Metformin usage and the risk of colorectal cancer: a national cohort study

Harnessing Oxylipins and Inflammation Modulation for Prevention and Treatment of Colorectal Cancer

Colorectal cancer (CRC) is one of the most prevalent cancers worldwide, ranking as the third most malignant. The incidence of CRC has been increasing with time, and it is reported that Westernized diet and lifestyle play a significant role in its higher incidence and rapid progression. The intake of high amounts of omega-6 (n - 6) PUFAs and low levels of omega-3 (n - 3) PUFAs has an important role in chronic inflammation and cancer progression, which could be associated with the increase in CRC prevalence. Oxylipins generated from PUFAs are bioactive lipid mediators and have various functions, especially in inflammation and proliferation. Carcinogenesis is often a consequence of chronic inflammation, and evidence has shown the particular involvement of n - 6 PUFA arachidonic acid-derived oxylipins in CRC, which is further described in this review. A deeper understanding of the role and metabolism of PUFAs by their modifying enzymes, their pathways, and the corresponding oxylipins may allow us to identify new approaches to employ oxylipin-associated immunomodulation to enhance immunotherapy in cancer. This paper summarizes oxylipins identified in the context of the initiation, development, and metastasis of CRC. We further explore CRC chemo-prevention strategies that involve oxylipins as potential therapeutics.

Is Metformin Associated with a Lower Prevalence of Polyps, Adenomas, and Colorectal Carcinoma in Patients with Diabetes Mellitus?

PURPOSE

Recent studies suggested a protective role of metformin in the development of colorectal cancer (CRC) and its precursors. We aimed to investigate if metformin was associated with a lower prevalence and number of colorectal polyps in diabetic patients and also adenomas, high-risk adenomas, and CRC.

METHODS

Retrospective study on adult patients with diabetes mellitus followed in our hospital with a total colonoscopy between 2015 and 2019, treated with either metformin for > 5 years or other antidiabetic agent (control group). We assessed the number, size, and histopathology examination of proliferative lesions detected on colonoscopy.

RESULTS

We included 401 patients aged 69 ± 9 years, 57% males, divided into two groups: treated with metformin (n = 260) and without (n = 141). The number of polyps detected was significantly lower in patients under metformin (p = 0.014). There was a nonsignificant trend towards lower polyp detection rates in the metformin compared to the control group both in unadjusted analysis (50% vs 60%, p = 0.058) and multivariable adjusted analysis (odds ratio [OR] 0.68, 95% confidence interval [CI] 0.43-1.09, p = 0.111). In the latter, we identified male gender (OR 2.24, 95%CI 1.44-3.49, p < 0.001), age (OR 1.35 for every 10 years, 95%CI 1.07-1.71, p = 0.012), glycated hemoglobin value (OR 1.20 for every 1% increase, 95%CI 1.06-1.37, p = 0.005), and hypertension (OR 1.76, 95%CI 1.01-3.08, p = 0.046) as factors associated with a higher prevalence of polyps. We saw no statistically significant differences regarding adenoma (p = 0.231), high-risk adenoma (p = 0.810), and CRC (p = 0.705) diagnoses between groups.

CONCLUSION

In our study, metformin was associated with less colorectal polyps in diabetic patients compared to other treatment modalities. We observed a nonsignificant trend towards lower polyp detection rates in the metformin group both in unadjusted and adjusted analyses.

The role of anti-diabetic drugs in NAFLD. Have we found the Holy Grail? A narrative review

PURPOSE

Non-alcoholic fatty liver disease (NAFLD) has become a leading cause of liver disease, affecting 30% of the global population. NAFLD prevalence is particularly high in obese individuals and patients with type 2 diabetes mellitus (T2DM). NAFLD ranges from simple fat deposition in the liver to necroinflammation and fibrosis (non-alcoholic steatohepatitis (NASH)), NASH-cirrhosis, and/or hepatocellular carcinoma. Insulin resistance plays a key role in NAFLD pathogenesis, alongside dysregulation of adipocytes, mitochondrial dysfunction, genetic factors, and changes in gut microbiota. Since insulin resistance is also a major predisposing factor of T2DM, the administration of anti-diabetic drugs for the management of NAFLD seems reasonable.

METHODS

In this review we provide the NAFLD-associated mechanisms of action of some of the most widely used anti-diabetic drugs, namely metformin, pioglitazone, sodium-glucose transport protein-2 inhibitors (SGLT2i), glucagon-like peptide 1 receptor analogs (GLP1 RAs), and dipeptyl-peptidase-4 inhibitors (DPP4i) and present available data regarding their use in patients with NAFLD, with and without T2DM.

RESULTS

Both metformin and DPP4i have shown rather contradictory results, while pioglitazone seems to benefit patients with NASH and is thus the only drug approved for NASH with concomitant significant liver fibrosis by all major liver societies. On the other hand, SGLT2i and GLP1 RAs seem to be beneficiary in patients with NAFLD, showing both remarkable results, with SGLT2i proving to be more efficient in the only head-to-head study so far.

CONCLUSION

In patients with NAFLD and diabetes, pioglitazone, GLP1 RAs, and SGLT2i seem to be logical treatment options. Larger studies are needed before these drugs can be recommended for non-diabetic individuals.

Colorectal Cancer Stem Cell Biomarkers: Biological Traits and Prognostic Insights

Due to self-renewal, differentiation, and limitless proliferation properties, Cancer Stem Cells (CSCs) increase the probability of tumor development. These cells are identified by using CSC markers, which are highly expressed proteins on the cell surface of CSCs. Recently, the therapeutic application of CSCs as novel biomarkers improved both the prognosis and diagnosis outcome of colorectal Cancer. In the present review, we focused on a specific panel of colorectal CSC markers, including LGR5, ALDH, CD166, CD133, and CD44, which offers a targeted and comprehensive analysis of their functions. The selection criteria for these markers cancer were based on their established significance in Colorectal Cancer (CRC) pathogenesis and clinical outcomes, providing novel insights into the CSC biology of CRC. Through this approach, we aim to elevate understanding and stimulate further research for developing effective diagnostic and therapeutic strategies in CRC.

Evaluating Metformin Strategies for Cancer Prevention: A Target Trial Emulation Using Electronic Health Records

BACKGROUND

Metformin users appear to have a substantially lower risk of cancer than nonusers in many observational studies. These inverse associations may be explained by common flaws in observational analyses that can be avoided by explicitly emulating a target trial.

METHODS

We emulated target trials of metformin therapy and cancer risk using population-based linked electronic health records from the UK (2009-2016). We included individuals with diabetes, no history of cancer, no recent prescription for metformin or other glucose-lowering medication, and hemoglobin A1c (HbA1c) <64 mmol/mol (<8.0%). Outcomes included total cancer and 4 site-specific cancers (breast, colorectal, lung, and prostate). We estimated risks using pooled logistic regression with adjustment for risk factors via inverse-probability weighting. We emulated a second target trial among individuals regardless of diabetes status. We compared our estimates with those obtained using previously applied analytic approaches.

RESULTS

Among individuals with diabetes, the estimated 6-year risk differences (metformin - no metformin) were -0.2% (95% CI = -1.6%, 1.3%) in the intention-to-treat analysis and 0.0% (95% CI = -2.1%, 2.3%) in the per-protocol analysis. The corresponding estimates for all site-specific cancers were close to zero. Among individuals regardless of diabetes status, these estimates were also close to zero and more precise. By contrast, previous analytic approaches yielded estimates that appeared strongly protective.

CONCLUSIONS

Our findings are consistent with the hypothesis that metformin therapy does not meaningfully influence cancer incidence. The findings highlight the importance of explicitly emulating a target trial to reduce bias in the effect estimates derived from observational analyses.

Efficacy and safety of metformin in combination with chemotherapy in cancer patients without diabetes: systematic review and meta-analysis

Background

The results of a meta-analysis of retrospective studies suggest that the use of metformin in cancer patients may prolong progression-free disease survival and overall survival. However, the studies included in the meta-analysis did not strictly distinguish between patients with or without type 2 diabetes mellitus. Therefore, further studies are needed to assess whether the use of adjuvant chemotherapy with metformin in cancer patients without diabetes improves prognosis.

Method

Systematic searches of Embase, Pubmed, and The Cochrane library were performed for the subject terms metformin and neoplasm and for free words. Data related to PFS, OS were extracted according to inclusion exclusion criteria. The data were combined and meta-analysis was performed using Review Manager 5.4 to confirm the efficacy and safety of metformin administration.

Results

There were 3228 publications retrieved from the database and a total of 13 publications with 955 patients were included in the meta-analysis after screening. All included studies were randomised controlled trials. Metformin combined with adjuvant chemotherapy did not improve progression-free survival (HR=1,95CI 0.79-1.25), overall survival (HR=0.91,95% CI 0.69-1.20) and did not improve objective disease response rates in patients. There was no significant difference in grade 3-4 adverse reactions compared to placebo.

Conclusion

In this meta-analysis of randomised controlled trial studies, we found that chemotherapy in combination with metformin in cancer patients without diabetes did not prolong progression-free survival and overall survival and improved disease control in patients, although there was no significant difference in terms of safety. More high-quality randomised controlled trials are needed in the future to confirm the in vivo anti-tumour activity and survival benefit of metformin.

Effects of Metformin on Risk and Prognosis of Biliary Tract Cancer: A Systematic Review and Meta-Analysis

Background and Objectives: Metformin has been found to potentially reduce the risk and improve the prognosis of a variety of tumors, but these findings remain controversial in biliary tract cancer (BTC). Therefore, this systematic review and meta-analysis was conducted to investigate the association between metformin and BTC. Materials and Methods: Two independent researchers comprehensively searched PubMed, Embase, the Cochrane Library, and Web of Science for eligible studies published from their inception to 31 March 2022. Comparisons of risk, overall survival (OS), and disease-free survival (DFS) for patients with BTC were selected as the endpoints of interest and pooled by random or fixed-effects models. Results: Eleven studies with a total of 24,788,738 participants were eligible for this analysis. The overall pooled effects showed no significant differences in biliary tract cancer risk (hazard ratio (HR) = 0.82, 95% confidence interval (CI): 0.50-1.35, p = 0.436), OS (HR = 0.88, 95% CI: 0.74-1.04, p = 0.135), or DFS (HR = 1.03, 95% CI: 0.79-1.34, p = 0.829) between metformin users and non-users. When restricting participants to those with diabetes, a similar negative result was found, demonstrating that metformin use was not significantly associated with a lower risk of developing BTC compared with a lack of metformin use (HR = 0.65, 95% CI: 0.39-1.07, p = 0.089); notably, the included studies exhibited significant heterogeneity in the selection of participants and the definition of metformin users. Conclusions: Metformin may not be able to reduce the risk of BTC and improve prognosis in certain populations. Based on the limited quantity and quality of the included studies, the present results should be interpreted within their limitations, and further studies are warranted to determine the optimal timing, dose, duration, and scenario of metformin administration.

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.

Metformin Mitigated Obesity-Driven Cancer Aggressiveness in Tumor-Bearing Mice

Metformin may offer benefits to certain cancer populations experiencing metabolic abnormalities. To extend the anticancer studies of metformin, a tumor model was established through the implantation of murine Lewis Lung Carcinoma (LLC) cells to Normal Diet (ND)-fed and High-Fat Diet (HFD)-fed C57BL/6 mice. The HFD-fed mice displayed metabolic and pro-inflammatory alterations together with accompanying aggressive tumor growth. Metformin mitigated tumor growth in HFD-fed mice, paralleled by reductions in circulating glucose, insulin, soluble P-selectin, TGF-β1 and High Mobility Group Box-1 (HMGB1), as well as tumor expression of cell proliferation, aerobic glycolysis, glutaminolysis, platelets and neutrophils molecules. The suppressive effects of metformin on cell proliferation, migration and oncogenic signaling molecules were confirmed in cell study. Moreover, tumor-bearing HFD-fed mice had higher contents of circulating and tumor immunopositivity of Neutrophil Extracellular Traps (NETs)-associated molecules, with a suppressive effect from metformin. Data taken from neutrophil studies confirmed the inhibitory effect that metformin has on NET formation induced by HMGB1. Furthermore, HMGB1 was identified as a promoting molecule to boost the transition process towards NETs. The current study shows that metabolic, pro-inflammatory and NET alterations appear to play roles in the obesity-driven aggressiveness of cancer, while also representing candidate targets for anticancer potential of metformin.

Metformin use is not associated with colorectal cancer incidence in type-2 diabetes patients: evidence from methods that avoid immortal time bias

PURPOSE

Immortal time bias (ITB) continues to distort many observational studies on metformin use and cancer risk. Our objective was to employ three statistical methods proven to avoid ITB and compare their results to that of a naïve time-fixed analysis in order to provide further evidence of metformin's association, or none thereof, with colorectal cancer (CRC) incidence.

METHODS

A total of 41,533 Korean subjects with newly diagnosed type-2 diabetes in 2005-2015 were selected from a prospectively maintained cohort (median follow-up of 6.3 years). Time-to-CRC incidence was regressed upon metformin use (yes/no, average prescription days/year) using time-dependent Cox, landmark, nested case-control, and time-fixed Cox analyses. Other CRC risk factors were included to adjust for possible confounding.

RESULTS

Neither metformin ever-use nor average metformin prescription days/year was associated with incident CRC hazard in time-dependent Cox, landmark, and nested case-control analyses with HR (95% CI) of 0.88 (0.68-1.13), 0.86 (0.65-1.12), and 1.10 (0.86-1.40) for metformin ever-use, and 0.97 (0.90-1.04), 0.95 (0.88-1.04), and 1.02 (0.95-1.10) for average metformin prescription days/year, respectively. In contrast, time-fixed Cox regression showed a falsely exaggerated protective effect of metformin on CRC incidence.

CONCLUSION

The association between metformin use and subsequent CRC incidence was statistically nonsignificant after accounting for time-related biases such as ITB. Previous studies that avoided these biases and meta-analyses of RCTs on metformin and cancer incidence were in agreement with our results. A definitive, large-scale RCT is needed to clarify this topic, and future observational studies should be explicit in avoiding ITB and other time-related biases.

Transforming growth factor-beta (TGF-β) in prostate cancer: A dual function mediator?

Transforming growth factor-beta (TGF-β) is a member of a family of secreted cytokines with vital biological functions in cells. The abnormal expression of TGF-β signaling is a common finding in pathological conditions, particularly cancer. Prostate cancer (PCa) is one of the leading causes of death among men. Several genetic and epigenetic alterations can result in PCa development, and govern its progression. The present review attempts to shed some light on the role of TGF-β signaling in PCa. TGF-β signaling can either stimulate or inhibit proliferation and viability of PCa cells, depending on the context. The metastasis of PCa cells is increased by TGF-β signaling via induction of EMT and MMPs. Furthermore, TGF-β signaling can induce drug resistance of PCa cells, and can lead to immune evasion via reducing the anti-tumor activity of cytotoxic T cells and stimulating regulatory T cells. Upstream mediators such as microRNAs and lncRNAs, can regulate TGF-β signaling in PCa. Furthermore, some pharmacological compounds such as thymoquinone and valproic acid can suppress TGF-β signaling for PCa therapy. TGF-β over-expression is associated with poor prognosis in PCa patients. Furthermore, TGF-β up-regulation before prostatectomy is associated with recurrence of PCa. Overall, current review discusses role of TGF-β signaling in proliferation, metastasis and therapy response of PCa cells and in order to improve knowledge towards its regulation, upstream mediators of TGF-β such as non-coding RNAs are described. Finally, TGF-β regulation and its clinical application are discussed.

Type 2 Diabetes Mellitus and Cancer: Epidemiology, Physiopathology and Prevention

Individuals with type 2 diabetes mellitus are at greater risk of developing cancer and of dying from it. Both diseases are age-related, contributing to the impact of population aging on the long-term sustainability of health care systems in European Union countries. The purpose of this narrative review was to describe, from epidemiological, pathophysiological and preventive perspectives, the links between type 2 diabetes mellitus and the most prevalent cancers in these patients. Multiple metabolic abnormalities that may occur in type 2 diabetes mellitus, particularly obesity, could explain the increased cancer risk. In addition, the effectiveness of drugs commonly used to treat type 2 diabetes mellitus (e.g., metformin and thiazolidinediones) has been broadly evaluated in cancer prevention. Thus, a better understanding of the links between type 2 diabetes mellitus and cancer will help to identify the contributing factors and the pathophysiological pathways and to design personalized preventive strategies. The final goal is to facilitate healthy aging and the prevention of cancer and other diseases related with type 2 diabetes mellitus, which are among the main sources of disability and death in the European Union and worldwide.

Effect of metformin use on the risk and prognosis of colorectal cancer in diabetes mellitus: a meta-analysis

BACKGROUND

Whether metformin is a protective factor of colorectal cancer (CRC) among CRC patients is still not entirely clear. Thus, we conducted this systemic review and meta-analysis to provide a comprehensive review of associations between metformin therapy and CRC risk or survival outcomes for clinical decisions.

METHODS

Articles published before July 2021 were searched in databases (PubMed and Web of Science). Odds ratio (OR)/risk ratio (RR) or hazard ratio (HR) and their confidence intervals (CIs) were computed using STATA 12.0 software. Q test and I2 were conducted to explore heterogeneities between studies.

RESULTS

The present meta-analysis showed that metformin use was associated with decreased risk and lower all-cause mortality of CRC in diabetes mellitus (DM) with random-effects models (risk: OR/RR = 0.71, 95% CI, 0.64-0.80, I2 = 89.3%, P < 0.001; all-cause mortality: HR = 0.72, 95% CI, 0.62-0.83, I2 = 60.1%, P = 0.014). In addition, the study showed that metformin use was associated with a lower CRC-specific mortality in DM in cohort studies with a fixed-effects model (HR = 0.80, 95% CI, 0.70-0.92, I2 = 34.7%, P = 0.190).

CONCLUSION

Overall, in this meta-analysis, we found that metformin may be a protective factor for CRC risk and prognosis in patients with DM. Further well-designed, large-scale clinical studies are needed to evaluate the accuracy of our findings and more preclinical experiments are needed to reveal the underlying mechanism of metformin.

Multifaceted Mechanisms of Action of Metformin Which Have Been Unraveled One after Another in the Long History

While there are various kinds of drugs for type 2 diabetes mellitus at present, in this review article, we focus on metformin which is an insulin sensitizer and is often used as a first-choice drug worldwide. Metformin mainly activates adenosine monophosphate-activated protein kinase (AMPK) in the liver which leads to suppression of fatty acid synthesis and gluconeogenesis. Metformin activates AMPK in skeletal muscle as well, which increases translocation of glucose transporter 4 to the cell membrane and thereby increases glucose uptake. Further, metformin suppresses glucagon signaling in the liver by suppressing adenylate cyclase which leads to suppression of gluconeogenesis. In addition, metformin reduces autophagy failure observed in pancreatic β-cells under diabetic conditions. Furthermore, it is known that metformin alters the gut microbiome and facilitates the transport of glucose from the circulation into excrement. It is also known that metformin reduces food intake and lowers body weight by increasing circulating levels of the peptide hormone growth/differentiation factor 15 (GDF15). Furthermore, much attention has been drawn to the fact that the frequency of various cancers is lower in subjects taking metformin. Metformin suppresses the mechanistic target of rapamycin (mTOR) by activating AMPK in pre-neoplastic cells, which leads to suppression of cell growth and an increase in apoptosis in pre-neoplastic cells. It has been shown recently that metformin consumption potentially influences the mortality in patients with type 2 diabetes mellitus and coronavirus infectious disease (COVID-19). Taken together, metformin is an old drug, but multifaceted mechanisms of action of metformin have been unraveled one after another in its long history.