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.

Classifying the adverse mitogenic mode of action of insulin analogues using a novel mechanism-based genetically engineered human breast cancer cell panel

Insulin analogues are widely used in clinical practice. Modifications on the insulin molecular structure can affect the affinity and activation towards two closely related receptor tyrosine kinases: the insulin receptor (INSR) and the insulin-like growth factor 1 receptor (IGF1R). A switch towards higher IGF1R affinity is likely to emphasize mitogenesis rather than glucose metabolism. Relevant well-validated experimental tools to address the insulin analogue activation of either INSR or IGF1R are missing. We have established a panel of human MCF-7 breast cancer cell lines either ectopically expressing the INSR (A or B isoform) in conjunction with a stable knockdown of the IGF1R or ectopically expressing the IGF1R in conjunction with a stable knockdown of the INSR. In these cell lines, we systematically evaluated the INSR and IGF1R receptor activation and downstream mitogenic signalling of all major clinical relevant insulin analogues in comparison with insulin and IGF1R. While most insulin analogues primarily activated the INSR, the mitogenic activation pattern of glargine was highly similar to IGF1 and insulin AspB10, known to bind IGF1R and induce carcinogenesis. Yet, in a long-term proliferation assay, the proliferative effect of glargine was not much different from regular insulin or other insulin analogues. This was caused by the rapid enzymatic conversion into its two metabolic active metabolites M1 and M2, with reduced mitogenic signalling through the IGF1R. In summary, based on our new cell models, we identified a similar mitogenic potency of insulin glargine and AspB10. However, rapid enzymatic conversion of glargine precludes a sustained activation of the IGF1R signalling pathway.

Contribution of bi-allelic germline MUTYH mutations to early-onset and familial colorectal cancer and to low number of adenomatous polyps: case-series and literature review

In the absence of a polyposis phenotype, colorectal cancer (CRC) patients referred for genetic testing because of early-onset disease and/or a positive family history, typically undergo testing for molecular signs of Lynch syndrome in their tumors. In the absence of these signs, DNA testing for germline mutations associated with other known tumor syndromes is usually not performed. However, a few studies in large series of CRC patients suggest that in a small percentage of CRC cases, bi-allelic MUTYH germline mutations can be found in the absence of the MUTYH-associated polyposis phenotype. This has not been studied in the Dutch population. Therefore, we analyzed the MUTYH gene for mutations in 89 patients with microsatellite-low or stable CRC cancer diagnosed before the age of 40 years or otherwise meeting the Bethesda criteria, all of them without a polyposis phenotype. In addition, we studied a series of 693 non-CRC patients with 1-13 adenomatous colorectal polyps for the MUTYH hotspot mutations Y179C, G396D and P405L. No bi-allelic MUTYH mutations were observed. Our data suggest that the contribution of bi-allelic MUTYH mutations to the development of CRC in Dutch non-polyposis patients that meet clinical genetic referral criteria, and to the development of low number of colorectal adenomas in non-CRC patients, is likely to be low.

Interleukin-9 polymorphism in infants with respiratory syncytial virus infection: an opposite effect in boys and girls

The predominance of severe respiratory syncytial virus (RSV) bronchiolitis in boys compared to girls is well known, but its mechanism is not yet understood. This is the first study focusing on gender-specific genetic factors affecting the risk of severe RSV infection using a previously described cohort. We determined 347 single-nucleotide polymorphisms (SNPs) in 470 children hospitalized for RSV infection, their parents, and 1,008 random population controls. We tested if these SNPs exerted a different effect in boys and girls by performing statistical interaction tests. Only one SNP (rs2069885) had a gender-specific significant association with RSV infection, severe enough to require hospitalization (P-value 0.00057). The major allele of this structural polymorphism in the interleukin (IL)-9 gene is associated with an increased susceptibility to severe RSV infection in boys, while there is a decreased susceptibility in girls. Haplotype analysis of two SNPs in the IL-9 gene (rs2069885 and rs1799962) showed overrepresentation of the TT haplotype in girls with severe RSV bronchiolitis requiring hospitalization indicating that this is the haplotype conferring the highest risk in girls. In conclusion, the IL-9 genetic polymorphism (rs2069885) has an opposite effect on the risk of severe RSV bronchiolitis in boys and girls. Although so far a difference in IL-9 production in boys and girls has not been reported, this study may help in explaining the different risks of severe RSV bronchiolitis in boys and girls.

Toll-like receptor 4 polymorphism associated with the response to whole-cell pertussis vaccination in children from the KOALA study

We examined the association between haplotype tagging single-nucleotide polymorphisms in TLR4 and the pertussis toxin-specific immunoglobulin G response after whole-cell pertussis (wP) vaccination in 515 1-year-old children from the KOALA study. A lower titer was associated with the minor allele of rs2770150, supporting a role for Toll-like receptor 4 in the antibody response to wP vaccination.

Genetic susceptibility to respiratory syncytial virus bronchiolitis is predominantly associated with innate immune genes

BACKGROUND

Respiratory syncytial virus (RSV) is a common cause of severe lower respiratory tract infection in infants. Only a proportion of children infected with RSV require hospitalization. Because known risk factors for severe disease, such as premature birth, cannot fully explain differences in disease severity, genetic factors have been implicated.

METHODS

To study the complexity of RSV susceptibility and to identify the genes and biological pathways involved in its development, we performed a genetic association study involving 470 children hospitalized for RSV bronchiolitis, their parents, and 1008 random, population controls. We analyzed 384 single-nucleotide polymorphisms (SNPs) in 220 candidate genes involved in airway mucosal responses, innate immunity, chemotaxis, adaptive immunity, and allergic asthma.

RESULTS

SNPs in the innate immune genes VDR (rs10735810; P=.0017), JUN (rs11688; P=.0093), IFNA5 (rs10757212; P=.0093), and NOS2 (rs1060826; P=.0031) demonstrated the strongest association with bronchiolitis. Apart from association at the allele level, these 4 SNPs also demonstrated association at the genotype level (P=.0056, P=.0285, P=.0372, and P=.0117 for the SNPs in VDR, JUN, IFNA5, and NOS2, respectively). The role of innate immunity as a process was reinforced by association of the whole group of innate immune SNPs when the global test for groups of genes was applied (P=.046).

CONCLUSION

SNPs in innate immune genes are important in determining susceptibility to RSV bronchiolitis.

Polymorphisms in the genes involved in the arachidonic acid-pathway, fish consumption and the risk of colorectal cancer

The objective of this study on colorectal cancer was to investigate the associations between SNPs in the genes involved in the arachidonic acid (AA)-pathway, their haplotypes and colorectal cancer. Moreover, interactions between SNPs and fish consumption were considered. In this study, a total of 508 cases and 772 controls were included, originating from 2 prospective cohorts, the Monitoring Project on Cardiovascular Disease Risk Factors (PPHV) and Diagnostisch Onderzoek Mammacarcinoom (DOM). Genotypes of 23 SNPs in 7 candidate genes were determined and the modifying effect of fish consumption was considered. A protective effect of the minor allele of SNP V102V in PTGS2 was observed (odds ratio (OR), 0.37; 95% confidence intervals (CI), 0.16-0.87). The haplotype representing this allele showed a weaker inverse association, indicating that 2 alleles are necessary to obtain this protective effect. Fish consumption data was available for 209 cases and 418 controls. Increased fish consumption was inversely associated with cancer, although not significant (OR, 0.83; 95% CI, 0.57-1.20). Despite the substantial reductions in cancer risk for some genotypes in combination with high fish intake, no significant interactions between any SNP studied and fish consumption were observed. We have previously described an association between colorectal adenomas and SNP V102V in PTGS2 and have now confirmed this association for colorectal adenocarcinomas. Fish consumption of once a week or more might protect against colorectal cancer, but no significant interactions with SNPs in the genes involved in the AA-pathway could be detected within the study.

Protective effect of nonsteroidal anti-inflammatory drugs on colorectal adenomas is modified by a polymorphism in peroxisome proliferator-activated receptor delta

OBJECTIVE

Nonsteroidal anti-inflammatory drugs (NSAIDs) are associated with a decreased risk of colorectal tumors. Single nucleotide polymorphisms (SNPs) in target genes of NSAID action, and their haplotypes, might modulate this protective effect.

METHODS

A case-control study including 724 cases and 682 controls was used to evaluate the effect of NSAIDs on colorectal adenoma risk in The Netherlands, a country in which NSAID use is relatively low. Cases and controls were classified according to presence or absence of endoscopy-proven, pathology-confirmed colorectal adenomas, ever in their lives. Thirteen SNPs in four genes (PPARdelta, PPARgamma, PTGS1 and PTGS2) were genotyped in 787 subjects (384 cases and 403 controls).

RESULTS

Compared to non-regular users (< 12 times/year), regular users of NSAIDs (> or = 12 times/year) had a lower risk of colorectal adenomas (odds ratio (OR): 0.75, 95% confidence interval (CI): 0.56-0.99). The results were similar for aspirin only. We found an interaction between SNP c.-789C>T in PPARdelta and NSAID use (P=0.03). The protective effect of NSAIDs was strengthened for regular users with the PPARdelta CT or TT genotypes (OR: 0.35, 95%CI: 0.11-1.13), whereas a positive association was observed for non-regular users with these genotypes (OR: 2.24, 95%CI: 1.06-4.73) as compared to non-regular users with the CC genotype. Also, a statistically significant interaction between a major haplotype containing the minor allele of this SNP and NSAID use was observed.

CONCLUSIONS

This study confirms the protective effect of NSAIDs and suggests a modulating effect of a SNP in the promoter of PPARdelta.

Colorectal adenoma risk is modified by the interplay between polymorphisms in arachidonic acid pathway genes and fish consumption

Associations between polymorphisms in genes (SNPs) involved in the arachidonic acid (AA) pathway and colorectal adenomas have been investigated in a Dutch case control study including 384 cases and 403 polyp-free controls. Twenty-one polymorphisms in seven candidate genes were studied and a potential modifying effect of fish consumption was considered. A protective effect on colorectal adenomas was found for the CT genotype of SNP H477H in PPARgamma and the GC genotype of SNP V102V in COX-2 (OR 0.63, 95% CI 0.45-0.89 and OR 0.65, 95% CI 0.46-0.92, respectively) compared with the homozygous major genotypes. An increase in adenoma risk was observed for the TC genotype of SNP c.2242T-->C in COX-2 (OR 1.47, 95% CI 1.07-2.00) compared with the TT genotype. Analysis with estimated haplotypes confirmed these associations and revealed three additional associations with COX-2, sPLA(2) and 15LOX haplotypes. Fish consumption modified the associations with COX-2 and PPARdelta genotypes. For SNP c.-789C-->T in PPARdelta the major genotype showed a decrease in adenoma risk for those in the highest tertile of fish consumption (T3), as compared with the lowest tertile (T1) (OR 0.65, 95% CI 0.41-1.02). Protective effects were also observed for SNPs V102V and c.2242T-->C in COX-2 and high fish intake. The interaction between fish consumption and c.2242T-->C was statistically significant, with an OR for the TT genotype and high fish consumption of 0.52 (95% CI 0.27-1.01) as compared with low fish intake. These results indicate that SNPs in genes involved in the AA pathway are associated with colorectal adenoma risk. Some of these associations are modified by fish consumption.

Tissue levels of fish fatty acids and risk of colorectal adenomas: a case-control study (Netherlands)

Epidemiological and animal studies have suggested that a high ratio of n-3 fish fatty acids to arachidonic acid (AA), might protect against colorectal carcinogenesis. Competition of n-3 and n-6 fatty acids, especially AA, for the enzyme cyclooxygenase-2 may be responsible for this effect. To examine the relation between fish intake and colorectal adenomas, data from a Dutch case-control study were analysed. All 52 cases and 57 controls filled out a food questionnaire, underwent a full colonic examination and have had a fat biopsy from the buttock. Intake of fish and fish fatty acids was inversely associated with colorectal adenomas although not statistically significant. For the ratio of fish fatty acids to AA, the ORs in the second and third tertile were 1.2 and 0.8 (p-trend = 0.78). Tissue levels of fish fatty acids were inversely associated and tissue levels of AA were positively associated with adenomas, although not statistically significant. However, the OR for the ratio of fish fatty acids to AA was 0.2 in the second and third tertile (p-trend = 0.002). In line with the hypothesis, a high ratio of fish fatty acids to AA in adipose tissue was associated with a lower risk of colorectal adenomas.