Caveolin-1 promotes mitochondrial health and limits mitochondrial ROS through ROCK/AMPK regulation of basal mitophagic flux

Caveolin-1 (CAV1), the main structural component of caveolae, is phosphorylated at tyrosine-14 (pCAV1), regulates signal transduction, mechanotransduction, and mitochondrial function, and plays contrasting roles in cancer progression. We report that CRISPR/Cas9 knockout (KO) of CAV1 increases mitochondrial oxidative phosphorylation, increases mitochondrial potential, and reduces ROS in MDA-MB-231 triple-negative breast cancer cells. Supporting a role for pCAV1, these effects are reversed upon expression of CAV1 phosphomimetic CAV1 Y14D but not non-phosphorylatable CAV1 Y14F. pCAV1 is a known effector of Rho-associated kinase (ROCK) signaling and ROCK1/2 signaling mediates CAV1 promotion of increased mitochondrial potential and decreased ROS production in MDA-MB-231 cells. CAV1/ROCK control of mitochondrial potential and ROS is caveolae-independent as similar results were observed in PC3 prostate cancer cells lacking caveolae. Increased mitochondrial health and reduced ROS in CAV1 KO MDA-MB-231 cells were reversed by knockdown of the autophagy protein ATG5, mitophagy regulator PINK1 or the mitochondrial fission protein Drp1 and therefore due to mitophagy. Use of the mitoKeima mitophagy probe confirmed that CAV1 signaling through ROCK inhibited basal mitophagic flux. Activation of AMPK, a major mitochondrial homeostasis protein inhibited by ROCK, is inhibited by CAV1-ROCK signaling and mediates the increased mitochondrial potential, decreased ROS, and decreased basal mitophagy flux observed in wild-type MDA-MB-231 cells. CAV1 regulation of mitochondrial health and ROS in cancer cells therefore occurs via ROCK-dependent inhibition of AMPK. This study therefore links pCAV1 signaling activity at the plasma membrane with its regulation of mitochondrial activity and cancer cell metabolism through control of mitophagy.

Enhancing the anticancer potential of metformin: fabrication of efficient nanospanlastics, in vitro cytotoxic studies on HEP-2 cells and reactome enhanced pathway analysis

Metformin (MET), an oral antidiabetic drug, was reported to possess promising anticancer effects. We hypothesized that MET encapsulation in unique nanospanlastics would enhance its anticancer potential against HEP-2 cells. Our results showed the successful fabrication of Nano-MET spanlastics (d = 232.10 ± 0.20 nm; PDI = 0.25 ± 0.11; zeta potential = (-) 44.50 ± 0.96; drug content = 99.90 ± 0.11 and entrapment efficiency = 88.01 ± 2.50%). MTT assay revealed the enhanced Nano-MET cytotoxicity over MET with a calculated IC50 of 50 μg/mL and > 500 μg/mL, respectively. Annexin V/PI apoptosis assay showed that Nano-MET significantly decreased the percentage of live cells from 95.49 to 93.70 compared to MET and increased the percentage of cells arrested in the G0/G1 phase by 8.38%. Moreover, Nano-MET downregulated BCL-2 and upregulated BAX protein levels by 1.57 and 1.88 folds, respectively. RT-qPCR revealed that Nano-MET caused a significant 13.75, 4.15, and 2.23-fold increase in caspase-3, -8, and - 9 levels as well as a 100 and 43.47-fold decrease in cyclin D1 and mTOR levels, respectively. The proliferation marker Ki67 immunofluorescent staining revealed a 3-fold decrease in positive cells in Nano-MET compared to the control. Utilizing the combined Pathway-Enrichment Analysis (PEA) and Reactome analysis indicated high enrichment of certain pathways including nucleotides metabolism, Nudix-type hydrolase enzymes, carbon dioxide hydration, hemostasis, and the innate immune system. In summary, our results confirm MET cytotoxicity enhancement by its encapsulation in nanospanlastics. We also highlight, using PEA, that MET can modulate multiple pathways implicated in carcinogenesis.

Discovering Biological Mechanisms of Exceptional Human Health Span and Life Span

Humans age at different rates and families with exceptional longevity provide an opportunity to understand why some people age slower than others. Unique features exhibited by centenarians include a family history of extended life span, compression of morbidity with resultant extension of health span, and longevity-associated biomarker profiles. These biomarkers, including low-circulating insulin-like growth factor 1 (IGF-1) and elevated high-density lipoprotein (HDL) cholesterol levels, are associated with functional genotypes that are enriched in centenarians, suggesting that they may be causative for longevity. While not all genetic discoveries from centenarians have been validated, in part due to exceptional life span being a rare phenotype in the general population, the APOE2 and FOXO3a genotypes have been confirmed in a number of populations with exceptional longevity. However, life span is now recognized as a complex trait and genetic research methods to study longevity are rapidly extending beyond classical Mendelian genetics to polygenic inheritance methodologies. Moreover, newer approaches are suggesting that pathways that have been recognized for decades to control life span in animals may also regulate life span in humans. These discoveries led to strategic development of therapeutics that may delay aging and prolong health span.

Metformin-Induced Receptor Turnover Alters Antibody Accumulation in HER-Expressing Tumors

Metformin has effects beyond its antihyperglycemic properties, including altering the localization of membrane receptors in cancer cells. Metformin decreases human epidermal growth factor receptor (HER) membrane density. Depletion of cell-surface HER decreases antibody-tumor binding for imaging and therapeutic approaches. Here, we used HER-targeted PET to annotate antibody-tumor binding in mice treated with metformin. Methods: Small-animal PET annotated antibody binding in HER-expressing xenografts on administration of an acute versus a daily dose schedule of metformin. Analyses at the protein level in the total, membrane, and internalized cell extracts were performed to determine receptor endocytosis, HER surface and internalized protein levels, and HER phosphorylation. Results: At 24 h after injection of radiolabeled anti-HER antibodies, control tumors had higher antibody accumulation than tumors treated with an acute dose of metformin. These differences were temporal, and by 72 h, tumor uptake in acute cohorts was similar to uptake in control. Additional PET imaging revealed a sustained decrease in tumor uptake on daily metformin treatment compared with control and acute metformin cohorts. The effects of metformin on membrane HER were reversible, and after its removal, antibody-tumor binding was restored. The time- and dose-dependent effects of metformin-induced HER depletion observed preclinically were validated with immunofluorescence, fractionation, and protein analysis cell assays. Conclusion: The findings that metformin decreases cell-surface HER receptors and reduces antibody-tumor binding may have significant implications for the use of antibodies targeting these receptors in cancer treatment and molecular imaging.

The function, mechanisms, and clinical applications of metformin: potential drug, unlimited potentials

Metformin has been used clinically for more than 60 years. As time goes by, more and more miraculous effects of metformin beyond the clinic have been discovered and discussed. In addition to the clinically approved hypoglycemic effect, it also has a positive metabolic regulation effect on the human body that cannot be ignored. Such as anti-cancer, anti-aging, brain repair, cardiovascular protection, gastrointestinal regulation, hair growth and inhibition of thyroid nodules, and other nonclinical effects. Metformin affects almost the entire body in the situation taking it over a long period, and the preventive effects of metformin in addition to treating diabetes are also beginning to be recommended in some guidelines. This review is mainly composed of four parts: the development history of metformin, the progress of clinical efficacy, the nonclinical efficacy of metformin, and the consideration and prospect of its application.

Dietary Folate Deficiency Promotes Lactate Metabolic Disorders to Sensitize Lung Cancer Metastasis through MTOR-Signaling-Mediated Druggable Oncotargets

Lactate metabolism plays a pivotal role in cancers but is often overlooked in lung cancer (LC). Folate deficiency has been linked to lung cancer development, but its impact on lactate metabolism and cancer malignancy is unclear. To investigate this, mice were fed either a folate-deficient (FD) or control diet and intrapleurally implanted with lung cancer cells pre-exposed to FD growth medium. Results showed that FD promoted lactate over-production and the formation of tumor oncospheroids (LCSs) with increased metastatic, migration, and invasion potential. Mice implanted with these cells and fed an FD diet developed hyperlactatemia in blood and lungs. This coincided with increased expression of hexokinase 2 (HK2), lactate dehydrogenase (LDH), and decreased expression of pyruvate dehydrogenase (PDH). Pre-treatment of the FD-LCS-implanted mice with the mTORC1 inhibitor, rapamycin, and the anti-metabolic drug metformin abolished FD/LCS-activated mTORC1 and its targets including HIF1α, HK2, LDH, and monocarboxylate transporters (MCT1 and MCT4), which coincided with the reduction in lactate disorders and prevention of LC metastasis. The findings suggest that dietary FD promotes lactate metabolic disorders that sensitize lung cancer metastasis through mTOR-signaling-mediated targets.

Caveolae Mechanotransduction at the Interface between Cytoskeleton and Extracellular Matrix

The plasma membrane (PM) is subjected to multiple mechanical forces, and it must adapt and respond to them. PM invaginations named caveolae, with a specific protein and lipid composition, play a crucial role in this mechanosensing and mechanotransduction process. They respond to PM tension changes by flattening, contributing to the buffering of high-range increases in mechanical tension, while novel structures termed dolines, sharing Caveolin1 as the main component, gradually respond to low and medium forces. Caveolae are associated with different types of cytoskeletal filaments, which regulate membrane tension and also initiate multiple mechanotransduction pathways. Caveolar components sense the mechanical properties of the substrate and orchestrate responses that modify the extracellular matrix (ECM) according to these stimuli. They perform this function through both physical remodeling of ECM, where the actin cytoskeleton is a central player, and via the chemical alteration of the ECM composition by exosome deposition. Here, we review mechanotransduction regulation mediated by caveolae and caveolar components, focusing on how mechanical cues are transmitted through the cellular cytoskeleton and how caveolae respond and remodel the ECM.

Endosomal trafficking in metabolic homeostasis and diseases

The global prevalences of obesity and type 2 diabetes mellitus have reached epidemic status, presenting a heavy burden on society. It is therefore essential to find novel mechanisms and targets that could be utilized in potential treatment strategies and, as such, intracellular membrane trafficking has re-emerged as a regulatory tool for controlling metabolic homeostasis. Membrane trafficking is an essential physiological process that is responsible for the sorting and distribution of signalling receptors, membrane transporters and hormones or other ligands between different intracellular compartments and the plasma membrane. Dysregulation of intracellular transport is associated with many human diseases, including cancer, neurodegeneration, immune deficiencies and metabolic diseases, such as type 2 diabetes mellitus and its associated complications. This Review focuses on the latest advances on the role of endosomal membrane trafficking in metabolic physiology and pathology in vivo, highlighting the importance of this research field in targeting metabolic diseases.

Metabolic reprogramming of cancer-associated fibroblasts in pancreatic cancer contributes to the intratumor heterogeneity of PET-CT

Intratumor heterogeneity of positron emission tomography-computed tomography (PET-CT) is reflected by variable ¹⁸F-fluorodeoxyglucose (FDG) uptake. Increasing evidence has shown that neoplastic and non-neoplastic components can affect the total ¹⁸F-FDG uptake in tumors. Cancer-associated fibroblasts (CAFs) is considered as the main non-neoplastic components in tumor microenvironment (TME) of pancreatic cancer. Our study aims to explore the impact of metabolic changes in CAFs on heterogeneity of PET-CT. A total of 126 patients with pancreatic cancer underwent PET-CT and endoscopic ultrasound elastography (EUS-EG) before treatment. High maximum standardized uptake value (SUVmax) from the PET-CT was positively correlated with the EUS-derived strain ratio (SR) and indicated poor prognosis of patients. In addition, single-cell RNA analysis showed that CAV1 affected glycolytic activity and correlated with glycolytic enzyme expression in fibroblasts in pancreatic cancer. We also observed the negative correlation between CAV1 and glycolytic enzyme expression in the tumor stroma by using immunohistochemistry (IHC) assay in the SUVmax-high and SUVmax-low groups of pancreatic cancer patients. Additionally, CAFs with high glycolytic activity contributed to pancreatic cancer cell migration, and blocking CAF glycolysis reversed this process, suggesting that glycolytic CAFs promote malignant biological behavior in pancreatic cancer. In summary, our research demonstrated that the metabolic reprogramming of CAFs affects total ¹⁸F-FDG uptake in tumors. Thus, an increase in glycolytic CAFs with decreased CAV1 expression promotes tumor progression, and high SUVmax may be a marker for therapy targeting the neoplastic stroma. Further studies should clarify the underlying mechanisms.

The promising therapeutic effects of metformin on metabolic reprogramming of cancer-associated fibroblasts in solid tumors

Tumor-infiltrated lymphocytes are exposed to many toxic metabolites and molecules in the tumor microenvironment (TME) that suppress their anti-tumor activity. Toxic metabolites, such as lactate and ketone bodies, are produced mainly by catabolic cancer-associated fibroblasts (CAFs) to feed anabolic cancer cells. These catabolic and anabolic cells make a metabolic compartment through which high-energy metabolites like lactate can be transferred via the monocarboxylate transporter channel 4. Moreover, a decrease in molecules, including caveolin-1, has been reported to cause deep metabolic changes in normal fibroblasts toward myofibroblast differentiation. In this context, metformin is a promising drug in cancer therapy due to its effect on oncogenic signal transduction pathways, leading to the inhibition of tumor proliferation and downregulation of key oncometabolites like lactate and succinate. The cross-feeding and metabolic coupling of CAFs and tumor cells are also affected by metformin. Therefore, the importance of metabolic reprogramming of stromal cells and also the pivotal effects of metformin on TME and oncometabolites signaling pathways have been reviewed in this study.

Metformin Induces PRODH/POX-Dependent Apoptosis in Breast Cancer Cells

Although the antineoplastic activity of metformin (MET) is well established, the underlying mechanism of the activity is not understood. Since MET activates AMP kinase (AMPK) and proline dehydrogenase/proline oxidase (PRODH/POX) is stimulated by AMPK ligands (implicated in the regulation of cancer cell survival/apoptosis), the effect of MET on PRODH/POX-dependent apoptosis in wild-type MCF-7 cells (MCF-7^WT) and POX knockdown MCF-7 cells (MCF-7^crPOX cells) was studied. PRODH/POX catalyzes proline degradation generating ROS-induced apoptosis or autophagy. Availability of proline for PRODH/POX functions is regulated by the activity of prolidase (enzyme releasing proline from imidodipeptides), collagen biosynthesis (process consuming proline), and metabolism of proline, ornithine, and glutamic acid. We have found that MET is cytotoxic for MCF-7 cells (IC50∼17 mM), and to the lower extent for MCF-7^crPOX cells (IC50∼28 mM). In MCF-7^WT cells, the effect was accompanied by the inhibition of DNA biosynthesis, collagen biosynthesis, stimulation of ROS formation, AMPKα phosphorylation, and expression of prolidase, p53, caspase 8, caspase 9, and cleaved PARP. In MET-treated MCF-7^crPOX cells, the processes were less affected than in MCF-7^WT cells and the expression of caspase 9 was decreased, while cleaved caspase 8 and cleaved PARP were not detected. The effects were accompanied by an increase in the prolidase activity and proline concentration. The mechanism for MET-induced apoptosis involves the up-regulation of prolidase activity and a decrease in collagen biosynthesis contributing to an increase in the concentration of substrate (proline) for PRODH/POX-dependent ROS formation and activation of caspases −9 and −8. The data suggest that PRODH/POX participates in the MET-induced intrinsic and extrinsic apoptosis in MCF-7 cells.

Proline Dehydrogenase/Proline Oxidase (PRODH/POX) Is Involved in the Mechanism of Metformin-Induced Apoptosis in C32 Melanoma Cell Line

The role of proline dehydrogenase/proline oxidase (PRODH/POX) in the mechanism of antineoplastic activity of metformin (MET) was studied in C32 melanoma cells. PRODH/POX is a mitochondrial enzyme-degrading proline that is implicated in the regulation of cancer cell survival/apoptosis. The enzyme is activated by AMP kinase (AMPK). It has been found that MET induced a significant decrease in cell viability and DNA biosynthesis accompanied by an increase in the expressions of AMPK and PRODH/POX in C32 cells. The mechanism for MET-dependent cytotoxicity on C32 cells was found at the level of PRODH/POX-induced ROS generation and activation of Caspase-3 and Caspase-9 expressions in these cells. The effects were not observed in MET-treated PRODH/POX knock-out C32 cells. Of interest is an MET-dependent increase in the concentration of proline, which is a substrate for PRODH/POX. This phenomenon is due to the MET-dependent inhibition of collagen biosynthesis, which is the main proline-utilizing process. It has been found that the underlying mechanism of anticancer activity of MET involves the activation of AMPK, PRODH/POX, increase in the cytoplasmic concentration of proline, inhibition of collagen biosynthesis, and stimulation of PRODH/POX-dependent ROS generation, which initiate the apoptosis of melanoma cells.

Metformin Treatment or PRODH/POX-Knock out Similarly Induces Apoptosis by Reprograming of Amino Acid Metabolism, TCA, Urea Cycle and Pentose Phosphate Pathway in MCF-7 Breast Cancer Cells

It has been considered that proline dehydrogenase/proline oxidase (PRODH/POX) is involved in antineoplastic activity of metformin (MET). The aim of this study is identification of key metabolites of glycolysis, pentose phosphate pathway (PPP), tricarboxylic acids (TCA), urea cycles (UC) and some amino acids in MET-treated MCF-7 cells and PRODH/POX-knocked out MCF-7 (MCF-7^crPOX) cells. MCF-7^crPOX cells were generated by using CRISPR-Cas9. Targeted metabolomics was performed by LC-MS/MS/QqQ. Expression of pro-apoptotic proteins was evaluated by Western blot. In the absence of glutamine, MET treatment or PRODH/POX-knock out of MCF-7 cells contributed to similar inhibition of glycolysis (drastic increase in intracellular glucose and pyruvate) and increase in the utilization of phospho-enol-pyruvic acid, glucose-6-phosphate and some metabolites of TCA and UC, contributing to apoptosis. However, in the presence of glutamine, MET treatment or PRODH/POX-knock out of MCF-7 cells contributed to utilization of some studied metabolites (except glucose), facilitating pro-survival phenotype of MCF-7 cells in these conditions. It suggests that MET treatment or PRODH/POX-knock out induce similar metabolic effects (glucose starvation) and glycolysis is tightly linked to glutamine metabolism in MCF-7 breast cancer cells. The data provide insight into mechanism of anticancer activity of MET as an approach to further studies on experimental breast cancer therapy.

Caveolin-1 Alleviates Acetaminophen-Induced Fat Accumulation in Non-Alcoholic Fatty Liver Disease by Enhancing Hepatic Antioxidant Ability via Activating AMPK Pathway

Non-alcoholic fatty liver disease (NAFLD) is an independent risk factor for acute liver injury caused by overuse of acetaminophen (APAP). Caveolin-1 (CAV1), a regulator of hepatic energy metabolism and oxidative stress, was found to have a protective effect against NAFLD in our previous study. However, it remains unclear whether CAV1 has a protective effect against APAP-induced hepatotoxicity in NAFLD. The aim of this study was to determine whether CAV1 inhibits oxidative stress through the AMPK/Nrf2/HO-1 pathway to protect the liver from fat accumulation exacerbated by APAP in NAFLD. In this study, seven-week-old C57BL/6 male mice (18–20 g) were raised under similar conditions for in vivo experiment. In vitro, L02 cells were treated with A/O (alcohol and oleic acid mixture) for 48 h, and APAP was added at 24 h for further incubation. The results showed that the protein expression of the AMPK/Nrf2 pathway was enhanced after CAV1 upregulation. The effects of CAV1 on fat accumulation, ROS, and the AMPK/Nrf2 anti-oxidative pathway were reduced after the application of CAV1-siRNA. Finally, treatment with compound C (an AMPK inhibitor) prevented CAV1 plasmid-mediated alleviation of oxidative stress and fat accumulation and reduced the protein level of Nrf2 in the nucleus, demonstrating that the AMPK/Nrf2/HO-1 pathway was involved in the protective effect of CAV1. These results indicate that CAV1 exerted a protective effect against APAP-aggravated lipid deposition and hepatic injury in NAFLD by inhibiting oxidative stress. Therefore, the upregulation of CAV1 might have clinical benefits in reducing APAP-aggravated hepatotoxicity in NAFLD.

Feedback-Driven Mechanisms Between Phosphorylated Caveolin-1 and Contractile Actin Assemblies Instruct Persistent Cell Migration

The actin cytoskeleton and membrane-associated caveolae contribute to active processes, such as cell morphogenesis and motility. How these two systems interact and control directional cell migration is an outstanding question but remains understudied. Here we identified a negative feedback between contractile actin assemblies and phosphorylated caveolin-1 (CAV-1) in migrating cells. Cytoplasmic CAV-1 vesicles display actin-associated motilities by sliding along actin filaments or/and coupling to do retrograde flow with actomyosin bundles. Inhibition of contractile stress fibers, but not Arp2/3-dependent branched actin filaments, diminished the phosphorylation of CAV-1 on site Tyr14, and resulted in substantially increased size and decreased motility of cytoplasmic CAV-1 vesicles. Reciprocally, both the CAV-1 phospho-deficient mutation on site Tyr14 and CAV-1 knockout resulted in dramatic AMPK phosphorylation, further causing reduced active level of RhoA-myosin II and increased active level of Rac1-PAK1-Cofilin, consequently led to disordered contractile stress fibers and prominent lamellipodia. As a result, cells displayed depolarized morphology and compromised directional migration. Collectively, we propose a model in which feedback-driven regulation between actin and CAV-1 instructs persistent cell migration.

Hypoxia-Induced Suppression of Antiapoptotic Bcl-2 Expression in Human Bladder Tumor Cells Is Regulated by Caveolin-1-Dependent Adenosine Monophosphate-Activated Protein Kinase Activity

Purpose

Adenosine monophosphate-activated protein kinase (AMPK) is thought to inhibit cell proliferation or promote cell death, but the details remain unclear. In this study, we propose that AMPK inhibits the expression of anti-apoptotic B-cell lymphoma 2 (Bcl-2) by relying on the hypoxia-inducible factor 1 alpha (HIF-1α)-induced caveolin-1 (Cav-1) expression pathway in noninvasive human bladder tumor (RT4) cells.

Methods

In cells exposed to a hypoxic environment (0.5% oxygen), the levels of expression and phospho-activity of the relevant signaling enzymes were examined via Western blots and reverse transcription-polymerase chain reaction. Cell proliferation was assessed using a Cell Counting Kit-8 assay.

Results

The level of expression of Cav-1 was very low or undetectable in RT4 cells. Hypoxia was associated with significantly decreased cell growth, along with marked induction of HIF-1α and Cav-1 expression; additionally, it suppressed the expression of the antiapoptotic marker Bcl-2 while leaving AMPK activity unchanged. Under hypoxic conditions, HIF-1α acts as a transcription factor for Cav-1 mRNA gene expression. The cell growth and Bcl-2 expression suppressed under hypoxia were reversed along with decreases in the induced HIF-1α and Cav-1 levels by AMPK activation with metformin (1mM) or phenformin (0.1mM). In addition, pretreatment with AMPK small interfering RNA not only increased the hypoxia-induced expression of HIF-1α and Cav-1, but also reversed the suppression of Bcl-2 expression. These results suggest that HIF-1α and Cav-1 expression in hypoxic environments is regulated by basal AMPK activity; therefore, the inhibition of Bcl-2 expression cannot be expected when AMPK activity is suppressed, even if Cav-1 expression is elevated.

Conclusions

For the first time, we find that AMPK activation can regulate HIF-1α induction as well as HIF-1α-induced Cav1 expression, and the hypoxia-induced inhibitory effect on the antiapoptotic pathway in RT4 cells is due to Cav-1-dependent AMPK activity.

Concurrent use of metformin enhances the efficacy of EGFR-TKIs in patients with advanced EGFR-mutant non-small cell lung cancer-an option for overcoming EGFR-TKI resistance

Background

Resistance is almost inevitable and is still a major obstacle in epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) therapy. Only limited relevant clinical studies evaluated the therapeutic effects by combing metformin and EGFR-TKIs in non-small cell lung cancer (NSCLC) patients. Therefore, we evaluated the efficacy of concurrent use of metformin with EGFR-TKIs, and assessed whether the addition of metformin may improve clinical outcomes and delay the occurrence of EGFR-TKI resistance.

Methods

We conducted cell proliferation and apoptosis assay for investigation of metformin in combination with EGFR-TKIs to overcome EGFR-TKI resistance in vitro. Furthermore, we retrospectively reviewed clinicopathological characteristics and therapeutic outcomes of EGFR-mutant advanced NSCLC diabetic patients who received EGFR-TKIs with or without concurrent use of metformin.

Results

In vitro experiment, metformin showed synergistic interaction both with gefitinib in PC9R (CI =0.77) and with osimertinib in PC9R/OR (CI =0.77) in proliferation inhibition assay. Metformin can also augment apoptosis effect of these TKI-resistant cells to EGFR-TKIs. In retrospective cohort, a total of 85 patients were identified (cohort A), in which 28 patients had concurrent use of metformin. The objective response rate in metformin use group was significantly higher (85.7% vs. 47.4%, P=0.001). The median progression-free survival (PFS) and overall survival (OS) in metformin use group were significantly longer (21.6 vs. 9.2 months, P=0.000; 48.4 vs. 36.6 months, P=0.049). Further analysis revealed that metformin obviously prolonged the median PFS2 of osimertinib treatment among patients who progressed to prior line EGFR-TKIs due to secondary EGFR T790M mutation (cohort B).

Conclusions

Our study suggest that concurrent use of metformin could be beneficial to EGFR-mutant NSCLC patients treated with either first-line EGFR-TKIs or second-line osimertinib.

[Research Advance in Anti-lung Cancer Mechanism of Metformin]

二甲双胍作为治疗2型糖尿病的一线用药，安全性及有效性得到证实。近年来流行病学研究发现二甲双胍具有抑制肺癌细胞增殖及转移等特性，有望成为一种新的抗肺癌药物。肺癌是一种严重危害人类健康的疾病，其发病率和死亡率一直居所有恶性肿瘤之首，且预后差。近年来大量证据表明二甲双胍能降低肺癌等肿瘤的发病风险及死亡率，其机制主要包括激活单磷酸腺苷活化的蛋白激酶通路、改善高胰岛素血症及胰岛素抵抗、促进肺癌细胞凋亡、抑制相关炎症反应等。本文就二甲双胍对肺癌的研究做一综述。

Current Status and Application of Metformin for Prostate Cancer: A Comprehensive Review

Metformin, an oral biguanide used for first-line treatment of type 2 diabetes mellitus, has attracted attention for its anti-proliferative and anti-cancer effects in several solid tumors, including prostate cancer (PCa). Liver kinase B1 (LKB1) and adenosine monophosphate-activated protein kinase (AMPK) activation, inhibition of the mammalian target of rapamycin (mTOR) activity and protein synthesis, induction of apoptosis and autophagy by p53 and p21, and decreased blood insulin level have been suggested as direct anti-cancer mechanisms of metformin. Research has shown that PCa development and progression are associated with metabolic syndrome and its components. Therefore, reduction in the risk of PCa and improvement in survival in metformin users may be the results of the direct anti-cancer mechanisms of the drug or the secondary effects from improvement of metabolic syndrome. In contrast, some research has suggested that there is no association between metformin use and PCa incidence or survival. In this comprehensive review, we summarize updated evidence on the relationship between metformin use and oncological effects in patients with PCa. We also highlight ongoing clinical trials evaluating metformin as an adjuvant therapy in novel drug combinations in various disease settings.

Metformin prevents murine ovarian aging

A number of studies have shown that metformin can delay aging process and extend healthy lifespan in animals. However, its role in female reproductive lifespan is unclear. This study was aimed to explore the potential anti-aging effect of metformin on the ovary and its possible mechanisms. Female C57BL/6 mice of 27-week old were divided into two groups, the control group (CON) and metformin-treated group (MET). CON mice were fed ad libitum, while MET mice were fed on chows supplied with 100mg/kg metformin for half a year. Ovarian reserve and function were assessed by ovarian follicle counts, estrous cycle and sex hormones levels. The expressions of oxidized metabolites, such as 8-hydroxy-2´-deoxyguanosine (8-OHdG), 4-hydroxynonenal (4-HNE), nitrotyrosine (NTY), and ovarian aging associated proteins P16, SIRT1, p-rpS6 and Bcl2 were examined. The MET mice exhibited increased level of serum E2 hormone and higher percentage of regular estrous cycles after 6 months' feeding, compared to the CON mice. The amount of primordial and primary follicles and the expression of SIRT1 were significantly increased, but the levels of P16, 8-OHdG, 4-HNE and p-rpS6 were decreased in the MET mice. These results indicate that metformin can delay ovarian aging process, probably by inducing the expression of SIRT1 and reducing the oxidative damage.

Role of Caveolin-1 in Diabetes and Its Complications

It is estimated that in 2017 there were 451 million people with diabetes worldwide. These figures are expected to increase to 693 million by 2045; thus, innovative preventative programs and treatments are a necessity to fight this escalating pandemic disorder. Caveolin-1 (CAV1), an integral membrane protein, is the principal component of caveolae in membranes and is involved in multiple cellular functions such as endocytosis, cholesterol homeostasis, signal transduction, and mechanoprotection. Previous studies demonstrated that CAV1 is critical for insulin receptor-mediated signaling, insulin secretion, and potentially the development of insulin resistance. Here, we summarize the recent progress on the role of CAV1 in diabetes and diabetic complications.

Metformin and Breast Cancer: Molecular Targets

Metformin has been the first-line drug for the treatment of type II diabetes mellitus for decades, being presently the most widely prescribed antihyperglycemic drug. Retrospective studies associate the use of metformin with a reduction in cancer incidence and cancer-related death. However, despite extensive research about the molecular effects of metformin in cancer cells, its mode of action remains controversial. The major molecular targets of metformin include complex I of the mitochondrial electron transport chain, adenosine monophosphate (AMP)-activated protein kinase (AMPK), and mechanistic target of rapamycin complex 1 (mTORC1), but AMPK-independent effects of metformin have also been described. Breast cancer is one of the leading causes of cancer-related morbidity and mortality among women worldwide. Several studies have reinforced a link between breast cancer risk and diabetes. Moreover, metformin significantly reduces breast cancer risk, compared to patients who are not using metformin and is independent of diabetes status. In this review, we summarize the current molecular evidence to elucidate metformin's mode of action against breast cancer cells.

Combined treatment with metformin and gefitinib overcomes primary resistance to EGFR-TKIs with EGFR mutation via targeting IGF-1R signaling pathway

Aim

Although EGFR tyrosine kinase inhibitors (TKIs) have shown dramatic effects against sensitizing EGFR mutations in non-small cell lung cancer (NSCLC), ~20%–30% of NSCLC patients with EGFR-sensitive mutation exhibit intrinsic resistance to EGFR-TKIs. The purpose of the current study was to investigate the enhanced antitumor effect of metformin (Met), a biguanide drug, in combination with gefitinib (Gef) in primary resistant human lung cancer cells and the associated molecular mechanism.

Experimental design

H1975 cell line was treated with Met and/or Gef to examine the inhibition of cell growth and potential mechanism of action by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Ki67 incorporation assay, flow cytometry analysis, small interfering RNA technology, Western blot analysis and xenograft implantation.

Results

Insulin-like growth factor-1 receptor (IGF-1R) signaling pathway was markedly activated in EGFR-TKI primary resistant H1975 cells as compared to EGFR-TKI acquired resistance cells (PC-9GR, H1650-M3) and EGFR-TKI sensitivity cells (PC-9, HCC827). Inhibition of IGF-1R activity by AG-1024 (a small molecule of IGF-1R inhibitor), as well as downregulation of IGF-1R by siRNA, significantly enhanced the ability of Gef to suppress proliferation and induce apoptosis in H1975 cells via the inhibition of AKT activation and subsequent upregulation of Bcl-2-interacting mediator of cell death (BIM). Interestingly, the observation showed that Met combined with Gef treatment had similar tumor growth suppression effects in comparison with the addition of AG-1024 to therapy with Gef. A clear synergistic antiproliferative interaction between Met and Gef was observed with a combination index (CI) value of 0.65. Notably, IGF-1R silencing mediated by RNA interference (RNAi) attenuated anticancer effects of Met without obviously resensitizing H1975 cells to Gef. Finally, Met-based combinatorial therapy effectively blocked tumor growth in the xenograft with TKI primary resistant lung cancer cells.

Conclusion

Our findings demonstrated that Met combined with Gef would be a promising strategy to overcome EGFR-TKI primary resistance via suppressing IGF-1R signaling pathway in NSCLC.

Suppressor of cytokine signalling-2 limits IGF1R-mediated regulation of epithelial-mesenchymal transition in lung adenocarcinoma

Non-small cell lung cancer (NSCLC), including adenocarcinoma and squamous cell carcinoma, is the leading cause of death from lung malignancies and has a poor prognosis due to metastasis. Suppressor of cytokine signalling-2 (SOCS2), a feedback inhibitor of cytokine signalling, has been shown to be involved in growth control. Here, we show that SOCS2 were significantly downregulated in tumour foci in NSCLC patients. The expression levels of SOCS2 significantly correlated with clinical stage, lymph node metastasis, histological subtype and survival time. In particular, the decreased expression of SOCS2 significantly associated with advanced pathological stage, lymph node metastasis and shorter overall survival in lung adenocarcinoma patients. In vivo animal results showed that overexpressed SOCS2 attenuated the metastatic characteristics of lung adenocarcinoma, including by inhibiting the epithelial-mesenchymal transition (EMT). Further functional studies indicated that insulin-like growth factor 1 (IGF1)-driven migratory and invasive behaviours of lung adenocarcinoma cells can be partially suppressed by exogenous SOCS2 expression. Investigations into the mechanism of action revealed that SOCS2 inhibits EMT by inactivating signal transducer and activator of transcription 3 (STAT3) and STAT5 via the competitive binding of SOCS2 to the STAT binding sites on IGF1R. Altogether, our results reveal an important role for SOCS2 dysregulation in the pathogenicity of lung adenocarcinoma, suggest its potential use as a biomarker for diagnosing lung adenocarcinoma, and paves the way to develop novel therapy targets as the axis of SOCS2-IGF1R-STAT in lung adenocarcinoma.

Metformin-induced caveolin-1 expression promotes T-DM1 drug efficacy in breast cancer cells

Trastuzumab emtansine (T-DM1) is an antibody drug conjugate (ADC) that was recently approved for the treatment of HER-2-positive metastatic breast cancer. The drug sensitivity of ADCs depends mainly on the internalization efficiency of the drug. Caveolin-1 was shown to promote T-DM1 internalization and enhance drug sensitivity. Whether caveolin-1 can be overexpressed to improve T-DM1 efficacy is interesting and has the potential for clinical application. In this study, diabetes drug metformin was investigated in terms of induction of caveolin-1 expression for increased efficacy of subsequent T-DM1 application. BT-474 cells were pretreated with metformin, followed by combined therapy with metformin and T-DM1. The T-DM1 internalization and drug efficacy were determined, and the protein expressions for signal transduction were also monitored. Caveolin-1 shRNA was applied to suppress endogenous caveolin-1 expression, and the ability of metformin to promote T-DM1 efficacy was investigated. Result showed that in BT-474 cells pretreated with metformin, cellular caveolin-1 overexpression was induced, which then promoted drug efficacy by enhancing T-DM1 internalization. As cellular caveolin-1 was suppressed by shRNA, the effect of metformin-enhanced T-DM1 cytotoxicity was decreased. This study demonstrated that metformin can be applied prior to T-DM1 treatment to improve the clinical efficacy of T-DM1 by enhancing caveolin-1-mediated endocytosis.

Metformin as a new anti-cancer drug in adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a rare heterogeneous malignancy with poor prognosis. Since radical surgery is the only available treatment, more specific and effective drugs are urgently required. The anti-diabetic drug metformin has been associated with a decreased cancer prevalence and mortality in several solid tumors, prompting its possible use for ACC treatment.

This paper evaluates the in vitro and in vivo anti-cancer effects of metformin using the ACC cell model H295R.

Metformin treatment significantly reduces cell viability and proliferation in a dose- and time-dependent manner and associates with a significant inhibition of ERK1/2 and mTOR phosphorylation/activation, as well as with stimulation of AMPK activity. Metformin also triggers the apoptotic pathway, shown by the decreased expression of Bcl-2 and HSP27, HSP60 and HSP70, and enhanced membrane exposure of annexin V, resulting in activation of caspase-3 apoptotic effector. Metformin interferes with the proliferative autocrine loop of IGF2/IGF-1R, which supports adrenal cancer growth. Finally, in the ACC xenograft mouse model, obtained by subcutaneous injection of H295R cells, metformin intraperitoneal administration inhibits tumor growth, confirmed by the significant reduction of Ki67%.

Our data suggest that metformin inhibits H295R cell growth both in vitro and in vivo. Further preclinical studies are necessary to validate the potential anti-cancer effect of metformin in patients affected by ACC.

Metformin treatment reduces temozolomide resistance of glioblastoma cells

It has been reported that metformin acts synergistically with temozolomide (TMZ) to inhibit proliferation of glioma cells including glioblastoma multiforme (GBM). However, the molecular mechanism underlying how metformin exerts its anti-cancer effects remains elusive. We used a combined experimental and bioinformatics approach to identify genes and complex regulatory/signal transduction networks that are involved in restoring TMZ sensitivity of GBM cells after metformin treatment. First, we established TMZ resistant GBM cell lines and found that the resistant cells regained TMZ sensitivity after metformin treatment. We further identified that metformin down-regulates SOX2 expression in TMZ-resistant glioma cells, reduces neurosphere formation capacity of glioblastoma cells, and inhibits GBM xenograft growth in vivo. Finally, the global gene expression profiling data reveals that multiple pathways are involved in metformin treatment related gene expression changes, including fatty acid metabolism and RNA binding and splicing pathways. Our work provided insight of the mechanisms on potential synergistic effects of TMZ and metformin in the treatment of glioblastoma, which will in turn yield potentially translational value for clinical applications.

Glutathione-mediated antioxidant response and aerobic metabolism: two crucial factors involved in determining the multi-drug resistance of high-risk neuroblastoma

Neuroblastoma, a paediatric malignant tumor, is initially sensitive to etoposide, a drug to which many patients develop chemoresistance. In order to investigate the molecular mechanisms responsible for etoposide chemoresistance, HTLA-230, a human MYCN-amplified neuroblastoma cell line, was chronically treated with etoposide at a concentration that in vitro mimics the clinically-used dose. The selected cells (HTLA-Chr) acquire multi-drug resistance (MDR), becoming less sensitive than parental cells to high doses of etoposide or doxorubicin. MDR is due to several mechanisms that together contribute to maintaining non-toxic levels of H₂O₂. In fact, HTLA-Chr cells, while having an efficient aerobic metabolism, are also characterized by an up-regulation of catalase activity and higher levels of reduced glutathione (GSH), a thiol antioxidant compound. The combination of such mechanisms contributes to prevent membrane lipoperoxidation and cell death. Treatment of HTLA-Chr cells with L-Buthionine-sulfoximine, an inhibitor of GSH biosynthesis, markedly reduces their tumorigenic potential that is instead enhanced by the exposure to N-Acetylcysteine, able to promote GSH synthesis.

Collectively, these results demonstrate that GSH and GSH-related responses play a crucial role in the acquisition of MDR and suggest that GSH level monitoring is an efficient strategy to early identify the onset of drug resistance and to control the patient's response to therapy.

Metformin restores crizotinib sensitivity in crizotinib-resistant human lung cancer cells through inhibition of IGF1-R signaling pathway

Aim

Despite the impressive efficacy of crizotinib for the treatment of ALK-positive non-small cell lung cancer, patients invariably develop therapeutic resistance. Suppression of the IGF-1R signaling pathway may abrogate this acquired mechanism of drug resistance to crizotinib. Metformin, a widely used antidiabetic agent, may reverse crizotinib resistance through inhibition of IGF-1R signaling.

Results

The present study revealed that metformin effectively increased the sensitivity of both crizotinib-sensitive and -resistant non-small cell lung cancer cells to crizotinib, as evidenced by decreased proliferation and invasion and enhanced apoptosis. Metformin reduced IGF-1R signaling activation in crizotinib-resistant cells. Furthermore, the addition of IGF-1 to crizotinib-sensitive H2228 cells induced crizotinib resistance, which was overcome by metformin.

Experimental design

The effects of metformin to reverse crizotinib resistance were examined in vitro by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT), invasion assay, ki67 incorporation assay, flow cytometry analysis, Western blot analysis, and colony-forming assay.

Conclusions

Metformin may be used in combination with crizotinib in ALK+ NSCLC patients to overcome crizotinib resistance and prolong survival.

Metformin Effects on Metabolic Coupling and Tumor Growth in Oral Cavity Squamous Cell Carcinoma Coinjection Xenografts

Objective Many aggressive head and neck cancers contain 2 metabolically coupled tumor compartments: a glycolytic stromal compartment with low caveolin-1 (CAV1) and high monocarboxylate transporter 4 (MCT4) expression and a highly proliferative carcinoma cell compartment with high MCT1. Metabolites are shuttled by MCTs from stroma to carcinoma to fuel tumor growth. We studied the effect of carcinoma-fibroblast coinjection and metformin administration on a mouse model of head and neck squamous cell carcinoma. Study Design Xenograft head and neck squamous cell carcinoma model. Setting Basic science laboratory. Subjects and Methods Oral cavity carcinoma cells were injected alone or as coinjection with human fibroblasts into nude mice to generate xenograft tumors. Tumors were excised and stained with immunohistochemistry for markers of metabolic coupling and apoptosis, including MCT1, MCT4, CAV1, and TUNEL assay (terminal deoxynucleotidyl transferase nick end labeling). Strength of staining was assessed by a pathologist or computer-assisted pathology software. Metformin was administered orally to mice to test effects on immunohistochemical markers in xenografts. Results Coinjection tumors were 2.8-fold larger ( P = .048) and had 1.4-fold stronger MCT1 staining ( P = .016) than tumors from homotypic carcinoma cell injection. Metformin decreased the size of coinjection xenograft tumors by 45% ( P = .025). Metformin reduced MCT1 staining by 28% ( P = .05) and increased carcinoma cell apoptosis 1.8-fold as marked by TUNEL assay ( P = .005). Metformin did not have a significant effect on tumor size when CAV1 knockdown fibroblasts were used in coinjection. Conclusion Coinjection with fibroblasts increases tumor growth and metabolic coupling in oral cavity cancer xenografts. Fibroblast CAV1 expression is required for metformin to disrupt metabolic coupling and decrease xenograft size.

Metformin sensitizes lung cancer cells to treatment by the tyrosine kinase inhibitor erlotinib

Lung cancer is one of the deadliest malignant tumors with limited treatment options. Although targeted therapy, using tyrosine-kinase inhibitors such as erlotinib (Erlo), has shown therapeutic benefit, only 15 % patients with mutated epidermal growth factor receptor (EGFR) in lung cancer cells are sensitive. Therefore, additional therapeutic strategy should be developed. In this study, we found that metformin (Met), which is widely used for the treatment of type 2 diabetes (T2D), sensitized lung cancer cells bearing wild-type EGFR to Erlo treatment by enriching cancer cells expressing higher levels of EGFR with persistent phosphorylation. As a consequence, combination of Met and Erlo more efficiently inhibited the growth of lung cancer cells both in vitro and in mice with xenografted tumors. Our results suggest a novel approach to treating lung cancer cases which are originally resistant to Erlo.

Metformin in Lung Cancer: Review of in Vitro and in Vivo Animal Studies

Cancer cells display enhanced growth rates and a resistance to apoptosis. The ability of cancer cells to evade homeostasis and proliferate uncontrollably while avoiding programmed cell death/apoptosis is acquired through mutations to key signaling molecules, which regulate pathways involved in cell proliferation and survival and these mutations allow them to develop resistance to many chemotherapeutic agents, highlighting the need for development of new potent anti-cancer agents. Metformin has long been used as a treatment for type 2 diabetes and has recently attracted attention as a potential agent to be used in the treatment of cancer. The present review summarizes the existing in vitro and in vivo animal studies focusing on the anti-lung cancer effects of metformin and its effects on key proliferative and anti-apoptotic signaling pathways.

Caveolin-1: An Oxidative Stress-Related Target for Cancer Prevention

Aberrant oxidative metabolism is one of the hallmarks of cancer. Reactive species overproduction could promote carcinogenesis via inducing genetic mutations and activating oncogenic pathways, and thus, antioxidant therapy was considered as an important strategy for cancer prevention and treatment. Caveolin-1 (Cav-1), a constituent protein of caveolae, has been shown to mediate tumorigenesis and progression through oxidative stress modulation recently. Reactive species could modulate the expression, degradation, posttranslational modifications, and membrane trafficking of Cav-1, while Cav-1-targeted treatments could scavenge the reactive species. More importantly, emerging evidences have indicated that multiple antioxidants could exert antitumor activities in cancer cells and protective activities in normal cells by modulating the Cav-1 pathway. Altogether, these findings indicate that Cav-1 may be a promising oxidative stress-related target for cancer antioxidant prevention. Elucidating the underlying interaction mechanisms between oxidative stress and Cav-1 is helpful for enhancing the preventive effects of antioxidants on cancer, for improving clinical outcomes of antioxidant-related therapeutics in cancer patients, and for developing Cav-1 targeted drugs. Herein, we summarize the available evidence of the roles of Cav-1 and oxidative stress in tumorigenesis and development and shed novel light on designing strategies for cancer prevention or treatment by utilizing the interaction mode between Cav-1 and oxidative stress.

Targeting metabolism and AMP-activated kinase with metformin to sensitize non-small cell lung cancer (NSCLC) to cytotoxic therapy: translational biology and rationale for current clinical trials

Lung cancer is the most fatal malignancy worldwide, in part, due to high resistance to cytotoxic therapy. There is need for effective chemo-radio-sensitizers in lung cancer. In recent years, we began to understand the modulation of metabolism in cancer and its importance in tumor progression and survival after cytotoxic therapy. The activity of biosynthetic pathways, driven by the Growth Factor Receptor/Ras/PI3k/Akt/mTOR pathway, is balanced by the energy stress sensor pathway of LKB1/AMPK/p53. AMPK responds both to metabolic and genotoxic stress. Metformin, a well-tolerated anti-diabetic agent, which blocks mitochondria oxidative phosphorylation complex I, became the poster child agent to elicit AMPK activity and tumor suppression. Metformin sensitizes NSCLC models to chemotherapy and radiation. Here, we discuss the rationale for targeting metabolism, the evidence supporting metformin as an anti-tumor agent and adjunct to cytotoxic therapy in NSCLC and we review retrospective evidence and on-going clinical trials addressing this concept.

Metformin targets multiple signaling pathways in cancer

Metformin, an inexpensive and well-tolerated oral agent commonly used in the first-line treatment of type 2 diabetes, has become the focus of intense research as a candidate anticancer agent. Here, we discuss the potential of metformin in cancer therapeutics, particularly its functions in multiple signaling pathways, including AMP-activated protein kinase, mammalian target of rapamycin, insulin-like growth factor, c-Jun N-terminal kinase/mitogen-activated protein kinase (p38 MAPK), human epidermal growth factor receptor-2, and nuclear factor kappaB pathways. In addition, cutting-edge targeting of cancer stem cells by metformin is summarized.

Caveolin-1 in the regulation of cell metabolism: a cancer perspective

Caveolin-1 (CAV1) is an oncogenic membrane protein associated with endocytosis, extracellular matrix organisation, cholesterol distribution, cell migration and signaling. Recent studies reveal that CAV1 is involved in metabolic alterations – a critical strategy adopted by cancer cells to their survival advantage. Consequently, research findings suggest that CAV1, which is altered in several cancer types, influences tumour development or progression by controlling metabolism. Understanding the molecular interplay between CAV1 and metabolism could help uncover druggable metabolic targets or pathways of clinical relevance in cancer therapy. Here we review from a cancer perspective, the findings that CAV1 modulates cell metabolism with a focus on glycolysis, mitochondrial bioenergetics, glutaminolysis, fatty acid metabolism, and autophagy.

Caveolin-1, a stress-related oncotarget, in drug resistance

Caveolin-1 (Cav-1) is both a tumor suppressor and an oncoprotein. Cav-1 overexpression was frequently confirmed in advanced cancer stages and positively associated with ABC transporters, cancer stem cell populations, aerobic glycolysis activity and autophagy. Cav-1 was tied to various stresses including radiotherapy, fluid shear and oxidative stresses and ultraviolet exposure, and interacted with stress signals such as AMP-activated protein kinase. Finally, a Cav-1 fluctuation model during cancer development is provided and Cav-1 is suggested to be a stress signal and cytoprotective. Loss of Cav-1 may increase susceptibility to oncogenic events. However, research to explore the underlying molecular network between Cav-1 and stress signals is warranted.

Metformin as a Tool to Target Aging

Aging has been targeted by genetic and dietary manipulation and by drugs in order to increase lifespan and health span in numerous models. Metformin, which has demonstrated protective effects against several age-related diseases in humans, will be tested in the TAME (Targeting Aging with Metformin) trial, as the initial step in the development of increasingly effective next-generation drugs.

Molecular targets of metformin antitumor action

Epidemiological studies have shown that metformin, a first line therapeutic agent for diabetes mellitus, reduced the risk of developing various malignancies. Several preclinical studies established some possible mechanisms of its anticancer effects. The primary effect of metformin action is a decrease in cell energy status, which activates AMP-activated kinase (AMPK), a cellular metabolic sensor. This event is followed by a decrease in serum concentrations of insulin and insulin growth factor I (IGF-I), the potent mitogens for cancer cells. In addition to the indirect mode of action, metformin may exhibit direct inhibitory effect on cancer cells by targeting mammalian target of rapamycin (mTOR) signaling and anabolic processes. This review gathers information on mechanisms of metformin antitumor activity, with special attention given to the impact of this antidiabetic drug on insulin/PI3K/mTOR and AMPK signaling. Furthermore, the factors required for this novel activity of metformin are discussed.

Translating the Science of Aging into Therapeutic Interventions

Life and health span have been extended in experimental animals using drugs that are potentially translatable into humans. Considerable effort is needed beyond the usual steps in drug development to devise the models, and realistic preclinical and clinical trial strategies are required to advance these agents into clinical application. It will be important to focus on subjects who already have symptoms or are at imminent risk of developing disorders related to fundamental aging processes, to use short-term, clinically relevant outcomes, as opposed to long-term outcomes, such as health span or life span, and to validate endpoint measures so they are acceptable to regulatory agencies. Funding is a roadblock, as is shortage of investigators with combined expertise in the basic biology of aging, clinical geriatrics, and investigational new drug clinical trials. Strategies for developing a path from the bench to the bedside are reviewed for interventions that target fundamental aging mechanisms.

Dissecting the Mechanisms Underlying Unusually Successful Human Health Span and Life Span

Humans age at different rates and families with exceptional survival provide the opportunity to understand why some people age slower than others. Unique features exhibited by centenarians include a family history of longevity, compression of morbidity with resultant extension of health span, and biomarkers such as low-circulating insulin-like growth factor 1 (IGF-1) and elevated high-density lipoprotein (HDL) cholesterol levels. Given the rarity of the centenarian phenotype, it has not been surprising that the use of discovery methods that relied on common population single nucleotide polymorphisms (SNPs) to unlock the genetic determinants of exceptional longevity have not yielded significant results. Conversely, gene sequencing has resulted in discoveries of functional gene variants that support several of the centenarian phenotypes. These discoveries have led to the strategic developments of drugs that may delay aging and prolong health span.

Association between metformin therapy and incidence, recurrence and mortality of prostate cancer: evidence from a meta-analysis

OBJECTIVE

Previous studies suggested that metformin is associated with decreased risk of cancer; however, results specifically addressing the potential association with prostate cancer were limited and contradictory. This study considers the association between metformin and the incidence, mortality and recurrence of prostate cancer by performing a meta-analysis of observational studies.

METHODS

Literatures published before January 2014 were searched by using databases of PubMed and Embase. Pooled relative risks (RRs) were determined using a random effects model to evaluate the strength of association between metformin therapy and risk of prostate cancer.

RESULTS

Thirteen studies involving a total of 334 532 participants were included in this meta-analysis. Compared with the control group, metformin therapy was associated with significantly decreased incidence of prostate cancer [RR = 0.88, 95% confidence interval (CI) [0.78, 0.99], p = 0.03, I(2)  = 74.7%]. However, metformin therapy was not associated with decreased all-cause mortality (RR = 1.07, 95% CI [0.86, 1.32], p = 0.55, I(2)  = 58.2%) or decreased recurrence of prostate cancer (RR = 0.90, 95% CI [0.75, 1.09], p = 0.27, I(2)  = 0.0%). No publication bias was detected (pBegg  = 0.55, pEgger  = 0.46).

CONCLUSIONS

The present study suggested that metformin therapy may decrease the incidence of prostate cancer but that there was no association between the treatment and all-cause mortality or recurrence. It is recommended that this finding should be considered carefully and confirmed with further studies.

Synergistic effects of metformin in combination with EGFR-TKI in the treatment of patients with advanced non-small cell lung cancer and type 2 diabetes

BACKGROUND

Acquired resistance has become the bottleneck affecting the efficacy of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) treatment. Studies have shown that the antidiabetic drug metformin could effectively increase the sensitivity of TKI-resistant lung cancer cells to EGFR-TKI. This study aimed to evaluate the effect of metformin in combination with EGFR-TKI on the prognosis of non-small cell lung cancer (NSCLC) patients with diabetes mellitus type 2 (DM2).

METHODS

Data of NSCLC patients with DM2 who received treatment in six hospitals in China between January 2006 and January 2014 were reviewed retrospectively. They were divided into two groups: Group A, where the patients (n = 44) received EGFR-TKI plus metformin; and Group B, where the patients (n = 46) received EGFR-TKI plus hypoglycemic agents other than metformin. Prognostic differences between the two groups were assessed.

RESULTS

The median progression-free survival (PFS) and median overall survival (OS) in Group A were significantly longer than those in Group B (19.0 months vs. 8.0 months, P = .005; 32.0 months vs. 23.0 months, P = .002). The objective response rate (ORR) and disease control rate (DCR) in Group A were significantly higher than those in Group B (70.5% vs. 45.7%, P = .017; 97.7% vs. 80.4%, P = .009). Secondary data analysis showed that metformin use significantly prolonged the median PFS in subgroups using either first-line EGFR-TKI or second-line EGFR-TKI.

CONCLUSIONS

Metformin and EGFR-TKI have a synergistic effect in the treatment of DM2 NSCLC patients harboring EGFR-activating mutations. Metformin use is associated with improved survival and delayed onset of acquired resistance to EGFR-TKI.

Differentiation of high-risk stage I and II colon tumors based on evaluation of CAV1 gene expression

BACKGROUND

Several molecular markers are currently being investigated for their prognostic or predictive value in colorectal cancer. One of the genes proposed, as a potential molecular marker in CRC is CAV1.

METHODS

The level of CAV1 expression was investigated in low-stage (I and II TNM) colon cancers using Real-Time PCR and immunohistochemistry.

RESULTS

The level of CAV1 expression increased in tumors characterized by greater depths of invasiveness. The CAV1 expression level detected in tumors with a depth of invasion at stage T4 was significantly higher compared to that in T2 (P = 0.01) and T3 (P = 0.003) lesions. The length of a patient's survival depended on CAV1 expression level; the 10-year survival rate for patients with elevated expression of CAV1 was ∼59% compared with 91% for patients with reduced or unchanged expression of CAV1 (P = 0.007). The overall survival rate of patients with T3 + T4 lesions was significantly lower (P = 0.006) for patients with tumor displaying elevated CAV1 expression compared with patients with reduced or unchanged CAV1 expression.

CONCLUSIONS

Evaluation of CAV1 expression offers valuable prognostic information for patients with colorectal cancer, and could be used to select patients with stage I or II disease, who are at increased risk of unfavorable outcomes.

Identification of AMP-activated protein kinase targets by a consensus sequence search of the proteome

Background

AMP-activated protein kinase (AMPK) is a heterotrimeric serine/threonine protein kinase that is activated by cellular perturbations associated with ATP depletion or stress. While AMPK modulates the activity of a variety of targets containing a specific phosphorylation consensus sequence, the number of AMPK targets and their influence over cellular processes is currently thought to be limited.

Results

We queried the human and the mouse proteomes for proteins containing AMPK phosphorylation consensus sequences. Integration of this database into Gaggle software facilitated the construction of probable AMPK-regulated networks based on known and predicted molecular associations. In vitro kinase assays were conducted for preliminary validation of 12 novel AMPK targets across a variety of cellular functional categories, including transcription, translation, cell migration, protein transport, and energy homeostasis. Following initial validation, pathways that include NAD synthetase 1 (NADSYN1) and protein kinase B (AKT2) were hypothesized and experimentally tested to provide a mechanistic basis for AMPK regulation of cell migration and maintenance of cellular NAD⁺ concentrations during catabolic processes.

Conclusions

This study delineates an approach that encompasses both in silico procedures and in vitro experiments to produce testable hypotheses for AMPK regulation of cellular processes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-015-0156-0) contains supplementary material, which is available to authorized users.

IGF1 regulates PKM2 function through Akt phosphorylation

Pyruvate kinase M2 (PKM2) acts at the crossroad of growth and metabolism pathways in cells. PKM2 regulation by growth factors can redirect glycolytic intermediates into key biosynthetic pathway. Here we show that IGF1 can regulate glycolysis rate, stimulate PKM2 Ser/Thr phosphorylation and decrease cellular pyruvate kinase activity. Upon IGF1 treatment we found an increase of the dimeric form of PKM2 and the enrichment of PKM2 in the nucleus. This effect was associated to a reduction of pyruvate kinase enzymatic activity and was reversed using metformin, which decreases Akt phosphorylation. IGF1 induced an increased nuclear localization of PKM2 and STAT3, which correlated with an increased HIF1α, HK2, and GLUT1 expression and glucose entrapment. Metformin inhibited HK2, GLUT1, HIF-1α expression and glucose consumption. These findings suggest a role of IGFIR/Akt axis in regulating glycolysis by Ser/Thr PKM2 phosphorylation in cancer cells.

Loss of stromal caveolin-1 expression: a novel tumor microenvironment biomarker that can predict poor clinical outcomes for pancreatic cancer

AIMS

Cancer development and progression is not only associated with the tumor cell proliferation but also depends on the interaction between tumor cells and the stromal microenvironment. A new understanding of the role of the tumor microenvironment suggests that the loss of stromal caveolin-1 (Cav-1) as a key regulator may become a potential therapy target. This study aims to elucidate whether stromal Cav-1 expression in pancreatic cancer can be a strong prognosis biomarker.

METHODS

Tissue samples from 45 pancreatic cancer patients were studied. Parenchyma and stroma were separated and purified using laser capture microdissection. Stromal Cav-1 expression was measured from pancreatic cancer, paraneoplastic, and normal tissue using immunohistochemistry. We analyzed the correlation of stromal Cav-1 expression with clinicopathologic features and prognostic indicators, such as tumor marker HER-2/neu gene.

RESULTS

Specimens from six patients (13.3%) showed high levels of stromal Cav-1 staining, those from eight patients (17.8%) showed a lower, intermediate level of staining, whereas those from 31 patients (68.9%) showed an absence of staining. Cav-1 expression in cancer-associated fibroblasts was lower than that in paracancer-associated and in normal fibroblasts. Stromal Cav-1 loss was associated with TNM stage (P = 0.018), lymph node metastasis (P = 0.014), distant metastasis (P = 0.027), and HER-2/neu amplification (P = 0.007). The relationships of age, sex, histological grade, and tumor size with stromal Cav-1 expression were not significant (P>0.05). A negative correlation was found between circulating tumor cells and stromal Cav-1 expression (P<0.05).

CONCLUSION

The loss of stromal Cav-1 in pancreatic cancer was an independent prognostic indicator, thus suggesting that stromal Cav-1 may be an effective therapeutic target for patients with pancreatic cancer.

Conventional hypoglycaemic agents and the risk of lung cancer in patients with diabetes: a meta-analysis

BACKGROUND

Accumulating evidence suggests that hypoglycaemic agents influence lung cancer risk in patients with diabetes. It remains to be fully elucidated whether conventional hypoglycaemic agents (metformin, sulfonylureas, thiazolidinediones [TZDs] or insulin) affect lung cancer incidence in patients with diabetes.

METHODS

We performed a meta-analysis using EMBASE, MEDLINE and Web of Science to search randomised controlled trials (RCTs), cohort studies, and case-control studies published up to October 2013 that assessed the effects of metformin, sulfonylurea, TZDs or insulin on lung cancer risk in subjects with diabetes. Fixed and random effects meta-analysis models were used, and the effect size was expressed as a summary odds ratio (OR) with 95% confidence intervals (CI). The Grades of Research, Assessment, Development and Evaluation (GRADE) approach was applied to define the quality of the evidence.

RESULTS

Analysis of 15 studies (11 cohort studies, 2 case-control studies, and 2 RCTs) showed that metformin use was associated with a 15% reduction in risk of lung cancer (OR 0.85, 95% CI 0.77 to 0.92), but this finding was not supported by sub-analysis of smoking-adjusted studies (OR 0.84, 95% CI 0.61 to 1.06). Moreover, sulfonylurea or TZDs use was not associated with increased or decreased lung cancer risk, respectively (OR 1.10, 95% CI 0.93 to 1.26), (OR 0.86, 95% CI 0.70 to 1.02). Higher lung cancer risk was related to insulin (OR 1.23, 95% CI 1.10 to 1.35). However, all data from RCTs failed to demonstrate a statistically significant effect.

CONCLUSIONS

This analysis demonstrated that metformin use may reduce lung cancer risk in patients with diabetes but not in a smoking-adjusted subgroup and that insulin use may be associated with an increased lung cancer risk in subjects with diabetes.

Metformin sensitizes EGFR-TKI-resistant human lung cancer cells in vitro and in vivo through inhibition of IL-6 signaling and EMT reversal

PURPOSE

The EGF receptor tyrosine kinase inhibitors (EGFR-TKI) have become a standard therapy in patients with EGFR-activating mutations. Unfortunately, acquired resistance eventually limits the clinical effects and application of EGFR-TKIs. Studies have shown that suppression of epithelial-mesenchymal transition (EMT) and the interleukin (IL)-6/STAT3 pathway may abrogate this acquired mechanism of drug resistance of TKIs. This study aims to investigate the effect of metformin on sensitizing EGFR-TKI-resistant human lung cancer cells in vitro and in vivo through inhibition of IL-6 signaling and EMT reversal.

EXPERIMENTAL DESIGN

The effect of metformin on reversing TKI resistance was examined in vitro and in vivo using MTT, BrdUrd incorporation assay, invasion assay, flow cytometry analysis, immunostaining, Western blot analysis, and xenograft implantation.

RESULTS

In this study, metformin, a widely used antidiabetic agent, effectively increased the sensitivity of TKI-resistant lung cancer cells to erlotinib or gefitinib. Metformin reversed EMT and decreased IL-6 signaling activation in TKI-resistant cells, while adding IL-6 to those cells bypassed the anti-TKI-resistance effect of metformin. Furthermore, overexpression or addition of IL-6 to TKI-sensitive cells induced TKI resistance, which could be overcome by metformin. Finally, metformin-based combinatorial therapy effectively blocked tumor growth in xenografts with TKI-resistant cancer cells, which was associated with decreased IL-6 secretion and expression, EMT reversal, and decreased IL-6-signaling activation in vivo.

CONCLUSION

Metformin, generally considered nontoxic and remarkably inexpensive, might be used in combination with TKIs in patients with non-small cell lung cancer, harboring EGFR mutations to overcome TKI resistance and prolong survival.