Diabetes, metformin use, and colon cancer: a population-based cohort study in Taiwan

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 reduces all-cause mortality and diseases of ageing independent of its effect on diabetes control: A systematic review and meta-analysis

This systematic review investigated whether the insulin sensitiser metformin has a geroprotective effect in humans. Pubmed and Embase were searched along with databases of unpublished studies. Eligible research investigated the effect of metformin on all-cause mortality or diseases of ageing relative to non-diabetic populations or diabetics receiving other therapies with adjustment for disease control achieved. Overall, 260 full-texts were reviewed and 53 met the inclusion criteria. Diabetics taking metformin had significantly lower all-cause mortality than non-diabetics (hazard ratio (HR)=0.93, 95%CI 0.88-0.99), as did diabetics taking metformin compared to diabetics receiving non-metformin therapies (HR=0.72, 95%CI 0.65-0.80), insulin (HR=0.68, 95%CI 0.63-0.75) or sulphonylurea (HR=0.80, 95%CI 0.66-0.97). Metformin users also had reduced cancer compared to non-diabetics (rate ratio=0.94, 95%CI 0.92-0.97) and cardiovascular disease (CVD) compared to diabetics receiving non-metformin therapies (HR=0.76, 95%CI 0.66-0.87) or insulin (HR=0.78, 95%CI 0.73-0.83). Differences in baseline characteristics were observed which had the potential to bias findings, although statistical adjustments were made. The apparent reductions in all-cause mortality and diseases of ageing associated with metformin use suggest that metformin could be extending life and healthspans by acting as a geroprotective agent.

Metformin: A Bridge between Diabetes and Prostate Cancer

Prostate cancer (PCa) has become the most frequent type of cancer in men. Recent data suggest that diabetic patients taking metformin have a lower incidence of certain cancer, including PCa. Metformin is the most common drug used in type II diabetes mellitus; its use has been shown to lower the incidence of several cancers, although there are ambiguous data about the anticancer activity of metformin. A large number of studies examined the potential antineoplastic mechanism of metformin although it is not still completely understood. This review summarizes the literature concerning the effects of metformin on PCa cells, highlighting its numerous mechanisms of action through which it can act. We analyze the possible causes of the discordances regarding the impact of metformin on risk of PCa; we discuss the latest findings in this field, suggesting that metformin may have a future role in the management of PCa both as monotherapy and in combination with other drugs.

Metformin therapy and risk of colorectal adenomas and colorectal cancer in type 2 diabetes mellitus patients: A systematic review and meta-analysis

Recent evidence indicates that metformin therapy may be associated with a decreased colorectal adenoma/colorectal cancer risk in type 2 diabetes patients. However, results are not consistent. We therefore performed a systematic review and meta-analysis to assess the association between metformin therapy and risk of colorectal adenomas/colorectal cancer in type 2 diabetes mellitus patients. We searched the literature published before Aug 31, 2016 in four databases: PubMed, Embase database, CNKI and VIP Library of Chinese Journal. Summary risk estimates (adjusted OR/adjusted RR/adjusted HR) with their 95% confidence interval (95% CI) were obtained using a random effects model. Twenty studies (including 12 cohort studies, 7 case-control studies and 1 randomized controlled trial study) were selected in terms of data of colorectal adenomas or colorectal cancer incidence. Metformin therapy was found to be associated with a decreased incidence of colorectal adenomas (unadjusted OR=0.80, 95% CI: 0.71-0.90, p=0.0002). When the adjusted data were analyzed, the summary estimate decreased to 25% reduction in colorectal adenomas risk (adjusted OR=0.75, 95% CI: 0.59-0.97, p=0.03). Besides, a significant reduction of colorectal cancer risk was also observed (unadjusted OR=0.73, 95% CI: 0.62-0.86, p=0.0002). And when the adjusted data were analyzed, colorectal cancer risk for metformin users was decreased with a reduction of 22%, compared with non-metformin users and other treatment users (adjusted OR=0.78, 95% CI: 0.70-0.87, p<0.00001). Our meta-analysis suggested that metformin therapy may be associated with a decreased risk of colorectal adenomas and colorectal cancer in type 2 diabetes mellitus patients.

Diabetes drugs and the incidence of solid cancers: a survey of the current evidence

INTRODUCTION

The evaluation of the relationship between the use of antidiabetic drug and the occurrence of cancer is extremely challenging, both from the clinical and pharmacoepidemiological standpoint. This narrative review described the current evidence supporting a relationship between the use of antidiabetic drugs and the incidence of solid cancers. Areas covered: Data from pharmacoepidemiological studies on cancer incidence were presented for the main antidiabetic drugs and drug classes, including human insulin and insulin analogues, metformin, sulfonylureas, glinides, alpha-glucosidase inhibitors, thiazolidinediones, incretin mimetics, and sodium glucose co-transporter 2 inhibitors. The relationship between the use of antidiabetics and the incidence of solid cancer was described in strata by any cancer and by organ-specific cancer and by drug and by drug classes. Information supporting biological evidence and putative mechanisms were also provided. Expert opinion: The history of exploration of the relationship between antidiabetic drugs and the risk of solid cancers has showed several issues. Unrecognized biases and misinterpretations of study results have had important consequences that delayed the identification of actual risk and benefits of the use of antidiabetic drugs associated with cancer occurrence or progression. The lesson learned from the past should address the future research in this area, since in the majority of cases findings are controversial and confirmatory studies are warranted.

Sex-dependent difference in the effect of metformin on colorectal cancer-specific mortality of diabetic colorectal cancer patients

AIM

To assess factors associated with the higher effect of metformin on mortality in diabetic colorectal cancer (CRC) patients, since the factors related to the effectiveness of metformin have not been identified yet.

METHODS

Between January 2000 and December 2010, 413 patients diagnosed with both stage 3/4 CRC and diabetes mellitus were identified. Patients’ demographics and clinical characteristics were analyzed. The effect of metformin on CRC-specific mortality and the interactions between metformin and each adjusted factor were evaluated.

RESULTS

Total follow-up duration was median 50 mo (range: 1-218 mo). There were 85 deaths (45.9%) and 72 CRC-specific deaths (38.9%) among 185 patients who used metformin, compared to 130 total deaths (57.0%) and 107 CRC-specific deaths (46.9%) among 228 patients who did not use metformin. In multivariate analysis, survival benefit associated with metformin administration was identified (HR = 0.985, 95%CI: 0.974-0.997, P = 0.012). Interaction test between metformin and sex after adjustment for relevant factors revealed that female CRC patients taking metformin exhibited a significantly lower CRC-specific mortality rate than male CRC patients taking metformin (HR = 0.369, 95%CI: 0.155-0.881, P = 0.025). Furthermore, subgroup analysis revealed significant differences in CRC-specific mortality between the metformin and non-metformin groups in female patients (HR = 0.501, 95%CI: 0.286-0.879, P = 0.013) but not male patients (HR = 0.848, 95%CI: 0.594-1.211, P = 0.365). There were no significant interactions between metformin and other adjusted factors on CRC-specific mortality.

CONCLUSION

We showed a strong sex-dependent difference in the effect of metformin on CRC-specific mortality in advanced stage CRC patients with diabetes.

Enemies or weapons in hands: investigational anti-diabetic drug glibenclamide and cancer risk

Epidemiological evidence suggests that diabetes is associated with elevated cancer risk through the actions of hyperglycemia, hyperinsulinemia and chronic inflammation. Metformin, a first-line medication for type 2 diabetes mellitus, arouses growing concerns on its anti-cancer effect. However, data regarding the effect of glibenclamide on tumor growth and cancer risk are less consistent, which may be a potential anti-cancer drug. Areas covered: In this review, we clarified probable underlying mechanisms in preclinical studies and reviewed epidemiological evidence on glibenclamide's cancer risk in clinical studies. Glibenclamide inhibited carcinogenesis through ATP-binding cassette protein super-family and ATP-sensitive potassium channels, while majority of clinical researches reported an increased or non-significant elevated cancer risk of glibenclamide users compared with metformin users. Other sulfonylureas and diarylsulfonylureas were also briefly introduced. Expert opinion: The inconsistency between the results of studies was probably ascribed to undiscovered mechanisms, confounding factors, inconsistent comparators and publication bias. Existing clinical trials were prone to be afflicted by time-related bias including immortal time bias, time-window bias, and time-lag bias. Glibenclimiade could be a promising and well-tolerated anti-neoplastic drug targeting ATP-binding cassette protein super-family and KATP channels, but its efficacy still needs to be proven in well-designed long-term randomized controlled clinical trials.

Metformin and lung cancer risk in patients with type 2 diabetes mellitus

This study evaluated whether metformin might reduce lung cancer risk. The reimbursement database of the Taiwan's National Health Insurance was used. A sample of 15414 never users and 280159 ever users of metformin (original sample) and a 1:1 matched-pairs of ever and never users (n=15414 in each group, matched sample) were recruited from patients with newly diagnosed type 2 diabetes mellitus during 1999-2005. They were followed until December 31, 2011. Cox regression incorporated with the inverse probability of treatment weighting using propensity score was used to estimate hazard ratios. Results showed that the respective incidence of lung cancer in ever and never users was 173.36 and 292.65 per 100000 person-years in the original sample; and was 211.71 and 292.65, respectively, in the matched sample. The overall hazard ratios (95% confidence intervals) of 0.586 (0.509-0.674) in the original sample and 0.717 (0.584-0.881) in the matched sample suggested a significantly lower risk among metformin users. Hazard ratios comparing the first (<22.60 months), second (22.60-46.67 months) and third (>46.67 months) tertile of cumulative duration of metformin use to never users was 1.163 (1.005-1.348), 0.612 (0.526-0.711) and 0.176 (0.148-0.210), respectively, in the original sample; and was 1.465 (1.131-1.897), 0.758 (0.566-1.016) and 0.228 (1.460-0.357) in the respective tertile of the matched sample. Sensitivity analyses after excluding patients with certain risk factors of cancer and subgroup analyses supported a favorable effect of metformin. In conclusion,metformin use may reduce lung cancer risk in patients with type 2 diabetes mellitus.

Metformin and esophageal cancer risk in Taiwanese patients with type 2 diabetes mellitus

This study evaluated whether metformin might reduce esophageal cancer risk. Patients with type 2 diabetes mellitus diagnosed during 1999-2005 were recruited from the reimbursement database of Taiwan's National Health Insurance. Those newly treated with metformin (n = 288013, "ever users of metformin") or other antidiabetic drugs (n = 16216, "never users of metformin") were followed until December 31, 2011. Sensitivity analyses were conducted in a matched-pair sample of 16216 never users and 16216 ever users. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. The risk associated with infection of Helicobacter pylori, Epstein-Barr virus, hepatitis B virus and hepatitis C virus was also evaluated. Results showed that the incidence of esophageal cancer in ever and never users was 25.03 and 50.87 per 100,000 person-years, respectively. The overall hazard ratio (95% confidence intervals) of 0.487 (0.347-0.684) suggested a significantly lower risk among metformin users. Hazard ratios comparing the first (< 21.47 months), second (21.47-46.00 months) and third (> 46.00 months) tertile of cumulative duration of metformin use to never users was 1.184 (0.834-1.680), 0.403 (0.276-0.588) and 0.113 (0.071-0.179), respectively. Infection of Helicobacter pylori (but not the other viral infections) significantly increased the risk, which could be ameliorated by metformin. Analyses in the matched sample consistently supported a protective role of metformin. In conclusion, metformin reduces esophageal cancer risk when the cumulative duration is more than approximately 2 years.

Rosiglitazone reduces breast cancer risk in Taiwanese female patients with type 2 diabetes mellitus

This study investigated whether rosiglitazone may affect breast cancer risk in female patients with type 2 diabetes mellitus in Taiwan. The reimbursement database of all female patients with type 2 diabetes mellitus under oral antidiabetic agents or insulin from 1996 to 2009 was retrieved from the National Health Insurance. An entry date was set on 1 January 2006 and a total of 431447 patients were followed up for breast cancer incidence till the end of 2009. Incidences for ever users, never users and subgroups of rosiglitazone dose-response parameters (tertile cutoffs of cumulative duration and cumulative dose) were calculated and hazard ratios estimated by Cox regression. There were 53029 ever users and 378418 never users, respective numbers of incident breast cancer 410 (0.77%) and 3292 (0.87%), and respective incidence 217.53 and 249.12 per 100000 person-years. The overall hazard ratio was 0.889 (95% confidence interval: 0.797-0.992) in the fully adjusted model. Significantly lower risk was observed for the third tertiles of cumulative duration (> 14 months) and cumulative dose (> 1792 mg) while compared to never users, with respective adjusted hazard ratio of 0.815 (95% confidence interval: 0.682-0.973) and 0.815 (95% confidence interval: 0.682-0.974). Additionally, a significant interaction between metformin and rosiglitazone was observed. The lowest risk was seen in patients who used both drugs (hazard ratio 0.812, 95% confidence interval: 0.705-0.934). In conclusion, rosiglitazone reduces breast cancer risk in female patients with type 2 diabetes mellitus, which shows a significant interaction with metformin.

Hyperglycaemia-induced resistance to Docetaxel is negated by metformin: a role for IGFBP-2

The incidence of many common cancers varies between different populations and appears to be affected by a Western lifestyle. Highly proliferative malignant cells require sufficient levels of nutrients for their anabolic activity. Therefore, targeting genes and pathways involved in metabolic pathways could yield future therapeutics. A common pathway implicated in energetic and nutritional requirements of a cell is the LKB1/AMPK pathway. Metformin is a widely studied anti-diabetic drug, which improves glycaemia in patients with type 2 diabetes by targeting this pathway. We investigated the effect of metformin on prostate cancer cell lines and evaluated its mechanism of action using DU145, LNCaP, PC3 and VCaP prostate cancer cell lines. Trypan blue dye-exclusion assay was used to assess levels of cell death. Western immunoblotting was used to determine the abundance of proteins. Insulin-like growth factor-binding protein-2 (IGFBP-2) and AMPK genes were silenced using siRNA. Effects on cell morphology were visualised using microscopy. IGFBP-2 gene expression was assessed using real-time RT-PCR. With DU145 and LNCaP cells metformin alone induced cell death, but this was reduced in hyperglycaemic conditions. Hyperglycaemia also reduced the sensitivity to Docetaxel, but this was countered by co-treatment with metformin. LKB1 was required for the activation of AMPK but was not essential to mediate the induction of cell death. An alternative pathway by which metformin exerted its action was through downregulation of IGFBP-2 in DU145 and LNCaP cells, independently of AMPK. This finding could have important implications in relation to therapeutic strategies in prostate cancer patients presenting with diabetes.

Metformin may reduce oral cancer risk in patients with type 2 diabetes

BACKGROUND

Whether metformin use may affect the risk of oral cancer required further investigation.

METHODS

The reimbursement database of the National Health Insurance in Taiwan was used. Patients with type 2 diabetes mellitus at an onset age of 25-74 years during 1999-2005 and newly treated with either metformin (n = 288198, "ever users of metformin") or other antidiabetic drugs (n = 16263, "never users of metformin") were followed for at least 6 months for oral cancer until December 31, 2011. The treatment effect of metformin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression adjusted for propensity score (PS) or incorporated with the inverse probability of treatment weighting (IPTW) using PS.

RESULTS

The respective numbers of incident oral cancer in ever users and never users were 1273 (0.44%) and 119 (0.73%), with respective incidences of 92.7 and 163.6 per 100,000 person-years. The overall hazard ratios (95% confidence intervals) suggested a significantly lower risk [0.584 (0.483-0.707) for PS-adjusted model, and 0.562 (0.465-0.678) for IPTW model]. In tertile analyses, the PS-adjusted hazard ratios (95% confidence intervals) for the first (<21.5 months), second (21.5-45.9 months) and third (>45.9 months) tertile of cumulative duration were 1.403 (1.152-1.708), 0.557 (0.453-0.684) and 0.152 (0.119-0.194), respectively; and were 1.244 (1.024-1.511), 0.526 (0.429-0.645) and 0.138 (0.108-0.176), respectively, for IPTW.

CONCLUSIONS

Metformin may significantly reduce the risk of oral cancer, especially when the cumulative duration is more than 21.5 months.

A story of metformin-butyrate synergism to control various pathological conditions as a consequence of gut microbiome modification: Genesis of a wonder drug?

The most widely prescribed oral anti-diabetic agent today in the world today is a member of the biguanide class of drugs called metformin. Apart from its use in diabetes, it is currently being investigated for its potential use in many diseases such as cancer, cardiovascular diseases, Alzheimer's disease, obesity, comorbidities of diabetes such as retinopathy, nephropathy to name a few. Numerous in-vitro and in-vivo studies as well as clinical trials have been and are being conducted with a vast amount of literature being published every day. Numerous mechanisms for this drug have been proposed, but they have been unable to explain all the actions observed clinically. It is of interest that insulin has a stimulatory effect on cellular growth. Metformin sensitizes the insulin action but believed to be beneficial in cancer. Like -wise metformin is shown to have beneficial effects in opposite sets of pathological scenario looking from insulin sensitization point of view. This requires a comprehensive review of the disease conditions which are claimed to be affected by metformin therapy. Such a comprehensive review is presently lacking. In this review, we begin by examining the history of metformin before it became the most popular anti-diabetic medication today followed by a review of its relevant molecular mechanisms and important clinical trials in all areas where metformin has been studied and investigated till today. We also review novel mechanistic insight in metformin action in relation to microbiome and elaborate implications of such aspect in various disease states. Finally, we highlight the quandaries and suggest potential solutions which will help the researchers and physicians to channel their research and put this drug to better use.

Functional characterization of AMP-activated protein kinase signaling in tumorigenesis

AMP-activated protein kinase (AMPK) is a ubiquitously expressed metabolic sensor among various species. Specifically, cellular AMPK is phosphorylated and activated under certain stressful conditions, such as energy deprivation, in turn to activate diversified downstream substrates to modulate the adaptive changes and maintain metabolic homeostasis. Recently, emerging evidences have implicated the potential roles of AMPK signaling in tumor initiation and progression. Nevertheless, a comprehensive description on such topic is still in scarcity, especially in combination of its biochemical features with mouse modeling results to elucidate the physiological role of AMPK signaling in tumorigenesis. Hence, we performed this thorough review by summarizing the tumorigenic role of each component along the AMPK signaling, comprising of both its upstream and downstream effectors. Moreover, their functional interplay with the AMPK heterotrimer and exclusive efficacies in carcinogenesis were chiefly explained among genetically altered mice models. Importantly, the pharmaceutical investigations of AMPK relevant medications have also been highlighted. In summary, in this review, we not only elucidate the potential functions of AMPK signaling pathway in governing tumorigenesis, but also potentiate the future targeted strategy aiming for better treatment of aberrant metabolism-associated diseases, including cancer.

Metformin use and cervical cancer risk in female patients with type 2 diabetes

This study evaluated whether metformin may affect the risk of cervical cancer. The reimbursement databases of the Taiwan's National Health Insurance were used. Female patients with type 2 diabetes at an onset age of 25-74 years during 1999-2005 and newly treated with metformin (n=132971, "ever users of metformin") or other antidiabetic drugs (n=6940, "never users of metformin") were followed for at least 6 months until December 31, 2011. The treatment effect of metformin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. Analyses were also conducted in a 1:1 matched pair cohort based on 8 digits of propensity score. Results showed that the respective numbers of incident cervical cancer in ever users and never users were 438 (0.33%) and 38 (0.55%), with respective incidences of 68.29 and 121.38 per 100,000 person-years. The overall hazard ratio suggested a significantly lower risk in metformin users (0.558, 95% confidence intervals: 0.401-0.778). In tertile analyses, the hazard ratios (95% confidence intervals) for the first (<23.0 months), second (23.0-47.9 months) and third (>47.9 months) tertile of cumulative duration were 1.272 (0.904-1.790), 0.523 (0.366-0.747) and 0.109 (0.070-0.172), respectively. Findings were supported by the analyses in the matched cohort. In conclusion, metformin may significantly reduce the risk of cervical cancer, especially when the cumulative duration is more than 2 years.

Metformin reduces gastric cancer risk in patients with type 2 diabetes mellitus

This retrospective cohort study investigated whether metformin may reduce gastric cancer risk by using the reimbursement databases of the Taiwan's National Health Insurance. Patients with type 2 diabetes diagnosed during 1999-2005 and newly treated with metformin (n=287971, "ever users of metformin") or other antidiabetic drugs (n=16217, "never users of metformin") were followed until December 31, 2011. The effect of metformin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. Results showed that the respective numbers of incident gastric cancer in ever and never users were 759 (0.26%) and 89 (0.55%), with respective incidences of 55.26 and 122.53 per 100,000 person-years. The overall hazard ratio (95% confidence intervals) of 0.448 (0.359-0.558) suggested a significantly lower risk among ever users. In tertile analyses, hazard ratios (95% confidence intervals) for the first (＜21.47 months), second (21.47-45.97 months) and third (＞45.97 months) tertile of cumulative duration was 0.973 (0.773-1.224), 0.422 (0.331-0.537) and 0.120 (0.090-0.161), respectively, while compared to never users. In conclusion, metformin significantly reduces gastric cancer risk, especially when the cumulative duration is more than approximately 2 years.

Synergistic Benefit of Statin and Metformin in Gastrointestinal Malignancies

OBJECTIVES

To evaluate whether statin use influences gastrointestinal cancer prognosis in patients with diabetes mellitus (DM).

METHODS

We reviewed all DM patients diagnosed at Roswell Park Cancer Institute with emergent gastrointestinal malignancy (January 2003 to December 2010) (N = 222). Baseline demographic, clinical history, and cancer outcomes were documented. Overall survival (OS) and disease-free survival (DFS) comparisons across various treatment groups were assessed by Kaplan-Meier and Cox proportional hazards.

RESULTS

Use of statin, alone or in combination, was associated with improved OS and DFS (hazard ratio [HR] = 0.65, P = .06; HR = 0.60, P < .02). We report similar OS and DFS advantage among users of mono- or combined metformin therapy (HR = 0.55, P < .01; HR = 0.63, P < .02). Concomitant use of metformin and statin provided a synergistic OS and DFS benefit (HR = 0.42, P < .01; HR = 0.44, P < .01). Despite significant tobacco and alcohol use history, patients with upper gastrointestinal cancers derived enhanced cancer outcomes from this combination (HR = 0.34, P < .01; HR = 0.43, P < .02), while receiving a statin without metformin or metformin without a statin did not provide significant cancer-related benefits.

CONCLUSION

Use of statin and metformin provides a synergistic improvement in gastrointestinal malignancies outcomes.

Metformin as a Tool to Target Aging

Aging has been targeted by genetic and dietary manipulation and by drugs in order to increase lifespan and health span in numerous models. Metformin, which has demonstrated protective effects against several age-related diseases in humans, will be tested in the TAME (Targeting Aging with Metformin) trial, as the initial step in the development of increasingly effective next-generation drugs.

NK cell count and glucotransporter 4 (GLUT4) expression in subjects with type 2 diabetes and colon cancer

BACKGROUND

Type 2 diabetes (T2D) and colon cancer (CC) are numbered among the most common diseases in the world. The decreased activity of natural killer (NK) cells previously revealed in both mentioned pathological states may be correlated with impaired expression of GLUT4 as the major insulin-dependent glucose transporter in these cells.

METHODS

The aim of this study was to evaluate GLUT4 expression and NK cells number in subjects with T2D and/or CC in comparison with control group. We evaluated 78 individuals divided into four groups: (1) patients with CC and T2DM, (2) patients with CC, (3) patients with T2DM (4) healthy control. GLUT4 expression on the surface of NK cells was measured using flow cytometry and phenotyping of NK cell was performed by immunofluorescent method.

RESULTS

Subjects with diabetes had the highest GLUT4 expression (21.35 ± 7.2 %) in comparison with other groups (P < 0.01). The mean values of GLUT4 expression in group with CC and in patients with both T2D and CC were similar (1.4 ± 0.4 % vs 1.5 ± 1.0 %; respectively). These values were significantly lower than in control group (12.6 ± 2.9 %; P < 0.01). In patients with T2D and CC the number of NK cells (20.15 ± 6.6 %) was significantly higher than in other groups, i.e. in group with T2D (14.08 ± 5.7 %), in group with CC (9.21 ± 3.6 %) and in control group (9.48 ± 4.7 %), respectively (P < 0.01).

CONCLUSIONS

It seems that there is a need to pay more attention to the high incidence of colon cancer among patients with type 2 diabetes. Decreased GLUT4 expression observed on NK cells in patients with colon cancer may be responsible for dysfunction of these cells and the higher carcinogenic risk in type 2 diabetic subjects.

Metformin in combination with 5-fluorouracil suppresses tumor growth by inhibiting the Warburg effect in human oral squamous cell carcinoma

Cancer cells show enhanced glucose consumption and lactate production even in the presence of abundant oxygen, a phenomenon known as the Warburg effect, which is related to tumor proliferation, progression and drug-resistance in cancers. Hypoxia-inducible factor-1 (HIF-1) and several members of Phosphatidylinositol-4, 5-bisphosphate 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway positively contribute to the Warburg effect, whereas AMP activated protein Kinase (AMPK) acts as a negative regulator. Targeting the regulator molecules of Warburg effect might be a useful strategy to effectively kill cancer cells. Metformin was reported to be effective against various cancers as it inhibits cell proliferation by activating AMPK, and inhibiting mTOR and HIF-1α. Several studies suggested the efficacy of metformin with 5-fluorouracil (5-FU) against esophageal and colon cancer. In this study, we evaluated the efficacy of metformin and 5-FU combined therapy against human oral squamous cell carcinoma (OSCC) in vitro and in vivo. MTT assay and TUNEL assay revealed that metformin (4 mg/ml) and 5-FU (2.5 µg/ml) combination treatment effectively inhibited cell growth and induced apoptosis in OSCC cell lines (HSC2, HSC3 and HSC4) compared to either agent alone. Lactate colorimetric assay detected decreased level of lactate in the supernatants of metformin and 5-FU treated cells compared to cells treated with metformin or 5-FU. Western blot analysis showed marked downregulation of HIF-1α and mTOR expression, and upregulation of AMPKα in cells treated with metformin and 5-FU combination treatment. Combination therapy with metformin (200 mg/kg, i.p.) and 5-FU (10 mg/kg, i.p.) for 4 weeks (5 days/week) effectively reduced HSC2 tumor growth (77.6%) compared to metformin (59.9%) or 5-FU (52%) alone in nude mice. These findings suggest that metformin and 5-FU combined therapy could exert strong antitumor effect against OSCC through the inhibition of Warburg phenomenon in tumor cells.

Molecular targets of metformin antitumor action

Epidemiological studies have shown that metformin, a first line therapeutic agent for diabetes mellitus, reduced the risk of developing various malignancies. Several preclinical studies established some possible mechanisms of its anticancer effects. The primary effect of metformin action is a decrease in cell energy status, which activates AMP-activated kinase (AMPK), a cellular metabolic sensor. This event is followed by a decrease in serum concentrations of insulin and insulin growth factor I (IGF-I), the potent mitogens for cancer cells. In addition to the indirect mode of action, metformin may exhibit direct inhibitory effect on cancer cells by targeting mammalian target of rapamycin (mTOR) signaling and anabolic processes. This review gathers information on mechanisms of metformin antitumor activity, with special attention given to the impact of this antidiabetic drug on insulin/PI3K/mTOR and AMPK signaling. Furthermore, the factors required for this novel activity of metformin are discussed.

Phase 2 Trial of Metformin Combined With 5-Fluorouracil in Patients With Refractory Metastatic Colorectal Cancer

BACKGROUND

Observational and preclinical studies have suggested that metformin has antitumor effects in solid tumors, including colorectal cancer (CRC). However, the effects of metformin in CRC have not been tested in clinical trials.

PATIENTS AND METHODS

This was a single-center, single-arm phase 2 clinical trial where histologically confirmed CRC patients with measurable and progressing metastatic disease previously treated with 5-fluorouracil (5-FU), irinotecan, oxaliplatin, and an anti-epidermal growth factor receptor (if the tumor was RAS wild type) were enrolled to receive metformin 850 mg orally continuously 2 times a day plus 5-FU 425 mg/m² and leucovorin 50 mg intravenously weekly until disease progression, unacceptable toxicity, or withdrawal of consent. The primary end point was disease control rate at 8 weeks.

RESULTS

Among 50 patients included, 11 (22%) met the primary end point. The median progression-free survival was 1.8 months and the median overall survival 7.9 months. Analyzing only the 11 patients who experienced disease control at 8 weeks, their median progression-free survival was 5.6 months and their median overall survival was 16.2 months. There was a trend for prolonged median survival for obese patients (12.4 vs. 5.8 months) and those longer off 5-FU. The treatment was well tolerated; the main adverse effects were diarrhea, nausea, vomiting, and myelotoxicity.

CONCLUSION

Metformin and 5-FU showed an overall modest but intriguing activity in patients with refractory CRC in this phase 2 study. Some patients experienced long-term disease control. Further trials are needed to confirm these results, particularly in obese patients with CRC.

Colorectal Cancer Patient Characteristics, Treatment and Survival in Oman--a Single Center Study

BACKGROUND

Colorectal cancer is the most common gastrointestinal cancer in Oman with an increasing incidence. We here report the presenting features, treatment outcomes and survival in a University hospital in Oman and compare our data with regional and international studies.

MATERIALS AND METHODS

Medical records of patients with colorectal cancer were reviewed retrospectively between June 2000 and December 2013 and were followed until June 2014.

RESULTS

A total of 162 patients were diagnosed with colorectal cancer. The majority were males (58.6%), with a median age of 56 years. Rectum was involved in 29.6% of patients, followed by ascending and sigmoid colon. The majority of patients had stage III (42.6%) and stage IV (32.7%) disease at presentation. K-Ras status was checked for 79 patients, and 41 (51.9%) featured the wild type. Median relapse free survival was 22 months. Median overall survival for all patients was 43 months. Observed 5 year overall survival (OS) for stages I, II and III was 100%, 60% and 60% respectively. On Log rank univariate analysis, age, BMI, diabetes, hypertension, metformin use, stage, clinical nodal status for rectal cancer, pathological T and nodal status, site of metastasis, surgical intervention, chemotherapy, radiotherapy, chemotherapy regimen, no of cycles of chemotherapy, response, RFS, site of recurrence and administration of 2nd line chemotherapy were significant factors affecting OS. On Cox regression multivariate analysis none of the factors independently affected the OS.

CONCLUSIONS

The majority of patients present with advanced disease and at young age. The survival rates are comparable to the published regional and international literature.

Translating the Science of Aging into Therapeutic Interventions

Life and health span have been extended in experimental animals using drugs that are potentially translatable into humans. Considerable effort is needed beyond the usual steps in drug development to devise the models, and realistic preclinical and clinical trial strategies are required to advance these agents into clinical application. It will be important to focus on subjects who already have symptoms or are at imminent risk of developing disorders related to fundamental aging processes, to use short-term, clinically relevant outcomes, as opposed to long-term outcomes, such as health span or life span, and to validate endpoint measures so they are acceptable to regulatory agencies. Funding is a roadblock, as is shortage of investigators with combined expertise in the basic biology of aging, clinical geriatrics, and investigational new drug clinical trials. Strategies for developing a path from the bench to the bedside are reviewed for interventions that target fundamental aging mechanisms.

Combination of metformin and 5-aminosalicylic acid cooperates to decrease proliferation and induce apoptosis in colorectal cancer cell lines

BACKGROUND

The link between inflammation and cancer has been confirmed by the use of anti-inflammatory therapies in cancer prevention and treatment. 5-aminosalicylic acid (5-ASA) was shown to decrease the growth and survival of colorectal cancer (CRC) cells. Studies also revealed that metformin induced apoptosis in several cancer cell lines.

METHODS

We investigated the combinatory effect of 5-ASA and metformin on HCT-116 and Caco-2 CRC cell lines. Apoptotic markers were determined using western blotting. Expression of pro-inflammatory cytokines was determined by RT-PCR. Inflammatory transcription factors and metastatic markers were measured by ELISA.

RESULTS

Metformin enhanced CRC cell death induced by 5-ASA through significant increase in oxidative stress and activation of apoptotic machinery. Moreover, metformin enhanced the anti-inflammatory effect of 5-ASA by decreasing the gene expression of IL-1β, IL-6, COX-2 and TNF-α and its receptors; TNF-R1 and TNF-R2. Significant inhibition of activation of NF-κB and STAT3 transcription factors, and their downstream targets was also observed. Metformin also enhanced the inhibitory effect of 5-ASA on MMP-2 and MMP-9 enzyme activity, indicating a decrease in metastasis.

CONCLUSION

The current data demonstrate that metformin potentiates the antitumor effect of 5-ASA on CRC cells suggesting their potential use as an adjuvant treatment in CRC.

Metformin Is Associated With Slightly Reduced Risk of Colorectal Cancer and Moderate Survival Benefits in Diabetes Mellitus: A Meta-Analysis

To systematically assess the effect of metformin on colorectal cancer (CRC) risk and mortality in type 2 diabetes mellitus (T2DM) patients. We conducted a systematic search of PubMed, Web of Science, and the Cochrane Library databases for relevant articles before August 2015. Two investigators identified and extracted data independently. We adopted adjusted estimates to calculate summary estimates with 95% confidence interval (CI) using either a fixed-effects or a random-effects model. Subgroup and sensitivity analyses were conducted to evaluate the robustness of the pooled results. The risk of publication bias was assessed by examining funnel plot asymmetry as well as Begg test and Egger test. Fifteen studies on CRC incidence and 6 studies on CRC survival were finally included in our meta-analysis. The pooled odds ratio (OR) of observational studies illustrated that a slight 10% reduction of CRC incidence was associated with metformin use (OR = 0.90, 95% CI: 0.85-0.96). Furthermore, the pooled hazard ratio (HR) revealed an improved survival outcome for metformin users in CRC patients compared to nonusers (HR = 0.68, 95% CI: 0.58-081). There was no publication bias across studies. Our meta-analysis demonstrated that metformin therapy could slightly reduce CRC incidence and moderately improve the survival outcomes in patients with T2DM. More prospective studies are warranted to certify this protective association.

Use of metformin and risk of kidney cancer in patients with type 2 diabetes

BACKGROUND

The anticancer effect of metformin has been reported in the literature but requires additional confirmation in epidemiologic studies. With respect to kidney cancer scarce data are available. This study investigates whether metformin use in patients with type 2 diabetes mellitus (T2DM) might affect kidney cancer risk.

METHODS

The reimbursement database of the National Health Insurance in Taiwan was used. T2DM patients aged ≥ 40 years and newly treated with either metformin (n=171,753, "ever users of metformin") or other antidiabetic drugs (n=75,499, "never users of metformin") within 1998-2002 were followed for at least 6 months for kidney cancer until 31 December 2009. The treatment effect was estimated by Cox regression using propensity score weighting by inverse probability of treatment weighting approach. Hazard ratios were estimated for ever versus never users, and for tertiles of cumulative duration of metformin therapy.

RESULTS

During follow-up, 917 ever users and 824 never users developed kidney cancer, with respective incidence of 80.09 and 190.30 per 100,000 person-years. The hazard ratio (95% confidence intervals) for ever versus never users is 0.279 (0.254-0.307); and is 0.598 (0.535-0.668), 0.279 (0.243-0.321) and 0.104 (0.088-0.124), respectively, for the first, second, and third tertile of cumulative duration of <14.5, 14.5-45.8 and >45.8 months. In subgroup analyses, the lower risk of kidney cancer associated with metformin use is consistently observed in both sexes, and in patients with or without concomitant use of other antidiabetic drugs.

CONCLUSION

Metformin use is associated with a decreased risk of kidney cancer in patients with T2DM.

Dissecting the Mechanisms Underlying Unusually Successful Human Health Span and Life Span

Humans age at different rates and families with exceptional survival provide the opportunity to understand why some people age slower than others. Unique features exhibited by centenarians include a family history of longevity, compression of morbidity with resultant extension of health span, and biomarkers such as low-circulating insulin-like growth factor 1 (IGF-1) and elevated high-density lipoprotein (HDL) cholesterol levels. Given the rarity of the centenarian phenotype, it has not been surprising that the use of discovery methods that relied on common population single nucleotide polymorphisms (SNPs) to unlock the genetic determinants of exceptional longevity have not yielded significant results. Conversely, gene sequencing has resulted in discoveries of functional gene variants that support several of the centenarian phenotypes. These discoveries have led to the strategic developments of drugs that may delay aging and prolong health span.

An updated review on cancer risk associated with incretin mimetics and enhancers

Incretin-based therapies, including the use of incretin mimetics of glucagon-like peptide-1 receptor (GLP-1R) agonists and incretin enhancers of dipeptidyl-peptidase 4 (DPP-4) inhibitors, are widely used by clinicians for glucose lowering in patients with type 2 diabetes mellitus. These agents have benefits of a lower risk of hypoglycemia, being neutral for body weight for DPP-4 inhibitors and having a potential for weight reduction with GLP-1R agonists. They may also have a neutral or beneficial cardiovascular effect. Despite these benefits, an increased risk of cancer (especially pancreatic cancer and thyroid cancer) associated with incretin-based therapies has been reported. In this article, we reviewed related literature of experimental animal and observational human studies, clinical trials, and meta-analyses published until December 15, 2014. Current studies suggested a probable role of GLP-1R activation on the development of pancreatic cancer and thyroid cancer in rodents, but such an effect in humans is not remarkable due to the lower or lack of expression of GLP-1R on human pancreatic ductal cells and thyroid tissues. Findings in human studies are controversial and inconclusive. In the analyses of the US Food and Drug Administration adverse events reporting system, a significantly higher risk of pancreatic cancer was observed for GLP-1R agonists and DPP-4 inhibitors, but a significantly higher risk of thyroid cancer was only observed for GLP-1R agonists. Such a higher risk of pancreatic cancer or thyroid cancer could not be similarly demonstrated in other human observational studies or analyses of data from clinical trials. With regards to cancers other than pancreatic cancer and thyroid cancer, available studies supported a neutral association in humans. Some preliminary studies even suggested a potentially beneficial effect on the development of other cancers with the use of incretins. Based on current evidence, continuous monitoring of the cancer issues related to incretin-based therapies is required, even though the benefits may outweigh the potential cancer risk in the general patients with type 2 diabetes mellitus.

Metformin for primary colorectal cancer prevention in patients with diabetes: a case-control study in a US population

BACKGROUND

Emerging evidence from observational studies has suggested that metformin may be beneficial in the primary prevention of colorectal cancer (CRC). However, to the authors' knowledge, none of these studies was conducted in a US population. Because environmental factors such as Western diet and obesity are implicated in the causation of CRC, a large case-control study was performed to assess the effects of metformin on the incidence of CRC in a US population.

METHODS

MarketScan databases were used to identify diabetic patients with CRC. A case was defined as having an incident diagnosis of CRC. Up to 2 controls matched for age, sex, and geographical region were selected for each case. Metformin exposure was assessed by prescription tracking within the 12-month period before the index date. Conditional logistic regression was used to adjust for multiple potential confounders and to calculate adjusted odds ratios (AORs).

RESULTS

The mean age of the study participants was 55 years and 57 years, respectively, in the control and case groups (P = 1.0). Approximately 60% of the study participants were male and 40% were female in each group. In the multivariable model, any metformin use was associated with a 15% reduction in the odds of CRC (AOR, 0.85; 95% confidence interval, 0.76-0.95 [P = .007]). After adjusting for health care use, the beneficial effect of metformin was reduced to 12% (AOR, 0.88; 95% confidence interval, 0.77-1.00 [P = .05]). The dose-response analyses demonstrated no significant association with metformin dose, duration, or total exposure.

CONCLUSIONS

Metformin use appears to be associated with a reduced risk of developing CRC among diabetic patients in the United States.

Kazinol C from Broussonetia kazinoki activates AMP-activated protein kinase to induce antitumorigenic effects in HT-29 colon cancer cells

Kazinol C is a 1,3-diphenylpropane, obtained from Broussonetia kazinoki, that has been employed in folk medicine as an edema suppressant. It exerts beneficial effects in oxidative stress-related diseases, such as cancer. However, the molecular mechanism involved in the anticancer effects remains to be determined. AMP-activated protein kinase (AMPK) has emerged as a possible anticancer target molecule. The present study investigated the effect of kazinol C on AMPK activation as well as subsequent HT-29 colon cancer cell viability, apoptosis and migration. Kazinol C markedly induced AMPK phosphorylation and significantly attenuated HT-29 colon cancer cell growth and viability. Compound C, as a well‑known AMPK inhibitor, blocked the kazinol C-induced cell death, and stable transduction of dominant-negative (DN) AMPK in colon cancer cells also inhibited kazinol C-induced cell apoptosis. In addition, kazinol C inhibited HT-29 cell migration and anchorage-independent growth. AMPK inhibition using stable transduction with DN AMPK significantly abrogated the kazinol C-induced inhibition of cancer cell migration. Thus, AMPK is a critical and novel regulator of kazinol C-mediated cancer cell apoptosis and inhibition of migration, suggesting that AMPK is a prime cancer target.

Metformin reduces thyroid cancer risk in Taiwanese patients with type 2 diabetes

BACKGROUND

Whether metformin may affect thyroid cancer risk has not been studied. This study investigated the association between metformin use and thyroid cancer risk in Taiwanese patients with type 2 diabetes mellitus.

METHODS

The reimbursement databases of all diabetic patients from 1996 to 2009 were retrieved from the National Health Insurance. An entry date was set at 1 January 2006 and 1,414,723 patients with type 2 diabetes were followed for thyroid cancer incidence until the end of 2009. Incidences for ever-users, never-users and subgroups of metformin exposure using tertile cutoffs for cumulative duration of therapy and cumulative dose were calculated and adjusted hazard ratios were estimated by Cox regression. Additional sensitivity analyses were conducted.

RESULTS

There were 795,321 ever-users and 619,402 never-users, with respective numbers of incident thyroid cancer of 683 (0.09%) and 1,614 (0.26%), and respective incidence of 24.09 and 87.33 per 100,000 person-years. The overall fully adjusted hazard ratio (95% confidence interval) was 0.683 (0.598-0.780), and all categories of the dose-response parameters showed significantly lower risk with P-trends < 0.0001. The protective effect of metformin on thyroid cancer incidence was also supported by sensitivity analyses, disregarding age (< 50 or ≥ 50 years) and sex; and was not affected by excluding users of insulin, sulfonylurea, and insulin and/or sulfonylurea respectively, by previous diagnosis of other cancers or by potential detection examinations that might lead to differential diagnosis of thyroid cancer.

CONCLUSIONS

This study provides evidence for the first time that metformin use in patients with type 2 diabetes may reduce the risk of thyroid cancer.

Type 2 diabetes mellitus is associated with increased mortality in Chinese patients receiving curative surgery for colon cancer

BACKGROUND

We investigated the association between diabetes mellitus (DM) and the prognosis of patients with early colon cancer who had undergone curative surgery.

METHODS

From three national databases of patients in Taiwan, we selected a cohort of colon cancer patients who had been newly diagnosed with stage I or stage II colon cancer between January 1, 2004 and December 31, 2008 and had undergone curative surgery. We collected information regarding DM (type 2 DM only), the use of antidiabetic medications, other comorbidities, and survival outcomes. The colon cancer-specific survival (CSS) and the overall survival (OS) were compared between patients with and without DM.

RESULTS

We selected 6,937 colon cancer patients, among whom 1,371 (19.8%) had DM. The colon cancer patients with DM were older and less likely to receive adjuvant chemotherapy but had a similar tumor stage and grade, compared with colon cancer patients without DM. Compared with colon cancer patients without DM, patients with DM had significantly shorter OS (5-year OS: 71.0% vs. 81.7%) and CSS (5-year CSS: 86.7% vs. 89.2%). After adjusting for age, sex, stage, adjuvant chemotherapy, and comorbidities in our multivariate analysis, DM remained an independent prognostic factor for overall mortality (adjusted hazards ratio: 1.32, 95% confidence interval: 1.18-1.49), but not for cancer-specific mortality. Among the colon cancer patients who had received antidiabetic drug therapy, patients who had used insulin had significantly shorter CSS and OS than patients who had not.

CONCLUSION

Among patients who receive curative surgery for early colon cancer, DM is a predictor of increased overall mortality.

Metformin and cancer risk and mortality: a systematic review and meta-analysis taking into account biases and confounders

Treatment of diabetics with metformin is associated with decreased breast cancer risk in observational studies, but it remains unclear if this drug has clinical antineoplastic activity. In a recent presurgical trial, we found a heterogeneous effect of metformin on breast cancer proliferation (ki-67) depending upon insulin resistance (HOMA index). Here, we determined the associations of additional serum biomarkers of insulin resistance, tumor subtype, and drug concentration with ki-67 response to metformin. Two-hundred non-diabetic women were randomly allocated to metformin (850 mg/bid) or placebo for 4 weeks prior to breast cancer surgery. The ki-67 response to metformin was assessed comparing data obtained from baseline biopsy (ki-67 and tumor subtype) and serum markers (HOMA index, C-peptide, IGF-I, IGFBP-1, IGFBP-3, free IGF-I, hs-CRP, adiponectin) with the same measurements at definitive surgery. For patients with a blood sample taken within 24 h from last drug intake, metformin level was measured. Compared with placebo, metformin significantly decreased ki-67 in women with HOMA > 2.8, those in the lowest IGFBP-1 quintile, those in the highest IGFBP-3 quartile, those with low free IGF-I, those in the top hs-CRP tertile, and those with HER2-positive tumors. In women with HOMA index > 2.8, drug levels were positively correlated with the ki-67 decrease, whereas no trend was noted in women with HOMA < 2.8 (p-interaction = 0.07). At conventional antidiabetic doses, the effect of metformin on tumor ki-67 of non-diabetic breast cancer patients varies with host and tumor characteristics. These findings are relevant to design breast cancer prevention and treatment trials with metformin.

Metformin and cancer risk and mortality: a systematic review and meta-analysis taking into account biases and confounders

Previous meta-analyses have shown that the antidiabetic agent metformin is associated with reduced cancer incidence and mortality. However, this effect has not been consistently demonstrated in animal models and recent epidemiologic studies. We performed a meta-analysis with a focus on confounders and biases, including body mass index (BMI), study type, and time-related biases. We identified 71 articles published between January 1, 1966, and May 31, 2013, through Pubmed, ISI Web of Science (Science Citation Index Expanded), Embase, and the Cochrane library that were related to metformin and cancer incidence or mortality. Study characteristics and outcomes were abstracted for each study that met inclusion criteria. We included estimates from 47 independent studies and 65,540 cancer cases in patients with diabetes. Overall cancer incidence was reduced by 31% [summary relative risk (SRR), 0.69; 95% confidence interval (CI), 0.52-0.90], although between-study heterogeneity was considerable (I(2) = 88%). Cancer mortality was reduced by 34% (SRR, 0.66; 95% CI, 0.54-0.81; I(2) = 21%). BMI-adjusted studies and studies without time-related biases also showed significant reduction in cancer incidence (SRR, 0.82; 95% CI, 0.70-0.96 with I(2) = 76% and SRR, 0.90; 95% CI, 0.89-0.91 with I(2) = 56%, respectively), albeit with lesser magnitude (18% and 10% reduction, respectively). However, studies of cancer mortality and individual organ sites did not consistently show significant reductions across all types of analyses. Although these associations may not be causal, our results show that metformin may reduce cancer incidence and mortality in patients with diabetes However, the reduction seems to be of modest magnitude and not affecting all populations equally. Clinical trials are needed to determine if these observations apply to nondiabetic populations and to specific organ sites.

Cancer biology in diabetes

Diabetes is a serious metabolic disease that causes multiple organ dysfunctions. Recent evidence suggests that diabetes could contribute to the initiation and progression of certain cancers in addition to the classic diabetic complications. Furthermore, some of the drugs used clinically to treat patients with diabetes might affect cancer initiation, progression and mortality. The recent discovery of the possible anticancer effects of metformin, a classic antidiabetic drug, has led physicians and scientists to reconsider the interaction between diabetes and cancer. In the present review, we analyze recent reports in this field, and explore possible mechanistic links between diabetes and cancer biology.

Metformin may reduce bladder cancer risk in Taiwanese patients with type 2 diabetes

Whether metformin therapy affects bladder cancer risk in patients with type 2 diabetes mellitus (T2DM) has not been extensively investigated. The reimbursement databases of all Taiwanese patients with a new diagnosis of T2DM between 1998 and 2002 (n = 940,708) were retrieved from the National Health Insurance for follow-up of bladder cancer up to the end of 2009. Metformin was treated as a time-dependent variable, and of these patients, 532,519 were never-users and 408,189 were ever-users of metformin. A time-dependent approach was applied in the calculation of bladder cancer incidence and in the estimation of hazard ratios by Cox regression for ever-users, never-users, and subgroups of metformin exposure (using tertile cutoffs of cumulative duration of therapy and cumulative dose). During the study period, 1,847 (0.45%) metformin ever-users and 6,213 (1.17%) metformin never-users developed bladder cancer, representing an incidence of 72.03 and 189.22 per 100,000 person-years, respectively. The age-sex-adjusted and multivariable-adjusted hazard ratios (95% confidence intervals) for ever- versus never-users were 0.382 (0.360-0.405) and 0.600 (0.564-0.638), respectively. The multivariable-adjusted hazard ratios for the first, second, and third tertiles of cumulative duration of metformin therapy were 1.034 (0.954-1.120), 0.696 (0.632-0.766), and 0.258 (0.229-0.291), respectively (P trend <0.0001). Similarly, the multivariable-adjusted hazard ratios for the first, second, and third tertiles of cumulative dose of metformin were 0.997 (0.920-1.080), 0.615 (0.559-0.677), and 0.285 (0.253-0.321), respectively (P trend <0.0001). This study suggests that metformin use is associated with a decreased risk of bladder cancer in patients with T2DM.

Diabetes and gastric cancer: the potential links

This article reviews the epidemiological evidence linking diabetes and gastric cancer and discusses some of the potential mechanisms, confounders and biases in the evaluation of such an association. Findings from four meta-analyses published from 2011 to 2013 suggest a positive link, which may be more remarkable in females and in the Asian populations. Putative mechanisms may involve shared risk factors, hyperglycemia, Helicobacter pylori (H. pylori) infection, high salt intake, medications and comorbidities. Diabetes may increase the risk of gastric cancer through shared risk factors including obesity, insulin resistance, hyperinsulinemia and smoking. Hyperglycemia, even before the clinical diagnosis of diabetes, may predict gastric cancer in some epidemiological studies, which is supported by in vitro, and in vivo studies. Patients with diabetes may also have a higher risk of gastric cancer through the higher infection rate, lower eradication rate and higher reinfection rate of H. pylori. High salt intake can act synergistically with H. pylori infection in the induction of gastric cancer. Whether a higher risk of gastric cancer in patients with diabetes may be ascribed to a higher intake of salt due to the loss of taste sensation awaits further investigation. The use of medications such as insulin, metformin, sulfonylureas, aspirin, statins and antibiotics may also influence the risk of gastric cancer, but most of them have not been extensively studied. Comorbidities may affect the development of gastric cancer through the use of medications and changes in lifestyle, dietary intake, and the metabolism of drugs. Finally, a potential detection bias related to gastrointestinal symptoms more commonly seen in patients with diabetes and with multiple comorbidities should be pointed out. Taking into account the inconsistent findings and the potential confounders and detection bias in previous epidemiological studies, it is expected that there are still more to be explored for the clarification of the association between diabetes and gastric cancer.

A review on thiazolidinediones and bladder cancer in human studies

There is a concern of an increased risk of bladder cancer associated with the use of thiazolidinediones, a class of oral glucose-lowering drugs commonly used in patients with type 2 diabetes with a mechanism of improving insulin resistance. Human studies on related issues are reviewed, followed by a discussion on potential concerns on the causal inference in current studies. Pioglitazone and rosiglitazone are discussed separately, and findings from different geographical regions are presented. Randomized controlled trials designed for primarily answering such a cancer link are lacking, and evidence from clinical trials with available data for evaluating the association may not be informative. Observational studies have been reported with the use of population-based administrative databases, single-hospital records, drug adverse event reporting system, and case series collection. Meta-analysis has also been performed by six different groups of investigators. These studies showed a signal of higher risk of bladder cancer associated with pioglitazone, especially at a higher cumulative dose or after prolonged exposure; however, a weaker signal or null association is observed with rosiglitazone. In addition, there are some concerns on the causal inference, which may be related to the use of secondary databases, biases in sampling, differential detection, and confounding by indications. Lack of full control of smoking and potential biases related to study designs and statistical approaches such as prevalent user bias and immortal time bias may be major limitations in some studies. Overlapping populations and opposing conclusions in studies using the same databases may be of concern and weaken the reported conclusions of the studies. Because randomized controlled trials are expensive and unethical in providing an answer to this cancer issue, observational studies are expected to be the main source in providing an answer in the future. Furthermore, international comparison studies using well-designed and uniform methodology to clarify the risk in specific sexes, ethnicities, and other subgroups and to evaluate the interaction with other environmental risk factors or medications will be helpful to identify patients at risk.

Rosiglitazone may reduce thyroid cancer risk in patients with type 2 diabetes

BACKGROUND

Whether rosiglitazone use in patients with type 2 diabetes may affect thyroid cancer risk has not been investigated.

METHODS

The reimbursement databases of all diabetic patients under oral anti-diabetic agents or insulin from 1996 to 2009 were retrieved from the National Health Insurance of Taiwan. An entry date was set at 1 January 2006, and 887,665 patients with type 2 diabetes were followed for thyroid cancer incidence until the end of 2009 for ever-users, never-users, and subgroups of rosiglitazone exposure using tertile cut-offs for time since starting rosiglitazone, duration of therapy, and cumulative dose. Hazard ratios were estimated by Cox regression.

RESULTS

There were 103,224 ever-users and 784,441 never-users, with respective numbers of incident thyroid cancer of 84 (0.08%) and 764 (0.10%), and respective incidence of 23.12 and 28.09 per 100,000 person-years. The overall multivariable-adjusted hazard ratio was not significant. However, in dose-response analyses, the adjusted hazard ratios (95% confidence intervals) were significant for the third tertile of duration of therapy (≥ 14 months) and cumulative dose (≥ 1,800 mg) for age ≥ 50 years: 0.53 (0.31-0.89) and 0.50 (0.29-0.87), respectively.

CONCLUSIONS

This study suggests that rosiglitazone use in patients with type 2 diabetes may reduce the risk of thyroid cancer.

Diabetes, insulin use, smoking, and pancreatic cancer mortality in Taiwan

The aim of the study was to evaluate the link between diabetes and pancreatic cancer (PC) mortality and the joint effect of smoking and insulin use on PC mortality. A total of 39,988 men and 46,909 women with type 2 diabetes, aged ≥25 years and recruited in 1995-1998, were followed to 2006 for PC mortality. Age-sex-specific mortality rate ratios for diabetic patients versus the general population were calculated. Cox regression was used to evaluate hazard ratios for PC mortality for covariates including age, sex, diabetes duration, body mass index, smoking, insulin use, and area of residence. The interaction and joint effect of smoking and insulin use were also evaluated. A total of 89 men and 63 women died of PC. The mortality rate ratios (95 % CI) showed a significantly higher risk in diabetic patients with a magnitude most remarkable at the youngest age: 1.51 (1.15, 1.98), 2.02 (1.35, 3.03), and 8.36 (5.39, 12.98) for ≥65, 55-64, and 25-54 years old, respectively, for men; and 1.16 (0.84, 1.59), 2.12 (1.39, 3.23) and 3.33 (1.14, 9.68), respectively, for women. In multivariable Cox regression analysis, only age was significantly predictive for PC mortality. Although smoking and insulin use might be associated with a 50 % higher risk when analyzed as individual risk factors, they did not reach statistical significance. The interaction term of smoking and insulin use was also not statistically significant in additional modeling. However, smoking and insulin use jointly increased the risk with an adjusted hazard ratio (95 % CI) of 3.04 (1.37, 6.73) when compared to patients who did not smoke and did not use insulin. Diabetic patients have a significantly higher risk of PC mortality. In patients with type 2 diabetes, smoking and insulin use may jointly increase the risk by threefold.

Antidiabetic medications and the risk of colorectal cancer in patients with diabetes mellitus: a systematic review and meta-analysis

BACKGROUND

Antidiabetic medications (ADM) may modify colorectal cancer risk in patients with diabetes mellitus. We performed a systematic review and meta-analysis, evaluating the effect of metformin, thiazolidinediones (TZD), sulfonylureas, and insulin on colorectal cancer risk in diabetic patients.

METHODS

We conducted a systematic search of multiple bibliographic databases, up to September 2012, for articles that evaluated exposure to metformin, TZD, sulfonylureas, and insulin, reported colorectal cancer risk in patients with diabetes mellitus, and reported OR or provided data for their estimation. Summary OR estimates with 95% confidence intervals (CI) were estimated using the random-effects model.

RESULTS

Fifteen studies reporting 13,871 cases of colorectal cancer in 840,787 patients with diabetes mellitus were included. Meta-analysis of observational studies showed an 11% reduction in colorectal cancer risk associated with metformin use (n = 9 studies; OR, 0.89; 95% CI, 0.81-0.99), whereas TZD use was not associated with colorectal cancer risk (n = 5 studies; OR, 0.96; 95% CI, 0.87-1.05). Conversely, a trend toward higher colorectal cancer risk was observed with sulfonylurea (n = 7 studies; OR, 1.11; 95% CI, 0.97-1.26) and insulin (n = 9 studies; OR, 1.33; 95% CI, 0.91-1.94) use, although these associations were not statistically significant. There was considerable heterogeneity across studies, partly explained by study location and adjustment for concomitant use of other ADMs. Post-hoc analysis of randomized controlled trials did not reveal any significant association between ADM and colorectal cancer risk.

CONCLUSIONS

Meta-analysis of published studies supports a protective association between metformin use and colorectal cancer risk in patients with diabetes mellitus.

IMPACT

Clinical trials on the chemopreventive effect of metformin against colorectal cancer are warranted.

The use of metformin and colorectal cancer incidence in patients with type II diabetes mellitus

BACKGROUND

Experimental studies have suggested that metformin may decrease the incidence of colorectal cancer in patients with type II diabetes. However, previous observational studies have reported contradictory results, which are likely due to important methodologic limitations. Thus, the objective of this study was to assess whether the use of metformin is associated with the incidence of colorectal cancer in patients with type II diabetes.

METHODS

A cohort study of patients newly treated with non-insulin antidiabetic agents was assembled using the United Kingdom Clinical Practice Research Datalink. A nested case-control analysis was conducted, where all incident cases of colorectal cancer occurring during follow-up were identified and randomly matched with up to 10 controls. Conditional logistic regression was used to estimate adjusted rate ratios (RR) of colorectal cancer associated with ever use, and cumulative duration of use of metformin. All models accounted for latency and were adjusted for relevant potential confounding factors.

RESULTS

Overall, ever use of metformin was not associated with the incidence of colorectal cancer [RR: 0.93; 95% confidence interval (CI), 0.73-1.18]. Similarly, no dose-response relationship was observed in terms of cumulative duration of use.

CONCLUSIONS

The use of metformin was not associated with the incidence of colorectal cancer in patients with type II diabetes.

IMPACT

The results of this study do not support the launch of metformin randomized controlled trials for the chemoprevention of colorectal cancer.

Diabetes and thyroid cancer mortality: a 12-year prospective follow-up of Taiwanese

BACKGROUND

The association between diabetes and thyroid cancer is rarely studied. This study evaluated thyroid cancer mortality trend in Taiwanese population, mortality rate ratios between diabetic patients and general population, and risk factors in diabetic patients.

METHODS

In general population, age-standardized trends were evaluated from 1995 to 2006. A total of 113,347 diabetic men and 131,573 diabetic women aged ≥ 25 years recruited during 1995-1998 were followed to 2006. Age- and sex-specific mortality rate ratios were calculated and Cox's regression evaluated the risk factors.

RESULTS

A steady trend of thyroid cancer mortality was observed in the general population. A total of 20 diabetic men and 45 diabetic women died of thyroid cancer, with overall mortality rate 2.32 and 4.26 per 100,000 person-years, respectively. Mortality rate ratios showed positive association with magnitude increased with decreasing age: 1.85 (0.77, 4.43), 1.21 (0.54, 2.73), 2.53 (1.14, 5.59) and 5.80 (2.10, 16.01) for ≥ 75, 65-74, 55-64 and 25-54 years old, respectively, for men; and 0.78 (0.35, 1.74), 2.03 (1.31, 3.13), 2.99 (1.77, 5.04) and 5.34 (2.20, 13.00), respectively, for women. After adjustment, only age was significantly associated with thyroid cancer mortality. Sex, diabetes duration, diabetes type, body mass index, smoking, insulin use and area of residence were not significantly predictive for thyroid cancer mortality.

CONCLUSIONS

The annual thyroid cancer mortality during 1995-2006 in the Taiwanese general population has been steady. Our data suggest a higher risk in diabetic patients, with especially higher mortality rate ratios in younger age. Obesity, smoking and insulin use are not modifiable risk factor.

Metformin and cancer

Type 2 diabetes mellitus is a rising cause of cardiovascular morbidity and mortality. A number of studies have also identified diabetic patients as having increased risk for the development of cancer. Metformin is a widely prescribed antidiabetic drug with an established efficacy coupled with a favorable safety profile and low cost. An increasing number of studies have associated metformin treatment with a decrease of cancer risk. Moreover, metformin has also been associated with improved outcomes in cancer patients. These possible pleiotropic effects of metformin may establish metformin as a cancer prevention and treatment option. However, any favorable effects of metformin on cancer are not always corroborated by clinical trials. Larger studies are expected to better investigate the possible antineoplastic effects of metformin.