metformin is a commonly used oral anti-hyperglycemic agent of the biguanide family. Recent studies suggest that metformin may reduce cancer risk and improve prognosis. However, the antitumor mechanism of metformin in several types of cancers, including hepatocellular carcinoma (HCC), has not been elucidated. The goal of the present study was to evaluate the effects of metformin on HCC cell proliferation in vitro and in vivo, and to study microRNAs (miRNAs) associated with the antitumor effect of metformin in vitro. We used the cell lines Alex, HLE and Huh7, and normal hepatocytes to study the effects of metformin on human HCC cells. In an in vivo study, athymic nude mice bearing xenograft tumors were treated with metformin or left untreated. Tumor growth was recorded after 4 weeks, and the expression of cell cycle-related proteins was determined. Metformin inhibited the proliferation of Alex, HLE and Huh7 cells in vitro and in vivo. Metformin blocked the cell cycle in G0/G1 in vitro and in vivo. This blockade was accompanied by a strong decrease of G1 cyclins, especially cyclin D1, cyclin E and cyclin-dependent kinase 4 (Cdk4). In addition, microRNA (miRNA) expression was markedly altered by the treatment with metformin in vitro and in vivo. In addition, various miRNAs induced by metformin also may contribute to the suppression of tumor growth. Our results demonstrate that metformin inhibits the growth of HCC, possibly by inducing G1 cell cycle arrest through the alteration of microRNAs.

Galectin-9 suppresses the growth of hepatocellular carcinoma via apoptosis in vitro and in vivo

Galectin-9, a soluble β-galactoside-binding animal lectin, evokes apoptosis in various human cancer cell lines. The galectin-9 antitumor effect against hepatocellular carcinoma (HCC) is, however, unknown. We investigated whether galectin-9 suppresses HCC growth in vitro and in vivo. We assessed the antitumor effect of galectin-9 on HCC cells by conducting WST-8 assay in vitro and xenograft model analysis in vivo. Galectin-9-induced apoptosis was evaluated by FACS and ELISA in vitro and by TUNEL stain in vivo. Cell cycle alteration was profiled by FACS. Caspases were profiled by colorimetry. MicroRNAs related to the galectin-9 antitumor effects were determined using microarrays, and their antitumor effect was confirmed in a transfection study in vitro. The expression levels of the target proteins of the miRNAs extracted above were analyzed by western blot analysis. To summarize the results, galectin-9 inhibited the growth of the HCC cell lines HLE and Li-7 in vitro and Li-7 in vivo inducing apoptosis. Cell cycle turnover was not arrested in HLE and Li-7 cells in vitro. miR-1246 was similarly extracted both in vitro and in vivo, which sensitized Li-7 cells to apoptosis when transfected into the cells. DYRK1A, a target protein of miR-1246 was downregulated in Li-7 cells. Caspase-9 was upregulated in Li-7 cells in vitro and in vivo. In conclusion, galectin-9 inhibited the growth of HCC cells by apoptosis, but not cell cycle arrest, in vitro and in vivo. miR-1246 mediated signals of galectin-9, possibly through miR-1246-DYRK1A-caspase-9 axis. Galectin-9 might be a candidate agent for HCC chemotherapy.

Diabetes mellitus and metformin in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related death worldwide. Diabetes mellitus, a risk factor for cancer, is also globally endemic. The clinical link between these two diseases has been the subject of investigation for a century, and diabetes mellitus has been established as a risk factor for HCC. Accordingly, metformin, a first-line oral anti-diabetic, was first proposed as a candidate anti-cancer agent in 2005 in a cohort study in Scotland. Several subsequent large cohort studies and randomized controlled trials have not demonstrated significant efficacy for metformin in suppressing HCC incidence and mortality in diabetic patients; however, two recent randomized controlled trials have reported positive data for the tumor-preventive potential of metformin in non-diabetic subjects. The search for biological links between cancer and diabetes has revealed intracellular pathways that are shared by cancer and diabetes. The signal transduction mechanisms by which metformin suppresses carcinogenesis in cell lines or xenograft tissues and improves chemoresistance in cancer stem cells have also been elucidated. This review addresses the clinical and biological links between HCC and diabetes mellitus and the anti-cancer activity of metformin in clinical studies and basic experiments.

MicroRNA profiles following metformin treatment in a mouse model of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is one of the most common causes of chronic liver disease and is considered to be a causative factor of cryptogenic cirrhosis and hepatocellular carcinoma. microRNAs (miRNAs) are small non-coding RNAs that negatively regulate messenger RNA (mRNA). Recently, it was demonstrated that the aberrant expression of certain miRNAs plays a pivotal role in liver disease. The aim of the present study was to evaluate changes in miRNA profiles associated with metformin treatment in a NASH model. Eight-week-old male mice were fed a methionine- and choline-deficient (MCD) diet alone or with 0.08% metformin for 15 weeks. Metformin significantly downregulated the level of plasma transaminases and attenuated hepatic steatosis and liver fibrosis. The expression of miRNA-376a, miRNA-127, miRNA-34a, miRNA-300 and miRNA-342-3p was enhanced among the 71 upregulated miRNAs, and the expression of miRNA-122, miRNA-194, miRNA-101b and miRNA-705 was decreased among 60 downregulated miRNAs in the liver of MCD-fed mice when compared with control mice. Of note, miRNA profiles were altered following treatment with metformin in MCD-fed mice. miRNA-376a, miRNA-127, miRNA-34a, miRNA-300 and miRNA-342-3p were down-regulated, but miRNA-122, miRNA-194, miRNA-101b and miRNA-705 were significantly upregulated in MCD-fed mice treated with metformin. miRNA profiles were altered in MCD-fed mice and metformin attenuated this effect on miRNA expression. Therefore, miRNA profiles are a potential tool that may be utilized to clarify the mechanism behind the metformin-induced improvement of hepatic steatosis and liver fibrosis. Furthermore, identification of targetable miRNAs may be used as a novel therapy in human NASH.

Profile of microRNAs associated with aging in rat liver.

Recent studies suggest that small non‑coding microRNAs (miRNAs or miRs) play an important role in the regulation of genes involved in various cellular and developmental processes. However, the expression of miRNAs during the aging process remains largely unknown. The aim of the present study was to analyze miRNA expression profiles in rat livers during the aging process. The livers of male Wistar rats at different stages of development (fetal, aged 3 days, and 1, 2, 4, 8 and 36 weeks of age) were used. Total RNA was extracted from the livers. We analyzed the expression levels of 679 rat miRNA probes. In addition, immunohistochemical staining for proliferating cell nuclear antigen (PCNA) was performed. Several up- and downregulated miRNAs were identified in the rat livers at 7 different fetal developmental stages and at 36 weeks of age. We observed the upregulation of miR‑29a, miR‑29c, miR‑195 and miR‑497, whereas miR‑301a, miR‑148b-3p, miR‑7a, miR‑93, miR‑106b, miR‑185, miR‑450a, miR‑539 and miR‑301b were downregulated in the aging rat livers. The number of PCNA-positive hepatocytes was decreased with age. In conclusion, our findings suggest that these up- and downregulated miRNAs play an important role in aging by regulating cell cycles that are involved in liver senescence. Further investigation is required to reveal additional target genes of the miRNAs expressed in the liver and the roles of miRNAs in the developmental process of aging in the liver.

Galectin-9: An anticancer molecule for gallbladder carcinoma.

Gallbladder cancer (GBC) is the most common and aggressive type of biliary tract cancer. There are various histological types of GBC, and the vast majority of GBC cases are adenocarcinomas. Squamous and adenosquamous carcinomas are rare GBC subtypes that are traditionally considered to be more aggressive and to be associated with a poorer prognosis than adenocarcinoma. Galectin-9 (Gal-9), a tandem-repeat-type galectin, has been reported to induce apoptosis-mediated elimination of various cancers, including hepatocellular carcinoma, cholangiocarcinoma, and hematologic malignancies. Therefore, we investigated the antitumor effects of Gal-9 on GBC in vitro and in vivo. In our in vitro experiments, Gal-9 suppressed cell proliferation in various GBC cell lines but not in the OCUG-1 cell line, which represents a poorly differentiated type of adenosquamous carcinoma. Gal-9 induced the apoptosis of Gal-9-sensitive GBC cells by increasing the levels of caspase-cleaved keratin 18 and phosphorylated p53. However, Gal-9 did not affect the expression of various cell cycle-related proteins. In addition, Gal-9 suppressed tumor growth by implanted human GBC cells in a xenograft model. Furthermore, Gal-9 induced the phosphorylation of the Ephrin type-B receptor, and the microRNA (miRNA) expression profile was markedly altered by Gal-9. Based on these results, various miRNAs might contribute to the suppression of tumor growth. Our data reveal that Gal-9 suppresses the growth of GBC, possibly by inducing apoptosis and altering miRNA expression. Thus, Gal-9 might serve as a therapeutic agent for the treatment of GBC.

Galectin-9 suppresses the proliferation of gastric cancer cells in vitro

Gastric cancer is the second-leading cause of cancer-related mortality worldwide, and the prognosis of advanced gastric cancer remains poor. Galectin-9 (Gal-9) is a tandem-repeat-type galectin that has recently been demonstrated to exert anti-proliferative effects on various types of cancer cells. The aim of our present study was to evaluate the effects of Gal-9 on human gastric cancer cells and the expression levels of microRNAs (miRNAs) associated with the antitumor effects of Gal-9 in vitro. In our initial experiments, Gal-9 suppressed the proliferation of gastric cancer cell lines in vitro. Our data further revealed that Gal-9 increased caspase-cleaved keratin 18 (CCK18) levels in gastric cancer cells. Additionally, Gal-9 reduced the phosphorylation of vascular endothelial growth factor receptor-3 (VEGFR-3) and insulin-like growth factor-1 receptor (IGF-1R). Furthermore, miRNA expression levels were markedly altered with Gal-9 treatment in vitro. In conclusion, Gal-9 suppressed the proliferation of human gastric cancer cells by inducing apoptosis. These findings suggest that Gal-9 could be a potential therapeutic target in the treatment of gastric cancer.

Cancer Therapy Due to Apoptosis: Galectin-9

Dysregulation of apoptosis is a major hallmark in cancer biology that might equip tumors with a higher malignant potential and chemoresistance. The anti-cancer activities of lectin, defined as a carbohydrate-binding protein that is not an enzyme or antibody, have been investigated for over a century. Recently, galectin-9, which has two distinct carbohydrate recognition domains connected by a linker peptide, was noted to induce apoptosis in thymocytes and immune cells. The apoptosis of these cells contributes to the development and regulation of acquired immunity. Furthermore, human recombinant galectin-9, hG9NC (null), which lacks an entire region of the linker peptide, was designed to resist proteolysis. The hG9NC (null) has demonstrated anti-cancer activities, including inducing apoptosis in hematological, dermatological and gastrointestinal malignancies. In this review, the molecular characteristics, history and apoptosis-inducing potential of galectin-9 are described.

MicroRNA profiles in various hepatocellular carcinoma cell lines.

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-associated mortality worldwide. Although surgery is considered the most effective treatment for patients with HCC, its indication is restricted by limited criteria and a high relapse rate following surgery; therefore, systemic chemotherapy is required for patients with advanced-stage HCC to prolong their survival. MicroRNAs (miRNAs) are endogenous non-coding RNAs of 18–22 nucleotides in length. It has been reported that aberrant expression of miRNAs is a feature shared by various types of human cancer. Previous studies have indicated that the modulation of non-coding RNAs, particularly miRNAs, may be a valuable therapeutic target for HCC. The aim of the present study was to elucidate the miRNA profiles associated with differentiation and hepatitis B virus (HBV) infection observed in HCC cell lines. The human Alex, Hep3B, HepG2, HuH1, HuH7, JHH1, JHH2, JHH5, JHH6, HLE, HLF and Li-7 HCC cell lines were used for an miRNA array. Replicate data were analyzed following their classification into: i) Poorly- and well-differentiated human HCC cells and ii) HBV-positive and -negative human HCC cells. Out of the 1,719 miRNAs, 4 were found to be significantly upregulated and 52 significantly downregulated in the poorly-differentiated cells, as compared with the well-differentiated cells. Conversely, in the HBV-positive cells 125 miRNAs were found to be upregulated and 2 downregulated, as compared with the HBV-negative cells. Unsupervised hierarchical clustering analysis with Pearsons correlation revealed that the miRNA expression levels were clustered both together and separately in each group. In conclusion, miRNA profile characterization based on various parameters may be a novel approach to determine the etiology of HCC.

Metformin-suppressed differentiation of human visceral preadipocytes: Involvement of microRNAs

Visceral adipose tissue contributes to the pathophysiology of metabolic syndrome. Metformin has been reported to suppress lipogenesis in a murine preadipocyte cell line. However, the effect of metformin on the differentiation of human visceral adipose tissue remains unknown. MicroRNAs (miRNAs or miRs) have been suggested as therapeutic targets because of their involvement in the differentiation and maturation of fatty cells. The aim of this study was to determine whether metformin suppresses the differentiation of human preadipocytes and to identify miRNAs associated with the regulation of lipid metabolism. Human visceral preadipocytes (HPrAD-vis) were preincubated in growth media and then cultured with differentiation media containing metformin for 1 or 2 weeks. Adipogenic differentiation of the cells was assessed by Oil Red O staining, and soluble adiponectin in the culture media was measured using an enzyme-linked immunosorbent assay. Cell proliferation was assessed using a WST-8 assay, and the gene and protein expression of peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT-enhancer-binding protein α (C/EBPα) was determined by RT-qPCR and western blot analysis, respectively. miRNAs were profiled using human miRNA Oligo chips after total RNA was extracted and labeled. Oil Red O staining showed that metformin suppressed the accumulation of lipid droplets in HPrAD-vis cells. The adiponectin concentration in the culture media was also decreased in metformin-treated cells. The WST-8 assay revealed no effect on proliferation or growth inhibition following metformin treatment, although metformin suppressed the expression of PPARγ and C/EBPα. miRNA profiling further revealed differences between the metformin-treated group and control HPrAD-vis cells. Thus, the findings of the present study demonstrated that metformin suppressed the differentiation of human preadipocytes in vitro and altered the miRNA profile of these cells. Thus, the miRNAs whose expression levels were altered by metformin may contribute to the observed suppression of HPrAD-vis cell differentiation.