Metformin intervention in obese non-diabetic patients with breast cancer: phase II randomized, double-blind, placebo-controlled trial

Metformin mitigates dementia risk among individuals with type 2 diabetes

This mini-narrative review explores the relationship between diabetes and dementia, focusing on the potential mitigating role of metformin in reducing cognitive decline among individuals with type 2 diabetes. The interplay of factors such as glycemic control, diabetic complications, and lifestyle influences characterises diabetes-related dementia. This review emphasises the significance of comprehensive diabetes management in addressing the heightened risk of dementia in this population. Methodologically, the review synthesises evidence from 23 studies retrieved through searches on PubMed, Embase, Google Scholar, and Scopus. Current evidence suggests a predominantly positive association between metformin use and a reduced risk of dementia in individuals with diabetes. However, the review shows the complex nature of these outcomes, revealing variations in results in some studies. These discrepancies show the importance of exploring dose-response relationships, long-term effects, and demographic diversity to unravel the complexities of metformin's impact on cognitive health. Limitations in the existing body of research, including methodological disparities and confounding variables, necessitate refined approaches in future studies. Large-scale prospective longitudinal studies and randomised controlled trials focusing specifically on cognitive effects are recommended. Propensity score matching and exploration of molecular mechanisms can enhance the validity of findings in clinical practice. From a clinical perspective, metformin can serve as a potential adjunctive therapy for individuals with diabetes at risk of cognitive decline.

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.

Metformin: A Promising Antidiabetic Medication for Cancer Treatment

Metformin is a widely used drug in patients with type 2 diabetes mellitus. Metformin inhibits hepatic gluconeogenesis and increases glucose utilization in peripheral tissues. In recent years, several studies have shown that metformin is a potential therapeutic agent against cancer, alone or combined with other anticancer treatments. Metformin mainly activates the AMPK complex and regulates intracellular energy status, inhibiting the mitochondrial respiratory chain complex I and reducing the production of reactive oxygen species. Other anticancer targets of metformin are specific transcription factors inhibiting cell proliferation, promoting apoptosis and reducing drug resistance. In addition, metformin modulates tumor cells' response to anticancer treatments, favoring the activity of T cells. In diabetic patients, metformin reduces the occurrence of cancer and improves the prognosis and efficacy of anticancer treatments. In this review, we provided a comprehensive perspective of metformin as an anticancer drug.

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.

De novo cholesterol biosynthesis: an additional therapeutic target for the treatment of postmenopausal breast cancer with excessive adipose tissue

The onset and development of breast cancer in postmenopausal women are associated with closely related individual-dependent factors, including weight gain and high levels of circulating androgens. Adipose tissue is the most peripheral site of aromatase enzyme synthesis; therefore, the excessive accumulation of visceral fat results in increased androgens aromatization and estradiol production that provides the microenvironment favorable to tumorigenesis in mammary epithelial cells expressing estrogen receptors (ERs). Moreover, to meet the increased requirement of cholesterol for cell membrane assembly and the production of steroid hormones to sustain their proliferation, ER-positive cells activate de novo cholesterol biosynthesis and subsequent steroidogenesis. Several approaches have been followed to neutralize the de novo cholesterol synthesis, including specific enzyme inhibitors, statins, and, more recently, metformin. Cumulating evidence indicated that inhibiting cholesterol biosynthesis by statins and metformin may be a promising therapeutic strategy to block breast cancer progression. Unlike antiestrogens and aromatase inhibitors (AIs) which compete for binding to ER and inhibit androgens aromatization, respectively, statins block the production of mevalonic acid by inhibiting the activity of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, and metformin hampers the activation of the sterol regulatory element-binding protein 2 (SREBP2) transcription factor, thus inhibiting the synthesis of several enzymes involved in cholesterol biosynthesis. Noteworthy, statins and metformin not only improve the prognosis of overweight patients with ER-positive cancer but also improve the prognosis of patients with triple-negative breast cancer, the aggressive tumor subtype that lacks, at present, specific therapy.

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.

Influences of preoperative metformin on immunological factors in early breast cancer

PURPOSE

Metformin has been suggested to possibly reduce cancer risk. However, the mechanism underlying the positive effects of metformin on cancer treatment remains unclear. We conducted a prospective study to evaluate the effects of preoperative metformin in patients with early breast cancer.

METHOD

We evaluated the effects on immunological factors (TILs, CD4 + , CD8 + , PD-L1, IFNγ and IL-2) by comparing core needle biopsies (CNB) obtained before metformin treatment with surgical specimens. Seventeen patients were enrolled in this prospective study from January to December 2016. We also analyzed 59 patients undergoing surgery during the same period to reveal the correlation of immune factors between CNB and surgical specimen.

RESULT

There was a moderate correlation between CNB and surgical specimens on TILs and CD8 + lymphocyte. (TILs Rs = 0.63, CD4 + Rs = 0.224, CD8 + Rs = 0.42) In the metformin group, TILs increases were confirmed in five (29%) patients, while a decrease was confirmed in two (12%). The expressions of CD4 + and CD8 + by TILs were increased in 41% and 18% of surgical specimens, respectively. However, TILs number (p = 0.0554), CD4+ (p = 0.0613) and CD8 + (p = 0.0646) expressions did not significantly increased. Furthermore, IFNγ expression appeared to be increased in response to metformin (p = 0.08).

CONCLUSION

Preoperative metformin tends to increase TILs, as well as the numbers of CD4 and CD8 positive lymphocytes, and IFNγ levels. Metformin might improve immune function and have a possibility of chemo-sensitivity and thereby increase the effectiveness of immunotherapy, based on the results of this preliminary study.

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.

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.

The effect of metformin on biomarkers associated with breast cancer outcomes: a systematic review, meta-analysis, and dose-response of randomized clinical trials

PURPOSE

Breast cancer is a leading cause of cancer mortality in developed countries. We performed a meta-analysis of randomized clinical trials to investigate the effect of metformin on biomarkers associated with breast cancer outcomes and to explore the dose-response relationship.

METHODS

A systematic search was performed from onset of the database to January 2019 in MEDLINE/PubMed, SCOPUS, and Cochrane library to identify randomized clinical trials investigating the impact of metformin on insulin, glucose, CRP, leptin, body mass indices (BMI), cholesterol, Ki-67, and Homeostatic Model Assessment for Insulin-Resistance (HOMA-IR). Effect sizes were expressed as weighted mean difference (WMD) and 95% confidence intervals (CI) using a random-effects models.

RESULTS

Nine studies providing 1,363 participants were included in the meta-analysis. Pooled results showed a significant reduction in insulin (WMD: - 0.99 U/ml, 95% CI - 1.66, - 0.33), glucose (WMD: - 1.78 ml/dl, 95% CI - 2.96, - 0.60), CRP (WMD: - 0.60 mg/l, 95% CI - 0.88, - 0.33), HOMA-IR (WMD: - 0.45, 95% CI - 0.77, - 0.11), leptin (WMD: - 2.44 ng/ml, 95% CI - 3.28, - 1.61), BMI (WMD: - 0.55 kg/m², 95% CI - 1.00, - 0.11), and Ki-67 (WMD: - 4.06, 95% CI - 7.59, - 0.54). Results of the subgroup analyses showed that insulin, glucose, and BMI decreased more significantly when the duration of administering metformin intervention was above 4 weeks. We did not observe non-linear changes in the dose-response relationship between metformin and biomarkers as outcomes.

CONCLUSIONS

Breast cancer patients receiving metformin as treatment for diabetes showed significant reduction in levels of insulin, fasting glucose, CRP, HOMA, leptin, BMI, and Ki-67.

Potential of memory T cells in bridging preoperative chemoradiation and immunotherapy in rectal cancer

The management of locally advanced rectal cancer has passed a long way of developments, where total mesorectal excision and preoperative radiotherapy are crucial to secure clinical outcome. These and other aspects of multidisciplinary strategies are in-depth summarized in the literature, while our mini-review pursues a different goal. From an ethical and medical standpoint, we witness a delayed implementation of novel therapies given the cost/time consuming process of organizing randomized trials that would bridge an already excellent local control in cT3-4 node-positive disease with long-term survival. This unfortunate separation of clinical research and medical care provides a strong motivation to repurpose known pharmaceuticals that suit for treatment intensification with a focus on distant control. In the framework of on-going phase II-III IG/IMRT-SIB trials, we came across an intriguing translational observation that the ratio of circulating (protumor) myeloid-derived suppressor cells to (antitumor) central memory CD8+ T cells is drastically increased, a possible mechanism of tumor immuno-escape and spread. This finding prompts that restoring the CD45RO memory T-cell pool could be a part of integrated adjuvant interventions. Therefore, the immunocorrective potentials of modified IL-2 and the anti-diabetic drug metformin are thoroughly discussed in the context of tumor immunobiology, mTOR pathways and revised Warburg effect.

Impact of metformin on gastric adenocarcinoma survival: A Belgian population based study

BACKGROUND

Preclinical studies have shown anticancer activities of metformin in gastric cancer and a recent epidemiological study showed a decrease in recurrence and mortality of gastric cancer in metformin users. This study aimed to assess the impact of metformin on gastric cancer survival in diabetic patients at a Belgian population level.

METHODS

We conducted an observational, population-based study by linking data of the Belgian Cancer Registry with medical claims data coming from the health insurance companies for patients diagnosed with stage I to III gastric adenocarcinoma between 2006 and 2012. Information on gastric cancer-specific deaths was retrieved from mortality records collected by regional governments. Time-dependent Cox regression models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CI) for overall survival (OS) and cancer-specific mortality (CSS).

RESULTS

In our population of 371 patients, a reduction in all-cause mortality was observed in metformin users (adjusted HR = 0.73, 95% CI: [0.52; 1.01], p = 0.06) but not for cancer specific mortality (adjusted HR = 0.86, 95% CI: [0.56; 1.33], p = 0.50). Pre-diagnosis exposure to metformin was associated with a significant improvement in OS (adjusted HR = 0.75, 95% CI: [0.57; 0.98], p = 0.04) that was not significant for CSS (adjusted HR = 0.89, 95% CI: [0.62; 1.28], p = 0.52). Moreover, no dose-response relationship between metformin use and either all-cause or cancer-specific mortality was observed.

CONCLUSION

In the first population based study of metformin use in gastric cancer adenocarcinoma patients with previous diabetes, our findings suggest that metformin use might improve overall mortality. However, no such association was found for cancer-specific survival. Additional studies in other populations are required.

Caloric restriction - A promising anti-cancer approach: From molecular mechanisms to clinical trials

Cancer is the second leading cause of death worldwide and the morbidity is growing in developed countries. According to WHO, >14 million people per year are diagnosed with cancer and about 8 million die. Anti-cancer strategy includes chemo-, immune- and radiotherapy or their combination. Unfortunately, these widely used strategies often have insufficient efficacy and significant toxic effects on healthy cells. Consequently, the improvement of treatment approaches is an important goal. One of promising schemes to enhance the effect of therapy is the restriction of calorie intake or some nutrients. The combination of caloric restriction or its chemical mimetics along with anti-cancer drugs may suppress growth of tumor cells and enhance death of cancer cells. That will allow the dose of therapeutic drugs to be decreased and their toxic effects to be reduced. Here the possibility of using this combinatory therapy as well as the molecular mechanisms underlying this approach will be discussed.

Metabolic Dysfunction, Obesity, and Survival Among Patients With Early-Stage Colorectal Cancer

PURPOSE

The effects of obesity and metabolic dysregulation on cancer survival are inconsistent. To identify high-risk subgroups of obese patients and to examine the joint association of metabolic syndrome (MetSyn) in combination with obesity, we categorized patients with early-stage (I to III) colorectal cancer (CRC) into four metabolic categories defined by the presence of MetSyn and/or obesity and examined associations with survival.

METHODS

We studied 2,446 patients diagnosed from 2006 to 2011 at Kaiser Permanente. We assumed MetSyn if patients had three or more of five components present at diagnosis: fasting glucose > 100 mg/dL or diabetes; elevated blood pressure (systolic ≥ 130 mm Hg, diastolic ≥ 85 mm Hg, or antihypertensives); HDL cholesterol < 40 mg/dL (men) or < 50 mg/dL (women); triglycerides ≥ 150 mg/dL or antilipids; and/or highest sex-specific quartile of visceral fat by computed tomography scan (in lieu of waist circumference). We then classified participants according to the presence (or absence) of MetSyn and obesity (BMI < 30 or ≥ 30 kg/m²) and assessed associations with overall and CRC-related survival using Cox proportional hazards models adjusted for demographic, tumor, and treatment factors and muscle mass at diagnosis.

RESULTS

Over a median follow-up of 6 years, 601 patients died, 325 as a result of CRC. Mean (SD) age was 64 (11) years. Compared with the reference of nonobese patients without MetSyn (n = 1,225), for overall survival the hazard ratios (HR) and 95% CIs were 1.45 (1.12 to 1.82) for obese patients with MetSyn (n = 480); 1.09 (0.83 to 1.44) for the nonobese with MetSyn (n = 417), and 1.00 (0.80 to 1.26) for obese patients without MetSyn (n = 324). Obesity with MetSyn also predicted CRC-related survival: 1.49 (1.09 to 2.02). The hazard of death increased with the number of MetSyn components present, independent of obesity.

CONCLUSION

Patients with early-stage CRC with obesity and MetSyn have worse survival, overall and CRC related.

Metformin may protect nondiabetic breast cancer women from metastasis

Metformin, a widely prescribed oral hypoglycemic agent, has recently received a big interest because of its potential antitumorigenic effects in different cancer types. The present study investigated the impact of adding metformin to breast cancer adjuvant therapy in nondiabetic women on, insulin like growth factor-1 (IGF-1), IGF binding protein-3 (IGFBP-3), insulin, fasting blood glucose (FBG), the molar ratio of IGF-1 to IGFBP-3, homeostatic model assessment of insulin resistance (HOMA-IR) and metastasis. 102 women with newly diagnosed breast cancer were divided into 2 main groups, a control group and a metformin group. All women were treated with adjuvant therapy, according to the protocols of Ministry of Health and Population and National Cancer Institute, Egypt. Moreover, the women in the metformin group received 850 mg of metformin twice daily. Blood samples were collected at baseline, after chemotherapy (CT), after 6 months of hormonal therapy (6-HT) and 12 months of hormonal therapy (12-HT) for analysis of serum IGF-1, IGFBP-3, insulin, FBG and cancer antigen 15-3 (CA15-3). Metformin resulted in a significant reduction of IGF-1, IGF-1: IGFBP-3 molar ratio, insulin, FBG and HOMA-IR. On the other hand, metformin caused a significant increase of IGFBP-3. Moreover, metformin significantly decreased the numbers of metastatic cases after 6-HT. Metformin may have potential antitumor and antimetastatic effects that need further clinical investigations. This may be attributed to either the significant increase of the apoptotic inducer IGFBP-3 or/and the significant reduction of mitogenic insulin, IGF-1, free bioactive IGF-1, FBG and HOMA-IR.