No reduced risk of overall, colorectal, lung, breast, and prostate cancer with metformin therapy in diabetic patients: database analyses from Germany and the UK

Effect of metformin on incidence, recurrence, and mortality in prostate cancer patients: integrating evidence from real-world studies

PURPOSE

Metformin has been suggested to reduce the risk of cancer. However, previous studies have been inconsistent regarding the relationship between metformin use and the risk of occurrence of prostate cancer (PCa). The purpose of this study was to assess the effect of metformin on clinical outcomes in patients with PCa in a meta-analysis and to explore the possible dose-response relationship.

METHODS

A systematic literature search was conducted in 10 electronic databases and 4 registries. The combined relative risks (RRs) were calculated using a random-effects model with 95% confidence interval (CIs) to assess the effect of metformin on the risk of PCa. Relevant subgroup analyses and sensitivity analyses were performed.

RESULTS

The across studies results show that metformin use associated with lower incidence of PCa (RR: 0.82, 95% CI: 0.74-0.91). Metformin use was also found to reduce PCa recurrence, but the results were not statistically significant (RR: 0.97, 95% CI: 0.81-1.15). Metformin use was not associated with PCa mortality (RR: 0.94, 95% CI: 0.81-1.09). The results of subgroup analyses indicated that the type of study was a cohort study and the population came from both Asia and Europe showed that taking metformin reduced the incidence of PCa. A linear correlation was found between the duration of metformin use and its protective effect.

CONCLUSIONS

This meta-analysis revealed an independent correlation between metformin use and reduced incidence of PCa. Metformin use was not associated with either PCa recurrence rate or mortality. Furthermore, the effect of metformin on PCa incidence was found to be related to duration.

Metformin and other anti-diabetic medication use and breast cancer incidence in the Nurses' Health Studies

We aimed to examine the association between the use of metformin and other anti-diabetic medications and breast cancer incidence within two large prospective cohort studies. We followed 185,181 women who participated in the Nurses' Health Study (NHS; 1994-2016) and the NHSII (1995-2017), with baseline corresponding to the date metformin was approved for type 2 diabetes (T2D) treatment in the US Information on T2D diagnosis, anti-diabetes medications, and other covariates was self-reported at baseline and repeatedly assessed by follow-up questionnaires every 2 years. Breast cancer cases were self-reported and confirmed by medical record review. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between medication use and breast cancer were estimated using Cox proportional hazards regression models, adjusting for breast cancer risk factors. During 3,324,881 person-years of follow-up, we ascertained 9,192 incident invasive breast cancer cases, of which 451 were among women with T2D. Compared with women without T2D (n = 169,263), neither metformin use (HR = 0.97; 95% CI = 0.81-1.15) nor other anti-diabetic medications use (HR = 1.11; 95% CI = 0.90-1.36) associated with significantly lower breast cancer incidence. Among women with T2D (n = 15,918), compared with metformin never users, metformin ever use was not significantly inversely associated with breast cancer (HR = 0.92; 95% CI = 0.74-1.15). Although we observed that past use of metformin was inversely associated with breast cancer in the T2D population (HR = 0.67; 95% CI = 0.48-0.94), current use (HR = 1.01; 95% CI = 0.80-1.27) and longer duration of metformin use were not associated with breast cancer (each 2-year interval: HR = 1.01; 95% CI = 0.95-1.07). Overall, metformin use was not associated with the risk of developing breast cancer among the overall cohort population or among women with T2D.

Association between gout and subsequent breast cancer: a retrospective cohort study including 67,598 primary care patients in Germany

PURPOSE

The aim of this retrospective cohort study was to analyze the cumulative incidence of breast cancer following gout and to investigate the association between gout and subsequent breast cancer in 67,598 primary care patients in Germany.

METHODS

This study included adult female patients (≥ 18 years) with an initial diagnosis of gout in 1284 general practices in Germany between January 2005 and December 2020. Individuals without gout were matched to gout patients using propensity score matching based on average yearly consultation frequency during the follow-up period, diabetes, obesity, chronic bronchitis/COPD diagnoses, and diuretic therapy. The 10-year cumulative incidence of breast cancer in the cohorts with and without gout was also studied using Kaplan-Meier curves, which were then compared using the log-rank test. Finally, a univariable Cox regression analysis was conducted to assess the association between gout and breast cancer.

RESULTS

After up to 10 years of follow-up, 4.5% of gout and 3.7% of non-gout patients were diagnosed with breast cancer. A Cox regression analysis revealed a significant association between gout and subsequent breast cancer in the total population (HR: 1.17; 95% CI: 1.05-1.31). In the age-stratified analyses, gout was only strongly associated with subsequent breast cancer in the age group ≤ 50 (HR: 1.58; 95% CI: 1.10-2.27), but the association was not significant in women over 50 years old.

CONCLUSION

Taken together, the findings of our study provide evidence for the association between gout and subsequent breast cancer diagnosis, particularly in the youngest age group.

Colorectal Cancer Chemoprevention: A Dream Coming True?

Colorectal cancer (CRC) is one of the deadliest forms of cancer worldwide. CRC development occurs mainly through the adenoma-carcinoma sequence, which can last decades, giving the opportunity for primary prevention and early detection. CRC prevention involves different approaches, ranging from fecal occult blood testing and colonoscopy screening to chemoprevention. In this review, we discuss the main findings gathered in the field of CRC chemoprevention, focusing on different target populations and on various precancerous lesions that can be used as efficacy evaluation endpoints for chemoprevention. The ideal chemopreventive agent should be well tolerated and easy to administer, with low side effects. Moreover, it should be readily available at a low cost. These properties are crucial because these compounds are meant to be used for a long time in populations with different CRC risk profiles. Several agents have been investigated so far, some of which are currently used in clinical practice. However, further investigation is needed to devise a comprehensive and effective chemoprevention strategy for CRC.

Prognostic value of metformin in cancers: An updated meta-analysis based on 80 cohort studies

BACKGROUND

Experiments have shown that metformin can inhibit cancer cell growth, but clinical observations have been inconsistent, so we pooled the currently available data to evaluate the impact of metformin on cancer survival and progression.

METHODS

PubMed, web of science, Embase, and Cochrane databases were searched. Pooled hazard ratios (HRs) were identified using a random-effects model to estimate the strength of the association between metformin and survival and progression in cancer patients.

RESULTS

We incorporated 80 articles published from all databases which satisfied the inclusion criterion. It showed that metformin was associated with better overall survival (hazard ratio [HR] = 0. 81; 95% confidence interval [CI]: [0.77-0.85]) and cancer-specific survival (HR = 0.79; 95% CI: [0.73-0.86]), and metformin was associated with progression-free survival (HR = 0.76; 95% CI: [0.66-0.87]). In patients with diabetes mellitus, the HR of overall survival was 0.79(95% CI: [0.75-0.83]), progression-free survival was 0.72(95% CI: [0.60-0.85]), and the cancer-specific survival was 0.76(95% CI: [0.68-0.86]). It was proposed that metformin can improve the prognosis of cancer patients with diabetes mellitus.

CONCLUSION

Based on cohort studies, metformin therapy has potential survival benefits for patients with malignancy, especially with the greatest benefits seen in breast cancer on overall survival, progression-free survival, and cancer-specific survival. And metformin also showed potential benefits in cancer-specific survival in colorectal and prostate cancer.

Association between anti-seizure medication and the risk of lower urinary tract infection in patients with epilepsy

PURPOSE

The aim of this retrospective study was to analyze the incidence of lower urinary tract infections (LUTI) and antibiotic prescriptions within 12 months after initial prescription of anti-seizure medication (ASM) between January and December 2020 (index date) and to investigate the association between a broad spectrum of ASMs and the risk of LUTI in patients with epilepsy.

METHODS

This retrospective cohort study included a total of 9186 adult patients (≥18 years) with an initial diagnosis of epilepsy and a prescription of an ASM treated in 1284 general practices in Germany between January 2010 and December 2020 (index date). Six frequently prescribed ASMs with at least 1000 available patients were analyzed. Patients treated with one of six ASMs were matched to each other by propensity scores based on sex, age, and secondary diagnoses. Cox regression models were used to analyze the association between the use of ASM and LUTI risk.

RESULTS

The cumulative LUTI incidence 12 months after the start of therapy was highest in patients treated with pregabalin (16.7%), followed by valproate (11.6%) and gabapentin (10.2%). A similar trend was observed for LUTI with antibiotic prescription (9.2% pregabalin, 6.8% valproate, 6.8% gabapentin). Conditional regression analyses revealed that pregabalin therapy was significantly positively associated with LUTI (HR: 1.76; 95% CI 1.29-2.39) and LUTI-based antibiotic prescription (HR: 2.16; 95% CI 1.43-3.27). Carbamazepine was associated with a significantly lower incidence of LUTI in women (HR: 0.47; 95% CI: 0.30-0.75), but not in men. No significant associations were observed for other ASMs.

CONCLUSION

The present study identifies a significant positive association between ASM and LUTI incidence and antibiotic prescriptions in patients with epilepsy treated with pregabalin, whereas a protective effect was found for carbamazepine in women only. No significant associations were observed for the four remaining ASMs.

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.

Metformin: Is it a drug for all reasons and diseases?

Metformin was first used to treat type 2 diabetes in the late 1950s and in 2022 remains the first-choice drug used daily by approximately 150 million people. An accumulation of positive pre-clinical and clinical data has stimulated interest in re-purposing metformin to treat a variety of diseases including COVID-19. In polycystic ovary syndrome metformin improves insulin sensitivity. In type 1 diabetes metformin may help reduce the insulin dose. Meta-analysis and data from pre-clinical and clinical studies link metformin to a reduction in the incidence of cancer. Clinical trials, including MILES (Metformin In Longevity Study), and TAME (Targeting Aging with Metformin), have been designed to determine if metformin can offset aging and extend lifespan. Pre-clinical and clinical data suggest that metformin, via suppression of pro-inflammatory pathways, protection of mitochondria and vascular function, and direct actions on neuronal stem cells, may protect against neurodegenerative diseases. Metformin has also been studied for its anti-bacterial, -viral, -malaria efficacy. Collectively, these data raise the question: Is metformin a drug for all diseases? It remains unclear as to whether all of these putative beneficial effects are secondary to its actions as an anti-hyperglycemic and insulin-sensitizing drug, or result from other cellular actions, including inhibition of mTOR (mammalian target for rapamycin), or direct anti-viral actions. Clarification is also sought as to whether data from ex vivo studies based on the use of high concentrations of metformin can be translated into clinical benefits, or whether they reflect a 'Paracelsus' effect. The environmental impact of metformin, a drug with no known metabolites, is another emerging issue that has been linked to endocrine disruption in fish, and extensive use in T2D has also raised concerns over effects on human reproduction. The objectives for this review are to: 1) evaluate the putative mechanism(s) of action of metformin; 2) analyze the controversial evidence for metformin's effectiveness in the treatment of diseases other than type 2 diabetes; 3) assess the reproducibility of the data, and finally 4) reach an informed conclusion as to whether metformin is a drug for all diseases and reasons. We conclude that the primary clinical benefits of metformin result from its insulin-sensitizing and antihyperglycaemic effects that secondarily contribute to a reduced risk of a number of diseases and thereby enhancing healthspan. However, benefits like improving vascular endothelial function that are independent of effects on glucose homeostasis add to metformin's therapeutic actions.

Metformin, Statin Use, and Female Colorectal Cancer: A Population-Based Cohort Study in Taiwan

In the last few years, the incidence of colorectal cancer (CRC) in women has gradually increased. However, epidemiological studies on the relationship between type II diabetes mellitus (T2DM) and female CRC and the effect of metformin or statins on female CRC are insufficient. To determine their association, we conducted a population-based cohort study on women in Taiwan. We collected data on a total of 396,521 women aged 40 to 64 years old from 1 January 2007 to 31 December 2009 from the National Health Insurance Research Database. We followed up on all participants in the cohort until the occurrence of CRC, the date for all death, or 31 December 2015. Full development of CRC was identified using the International Classification of Disease (ICD), 9th Revision, code 153. We estimated hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) using the Cox proportional hazards model. Both metformin (adjusted hazard ratio, aHR = 1.12; 95% CI: 0.934–1.335, p = 0.227) and statin (aHR = 1.03; 95% CI: 0.906–1.172, p = 0.645) use showed no association with female CRC in a multivariate analysis. The findings indicate that metformin and statin use showed no protective effect against female colorectal cancer (CRC). An additional randomized trial is necessary to investigate the effect of metformin and statin use in CRC prevention.

Association between antihypertensive medication and the risk of urinary tract infection (UTI) of outpatients: a retrospective cohort study

PURPOSE

The aim of this retrospective study was to investigate the impact of a broad spectrum of antihypertensive (AH) medications on urinary tract infections (UTI) of outpatients diagnosed in general practices in Germany.

METHODS

This study included a total of 367,960 patients aged ≥ 18 years newly a diagnosed with UTI in 1274 general practices in Germany between January 2010 and December 2019. The analysis was conducted for five groups representing five AH therapy classes (diuretics (DIU); beta blockers (BB); calcium channel blockers (CCB); ACE inhibitors (ACEi); angiotensin II receptor blockers (ARB)), each containing 73,592 patients. A Cox regression model was used to analyze the association between each antihypertensive drug class and UTI incidence as compared to all other antihypertensive drug classes (as a group).

RESULTS

The incidence of UTI diagnosis was slightly higher in patients treated with DIU (8.6%), followed by ACEi (8.1%), ARB (7.9%), and CCB (6.5%). Antibiotic therapy for UTI was given in 5.6% of DIU and 4.3% of CCB patients. The incidence of UTI and antibiotic therapy was much higher in women than in men across all therapy classes. No significant increase or decrease in UTI incidence or antibiotic therapy was observed in any of the AH therapy classes investigated.

CONCLUSION

The present study did not identify a significant increase or decrease of UTI incidence or antibiotic therapy in patients treated with ACEi, ACB, CCB, beta blockers or diuretics. Across all AH classes studied, the incidence of UTI and antibiotic therapy was higher in women than in men, although not significantly.

Sulfonylurea and Cancer Risk Among Patients With Type 2 Diabetes: A Population-Based Cohort Study

BACKGROUND

Current evidence of the association between the use of sulfonylurea and cancer risk is highly conflicting and little evidence of this association is from the mainland Chinese population. This study aimed to evaluate the potential effects of sulfonylurea use on cancer risk among patients with type 2 diabetes mellitus (T2DM).

METHODS

A retrospective cohort study of T2DM patients who were new users of sulfonylurea or metformin was conducted using the Yinzhou Regional Health Care Database. A marginal structural Cox model was used to estimate the hazard ratio (HR) of cancer associated with the use of sulfonylurea compared with metformin, with time-varying confounders controlled by inverse probability weighting. Secondary analyses using different glucose-lowering drugs (GLDs) as comparator and sensitivity analyses for potential bias due to latency period, model misspecification, missing data, analyses strategy (intention-to-treat and per-protocol), and diagnosis validation were performed to examine the robustness of the results.

RESULTS

After fully controlling for time-varying confounding, baseline confounding, and competing risk, the use of sulfonylurea was not associated with the risk of any cancer (HR 1.09; 95% CI, 0.93-1.27), compared with the use of metformin. In the secondary analyses, compared with α - glucosidase inhibitors, thiazolidinediones, glinides, other GLDs except sulfonylure and insulin, and T2DM patients not treated with sulfonylureas, the HRs of the association between sulfonylurea use and cancer risk were 0.92 (95% CI; 0.78-1.08), 0.89 (95% CI; 0.66-1.19), 0.85 (95% CI; 0.71-1.02), 1.04 (95% CI; 0.89-1.22), and 1.07 (95% CI; 0.99-1.16), respectively. The results of analyses for various subgroups, risk of site-specific cancers, cumulative duration, dose-response relationship, and sensitivity analyses of different latency periods and missing data were generally consistent with the findings of the primary analyses.

CONCLUSION

No association between sulfonylurea use and cancer risk was found in this study after properly controlling biases due to time-varying confounders and other sources. Further studies on the association between sulfonylurea use and the risk of cancer by using data from a Chinese population with higher representativeness are needed.

Cancer and diabetes: the interlinking metabolic pathways and repurposing actions of antidiabetic drugs

Cancers are regarded as one of the main causes of death and result in high health burden worldwide. The management of cancer include chemotherapy, surgery and radiotherapy. The chemotherapy, which involves the use of chemical agents with cytotoxic actions is utilised as a single treatment or combined treatment. However, these managements of cancer such as chemotherapy poses some setbacks such as cytotoxicity on normal cells and the problem of anticancer drug resistance. Therefore, the use of other therapeutic agents such as antidiabetic drugs is one of the alternative interventions used in addressing some of the limitations in the use of anticancer agents. Antidiabetic drugs such as sulfonylureas, biguanides and thiazolidinediones showed beneficial and repurposing actions in the management of cancer, thus, the activities of these drugs against cancer is attributed to some of the metabolic links between the two disorders and these includes hyperglycaemia, hyperinsulinemia, inflammation, and oxidative stress as well as obesity. Furthermore, some studies showed that the use of antidiabetic drugs could serve as risk factors for the development of cancerous cells particularly pancreatic cancer. However, the beneficial role of these chemical agents overweighs their detrimental actions in cancer management. Hence, the present review indicates the metabolic links between cancer and diabetes and the mechanistic actions of antidiabetic drugs in the management of cancers.

Positive effect of metformin treatment in colorectal cancer patients with type 2 diabetes: national cohort study

We aimed to estimate colorectal cancer risk in patients with type 2 diabetes mellitus (T2DM) using metformin. Patients with colorectal cancer and diabetes from 2000 to 2012 were identified form Lithuanian Cancer Registry and the National Health Insurance Fund database. Standardized incidence ratios (SIRs) for colorectal cancers as a ratio of observed number of cancer cases in people with diabetes to the expected number of cancer cases in the underlying general population was calculated. We analysed 111 109 patients with diabetes. Overall, 1213 colorectal cancers were observed versus 954.91 expected within a period of observation entailing an SIR of 1.27 [95% confidence interval (CI): 1.20-1.34]. Significantly higher risk of colorectal cancer was found both in male and female patients with diabetes in all age groups. Higher risk was found for both colon and rectum cancers 1.36 (95% CI: 1.27-1.46) and 1.11 (95% CI: 1.01-1.22), respectively. There were no differences in risk over time since initial diabetes diagnosis. Never-users of metformin had twice higher risk of colorectal cancer compared to general population (SIR: 2.14, 95% CI: 1.95-2.35). Among metformin users, risk was lover (SIR: 1.47, 95% CI: 1.36-1.58) and colorectal cancer risk decreased with increasing cumulative dose of metformin (P < 0.001). Patients with T2DM had increased risk of colorectal cancer compared with the general Lithuanian population. Decreasing colorectal cancer risk with increasing cumulative dose of metformin indicates that metformin may be a protective agent for colorectal cancer development.

Repurposing metformin for the treatment of gastrointestinal cancer

Diabetes mellitus type 2 and cancer share many risk factors. The pleiotropic insulin-dependent and insulin-independent effects of metformin might inhibit pathways that are frequently amplified in neoplastic tissue. Particularly, modulation of inflammation, metabolism, and cell cycle arrest are potential therapeutic cancer targets utilized by metformin to boost the anti-cancer effects of chemotherapy. Studies in vitro and in vivo models have demonstrated the potential of metformin as a chemo- and radiosensitizer, besides its chemopreventive and direct therapeutic activity in digestive system (DS) tumors. Hence, these aspects have been considered in many cancer clinical trials. Case-control and cohort studies and associated meta-analyses have evaluated DS cancer risk and metformin usage, especially in colorectal cancer, pancreatic cancer, and hepatocellular carcinoma. Most clinical studies have demonstrated the protective role of metformin in the risk for DS cancers and survival rates. On the other hand, the ability of metformin to enhance the actions of chemotherapy for gastric and biliary cancers is yet to be investigated. This article reviews the current findings on the anti-cancer mechanisms of metformin and its apparatus from pre-clinical and ongoing studies in DS malignancies.

Metformin, Microbiome and Protection Against Colorectal Cancer

Metformin is widely used as a firstline therapy to improve insulin sensitivity in type 2 diabetes mellitus (T2DM) patients. This is achieved primarily through regulating AMP-activated protein kinase (AMPK)-dependent pathways leading to reduced hepatic gluconeogenesis and improved muscular uptake of glucose. Epidemiological studies first recognized a relationship with metformin use in T2DM patients and reduced colorectal cancer (CRC) risk. Thereafter, metformin has gained wide attention as a candidate CRC chemopreventative agent; however, the molecular mechanisms underlying its gastrointestinal anti-cancer properties appear multi-faceted and are not well understood. An intriguing area of research is the growing evidence of metformin's metabolic juncture with gut microbiota at the intestinal mucosal interface. This review examines the mechanistic evidence which may account for metformin's protection against CRC through interactions between the drug, gut microbiota and the colonic epithelial mucosa.

Prevalent diabetes and risk of total, colorectal, prostate and breast cancers in an ageing population: meta-analysis of individual participant data from cohorts of the CHANCES consortium

BACKGROUND

We investigated whether associations between prevalent diabetes and cancer risk are pertinent to older adults and whether associations differ across subgroups of age, body weight status or levels of physical activity.

METHODS

We harmonised data from seven prospective cohort studies of older individuals in Europe and the United States participating in the CHANCES consortium. Cox proportional hazard regression was used to estimate the associations of prevalent diabetes with cancer risk (all cancers combined, and for colorectum, prostate and breast). We calculated summary risk estimates across cohorts using pooled analysis and random-effects meta-analysis.

RESULTS

A total of 667,916 individuals were included with an overall median (P25-P75) age at recruitment of 62.3 (57-67) years. During a median follow-up time of 10.5 years, 114,404 total cancer cases were ascertained. Diabetes was not associated with the risk of all cancers combined (hazard ratio (HR) = 0.94; 95% confidence interval (CI): 0.86-1.04; I2 = 63.3%). Diabetes was positively associated with colorectal cancer risk in men (HR = 1.17; 95% CI: 1.08-1.26; I2 = 0%) and a similar HR in women (1.13; 95% CI: 0.82-1.56; I2 = 46%), but with a confidence interval including the null. Diabetes was inversely associated with prostate cancer risk (HR = 0.81; 95% CI: 0.77-0.85; I2 = 0%), but not with postmenopausal breast cancer (HR = 0.96; 95% CI: 0.89-1.03; I2 = 0%). In exploratory subgroup analyses, diabetes was inversely associated with prostate cancer risk only in men with overweight or obesity.

CONCLUSIONS

Prevalent diabetes was positively associated with colorectal cancer risk and inversely associated with prostate cancer risk in older Europeans and Americans.

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

PURPOSE

This study aimed to investigate the association between metformin usage and the risk of colorectal cancer (CRC) using data from the Korean National Health Insurance Service-National Health Screening Cohort database.

METHODS

Data from the NHIS-HEALS cohort between 2002 and 2015 were longitudinally analyzed. Subjects were divided into three groups: metformin non-users with diabetes mellitus (DM), metformin users with DM, and no DM group. CRC was defined using the ICD-10 code (C18.0-C20.0) at the time of admission. Cox proportional hazard regression models were adopted after stepwise adjustment for confounders to investigate the association between metformin usage and colorectal cancer risk.

RESULTS

During the follow-up period, of the total 323,430 participants, 2341 (1.33%) of the 175,495 males and 1204 (0.81%) of the 147,935 females were newly diagnosed with CRC. The estimated cumulative incidence of CRC was significantly different among the three groups based on Kaplan-Meier's survival curve (p values < 0.05 in both sexes). Compared with metformin non-users, hazard ratios (95% CIs) of metformin users and the no DM group were 0.66 (0.51-0.85) and 0.72 (0.61-0.85) in males and 0.59 (0.37-0.92) and 0.93 (0.66-1.29) in females, respectively, after being fully adjusted.

CONCLUSIONS

Metformin users with diabetes appear to have a significantly lower risk of CRC compared with metformin non-users.

Metformin and risk of cancer among patients with type 2 diabetes mellitus: A systematic review and meta-analysis

AIM

We carried out this meta-analysis on all published studies to estimate the overall cancer risk of the use of metformin in T2DM patients.

METHODS

We searched the PubMed, Embase and CNKI databases for all articles within a range of published years from 2007 to 2019 on the association between the use of metformin and cancer risk in T2DM patients. The odds ratio (OR) corresponding to the 95% confidence interval (95% CI) was used to assess the association using a random-effect meta-analysis.

RESULTS

Finally, 67 studies met the inclusion criteria for this study, with 10,695,875 T2DM patients and 145,108 cancer cases. Overall, For T2DM patients of ever vs. never metformin users, there was statistical evidence of significantly decreased cancer risk was found to be associated with ever metformin users (OR=0.70, 95% CI=0.65-0.76). Considering T2DM may be a specific and independent risk factor for various forms of cancer, due to its particular metabolic characteristics of glucose intolerance and hyperinsulinemia, we performed a comparison to estimate the effects of metformin on cancer risk with other anti-diabetes medications (ADMs), our results found significantly decreased cancer risk to be associated with the use of metformin (OR=0.80, 95% CI=0.73-0.87).

CONCLUSION

Our meta-analysis indicated that metformin may be a independent protective factor for cancer risk in T2DM patients.

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

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

Relationship between metformin therapy and risk of colorectal cancer in patients with diabetes mellitus: a meta-analysis

OBJECTIVE

At present, there are many studies on metformin and the risk of colorectal cancer in patients with diabetes, but the conclusions are contradictory. Our aim is to comprehensively collect the published literature and systematically evaluate the relationship between metformin and the risk of colorectal cancer in patients with diabetes.

METHODS

We systematically searched the MEDLINE, EMBASE, and CENTRAL databases up to March 2020. We adopted adjusted estimates and their 95% confidence intervals (CI) to calculate summary effect estimates using either a fixed-effects or a random-effects model.

RESULTS

A total of 17 articles were included in this study, with a total of 1,092,074 patients with diabetes. Meta-analysis of observational studies showed that metformin treatment could significantly reduce the incidence of colorectal cancer in diabetic patients (adjusted RR = 0.884, 95%CI = 0.829-0.943), and there was heterogeneity between studies (p = 0.013, I² = 47.9%). Subgroup analysis showed that metformin treatment was significantly associated with a significantly reduced risk of colorectal cancer in diabetics in America and Europe (adjusted RR = 0.852, 95%CI = 0.786-0.924; adjusted RR = 0.900, 95%CI = 0.845-0.958). Patients with diabetes treated with metformin had a significantly lower risk of colorectal cancer compared with patients who had never been treated with metformin or sulfonamide monotherapy (adjusted RR = 0.863, 95%CI = 0.776-0.960; adjusted RR = 0.911, 95%CI = 0.882-0.941).

CONCLUSIONS

Metformin therapy is associated with a significantly reduced risk of colorectal disease in patients with diabetes, and it is necessary to conduct larger, more standardized clinical studies to verify this conclusion.

Molecular mechanisms underlining the role of metformin as a therapeutic agent in lung cancer

BACKGROUND

Metformin, a first-line therapeutic for type 2 diabetes, has been studied for its potential use in cancer treatment following a number of epidemiological studies that have demonstrated reduced cancer incidence and mortality rates among patients treated with the drug. As yet, however, there remains significant uncertainty about the molecular mechanisms by which metformin exerts its anti-cancer effects. Herein, we summarize the evidence surrounding the anti-lung cancer effects of metformin.

CONCLUSIONS

Specifically, we explore protein targets of metformin, including AMPK, PP2A, IRF-1/YAP and HGF and we outline the proposed mechanisms of action for metformin in lung cancer, with particular attention given to apoptosis and autophagy. We also closely examine the synergistic activity of metformin with existing cancer treatment regimens, such as TKI's, platinum-based agents and immune therapeutics. In addition to considering preclinical and clinical studies, we also dissect and contextualize the limitations and inconsistencies of the current literature, especially those of epidemiological studies. Finally, we offer a potential trajectory for future research in this rapidly evolving area of basic and clinical oncology.

Metformin Inhibited Proliferation and Metastasis of Colorectal Cancer and presented a Synergistic Effect on 5-FU

The purpose of this study was to investigate the effect of metformin or the combination of metformin and 5-FU on the growth and metastasis of colorectal cancer (CRC). For the in vitro experiments, HCT 116 and SW1463 cell lines were treated with metformin or the combination of metformin and 5-FU. Cell proliferation and invasion were analyzed by CCK-8, colony formation, and transwell assay, respectively. For the in vivo experiments, the CRC xenograft nude mice model was used to observe the effects of metformin or combined with 5-FU on tumor growth and metastasis. Metformin significantly inhibited the proliferation and invasion of HCT116 and SW1463 cells in vitro, which showed synergetic effects to 5-FU. In CRC xenograft nude mice, metformin alone and metformin combined with 5-FU treatment significantly inhibited tumor cell proliferation and tumor metastasis. In summary, metformin played an inhibitory role in the proliferation and metastasis of CRC and had a synergistic effect with 5-FU. Metformin may be a potentially effective anti-metastatic drug or an anticancer adjuvant agent for treating CRC.

Metformin and colorectal cancer: a systematic review, meta-analysis and meta-regression

PURPOSE

Metformin may have a role in reducing the incidence of colorectal cancer (CRC) and improving survival outcome. This meta-analysis explored the effect of metformin use on colorectal adenoma and cancer incidence, and colorectal oncological outcomes.

METHODS

A database search was conducted on Medline, Embase and CNKI for studies comparing metformin vs. non-metformin users, metformin users vs. non-diabetics and metformin users vs. diabetics with diet-only treatment. Meta-analysis was done with DerSimonian and Laird with risk ratios (RR), and hazard ratios (HR) for survival outcomes.

RESULTS

We included 58 studies and summarized incidences of colorectal adenoma and cancer, as well as cancer survival outcomes. Metformin users had a significant lower incidence of colorectal adenoma (RR 0.77, CI 0.67-0.88, p < 0.001), advanced adenoma (0.61, CI 0.42-0.88, p = 0.008) and CRC (RR 0.76, CI 0.69-0.84, p < 0.001) respectively compared with non-metformin users. Overall survival (HR 0.6, CI 0.53-0.67, p < 0.001) and CRC-specific survival (HR 0.66, CI 0.59-0.74, p < 0.001) were higher among metformin users compared with non-metformin users. Further analysis on overall survival of metastatic CRC patients revealed significantly higher survival rates in metformin users (HR 0.77, CI 0.68-0.87, p < 0.001).

CONCLUSION

This meta-analysis showed that metformin use significantly reduces colorectal adenoma and cancer incidence and improves colorectal cancer outcomes.

Assessing the Current State of Lung Cancer Chemoprevention: A Comprehensive Overview

Chemoprevention of lung cancer is thought to significantly reduce the risk of acquiring these conditions in the subpopulation of patients with underlying health issues, such as chronic obstructive pulmonary disorder and smoking-associated lung problems. Many strategies have been tested in the previous decades, with very few translating to successful clinical trials in specific subpopulations of patients. In this review, we analyze these strategies, as well as new approaches that have emerged throughout the last few years, including synthetic lethality concept and microbiome-induced regulation of lung carcinogenesis. Overall, the continuous effort in the area of lung chemoprevention is required to develop practical therapeutical approaches. Given the inconsistency of results obtained in clinical trials targeting lung cancer chemoprevention in various subgroups of patients that differ in the underlying health condition, race, and gender, we believe that individualized approaches will have more promise than generalized treatments.

Type 2 diabetes, breast cancer specific and overall mortality: Associations by metformin use and modification by race, body mass, and estrogen receptor status

INTRODUCTION

While type 2 diabetes (T2D) has been associated with increased all-cause mortality among women diagnosed with breast cancer (BC), the association between T2D and breast cancer-specific (BCS) mortality is unresolved. The goal of this study was to examine the association between T2D and BCS mortality and examine the influence of metformin treatment on mortality rates.

METHODS

A retrospective cohort study was conducted between 2002 and 2008 at Emory University Hospitals among non-Hispanic black and white women who had confirmed diagnosis of stage I-III BC and known diabetes status (T2D: n = 73; non-T2D: n = 514). Cox proportional hazard models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Compared to non-T2D patients, T2D women had almost a 2-fold increase in BCS mortality after adjusting for covariates (HR = 2.01; 95%CI = 1.02-3.98). Though attenuated, the increased hazard of death was also observed for all-cause mortality (HR = 1.74; 95%CI = 1.06-2.87). T2D patients who were not on metformin had substantially higher hazard of BCS mortality compared to non-diabetic patients (HR = 4.54; 95%CI = 1.98-10.44), whereas the association among T2D patients treated with metformin was weak (HR = 1.20; 95%CI = 0.36-3.97) and included the null.

CONCLUSIONS

Among women with BC, T2D is associated with increased BCS mortality. Metformin treatment for T2D during the initial diagnosis of BC may improve outcomes.

Review: Diabetes, Obesity, and Cancer-Pathophysiology and Clinical Implications

Obesity and diabetes have both been associated with an increased risk of cancer. In the face of increasing obesity and diabetes rates worldwide, this is a worrying trend for cancer rates. Factors such as hyperinsulinemia, chronic inflammation, antihyperglycemic medications, and shared risk factors have all been identified as potential mechanisms underlying the relationship. The most common obesity- and diabetes-related cancers are endometrial, colorectal, and postmenopausal breast cancers. In this review, we summarize the existing evidence that describes the complex relationship between obesity, diabetes, and cancer, focusing on epidemiological and pathophysiological evidence, and also reviewing the role of antihyperglycemic agents, novel research approaches such as Mendelian Randomization, and the methodological limitations of existing research. In addition, we also describe the bidirectional relationship between diabetes and cancer with a review of the evidence summarizing the risk of diabetes following cancer treatment. We conclude this review by providing clinical implications that are relevant for caring for patients with obesity, diabetes, and cancer and provide recommendations for improving both clinical care and research for patients with these conditions.

More recent, better designed studies have weakened links between antidiabetes medications and cancer risk

BACKGROUND

An increasing number of studies have investigated associations of antidiabetes medications with cancer risk. Antidiabetes medications are classified by their mechanisms of action on tissues and organs. They potentially act as both causative and confounding factors in the temporal association of diabetes and cancer.

AIM

To present the current evidence regarding both the carcinogenic and anti-carcinogenic effects of antidiabetes medications on cancer in humans.

METHODS

A review of the scientific literature.

RESULTS

The most conclusive evidence shown of an association of antidiabetes medication with a specific cancer was for that of the thiazolidinedione pioglitazone with bladder cancer. Currently, there is inconclusive evidence regarding a possible association of incretin therapies, drugs of the dipeptidyl peptidase-4 inhibitor class, with the risk of pancreatic cancer. Insulin, sulfonylureas, metformin and sodium-glucose co-transporter-2 inhibitors appear not to be associated with increased risk of any cancer. Sparse evidence suggests possible protective effects against cancer incidence of metformin, sulfonylureas, thiazolidinediones, incretin-based drugs and sodium-glucose co-transporter-2 inhibitors.

CONCLUSION

The conflicting evidence regarding associations of antidiabetes medications with cancer risk is apparently attributable to both methodological issues and to the complexity of the subject. More recent and better-designed studies have weakened the evidence for links between antidiabetes medications and cancer risk.

Chemoprevention of Colorectal Cancer

Although colorectal cancer (CRC) screening has reduced the incidence of and mortality from CRC, chemoprevention strategies have the potential to further reduce CRC incidence and mortality. Chemoprevention agents might be used for average-risk as well as high-risk groups, and to prevent CRC recurrence after therapy. CRC chemoprevention agents that have been studied include aspirin, nonaspirin nonsteroidal anti-inflammatory drugs, statins, agents that target metabolic pathways, and vitamins and minerals. We review the prospect of chemoprevention of CRC, results from preclinical and human studies, challenges, and future directions.

Effect of metformin on the risk of prostate cancer in patients with type 2 diabetes by considering different confounding factors: a meta-analysis of observational studies

Preclinical studies have suggested the antitumorigenic properties of metformin on prostate cancer; results from epidemiological studies remain contradictory. We aim to investigate the evidence of metformin and the risk of prostate cancer. PubMed, Embase, Cochrane Library, and Web of Science databases were searched for eligible studies. Meta-analyses were carried out using the most fully adjusted hazard ratios and the corresponding 95% confidence intervals. Eighteen cohort studies and six case-control studies representing 2 009 504 male patients with type 2 diabetes mellitus were identified. The pooled HR of prostate cancer for metformin therapy was 0.97 (0.84-1.12) in case-control studies and 0.94 (0.79-1.12) in cohort studies, respectively. In cohort studies, we found that there was a modest association in studies with samples from Europe, but not in studies with samples from North America, Asia, and Oceania. In addition, metformin showed a slightly protective effect compared with sulfonylurea, but not insulin and other comparators. Meta-regression analyses found that obesity and prostate-specific antigen adjustment in statistical models may be the sources of heterogeneity. However, there were no significant differences in subgroups stratified by time-related biases, analytical approaches, types of risk estimates, study quality, publication year, and whether adjusted for smoking, alcohol abuse, hemoglobin A1c, diabetes duration, and other confounding factors. Our study showed that metformin therapy was not associated with the risk of prostate cancer in patients with type 2 diabetes mellitus. However, exploratory analyses suggest that metformin use may be protective in a certain subgroup of patients.

Metformin in colorectal cancer: molecular mechanism, preclinical and clinical aspects

Growing evidence showed the increased prevalence of cancer incidents, particularly colorectal cancer, among type 2 diabetic mellitus patients. Antidiabetic medications such as, insulin, sulfonylureas, dipeptyl peptidase (DPP) 4 inhibitors and glucose-dependent insulinotropic peptide (GLP-1) analogues increased the additional risk of different cancers to diabetic patients. Conversely, metformin has drawn attention among physicians and researchers since its use as antidiabetic drug exhibited beneficial effect in the prevention and treatment of cancer in diabetic patients as well as an independent anticancer drug. This review aims to provide the comprehensive information on the use of metformin at preclinical and clinical stages among colorectal cancer patients. We highlight the efficacy of metformin as an anti-proliferative, chemopreventive, apoptosis inducing agent, adjuvant, and radio-chemosensitizer in various colorectal cancer models. This multifarious effects of metformin is largely attributed to its capability in modulating upstream and downstream molecular targets involved in apoptosis, autophagy, cell cycle, oxidative stress, inflammation, metabolic homeostasis, and epigenetic regulation. Moreover, the review highlights metformin intake and colorectal cancer risk based on different clinical and epidemiologic results from different gender and specific population background among diabetic and non-diabetic patients. The improved understanding of metformin as a potential chemotherapeutic drug or as neo-adjuvant will provide better information for it to be used globally as an affordable, well-tolerated, and effective anticancer agent for colorectal cancer.

Suppressive effects of metformin on colorectal adenoma incidence and malignant progression

BACKGROUND

The linear progression from normal colonic epithelium to adenoma initiation, carcinoma transformation and metastasis is considered the classical model of colorectal cancer (CRC) development. Although metformin has been extensively reported to be negatively related to cancer incidence, the effect of metformin on CRC development remains unclear. We aimed to evaluate the role of metformin in the entire CRC linear progression.

METHODS

Systematic searches and data extraction were performed in the PubMed, Embase, and Cochrane Library databases on Jan 31, 2019. The combined relative ratios (RRs) of colorectal tumor incidence and the hazard ratios (HRs) of overall survival (OS) and cancer-specific survival (CSS) were evaluated by a random-effects model. Then, the effects of metformin were further assessed through stratified analyses by population, medication duration and dosage, dose-response analysis and comparison with other antidiabetic agents.

RESULTS

A total of 50 studies consisting of 238,540 cases of diabetes mellitus (DM) were included in this study. Metformin use was negatively associated with the incidence of colorectal adenoma (RR: 0.75, 95% CI: 0.65-0.86) and CRC (RR: 0.73, 95% CI: 0.58-0.90). Moreover, CRC patients benefited from metformin in terms of both OS (HR: 0.73, 95% Cl: 0.63-0.84) and CSS (HR: 0.60, 95% Cl: 0.50-0.73). Stratified analyses suggested that a long duration of high-dose metformin (RR: 0.52, 95% Cl: 0.36-0.83) was more effective than a short duration in Asian populations against colorectal adenoma (RR: 0.66, 95% Cl: 056-0.70) and CRC (RR: 0.45, 95% Cl: 0.29-0.70). Interestingly, metformin use decreased CRC risk in a dose-dependent manner (RR: 0.91, 95% CI: 0.87-0.95). In addition, the benefit of metformin on CRC was more significant than that of other antidiabetic agents, including insulin.

CONCLUSIONS

The use of metformin is associated with a lower incidence of adenoma and CRC and a better prognosis, especially in Asian populations.

Controversial association between polycystic ovary syndrome and breast cancer

Polycystic ovary syndrome (PCOS) risk factors overlap with breast cancer, and the hormonal profile may be implicated in breast cancer pathogenesis. This study aims to report a literature review considering epidemiological and molecular mechanisms that correlate PCOS and breast cancer, as well as the influence of PCOS treatment on the incidence of breast cancer. Epidemiological studies failed to adjust potential variables that affect the risk and have thus provided inconclusive results. Molecular effects of androgenic pathways in breast cancer have been studied and androgens seem to have an inhibitory effect on mammary epithelial proliferation. However, increased bioavailable androgens were associated with recurrence of breast cancer due to conversion to oestrogens. Sex hormone-binding globulin has a role in hormone-dependent cancers and can be considered a marker for PCOS; a gene profile has already been linked to breast cancer risk in these patients. PCOS medical treatment is a promising tool for stratifying breast cancer risk due to the metabolic influence and hormonal environment. Clinical reports are inconsistent, emphasizing the need for further studies with a prospective design. In the future, the role of pharmacological interventions in PCOS will increase knowledge and awareness of breast cancer pathogenesis and will help to refine breast cancer risk stratification.

Metformin Treatment and Cancer Risk: Cox Regression Analysis, With Time-Dependent Covariates, of 320,000 Persons With Incident Diabetes Mellitus

There is conflicting evidence regarding the association between metformin use and cancer risk in diabetic patients. During 2002–2012, we followed a cohort of 315,890 persons aged 21–87 years with incident diabetes who were insured by the largest health maintenance organization in Israel. We used a discrete form of weighted cumulative metformin exposure to evaluate the association of metformin with cancer incidence. This was implemented in a time-dependent covariate Cox model, adjusting for treatment with other glucose-lowering medications, as well as age, sex, ethnic background, socioeconomic status, smoking (for bladder and lung cancer), and parity (for breast cancer). We excluded from the analysis metformin exposure during the year before cancer diagnosis in order to minimize reverse causation of cancer on changes in medication use. Estimated hazard ratios associated with exposure to 1 defined daily dose of metformin over the previous 2–7 years were 0.98 (95% confidence interval (CI): 0.82, 1.18) for all-sites cancer (excluding prostate and pancreas), 1.05 (95% CI: 0.67, 1.63) for colon cancer, 0.98 (95% CI: 0.49, 1.97) for bladder cancer, 1.02 (95% CI: 0.59, 1.78) for lung cancer, and 0.88 (95% CI: 0.56, 1.39) for female breast cancer. Our results do not support an association between metformin treatment and the incidence of major cancers (excluding prostate and pancreas).

Combination of Metformin and Gefitinib as First-Line Therapy for Nondiabetic Advanced NSCLC Patients with EGFR Mutations: A Randomized, Double-Blind Phase II Trial

PURPOSE

Preclinical and retrospective studies suggested a role for metformin in sensitizing patients who have diabetes with non-small cell lung cancer (NSCLC) to EGFR tyrosine kinase inhibitors (TKIs). We therefore examined its effects in combination with gefitinib in patients without diabetes harboring EGFR mutations (EGFRm).

PATIENTS AND METHODS

A total of 224 patients without diabetes with treatment-naïve stage IIIB-IV EGFRm NSCLC were randomly assigned in a 1:1 ratio to receive gefitinib plus either metformin or placebo. The primary endpoint was progression-free survival (PFS) rate at 1 year and secondary endpoints included overall survival (OS), PFS, objective response rate (ORR), and safety. Serum levels of IL6 were also examined in an exploratory analysis.

RESULTS

The median duration of follow-up was 19.15 months. The estimated 1-year PFS rates were 41.2% [95% confidence interval (CI), 30.0-52.2] with gefitinib plus metformin and 42.9% (95% CI, 32.6-52.7) with gefitinib plus placebo (P = 0.6268). Median PFS (10.3 months vs. 11.4 months) and median OS (22.0 months vs. 27.5 months) were numerically lower in the metformin group, while ORRs were similar between the two arms (66% vs. 66.7%). No significant treatment group differences were detected across all subgroups with respect to PFS, including those with elevated levels of IL6. Metformin combined with gefitinib resulted in a remarkably higher incidence of diarrhea compared with the control arm (78.38% vs. 43.24%).

CONCLUSIONS

Our study showed that addition of metformin resulted in nonsignificantly worse outcomes and increased toxicity and hence does not support its concurrent use with first-line EGFR-TKI therapy in patients without diabetes with EGFRm NSCLC.

Diabetes Mellitus and Colon Carcinogenesis: Expectation for Inhibition of Colon Carcinogenesis by Oral Hypoglycemic Drugs

The global deaths due to colorectal cancer and diabetes mellitus have increased by 57% and 90%, respectively. The relationship between various cancers and diabetes mellitus has been shown in multiple epidemiological studies. Hence, better management of diabetes mellitus is expected to reduce the risk of various cancers. This review focuses on colorectal cancer and aims to summarize recent findings on the antitumor effects of various oral hypoglycemic drugs on colorectal cancer and their estimated mechanisms. Of the seven classes of oral hypoglycemic agents, only metformin was found to have suppressive effects on colorectal cancer in both clinical and basic research. Clinical and basic researches on suppressing effects of glinides, dipeptidyl peptidase-4 inhibitors, thiazolidinedione, α-glucosidase inhibitors, and sodium glucose cotransporter-2 inhibitors against colon carcinogenesis have been insufficient and have not arrived at any conclusion. Therefore, further research regarding these agents is warranted. In addition, the suppressive effects of these agents in healthy subjects without diabetes should also be investigated.

A Cohort Study of Metformin and Colorectal Cancer Risk among Patients with Diabetes Mellitus

Background: Several epidemiologic studies have reported strong inverse associations between metformin use and risk of colorectal cancer, although time-related biases, such as immortal time bias, may in part explain these findings. We reexamined this association using methods to minimize these biases.Methods: A cohort study was conducted among 47,351 members of Kaiser Permanente Northern California with diabetes and no history of cancer or metformin use. Follow-up for incident colorectal cancer occurred from January 1, 1997, until June 30, 2012. Cox regression was used to calculate HRs and 95% confidence intervals (CIs) for colorectal cancer risk associated with metformin use (ever use, total duration, recency of use, and cumulative dose).Results: No association was observed between ever use of metformin and colorectal cancer risk (HR, 0.90; 95% CI, 0.76-1.07) and there was no consistent pattern of decreasing risk with increasing total duration, dose, or recency of use. However, long-term use (≥5.0 years) appeared to be associated with reduced risk of colorectal cancer in the full population (HR, 0.78; 95% CI, 0.60-1.02), among current users (HR, 0.78; 95% CI, 0.59-1.04), and in men (HR, 0.65; 95% CI, 0.45-0.94) but not in women. Higher cumulative doses of metformin were associated with reduced risk. In initial users of sulfonylureas, switching to or adding metformin was also associated with decreased colorectal cancer risk.Conclusions: Our findings showed an inverse association between long-term use of metformin and colorectal cancer risk. Findings, especially the risk reduction among men, need to be confirmed in large, well-conducted studies.Impact: If our findings are confirmed, metformin may have a role in the chemoprevention of colorectal cancer. Cancer Epidemiol Biomarkers Prev; 27(5); 525-30. ©2018 AACRSee related commentary by Jackson and García-Albéniz, p. 520.

Drug repurposing in oncology: Compounds, pathways, phenotypes and computational approaches for colorectal cancer

The strategy of using existing drugs originally developed for one disease to treat other indications has found success across medical fields. Such drug repurposing promises faster access of drugs to patients while reducing costs in the long and difficult process of drug development. However, the number of existing drugs and diseases, together with the heterogeneity of patients and diseases, notably including cancers, can make repurposing time consuming and inefficient. The key question we address is how to efficiently repurpose an existing drug to treat a given indication. As drug efficacy remains the main bottleneck for overall success, we discuss the need for machine-learning computational methods in combination with specific phenotypic studies along with mechanistic studies, chemical genetics and omics assays to successfully predict disease-drug pairs. Such a pipeline could be particularly important to cancer patients who face heterogeneous, recurrent and metastatic disease and need fast and personalized treatments. Here we focus on drug repurposing for colorectal cancer and describe selected therapeutics already repositioned for its prevention and/or treatment as well as potential candidates. We consider this review as a selective compilation of approaches and methodologies, and argue how, taken together, they could bring drug repurposing to the next level.

Association of antidiabetic medication and statins with breast cancer incidence in women with type 2 diabetes

Purpose

To address the possible association between the use of metformin, other forms of antidiabetic medication (ADM) and statins with the incidence of breast cancer in women with type 2 diabetes (T2D).

Methods

Data were collected from a Finnish nationwide diabetes database (FinDM). The study cohort consisted of women diagnosed with T2D in 1996–2011 in Finland. In full-cohort analysis, Poisson regression was used to estimate hazard ratios (HRs) in relation to use of metformin, insulin, other forms of oral ADM and statins. In nested case–control analysis, up to 20 controls were matched for age and duration of diabetes to each case of breast cancer. Conditional logistic regression was used to estimate HRs in relation to medication use and cumulative use of different forms of ADM, and statins.

Results

2300 women were diagnosed with breast cancer during follow-up. No difference in breast cancer incidence was observed between metformin users [HR 1.02, 95% confidence interval (CI) 0.93–1.11] or statin users (HR 0.97, 95% CI 0.89–1.05) compared with non-users. In nested case–control analysis the results were similar. Use of insulin (HR 1.18, 95% CI 1.03–1.36) was associated with a slightly increased incidence of breast cancer.

Conclusions

No evidence of an association between the use of metformin or statins and the incidence of breast cancer in women with T2D was found. Among insulin users, a slightly higher incidence of breast cancer was observed.

Electronic supplementary material

The online version of this article (10.1007/s10549-019-05185-0) contains supplementary material, which is available to authorized users.

Metformin use and prostate cancer risk: A meta-analysis of cohort studies

BACKGROUND

The relationship between metformin use and the risk of prostate cancer is still inconclusive. Therefore, we performed a systematic review and meta-analysis of all eligible cohort studies to evaluate a potential association of metformin use with prostate cancer risk.

METHODS

A comprehensive literature search was performed in PubMed and Web of Science databases through July 2018. A DerSimonian and Laird random-effects model was applied to calculate the pooled relative risk (RR) and its 95% confidence interval (CI).

RESULTS

Eighteen cohort or nested case-control studies were included in this study with a total of 52,328 cases. In a random-effect pooled analysis, metformin use was not significantly associated with the risk of prostate cancer (RR 0.97, 95% CI 0.80-1.16, P = .711). Statistically significant heterogeneity was identified among included studies (P < .001, I = 98.1%). Sensitivity analysis indicated that no single study dominated the pooled RR.

CONCLUSION

The present large meta-analysis of cohort studies did not find an association between metformin use and prostate cancer risk.

Metformin Use and Lung Cancer Risk in Diabetic Patients: A Systematic Review and Meta-Analysis

Background

Antidiabetic medications (ADMs) can alter the risk of different types of cancer, but the relationship between lung cancer incidence and metformin remains controversial. Our aim was to quantitatively estimate the relationship between incidences of lung cancer and metformin in patients with diabetes in this meta-analysis.

Methods

We performed a search in PubMed, Embase, ISI Web of Science, and Cochrane Library until September 20, 2017. The odds ratio (OR), relative risk (RR) or hazard ratio (HR), and 95% confidence interval (95% CI) were estimated using the random-effect model. The Newcastle-Ottawa Scale (NOS) was used to assess the study quality.

Results

A total of 13 studies (10 cohort studies and 3 case-control studies) were included in the meta-analysis. Compared to nonmetformin users, metformin probably decreased lung cancer incidence in diabetic patients (RR = 0.89; 95% CI, 0.83-0.96; P = 0.002) with significant heterogeneity (Q = 35.47, I² = 66%, P = 0.0004). Subgroup analysis showed that cohort studies (RR = 0.91; 95% CI, 0.85-0.98; P = 0.008), location in Europe (RR = 0.90; 95% CI, 0.86-0.94; P < 0.0001), the control drug of the sulfonylurea group (RR = 0.91; 95% CI, 0.86-0.96; P = 0.001), and adjusting for smoking (RR = 0.86; 95% CI, 0.75-1.00; P = 0.05) may be related to lower lung cancer risk. No significant publication bias was detected using a funnel plot.

Conclusion

Metformin use was related to a lower lung cancer risk in diabetic patients compared to nonusers, but this result was retrieved from observational studies and our findings need more well-designed RCTs to confirm the association.

Monotherapy with Metformin versus Sulfonylureas and Risk of Cancer in Type 2 Diabetic Patients: A Systematic Review and Meta-Analysis

BACKGROUND

Accumulating evidence suggests that patients with type 2 diabetes mellitus and hyperinsulinemia are at an increased risk of developing malignancies. It remains to be fully elucidated whether the use of metformin, an insulin sensitizer, and/or sulfonylureas, insulin secretagogues, affects cancer incidence in subjects with type 2 diabetes mellitus.

OBJECTIVE

A systematic review and meta-analysis was performed to compare the risk of cancer incidence associated with monotherapy with metformin compared with monotherapy with sulfonylureas in type 2 diabetes mellitus patients.

METHODS

Search was performed throughout MEDLINE/PubMed, EMBASE, Google Scholar, Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov up until December 2018. In this meta-analysis, each raw data (unadjusted) and study-specific (adjusted) relative risks (RRs) was combined and the pooled unadjusted and adjusted RRs with the 95% CI were calculated using the random-effects model with inverse-variance weighting. Heterogeneity among the studies was evaluated using I ² statistics. Publication bias was evaluated using the funnel plot asymmetry test. The Newcastle-Ottawa scale (NOS) was used to assess the study quality.

RESULTS

A total of 8 cohort studies were included in the meta-analysis. Obvious heterogeneity was noted, and monotherapy with metformin was associated with a lower risk of cancer incidence (unadjusted RR = 0.74, 95% CI: 0.55-0.99, I ² = 97.89%, p < 0.00001; adjusted RR = 0.76, 95% CI: 0.54-1.07, I ² = 98.12%, p < 0.00001) compared with monotherapy with sulfonylurea, using the random-effects model with inverse-variance weighting.

CONCLUSIONS

According to this review, the monotherapy with metformin appears to be associated with a lower risk of cancer incidence than monotherapy with sulfonylurea in patients with type 2 diabetes. This analysis is mainly based on cohort studies, and our findings underscore the need for large-scale randomized controlled trials to establish the effect of metformin monotherapy, relative to sulfonylureas monotherapy on cancer.

Diet, obesity and colorectal carcinoma risk: results from a national cancer registry-based middle-eastern study

BACKGROUND

Cancer of colon and rectum (colorectal) is one of the most common cancers worldwide. There is a scarcity of published data on the risk factors for colorectal cancer (CRC) from the Middle-Eastern countries specifically in Kuwait. Therefore, this matched case-control study sought to examine the risk factors associated with CRC in Kuwait.

METHODS

One hundred and three histopathologically confirmed colorectal cancer cases were recruited from Kuwait Cancer Control Centre Registry. Two hundred and six controls matched with cases (2:1 ratio) on age, gender and nationality were selected from medical, ophthalmology, orthopedic and/ or surgical out-patient clinics at three main general hospitals in Kuwait. A structured questionnaire was used to collect the data from cases and controls through face-to-face interview. Adjusted matched odds ratios (mOR_adj) and their 95% confidence intervals (CI) were estimated using a multivariable conditional logistic regression model.

RESULTS

Multivariable conditional logistic regression model showed that cases were 4.3 times more likely to have had attainted obesity (BMI ≥ 30) in their lifetime compared to controls (mOR_adj = 4.3; 95% CI: 1.6-11.4). Compared to controls, cases rarely consumed fruits and vegetable (mOR_adj = 20.8; 95% CI: 4.4-99.5), tended to consume red meat 2-3 times a week (mOR_adj = 3.8; 95% CI: 1.6-8.7) or more than 4 times a week (mOR_adj = 9.4; 95% CI: 2.5-35.4). Reportedly cases compared to controls frequently (nearly every week) suffered from constipation (mOR_adj = 5.6; 95% CI: 1.9-16.5). However, CRC cases were less likely than controls to have been diagnosed in the past with hypercholesterolemia (mOR_adj = 0.3; 95% CI: 0.2-0.7) or diabetes mellitus type II (mOR_adj = 0.4; 95% CI: 0.2-0.8).

CONCLUSIONS

Obesity, excessive red meat consumption and infrequent fruits/vegetables intake were associated with an increased CRC risk. Overcoming identified pitfalls in dietary pattern and maintenance of healthy weight may help minimize CRC risk in Kuwait and perhaps other countries in the region. Further studies on genetic basis in conjunction with life styles and dietary factors may unravel their joint contributions to CRC risk and furnish tools for curtailing CRC risk in this and other similar populations.

Efficacy of metformin in mediating cellular uptake and inducing apoptosis activity of doxorubicin

The clinical use of doxorubicin (DOX) is limited due to its systemic side effects and drug resistance. Recent evidence suggests that metformin prevents and controls certain but not all types of cancer. The beneficial use of metformin in combination with some chemotherapeutic agents has been reported. The aim of this study is to investigate the influence of metformin on DOX-induced effects in human prostate DU145 cancer cells and clarify its molecular mechanisms. For this purpose, DU145 cells were treated with DOX or metformin, either alone or in combination with each other. The proliferation of DU145 cells was inhibited by DOX-alone and metformin-alone treatment in a time and dose-dependent manner. Metformin could enhance the cytotoxicity of DOX by increasing DOX cellular uptake and cell cycle arrest at G1/S checkpoint which is associated with the enhancement of p21 protein expression. Moreover, metformin could elevate DOX-induced apoptosis in DU145 cells in a concentration-dependent manner and DOX-induced caspase-3 activity. These findings suggest that the combined treatment of metformin with DOX potentiates the anticancer efficacy of DOX in DU145 cells via inhibiting ABCB1 function, cell cycle arrest at G1/S transition and apoptosis induction.

Nuclear translocation of PKM2/AMPK complex sustains cancer stem cell populations under glucose restriction stress

Cancer cells encounter metabolic stresses such as hypoxia and nutrient limitations because they grow and divide more quickly than their normal counterparts. In response to glucose restriction, we found that nuclear translocation of the glycolic enzyme, pyruvate kinase M2 (PKM2), helped cancer cells survive under the metabolic stress. Restriction of glucose stimulated AMPK activation and resulted in co-translocation of AMPK and PKM2 through Ran-mediated nuclear transport. Nuclear PKM2 subsequently bound to Oct4 and promoted the expression of cancer stemness-related genes, which might enrich the cancer stem cell population under the metabolic stress. Nuclear PKM2 was also capable of promoting cancer metastasis in an orthotopic xenograft model. In summary, we found that cytosolic AMPK helped PKM2 carry out its nonmetabolic functions in the nucleus under glucose restriction and that nuclear PKM2 promoted cancer stemness and metastasis. These findings suggested a potential new targeting pathway for cancer therapy in the future.

Valproic acid sensitizes metformin-resistant human renal cell carcinoma cells by upregulating H3 acetylation and EMT reversal

BACKGROUND

Metformin (Met) is a widely available diabetic drug and shows suppressed effects on renal cell carcinoma (RCC) metabolism and proliferation. Laboratory studies in RCC suggested that metformin has remarkable antitumor activities and seems to be a potential antitumor drug. But the facts that metformin may be not effective in reducing the risk of RCC in cancer clinical trials made it difficult to determine the benefits of metformin in RCC prevention and treatment. The mechanisms underlying the different conclusions between laboratory experiments and clinical analysis remains unclear. The goal of the present study was to determine whether long-term metformin use can induce resistance in RCC, whether metformin resistance could be used to explain the disaccord in laboratory and clinical studies, and whether the drug valproic acid (VPA), which inhibits histone deacetylase, exhibits synergistic cytotoxicity with metformin and can counteract the resistance of metformin in RCC.

METHODS

We performed CCK8, transwell, wound healing assay, flow cytometry and western blotting to detect the regulations of proliferation, migration, cell cycle and apoptosis in 786-O, ACHN and metformin resistance 786-O (786-M-R) cells treated with VPA, metformin or a combination of two drugs. We used TGF-β, SC79, LY294002, Rapamycin, protein kinase B (AKT) inhibitor to treat the 786-O or 786-M-R cells and detected the regulations in TGF-β /pSMAD3 and AMPK/AKT pathways.

RESULTS

786-M-R was refractory to metformin-induced antitumor effects on proliferation, migration, cell cycle and cell apoptosis. AMPK/AKT pathways and TGF-β/SMAD3 pathways showed low sensibilities in 786-M-R. The histone H3 acetylation diminished in the 786-M-R cells. However, the addition of VPA dramatically upregulated histone H3 acetylation, increased the sensibility of AKT and inhibited pSMAD3/SMAD4, letting the combination of VPA and metformin remarkably reappear the anti-tumour effects of metformin in 786-M-R cells.

CONCLUSIONS

VPA not only exhibits synergistic cytotoxicity with metformin but also counteracts resistance to metformin in renal cell carcinoma cell. The re-sensitization to metformin induced by VPA in metformin-resistant cells may help treat renal cell carcinoma patients.

Association of Metformin with Breast Cancer Incidence and Mortality in Patients with Type II Diabetes: A GRADE-Assessed Systematic Review and Meta-analysis

Background: Preclinical data suggest that metformin may reduce breast cancer incidence and improve cancer prognosis. However, the current evidence in observational studies is inconclusive. A systematic review and meta-analysis was conducted to assess the effect of metformin on the incidence of breast cancer and all-cause mortality in patients with type II diabetes (T2D).Methods: A literature search was performed on Medline, EMBASE, and the Cochrane library from inception to November 2016. Outcomes were incidence of breast cancer and all-cause mortality. Risk of bias and overall certainty of evidence was assessed using the Newcastle-Ottawa Scale and Grading of Recommendations Assessment, Development, and Evaluation (GRADE), respectively. Meta-analyses were performed using the most fully adjusted ORs or HRs and 95% confidence intervals (95% CI) as effect measures.Results: A total of 12 observational studies were included for breast cancer incidence and 11 studies for all-cause mortality. No significant association was found between metformin exposure and incidence of breast cancer (OR = 0.93; 95% CI, 0.85-1.03; I² = 35%). A 45% risk reduction was observed for all-cause mortality (HR = 0.55; 95% CI, 0.44-0.70; I² = 81%). Presence of publication bias is strongly suspected for both outcomes using Egger's funnel plots.Conclusions: The use of metformin may improve overall survival in patients with T2D and breast cancer. No effect of metformin on the incidence of breast cancer was observed. Interpretation of results is limited by the observational nature of the studies and resulting biases.Impact: Clinical trials are warranted to determine the role of metformin in breast cancer risk reduction and prognosis. Cancer Epidemiol Biomarkers Prev; 27(6); 627-35. ©2018 AACR.

Association of p53 and mitochondrial gene with chemosensitization by metformin in ovarian cancer

OBJECTIVE

This study aims to investigate the association of p53 and D-loop gene with drug resistance and sensitization induced by metformin in ovarian cancer.

RESULTS

Metformin suppresses cells in a time-dependent manner, but the inhibition does not change with the dose of metformin. This suggests that within a certain range of concentration in the body, metformin has a constant inhibitory effect on cells; and the long-term use of metformin yields a better effect.

CONCLUSIONS

Metformin enhances the sensitivity of drug-resistant ovarian cancer cells to chemotherapy.

METHODS

The third passage cells of 17 cancerous ovarian tissues, which were successfully passaged five times, were used as the study objects; and the SKOV3 cell line was used as the positive control. After three adaptations, cells were cultured for 72 hours in an orthogonal experiment using drugs that were used for adaptation. Then, the inhibitory rate on cells in the experimental group was observed by CCK8 assay, in order to study the sensitization effect of metformin in different chemotherapies of ovarian cancer.

Metformin and Colorectal Cancer

Colorectal Cancer (CRC) is one of the most frequently encountered neoplasms in humans. The incidence of CRC has been increasing and new strategies for prevention, including chemoprevention, are required to lower its incidence and associated mortality. Metformin is a biguanide compound commonly used for the treatment of diabetes mellitus. Many recent basic research, epidemiological and clinical trial studies have indicated that metformin has benefits not only in diabetes treatment, but also in lowering the risk of developing cancer (including CRC). These studies indicate that metformin may be a candidate chemoprevention agent for CRC. This review article shall discuss the present evidence of metformin treatment and CRC, as well as outline our challenge in the investigation of metformin use in chemoprevention therapy for colorectal tumors.

Metformin depresses overactivated Notch1/Hes1 signaling in colorectal cancer patients with type 2 diabetes mellitus

The function of metformin in colorectal cancer (CRC) patients with diabetes mellitus (DM) remains a controversial topic because studies are increasingly focusing on epidemiologic features. We examined Notch1/Hes1 signaling in CRC with DM (DM-CRC) and investigated alterations in signaling caused by metformin treatment. For this purpose, information on pathological characteristics was collected from each patient. The proliferation of epithelium labeled with proliferating cell nuclear antigen and the differentiation of goblet cells were investigated using immunohistochemistry and periodic acid-Schiff staining, respectively. The factors involved in Notch1/Hes1 signaling were detected using qRT-PCR and western blot. In our study, we found that lymphatic metastasis, pTNM staging, and the carcinoembryonic antigen level were significantly different between groups. The depth of crypts and the rate of proliferating cell nuclear antigen-positive cells were distinctly higher in DM-CRC and patients who were managed with insulin. Moreover, the goblet cell differentiation rate was decreased in DM-CRC. The expression of Dll1, Notch1, Math1, and RBP-Jκ was increased in DM-CRC, whereas the expression of Dll4 and Hes1 was decreased in this group in normal tissue. In CRC tissue, the expression of Dll1 and Notch1 was clearly higher than that in DM-CRC. Furthermore, the trend in these changes was aggravated with insulin management and alleviated with metformin treatment. In conclusion, the abnormal cell proliferation and differentiation observed in DM-CRC are correlated with overactivated Notch1/Hes1 signaling, which is potentially relieved by metformin treatment.