Metformin may protect nondiabetic breast cancer women from metastasis. Clin Exp Metastasis. 2016;33:339-357. [PMID: 26902691 DOI: 10.1007/s10585-016-9782-1]

Targeting cancer and immune cell metabolism with the complex I inhibitors metformin and IACS-010759

Metformin and IACS-010759 are two distinct antimetabolic agents. Metformin, an established antidiabetic drug, mildly inhibits mitochondrial complex I, while IACS-010759 is a new potent mitochondrial complex I inhibitor. Mitochondria is pivotal in the energy metabolism of cells by providing adenosine triphosphate through oxidative phosphorylation (OXPHOS). Hence, mitochondrial metabolism and OXPHOS become a vulnerability when targeted in cancer cells. Both drugs have promising antitumoral effects in diverse cancers, supported by preclinical in vitro and in vivo studies. We present evidence of their direct impact on cancer cells and their immunomodulatory effects. In clinical studies, while observational epidemiologic studies on metformin were encouraging, actual trial results were not as expected. However, IACS-01075 exhibited major adverse effects, thereby causing a metabolic shift to glycolysis and elevated lactic acid concentrations. Therefore, the future outlook for these two drugs depends on preventive clinical trials for metformin and investigations into the plausible toxic effects on normal cells for IACS-01075.

Metformin and Breast Cancer: Current Findings and Future Perspectives from Preclinical and Clinical Studies

Over the last several decades, a growing body of research has investigated the potential to repurpose the anti-diabetic drug metformin for breast cancer prevention and/or treatment. Observational studies in the early 2000s demonstrated that patients with diabetes taking metformin had decreased cancer risk, providing the first evidence supporting the potential role of metformin as an anti-cancer agent. Despite substantial efforts, two decades later, the exact mechanisms and clinical efficacy of metformin for breast cancer remain ambiguous. Here, we have summarized key findings from studies examining the effect of metformin on breast cancer across the translational spectrum including in vitro, in vivo, and human studies. Importantly, we discuss critical factors that may help explain the significant heterogeneity in study outcomes, highlighting how metformin dose, underlying metabolic health, menopausal status, tumor subtype, membrane transporter expression, diet, and other factors may play a role in modulating metformin's anti-cancer effects. We hope that these insights will help with interpreting data from completed studies, improve the design of future studies, and aid in the identification of patient subsets with breast cancer or at high risk for the disease who are most likely to benefit from metformin treatment.

The Effect of Metformin on Chemotherapy-Induced Toxicities in Non-diabetic Breast Cancer Patients: A Randomised Controlled Study

BACKGROUND AND OBJECTIVE

Breast cancer patients treated with adriamycin-cyclophosphamide plus paclitaxel (AC-T) are often challenged with serious adverse effects for which no effective therapies are available. Here, we investigated whether metformin, an antidiabetic drug with additional pleiotropic effects could favourably offset AC-T induced toxicities.

PATIENTS AND METHODS

Seventy non-diabetic breast cancer patients were randomised to receive either AC-T (adriamycin 60 mg/m² + cyclophosphamide 600 mg/m² × 4 cycles Q21 days, followed by weekly paclitaxel 80 mg/m² × 12 cycles) alone or AC-T plus metformin (1700 mg/day). Patients were assessed regularly after each cycle to record the incidence and severity of adverse events based on the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE), version 5.0. Moreover, baseline echocardiography and ultrasonography were done and repeated after the end of neoadjuvant therapy.

RESULTS

Addition of metformin to AC-T resulted in significantly less incidence and severity of peripheral neuropathy, oral mucositis, and fatigue (p < 0.05) compared to control arm. Moreover, the left ventricular ejection fraction (LVEF%) in the control arm dropped from a mean of 66.69 ± 4.57 to 62.2 ± 5.22% (p = 0.0004) versus a preserved cardiac function in the metformin arm (64.87 ± 4.84 to 65.94 ± 3.44%, p = 0.2667). Furthermore, fatty liver incidence was significantly lower in metformin compared with control arm (8.33% vs 51.85%, p = 0.001). By contrast, haematological disturbances caused by AC-T were preserved after concurrent metformin administration (p > 0.05).

CONCLUSION

Metformin offers a therapeutic opportunity for controlling toxicities caused by neoadjuvant chemotherapy in non-diabetic breast cancer patients.

TRIAL REGISTRATION

This randomised controlled trial was registered on November 20, 2019 in ClinicalTrials.gov under registration number: NCT04170465.

Is it still worth pursuing the repurposing of metformin as a cancer therapeutic?

Over the past 15 years, there has been great interest in the potential to repurpose the diabetes drug, metformin, as a cancer treatment. However, despite considerable efforts being made to investigate its efficacy in a number of large randomised clinical trials in different tumour types, results have been disappointing to date. This perspective article summarises how interest initially developed in the oncological potential of metformin and the diverse clinical programme of work to date including our contribution to establishing the intra-tumoral pharmacodynamic effects of metformin in the clinic. We also discuss the lessons that can be learnt from this experience and whether a further clinical investigation of metformin in cancer is warranted.

Metformin: Activation of 5′ AMP-activated protein kinase and its emerging potential beyond anti-hyperglycemic action

Metformin is a plant-based drug belonging to the class of biguanides and is known to treat type-2 diabetes mellitus (T2DM). The drug, combined with controlling blood glucose levels, improves the body’s response to insulin. In addition, trials have identified the cardioprotective potential of metformin in the diabetic population receiving the drug. Activation of 5′ AMP-activated protein kinase (AMPK) is the major pathway for these potential beneficial effects of metformin. Historically, much emphasis has been placed on the potential indications of metformin beyond its anti-diabetic use. This review aims to appraise other potential uses of metformin primarily mediated by the activation of AMPK. We also discuss various mechanisms, other than AMPK activation, by which metformin could produce beneficial effects for different conditions. Databases including PubMed/MEDLINE and Embase were searched for literature relevant to the review’s objective. Reports from both research and review articles were considered. We found that metformin has diverse effects on the human body systems. It has been shown to exert anti-inflammatory, antioxidant, cardioprotective, metabolic, neuroprotective, anti-cancer, and antimicrobial effects and has now even been identified as effective against SARS-CoV-2. Above all, the AMPK pathway has been recognized as responsible for metformin’s efficiency and effectiveness. Owing to its extensive potential, it has the capability to become a part of treatment regimens for diseases apart from T2DM.

Efficacy of metformin therapy in patients with cancer: a meta-analysis of 22 randomised controlled trials

BACKGROUND

To investigate whether metformin monotherapy or adjunctive therapy improves the prognosis in patients with any type of cancer compared to non-metformin users (age ≥18).

METHODS

Databases (Medline, Embase, and the Cochrane Central Register of Controlled Trials) and clinical trial registries ( ClinicalTrials.gov ; the World Health Organization International Clinical Trials Registry Platform) were screened for randomized, controlled trials (RCT) reporting at least progression-free survival (PFS) and/or overall survival (OS). Main outcome measures included hazard ratios (HR), and combined HRs and 95% confidence intervals (CI) were calculated using random-effects models.

RESULTS

Of the 8419 records screened, 22 RCTs comprising 5943 participants were included. Pooled HRs were not statistically significant in both PFS (HR 0.97, 95% CI 0.82-1.15, I² = 50%) and OS (HR 0.98, 95% CI 0.86-1.13, I² = 33%) for patients with cancer between the metformin and control groups. Subgroup analyses demonstrated that metformin treatment was associated with a marginally significant improvement in PFS in reproductive system cancers (HR 0.86, 95% CI 0.74-1.00) and a significantly worse PFS in digestive system cancers (HR 1.45, 95% CI 1.03-2.04). The PFS or OS was observed consistently across maintenance dose, diabetes exclusion, median follow-up, risk of bias, and combined antitumoral therapies.

CONCLUSION

Metformin treatment was not associated with cancer-related mortality in adults compared with placebo or no treatment. However, metformin implied beneficial effects in the PFS of the patients with reproductive system cancers but was related to a worse PFS in digestive system cancers.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42022324672.

Insulin-like growth factor role in determining the anti-cancer effect of metformin: RCT in prostate cancer patients

OBJECTIVE

Androgen deprivation therapy (ADT), a principal therapy in patients with prostate cancer, is associated with the development of obesity, insulin resistance, and hyperinsulinemia. Recent evidence indicates that metformin may slow cancer progression and improves survival in prostate cancer patients, but the mechanism is not well understood. Circulating insulin-like growth factors (IGFs) are bound to high-affinity binding proteins, which not only modulate the bioavailability and signalling of IGFs but also have independent actions on cell growth and survival. The aim of this study was to investigate whether metformin modulates IGFs, IGF-binding proteins (IGFBPs), and the pregnancy-associated plasma protein A (PAPP-A) - stanniocalcin 2 (STC2) axis.

DESIGN AND METHODS

In a blinded, randomised, cross-over design, 15 patients with prostate cancer on stable ADT received metformin and placebo treatment for 6 weeks each. Glucose metabolism along with circulating IGFs and IGFBPs was assessed.

RESULTS

Metformin significantly reduced the homeostasis model assessment as an index of insulin resistance (HOMA IR) and hepatic insulin resistance. Metformin also reduced circulating IGF-2 (P < 0.05) and IGFBP-3 (P < 0.01) but increased IGF bioactivity (P < 0.05). At baseline, IGF-2 correlated significantly with the hepatic insulin resistance (r2= 0.28, P < 0.05). PAPP-A remained unchanged but STC2 declined significantly (P < 0.05) following metformin administration. During metformin treatment, change in HOMA IR correlated with the change in STC2 (r2= 0.35, P < 0.05).

CONCLUSION

Metformin administration alters many components of the circulating IGF system, either directly or indirectly via improved insulin sensitivity. Reduction in IGF-2 and STC2 may provide a novel mechanism for a potential metformin-induced antineoplastic effect.

Factors influencing the anticancer effects of metformin on breast cancer outcomes: a systematic review and meta-analysis

INTRODUCTION

Several clinical trials have attempted to find evidence that supports the use of metformin as an anticancer treatment. However, the observed effects on various breast cancer (BC) outcomes have been heterogeneous.

AREAS COVERED

Based on the outcomes of previous clinical trials, this review discusses the patients' characteristics, cancer intrinsic subtypes, cancer stage, and anticancer treatments that may influence the anticancer effect of metformin on BC outcomes. Additionally, the safety and tolerability of metformin addition to various anticancer regimens are reviewed.

EXPERT OPINION

Metformin is a challenging anticancer agent in BC cohorts, besides being safe and well-tolerated at antidiabetic doses. Survival benefits of metformin have been observed in BC patients with: hormone receptor-positive, human epidermal growth factor receptor-2 overexpression, and high insulin like growth factor-1 receptor expression on the tumor surface. Moreover, patients with diabetes receiving metformin experienced better survival outcomes compared to diabetic patients not receiving metformin. Additionally, metformin has anti-proliferative activity in patients with BC who have high insulin resistance and high body mass index. Besides, metformin has been shown to decrease metastatic events, and enhance the level of metabolic- and insulin-related biomarkers associated with carcinogenesis. Finally, most adverse events following metformin treatment were low-grade GIT toxicities.

Metformin inhibits gastric cancer cell proliferation by regulation of a novel Loc100506691-CHAC1 axis

Long noncoding RNAs (lncRNAs) are a group of nonprotein coding transcripts that play a critical role in cancer progression. However, the role of lncRNA in metformin-induced inhibition of cell growth and its biological function in gastric cancer remain largely unknown. In this study, we identified an oncogenic lncRNA, Loc100506691, the expression of which was decreased in gastric cancer cells with metformin treatment. Moreover, Loc100506691 was significantly overexpressed in gastric cancer compared with adjacent normal tissues (p < 0.001), and high Loc100506691 expression was significantly correlated with poor survival of patients with gastric cancer. Additionally, Loc100506691 knockdown could significantly suppress gastric cancer cell growth in vitro, and ectopic Loc100506691 expression accelerated tumor growth in an in vivo mouse model. Analysis of the cell cycle revealed that Loc100506691 knockdown induced cell cycle arrest at the G2/M phase by impairing cell entry from the G2/M to G1 phase. Loc100506691 negatively regulated CHAC1 expression by modulating miR-26a-5p/miR-330-5p expression, and CHAC1 knockdown markedly attenuated Loc100506691 knockdown-induced gastric cancer cell growth and motility suppression. We concluded that anti-proliferative effects of metformin in gastric cancer may be partially caused by suppression of the Loc100506691-miR-26a-5p/miR-330-5p-CHAC1 axis.

Metformin and survival of women with breast cancer: A meta-analysis of randomized controlled trials

WHAT IS KNOWN AND OBJECTIVE

Metformin has been suggested to confer anticancer efficacy. However, it remains uncertain whether additional use of metformin could improve survival of women with breast cancer. We performed a meta-analysis of randomized controlled trials (RCTs) to evaluate the influence of metformin on survival outcome in women with breast cancer.

METHODS

Relevant RCTs were obtained by search of PubMed, Embase and Cochrane's Library databases from inception to 15 May 2021. A random-effects model incorporating the potential publication bias was used to pool the results.

RESULTS AND DISCUSSION

Five phase II RCTs including 396 non-diabetic women with breast cancer were included in the meta-analysis. Pooled results showed that additional use of metformin was not associated with improved progression-free survival (PFS, hazard ratio [HR]: 1.00, 95% confidence interval [CI]: 0.70 to 1.43, p = 0.98; I²  = 32%) or overall survival (OS, HR: 1.00, 95% CI: 0.71 to 1.39, p = 0.98; I²  = 0%). Sensitivity analysis by excluding one study at a time showed consistent results (HR for PFS: 0.91 to 1.14, p all >0.05; HR for OS: 0.88 to 1.21, P all >0.05).

WHAT IS NEW AND CONCLUSION

Current evidence from phase II clinical trials does not support that additional use of metformin could improve the survival outcome in women with breast cancer.

Efficacy of Metformin in Patients With Breast Cancer Receiving Chemotherapy or Endocrine Therapy: Systematic Review and Meta-analysis

BACKGROUND

Previous studies have suggested that metformin might improve survival outcomes in patients with breast cancer. However, findings on the efficacy of metformin with chemotherapy or endocrine therapy are inconsistent.

OBJECTIVE

To clarify the efficacy of metformin with chemotherapy or endocrine therapy in breast cancer patients according to the treatment setting, including neoadjuvant, adjuvant, and metastasis/recurrence.

METHODS

We systematically searched for randomized controlled trials (RCTs) in MEDLINE, CENTRAL, and EMBASE from inception through July 2020. Overall survival (OS), progression-free survival (PFS), and hypoglycemia rate were the primary outcomes. Secondary outcomes included severe adverse events (SAEs) and relapse-free survival. We used the Grading of Recommendations Assessment, Development, and Evaluation approach and performed a meta-analysis to evaluate the efficacy and safety of metformin with chemotherapy and endocrine therapy in patients with breast cancer.

RESULTS

Our systematic review included 412 participants from 5 trials. Metformin showed little to no difference in OS (hazard ratio [HR] = 1.13; 95% CI = 0.71-1.81; certainty of evidence [COE], moderate) and PFS (HR = 1.14; 95% CI = 0.86-1.50; COE, moderate) in patients with metastasis/recurrence. The evidence was very uncertain about the effect of metformin on survival outcomes in patients who received metformin with neoadjuvant or adjuvant treatment. Metformin showed little to no difference in hypoglycemia and SAEs.

CONCLUSION AND RELEVANCE

Metformin should be discouraged routinely in nondiabetic patients with metastatic/recurrent breast cancer. Further RCTs are needed to verify whether metformin with chemotherapy or endocrine therapy results in significant clinical benefits in the neoadjuvant or adjuvant setting.

Metformin induces apoptosis and inhibits migration by activating the AMPK/p53 axis and suppressing PI3K/AKT signaling in human cervical cancer cells

Human cervical cancer is the fourth most common malignancy among women worldwide, and it is expected to result in 460,000 deaths per year by 2040. Moreover, patients with cervical cancer often display drug resistance and severe side effects; therefore, the development of effective novel chemotherapeutic agents is important. In the present study, the effects of metformin, a first-line therapeutic drug for type 2 diabetes mellitus, were evaluated in cervical cancer. Compared with the control group, metformin significantly inhibited cell viability and migration, and induced apoptosis and cell cycle arrest in human cervical cancer cell lines (CaSki and HeLa). Following metformin treatment, the protein expression levels of p-AMP-activated protein kinase (p-AMPK), which promotes cell death, and the tumor suppressor protein p-p53 were remarkably upregulated in CaSki and C33A cells compared with the control group. Furthermore, compared with the control group, metformin significantly suppressed the PI3K/AKT signaling pathway in CaSki, C33A and HeLa cells. Compound C (an AMPK inhibitor) significantly reversed the effects of metformin on CaSki, C33A and HeLa cell viability, and AMPK and p53 phosphorylation. The results of the present study suggested that metformin induced AMPK-mediated apoptosis, thus metformin may serve as a chemotherapeutic agent for human cervical cancer.

Metformin: current clinical applications in nondiabetic patients with cancer

Metformin is one of the most commonly used first-line oral medications for type 2 diabetes mellitus. Multiple observational studies, reviewed in numerous systematic reviews, have shown that metformin treatment may not only reduce the risk of cancer but may also improve the efficacy of cancer treatment in diabetic patients. Recent studies have been conducted to determine whether a similar protective effect can be demonstrated in nondiabetic cancer patients. However, the results are controversial. The potential optimal dose, schedule, and duration of metformin treatment and the heterogeneity of histological subtypes and genotypes among cancer patients might contribute to the different clinical benefits. In addition, as the immune property of metformin was investigated, further studies of the immunomodulatory effect of metformin on cancer cells should also be taken into account to optimize its clinical use. In this review, we present and discuss the latest findings regarding the anticancer potential of metformin in nondiabetic patients with cancer.

For colorectal cancer patients with type II diabetes, could metformin improve the survival rate? A meta-analysis

OBJECTIVE

Current research is controversial about whether metformin can improve the survival rate of patients with colon cancer. Therefore, we conducted a meta-analysis to identify the association between metformin and the survival rate of colorectal cancer (CRC) patients with type II diabetes.

METHODS

We conducted a search in databases including Pubmed, EMBASE and Cochrane Library. All articles were published in the last decade, and the quality of each study was evaluated by the Newcastle-Ottawa Scale. Odds ratios (ORs) and its corresponding 95% confidence intervals (CIs) for each study were calculated and summary relative risk estimates with corresponding 95% CIs were generated using the random-effects model. Heterogeneity and publication bias were assessed.

RESULTS

Ten articles were included in this meta-analysis. The included articles were all cohort studies. In a pooled analysis of all studies, metformin using was associated with increased overall survival (OS) rate (OR, 0.54; 95% CI, 0.47 to 0.63) and cancer-specific survival (CS) rate (OR 0.59; 95% CI 0.43 to 0.82) of CRC patients with diabetes. We found that the effect of metformin is associated with geographical region through subgroup meta-analysis.

CONCLUSIONS

Metformin using was associated with an increased OS rate and CS rate of colorectal cancer.

The effect of metformin use on hypopharyngeal squamous cell carcinoma in diabetes mellitus patients

Background

Metformin is proven to improve the prognosis of various cancers, but it is unknown if metformin could ameliorate hypopharyngeal cancer in diabetes mellitus patients. This was a retrospective cohort study, and the effect and survival outcome of metformin on hypopharyngeal cancer with diabetes mellitus was investigated.

Methods

There were 141 hypopharyngeal cancer patients collected in a tertiary referral center from December 1st, 2011 to December 31st, 2013. There were 49 patients without diabetes mellitus (DM) and 92 patients with DM. In the 92 DM patients, there were 43 patients with metformin used and 49 patients without metformin used. All received patients followed up until September 1st, 2015.

Results

There was no significant difference in patients’ characteristics between the non-DM and DM groups, and also no significant difference in clinical T stage, N stage, metastatic condition, and disease stage between the non-DM and DM groups. DM with metformin patients had lower metastasis rates and better overall survival (OS) (p = 0.011) and disease-free survival (DFS) (p = 0.004) compared to non-DM and DM without metformin. Multivariate analysis also showed a better OS and DFS in DM-Met (+) with advanced hypopharyngeal cancer but not in early stage.

Conclusion

There was less distant metastasis and better survival outcomes in hypopharyngeal cancer DM patients who use metformin.

Metformin as an adjuvant in breast cancer treatment

Breast cancer is one of the most common malignancies in females. It is an etiologically complex disease driven by a multitude of cellular pathways. The proliferation and spread of breast cancer is intimately linked to cellular glucose metabolism, given that glucose is an essential cellular metabolic substrate and that insulin signalling has mitogenic effects. Growing interest has focused on anti-diabetic agents in the management of breast cancer. Epidemiologic studies show that metformin reduces cancer incidence and mortality among type 2 diabetic patients. Preclinical in vitro and in vivo research provides intriguing insight into the cellular mechanisms behind the oncostatic effects of metformin. This article aims to provide an overview of the mechanisms in which metformin may elicit its anti-cancerous effects and discuss its potential role as an adjuvant in the management of breast cancer.

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.

Metformin and melatonin improve histopathological outcome of NMU-induced mammary tumors in rats

OBJECTIVE

Numerous reports showed inhibition of carcinogenesis after metformin (MF) and melatonin (MEL) administration. However, most in vivo studies used standard diet type, with relatively low fat content. As increase in fat intake may have a considerable impact on malignant transformation, we evaluated the effects of these two substances in a model of mammary carcinogenesis in rats fed a high-fat diet (10%).

METHODS

Mammary tumors were induced by N-methyl-N-nitrosourea (NMU) in female rats of sensitive Sprague-Dawley strain. MF was administered in a diet (0.2%), MEL was administered in drinking water (20 mg/L). The chemoprevention was initiated 12 days prior to tumor initiation, both substances were administered through the termination of the experiment on 16th week after carcinogen application. Analysis of basic parameters of tumor growth, histopathological profile, and serum IGF-1 level were performed together with immunohistochemical detection of Ki67 (proliferation marker) and caspase-3 and BCL-2 (apoptosis markers) in mammary cancer cells.

RESULTS

Although neither tumor incidence nor frequency were changed after MF and/or MEL administration, MF and MEL decreased high-grade/low-grade (HG/LG) tumor ratio. MEL decreased proliferation in mammary cancer cells; positive correlations between histological grade and Ki67 expressions were found after single administration of both MF and MEL. Serum IGF-1 levels were reduced to the level of intact rats in all groups receiving chemoprevention.

CONCLUSIONS

MF and MEL administration did not inhibit growth of NMU-induced mammary tumors in rats in a significant manner but both substances ameliorated tumor histopathological profile. Surprisingly, combined treatment had no such effect.

Melatonin May Increase Anticancer Potential of Pleiotropic Drugs

Melatonin (N-acetyl-5-methoxytryptamine) is not only a pineal hormone, but also an ubiquitary molecule present in plants and part of our diet. Numerous preclinical and some clinical reports pointed to its multiple beneficial effects including oncostatic properties, and as such, it has become one of the most aspiring goals in cancer prevention/therapy. A link between cancer and inflammation and/or metabolic disorders has been well established and the therapy of these conditions with so-called pleiotropic drugs, which include non-steroidal anti-inflammatory drugs, statins and peroral antidiabetics, modulates a cancer risk too. Adjuvant therapy with melatonin may improve the oncostatic potential of these drugs. Results from preclinical studies are limited though support this hypothesis, which, however, remains to be verified by further research.

Metformin Inhibits Migration and Invasion by Suppressing ROS Production and COX2 Expression in MDA-MB-231 Breast Cancer Cells

Background: Several mechanisms of action have been proposed to explain the apparent antineoplastic functions of metformin, many of which are observed at high concentrations that may not be reflective of achievable tissue concentrations. We propose that metformin at low concentrations functions to inhibit ROS production and inflammatory signaling in breast cancer, thereby reducing metastasis. Methods: Using the highly invasive MDA-MB-231 breast carcinoma model, we ascertained the impact of metformin on cell viability by DNA content analysis and fluorescent dye exclusion. Migration and invasion assays were performed using a modified Boyden chamber assay and metastasis was ascertained using the chorioallantoic membrane (CAM) assay. PGE2 production was measured by Enzyme-Linked Immunosorbent Assay (ELISA). COX2 and ICAM1 levels were determined by flow cytometry immunoassay. Results: Metformin acutely decreased cell viability and caused G2 cell cycle arrest only at high concentrations (10 mM). At 100 µM, however, metformin reduced ICAM1 and COX2 expression, as well as reduced PGE2 production and endogenous mitochondrial ROS production while failing to significantly impact cell viability. Consequently, metformin inhibited migration, invasion in vitro and PGE2-dependent metastasis in CAM assays. Conclusion: At pharmacologically achievable concentrations, metformin does not drastically impact cell viability, but inhibits inflammatory signaling and metastatic progression in breast cancer cells.

Expressions of IGF-1, ERK, GLUT4, IRS-1 in metabolic syndrome complicated with colorectal cancer and their associations with the clinical characteristics of CRC

BACKGROUND

Epidemiological data have revealed that colorectal cancer (CRC) risk is increased in patients with Metabolic syndrome.

OBJECTIVE

To explore the expressions of IGF-1, ERK, GLUT4, IRS-1 in MS patients with CRC and their associations with the clinical characteristics of CRC.

METHODS

We investigated the expressions of IGF-1, ERK, GLUT4 and IRS-1 in greater omental adipose tissues of 168 MS patients with/without CRC, 85 CRC patients without MS and 98 healthy controls by RT-PCR, and analyzed the relationships between their expressions and clinical characteristics of CRC.

RESULTS

The expression levels of IGF-1 and ERK in MS patients with/without CRC were higher while the expression levels of GLUT4 were lower compared with CRC patients without MS and healthy controls (P< 0.01). The expression levels of IGF-1 and ERK in MS patients with CRC were higher while expression levels of GLUT4 were lower compared to MS patients without CRC (P< 0.01). Expression levels of ERK, IGF-1, GLUT4 were associated with clinical characteristics of CRC, including tumor size, distant metastasis and advanced stages (III/IV) (P< 0.05).

CONCLUSIONS

Expressions of IGF-1, ERK and GLUT4 in greater omental adipose tissues might be useful biomarkers and predictive targets in the diagnosis of CRC.

Metformin and melatonin inhibit DMBA-induced mammary tumorigenesis in rats fed a high-fat diet

The data from in-vitro and in-vivo studies show that both peroral antidiabetic metformin (MF) and pineal hormone melatonin (MT) inhibit the growth of many cancers, including breast cancer. However, most in-vivo studies used standard-type diet with low fat content. Therefore, in this study, we evaluated the chemopreventive effect of MF and MT in an in-vivo model of breast cancer in rats on a high-fat diet (10% of total fat). Mammary carcinogenesis was induced by 7,12-dimethylbenz[a]anthracene (DMBA) in female Sprague-Dawley rats. Chemoprevention with MF (administered in a diet, 0.2%) and MT (administered in tap water, 20 mg/l) was induced 20 days before the carcinogen administration through the termination of the experiment (14 weeks after carcinogen administration). Tumor growth parameters were analyzed together with histopathological examination and immunohistochemical detection of KI67 (proliferation marker), caspase-3, BAX, BCL-2 (apoptosis markers), and CD24 and CD44 (cancer stem cell markers) in mammary tumor samples. The combination of chemopreventive agents decreased tumor incidence by 29%. Cumulative tumor volume was lower in all groups treated with chemoprevention. Histopathology did not show significant changes in high-grade/low-grade tumor ratio. Immunohistochemistry showed increased expression of BAX in the combination group, and caspase-3 expression increased in both MT and combination groups. MT, and particularly the MF and MT combination, inhibited DMBA-induced mammary tumor growth in rats by apoptosis stimulation in cancer cells. Our results indicate that MT supplements in patients treated with MF may have a considerable effect on the incidence of breast cancer.

Hypoxia negates hyperglycaemia-induced chemo-resistance in breast cancer cells: the role of insulin-like growth factor binding protein 2

Background

Women who suffer from breast cancer and type II diabetes with associated hyperglycaemia respond less well to chemotherapy. We have shown that hyperglycaemia induces resistance to chemotherapy through upregulation of fatty acid synthase (FASN) in breast cancer cells and increased insulin-like binding protein 2 (IGFBP-2) in prostate cancer cells. As a tumour develops the tumour mass can outgrow the blood supply resulting in the cancer cells being exposed to hypoxia that stimulates many tumorigenic signalling pathways.

Methods

We used MCF-7 and T47D breast cancer cell lines. Trypan blue dye exclusion assay was employed to assess cell death and Western immunoblotting was used to determine changes in protein abundance. Hypoxia was induced both chemically by the addition of cobalt chloride (CoCl₂) and using a hypoxia chamber.

Results

IGFBP-2 abundance increased with increasing concentrations of glucose (0-25 mM) that contributed to hyperglycaemia-induced chemo-resistance as it was abrogated by downregulating IGFBP-2 using siRNA. Production of IGFBP-2 is ER dependent: pre-treatment of MCF-7 cells with β-estradiol increased IGFBP-2 and induced chemo-resistance to doxorubicin. The hyperglycaemia-induced chemo-resistance and increases in FASN and IGFBP-2 were negated in a hypoxic environment, with levels of cell death unaffected by glucose concentrations.

Conclusions

The sensitivity of breast cancer cells to chemotherapy is reduced in hyperglycaemic conditions but this effect is negated by hypoxia. These effects appear to be mediated via regulation of IGFBP-2 and FASN. Understanding the role of FASN and IGFBP-2 in chemo-resistance could provide a novel target for improving the effectiveness of breast cancer treatment.

Expression of metastasis related genes S100A4 and MMP-9 in pancreatic cancer cells treated with metformin

AIM

To investigate the expression of metastasis related genes S100A4 and matrix metalloproteinase (MMP)-9 in pancreatic cancer cell lines BxPC-3 and AsPC-1 treated with metformin.

METHODS

Cells were incubated with metformin at different concentrations for 24, 48, or 72 h. Then, cell viability was measured by MTT assay, and IC₅₀ values were calculated. The two cell lines were then treated with metformin at IC₅₀ concentrations for 48 h, and RT-PCR was used to detect the expression of S100A4 and MMP-9 mRNAs.

RESULTS

Cell viability was apparently inhibited by metformin in both cell lines, and the inhibitory effect showed a time- and dose-dependent manner. The IC₅₀ values for BxPC-3 cells at 24, 48, and 72 h were 12.13 mmol/L, 10.43 mmol/L, and 9.55 mmol/L, respectively, and the corresponding values for AsPC-1 cells were 23.45 mmol/L, 15.44 mmol/L, and 11.30 mmol/L. After treatment with metformin for 48 h, the expression of S100A4 and MMP-9 mRNAs in the two cell lines was significantly decreased compared with control cells (P < 0.01).

CONCLUSION

Metformin inhibits pancreatic cancer cell growth in a time- and dose-dependent manner. Metformin may exert anti-metastasis effects by decreasing the expression of S100A4 and MMP-9 in pancreatic cancer cell lines.

An Integrated Genome-Wide Systems Genetics Screen for Breast Cancer Metastasis Susceptibility Genes

Metastasis remains the primary cause of patient morbidity and mortality in solid tumors and is due to the action of a large number of tumor-autonomous and non-autonomous factors. Here we report the results of a genome-wide integrated strategy to identify novel metastasis susceptibility candidate genes and molecular pathways in breast cancer metastasis. This analysis implicates a number of transcriptional regulators and suggests cell-mediated immunity is an important determinant. Moreover, the analysis identified novel or FDA-approved drugs as potentially useful for anti-metastatic therapy. Further explorations implementing this strategy may therefore provide a variety of information for clinical applications in the control and treatment of advanced neoplastic disease.

Metastasis, the spread and growth of tumor cells from the original tumor to secondary sites throughout the body, is the primary cause of cancer-related death for most solid tumor types. The process of metastasis is very complex, requiring multiple individual steps and the cooperation of different cell types during the dissemination and proliferation steps. Many genes are involved in this process, but at present few have been identified and characterized. In this study, we have integrated multiple genome-wide analysis methods to try to identify large numbers of candidate metastasis-associated genes and pathways based on a highly metastatic mouse model. Using this strategy, we have identified a number of genes that predict outcome of human breast cancer. These genes implicate specific molecular and cellular pathways in the metastatic process that might be used to intervene in the process. Furthermore, this integrated analysis implicates pre-existing drugs that might be re-purposed to help prevent or reduce metastatic burden in patients. The combined results obtained from this analytical strategy therefore provide an important platform for further genome-wide analysis into the etiology of metastatic disease.