Cohort study of insulin glargine and risk of breast, prostate, and colorectal cancer among patients with diabetes

Cancer biology in diabetes update: Focusing on antidiabetic drugs

The association of type 2 diabetes with certain cancer risk has been of great interest for years. However, the effect of diabetic medications on cancer development is not fully understood. Prospective clinical trials have not elucidated the long-term influence of hypoglycemic drugs on cancer incidence and the safety for cancer-bearing patients with diabetes, whereas numerous preclinical studies have shown that antidiabetic drugs could have an impact on carcinogenesis processes beyond the glycemic control effect. Because there is no evidence of the safety profile of antidiabetic agents on cancer biology, careful consideration would be required when prescribing any medicines to patients with diabetes and existing tumor. In this review, we discuss the potential influence of each diabetes therapy in cancer 'initiation', 'promotion' and 'progression'.

The prognostic outcome of 'type 2 diabetes mellitus and breast cancer' association pivots on hypoxia-hyperglycemia axis

Type 2 diabetes mellitus and breast cancer are complex, chronic, heterogeneous, and multi-factorial diseases; with common risk factors including but not limited to diet, obesity, and age. They also share mutually inclusive phenotypic features such as the metabolic deregulations resulting from hyperglycemia, hypoxic conditions and hormonal imbalances. Although, the association between diabetes and cancer has long been speculated; however, the exact molecular nature of this link remains to be fully elucidated. Both the diseases are leading causes of death worldwide and a causal relationship between the two if not addressed, may translate into a major global health concern. Previous studies have hypothesized hyperglycemia, hyperinsulinemia, hormonal imbalances and chronic inflammation, as some of the possible grounds for explaining how diabetes may lead to cancer initiation, yet further research still needs to be done to validate these proposed mechanisms. At the crux of this dilemma, hyperglycemia and hypoxia are two intimately related states involving an intricate level of crosstalk and hypoxia inducible factor 1, at the center of this, plays a key role in mediating an aggressive disease state, particularly in solid tumors such as breast cancer. Subsequently, elucidating the role of HIF1 in establishing the diabetes-breast cancer link on hypoxia-hyperglycemia axis may not only provide an insight into the molecular mechanisms underlying the association but also, illuminate on the prognostic outcome of the therapeutic targeting of HIF1 signaling in diabetic patients with breast cancer or vice versa. Hence, this review highlights the critical role of HIF1 signaling in patients with both T2DM and breast cancer, potentiates its significance as a prognostic marker in comorbid patients, and further discusses the potential prognostic outcome of targeting HIF1, subsequently establishing the pressing need for HIF1 molecular profiling-based patient selection leading to more effective therapeutic strategies emerging from personalized medicine.

Real-world evidence: the devil is in the detail

Much has been written about real-world evidence (RWE), a concept that offers an understanding of the effects of healthcare interventions using routine clinical data. The reflection of diverse real-world practices is a double-edged sword that makes RWE attractive but also opens doors to several biases that need to be minimised both in the design and analytical phases of non-experimental studies. Additionally, it is critical to ensure that researchers who conduct these studies possess adequate methodological expertise and ability to accurately implement these methods. Critical design elements to be considered should include a clearly defined research question using a causal inference framework, choice of a fit-for-purpose data source, inclusion of new users of a treatment with comparators that are as similar as possible to that group, accurately classifying person-time and deciding censoring approaches. Having taken measures to minimise bias 'by design', the next step is to implement appropriate analytical techniques (for example propensity scores) to minimise the remnant potential biases. A clear protocol should be provided at the beginning of the study and a report of the results after, including caveats to consider. We also point the readers to readings on some novel analytical methods as well as newer areas of application of RWE. While there is no one-size-fits-all solution to evaluating RWE studies, we have focused our discussion on key methods and issues commonly encountered in comparative observational cohort studies with the hope that readers are better equipped to evaluate non-experimental studies that they encounter in the future. Graphical abstract.

Similar Breast Cancer Risk in Women Older Than 65 Years Initiating Glargine, Detemir, and NPH Insulins

OBJECTIVE

To assess whether initiation of insulin glargine (glargine), compared with initiation of NPH or insulin detemir (detemir), was associated with an increased risk of breast cancer in women with diabetes.

RESEARCH DESIGN AND METHODS

This was a retrospective new-user cohort study of female Medicare beneficiaries aged ≥65 years initiating glargine (203,159), detemir (67,012), or NPH (47,388) from September 2006 to September 2015, with follow-up through May 2017. Weighted Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% CIs for incidence of breast cancer according to ever use, cumulative duration of use, cumulative dose of insulin, length of follow-up time, and a combination of dose and length of follow-up time.

RESULTS

Ever use of glargine was not associated with an increased risk of breast cancer compared with NPH (HR 0.97; 95% CI 0.88-1.06) or detemir (HR 0.98; 95% CI 0.92-1.05). No increased risk was seen with glargine use compared with either NPH or detemir by duration of insulin use, length of follow-up, or cumulative dose of insulin. No increased risk of breast cancer was observed in medium- or high-dose glargine users compared with low-dose users.

CONCLUSIONS

Overall, glargine use was not associated with an increased risk of breast cancer compared with NPH or detemir in female Medicare beneficiaries.

The systematic case-referent method

The systematic case-referent method is a special case-referent design originally developed for pharmacoepidemiologic research purposes. It consists in the systematic collection of series of incident cases of various disorders and the assembling of a general reference pool, from which "controls" are secondarily selected to be matched to specific cases. Both series are collected independently from each other and with no a priori hypothesis to be investigated. The reference pool can be either general or limited to a subpopulation, representative of the source population of the cases. Based on clinical recruitment of cases and referents, the design allows a very high specificity of diagnosis and documentation of clinical variables. All cases and referents are systematically documented on all treatments received before the incidence of the cases or before identification of referents. This documentation is done preferentially using objective sources assembled independently (linkage to claims data, medical records, pharmacy records, prescription records, hospital discharge letters). It can be completed with patients' interviews using standardised research tools, in particular for over-the-counter drug use and self-medication, and for the documentation of adherence to treatment and specific time-windows of exposure. Likewise, all cases and all referents are systematically documented on a series of risk factors, which are common to most epidemiological studies and are not hypothesis-dependent. Whenever the documentation of a confounding factor specific to the disease at hand is necessary, additional questionnaires can be applied to all or a sample of patients. The method has been successfully implemented for the pharmacoepidemiologic study of myocardial infarction, stroke, lupus, multiple sclerosis, rheumatoid arthritis, Guillain Barré syndrome, idiopathic thrombocytopenic purpura, type 1 diabetes mellitus, suicide attempts, breast cancer, and other disorders, for the analysis of the risk or preventing action of NSAIDs, statins, antiplatelet agents, anticoagulants, insulins, vaccines and other drugs.

Insulin glargine affects the expression of Igf-1r, Insr, and Igf-1 genes in colon and liver of diabetic rats

Objective(s):

The mitogenic effect of the analogous insulin glargine is currently under debate since several clinical studies have raised the possibility that insulin glargine treatment has a carcinogenic potential in different tissues. This study aimed to evaluate the Igf-1r, Insr, and Igf-1 gene expression in colon and liver of streptozotocin-induced diabetic rats in response to insulin glargine, neutral protamine Hagedorn (NPH) insulin, and metformin treatments.

Materials and Methods:

Male Wistar rats were induced during one week with streptozotocin to develop Type 2 Diabetes (T2D) and then randomly distributed into four groups. T2D rats included in the first group received insulin glargine, the second group received NPH insulin, the third group received metformin; finally, untreated T2D rats were included as the control group. All groups were treated for seven days; after the treatment, tissue samples of liver and colon were obtained. Quantitative PCR (qPCR) was performed to analyze the Igf-1r, Insr and Igf-1 gene expression in each tissue sample.

Results:

The liver tissue showed overexpression of the Insr and Igf-1r genes (P>0.001) in rats treated with insulin glargine in comparison with the control group. Similar results were observed for the Insr gene (P>0.011) in colonic tissue of rats treated with insulin glargine.

Conclusion:

These observations demonstrate that insulin glargine promote an excess of insulin and IGF-1 receptors in STZ-induced diabetic rats, which could overstimulate the mitogenic signaling pathways.

Thiazolidinedione therapy and breast cancer risk in diabetic women: A systematic review and meta-analysis

Rising experimental evidence suggests that thiazolidinediones (TZDs) exert a protective effect on breast cancer. However, studies concerning this issue were inconsistent and limited. Hence, we performed a meta-analysis with data from currently available studies to evaluate the effect of TZDs on breast cancer risk among diabetic women. We comprehensively searched for all pertinent studies addressing TZDs use and breast cancer risk published before January 1, 2016, in PubMed, Clinical Trials, and Cochrane Library. Data synthesis was performed in a random-effects model using Stata version 12.0 (Stata Corp, College Station, Texas). Fourteen independent studies were eventually selected in this meta-analysis, including 5 randomized controlled clinical trials (RCTs), 7 cohort studies, and 2 case-control studies. No significant associations of TZD use and risk of breast cancer were observed in the RCTs (pooled risk ratio [RR]: 0.77, 95% confidence interval (CI), 0.39-1.53, I²  = 26%) or case-control studies (pooled odds ratio, 0.99, 95% CI, 0.76-1.28, I²  = 31%). A 19% reduction in breast cancer risk (pooled RR: 0.81, 95% CI, 0.66-0.99, I²  = 72%) was found in the cohort studies. However, after removing the study with the smallest event number and the greatest effect size, the association became nonsignificant with greatly decreased heterogeneity (pooled RR: 0.94, 95% CI, 0.86-1.03, I²  = 16%). This meta-analysis did not find any significant association between TZDs use and risk of breast cancer among diabetic women.

Genome-Wide Analyses Identify Filamin-A As a Novel Downstream Target for Insulin and IGF1 Action

Insulin analogs were developed to improve diabetes therapy. However, certain modifications introduced into the insulin molecule were shown to enhance their affinity to the insulin-like growth factor-1 receptor (IGF1R). Most tumors, including endometrial cancers, express high levels of IGF1R. The present study was aimed at identifying the entire set of genes that are differentially activated by insulin glargine or detemir, in comparison to insulin and IGF1, in Type 1 and Type 2 endometrial cancer cell lines (ECC-1 and USPC-1, respectively). Global gene expression analyses demonstrated a ligand-dependent upregulated expression of filamin-A (FLNA), a gene that encodes an actin filament cross-linking protein, in both endometrial cancer cell types. Silencing experiments linked to migration assays confirmed the role of FLNA in cell growth and motility. Our data suggest that the activation of distinct sets of genes by glargine may lead to stimulation of specific pathways or, alternatively, may provide additive effects, different from those classically induced by insulin. Given that metastases are probably the main factor contributing to tumor invasiveness, the identification of FLNA as a downstream target for insulin-like hormones may be of translational relevance in oncology. Clinical studies in endometrial cancer may add further relevant information regarding the possible differential actions of insulin analogs with respect to native insulin.

Effects of insulin analogs and glucagon-like peptide-1 receptor agonists on proliferation and cellular energy metabolism in papillary thyroid cancer

Purpose

This study was aimed to investigate the expressions of the insulin receptor (IR), insulin-like growth factor receptor (IGF-1R), and glucagon-like peptide-1 receptor (GLP-1R) in normal thyroid tissue, papillary thyroid cancer (PTC) tissues, and PTC cells, and to examine the possible role of insulin analogs and GLP-1R agonists in cell proliferation and energy metabolism in PTC cells.

Methods

The expressions of IR, IGF-1R, and GLP-1R in PTC tissues and PTC cell lines were detected by immunohistochemistry and western blotting, respectively. Cell proliferation was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Levels of members of the phosphoinositol-3 kinase/AKT serine/threonine kinase (Akt) and mitogen-activated protein kinase/extracellular signal-regulated kinase (Erk) signaling pathways were measured by western blotting. Energy metabolism of PTC cell lines was analyzed using a Seahorse Extracellular Flux analyzer.

Results

Three receptors could be detected in both PTC tissues and PTC cell lines. Expressions of IGF-1R and GLP-1R were more obvious in PTC than in normal thyroid cells. Neither insulin, four insulin analogs, and two GLP-1R agonists showed significant effects on the proliferation of PTC cells, nor did they influence the levels of Akt/p-Akt and Erk/p-Erk. None of these antidiabetic agents could change the mitochondrial respiration and glycolysis levels in PTC cell lines.

Conclusion

Both PTC tissues and the PTC cell lines express IR, IGF-1R, and GLP-1R. However, insulin analogs and GLP-1R agonists, which are commonly used to treat patients with diabetes, may not influence cell proliferation, the phosphoinositol-3 kinase/Akt and mitogen-activated protein kinase/Erk pathways, or energy metabolism in PTC cells. For now, it is not necessary to avoid use of these antidiabetic agents in patients with PTC.

Long-Term Use of Long-Acting Insulin Analogs and Breast Cancer Incidence in Women With Type 2 Diabetes

Purpose

The association between long-acting insulin analogs and increased breast cancer risk is uncertain, particularly with the short follow-up in previous studies. We assessed this risk long term in women with type 2 diabetes.

Methods

A population-based cohort of women 40 years or older, all of whom were treated with long-acting (glargine, detemir) or neutral protamine Hagedorn (NPH) insulin between 2002 and 2012, was formed using the United Kingdom’s Clinical Practice Research Datalink. Women were followed until February 2015 or breast cancer diagnosis. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs) and 95% CIs of incident breast cancer, comparing long-acting insulin analogs with NPH overall, as well as by duration and cumulative dose.

Results

The cohort included 22,395 women who received insulin treatment, with 321 incident breast cancer events occurring during up to 12 years of follow-up (incidence rate 3.3 per 1,000 person-years). Compared with NPH insulin, insulin glargine was associated with an increased risk of breast cancer (HR, 1.44; 95% CI, 1.11 to 1.85), mainly increasing 5 years after glargine initiation (HR, 2.23; 95% CI, 1.32 to 3.77) and after > 30 prescriptions (HR, 2.29; 95% CI, 1.26 to 4.16). The risk was particularly elevated among prior insulin users (HR, 1.53; 95% CI, 1.10 to 2.12) but not for new users, which included fewer patients and for which one cannot rule out an HR of 1.81. The risk associated with insulin detemir was not significantly elevated (HR, 1.17; 95% CI, 0.77 to 1.77).

Conclusion

Long-term use of insulin glargine is associated with an increased risk of breast cancer in women with type 2 diabetes. The risk associated with insulin detemir remains uncertain because there are fewer users of this insulin.

Cancer risk among insulin users: comparing analogues with human insulin in the CARING five-country cohort study

AIMS/HYPOTHESIS

The aim of this work was to investigate the relationship between use of certain insulins and risk for cancer, when addressing the limitations and biases involved in previous studies.

METHODS

National Health Registries from Denmark (1996-2010), Finland (1996-2011), Norway (2005-2010) and Sweden (2007-2012) and the UK Clinical Practice Research Datalink database (1987-2013) were used to conduct a cohort study on new insulin users (N = 327,112). By using a common data model and semi-aggregate approach, we pooled individual-level records from five cohorts and applied Poisson regression models. For each of ten cancer sites studied, we estimated the rate ratios (RRs) by duration (≤0.5, 0.5-1, 1-2, 2-3, 3-4, 4-5, 5-6 and >6 years) of cumulative exposure to insulin glargine or insulin detemir relative to that of human insulin.

RESULTS

A total of 21,390 cancer cases occurred during a mean follow-up of 4.6 years. No trend with cumulative treatment time for insulin glargine relative to human insulin was observed in risk for any of the ten studied cancer types. Of the 136 associations tested in the main analysis, only a few increased and decreased risks were found: among women, a higher risk was observed for colorectal (RR 1.54, 95% CI 1.06, 2.25) and endometrial cancer (RR 1.78, 95% CI 1.07, 2.94) for ≤0.5 years of treatment and for malignant melanoma for 2-3 years (RR 1.92, 95% CI 1.02, 3.61) and 4-5 years (RR 3.55, 95% CI 1.68, 7.47]); among men, a lower risk was observed for pancreatic cancer for 2-3 years (RR 0.34, 95% CI 0.17, 0.66) and for liver cancer for 3-4 years (RR 0.36, 95% CI 0.14, 0.94) and >6 years (RR 0.22, 95% CI 0.05, 0.92). Comparisons of insulin detemir with human insulin also showed no consistent differences.

CONCLUSIONS/INTERPRETATION

The present multi-country study found no evidence of consistent differences in risk for ten cancers for insulin glargine or insulin detemir use compared with human insulin, at follow-up exceeding 5 years.

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.

Type 2 diabetes, insulin treatment and prognosis of breast cancer

BACKGROUND

The aim of our study was to investigate whether pre-existing type 2 diabetes and insulin therapy have an impact on the prognosis of breast cancer patients.

METHODS

We performed a retrospective analysis of 462 type 2 diabetic breast cancer patients and 1644 non-diabetic breast cancer patients treated in our institute from January 2005 to August 2010. Patients were divided by diabetes status and insulin use. The clinicopathological characteristics and clinical outcomes of patients within 5 years following breast cancer diagnosed were analysed.

RESULTS

Diabetic patients tended to have higher body mass index and higher histological grade tumours. Five-year disease-free survival and overall survival were reduced in diabetic patients (P < 0.001), and diabetes was an independent predictor for an increased risk of breast cancer relapse and death within 5 years (P < 0.001). Insulin treatment was associated with reduced 5-year disease-free survival and overall survival (P < 0.05); the risk of 5-year relapse and breast cancer mortality in the insulin group increased compared to that of non-insulin group after adjusting for age, tumour size, histological grade, oestrogen receptor, progesterone receptor, chemotherapy and hormone therapy (P < 0.05). After adjusting for age and other factors, the risk of breast cancer relapse was also increased in the insulin subgroup, while the risk of breast cancer mortality did not increase statistically.

CONCLUSIONS

Type 2 diabetes and insulin treatment might be independently associated with poorer prognosis of breast cancer. However, caution is needed when interpreting our results, and further investigations are needed. Copyright © 2016 John Wiley & Sons, Ltd.

Co-Managing Patients with Type 1 Diabetes and Cancer

The life expectancy of people with type 1 diabetes is improving and now approaches that of those without diabetes. As this population ages, a growing number will be diagnosed with and treated for cancer. Cancer treatments can drastically affect insulin requirement and glycemic control through multiple mechanisms including high doses of glucocorticoids and targeted therapies that directly interfere with cellular pathways involved in the action of insulin. Patients with cancer frequently also have alterations in gastrointestinal motility or appetite and require supplemental enteral or parenteral nutrition. Few studies have evaluated these patients directly, but data on patients with and without diabetes suggest that glycemic control may play a larger role in cancer outcomes than is often recognized. Collaboration between the treating oncologist and diabetologist allows people with diabetes to receive the most effective therapies for their cancers without undue risk of hypoglycemia or adverse outcomes due to hyperglycemia.

Insulin glargine use and breast cancer risk: Associations with cumulative exposure

BACKGROUND

This study was aimed to assess the risk of breast cancer associated with exposure to insulin glargine in women with type 2 diabetes and evaluate whether the pattern of risk concurs with the hypothesized trend of an increase in risk with longer duration of use, taking into account previous cumulative exposure to other types of insulin.

METHODS

We performed a restrospective cohort study (2002-2013) in the Clinical Practice Research Datalink among adult female patients with a first ever insulin prescription (n = 12 468). Time-dependent exposure measures were used to assess associations with duration of use of: (1) other insulin types before glargine was first prescribed (i.e. among switchers); and (2) of glargine during follow-up. Analyses were performed separately for insulin-naïve glargine users and patients switched to glargine. Cox proportional hazards models were used to derive p-trends, hazard ratios (HR) and 95% confidence intervals (CI) for breast cancer associated with glargine use.

RESULTS

During 66 151 person years, 186 breast cancer cases occurred; 76 in glargine users (3.0/1000 years) and 110 in users of other insulins (2.7/1000 years). Among insulin-naïve women, no association with cumulative glargine use was observed (p-trend = 0.91), even after ≥5 years (HR = 1.06, 95% CI 0.48-2.33). Among switchers, a linear trend with years of prior exposure to other insulins was found (p-trend = 0.02). An increased risk was observed in glargine users with extensive (>3 years) past exposure to other insulins (HR = 3.17, 95% CI 1.28-7.84). A non-significant trend with cumulative glargine exposure was found among switchers (p-trend = 0.24).

CONCLUSIONS

Exposure to glargine was not associated with an increased breast cancer risk in insulin-naïve patients. Exposure to other insulins prior to the start of glargine appears to be relevant when studying breast cancer risk associated with glargine use.

Effect of Long-Acting Insulin Analogs on the Risk of Cancer: A Systematic Review of Observational Studies

OBJECTIVE

Observational studies examining the association between long-acting insulin analogs and cancer incidence have produced inconsistent results. We conducted a systematic review of these studies, focusing on their methodological strengths and weaknesses.

RESEARCH DESIGN AND METHODS

We systematically searched MEDLINE and EMBASE from 2000 to 2014 to identify all observational studies evaluating the relationship between the long-acting insulin analogs and the risk of any and site-specific cancers (breast, colorectal, prostate). We included cohort and case-control studies published in English on insulin glargine and detemir and any cancer incidence among patients with type 1 or 2 diabetes. The methodological assessment involved the inclusion of prevalent users, inclusion of lag periods, time-related biases, and duration of follow-up between insulin initiation and cancer incidence.

RESULTS

A total of 16 cohort and 3 case-control studies met our inclusion criteria. All studies evaluated insulin glargine, and four studies also examined insulin detemir. Follow-up ranged from 0.9 to 7.0 years. Thirteen of 15 studies reported no association between insulin glargine and detemir and any cancer. Four of 13 studies reported an increased risk of breast cancer with insulin glargine. In the quality assessment, 7 studies included prevalent users, 11 did not consider a lag period, 6 had time-related biases, and 16 had short (<5 years) follow-up.

CONCLUSIONS

The observational studies examining the risk of cancer associated with long-acting insulin analogs have important methodological shortcomings that limit the conclusions that can be drawn. Thus, uncertainty remains, particularly for breast cancer risk.

Association of diabetes and diabetes treatment with incidence of breast cancer

AIMS

The aim of this study was to evaluate the association of diabetes and diabetes treatment with risk of postmenopausal breast cancer.

METHODS

Histologically confirmed incident cases of postmenopausal breast (N = 916) cancer were recruited from 23 Spanish public hospitals. Population-based controls (N = 1094) were randomly selected from primary care center lists within the catchment areas of the participant hospitals. ORs (95 % CI) were estimated using mixed-effects logistic regression models, using the recruitment center as a random effect term. Breast tumors were classified into hormone receptor positive (ER+ or PR+), HER2+ and triple negative (TN).

RESULTS

Diabetes was not associated with the overall risk of breast cancer (OR 1.09; 95 % CI 0.82-1.45), and it was only linked to the risk of developing TN tumors: Among 91 women with TN tumors, 18.7 % were diabetic, while the corresponding figure among controls was 9.9 % (OR 2.25; 95 % CI 1.22-4.15). Regarding treatment, results showed that insulin use was more prevalent among diabetic cases (2.5 %) as compared to diabetic controls (0.7 %); OR 2.98; 95 % CI 1.26-7.01. They also showed that, among diabetics, the risk of developing HR+/HER2- tumors decreased with longer metformin use (ORper year 0.89; 95 % CI 0.81-0.99; based on 24 cases and 43 controls).

CONCLUSION

This study reinforces the need to correctly classify breast cancers when studying their association with diabetes. Given the low survival rates in women diagnosed with TN breast tumors and the potential impact of diabetes control on breast cancer prevention, more studies are needed to better characterize this association.

Treatment with insulin (analogues) and breast cancer risk in diabetics; a systematic review and meta-analysis of in vitro, animal and human evidence

INTRODUCTION

Several studies have suggested that anti-diabetic insulin analogue treatment might increase cancer risk. The aim of this study was to review the postulated association between insulin and insulin analogue treatment and breast cancer development, and plausible mechanisms.

METHOD

A systematic literature search was performed on breast cell-line, animal and human studies using the key words 'insulin analogue' and 'breast neoplasia' in MEDLINE at PubMed, EMBASE, and ISI Web of Science databases. A quantitative and qualitative review was performed on the epidemiological data; due to a limited number of reported estimates, a meta-analysis was performed for glargine only. A comprehensive overview was composed for in vitro and animal studies. Protein and gene expression was analysed for the cell lines most frequently used in the included in vitro studies.

RESULTS

In total 16 in vitro, 5 animal, 2 in vivo human and 29 epidemiological papers were included. Insulin AspB10 showed mitogenic properties in vitro and in animal studies. Glargine was the only clinically available insulin analogue for which an increased proliferative potential was found in breast cancer cell lines. However, the pooled analysis of 13 epidemiological studies did not show evidence for an association between insulin glargine treatment and an increased breast cancer risk (HR 1.04; 95 % CI 0.91-1.17; p=0.49) versus no glargine in patients with diabetes mellitus. It has to be taken into account that the number of animal studies was limited, and epidemiological studies were underpowered and suffered from methodological limitations.

CONCLUSION

There is no compelling evidence that any clinically available insulin analogue (Aspart, Determir, Glargine, Glulisine or Lispro), nor human insulin increases breast cancer risk. Overall, the data suggests that insulin treatment is not involved in breast tumour initiation, but might induce breast tumour progression by up regulating mitogenic signalling pathways.

Alternative signaling network activation through different insulin receptor family members caused by pro-mitogenic antidiabetic insulin analogues in human mammary epithelial cells

Introduction

Insulin analogues are designed to have improved pharmacokinetic parameters compared to regular human insulin. This provides a sustained control of blood glucose levels in diabetic patients. All novel insulin analogues are tested for their mitogenic side effects, however these assays do not take into account the molecular mode of action of different insulin analogues. Insulin analogues can bind the insulin receptor and the insulin-like growth factor 1 receptor with different affinities and consequently will activate different downstream signaling pathways.

Methods

Here we used a panel of MCF7 human breast cancer cell lines that selectively express either one of the isoforms of the INSR or the IGF1R. We applied a transcriptomics approach to assess the differential transcriptional programs activated in these cells by either insulin, IGF1 or X10 treatment.

Results

Based on the differentially expressed genes between insulin versus IGF1 and X10 treatment, we retrieved a mitogenic classifier gene set. Validation by RT-qPCR confirmed the robustness of this gene set. The translational potential of these mitogenic classifier genes was examined in primary human mammary cells and in mammary gland tissue of mice in an in vivo model. The predictive power of the classifier genes was evaluated by testing all commercial insulin analogues in the in vitro model and defined X10 and glargine as the most potent mitogenic insulin analogues.

Conclusions

We propose that these mitogenic classifier genes can be used to test the mitogenic potential of novel insulin analogues as well as other alternative molecules with an anticipated affinity for the IGF1R.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0600-5) contains supplementary material, which is available to authorized users.

Assessing the effect of treatment duration on the association between anti-diabetic medication and cancer risk

Most studies that have evaluated the association between anti-diabetic medication and cancer risk have suffered from methodological drawbacks. To avoid time-related biases, we evaluated the effect of treatment duration on the cancer risk among naive users of anti-diabetic medication as compared to non-users. In addition, we addressed the influence of common risk factors such as smoking and BMI. The study population comprised 23,394 participants of FINRISK surveys. Data on cancer and anti-diabetic medication were linked with the study cohorts. We applied Lexis tabulation to the data and analyzed split records by using Poisson regression. Changes in cancer incidence in relation to treatment duration were examined by modeling the rate ratio (RR). After a median follow-up of 9 years, 53 cancer cases among users of anti-diabetic medication and 1,028 among non-users were diagnosed. No significant difference in cancer risk between users and non-users was observed after adjustment. The RR for all medication regardless of its duration was 1.01 [95% CI 0.75–1.33], and 1.37 [0.94–1.94] for period of 1–4 years. The results were similar for metformin, sulfonylurea, and insulin. This study demonstrates that evaluation of the variation in cancer risk in relation to treatment duration is of particular importance for enhancing the accuracy of conclusions on the link between exposure to anti-diabetic medication and cancer risk.

Importance of Beta Cell Function for the Treatment of Type 2 Diabetes

Type 2 diabetes (T2DM) is characterized by insulin resistance and beta cell dysfunction. Recent evidence has emerged that beta cell dysfunction is a common pathogenetic feature of both type 1 and type 2 diabetes, and T2DM never develops without beta cell dysfunction. Therefore, treatment of T2DM should aim to restore beta cell function. Although the treatment of T2DM has greatly improved over the past few decades, remaining issues in the current treatment of T2DM include (1) hypoglycemia; (2) body weight gain; (3) peripheral hyperinsulinemia and (4) postprandial hyperglycemia, which are all associated with inappropriate insulin supplementation, again underpinning the important role of endogenous and physiological insulin secretion in the management of T2DM. This review summarizes the current knowledge on beta cell function in T2DM and discusses the treatment strategy for T2DM in relation to beta cell dysfunction.