The Effect of Metformin vs Placebo on Sex Hormones in Canadian Cancer Trials Group MA.32

The impact of metformin on weight and metabolic parameters in patients with obesity: A systematic review and meta-analysis of randomized controlled trials

There are conflicting data on the weight-reducing potential of metformin (MTF) in nondiabetic patients with obesity. The purpose of this systematic review and meta-analysis was to evaluate the effect of MTF on weight and cardiometabolic parameters in adults with overweight/obesity with or without nonalcoholic fatty liver disease (NAFLD) (CRD42018085512). We included randomized controlled trials (RCTs) in adults without diabetes mellitus, with mean body mass index (BMI) ≥ 25 kg/m2, with or without NAFLD, comparing MTF to placebo/control, lifestyle modification (LSM) or a US Food and Drug Administration-approved anti-obesity drug, reporting on weight or metabolic parameters, and extending over at least 3 months. We conducted a systematic search in MEDLINE, EMBASE, PubMed and the Cochrane Library without time limitation (until March 2022). We screened and selected eligible articles, abstracted relevant data, and assessed the risk of bias. All steps were in duplicate and independently. We conducted a random-effects model meta-analysis using Review Manager version 5.3, with prespecified subgroup analyses in case of heterogeneity. We identified 2650 citations and included 49 trials (55 publications). Compared to placebo, MTF was associated with a significant reduction in BMI (mean difference [MD] -0.56 [-0.74, -0.37] kg/m2; p < 0.0001), at doses ranging from 500 to 2550 mg/day, and with a significant percentage change in BMI of -2.53% (-2.90, -2.17) at the dose 1700 mg/day. There was no interaction by baseline BMI, MTF dose or duration, nor presence or absence of NAFLD. There was no significant difference between MTF and LSM. Orlistat was more effective than MTF (at doses of 1000-1700 mg/day) in terms of weight loss, with an MD in BMI of -3.17 (-5.88; -0.47) kg/m2, favouring the former. Compared to placebo/control, MTF improved insulin parameters, while no effect was detected when compared to LSM. A few small trials showed heterogenous effects on liver parameters in patients with NAFLD treated with MTF compared to placebo/control. There was a large variability in the expression of outcome measures and RCTs were of low quality. In conclusion, MTF was associated with a modest weight reduction in obese nondiabetic patients. Further high-quality and better powered studies are needed to examine the impact of MTF in patients with insulin resistance and NAFLD.

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 clinical therapeutical approach for BPH treatment via inhibiting dysregulated steroid hormones-induced prostatic epithelial cells proliferation

The occurrence of benign prostate hyperplasia (BPH) was related to disrupted sex steroid hormones, and metformin (Met) had a clinical response to sex steroid hormone-related gynaecological disease. However, whether Met exerts an antiproliferative effect on BPH via sex steroid hormones remains unclear. Here, our clinical study showed that along with prostatic epithelial cell (PEC) proliferation, sex steroid hormones were dysregulated in the serum and prostate of BPH patients. As the major contributor to dysregulated sex steroid hormones, elevated dihydrotestosterone (DHT) had a significant positive relationship with the clinical characteristics of BPH patients. Activation of adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) by Met restored dysregulated sex steroid hormone homeostasis and exerted antiproliferative effects against DHT-induced proliferation by inhibiting the formation of androgen receptor (AR)-mediated Yes-associated protein (YAP1)-TEA domain transcription factor (TEAD4) heterodimers. Met's anti-proliferative effects were blocked by AMPK inhibitor or YAP1 overexpression in DHT-cultured BPH-1 cells. Our findings indicated that Met would be a promising clinical therapeutic approach for BPH by inhibiting dysregulated steroid hormone-induced PEC proliferation.

Current status and frontier tracking of clinical trials on Metformin for cancer treatment

PURPOSE

Metformin has been used clinically for more than six decades. Over time, numerous remarkable effects of metformin beyond the clinic have been discovered and discussed. Metformin has been shown to have a favorable impact on cancer therapy in addition to its clinically recognized hypoglycemic effect. However, the antitumor efficacy of metformin in humans has not been clearly demonstrated yet. Hence, a systematic analysis of the existing trials is necessary.

METHODS

Here, we retrieved clinical trials from the Clinical Trials.gov database to overview the clinical development of metformin for the treatment of cancer, analyze existing clinical results, and summarize some promising applications for specific cancer therapies.

RESULTS

The potential application of metformin contains three directions: Firstly, improvement of metabolic factors associated with treatment effects, such as insulin resistance and peripheral neuropathy. Secondly, in combination with immune checkpoint blockade effects. Finally, use it for the endocrine treatment of hormone-dependent cancers.

CONCLUSION

Although the outcomes of metformin as a repurposed agent in some trials have been unsatisfactory, it still has the potential to be used in select cancer therapy settings.

Are steroid hormones and autistic traits affected by metformin? First insights from a pilot

Background

Different lines of evidence imply that metformin could alter steroid hormone homeostasis and thereby improve social impairment. Here, we tried to correlate the impact of metformin treatment on alterations in steroid hormones and autism spectrum traits before versus after treatment with metformin.

Material & methods

Urine steroid hormones were measured using gas chromatography mass spectrometry in 12 male subjects (54.2 ± 9.1 years, 177.3 ± 4.1 cm, 80 ± 10.4 kg) and 7 female subjects (64.14 ± 18.0 years, 162.7 ± 4.1 cm, 76.1 ± 10.4 kg). Furthermore, a questionnaire on autism spectrum traits (Autism Spectrum Questionnaire]) was administered prior to and after metformin treatment.

Results

Overall, a decrease of steroid hormones were detected, which were most pronounced in the metabolites of corticosterone, deoxycortisol, cortisol, as well as androgens. These remained after Bonferroni correction (three classes: glucocorticoid, mineralocorticoid, androgens). No effect on autism spectrum traits (social skills, attention switching skills, attention to detail skills, communication skills, imagination skills), was identified pre versus post metformin treatment.

Discussion

The decreased steroid hormone levels are based on different mechanisms; one effect is likely via mitochondria, another effect via activated protein kinase prior to post treatment. The finding on autistic traits must be taxed as negative and do not directly provide an argument for using metformin in the treatment of autism.

Obesity promotes breast epithelium DNA damage in women carrying a germline mutation in BRCA1 or BRCA2

Obesity, defined as a body mass index (BMI) ≥ 30, is an established risk factor for breast cancer among women in the general population after menopause. Whether elevated BMI is a risk factor for women with a germline mutation in BRCA1 or BRCA2 is less clear because of inconsistent findings from epidemiological studies and a lack of mechanistic studies in this population. Here, we show that DNA damage in normal breast epithelia of women carrying a BRCA mutation is positively correlated with BMI and with biomarkers of metabolic dysfunction. In addition, RNA sequencing showed obesity-associated alterations to the breast adipose microenvironment of BRCA mutation carriers, including activation of estrogen biosynthesis, which affected neighboring breast epithelial cells. In breast tissue explants cultured from women carrying a BRCA mutation, we found that blockade of estrogen biosynthesis or estrogen receptor activity decreased DNA damage. Additional obesity-associated factors, including leptin and insulin, increased DNA damage in human BRCA heterozygous epithelial cells, and inhibiting the signaling of these factors with a leptin-neutralizing antibody or PI3K inhibitor, respectively, decreased DNA damage. Furthermore, we show that increased adiposity was associated with mammary gland DNA damage and increased penetrance of mammary tumors in Brca1+/- mice. Overall, our results provide mechanistic evidence in support of a link between elevated BMI and breast cancer development in BRCA mutation carriers. This suggests that maintaining a lower body weight or pharmacologically targeting estrogen or metabolic dysfunction may reduce the risk of breast cancer in this population.

Effect of metformin as an adjuvant therapy to letrozole on estradiol and other biomarkers involved in the pathogenesis of breast cancer in overweight and obese postmenopausal women: a pilot study

INTRODUCTION

Metformin may provide a therapeutic benefit in different types of malignancy.

PURPOSE

We aimed at evaluating the effect of metformin as an adjuvant therapy to letrozole on estradiol and other biomarkers involved in the pathogenesis of breast cancer in overweight and obese postmenopausal women.

METHODS

Seventy-five postmenopausal stages II-III breast cancer female patients were assessed for eligibility in an open-labeled parallel pilot study. Forty-five patients met the inclusion criteria and were assigned into three arms: the lean arm (n = 15) women who received letrozole 2.5 mg/day, the control arm (n = 15) overweight/obese women who received letrozole 2.5 mg/day, and the metformin arm (n = 15) overweight/obese women who received letrozole 2.5 mg/day plus metformin (2000 ± 500 mg/day). The intervention duration was 6 months. Blood samples were obtained at baseline and 6 months after intervention for the measurement of serum estradiol, leptin, osteocalcin levels, fasting blood glucose concentration, and serum insulin.

RESULTS

After the intervention and as compared to the control arm, the metformin arm showed a significantly lower ratio to the baseline (significant reduction) for estradiol (p = 0.0433), leptin (p < 0.0001), fasting blood glucose (p = 0.0128), insulin (p = 0.0360), osteocalcin serum levels (p < 0.0001), and the homeostatic model assessment of insulin resistance "HOMA-IR" value (p = 0.0145). There was a non-significant variation in the lactate ratio to the baseline among the three study arms (p = 0.5298).

CONCLUSION

Metformin may exert anti-cancer activity by decreasing the circulating estradiol, leptin, and insulin. Metformin might represent a safe and promising adjuvant therapy to letrozole in overweight/obese postmenopausal women with breast cancer.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05053841/Registered September 23, 2021 - Retrospectively.

Linking Physical Activity to Breast Cancer Risk via the Insulin/Insulin-like Growth Factor Signaling System, Part 2: The Effect of Insulin/Insulin-like Growth Factor Signaling on Breast Cancer Risk

Perturbation of the insulin/insulin-like growth factor (IGF) signaling system is often cited as a mechanism driving breast cancer risk. A systematic review identified prospective cohort studies and Mendelian randomization studies that examined the effects of insulin/IGF signaling (IGF, their binding proteins (IGFBP), and markers of insulin resistance] on breast cancer risk. Meta-analyses generated effect estimates; risk of bias was assessed and the Grading of Recommendations Assessment, Development and Evaluation system applied to evaluate the overall quality of the evidence. Four Mendelian randomization and 19 prospective cohort studies met our inclusion criteria. Meta-analysis of cohort studies confirmed that higher IGF-1 increased risk of breast cancer; this finding was supported by the Mendelian randomization studies. IGFBP-3 did not affect breast cancer. Meta analyses for connecting-peptide and fasting insulin showed small risk increases, but confidence intervals were wide and crossed the null. The quality of evidence obtained ranged from 'very low' to 'moderate'. There were insufficient studies to examine other markers of insulin/IGF signaling. These findings do not strongly support the biological plausibility of the second part of the physical activity-insulin/IGF signaling system-breast cancer pathway. Robust conclusions cannot be drawn due to the dearth of high quality studies. See related article by Swain et al., p. 2106.

The effects of exercise and diet on sex steroids in breast cancer survivors

Insufficient physical activity and obesity are associated with an increased risk of cancer recurrence and death in breast cancer survivors. Sex steroid hormones may mediate these associations. This study tested the hypothesis that exercise and diet, as compared to control, favorably change sex steroid hormones. This analysis of data from a subset of participants in a 2 × 2 factorial trial compares 269 postmenopausal breast cancer survivors who were insufficiently physically active and had overweight or obesity and were randomized to one of four treatment groups for 52 weeks: control, exercise alone, diet alone, or exercise plus diet. Secondary sex steroid hormone endpoints included estradiol, sex hormone-binding globulin (SHBG), and testosterone. Treatment effects were quantified using a mixed model for repeated measures. Compared to control, exercise alone did not significantly change estradiol (-1.9%; 95% CI: -12.6, 8.8), SHBG (2.4%; 95% CI: -9.9, 14.6), or testosterone (1.2%; 95% CI: -12.2, 14.5). Compared to control, diet alone did not significantly change estradiol (-7.8%; 95% CI: -17.6, 1.9), SHBG (8.2%; 95% CI: -4.2, 20.6), or testosterone (-0.8%; 95% CI: -13.6, 12.0). Compared to control, exercise plus diet did not significantly change estradiol (-6.3%; 95% CI: -16.3, 3.6), SHBG (8.8%; 95% CI: -4.0, 21.7), or testosterone (-5.3%; 95% CI: -18.0, 7.4). In postmenopausal breast cancer survivors who were insufficiently physically active and had overweight or obesity, randomization to exercise alone, diet alone, or exercise plus diet did not statistically significantly change sex steroid hormone concentrations at week 52.

Effect of Metformin vs Placebo on Invasive Disease-Free Survival in Patients With Breast Cancer: The MA.32 Randomized Clinical Trial

Importance

Metformin, a biguanide commonly used to treat type 2 diabetes, has been associated with potential beneficial effects across breast cancer subtypes in observational and preclinical studies.

Objective

To determine whether the administration of adjuvant metformin (vs placebo) to patients with breast cancer without diabetes improves outcomes.

Design, Setting, and Participants

MA.32, a phase 3 randomized, placebo-controlled, double-blind trial, conducted in Canada, Switzerland, US, and UK, enrolled 3649 patients with high-risk nonmetastatic breast cancer receiving standard therapy between August 2010 and March 2013, with follow-up to October 2020.

Interventions

Patients were randomized (stratified for hormone receptor [estrogen receptor and/or progesterone receptor {ER/PgR}] status, positive vs negative; body mass index, ≤30 vs >30; human epidermal growth factor receptor 2 [ERBB2, formerly HER2 or HER2/neu], positive vs negative; and any vs no chemotherapy) to 850 mg of oral metformin twice a day (n = 1824) or oral placebo twice a day (n = 1825) for 5 years.

Main Outcomes and Measures

The primary outcome was invasive disease-free survival in hormone receptor-positive breast cancer. Of the 8 secondary outcomes, overall survival, distant relapse-free survival, and breast cancer-free interval were analyzed.

Results

Of the 3649 randomized patients (mean age, 52.4 years; 3643 women [99.8%]), all (100%) were included in analyses. After a second interim analysis, futility was declared for patients who were ER/PgR-, so the primary analysis was conducted for 2533 patients who were ER/PgR+. The median duration of follow-up in the ER/PgR+ group was 96.2 months (range, 0.2-121 months). Invasive disease-free survival events occurred in 465 patients who were ER/PgR+. The incidence rates for invasive disease-free survival events were 2.78 per 100 patient-years in the metformin group vs 2.74 per 100 patient-years in the placebo group (hazard ratio [HR], 1.01; 95% CI, 0.84-1.21; P = .93), and the incidence rates for death were 1.46 per 100 patient-years in the metformin group vs 1.32 per 100 patient-years in the placebo group (HR, 1.10; 95% CI, 0.86-1.41; P = .47). Among patients who were ER/PgR-, followed up for a median of 94.1 months, incidence of invasive disease-free survival events was 3.58 vs 3.60 per 100 patient-years, respectively (HR, 1.01; 95% CI, 0.79-1.30; P = .92). None of the 3 secondary outcomes analyzed in the ER/PgR+ group had statistically significant differences. Grade 3 nonhematological toxic events occurred more frequently in patients taking metformin than in patients taking placebo (21.5% vs 17.5%, respectively, P = .003). The most common grade 3 or higher adverse events in the metformin vs placebo groups were hypertension (2.4% vs 1.9%), irregular menses (1.5% vs 1.4%), and diarrhea (1.9% vs 7.0%).

Conclusions and Relevance

Among patients with high-risk operable breast cancer without diabetes, the addition of metformin vs placebo to standard breast cancer treatment did not significantly improve invasive disease-free survival.

Trial Registration

ClinicalTrials.gov Identifier: NCT01101438.

A Clinical Perspective of the Multifaceted Mechanism of Metformin in Diabetes, Infections, Cognitive Dysfunction, and Cancer

In type 2 diabetes, ecological and lifecourse factors may interact with the host microbiota to influence expression of his/her genomes causing perturbation of interconnecting biological pathways with diverse clinical course. Metformin is a plant-based or plant-derived medicinal product used for the treatment of type 2 diabetes for over 60 years and is an essential drug listed by the World Health Organization. By reducing mitochondrial oxidative phosphorylation and adenosine triphosphate (ATP) production, metformin increased AMP (adenosine monophosphate)-activated protein kinase (AMPK) activity and altered cellular redox state with reduced glucagon activity, endogenous glucose production, lipogenesis, and protein synthesis. Metformin modulated immune response by directly reducing neutrophil to lymphocyte ratio and improving the phagocytic function of immune cells. By increasing the relative abundance of mucin-producing and short-chain-fatty-acid-producing gut microbes, metformin further improved the host inflammatory and metabolic milieu. Experimentally, metformin promoted apoptosis and reduced proliferation of cancer cells by reducing their oxygen consumption and modulating the microenvironment. Both clinical and mechanistic studies support the pluripotent effects of metformin on reducing cardiovascular–renal events, infection, cancer, cognitive dysfunction, and all-cause death in type 2 diabetes, making this low-cost medication a fundamental therapy for individualization of other glucose-lowering drugs in type 2 diabetes. Further research into the effects of metformin on cognitive function, infection and cancer, especially in people without diabetes, will provide new insights into the therapeutic value of metformin in our pursuit of prevention and treatment of ageing-related as well as acute and chronic diseases beyond diabetes.

Metformin: A Narrative Review of Its Potential Benefits for Cardiovascular Disease, Cancer and Dementia

The biguanide metformin has been used as first-line therapy in type 2 diabetes mellitus (T2DM) treatment for several decades. In addition to its glucose-lowering properties and its prevention of weight gain, the landmark UK Prospective Diabetes Study (UKPDS) demonstrated cardioprotective properties in obese T2DM patients. Coupled with a favorable side effect profile and low cost, metformin has become the cornerstone in the treatment of T2DM worldwide. In addition, metformin is increasingly being investigated for its potential anticancer and neuroprotective properties both in T2DM patients and non-diabetic individuals. In the meantime, new drugs with powerful cardioprotective properties have been introduced and compete with metformin for its place in the treatment of T2DM. In this review we will discuss actual insights in the various working mechanisms of metformin and the evidence for its beneficial effects on (the prevention of) cardiovascular disease, cancer and dementia. In addition to observational evidence, emphasis is placed on randomized trials and recent meta-analyses to obtain an up-to-date overview of the use of metformin in clinical practice.

Metformin and Breast Cancer: Where Are We Now?

Breast cancer is the most prevalent cancer and the leading cause of cancer-related death among women worldwide. Type 2 diabetes–associated metabolic traits such as hyperglycemia, hyperinsulinemia, inflammation, oxidative stress, and obesity are well-known risk factors for breast cancer. The insulin sensitizer metformin, one of the most prescribed oral antidiabetic drugs, has been suggested to function as an antitumoral agent, based on epidemiological and retrospective clinical data as well as preclinical studies showing an antiproliferative effect in cultured breast cancer cells and animal models. These benefits provided a strong rationale to study the effects of metformin in routine clinical care of breast cancer patients. However, the initial enthusiasm was tempered after disappointing results in randomized controlled trials, particularly in the metastatic setting. Here, we revisit the current state of the art of metformin mechanisms of action, critically review past and current metformin-based clinical trials, and briefly discuss future perspectives on how to incorporate metformin into the oncologist’s armamentarium for the prevention and treatment of breast cancer.

Metformin in the management of fibrocystic breast disease: a placebo-controlled randomized clinical trial

BACKGROUND AND PURPOSE

Fibrocystic disease (FCD) of the breast as a very common health problem in women has estrogen-dependent and proliferative features. No effective management strategy has been validated for this disorder, so far. The anti-hyperglycemic agent metformin has both anti-proliferative and estrogen-suppressing effects. Thus, we investigated metformin as a management strategy for FCD.

METHODS

The study was a double-blind placebo-controlled randomized clinical trial. Premenopausal women with FCD according to history, physical exam and ultrasound, who had measurable microcyst clusters on ultrasound (US) were entered the study. Oral placebo and metformin tablets (500 mg) were used twice daily by participants in the intervention and control groups. Size and number of microcyst clusters on US and the subjective pain score were recorded before and after the intervention.

RESULTS

154 participants were randomly allocated into two groups of 77 interventions and 77 controls. The decrease in size of the largest microcyst cluster in each patient and the mean decrease in number of microcyst clusters were not statistically significant (P = 0.310 and P = 0.637, respectively). However, those microcyst clusters which were ≥ 14 mm became significantly smaller after metformin use (P = 0.006). Additionally, in the subset of participants with pain at baseline, a larger proportion in the intervention group experienced at least 50% reduction in pain score (63.8% (30/47) in the intervention vs. 44.2% (19/43) in the placebo groups, P = 0.031).

CONCLUSION

Our study showed that metformin might be effective in the management of FCD. Further studies are proposed for confirmation of this subject.

Role of metformin and other metabolic drugs in the prevention and therapy of endocrine-related cancers

Metabolic syndrome is associated with chronic diseases, including type 2 diabetes, cardiovascular diseases, and cancer. This review summarizes the current evidence on the antitumor effects of some relevant drugs currently used to manage metabolic-related pathologies (i.e. insulin and its analogs, metformin, statins, etc.) in endocrine-related cancers including breast cancer, prostate cancer, pituitary cancer, ovarian cancer, and neuroendocrine neoplasms. Although current evidence does not provide a clear antitumor role of several of these drugs, metformin seems to be a promising chemopreventive and adjuvant agent in cancer management, modulating tumor cell metabolism and microenvironment, through both AMP-activated protein kinase-dependent and -independent mechanisms. Moreover, its combination with statins might represent a promising therapeutic strategy to tackle the progression of endocrine-related tumors. However, further studies are needed to endorse the clinical relevance of these drugs as adjuvants for cancer chemotherapy.

Metabolic pathways in obesity-related breast cancer

This Review focuses on the mechanistic evidence for a link between obesity, dysregulated cellular metabolism and breast cancer. Strong evidence now links obesity with the development of 13 different types of cancer, including oestrogen receptor-positive breast cancer in postmenopausal women. A number of local and systemic changes are hypothesized to support this relationship, including increased circulating levels of insulin and glucose as well as adipose tissue-derived oestrogens, adipokines and inflammatory mediators. Metabolic pathways of energy production and utilization are dysregulated in tumour cells and this dysregulation is a newly accepted hallmark of cancer. Dysregulated metabolism is also hypothesized to be a feature of non-neoplastic cells in the tumour microenvironment. Obesity-associated factors regulate metabolic pathways in both breast cancer cells and cells in the breast microenvironment, which provides a molecular link between obesity and breast cancer. Consequently, interventions that target these pathways might provide a benefit in postmenopausal women and individuals with obesity, a population at high risk of breast cancer.

Hyperinsulinemia in Obesity, Inflammation, and Cancer

The relative insufficiency of insulin secretion and/or insulin action causes diabetes. However, obesity and type 2 diabetes mellitus can be associated with an absolute increase in circulating insulin, a state known as hyperinsulinemia. Studies are beginning to elucidate the cause-effect relationships between hyperinsulinemia and numerous consequences of metabolic dysfunctions. Here, we review recent evidence demonstrating that hyperinsulinemia may play a role in inflammation, aging and development of cancers. In this review, we will focus on the consequences and mechanisms of excess insulin production and action, placing recent findings that have challenged dogma in the context of the existing body of literature. Where relevant, we elaborate on the role of specific signal transduction components in the actions of insulin and consequences of chronic hyperinsulinemia. By discussing the involvement of hyperinsulinemia in various metabolic and other chronic diseases, we may identify more effective therapeutics or lifestyle interventions for preventing or treating obesity, diabetes and cancer. We also seek to identify pertinent questions that are ripe for future investigation.

Hyperglycemia and Chemoresistance in Breast Cancer: From Cellular Mechanisms to Treatment Response

Female breast cancer is a complex, multifactorial disease. Studies have shown that hyperglycemia is one of the most important contributing factors to increasing the risk of breast cancer that also has a major impact on the efficacy of chemotherapy. At the cellular level, hyperglycemia can promote the proliferation, invasion, and migration of breast cancer cells and can also induce anti-apoptotic responses to enhance the chemoresistance of tumors via abnormal glucose metabolism. In this article, we focus on the latest progress in defining the mechanisms of chemotherapy resistance in hyperglycemic patients including the abnormal behaviors of cancer cells in the hyperglycemic microenvironment and the impact of abnormal glucose metabolism on key signaling pathways. To better understand the advantages and challenges of breast cancer treatments, we explore the causes of drug resistance in hyperglycemic patients that may help to better inform the development of effective treatments.