Metformin synergistically enhances antiproliferative effects of cisplatin and etoposide in NCI-H460 human lung cancer cells

Addition of metformin for non-small cell lung cancer patients receiving antineoplastic agents

Background and purpose: Previous studies have found that metformin can inhibit tumor growth and improve outcomes for cancer patients. However, the association between the addition of metformin to the treatment regimen and survival in non-small cell lung cancer (NSCLC) patients receiving antineoplastic agents such as chemotherapy drugs, epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), and immune checkpoint inhibitors (ICIs) remains unclear. This study aimed to evaluate the effect of metformin in NSCLC patients who received the aforementioned antineoplastic therapies.

Methods: Several electronic databases were searched for relevant studies published by 10 September 2022. The primary and secondary outcomes were overall survival (OS) and progression-free survival (PFS); eligible studies were those comparing patients with and without the addition of metformin. Hazard ratios (HRs) and 95% confidence intervals (CIs) were combined, with all statistical analyses performed using STATA 15.0.

Results: A total of 19 studies involving 6,419 participants were included, of which six were randomized controlled trials. The overall pooled results indicate that the addition of metformin improved OS (HR = 0.84, 95% CI: 0.71–0.98, p = 0.029) and PFS (HR = 0.85, 95% CI: 0.74–0.99, p = 0.039). However, subgroup analysis based on treatment type and comorbidity of diabetes mellitus demonstrated that improvements in OS and PFS were observed only in diabetic and EGFR-TKI-treated patients (OS: HR = 0.64, 95% CI: 0.45–0.90, p = 0.011; PFS: HR = 0.59, 95% CI: 0.34–1.03, p = 0.061).

Conclusion: Overall, this meta-analysis found that metformin use could improve outcomes for diabetic patients receiving EGFR-TKIs. However, no significant association between the addition of metformin and the survival of non-diabetic NSCLC patients receiving chemotherapy or ICI therapy was identified based on the current evidence.

Metformin: A promising drug for human cancers

Small-molecule chemical drugs are of great significance for tumor-targeted and individualized therapies. However, the development of new small-molecule drugs, from basic experimental research and clinical trials to final application in clinical practice, is a long process that has a high cost. It takes at least 5 years for most drugs to be developed in the laboratory to prove their effectiveness and safety. Compared with the development of new drugs, repurposing traditional non-tumor drugs can be a shortcut. Metformin is a good model for a new use of an old drug. In recent years, the antitumor efficacy of metformin has attracted much attention. Epidemiological data and in vivo, and in vitro experiments have shown that metformin can reduce the incidence of cancer in patients with diabetes and has a strong antagonistic effect on metabolism-related tumors. Recent studies have shown that metformin can induce autophagy in esophageal cancer cells, mainly by inhibiting inflammatory signaling pathways. In recent years, studies have shown that the antitumor functions and mechanisms of metformin are multifaceted. The present study aims to review the application of metformin in tumor prevention and treatment.

Will We Unlock the Benefit of Metformin for Patients with Lung Cancer? Lessons from Current Evidence and New Hypotheses

Metformin has been under basic and clinical study as an oncological repurposing pharmacological agent for several years, stemming from observational studies which consistently evidenced that subjects who were treated with metformin had a reduced risk for development of cancer throughout their lives, as well as improved survival outcomes when diagnosed with neoplastic diseases. As a result, several basic science studies have attempted to dissect the relationship between metformin’s metabolic mechanism of action and antineoplastic cellular signaling pathways. Evidence in this regard was compelling enough that a myriad of randomized clinical trials was planned and conducted in order to establish the effect of metformin treatment for patients with diverse neoplasms, including lung cancer. As with most novel antineoplastic agents, early results from these studies have been mostly discouraging, though a recent analysis that incorporated body mass index may provide significant information regarding which patient subgroups might derive the most benefit from the addition of metformin to their anticancer treatment. Much in line with the current pipeline for anticancer agents, it appears that the benefit of metformin may be circumscribed to a specific patient subgroup. If so, addition of metformin to antineoplastic agents could prove one of the most cost-effective interventions proposed in the context of precision oncology. Currently published reviews mostly rely on a widely questioned mechanism of action by metformin, which fails to consider the differential effects of the drug in lean vs. obese subjects. In this review, we analyze the pre-clinical and clinical information available to date regarding the use of metformin in various subtypes of lung cancer and, further, we present evidence as to the differential metabolic effects of metformin in lean and obese subjects where, paradoxically, the obese subjects have reported more benefit with the addition of metformin treatment. The novel mechanisms of action described for this biguanide may explain the different results observed in clinical trials published in the last decade. Lastly, we present novel hypothesis regarding potential biomarkers to identify who might reap benefit from this intervention, including the role of prolyl hydroxylase domain 3 (PHD3) expression to modify metabolic phenotypes in malignant diseases.

Combined regimens of cisplatin and metformin in cancer therapy: A systematic review and meta-analysis

INTRODUCTION

Cancer cell resistance to chemotherapy agents is a challenging issue in treating patients with cancer. Findings suggest that a combination of drugs may have synergistic or additive effects. in the present study, we systematically reviewed the combined regimens of metformin with cisplatin in various treating cancers.

METHODS

A comprehensive systematic search was performed in PubMed, Scopus, Embase, and other relevant databases with the following keyword "metformin", "cisplatin", "combination", "using all their equivalents and similar terms. Pooled odds ratio (OR) and 95% confidence intervals of cell viability and tumor volume as primary outcomes were calculated using Der-Simonian and Laird method while random effects meta-analysis was used, taking into account clinical and statistical heterogeneity.

RESULTS

Overall, 44 studies were retrieved, Findings of the present meta-analysis showed that combined regimens of metformin plus cisplatin was significantly associated with decreased odds of tumor volume and cell viability for all cancers compared with cisplatin alone (pooled OR: 0.40; 95% CI: 0.27, 0.58) and (pooled OR: 0.49; 95% CI: 0.42, 0.58) respectively. The result was same for cell viability in lung cancer (pooled OR: 0.59; 95% CI: 0.49, 0.70). The tumor size reduction and the response rate were evident in the animal xenografts model.

CONCLUSION

Findings indicated that combining metformin with cisplatin is a practical therapeutic approach to increase treatment efficacy in the case of cell viability and tumor volume and minimize side effects. A combination of metformin with cisplatin could enhance treatment efficacy through synergistic inhibitory effects on the growth of cancer cells.

The effect of metformin on viability and mitochondrial status of tumor and non-tumor cell line

Introduction: Metformin is a drug of choice in the therapy of type II Diabetes mellitus. There is a growing evidence of metformin's antitumor activity, but the suggested mechanisms of such activity are still not fully elucidated. Aim: To investigate the effect of therapeutic doses of metformin on viability and mitochondrial status of human non-small cell lung carcinoma (NCI-H460) and human immortalized lung fibroblasts (MRC-5) cell lines. Material and methods: Acid phosphatase and Crystal Violet assays were used for the determination of NCI-H460 and MRC-5 cell viability after the treatment with metformin (10-60 µM) for 1-7 days. Mitochondrial membrane potential, production of reactive oxygen species and superoxide anion, as well as mitochondrial mass were measured using flow cytometry after the treatment of the cells for 3, 24 and 120 h, followed by staining with appropriate fluorochromes: JC-1, DHR, DHE and Mitotracker Red. Results: Metformin did not change the viability of both NCI-H460 and MRC-5 cells in all investigated time-points and all used concentrations. Depolarization of mitochondrial membrane was observed 3 h post-treatment in MRC-5 cells. Prolonged treatment (120 h) increased superoxide anion production and mitochondrial mass in NCI-H460 cells. No significant changes in production of reactive oxygen species were observed in both cells lines after short or extended exposure to metformin. Conclusion: : Therapeutic concentrations of metformin do not influence the viability of NCI-H460 and MRC-5 cells, but induce mitochondrial depolarization after short-term exposure in lung fibroblasts and increase production of superoxide anion and mitochondrial mass in lung carcinoma cells after prolonged treatment.

Enhanced Antiproliferation Potency of Electrical Pulse-Mediated Metformin and Cisplatin Combination Therapy on MDA-MB-231 Cells

We investigated the combined potency of metformin and cisplatin on the MDA-MB-231, triple-negative breast cancer (TNBC) cells with the application of electrical pulses. There are no targeted therapies for this subset of breast cancer because of the absence of specific biomarkers. Cytotoxic chemotherapy is the mainstream mode of treatment for TNBC, and cisplatin is the most commonly used chemotherapeutic drug. While there is a good response initially, TNBC cells develop drug resistance eventually. Thus, there is a need for alternate therapies. Toward this, we studied the antiproliferation characteristics of electrical pulse-mediated combination therapy using metformin, the commonly used Type-2 diabetes drug, along with cisplatin. We used metformin, as it has various anticancer properties caused by repressing energy pathways in a cancer cell. Application of 8 pulses of 1000 V/cm, 100 µs, at 1 Hz frequency, enhanced the drug uptake leading to cell viability as low as 25.86% at 30 µM cisplatin and 5 mM metformin in a 24 h study. Also, the same studies were conducted on MCF10A, a non-cancerous human epithelial cell. It aided in comparing the result for both MDA-MB-231 and MCF10A cell lines while establishing a better understanding of the experimental outcomes. Overall, the various experimental results from colony-forming assay, reactive oxidative analysis, and the intracellular glucose metabolic assay indicate the possibility of the electrical pulses-based cisplatin and metformin drug combination as a potential alternative to TNBC treatment.

Metformin Adjunct With Antineoplastic Agents for the Treatment of Lung Cancer: A Meta-Analysis of Randomized Controlled Trials and Observational Cohort Studies

Objective: Resistance to anticancer agents ensures a poor prognosis in patients with lung cancer. Metformin could enhance the anticancer effects of standard antineoplastic agents [traditional chemotherapy drugs, epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), or immune checkpoint inhibitors (ICIs)]; however, it is unclear whether metformin can be combined with antineoplastic agents in the treatment of lung cancer. To explore the efficacy of combinational strategies, we performed a systematic review and meta-analysis for diabetic and non-diabetic patients with lung cancer.

Method: An electronic literature search was performed to obtain relevant randomized controlled trials (RCTs) and observational cohort studies. Hazard ratios (HR) with 95% confidence intervals (CI) of overall survival (OS) and progression-free survival (PFS) outcomes were extracted. Subgroup analysis by antineoplastic agents, study type, histology and clinical stage were investigated.

Results: 14 studies (three RCTs and eleven observational cohort studies) consisting 3,856 patients were included in the meta-analysis. Compared to standard antineoplastic agents alone (traditional chemotherapy drugs, EGFR-TKIs or ICIs), the antineoplastic agents combined with metformin significantly improved OS (HR 0.73, 95% CI 0.66–0.81, p < 0.00001) and PFS (HR 0.72, 95% CI 0.59–0.88, p = 0.001); a similar association was found in observational evidence. Limited data from RCTs showed no differences in OS or PFS.

Conclusion: Metformin plus antineoplastic agents may improve survival outcomes of patients with lung cancer. Further investigation is needed.

Metformin impairs cisplatin resistance effects in A549 lung cancer cells through mTOR signaling and other metabolic pathways

Lung cancer is the leading cause of cancer‑associated death worldwide and exhibits intrinsic and acquired therapeutic resistance to cisplatin (CIS). The present study investigated the role of mTOR signaling and other signaling pathways after metformin (MET) treatment in control and cisplatin‑resistant A549 cells, mapping pathways and possible targets involved in CIS sensitivity. MTT, flow cytometry, clonogenic assay, western blotting, proteomic analysis using the Stable Isotope Labeling by Amino acids in Cell culture (SILAC) approach and reverse transcription‑quantitative PCR were performed. The results revealed that CIS treatment induced mTOR signaling pathway overactivation, and the mTOR status was restored by MET. MET and the mTOR inhibitor rapamycin (RAPA) decreased the viability in control and resistant cells, and decreased the cell size increase induced by CIS. In control cells, MET and RAPA decreased colony formation after 72 h and decreased IC₅₀ values, potentiating the effects of CIS. Proteomics analysis revealed important pathways regulated by MET, including transcription, RNA processing and IL‑12‑mediated signaling. In CIS‑resistant cells, MET regulated the apoptotic process, oxidative stress and G₂/M transition. Annexin 4 (ANXA4) and superoxide dismutase 2 (SOD2), involved in apoptosis and oxidative stress, respectively, were chosen to validate the SILAC analysis and may represent potential therapeutic targets for lung cancer treatment. In conclusion, the chemosensitizing and antiproliferative effects of MET were associated with mTOR signaling and with potential novel targets, such as ANXA4 and SOD2, in human lung cancer cells.

The Chemosensitizing Role of Metformin in Anti-Cancer Therapy

Chemoresistance, which leads to the failure of chemotherapy and further tumor recurrence, presents the largest hurdle for the success of anti-cancer therapy. In recent years, metformin, a widely used first-line antidiabetic drug, has attracted increasing attention for its anti-cancer effects. A growing body of evidence indicates that metformin can sensitize tumor responses to different chemotherapeutic drugs, such as hormone modulating drugs, anti-metabolite drugs, antibiotics, and DNA-damaging drugs via selective targeting of Cancer Stem Cells (CSCs), improving the hypoxic microenvironment, and by suppressing tumor metastasis and inflammation. In addition, metformin may regulate metabolic programming, induce apoptosis, reverse Epithelial to Mesenchymal Transition (EMT), and Multidrug Resistance (MDR). In this review, we summarize the chemosensitization effects of metformin and focus primarily on its molecular mechanisms in enhancing the sensitivity of multiple chemotherapeutic drugs, through targeting of mTOR, ERK/P70S6K, NF-κB/HIF-1 α, and Mitogen- Activated Protein Kinase (MAPK) signaling pathways, as well as by down-regulating the expression of CSC genes and Pyruvate Kinase isoenzyme M2 (PKM2). Through a comprehensive understanding of the molecular mechanisms of chemosensitization provided in this review, the rationale for the use of metformin in clinical combination medications can be more systematically and thoroughly explored for wider adoption against numerous cancer types.>.

Dual polymeric prodrug co-assembled nanoparticles with precise ratiometric co-delivery of cisplatin and metformin for lung cancer chemoimmunotherapy

The combination therapy of cisplatin (CDDP) and metformin (MET) is a clinical strategy to enhance therapeutic outcomes in lung cancer. However, the efficacy of this combination is limited due to the asynchronous pharmacokinetic behavior of CDDP and MET, used as free drugs. Therefore, in this work, hyaluronic acid-cisplatin/polystyrene-polymetformin (HA-CDDP/PMet) dual-prodrug co-assembled nanoparticles were developed, with precise ratiometric co-delivery of CDDP and MET for chemo-immunotherapy against lung cancer. The HA-CDDP/PMet NPs showed a spherical morphology with an average particle size of 166.5 nm and a zeta potential of -17.4 mV at an HA-CDDP and PMet mass ratio of 1/1. The content of CDDP and MET in HA-CDDP/PMet NPs was 3.7% and 15.2%, respectively. In vitro antitumor effects of CDDP and MET resulted in an improved synergistic action on proliferation inhibition and apoptosis induction on Lewis lung cancer cells. Moreover, in vivo by co-delivered HA-CDDP/PMet NPs into tumor cells, with an excellent intracellular CDDP and MET cleavage. These nanoparticles exhibited significantly increased tumor accumulation and tumor growth inhibition and prolonged animal overall survival in Lewis lung cancer bearing mice without nephrotoxicity, excess of free drugs and homo-prodrugs. The synergistic effect of MET and CDDP in HA-CDDP/PMet NPs resulted in up-regulation of the cleaved poly(ADP)-ribose polymerase (PARP) protein to induce tumor cell apoptosis, and down-regulation of the excision repair cross-complementation group 1 (ERCC1) protein level to decrease the resistance to CDDP. The synergistic effect of MET and CDDP in HA-CDDP/PMet NPs also resulted in induction of the adenosine monophosphate (AMP)-activated protein kinase-α (AMPK-α) pathway and inhibition of the mammalian target of rapamycin (mTOR), finally exerting a chemotherapeutic effect and modulating a potent immunotherapeutic function with an increase in CD4⁺ and CD8⁺ T cells, a concomitant decrease in regulatory T (Treg) cells, and an increased expression of the cytokines IFN-γ and TNF-α. Therefore, the immunochemotherapy using CDDP and MET mediated by this dual prodrug co-assembled nano-platform might provide a promising treatment strategy against lung cancer.

A Cohort Study of Exposure to Antihyperglycemic Therapy and Survival in Patients with Lung Cancer

We evaluated the effect of antihyperglycemic therapy on the survival of patients with lung cancer (LC). The analysis included patients with LC and concomitant type 2 diabetes. 15,929 patients were classified into five groups: metformin users, insulin users, metformin and insulin users, sulphonylurea users and non-diabetic group. A multivariate analysis showed that exposure to either metformin or to insulin was associated with a lower risk of LC-specific mortality, and this approached statistical significance (HR 0.82, 95% CI 0.72–92 for metformin and HR 0.65, 95% CI 0.44–95 for insulin). When deaths from all causes were considered, only metformin exposure was associated with a significantly lower risk of death (HR 0.82, 95% CI 0.73–0.92). Users of sulphonylurea were at a higher risk of LC-specific and overall mortality (HRs 1.19, 95% CI 0.99–1.43 and 1.22, 95% CI 1.03–1.45). Our study shows a positive effect of metformin on the survival of patients with LC. Moreover, our results show that exposure to insulin was associated with a lower risk of LC-specific mortality, but not with deaths from all causes. The study results suggested that users of sulphonylurea may be at a higher risk of LC-specific and overall mortality.

Metformin overcomes resistance to cisplatin in triple-negative breast cancer (TNBC) cells by targeting RAD51

Background

Chemotherapy is a standard therapeutic regimen to treat triple-negative breast cancer (TNBC); however, chemotherapy alone does not result in significant improvement and often leads to drug resistance in patients. In contrast, combination therapy has proven to be an effective strategy for TNBC treatment. Whether metformin enhances the anticancer effects of cisplatin and prevents cisplatin resistance in TNBC cells has not been reported.

Methods

Cell viability, wounding healing, and invasion assays were performed on Hs 578T and MDA-MB-231 human TNBC cell lines to demonstrate the anticancer effects of combined cisplatin and metformin treatment compared to treatment with cisplatin alone. Western blotting and immunofluorescence were used to determine the expression of RAD51 and gamma-H2AX. In an in vivo 4T1 murine breast cancer model, a synergistic anticancer effect of metformin and cisplatin was observed.

Results

Cisplatin combined with metformin decreased cell viability and metastatic effect more than cisplatin alone. Metformin suppressed cisplatin-mediated RAD51 upregulation by decreasing RAD51 protein stability and increasing its ubiquitination. In contrast, cisplatin increased RAD51 expression in an ERK-dependent manner. In addition, metformin also increased cisplatin-induced phosphorylation of γ-H2AX. Overexpression of RAD51 blocked the metformin-induced inhibition of cell migration and invasion, while RAD51 knockdown enhanced cisplatin activity. Moreover, the combination of metformin and cisplatin exhibited a synergistic anticancer effect in an orthotopic murine model of 4T1 breast cancer in vivo.

Conclusions

Metformin enhances anticancer effect of cisplatin by downregulating RAD51 expression, which represents a novel therapeutic target in TNBC management.

Metformin for lung cancer prevention and improved survival: a novel approach

Diabetes mellitus has been associated with increased risk for the development of many types of cancer. Metformin, an oral medication and first-line treatment for type 2 diabetes mellitus, has been suggested to reduce cancer risk and mortality in various types of cancer. This study focuses on assessing metformin association with lung cancer as reported in the literature. Recent studies and reviews investigating metformin effects on lung cancer incidence and patient survival are critically and systematically discussed.

Metformin attenuates cisplatin-induced genotoxicity and apoptosis in rat bone marrow cells

Metformin is widely used as an oral hypoglycemic drug in the management of type 2 diabetes mellitus. This study evaluated the possible protective effects of metformin against cisplatin-induced genotoxicity and apoptosis in rat bone marrow cells. Two different doses of metformin (50 and 100 mg/kg b.w.) were administered orally to experimental animals for seven consecutive days. On the seventh day, the rats were exposed to cisplatin (5 mg/kg, i.p.) 1 h after the last oral metformin administration. Rats in the control group were treated orally with 10 ml/kg PBS for 7 consecutive days and a single intraperitoneal injection of saline (0.9%) on the 7th day. The antagonistic effects of metformin against cisplatin were evaluated using micronucleus assay, reactive oxygen species (ROS) level analysis, hematological analysis, and flow cytometry. Treatment with 50 and 100 mg/kg metformin before cisplatin injection produced a significant reduction in the frequencies of micronucleated polychromatic erythrocytes (MnPCEs) and micronucleated normochromatic erythrocytes (MnNCEs) 24 h after cisplatin treatment with a corresponding increase in the PCE/(PCE + NCE) ratio. Moreover, metformin markedly elevated the levels of both red and white blood cells in peripheral blood and decreased the percentage of apoptotic cells and the ROS level in bone marrow cells of rats treated with cisplatin. The data suggest that metformin has potential chemoprotective properties in rat bone marrow after cisplatin treatment, which support its candidature as a potential chemoprotective agent for cancer patients undergoing chemotherapy.

Metformin Use and Lung Cancer Risk in Diabetic Patients: A Systematic Review and Meta-Analysis

Background

Antidiabetic medications (ADMs) can alter the risk of different types of cancer, but the relationship between lung cancer incidence and metformin remains controversial. Our aim was to quantitatively estimate the relationship between incidences of lung cancer and metformin in patients with diabetes in this meta-analysis.

Methods

We performed a search in PubMed, Embase, ISI Web of Science, and Cochrane Library until September 20, 2017. The odds ratio (OR), relative risk (RR) or hazard ratio (HR), and 95% confidence interval (95% CI) were estimated using the random-effect model. The Newcastle-Ottawa Scale (NOS) was used to assess the study quality.

Results

A total of 13 studies (10 cohort studies and 3 case-control studies) were included in the meta-analysis. Compared to nonmetformin users, metformin probably decreased lung cancer incidence in diabetic patients (RR = 0.89; 95% CI, 0.83-0.96; P = 0.002) with significant heterogeneity (Q = 35.47, I² = 66%, P = 0.0004). Subgroup analysis showed that cohort studies (RR = 0.91; 95% CI, 0.85-0.98; P = 0.008), location in Europe (RR = 0.90; 95% CI, 0.86-0.94; P < 0.0001), the control drug of the sulfonylurea group (RR = 0.91; 95% CI, 0.86-0.96; P = 0.001), and adjusting for smoking (RR = 0.86; 95% CI, 0.75-1.00; P = 0.05) may be related to lower lung cancer risk. No significant publication bias was detected using a funnel plot.

Conclusion

Metformin use was related to a lower lung cancer risk in diabetic patients compared to nonusers, but this result was retrieved from observational studies and our findings need more well-designed RCTs to confirm the association.

Metformin enhances the radiosensitizing effect of cisplatin in non-small cell lung cancer cell lines with different cisplatin sensitivities

Cisplatin is an extensively used chemotherapeutic drug for lung cancer, but the development of resistance decreases its effectiveness in the treatments of non-small cell lung cancer (NSCLC). In this study, we examined the effects of metformin, a widely used antidiabetic drug, on cisplatin radiosensitization in NSCLC cell lines. Human NSCLC cell lines, A549 (cisplatin-resistant) and H460 (cisplatin-sensitive), were treated with metformin, cisplatin or a combination of both drugs before ionizing radiation. Cell proliferation, clonogenic assays, western blotting, cisplatin-DNA adduct formation and immunocytochemistry were used to characterize the treatments effects. Metformin increased the radiosensitivity of NSCLC cells. Metformin showed additive and over-additive effects in combination with cisplatin and the radiation response in the clonogenic assay in H460 and A549 cell lines (p = 0.018 for the interaction effect between cisplatin and metformin), respectively. At the molecular level, metformin led to a significant increase in cisplatin-DNA adduct formation compared with cisplatin alone (p < 0.01, ANOVA-F test). This was accompanied by a decreased expression of the excision repair cross-complementation 1 expression (ERCC1), a key enzyme in nucleotide excision repair pathway. Furthermore, compared with each treatment alone metformin in combination with cisplatin yielded the lowest level of radiation-induced Rad51 foci, an essential protein of homologous recombination repair. Ionizing radiation-induced γ-H2AX and 53BP1 foci persisted longer in both cell lines in the presence of metformin. Pharmacological inhibition of AMP-activated protein kinase (AMPK) demonstrated that metformin enhances the radiosensitizing effect of cisplatin through an AMPK-dependent pathway only in H460 but not in A549 cells. Our results suggest that metformin can enhance the effect of combined cisplatin and radiotherapy in NSCLC and can sensitize these cells to radiation that are not sensitized by cisplatin alone.

In Vitro Study of Antitumor Effect of Antimicrobial Peptide Tachyplesin I in Combination with Cisplatin

We studied combined effect of β-hairpin antimicrobial peptide tachyplesin I and cytotoxic agent cisplatin on tumor and normal human cell lines. MTT assay and flow cytometry showed that tachyplesin I selectively sensitized cancer cells to cisplatin in specified concentration ratios. In vitro experiments demonstrated that combined use of tachyplesin I and cisplatin allows decreasing the effective dose of the cytostatic thus reducing nonspecific toxicity.

Survival benefit associated with metformin use in inoperable non-small cell lung cancer patients with diabetes: A population-based retrospective cohort study

Objective

To evaluate the effects of metformin use on the survival of inoperable non-small cell lung cancer (NSCLC) patients with diabetes using the Taiwanese National Health Insurance Research Database.

Research design and methods

In total, 7,620 patients were eligible in this study, among them, 3,578 patients were metformin users and 4,042 were non-users. Propensity score matching was used to reduce possible confounding factors. In total, 4,182 patients (2,091 matched pairs) were included in the matched cohort. Cox proportional hazard model with time-dependent covariate were also applied to evaluate the association between metformin use and overall survival (OS).

Results

A total of 3,578 patients were metformin users at the time of diagnosis of NSCLC. Cox proportional hazard model with time-dependent covariate revealed that metformin use was associated with a significantly longer OS (HR: 0.85, 95.0% CI: 0.80–0.90). The survival benefit of metformin use was maintained after propensity score matching at a ratio of 1:1 (HR: 0.90, 95.0% CI: 0.84–0.97).

Conclusions

Metformin use is associated with longer OS in inoperable NSCLC patients with diabetes, suggesting a potential anti-tumorigenic effect for metformin. Further research is needed to investigate the actual role of metformin in the treatment of NSCLC patients with diabetes.

Metformin partially reverses the carboplatin-resistance in NSCLC by inhibiting glucose metabolism

Platinum-based chemotherapeutic drugs are irreplaceable for the treatment of advanced non-small cell lung cancer (NSCLC). However, acquired drug resistance has become a major obstacle for the clinical application of chemotherapy on NSCLC. In the present study, we established carboplatin-resistant NSCLC models on A549 and PC9 cell lines, which were named A549/R and PC9/R. Besides the low sensitivity of A549/R and PC9/R to carboplatin treatment, they exhibited higher metabolism rate of glucose compared to their parental A549 and PC9 cells, respectively. Mechanically, we confirmed that overexpression of PKM2 in A549/R and PC9/R was responsible for the high glucose metabolism and carboplatin resistance. Metformin, an antidiabetic drug, was observed to increase the sensitivity of carboplatin-resistant NSCLC cells to carboplatin treatment in vitro and in vivo. Mechanically, metformin decreased expression of PKM2 and subsequently inhibited the glucose uptake, lactate generation and ATP production in A549/R and PC9/R. Therefore, metformin promoted carboplatin-induced apoptosis through the mitochondria pathway. In addition, we demonstrated that metformin treatment also impaired the cross-resistance of A549/R and PC9/R to cisplatin, etoposide and 5-fluorouracil.

Metformin synergistic pemetrexed suppresses non-small-cell lung cancer cell proliferation and invasion in vitro

The aim of this study was to investigate whether metformin in combination with pemetrexed has an effect on the treatment of non-small-cell lung cancer (NSCLC) models and to explore the related molecular mechanism. The half maximal inhibitory concentration (IC50) and combination index (CI) of metformin and pemetrexed were detected by the CCK8 assay to assess the antiproliferative and therapeutic effects of the two-drug combination. Flow cytometry (FCM) and invasion assays were used to estimate the variation in apoptosis rate and invasion ability of the differently treated NSCLC cell lines. Apoptotic markers were detected by western blotting to validate the data related to the antiproliferation and proapoptosis effects. Metformin monotherapy inhibited the growth of NSCLC cell lines and reduced the invasion ability to different degrees compared with the control groups (P < 0.05). Metformin in combination with pemetrexed produced a synergistic effect (CI < 0.90) compared with the two drugs in monotherapy in the three tested NSCLC cell lines. Metformin in combination with pemetrexed significantly increased the cell numbers of HCC827 cells at S phase (P < 0.001), and the combination therapy had no influence on the A549 and H1975 cell lines. We found that combining metformin with pemetrexed induced more cell apoptosis than metformin or pemetrexed used alone (P < 0.05), which was validated by the apoptotic markers. These results demonstrate that the combination of metformin and pemetrexed has a synergistic effect on the treatment of NSCLC cell lines by inducing apoptosis or blocking the cell cycle. Our data indicate that the combination of metformin and pemetrexed could have beneficial antitumor effects on NSCLC cells in vitro.

Redox-dependent modulation of metformin contributes to enhanced sensitivity of esophageal squamous cell carcinoma to cisplatin

Glutathione is the major intracellular anti-oxidant against reactive oxygen species and serves as a detoxification essential. The anti-diabetic drug metformin has been showed to exert anti-tumor activity via modulation of redox homeostasis. In this study, we provided evidence that metformin inhibits proliferation and induces apoptosis of esophageal squamous cancer cells. Importantly, we found that metformin acts as pro-oxidant via depletion of intracellular glutathione. Co-treatment with metformin reversed the elevated intracellular glutathione induced by cisplatin and therefore enhanced the sensitivity to cisplatin in vitro and in vivo. Taken together, our data indicate that combination of metformin with cisplatin may represent a novel therapeutic strategy for esophageal squamous cell carcinoma treatment.

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.

Progress in the application and mechanism of metformin in treating non-small cell lung cancer

At present, the incidence and mortality of lung cancer demonstrate an increasing trend. Non-small cell lung cancer (NSCLC) accounts for ~80–85% of all lung cancer cases. Therefore, developing novel and more effective treatments is of great importance. The use of combination therapies, where several anticancer agents are used together, is a promising strategy. Recent studies demonstrate that metformin, which has been utilized for treating diabetes mellitus for >50 years, has antitumor effects in numerous types of cancer including NSCLC. Its antitumor effects can be direct and indirect, and it is able to synergize with other physical therapies including targeted anticancer therapy, chemotherapy and radiotherapy. The present review discusses how metformin affects cellular energy metabolism in NSCLC, the mechanism of its antitumor action and its synergy with other therapies. Information and analysis are provided in the present review to stimulate further studies on metformin as an adjunct anticancer treatment.

Co-delivery of polymeric metformin and cisplatin by self-assembled core-membrane nanoparticles to treat non-small cell lung cancer

Clinically, combined therapy of cisplatin (CDDP) and metformin is an effective treatment for non-small cell lung cancer (NSCLC). The success is attributed to synergistic effects between the two drugs. Therefore, we hypothesize that co-encapsulation of CDDP and metformin will avoid the prominent toxicity of CDDP while maintaining the synergy between the regimens. CDDP was first conjugated to polyglutamic acid (PGA) to form anionic PGA-CDDP which was electrostatically complexed with the cationic polymeric metformin (polymet). The nano-sized complex was then stabilized with cationic liposomes composed of DOTAP (2, 3-Dioleoyloxy-propyl)-trimethylammonium/Cholesterol/DSPE-PEG-anisamide aminoethyl. Both in vitro and in vivo experiments confirmed the synergy between polymet and CDDP. CDDP delivered with nanoparticles (NPs) exhibited significantly increased tumor accumulation over free CDDP and suppressed tumor growth through apoptosis in NSCLC H460 tumor-bearing mice without nephrotoxicity. The synergistic effect of polymet alongside CDDP demonstrates that polymet-CDDP NPs can activate the AMP-activated protein kinase α (AMPKα) pathway and inhibit mammalian target rapamycin (mTOR) activity to enhance growth suppression. In all, this platform is the first to successfully co-load polymet, a polymeric metformin, and CDDP into the same nanoparticle for successful treatment of NSCLC.

Combinational strategies of metformin and chemotherapy in cancers

Chemotherapeutic regimens are the most common treatment to inhibit tumor growth, but there is great variability in clinical responses of cancer patients; cancer cells often develop resistance to chemotherapeutics which results in tumor recurrence and further progression. Metformin, an extensively prescribed and well-tolerated first-line therapeutic drug for type 2 diabetes mellitus, has recently been identified as a potential and attractive anticancer adjuvant drug combined with chemotherapeutic drugs to improve treatment efficacy and lower doses. In this review, we summarized the molecular mechanisms underlying anticancer effects of metformin, which included insulin- and AMPK-dependent effects, selectively targeting cancer stem cells, reversing multidrug resistance, inhibition of the tumor metastasis and described the antineoplastic effects of metformin combined with chemotherapeutic agents in digestive system cancers (colorectal, gastric, hepatic and pancreatic cancer), reproductive system cancers (ovarian and endometrial cancer), prostate cancer, breast cancer, lung cancer, etc. Moreover, the clinical trials regarding metformin in combination of chemotherapeutic drugs were presented and the clinical obstacle or limitation related to the potential role of metformin in cancer treatment was also discussed in this review.

Improved progression free survival for patients with diabetes and locally advanced non-small cell lung cancer (NSCLC) using metformin during concurrent chemoradiotherapy

BACKGROUND AND PURPOSE

The aim was to investigate whether the use of metformin during concurrent chemoradiotherapy (cCRT) for locally advanced non-small cell lung cancer (NSCLC) improved treatment outcome.

MATERIAL AND METHODS

A total of 682 patients were included in this retrospective cohort study (59 metformin users, 623 control patients). All received cCRT in one of three participating radiation oncology departments in the Netherlands between January 2008 and January 2013. Primary endpoint was locoregional recurrence free survival (LRFS), secondary endpoints were overall survival (OS), progression-free survival (PFS) and distant metastasis free survival (DMFS).

RESULTS

No significant differences in LRFS or OS were found. Metformin use was associated with an improved DMFS (74% versus 53% at 2 years; p=0.01) and PFS (58% versus 37% at 2 years and a median PFS of 41 months versus 15 months; p=0.01). In a multivariate cox-regression analysis, the use of metformin was a statistically significant independent variable for DMFS and PFS (p=0.02 and 0.03).

CONCLUSIONS

Metformin use during cCRT is associated with an improved DMFS and PFS for locally advanced NSCLC patients, suggesting that metformin may be a valuable treatment addition in these patients. Evidently, our results merit to be verified in a prospective trial.

Metformin Synergistically Enhances Cisplatin-Induced Cytotoxicity in Esophageal Squamous Cancer Cells under Glucose-Deprivation Conditions

Previous studies suggest that metformin may exert a protective effect on cisplatin-induced cytotoxicity in cancer cells, and this finding has led to a caution for considering metformin use in the treatment of cancer patients. However, in this paper we provide the first demonstration that metformin synergistically augments cisplatin cytotoxicity in the esophageal squamous cancer cell line, ECA109, under glucose-deprivation conditions, which may be more representative of the microenvironment within solid tumors; this effect is very different from the previously reported cytoprotective effect of metformin against cisplatin in commonly used high glucose incubation medium. The potential mechanisms underlying the synergistic effect of metformin on cisplatin-induced cytotoxicity under glucose-deprivation conditions may include enhancement of metformin-associated cytotoxicity, marked reduction in the cellular ATP levels, deregulation of the AKT and AMPK signaling pathways, and impaired DNA repair function.

Metformin inhibits the invasion of human hepatocellular carcinoma cells and enhances the chemosensitivity to sorafenib through a downregulation of the ERK/JNK-mediated NF-κB-dependent pathway that reduces uPA and MMP-9 expression

Metformin has been shown to exert anti-cancer activities in several cancer cells and animal models. However, the molecular mechanisms of its anti-metastatic activities remain poorly understood and warrant further investigation. The aims of this study were to evaluate the ability of metformin to inhibit the migration and invasion of hepatocellular carcinoma (HCC) cells and identify its effects on signaling pathways. Our data indicate that metformin inhibits the migration and invasion of human HCC cells. Metformin was also found to significantly inhibit the expression and secretion of MMP-9 and uPA in HCC cells, and suppress the phosphorylation of ERK1/2 and JNK1/2. Treatment with an ERK1/2 inhibitor (PD98059) or JNK1/2 inhibitor (SP600125) enhanced the inhibitory effects of metformin on the migration and invasion of HCC cells. Moreover, metformin-induced inhibition of MMP-9 and uPA promoter activity also blocked the nuclear translocation of NF-κB and its binding to the MMP-9 and uPA promoters, and these suppressive effects were further enhanced by PD98059 or SP600125. Moreover, metformin markedly enhanced the anti-metastatic effects of sorafenib. In conclusion, metformin inhibits the migration and invasion of HCC cells by suppressing the ERK/JNK-mediated NF-κB-dependent pathway, and thereby reducing uPA and MMP-9 expression. Additionally, combination treatment with metformin and sorafenib yielded synergistic inhibitory effects in suppressing cell migration and invasion of HCC cells. These findings provide insight into the molecular mechanisms involved in the anti-metastatic effects of metformin, as well as its ability to enhance the chemosensitivity of HCC cells to sorafenib.