二甲双胍在肿瘤治疗中的机制研究进展

作为胰岛素增敏剂的降糖药物二甲双胍具有抗肿瘤的多种生物活性,它能够抑制肿瘤细胞的增殖、促进凋亡、增强肿瘤对化疗药物的敏感性、并且能逆转部分肿瘤细胞对化疗药物的耐药性、甚至还能抑制肿瘤新生血管的生成.这些生物功能的实现依赖于AMPK等相关的信号通路的活化,进而负向调控mTOR通路信号分子的表达,再通过转录因子的表达调控相关靶基因的表达.因此这些信号分子的活化或抑制就成为了新的抗肿瘤治疗的靶点.肿瘤干细胞也是近年来研究的一个热点,二甲双胍能直接杀伤某些肿瘤的干细胞,从而达到有效抑瘤的作用.但二甲双胍杀伤肿瘤干细胞的分子机制不明确.另外.二甲双胍联合激素药物治疗肿瘤,可以增加保守治疗的效果.虽然二甲双胍具有显著的抗肿瘤的多重功效,但其具体的分子机制尚未被清晰完整的阐明,有待进一步的研究和证实.     

二甲双胍在II型糖尿病合并肝癌中的研究进展

多年来二甲双胍以其安全性高、价格低及疗效好的优点而广泛应用于临床治疗糖尿病。糖尿病增加了肝癌的罹患率并影响其预后。近年来研究发现二甲双胍在治疗Ⅱ型糖尿病(T2MD)患者时亦降低了其罹患肝癌的风险,大量研究证明其具有抗癌及协同抗癌作用。现本文对二甲双胍在Ⅱ型糖尿病患者中对肝癌发生的影响进行探讨,对二甲双胍抑制肿瘤的分子生物学机制进行了介绍,列举了最新的实验研究数据,并对现有临床数据进行分析,对于二甲双胍未来的研究方向提出了预期,对于二甲双胍未来在Ⅱ型糖尿病患者中肝癌的预防作用进行了简要的总结及未来使用的展望,对于其在Ⅱ型糖尿病合并肝癌的患者中的治疗作用进行了前瞻性的探讨,为二甲双胍在其他癌症防治中的应用提出了可能性。     

运动与二甲双胍调节肝脏脂代谢的作用机制研究进展

肝脏脂代谢紊乱与2型糖尿病、肥胖症、心血管疾病等多种慢性病密切相关。运动与二甲双胍均可通过作用于不同组织器官调节机体脂代谢,是防治脂代谢异常相关疾病的有效手段。运动可减少肝脏脂质摄入与分泌、降低脂质合成、促进脂肪酸分解,二甲双胍可抑制肝脏糖异生及脂质合成,达到控糖减脂的作用。两者在激活AMPK信号通路、促进肝脏因子分泌方面表现为协同效应,而对线粒体复合物I活性的调节却表现为拮抗效应,两者联合作用于肝脏脂代谢的分子机制有待进一步研究。该文基于运动与二甲双胍调控肝脏脂代谢的生物学机制进行综述,为慢病预防和治疗提供新的思路与策略。     

JBC:研究鉴别出糖尿病药物二甲双胍的新型作用靶点

正近日,一项刊登于国际杂志Journal of Biological Chemistry上的研究报告中,来自日本名古屋大学的研究人员利用线虫作为模式动物进行研究,鉴别出了2型糖尿病药物二甲双胍的新型靶点,研究者发现,在果蝇机体中离子交换蛋白NHX-5和其相关的蛋白质或许是潜在的二甲双胍的靶点,这就表明二甲双胍能够控制细胞内吞作用的周期。2型糖尿病是一种常见的糖尿病类型,患者主要特点表现为胰岛素耐受性及高血糖,很多患者都服用二甲双胍药物来进行治疗,二甲双胍能     

二甲双胍与肝细胞癌

二甲双胍作为一种口服降糖药,已被用于2型糖尿病的一线治疗,有报道指出其可以预防和控制多种癌症的发展。肝细胞癌(肝癌)是原发性肝癌的最常见形式,也是最常见的恶性肿瘤之一。目前,流行病学显示二甲双胍可以降低肝细胞癌的发生风险或改善肝癌患者的预后,实验室研究也证实二甲双胍可抑制肝癌细胞生长。因此文章将探讨二甲双胍抑制肝癌生长的相关机制。     

二甲双胍通过下调c-Myc增强他莫昔芬对乳腺癌的抗肿瘤作用

乳腺癌是一种常见的高度恶性肿瘤,在临床病人的治疗中,寻找有效的抑制肿瘤生长的治疗方法尤为重要。他莫昔芬目前被用于治疗雌激素受体阳性乳腺癌。二甲双胍是一种抗糖尿病药物,据报道可以降低人类癌症发病率,提高乳腺癌患者的生存率。该文主要研究二甲双胍联合他莫昔芬对乳腺癌细胞的协同作用及其机制。采用CCK-8法和平板克隆形成实验检测细胞活力和增殖;流式细胞术检测细胞凋亡; Transwell实验检测细胞迁移、侵袭能力;免疫印迹法检测MAPK信号通路和c-Myc蛋白。结果显示,他莫昔芬与二甲双胍联合用药对乳腺癌细胞增殖、克隆形成、迁移侵袭及凋亡的作用均优于单独用药,表明二甲双胍可以增强他莫昔芬对肿瘤生长的抑制作用,并能下调c-Myc蛋白的表达。该研究结果显示,二甲双胍能明显提高乳腺癌细胞的抗肿瘤作用,这些影响是通过下调c-Myc蛋白介导的。该发现可能对乳腺癌的治疗有潜在的临床应用价值。     

二甲双胍对低级别非侵袭性膀胱肿瘤细胞增殖的影响

目的:初步探讨降糖药物二甲双胍对膀胱肿瘤细胞253J的作用及其相关作用机制。方法:采用Cell Counting Kit-8(CCK-8)试剂盒分析二甲双胍对膀胱肿瘤细胞增殖的影响。应用流式细胞仪检测二甲双胍对细胞周期及凋亡的影响。并通过免疫印迹方法检测相关蛋白确定可能参与其中的信号分子。结果:在各时间点(24小时,48小时,72小时)二甲双胍处理组与对照组相比膀胱肿瘤细胞的增殖受到明显抑制(P0.01或P0.05);与对照组比较,二甲双胍处理组G0/G1期细胞比例上升,S期细胞比例下降(P0.01或P0.05);免疫蛋白印迹发现,二甲双胍处理组中的磷酸化AMP激活的蛋白激酶(AMP-activated protein kinase,AMPK)表达升高,同时细胞周期蛋白D1(cyclin D1)的表达下降(P0.01或P0.05)。结论:体外实验中二甲双胍能够明显抑制膀胱肿瘤细胞的增殖,通过下调cyclin D1的表达诱导细胞周期停滞于G0/G1期。这些结果表明二甲双胍可能成为治疗膀胱癌的潜在药物。     

二甲双胍抗肿瘤效应的基础与临床研究进展

二甲双胍(Metformin)是一种胰岛素增敏剂,临床上主要用于2型糖尿病的治疗。越来越多的证据表明,二甲双胍能够发挥抗肿瘤效应,它通过活化磷酸腺苷蛋白激酶(AMPK),阻断哺乳动物雷帕霉素靶蛋白(m TOR)信号通路抑制肿瘤细胞的生长,并且参与细胞周期、凋亡、血管新生等多种生物学行为。不仅如此,二甲双胍的抗肿瘤临床研究也不断出现,包括大样本回顾性研究和前瞻性研究。这些研究数据不仅为二甲双胍抗肿瘤效应提供了有益的证据支持,也为二甲双胍及其介导的抗肿瘤分子信号途径的阐明奠定了理论依据。     

二甲双胍对人膀胱癌细胞能量代谢的调控作用分析

目的:检测二甲双胍对人膀胱肿瘤细胞能量代谢的作用及分子机制。方法:将膀胱肿瘤细胞分为4组,分别用终浓度为0、20、40、60 mmol/L的二甲双胍处理,比色法检测各组葡萄糖的消耗和乳酸的生成,用ATP检测试剂盒检测各组ATP水平,用JC-1膜电位检测试剂盒检测二甲双胍对膀胱肿瘤细胞膜电位的影响,通过real-time PCR检测己糖激酶2(HK2)和电压依赖性阴离子通道(VDAC)的mRNA表达水平,采用Western印迹检测每组中HK2、VDAC、磷酸化信号转导与转录激活因子3(p-STAT3)的蛋白表达水平变化。结果:在20 mmol/L二甲双胍下,膀胱肿瘤细胞葡萄糖消耗增加,乳酸产生受到抑制,ATP产生和细胞线粒体膜电位降低,HK2、VDAC和p-STAT3的表达降低。结论:二甲双胍可能通过抑制HK2、VDAC和p-STAT3的表达来阻断膀胱肿瘤的糖酵解和线粒体功能,这为研究二甲双胍对肿瘤的抑制作用机制奠定了理论和实验基础。     

二甲双胍抑制H1299细胞迁移及其机制研究

该文主要研究二甲双胍(metformin, Met)对肺腺癌H1299细胞增殖、迁移和凋亡的影响,并探讨其可能作用机制。利用显微镜观察二甲双胍处理后细胞形态,划痕实验检测二甲双胍对细胞迁移的影响; Annexin V/PI标记,流式检测二甲双胍对细胞凋亡的影响; 5-乙炔基-2’脱氧尿嘧啶(Edu)法检测二甲双胍对细胞增殖的影响。结果表明,二甲双胍能改变H1299细胞形态且能显著抑制细胞迁移;二甲双胍不能诱导H1299细胞凋亡;二甲双胍能抑制H1299细胞增殖。进一步研究发现,二甲双胍能下调p-ERK和p-MEK蛋白水平,同时增加E-Cadherin和减少FAK、vimentin蛋白表达,说明二甲双胍主要通过抑制ERK信号通路抑制H1299细胞增殖和迁移,并通过上调E-Cadherin、下调FAK、vimentin使H1299细胞迁移受到明显抑制,为二甲双胍应用于肺腺癌的预防及治疗提供了指导依据。     

Metabolic roles of AMPK and metformin in cancer cells

Metformin is one of the most widely used anti-diabetic agents in the world, and a growing body of evidence suggests that it may also be effective as an anti-cancer drug. Observational studies have shown that metformin reduces cancer incidence and cancer-related mortality in multiple types of cancer. These results have drawn attention to the mechanisms underlying metformin’s anti-cancer effects, which may include triggering of the AMP-activated protein kinase (AMPK) pathway, resulting in vulnerability to an energy crisis (leading to cell death under conditions of nutrient deprivation) and a reduction in circulating insulin/IGF-1 levels. Clinical trials are currently underway to determine the benefits, appropriate dosage, and tolerability of metformin in the context of cancer therapy. This review highlights fundamental aspects of the molecular mechanisms underlying metformin’s anti-cancer effects, describes the epidemiological evidence and ongoing clinical challenges, and proposes directions for future translational research.     

Basal Autophagy and Feedback Activation of Akt Are Associated with Resistance to Metformin-Induced Inhibition of Hepatic Tumor Cell Growth

While accumulating evidence has shown that the use of the diabetic drug metformin may be beneficial against various tumors in some epidemiological studies, a few studies failed to show the same beneficial effects. The molecular and cellular mechanisms for these conflicting observations are not clear. In this study, we compared the inhibitory effects of cell growth by metformin on several hepatic tumor cell lines: SMMC-7721, HCC-97L, HCC-LM3 and HepG2. While metformin inhibited cell growth in all these cells, we found that SMMC-7721, HCC-97L and HCC-LM3 cells were more resistant than HepG2 cells. Mechanistically, we found that metformin inhibited mTOR in all these hepatic tumor cells. However, SMMC-7721 cells had higher levels of basal autophagy and mTORC2-mediated feedback activation of Akt than HepG2 cells, which may render SMMC-7721 cells to be more resistant to metformin-induced inhibition of cell growth. Similarly, HCC-97L and HCC-LM3 cells also had higher feedback activation of AKT than HepG2 cells, which may also account for their resistance to metformin-induced inhibition of cell growth. Therefore, the various basal autophagy and mTOR activity in different cancer cells may contribute to the controversial findings on the use of metformin in inhibition of cancers in humans.     

Effect of metformin on stem cells: Molecular mechanism and clinical prospect

Metformin is a first-line medication for type II diabetes. Numerous studies have shown that metformin not only has hypoglycemic effects, but also modulates many physiological and pathological processes ranging from aging and cancer to fracture healing. During these different physiological activities and pathological changes, stem cells usually play a core role. Thus, many studies have investigated the effects of metformin on stem cells. Metformin affects cell differentiation and has promising applications in stem cell medicine. It exerts anti-aging effects and can be applied to gerontology and regenerative medicine. The potential anti-cancer stem cell effect of metformin indicates that it can be an adjuvant therapy for cancers. Furthermore, metformin has beneficial effects against many other diseases including cardiovascular and autoimmune diseases. In this review, we summarize the effects of metformin on stem cells and provide an overview of its molecular mechanisms and clinical prospects.     

Metformin and cancer: Doses,mechanisms and the dandelion and hormetic phenomena

In the early 1970s, Professor Vladimir Dilman originally developed the idea that antidiabetic biguanides may be promising as geroprotectors and anticancer drugs ("metabolic rehabilitation"). In the early 2000s, Anisimov´s experiments revealed that chronic treatment of female transgenic HER2-/neu mice with metformin significantly reduced the incidence and size of mammary adenocarcinomas and increased the mean latency of the tumors. Epidemiological studies have confirmed that metformin, but not other anti-diabetic drugs, significantly reduces cancer incidence and improves cancer patients' survival in type 2 diabetics. At present, pioneer work by Dilman & Anisimov at the Petrov Institute of Oncology (St. Petersburg, Russia) is rapidly evolving due to ever-growing preclinical studies using human tumor-derived cultured cancer cells and animal models. We herein critically review how the antidiabetic drug metformin is getting reset to metabolically fight cancer. Our current perception is that metformin may constitute a novel "hybrid anti-cancer pill" physically combining both the long-lasting effects of antibodies -by persistently lowering levels of blood insulin and glucose- and the immediate potency of a cancer cell-targeting molecular agent -by suppressing the pivotal AMPK/mTOR/S6K1 axis and several protein kinases at once, including tyrosine kinase receptors such as HER1 and HER2-. In this scenario, we discuss the relevance of metformin doses in pre-clinical models regarding metformin's mechanisms of action in clinical settings. We examine recent landmark studies demonstrating metformin's ability to specifically target the cancer-initiating stem cells from which tumor cells develop, thereby preventing cancer relapse when used in combination with cytotoxic chemotherapy (dandelion hypothesis). We present the notion that, by acting as an efficient caloric restriction mimetic, metformin enhanced intrinsic capacity of mitotically competent cells to self-maintenance and repair (hormesis) might trigger counterintuitive detrimental effects. Ongoing chemopreventive, neoadjuvant and adjuvant trials should definitely establish whether metformin's ability to kill the "dandelion root" beneath the "cancer soil" likely exceeds metformin-related dangers of hormesis.     

Metformin inhibits lung cancer cells proliferation through repressing microRNA-222

Metformin, which is commonly used as an oral anti-hyperglycemic agent of the biguanide family, may reduce cancer risk and improve prognosis. However, the mechanism by which metformin affects various cancers, including lung cancer, remains unknown. MiR-222 induces cell growth and cell cycle progression via direct targeting of p27, p57 and PTEN in cancer cells. In the present study, we used A549 and NCI-H358 human lung cancer cell lines to study the effects and mechanisms of metformin. Metformin treatment reduced expression of miR-222 in these cells (p < 0.05). As a result, protein abundance of p27, p57 and PTEN were increased in cells exposed to metformin. Therefore, these data provide novel evidence for a mechanism that may contribute to the anti-neoplastic effects of metformin suggested by recent population studies and justifying further work to explore potential roles for it in lung cancer treatment.     

Fibroblasts rescue oral squamous cancer cell from metformin-induced apoptosis via alleviating metabolic disbalance and inhibiting AMPK pathway

Metformin is an antidiabetic drug widely used for the treatment of type 2 diabetes. Growing evidence suggests that it may exert antitumor effects in vivo and in vitro. However, even with the promising potency on defeating cancer cells, the pre-clinical and epidemiological studies of metformin on various kinds of cancers are not satisfactory, and the reasons and underlying mechanisms remain unknown. Since cancer is a complex system, dependent on a promoting microenvironment, we hypothesize that the interactions between cancer cells and their neighborhood fibroblasts are essential for metformin resistance. To test this, we used a cell co-culture model closely mimicking the in vivo interactions and metabolic exchanges between normal stromal cells (NOFs) and oral squamous cancer cells (OSCC). Here we show that while metformin can significantly inhibit cell growth and induce apoptosis of OSCC cultured alone in a dose-dependent manner through activating p-AMPK^T172 and modulating Bcl-2, Bax, and cleaved PARP. However, when OSCC are co-cultured with NOFs the metformin effects on OSCC cells are annihilated. NOFs are rescuing OSCC from metformin – induced apoptosis, at least partially, through inhibiting the activity of AMPK and PARP, maintaining mitochondrial membrane potential and increasing the oxidative stress. Our results indicate that metformin effects on oral cancer cells are modulated by the microenvironment and that this has to be taken into consideration in the context of developing a new combination of drugs for oral cancer treatment.     

Metformin induces both caspase-dependent and poly(ADP-ribose) polymerase-dependent cell death in breast cancer cells

There is substantial evidence that metformin, a drug used to treat type 2 diabetics, is potentially useful as a therapeutic agent for cancer. However, a better understanding of the molecular mechanisms through which metformin promotes cell-cycle arrest and cell death of cancer cells is necessary. It will also be important to understand how the response of tumor cells differs from normal cells and why some tumor cells are resistant to the effects of metformin. We have found that exposure to metformin induces cell death in all but one line, MDA-MB-231, in a panel of breast cancer cell lines. MCF10A nontransformed breast epithelial cells were resistant to the cytotoxic effects of metformin, even after extended exposure to the drug. In sensitive lines, cell death was mediated by both apoptosis and a caspase-independent mechanism. The caspase-independent pathway involves activation of poly(ADP-ribose) polymerase (PARP) and correlates with enhanced synthesis of PARP and nuclear translocation of apoptosis-inducing factor (AIF), which plays an important role in mediating cell death. Metformin-induced, PARP-dependent cell death is associated with a striking enlargement of mitochondria. Mitochondrial enlargement was observed in all sensitive breast cancer cell lines but not in nontransformed cells or resistant MDA-MB-231. Mitochondrial enlargement was prevented by inhibiting PARP activity or expression. A caspase inhibitor blocked metformin-induced apoptosis but did not affect PARP-dependent cell death or mitochondrial enlargement. Thus, metformin has cytotoxic effects on breast cancer cells through 2 independent pathways. These findings will be pertinent to efforts directed at using metformin or related compounds for cancer therapy.     

Metformin Treatment Does Not Inhibit Growth of Pancreatic Cancer Patient-Derived Xenografts

There is currently tremendous interest in developing anti-cancer therapeutics targeting cell signaling pathways important for both cancer cell metabolism and growth. Several epidemiological studies have shown that diabetic patients taking metformin have a decreased incidence of pancreatic cancer. This has prompted efforts to evaluate metformin, a drug with negligible toxicity, as a therapeutic modality in pancreatic cancer. Preclinical studies in cell line xenografts and one study in patient-derived xenograft (PDX) models were promising, while recently published clinical trials showed no benefit to adding metformin to combination therapy regimens for locally advanced and metastatic pancreatic cancer. PDX models in which patient tumors are directly engrafted into immunocompromised mice have been shown to be excellent preclinical models for biomarker discovery and therapeutic development. We evaluated the response of four PDX tumor lines to metformin treatment and found that all four of our PDX lines were resistant to metformin. We found that the mechanisms of resistance may occur through lack of sustained activation of adenosine monophosphate-activated protein kinase (AMPK) or downstream reactivation of the mammalian target of rapamycin (mTOR). Moreover, combined treatment with metformin and mTOR inhibitors failed to improve responses in cell lines, which further indicates that metformin alone or in combination with mTOR inhibitors will be ineffective in patients, and that resistance to metformin may occur through multiple pathways. Further studies are required to better understand these mechanisms of resistance and inform potential combination therapies with metformin and existing or novel therapeutics.