Energy restriction at young age, genetic variants in the insulin-like growth factor pathway and colorectal cancer risk in the Netherlands Cohort Study

A systematic review and meta-analysis for the association of the insulin-like growth factor1 pathway genetic polymorphisms with colorectal cancer susceptibility

Background

The receptors, ligands, and associated proteins of the insulin-like growth factor (IGF) family are involved in cancer development. The IGF1 receptor and its accompanying signaling cascade are a crucial growth-regulatory mechanism that plays an important role in colorectal cancer (CRC) proliferation and differentiation. IRS1 (Insulin receptor substrate-1), a major substrate for the IGF1R, is involved in cell growth and promotes tumorigenesis. There are shreds of evidence from prior research suggesting that IGF system polymorphisms may influence susceptibility to CRC. However, the findings in this area were contradictory. Accordingly, we carried out a systematic literature search to identify all case-control, cross-sectional, and cohort studies on the association between various polymorphisms across four IGF1 pathway genes (IGF1, IGF1R, IRS1, and IRS2) and the risk of CRC.

Methods

We performed a comprehensive search strategy in PubMed, Scopus, and Web of Science databases for articles available until Aug 30, 2022. A total of 26 eligible studies with IGF1/IGF1R, IRS1 and IRS2 polymorphisms; met the inclusion criteria. All case-control studies for IGF1 rs6214C>T, IRS1 rs1801278G>A, and IRS2 rs1805097G>A comprising 22,084 cases and 29,212 controls were included in the current meta-analysis. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate relationships between the polymorphisms and CRC susceptibility. All statistical analyses were performed using STATA software version 14.0.

Results

The meta-analysis of available data for rs6214C>T, rs1801278G>A, and rs1805097G>A showed a significant association between these polymorphisms and an increased CRC risk in some of the comparisons studied (rs6214C>T, pooled OR for CC = 0.43, 95% CI 0.21- 0.87, P = 0.019; rs1801278G>A, OR for GA = 0.74, 95% CI 0.58-0.94, P = 0.016; rs1805097G>A, OR for GA = 0.83, 95% CI 0.71-0.96, P = 0.013). Nevertheless, the meta-analysis did not include other genetic variations in IGF1, IGF1R, IRS1, and IRS2 due to heterogeneity and limited sample size.

Conclusions

This systematic review and meta-analysis provide evidence that genetic variants in IGF1 rs6214C>T, IRS1 rs1801278G>A, and IRS2 rs1805097G>A are associated with an increased risk of CRC. These findings may contribute to a better understanding of the complex genetic mechanisms involved in CRC development and could inform future research on prevention and treatment strategies for this disease.

Polymorphisms in the mTOR-PI3K-Akt pathway, energy balance-related exposures and colorectal cancer risk in the Netherlands Cohort Study

BACKGROUND

The mTOR-PI3K-Akt pathway influences cell metabolism and (malignant) cell growth. We generated sex-specific polygenic risk scores capturing natural variation in 7 out of 10 top-ranked genes in this pathway. We studied the scores directly and in interaction with energy balance-related factors (body mass index (BMI), trouser/skirt size, height, physical activity, and early life energy restriction) in relation to colorectal cancer (CRC) risk in the Netherlands Cohort Study (NLCS) (n=120,852). The NLCS has a case-cohort design and 20.3 years of follow-up. Participants completed a baseline questionnaire on diet and cancer in 1986 when 55-69 years old. ~75% of the cohort returned toenail clippings used for DNA isolation and genotyping (n subcohort=3,793, n cases=3,464). To generate the scores, the dataset was split in two and risk alleles were defined and weighted based on sex-specific associations with CRC risk in the other dataset half, because there were no SNPs in the top-ranked genes associated with CRC risk in previous genome-wide association studies at a significance level p<1*10^-5.

RESULTS

Cox regression analyses showed positive associations between the sex-specific polygenic risk scores and colon but not rectal cancer risk in men and women, with hazard ratios for continuously modeled scores close to 1.10. There was no modifying effect observed of the scores on associations between the energy balance-related factors and CRC risk. However, BMI (in men), non-occupational physical activity (in women), and height (in men and women) were associated with the risk of CRC, in particular (proximal and distal) colon cancer, in the direction as expected in the lower tertiles of the sex-specific polygenic risk scores.

CONCLUSIONS

Current data suggest that the mTOR-PI3K-Akt pathway may be involved in colon cancer development. This study thereby sheds more light on colon cancer etiology through use of genetic variation in the mTOR-PI3K-Akt pathway.

Growth Hormone's Links to Cancer

Several components of the GH axis are involved in tumor progression, and GH-induced intracellular signaling has been strongly associated with breast cancer susceptibility in genome-wide association studies. In the general population, high IGF-I levels and low IGF-binding protein-3 levels within the normal range are associated with the development of common malignancies, and components of the GH-IGF signaling system exhibit correlations with clinical, histopathological, and therapeutic parameters in cancer patients. Despite promising findings in preclinical studies, anticancer therapies targeting the GH-IGF signaling system have led to disappointing results in clinical trials. There is substantial evidence for some degree of protection against tumor development in several animal models and in patients with genetic defects associated with GH deficiency or resistance. In contrast, the link between GH excess and cancer risk in acromegaly patients is much less clear, and cancer screening in acromegaly has been a highly controversial issue. Recent studies have shown that increased life expectancy in acromegaly patients who attain normal GH and IGF-I levels is associated with more deaths due to age-related cancers. Replacement GH therapy in GH deficiency hypopituitary adults and short children has been shown to be safe when no other risk factors for malignancy are present. Nevertheless, the use of GH in cancer survivors and in short children with RASopathies, chromosomal breakage syndromes, or DNA-repair disorders should be carefully evaluated owing to an increased risk of recurrence, primary cancer, or second neoplasia in these individuals.

Sirtuin 1 genetic variation, energy balance and colorectal cancer risk by sex and subsite in the Netherlands Cohort Study

Sirtuin 1 (SIRT1) is an energy-sensing protein, which may affect tumorigenesis. We used SIRT1 variants as time-independent indicators of SIRT1 involvement in carcinogenesis and we studied two tagging SIRT1 variants in relation to colorectal cancer (CRC) risk. We also evaluated known energy balance-related CRC risk factors within SIRT1 genotype strata. The Netherlands Cohort Study includes 120,852 individuals and has 20.3 years follow-up (case-cohort: n_subcohort = 5000; n_{CRC cases} = 4667). At baseline, participants self-reported weight, weight at age 20, height, trouser/skirt size reflecting waist circumference, physical activity, and early life energy restriction. SIRT1 rs12778366 and rs10997870 were genotyped in toenail DNA available for ~75% of the cohort. Sex- and subsite-specific Cox hazard ratios (HRs) showed that the rs12778366 CC versus TT genotype decreased CRC and colon cancer risks in women (HR_CRC = 0.53, 95% confidence interval: 0.30–0.94) but not men. Multiplicative interactions were observed between SIRT1 variants and energy balance-related factors in relation to CRC endpoints, but the direction of associations was not always conform expectation nor specific to one genotype stratum. In conclusion, these results support SIRT1 involvement in colon cancer development in women. No conclusions could be made regarding a modifying effect of SIRT1 variants on associations between energy balance-related factors and CRC risk.

Estimating the Relative Excess Risk Due to Interaction in Clustered-Data Settings

The risk difference scale is often of primary interest when evaluating public health impacts of interventions on binary outcomes. However, few investigators report findings in terms of additive interaction, probably because the models typically used for binary outcomes implicitly measure interaction on the multiplicative scale. One measure with which to assess additive interaction from multiplicative models is the relative excess risk due to interaction (RERI). The RERI measure has been applied in many contexts, but one limitation of previous approaches is that clustering in data has rarely been considered. We evaluated the RERI metric for the setting of clustered data using both population-averaged and cluster-conditional models. In simulation studies, we found that estimation and inference for the RERI using population-averaged models was straightforward. However, frequentist implementations of cluster-conditional models including random intercepts often failed to converge or produced degenerate variance estimates. We developed a Bayesian implementation of log binomial random-intercept models, which represents an attractive alternative for estimating the RERI in cluster-conditional models. We applied the methods to an observational study of adverse birth outcomes in mothers with human immunodeficiency virus, in which mothers were clustered within clinical research sites.