Metformin use and survival outcomes in endometrial cancer: a systematic review and meta-analysis

Associations of metformin therapy treatment with endometrial cancer risk and prognosis: A systematic review and meta-analysis

BACKGROUND

Several abstract studies have demonstrated that metformin may be beneficial for preventing and treating endometrial cancer (EC), while the results have been inconsistent and inconclusive. This systematic review and meta-analysis aimed to investigate the association between metformin use and the incidence and mortality of endometrial cancer in diabetic patients.

METHODS

A systematic literature search was performed in Pubmed, EMBASE, Web of Science, Cochrane Library, SinoMed, CNKI, Wanfang Data, and VIP from inception to November 2022. The outcome measures were hazard ratios (HRs) comparing the EC incidence and mortality in patients with type 2 diabetes mellitus (T2DM) on metformin and non-metformin. A random or fixed-effects model was applied for data analysis, and subgroup analysis was performed to look for factors of heterogeneity. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) assessed the evidence's certainty.

RESULTS

Eleven studies reported data on EC incidence. The pooled results suggested that the use of metformin was associated with a significantly higher incidence of EC (HR = 1.17, 95% CI 1.09-1.26, P < 0.0001). Further, seventeen studies were included for survival analysis. The pooled data showed that metformin could significantly decrease all-cause mortality (HR = 0.62, 95% CI 0.52-0.74, P < 0.00001) and endometrial cancer-specific mortality (HR = 0.95, 95% CI 0.90, 1.00, P = 0.03). Finally, we noted that metformin was associated with significantly improving the progression-free survival (PFS) of EC patients with T2DM (HR = 0.55, 95% CI 0.44, 0.68, P < 0.00001).

CONCLUSIONS

This meta-analysis did not prove that metformin was beneficial for preventing EC. However, metformin could reduce their mortality risk and prolong the progression-free survival time of EC patients with T2DM.

Impact of Type 2 Diabetes Mellitus on Endometrial Cancer Survival: A Prospective Database Analysis

Purpose

Type 2 diabetes mellitus (T2DM) is an established risk factor for endometrial cancer but its impact on endometrial cancer survival outcomes is unclear. The aim of this study was to investigate whether pre-existing T2DM impacts survival outcomes in endometrial cancer.

Patients and Methods

Women diagnosed with endometrial cancer were recruited to a single centre prospective cohort study. Relevant sociodemographic and clinico-pathological data were recorded at baseline. T2DM status was based on clinical and biochemical assessment, verified by general practitioner records and analysed in relation to overall, cancer-specific and recurrence-free survival using Kaplan-Meier estimation and multivariable Cox-regression.

Results

In total, 533 women with median age and BMI of 66 years (Interquartile range (IQR), 56, 73) and 32kg/m² (IQR 26, 39) respectively, were included in the analysis. The majority had low-grade (67.3%), early-stage (85.1% stage I/II), endometrial cancer of endometrioid histological phenotype (74.7%). A total of 107 (20.1%) had pre-existing T2DM. Women with T2DM had a two-fold increase in overall mortality (adjusted HR 2.07, 95%CI 1.21-3.55, p=0.008), cancer-specific mortality (adjusted HR 2.15, 95% CI 1.05-4.39, p=0.035) and recurrence rates (adjusted HR 2.22, 95% CI 1.08-4.56, p=0.030), compared to those without, in multivariable analyses.

Conclusion

T2DM confers an increased risk of death in endometrial cancer patients. Well-designed longitudinal studies with large sample sizes are now needed to confirm these findings.

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.

Clinical factors as prognostic variables among molecular subgroups of endometrial cancer

Background

Clinical factors may influence endometrial cancer survival outcomes. We examined the prognostic significance of age, body mass index (BMI), and type 2 diabetes among molecular subgroups of endometrial cancer.

Methods

This was a single institution retrospective study of patients who underwent surgery for endometrial carcinoma between January 2007 and December 2012. Tumors were classified into four molecular subgroups by immunohistochemistry of mismatch repair (MMR) proteins and p53, and sequencing of polymerase-ϵ (POLE). Overall, cancer-related, and non-cancer-related mortality were estimated using univariable and multivariable survival analyses.

Results

Age >65 years was associated with increased mortality rates in the whole cohort (n = 515) and in the “no specific molecular profile” (NSMP) (n = 218) and MMR deficient (MMR-D) (n = 191) subgroups during a median follow-up time of 81 months (range 1‒136). However, hazard ratios for cancer-related mortality were non-significant for NSMP and MMR-D. Diabetes was associated with increased overall and non-cancer-related mortality in the whole cohort and MMR-D subgroup. Overweight/obesity had no effect on outcomes in the whole cohort, but was associated with decreased overall and cancer-related mortality in the NSMP subgroup, and increased overall and non-cancer-related mortality in the MMR-D subgroup. Overweight/obesity effect on cancer-related mortality in the NSMP subgroup remained unchanged after controlling for confounders. High-risk uterine factors were more common, and estrogen and progesterone receptor expression less common in NSMP subtype cancers of normal-weight patients compared with overweight/obese patients. No clinical factors were associated with outcomes in p53 aberrant (n = 69) and POLE mutant (n = 37) subgroups. No cancer-related deaths occurred in the POLE mutant subgroup.

Conclusions

The prognostic effects of age, BMI, and type 2 diabetes do not appear to be uniform for the molecular subgroups of endometrial cancer. Our data support further evaluation of BMI combined with genomics-based risk-assessment.

Insulin Resistance and Endometrial Cancer: Emerging Role for microRNA

Endometrial cancer (EC) remains one of the most common cancers of the female reproductive system. Epidemiological and clinical data implicate insulin resistance (IR) and its accompanying hyperinsulinemia as key factors in the development of EC. MicroRNAs (miRNAs) are short molecules of non-coding endogenous RNA that function as post-transcriptional regulators. Accumulating evidence has shown that the miRNA expression pattern is also likely to be associated with EC risk factors. The aim of this work was the verification of the relationships between IR, EC, and miRNA, and, as based on the literature data, elucidation of miRNA's potential utility for EC prevention in IR patients. The pathways affected in IR relate to the insulin receptors, insulin-like growth factors and their receptors, insulin-like growth factor binding proteins, sex hormone-binding globulin, and estrogens. Herein, we present and discuss arguments for miRNAs as a plausible molecular link between IR and EC development. Specifically, our careful literature search indicated that dysregulation of at least 13 miRNAs has been ascribed to both conditions. We conclude that there is a reasonable possibility for miRNAs to become a predictive factor of future EC in IR patients.

Statin and Cancer Mortality and Survival: An Umbrella Systematic Review and Meta-Analysis

The aim of this study is to provide an overview and understand the strength of evidence and the extent of potential biases and the validity of claimed associations between the use of statins and cancer mortality or survival. We performed a comprehensive umbrella review of meta-analyses and systematically appraised the relevant meta-analyses of observational studies on the associations between statin use and cancer mortality or survival in various kinds of cancer. We searched the PubMed database and screened the reference list of relevant articles. We obtained the summary effect, 95% confidence interval, heterogeneity, and also examined small study effects and 95% prediction intervals for effect sizes, and the level of evidence was determined from the criteria. Regarding cancer mortality, statin use showed convincing evidence for an association with a reduced cancer-specific mortality rate for colorectal cancer. Four associations with reduced all-cause mortality (for breast cancer, colorectal cancer, endocrine-related gynecological cancer, and ovarian cancer) had a suggestive evidence. Moreover, analyses in nine cancers showed a weak level of evidence, while the remaining 15 did not indicate significant changes in either direction. Although there was a preventive effect of statin on cancer mortality in some cancer types, the evidence supporting the use of statins to reduce cancer mortality or survival was low.

Metformin Promotes Anti-tumor Biomarkers in Human Endometrial Cancer Cells

Metformin (MET) is increasingly implicated in reducing the incidence of multiple cancer types in patients with diabetes. However, similar effects of MET in non-diabetic women with endometrial cancer (EC) remain unknown. In a pilot study, obese non-diabetic women diagnosed with type 1, grade 1/2 EC, and consenting to participate were randomly assigned to receive MET or no MET (control (CON)) during the pre-surgical window between diagnosis and hysterectomy. Endometrial tumors obtained at surgery (MET, n = 4; CON, n = 4) were analyzed for proliferation (Ki67), apoptosis (TUNEL), and nuclear expression of ERα, PGR, PTEN, and KLF9 proteins in tumor glandular epithelial (GE) and stromal (ST) cells. The percentages of immunopositive cells for PGR and for KLF9 in GE and for PTEN in ST were higher while those for ERα in GE but not ST were lower, in tumors of MET vs. CON patients. The numbers of Ki67- and TUNEL-positive cells in tumor GE and ST did not differ between groups. In human Ishikawa endometrial cancer cells, MET treatment (60 μM) decreased cell numbers and elicited distinct temporal changes in ESR1, KLF9, PGR, PGR-B, KLF4, DKK1, and other tumor biomarker mRNA levels. In the context of reduced KLF9 expression (by siRNA targeting), MET rapidly amplified PGR, PGR-B, and KLF4 transcript levels. Our findings suggest that MET acts directly in EC cells to modify steroid receptor expression and signaling network and may constitute a preventative strategy against EC in high-risk non-diabetic women.

Productive Cross-Talk with the Microenvironment: A Critical Step in Ovarian Cancer Metastasis

Most ovarian cancer patients present with disseminated disease at the time of their diagnosis, which is one of the main reasons for their poor prognosis. Metastasis is a multi-step process and a clear understanding of the mechanism of regulation of these steps remains elusive. Productive reciprocal interactions between the metastasizing ovarian cancer cells and the microenvironment of the metastatic site or the tumor microenvironment play an important role in the successful establishment of metastasis. Much progress has been made in the recent past in our understanding of such interactions and the role of the cellular and acellular components of the microenvironment in establishing the metastatic tumors. This review will outline the role of the microenvironmental components of the ovarian cancer metastatic niche and their role in helping establish the metastatic tumors. Special emphasis will be given to the mesothelial cells, which are the first cells encountered by the cancer cells at the site of metastasis.

Inhibition of midkine by metformin can contribute to its anticancer effects in malignancies: A proposal mechanism of action of metformin in context of endometrial cancer prevention and therapy

Metformin, a drug widely used in the treatment of type II diabetes mellitus (T2DM), has been the focus of interest as a potential therapeutic agent for certain types of malignancies, including gynaecological cancers [i.e. endometrial cancer (EC)]. Although the exact mechanism behind the potential anticancer activity of metformin is still not completely understood, certain studies have suggested that different effects on cell functions, such as inhibition of cell migration, apoptosis and tumor cell proliferation, are involved in its preventive and therapeutic effects in certain types of malignancies, including EC. In contrast, midkine (MK), a heparin-binding growth factor and cytokine, which induces carcinogenesis and chemoresistance, promotes the development and progression of many malignant tumours by increasing diverse cell functions such as cell proliferation, cell survival and antiapoptotic activities via mainly the activation of phosphatidyl inositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways. The same pathways are also subject to certain therapeutic effects of metformin, although this cytokine and this drug have some different mechanism of action pathways as well. Taken together, MK and metformin appear to have opposite effects in various biological processes such as apoptosis, cell proliferation, cell survival, cell migration, and angiogenesis. On the other hand, MK activates PI3K and MAPK cell signal pathways, whereas metformin inhibits these two pathways. It seems likely that almost all the pathways and cell functions, which play important roles in malignancies, are inhibited by metformin and activated by MK. Given the opposite relationship between the actions of metformin and MK, we hypothesize that metformin may act like a novel MK inhibitor in some malignancies. We also discuss the possible relationship between metformin and MK in the context of EC, the most common gynecological cancer worldwide, which incidence is rising rapidly, in parallel with the increase in obesity, T2DM and insulin resistance. In this respect, the therapeutic use of metformin may improve the survival of EC or other cancers, via inhibiting or overcoming the unwanted effects of MK in carcinogenesis.

Cancer cell specific inhibition of Wnt/β-catenin signaling by forced intracellular acidification

Use of the diabetes type II drug Metformin is associated with a moderately lowered risk of cancer incidence in numerous tumor entities. Studying the molecular changes associated with the tumor-suppressive action of Metformin we found that the oncogene SOX4, which is upregulated in solid tumors and associated with poor prognosis, was induced by Wnt/β-catenin signaling and blocked by Metformin. Wnt signaling inhibition by Metformin was surprisingly specific for cancer cells. Unraveling the underlying specificity, we identified Metformin and other Mitochondrial Complex I (MCI) inhibitors as inducers of intracellular acidification in cancer cells. We demonstrated that acidification triggers the unfolded protein response to induce the global transcriptional repressor DDIT3, known to block Wnt signaling. Moreover, our results suggest that intracellular acidification universally inhibits Wnt signaling. Based on these findings, we combined MCI inhibitors with H⁺ ionophores, to escalate cancer cells into intracellular hyper-acidification and ATP depletion. This treatment lowered intracellular pH both in vitro and in a mouse xenograft tumor model, depleted cellular ATP, blocked Wnt signaling, downregulated SOX4, and strongly decreased stemness and viability of cancer cells. Importantly, the inhibition of Wnt signaling occurred downstream of β-catenin, encouraging applications in treatment of cancers caused by APC and β-catenin mutations.