The influence of antidiabetic medications on the development and progression of prostate cancer

Drug Repurposing in Oncology: A Systematic Review of Randomized Controlled Clinical Trials

Quality pharmacological treatment can improve survival in many types of cancer. Drug repurposing offers advantages in comparison with traditional drug development procedures, reducing time and risk. This systematic review identified the most recent randomized controlled clinical trials that focus on drug repurposing in oncology. We found that only a few clinical trials were placebo-controlled or standard-of-care-alone-controlled. Metformin has been studied for potential use in various types of cancer, including prostate, lung, and pancreatic cancer. Other studies assessed the possible use of the antiparasitic agent mebendazole in colorectal cancer and of propranolol in multiple myeloma or, when combined with etodolac, in breast cancer. We were able to identify trials that study the potential use of known antineoplastics in other non-oncological conditions, such as imatinib for severe coronavirus disease in 2019 or a study protocol aiming to assess the possible repurposing of leuprolide for Alzheimer's disease. Major limitations of these clinical trials were the small sample size, the high clinical heterogeneity of the participants regarding the stage of the neoplastic disease, and the lack of accounting for multimorbidity and other baseline clinical characteristics. Drug repurposing possibilities in oncology must be carefully examined with well-designed trials, considering factors that could influence prognosis.

Antidiabetic Medications and the Risk of Prostate Cancer in Patients with Diabetes Mellitus: A Systematic Review and Meta-analysis

BACKGROUND

Antidiabetic medications (ADMs) may modify prostate cancer (PCa) risk in patients with diabetes mellitus (DM). Accordingly, the current study assessed the possible associations between ADMs and the risk of PCa in diabetics.

METHODS

A systematic literature search (PubMed, Embase and Cochrane Library) identified studies evaluating the associations between ADMs and incidence of PCa. A meta-analysis followed PRISMA was performed using odds ratio (OR) with 95% confidence interval (CI) as effect measures.

RESULTS

In total of 47 studies involving 3,094,152 patients with diabetes were included. Results of meta-analysis of the observational studies suggested no significant association between metformin, thiazolidinediones, sulfonylureas, insulin or dipeptidyl peptidase-4 inhibitors administration and the risk of PCa (All p-values > 0.05). Separate analysis of randomized controlled trials (RCTs) revealed a significant reduction in PCa risk with thiazolidinediones (OR = 0.55, p = 0.04) or glucagon-like peptide-1 receptor agonists (GLP-1RA) administration (OR = 0.53, p = 0.006), whereas no significant association was found in SGLT2 inhibitors (p = 0.3).

CONCLUSION

Thiazolidinediones or GLP-1RA administration may have benefits in PCa based on RCTs, however, further research is needed to confirm these findings.

Prostate Cancer-specific Survival After Radical Prostatectomy Is Improved Among Metformin Users but Not Among Other Antidiabetic Drug Users

Background

Metformin has been linked to improved survival among diabetic prostate cancer (PCa) patients, while hyperinsulinemia and insulin usage has been related to worse prognosis.

Objective

To evaluate the association of metformin and other antidiabetic drugs with PCa death and androgen deprivation therapy (ADT).

Design, setting, and participants

The study cohort included 14 424 men who underwent radical prostatectomy in Finland during 1995–2013. Cases were identified, and clinical data were collected from patient files and national registries using personal identification numbers.

Intervention

Information on the use of each antidiabetic drug during 1995–2014 was collected from prescription registry of the Social Insurance Institution of Finland.

Outcome measurements and statistical analysis

The risks of PCa death and initiation of ADT were analyzed by antidiabetic drug use with the Cox regression method. Each antidiabetic drug group was analyzed separately to model simultaneous usage. Pre- and postdiagnostic uses were analyzed separately.

Results and limitations

Prediagnostic use of antidiabetic drugs in general had no association with the risk of PCa death. Prediagnostic use of metformin was related to a reduced risk of ADT initiation (hazard ratio [HR] 0.75, 95% confidence interval [CI] 0.59–0.96), while high-dose insulin users had an increased risk. Overall, antidiabetic drug use after PCa diagnosis was associated with an elevated risk of PCa death. Only postdiagnostic metformin use was associated with reduced risks of PCa death (HR 0.47, 95% CI 0.30–0.76) and ADT initiation compared with nonusers. Study limitations are missing information on glycemic control, smoking, living or exercise habits, prostate-specific antigen, and Gleason score.

Conclusions

Among surgically treated PCa patients, use of metformin was associated with improved disease-specific survival, while insulin and insulin secretagogues were associated with poor survival. Metformin might be a favorable diabetes treatment among men with PCa.

Patient summary

In this Finnish nationwide study, we found that the risks of prostate cancer death and cancer progression are lowered among metformin users, but not among other antidiabetic drug users. Metformin might be a favorable treatment choice for diabetes in men with prostate cancer.

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.

The Effect of Metformin Use during Docetaxel Chemotherapy on Prostate Cancer Specific and Overall Survival of Diabetic Patients with Castration Resistant Prostate Cancer

PURPOSE

Docetaxel is the first line chemotherapy currently used to treat patients with symptomatic metastatic castration resistant prostate cancer. Although it provides survival benefits, it is associated with significant side effects. Novel therapeutic options are needed for patients with metastatic castration resistant prostate cancer and an approach is combining docetaxel with chemosensitizing agents. Metformin has been shown to improve the survival of patients with breast, lung and endometrial cancer receiving chemotherapy, and enhance chemotherapeutic efficacy in breast cancer and colon cancer cells. However, to our knowledge the chemosensitizing effect of metformin in prostate cancer has not been explored. Therefore, the hypothesis for our study was that diabetic patients with metastatic castration resistant prostate cancer who were administered metformin during docetaxel chemotherapy would have improved prostate cancer specific and overall survival.

MATERIALS AND METHODS

This retrospective cohort study used data from several Ontario administrative health care databases. Men older than 65 years diagnosed with metastatic castration resistant prostate cancer and treated with docetaxel were stratified into groups based on diabetes status and use of antidiabetic medications. We evaluated the effect of metformin use with docetaxel on prostate cancer specific survival and overall survival using Kaplan-Meier survival curves, the log rank test and multivariate Cox proportional HRs.

RESULTS

Survival curves showed that metformin use with docetaxel did not improve prostate cancer specific survival (p = 0.9562) or overall survival (p = 0.9927). HRs showed no significant effect of metformin use with docetaxel on prostate cancer specific survival (HR = 0.96, p = 0.66) or overall survival (HR = 0.94, p = 0.39).

CONCLUSIONS

Metformin use during docetaxel chemotherapy did not significantly improve prostate cancer specific or overall survival in diabetic patients with metastatic castration resistant prostate cancer. This study indicates that metformin may not be an effective chemosensitizer for metastatic castration resistant prostate cancer.

Warfarin use and prostate cancer risk in the Finnish Randomized Study of Screening for Prostate Cancer

OBJECTIVE

Anticoagulants, especially vitamin K antagonists (VKAs) such as warfarin, have been hypothesized to have antitumor properties, and use of VKAs has been associated with a lower prostate cancer (PCa) risk. This study estimated PCa risk among users of warfarin and other anticoagulants.

MATERIALS AND METHODS

All anticoagulant use among 78,615 men during 1995-2009 was analyzed. Cox regression, adjusted for age, screening trial arm and use of other medications, with medication use as a time-dependent variable, was used to estimate PCa risk overall, and by tumor grade and stage.

RESULTS

In total, 6537 men were diagnosed with PCa during 1995-2009 (1210 among warfarin users). Compared to non-users, warfarin use was associated with an increased risk of PCa [multivariable-adjusted hazard ratio (HR) = 1.11, 95% confidence interval (CI) 1.01-1.22]. This was limited to short-term, low-dose use, and was not observed in long-term use. A similar overall risk increase was observed for Gleason grade 7-10 PCa. Low-dose, short-term use of warfarin was associated with an increased risk of metastatic PCa. However, the increase in risk vanished with continued use. Compared to other anticoagulants, low-dose use of warfarin was associated with a slightly elevated overall PCa risk (HR = 1.19, 95% CI 1.00-1.43). The increase in risk disappeared in long-term, high-dose use.

CONCLUSIONS

This study, which included a larger number of PCa cases with warfarin exposure than previous studies, does not support previous notions of decreased risk of PCa among warfarin users. A similar risk of PCa was found among warfarin users and the general population, and no difference in risk was found between warfarin and other anticoagulants.

Association between metformin therapy and incidence, recurrence and mortality of prostate cancer: evidence from a meta-analysis

OBJECTIVE

Previous studies suggested that metformin is associated with decreased risk of cancer; however, results specifically addressing the potential association with prostate cancer were limited and contradictory. This study considers the association between metformin and the incidence, mortality and recurrence of prostate cancer by performing a meta-analysis of observational studies.

METHODS

Literatures published before January 2014 were searched by using databases of PubMed and Embase. Pooled relative risks (RRs) were determined using a random effects model to evaluate the strength of association between metformin therapy and risk of prostate cancer.

RESULTS

Thirteen studies involving a total of 334 532 participants were included in this meta-analysis. Compared with the control group, metformin therapy was associated with significantly decreased incidence of prostate cancer [RR = 0.88, 95% confidence interval (CI) [0.78, 0.99], p = 0.03, I(2)  = 74.7%]. However, metformin therapy was not associated with decreased all-cause mortality (RR = 1.07, 95% CI [0.86, 1.32], p = 0.55, I(2)  = 58.2%) or decreased recurrence of prostate cancer (RR = 0.90, 95% CI [0.75, 1.09], p = 0.27, I(2)  = 0.0%). No publication bias was detected (pBegg  = 0.55, pEgger  = 0.46).

CONCLUSIONS

The present study suggested that metformin therapy may decrease the incidence of prostate cancer but that there was no association between the treatment and all-cause mortality or recurrence. It is recommended that this finding should be considered carefully and confirmed with further studies.

Impact of metformin on clinical outcomes among men with prostate cancer: a systematic review and meta-analysis

BACKGROUND

Conflicting evidence exists regarding the beneficial effects of metformin in prostate cancer. To determine the association between metformin and clinical outcomes in prostate cancer using systematic review and meta-analysis.

METHODS

Original articles published in English until third week of July, 2014 were searched in electronic databases (Medline-Ovid, Scopus, The Cochrane Library, Web of Science, ProQuest) for studies on metformin use in prostate cancer. The clinical outcomes assessed were: development of biochemical recurrence, metastases or castration-resistant metastatic cancer, all-cause and prostate cancer-specific mortality. Meta-analysis was performed to calculate the pooled hazard ratio (pHR) and their 95% confidence interval (95% CI). Heterogeneity between the studies was examined using I2 statistics. Sensitivity analysis was conducted to assess the robustness of findings and publication bias was assessed by the Egger's regression asymmetry test and contour plot.

RESULTS

Out of 230 retrieved citations, eight retrospective cohort studies and one nested-case-control study met the inclusion criteria. Metformin use was marginally associated with reduction in the risk of biochemical recurrence (pHR: 0.82, 95% CI: 0.67, 1.01, P-value=0.06, I2=25%, five studies). Metformin use was not significantly associated with metastases (pHR: 0.59, 95% 0.30-1.18, P-value=0.14, I2=74%, three studies), all-cause mortality (pHR: 0.86; 95% CI, 0.67, 1.10, P-value=0.23, I2: 73%, six studies) and prostate cancer-specific mortality (pHR: 0.76, 95% CI: 0.43, 1.33, P-value = 0.33, I2=60%, four studies). Pooled estimates for all outcomes varied in sensitivity analysis by diabetes status and primary treatment of prostate cancer. Systematic review revealed mixed findings on metformin use and the risk of CRPC.

CONCLUSIONS

Metformin may reduce the risk of biochemical recurrence in prostate cancer. Given the potential of selection bias in the observational studies, randomized trials should be designed to assess the efficacy of metformin use in prostate cancer.

Targeting the 5'-AMP-activated protein kinase and related metabolic pathways for the treatment of prostate cancer

INTRODUCTION

Increasing evidence suggests that prostate cancer cells undergo unique metabolic reprogramming during transformation. A master regulator of cellular homeostasis, 5'-AMP-activated protein kinase (AMPK), directs metabolic adaptation that supports the growth demands of rapidly dividing cancer cells. The utilization of AMPK as a therapeutic target may therefore provide an effective strategy in the treatment of prostate cancer.

AREAS COVERED

Our review describes the regulation of AMPK by androgens and upstream kinases including the calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2) in prostate cancer. Oncogenic, AMPK-regulated pathways that direct various metabolic processes are also addressed. Furthermore, we discuss the role of AMPK in growth arrest and autophagy as a potential survival pathway for cancer cells. In addition, by regulating non-metabolic pathways, AMPK may stimulate migration and mitosis. Finally, this review summarizes efforts to treat prostate cancer with pharmacological agents capable of modulating AMPK signaling.

EXPERT OPINION

Current research is primarily focused on developing drugs that activate AMPK as a treatment for prostate cancer. However, oncogenic aspects of AMPK signaling calls for caution about employing such therapies. We think that inhibitors of CaMKK2 or AMPK, or perhaps the modulation of downstream targets of AMPK, will gain importance in the clinical management of prostate cancer.

Metabolic syndrome in the development and progression of prostate cancer

Prostate cancer (PCa) is the most common noncutaneous malignancy and second leading cause of cancer-specific mortality for men in the United States. There is a wide spectrum of aggressiveness ranging from biologically significant to indolent disease, which has led to an interest in the identification of risk factors for its development and progression. Emerging evidence has suggested an association between metabolic syndrome (MetS) and PCa. MetS represents a cluster of metabolic derangements that confer an increased risk of cardiovascular disease and type 2 diabetes mellitus. Its individual components include obesity, dyslipidemias, high blood pressure, and high fasting glucose levels. MetS has become pervasive and is currently associated with a high socioeconomic cost in both industrialized and developing countries throughout the world. The relationship between MetS and PCa is complex and yet to be fully defined. A better understanding of this relationship will facilitate the development of novel therapeutic targets for the prevention of PCa and improvement of outcomes among diagnosed men in the future. In this review, we evaluate the current evidence on the role of MetS in the development and progression of PCa. We also discuss the clinical implications on the management of PCa and consider the future direction of this subject.

Synergism between metformin and statins in modifying the risk of biochemical recurrence following radical prostatectomy in men with diabetes

BACKGROUND

To determine the effect of statins and metformin in combination on biochemical recurrence (BCR) among diabetic men undergoing radical prostatectomy (RP).

METHODS

Diabetic men undergoing RP at our institution from January 1995 to March 2012 were retrospectively reviewed. Recipients of adjuvant radiation or hormonal therapy were excluded. Statin and/or metformin use was determined through review of electronic records. BCR-free survival was plotted using Kaplan-Meier analysis, and the effect of statins and metformin on BCR was assessed via a multivariate Cox proportional hazards model.

RESULTS

Seven hundred and sixty-seven men met the inclusion criteria. Seventy-six (9.9%) were users of statins only, 56 (7.3%) were users of metformin only and 42 (5.5%) were dual users. Median follow-up time was 27 months. Dual users were less likely than nonusers or users of either medication alone to have a biopsy Gleason sum of 8-10 (P=0.033), and tended towards a lower rate of pathological T stage of pT3 or higher (P=0.064). Dual users had the highest 2-year and 5-year BCR-free survival, although this was not statistically significant (P=0.205). On multivariate regression, neither statin nor metformin use alone was significantly associated with BCR-free survival. However, their interaction led to a significantly lower BCR risk than would be expected from each medication's independent effects (hazard ratio=0.2; P=0.037).

CONCLUSIONS

The combination of statins and metformin in men undergoing RP for prostate cancer (PCa) may be associated with a lower BCR risk than would be predicted based on the independent effects of both medications. A synergism between these two agents is biologically plausible based on our current understanding of their diverse molecular pathways of action. The results of future clinical trials involving the use of either medication in men with PCa should be carefully assessed for confirmatory evidence of such a relationship.

Metformin significantly reduces incident prostate cancer risk in Taiwanese men with type 2 diabetes mellitus

BACKGROUND

Whether metformin therapy affects incident prostate cancer risk in Asian patients with type 2 diabetes mellitus (T2DM) has not been investigated.

METHODS

The National Health Insurance reimbursement database of Taiwanese male patients with new-onset T2DM between 1998 and 2002 and aged ⩾40years (n=395,481) were retrieved to follow up prostate cancer incidence until the end of 2009. Metformin was treated as a time-dependent variable. Of the patients studied, 209,269 were never-users and 186,212 were ever-users. A time-dependent approach was used to calculate prostate cancer incidence and estimate hazard ratios using Cox regression for ever-users, never-users and subgroups of metformin exposure (tertiles of cumulative duration and cumulative dose). Sensitivity analyses were conducted in various subgroups, using time-dependent and non-time-dependent approaches.

RESULTS

During the follow-up, 2776 metformin ever-users and 9642 never-users developed prostate cancer, representing an incidence of 239.42 and 737.10 per 100,000 person-years, respectively. The hazard ratio (95% confidence intervals) after adjustment for propensity score (PS) for ever- versus never-users was 0.467 (0.446-0.488). The PS-adjusted hazard ratios for the first, second and third tertiles of cumulative duration of metformin therapy were 0.741 (0.698-0.786), 0.474 (0.441-0.508) and 0.231 (0.212-0.253), respectively (P-trend<0.001); and were 0.742 (0.700-0.786), 0.436 (0.406-0.468) and 0.228 (0.208-0.251) for the respective cumulative dose (P-trend<0.001). Sensitivity analyses consistently supported a protective effect of metformin on incident prostate cancer.

CONCLUSIONS

Metformin use is associated with a decreased risk of incident prostate cancer in Taiwanese male patients with T2DM.

The use of metformin in patients with prostate cancer and the risk of death

BACKGROUND

Given the conflicting results from observational studies, we assessed whether the use of metformin after a prostate cancer diagnosis is associated with a decreased risk of cancer-specific and all-cause mortality.

METHODS

This study was conducted linking four databases from the United Kingdom. A cohort of men newly diagnosed with nonmetastatic prostate cancer with a history of treated type II diabetes, between April 1, 1998 and December 31, 2009, was followed until October 1, 2012. Nested case-control analyses were performed for cancer-specific mortality and all-cause mortality, in which exposure was defined as use of metformin during the time to risk-set. Conditional logistic regression was used to estimate adjusted rate ratios (RR) of each outcome with 95% confidence intervals (CI).

RESULTS

The cohort consisted of 935 men with prostate cancer and a history of type II diabetes. After a mean follow-up of 3.7 years, 258 deaths occurred, including 112 from prostate cancer. Overall, the post-diagnostic use of metformin was not associated with a decreased risk of cancer-specific mortality (RR, 1.09; 95% CI, 0.51-2.33). In a secondary analysis, a cumulative duration ≥938 days was associated with an increased risk (RR, 3.20; 95% CI, 1.00-10.24). The post-diagnostic use of metformin was not associated with all-cause mortality (RR, 0.79; 95% CI, 0.50-1.23).

CONCLUSION

The use of metformin after a prostate cancer diagnosis was not associated with an overall decreased risk of cancer-specific and all-cause mortality.

IMPACT

The results of this study do not support a role for metformin in the prevention of prostate cancer outcomes.

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.

Positive and negative effects of glitazones in carcinogenesis: experimental models vs. clinical practice

Diabetes increases cancer risk, which may be modulated by careful choice of treatment. Experimental reports showed efficacy of glitazones in various in vitro and in vivo models of carcinogenesis, but procarcinogenic effects in some models were reported too, and, similarly, data on cancer incidence in glitazone users are inconsistent. This review summarizes oncostatic effects of glitazones in preclinical and clinical studies and brings a brief summary of their impact on cancer risk in diabetic patients, with a focus on the association between pioglitazone use and bladder cancer.

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.

Metformin anti-tumor effect via disruption of the MID1 translational regulator complex and AR downregulation in prostate cancer cells

BACKGROUND

Metformin is an approved drug prescribed for diabetes. Its role as an anti-cancer agent has drawn significant attention because of its minimal side effects and low cost. However, its mechanism of anti-tumour action has not yet been fully clarified.

METHODS

The effect on cell growth was assessed by cell counting. Western blot was used for analysis of protein levels, Boyden chamber assays for analyses of cell migration and co-immunoprecipitation (CoIP) followed by western blot, PCR or qPCR for analysis of protein-protein and protein-mRNA interactions.

RESULTS

Metformin showed an anti-proliferative effect on a wide range of prostate cancer cells. It disrupted the AR translational MID1 regulator complex leading to release of the associated AR mRNA and subsequently to downregulation of AR protein in AR positive cell lines. Inhibition of AR positive and negative prostate cancer cells by metformin suggests involvement of additional targets. The inhibitory effect of metformin was mimicked by disruption of the MID1-α4/PP2A protein complex by siRNA knockdown of MID1 or α4 whereas AMPK activation was not required.

CONCLUSIONS

Findings reported herein uncover a mechanism for the anti-tumor activity of metformin in prostate cancer, which is independent of its anti-diabetic effects. These data provide a rationale for the use of metformin in the treatment of hormone naïve and castration-resistant prostate cancer and suggest AR is an important indirect target of metformin.

The effects of nonspecific HIF1α inhibitors on development of castrate resistance and metastases in prostate cancer

Expression of hypoxia-inducible factor (HIF)1α increases the risk of castrate-resistant prostate cancer (CRPC) and metastases in patients on androgen deprivation therapy (ADT) for prostate cancer (PC). We aimed to investigate the effects of nonspecific HIF1α inhibitors (Digoxin, metformin, and angiotensin-2 receptor blockers) on development of CRPC and metastases while on ADT. A retrospective review of prospectively collected medical records was conducted of all men who had continuous ADT as first-line therapy for CRPC at the Austin Hospital from 1983 to 2011. Association between HIF1α inhibitor medications and time to develop CRPC was investigated using actuarial statistics. Ninety-eight patients meeting the criteria were identified. Eighteen patients (21.4%) were treated with the nonspecific HIF1α inhibitors. Both groups had similar characteristics, apart from patients on HIF1α inhibitors being older (70 years vs. 63.9 years). The median CRPC-free survival was longer in men using HIF1α inhibitors compared to those not on inhibitors (6.7 years vs. 2.7 years, P = 0.01) and there was a 71% reduction in the risk of developing CRPC (HR 0.29 [95% CI 0.10-0.78] P = 0.02) after adjustment for Gleason score, age, and prostate-specific antigen (PSA). The median metastasis-free survival in men on HIF1α inhibitors was also significantly longer compared to those on no inhibitors (5.1 years vs. 2.6 years, P = 0.01) with an 81% reduction in the risk of developing metastases (HR 0.19 [CI 0.05-0.76] P = 0.02) after adjustment for Gleason score, age, and PSA. Nonspecific HIF1α inhibitors appear to increase the progression-free survival and reduce the risk of developing CRPC and metastases in patients on continuous ADT.

Metformin exposure and disseminated disease in patients with colorectal cancer

BACKGROUND

Preclinical evidence suggests a role for metformin in inhibiting tumour dissemination and metastasis. Previous studies have identified associations between metformin exposure and improved colorectal cancer survival. This study aimed to examine associations between metformin exposure and the odds of presenting with disseminated disease among colorectal cancer patients.

METHODS

Colorectal cancer patients diagnosed 2001-2006 were identified from the National Cancer Registry Ireland. A linked national pharmacy claims database was used to determine exposure to anti-diabetic medications prior to diagnosis. Multivariate logistic regression was used to estimate odds ratios (OR) with 95% confidence intervals (CI) for associations between metformin use (versus non-metformin anti-diabetic drugs) and odds of presenting with disseminated disease (lymph node positive/metastatic). Analyses were stratified by anti-diabetic drug co-prescription and intensity of metformin exposure.

RESULTS

The study population included 241 metformin-exposed diabetics, 129 non-metformin-exposed diabetics, and 4277 non-diabetic patients. In multivariate analysis, odds of disseminated disease were lower in metformin-exposed diabetics, compared with non-metformin-exposed diabetics, though not statistically significant (OR=0.66, 95% CI 0.39-1.12). In analyses stratified by metformin dosing intensity and anti-diabetic drug co-prescription, the odds were further from unity and approached significance in diabetics with high intensity, exclusive metformin use (OR=0.52, 95% CI 0.25-1.10).

CONCLUSIONS

While overall there was no statistically significant association between metformin exposure and disseminated colorectal cancer at diagnosis, there was a suggestion that high intensity, exclusive metformin use may be associated with reduced odds of disseminated disease. The number of patients in these subgroup analyses was small, and further investigation in larger studies is warranted.

Cancer cachexia and diabetes: similarities in metabolic alterations and possible treatment

Cancer cachexia is a metabolic syndrome featuring many alterations typical of type 2 diabetes (T2D). While muscle wasting is a hallmark of cachexia, epidemiological evidence also supports an accelerated age-related muscle loss in T2D. Insulin resistance manifests in both conditions and impairs glucose disposal and protein anabolism by tissues. A greater contribution of gluconeogenesis to glucose production may limit amino acid availability for muscle protein synthesis, further aggravating muscle loss. In the context of inter-dependence between glucose and protein metabolism, the present review summarizes the current state of knowledge on alterations that may lead to muscle wasting in human cancer. By highlighting the similarities with T2D, a disease that has been more extensively studied, the objective of this review is to provide a better understanding of the pathophysiology of cancer cachexia and to consider potential treatments usually targeted for T2D. Nutritional approaches aimed at stimulating protein anabolism might include specially formulated food with optimal protein and amino acid composition. Because the gradual muscle loss in T2D may be attenuated by diabetes treatment, anti-diabetic drugs might be considered in cachexia treatment. Metformin emerges as a choice candidate as it acts both on reducing gluconeogenesis and improving insulin sensitivity, and has demonstrated tumour suppressor properties in multiple cancer types. Such a multimodal approach to slow or reverse muscle wasting in cachexia warrants further investigation.

Human insulin does not increase prostate cancer risk in Taiwanese

BACKGROUND

Whether human insulin can increase the risk of prostate cancer is rarely studied.

PATIENTS AND METHODS

The reimbursement databases of all Taiwanese patients with diabetes from 1996 to 2009 were retrieved from the National Health Insurance databases of Taiwan. An entry date was set at January 1, 2004 and a total of 498,407 men with type 2 diabetes were followed for prostate cancer incidence until the end of 2009. Incidence for ever-users, never-users, and subgroups of human insulin exposure (using tertile cutoffs of time since starting insulin, cumulative dose, and cumulative duration of insulin) were calculated, and the age-adjusted and multivariable-adjusted hazard ratios were estimated using Cox regression.

RESULTS

There were 72,948 ever-users and 425,459 never-users, with respective numbers of incident prostate cancer of 768 (1.05%) and 6282 (1.48%), and respective incidence of 236.87 and 276.88 per 100,000 person-years. The overall hazard ratios (95% confidence intervals) indicated a significant negative association with insulin in the age-adjusted model (0.910; 0.843-0.981), but lack of association in the full model adjusted for multivariables (0.989; 0.912-1.072). The hazard ratios for the different categories of the dose-responsive parameters might show significantly lower risk with insulin use in the age-adjusted models, but none of the hazard ratios were significant in the full models.

CONCLUSION

This study suggests a lack of association between the use of human insulin and prostatic cancer risk in patients with type 2 diabetes after multivariable adjustment.

Association of diabetes mellitus and metformin use with biochemical recurrence in patients treated with radical prostatectomy for prostate cancer

PURPOSE

The impact of diabetes mellitus (DM) and metformin use on biochemical recurrence (BCR) in patients treated with radical prostatectomy (RP) remains controversial.

METHODS

We retrospectively evaluated 6,863 patients who underwent RP for clinically localized PC between 2000 and 2011. Univariable and multivariable Cox regression models addressed the association of DM and metformin use with BCR.

RESULTS

Overall, 664 patients had a diagnosis of DM from which 287 (43 %) were on metformin and 377 (57 %) were on anti-diabetics other than metformin. DM and metformin were not associated with any clinicopathologic features (p values >0.05). Within a median follow-up of 25 months (interquartile range 35 months), 774 (11.3 %) patients experienced BCR. Actuarial 5-year biochemical-free survival was 83 % for non-diabetic, 79 % for diabetic patients without metformin use, and 85 % for diabetic patients with metformin use (log rank p = 0.17). In uni- and multivariable Cox regression analyses with the non-diabetic group as referent, DM without metformin use (HR = 0.99; 95 % CI 0.75-1.30, p = 0.65) and DM with metformin use (HR = 0.84, 95 % CI 0.58-1.22, p = 0.36) were not associated with BCR after RP. A subgroup analysis stratified by nodal status, surgical margins, tumor stage, and Gleason sum did not reveal any significant association between DM, use of metformin and risk of BCR.

CONCLUSIONS

We found no association between DM or metformin use and cancer-specific features or BCR in patients treated with RP. The effect of DM and metformin on complications, wound healing and overall survival needs to be assessed in similar cohorts.

Metformin and sulfonylureas in relation to cancer risk in type II diabetes patients: a meta-analysis using primary data of published studies

INTRODUCTION

Accumulating evidence suggests that patients with type 2 diabetes mellitus (T2DM) and hyperinsulinemia are at increased risk for developing malignancies. It remains to be fully elucidated whether use of metformin, an insulin sensitizer, and/or sulfonylureas, insulin secretagogues, affect cancer incidence in subjects with T2DM.

MATERIAL & METHODS

We performed a meta-analysis using PubMed, of randomized control trials (RCTs), cohorts, and case-control studies published through July 2012 that assess effects of metformin and/or sulfonylurea sulfonylureas on cancer risk at any site, in subjects with T2DM. Fixed and random effects meta-analysis models were used, and the effect size was summarized as relative risk (RR) for RCTs/cohorts and as odds ratio (OR) for the case-control studies.

RESULTS

Analysis of 24 metformin studies in subjects with T2DM showed that metformin use is associated with reduced risk for the development of cancer, in both cohort (RR=0.70 [95% CI=0.67-0.73]) and case-control studies (OR=0.90 [95% CI=0.84-0.98]), but this finding was not supported by RCTs (RR=1.01[95% CI=0.81-1.26]). Data from 18 sulfonylurea studies in subjects with T2DM showed that sulfonylurea use is associated with an increase in all-cancer risk, in cohort studies (RR=1.55 [95% CI=1.48 -1.63]), though data from RCTs (RR=1.17 [95% CI=0.95-1.45]) and case-control studies (OR=1.02 [95% CI=0.93-1.13]) failed to demonstrate a statistically significant effect.

CONCLUSIONS

This analysis using pooled primary data demonstrates that metformin use reduces, while sulfonylurea use may be associated with an increased cancer risk in subjects with T2DM. These findings need to be confirmed in large-scale RCTs before they are translated into clinical practice.

Effect of metformin on prostate cancer outcomes after radical prostatectomy

OBJECTIVE

Recent studies have shown a relative risk reduction in the incidence of prostate cancer in patients taking metformin. However, there are conflicting findings on the effect of metformin on established cases of prostate cancer. In this study we evaluated the effect of metformin on survival and pathologic outcomes in established prostate cancer.

MATERIALS AND METHODS

We retrospectively identified 12,052 patients who underwent radical prostatectomy between 1997 and 2010 at Mayo Clinic. Among these, 885 (7.3%) were diabetics, including 323 taking and 562 not taking metformin. Kaplan-Meier method was utilized to calculate rates of biochemical recurrence (BCR), systemic progression (SP), and all-cause mortality (ACM). Cox models were used to estimate the metformin hazard ratio (HR) adjusted for clinical and pathologic variables.

RESULTS AND CONCLUSIONS

Median follow-up was 5.1 years. In univariate analysis, metformin HR (95% confidence intervals) was not significant for BCR (1.13 [0.84, 1.52]; P = 0.40), SP (1.37 [0.69, 2.72]; P = 0.37), and ACM (1.32 [0.84, 2.05]; P = 0.23). After adjusting for covariates of interest, the HRs for metformin among diabetics remained nonsignificant for BCR (0.91 [0.67, 1.24]; P = 0.55), SP (0.83 [0.39, 1.74]; P = 0.62); and ACM (1.16 [0.73, 1.86]; P = 0.53). No significant difference was seen between metformin users and nonusers in the final pathologic Gleason score (P = 0.33), stage (P = 0.1), rate of positive surgical margins (P = 0.29), or tumor volume (P = 0.76). Metformin use was not associated with a risk reduction in BCR, SP, or ACM. Besides presenting survival data, our results describing metformin's effect on final pathology are unique.

Metabolic syndrome as a peculiar target for management of prostate cancer patients

An interesting and reciprocal association between the metabolic syndrome and prostate cancer has been identified. Metabolic alterations, such as hyperinsulinemia, increased levels of insulin growth factor-1, and insulin resistance could be on the basis of development and progression of many tumors, including prostate cancer, and changes in body composition, in turn, can represent some side effects of androgen deprivation therapy and novel drugs, such as mammalian target of rapamycin inhibitors. This review evaluates this interrelation between metabolic syndrome and prostate tumor scanning in many clinical and preclinical epidemiological studies and describes possible pathogenetic biological mechanisms. Finally, this article discusses feasible clinical implications for the management, prevention, diagnosis, prognosis, and treatment of patients affected by metabolic syndrome and prostate cancer, with particular attention to the metformin action.

Association of metformin use with cancer incidence and mortality: a meta-analysis

PURPOSE

To assess the effect of metformin intake on cancer incidence and mortality.

METHODS

Original articles in English published until June 15, 2012 were searched for in electronic databases (MEDLINE, ISI Web of Science and EMBASE databases) and relevant reviews were examined. Meta-analysis was applied to calculate the summary relative risk (SRR) and their 95% confidence intervals (95% CI). Sensitivity analysis was conducted to assess the robustness of the pooled estimator. The risk of publication bias was assessed by the Egger regression asymmetry test.

RESULTS

According to the eligibility criteria, 37 studies comprising 1,535,636 participants, were selected in terms of intervention and data of cancer incidence or mortality. Among metformin users compared with non-users, the SRR for overall-cancer incidence was 0.73 (95% CI, 0.64-0.83) and that for mortality was 0.82 (95% CI, 0.76-0.89). The risk reductions for liver, pancreatic, colorectal and breast cancer incidence were 78%, 46%, 23% and 6%, respectively. Also, metformin can reduce the mortality of liver cancer (SRR, 0.23; 95% CI, 0.09-0.60) and breast cancer (SRR, 0.63; 95% CI, 0.40-0.99). No statistically significant association between metformin and prostate cancer incidence was found.

CONCLUSIONS

Metformin can reduce the incidence of overall cancer, liver cancer, pancreatic cancer, colorectal cancer and breast cancer as well as the mortality of overall cancer, liver cancer and breast cancer. No beneficial effect on prostate cancer incidence was found for meformin intake in the meta-analysis.

Diabetes mellitus and risk of prostate cancer: an updated meta-analysis based on 12 case-control and 25 cohort studies

The association between diabetes and risk of prostate cancer has been investigated widely. However, study results remain inconsistent and contradictory. Using a meta-analytic approach, the present study explore the relationship incorporating more recent studies and provide more powerful evidence without the limitations of any individual study. Relevant studies were identified by searching Pubmed and the Cochrane Central Register of Controlled Trials through May 18, 2012. The strength of the relationship between diabetes mellitus and risk of prostate cancer was assessed using relative risk (RR). Either a fixed effects or random effects model was used to calculate the pooled RRs. Stratification analyses and sensitivity analyses were conducted, and publication bias was assessed by Egger's test and Begg's test. Twelve case-control studies involving 9,767 cases and 19,790 controls, and 25 cohort studies involving 118,825 cases were included. The person-years of follow-up ranged from 29,963 to 6,264,890 among included cohort studies. Diabetes was not significantly associated with incidence of prostate cancer in our analysis of case-control studies only (RR = 0.846, 95 % CI [0.710, 1.009]) or that of cohort studies only (RR = 0.925, 95 % CI [0.811, 1.054]). However, through subgroup analyses, statistically significant associations between diabetes and prostate cancer were found when considering population-based studies only (RR = 0.719, 95 % CI [0.637, 0.812]), cohort studies conducted in the United States (RR = 0.789, 95 % CI [0.727, 0.857]), and studies with follow-up of more than 5 years. Compared to risk of prostate cancer among people without diabetes, diabetic patients using insulin treatment experienced reduced incidence of prostate cancer in both case-control and cohort studies. The results suggest that diabetes mellitus is associated with decreased incidence of prostate cancer, specifically in the population of the United States. In addition, the time since onset of diabetes was positively associated with decreasing incidence of prostate cancer. The present conclusions should be considered carefully, however, and confirmed with further studies.