Insulin-like growth factor-1 promoter polymorphisms and colorectal cancer: a functional genomics approach

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.

IGF1-mediated HOXA13 overexpression promotes colorectal cancer metastasis through upregulating ACLY and IGF1R

Metastasis is the major reason for the high mortality of colorectal cancer (CRC) patients and its molecular mechanism remains unclear. Here, we report a novel role of Homeobox A13 (HOXA13), a member of the Homeobox (HOX) family, in promoting CRC metastasis. The elevated expression of HOXA13 was positively correlated with distant metastasis, higher AJCC stage, and poor prognosis in two independent CRC cohorts. Overexpression of HOXA13 promoted CRC metastasis whereas downregulation of HOXA13 suppressed CRC metastasis. Mechanistically, HOXA13 facilitated CRC metastasis by transactivating ATP-citrate lyase (ACLY) and insulin-like growth factor 1 receptor (IGF1R). Knockdown of ACLY and IGFIR inhibited HOXA13-medicated CRC metastasis, whereas ectopic overexpression of ACLY and IGFIR rescued the decreased CRC metastasis induced by HOXA13 knockdown. Furthermore, Insulin-like growth factor 1 (IGF1), the ligand of IGF1R, upregulated HOXA13 expression through the PI3K/AKT/HIF1α pathway. Knockdown of HOXA13 decreased IGF1-mediated CRC metastasis. In addition, the combined treatment of ACLY inhibitor ETC-1002 and IGF1R inhibitor Linsitinib dramatically suppressed HOXA13-mediated CRC metastasis. In conclusion, HOXA13 is a prognostic biomarker in CRC patients. Targeting the IGF1-HOXA13-IGF1R positive feedback loop may provide a potential therapeutic strategy for the treatment of HOXA13-driven CRC metastasis.

Association between insulin-like growth factor 1 gene rs5742612 polymorphism and malignant tumor susceptibility: a meta-analysis

BACKGROUND

Malignant tumor is a serious threat to human health and life, which is a difficult problem in the world. Insulin-like growth factor 1 (IGF1) is an important mitotic factor in vivo. It usually acts in the way of autocrine and paracrine to control the proliferation, differentiation, and apoptosis of various cells, IGF1 has a strong mitotic and anti-apoptosis activity in malignant cells. Single nucleotide polymorphism (SNP) is an important part of individual genetic variation. A large number of studies have shown that IGF1 SNP associated with the risk of a malignant tumor may be an important biomarker for the diagnosis of malignant tumors. Therefore, the article will investigate the association between rs5742612 polymorphism of IGF1 gene and malignant tumor susceptibility.

METHODS

We searched for studies in five databases (PubMed, Embase, Web of Science, CNKI and Wanfang) regarding the association between IGF1 gene rs5742612 and malignant tumor susceptibility. Odds ratios (ORs) and the related 95% confidence intervals (CIs) were employed to assess the strength of the associations.

RESULTS

Ultimately this study identified seven articles that met the inclusion criteria, involving 2,581 cases and 2,445 controls. There was no significant correlation between IGF1 gene rs5742612 polymorphism and malignant tumor susceptibility [thymidine (T) vs. cytimidine (C), OR =0.99, 95% CI: 0.85-1.15, P=0.91; TC vs. CC: OR =1.03, 95% CI: 0.81-1.32, P=0.79; TT vs. CC: OR =0.92, 95% CI: 0.73-1.17, P=0.52; TT + TC =0.91; TC vs. CC: OR =0.97, 95% CI: 0.77-1.22, P=0.80; TT vs. TC + CC: OR =0.98, 95% CI: 0.81-1.18, P=0.83].

CONCLUSIONS

There was no significant association detected between IGF1 gene rs5742612 polymorphism and malignant tumor susceptibility.

Relationship between polymorphisms of the lipid metabolism-related gene PLA2G16 and risk of colorectal cancer in the Chinese population

This study aimed to investigate the relationship between polymorphisms in the lipid metabolism-related gene PLA2G16 encoding Group XVI phospholipase A2 and the risk of colorectal cancer (CRC) in the Chinese population. A total of 185 patients with CRC and 313 healthy controls were enrolled. Thirteen single nucleotide polymorphisms (SNPs) of PLA2G16 were genotyped with SNPscan™. Linkage disequilibrium and haplotypes were analysed using Haploview software. Multivariate logistic regression was used to determine the association between the various genotypes and CRC risk. We identified five PLA2G16 SNPs (rs11600655, rs3809072, rs3809073, rs640908 and rs66475048) that were associated with CRC risk after adjusting for age, sex and body mass index. Two haplotypes (CTC and GGA) of rs11600655, rs3809073 and rs3809072, were relevant to CRC risk. The rs11600655 polymorphism was also associated with lymph node metastasis and CRC staging, while rs3809073 and rs3809072 may affect transcriptional regulation of PLA2G16 by altering transcription factor binding. These findings suggest that PLA2G16 polymorphisms-especially CTC and GGA haplotypes-increase CRC susceptibility. Importantly, we showed that the rs11600655 CC, rs640908 CT and rs66475048 GA genotypes are independent risk factors for CRC in the Chinese population.

Distribution of a Single Nucleotide Polymorphism of Insulin-Like Growth Factor-1 in Colorectal Cancer Patients and Its Association with Mucinous Adenocarcinoma

Purpose

To analyze the difference in the distribution of an insulin growth factor-1 (IGF-1) polymorphism (-2995 C/A) between young and old colorectal cancer (CRC) patients.

Methods

Information from 950 CRC patients undergoing surgery at the Taipei Veterans General Hospital between 2000 and 2005 was collected. The IGF-1 polymorphism was analyzed in patients in extreme age ranges at the time of CRC onset (i.e., under the 20th and above the 80th percentiles, respectively). Associations between clinicopathological variables and the IGF-1 polymorphism were analyzed.

Results

Young CRC patients had a higher frequency of advanced disease (58.7%) and mucinous adenocarcinoma (20%) than old CRC patients. Among old CRC patients, the frequency of the AA genotype of IGF-1 was 12.7% (24/189), which was significantly higher than in young patients (4.2%). Other clinicopathological factors including tumor location, differentiation, lymphovascular invasion, and TNM stage were not associated with the AA genotype of IGF-1. Mucinous differentiation (but not the other clinicopathological factors) was significantly associated with the CA/AA genotype of IGF-1 (39/195).

Conclusions

Older patients had a higher frequency of the AA genotype of IGF-1(-2995 C/A), while younger patients more often had advanced disease and mucinous adenocarcinoma.

Association of the insulin-like growth factor-1 single nucleotide polymorphisms rs35767, rs2288377, and rs5742612 with osteoporosis risk: A meta-analysis

BACKGROUND

Insulin-like growth factor-1 (IGF-1) plays an important role in the regulation of bone formation and mineralization. We aimed to perform a meta-analysis to assess the association of three IGF-1 single nucleotide polymorphisms (SNPs) rs35767, rs2288377, and rs5742612 with osteoporosis risk.

METHODS

A systematic search of PubMed, Web of Science, Embase, Medline, Scopus, CNKI, and Wanfang databases was conducted. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using a fixed effects model.

RESULTS

Four Chinese case-control studies with a total of 2807 participants were included in this meta-analysis. The results revealed an association between rs35767 and osteoporosis risk in all study subjects (women and men) in dominant (OR 1.32, 95% CI 1.13-1.53, P < .001), recessive (OR 1.73, 95% CI 1.35-2.21, P < .001), homozygote (OR 1.89, 95% CI 1.46-2.45, P < .001), and allelic (OR 1.31, 95% CI 1.18-1.47, P < .001) models. Subgroup analysis according to gender showed that rs35767 was associated with osteoporosis risk in women under dominant (OR 1.29, 95% CI 1.08-1.54, P = .005), recessive (OR 1.59, 95% CI 1.19-2.12, P = .002), homozygote (OR 1.73, 95% CI 1.28-2.34, P < .001), and allelic (OR 1.28, 95% CI 1.12-1.47, P < .001) models. Meta-analysis did not find associations of rs2288377 and rs5742612 with osteoporosis risk. There was no evidence of between-study heterogeneity and publication bias.

CONCLUSION

Our results suggest that rs35767 is associated with osteoporosis risk in Chinese, whereas there is no association of rs2288377 and rs5742612 with osteoporosis risk.

Genetic variants and traits related to insulin-like growth factor-I and insulin resistance and their interaction with lifestyles on postmenopausal colorectal cancer risk

Genetic variants and traits in metabolic signaling pathways may interact with lifestyle factors such as obesity, physical activity, and exogenous estrogen (E), influencing postmenopausal colorectal cancer (CRC) risk, but these interrelated pathways are not fully understood. In this case-cohort study, we examined 33 single-nucleotide polymorphisms (SNPs) in genes related to insulin-like growth factor-I (IGF-I)/ insulin resistance (IR) traits and signaling pathways, using data from 704 postmenopausal women in Women’s Health Initiative Observation ancillary studies. Stratifying by the lifestyle modifiers, we assessed the effects of IGF-I/IR traits (fasting total and free IGF-I, IGF binding protein-3, insulin, glucose, and homeostatic model assessment–insulin resistance) on CRC risk as a mediator or influencing factor. Six SNPs in the INS, IGF-I, and IGFBP3 genes were associated with CRC risk, and those associations differed between non-obese/active and obese/inactive women and between E nonusers and users. Roughly 30% of the cancer risk due to the SNP was mediated by IGF-I/IR traits. Likewise, carriers of 11 SNPs in the IRS1 and AKT1/2 genes (signaling pathway–related genetic variants) had different associations with CRC risk between strata, and the proportion of the SNP–cancer association explained by traits varied from 30% to 50%. Our findings suggest that IGF-I/IR genetic variants interact with obesity, physical activity, and exogenous E, altering postmenopausal CRC risk, through IGF-I/IR traits, but also through different pathways. Unraveling gene–phenotype–lifestyle interactions will provide data on potential genetic targets in clinical trials for cancer prevention and intervention strategies to reduce CRC risk.

Identification of hub genes, key miRNAs and potential molecular mechanisms of colorectal cancer

Colorectal cancer (CRC) is the most common cancer of the digestive system. The aim of the present study was to identify the potential biomarkers and uncover the underlying mechanisms. The gene and miRNA expression profiles were obtained from GEO database. The differentially expressed genes (DEGs) and miRNAs (DE miRNAs) were identified by GEO2R. The Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed by KOBAS 3.0. The protein-protein interaction (PPI) network and miRNA-gene network were constructed by Cytoscape software. Then, the identified genes were verified by quantitative real-time PCR in both CRC tissue samples and cell lines. A total of 600 upregulated DEGs, 283 downregulated DEGs, 13 upregulated DE miRNAs and 7 downregulated DE miRNAs were identified. GO analysis results showed that upregulated DEGs were significantly enriched in binding, organelle and cellular process. Downregulated DEGs were enriched in binding, extracellular region and chemical homeostasis. KEGG analysis showed that the DEGs were mostly enriched in cell cycle and pathways in cancer. A total of eight genes were identified as biomarkers, including CAD, ITGA2, E2F3, BCL2, PRKACB, IGF1, SGK1 and NR3C1. Experimental validation showed that seven of the eight identified genes had the same expression trend as predicted, except for ITGA2. Besides, hsa-miR-552 and hsa-miR-30a were identified as key miRNAs. The present study provides a series of biomarkers and mechanisms for the diagnosis and therapy of CRC. We also prove that although bioinformatics analysis is a wonderful approach, experiment validation is necessary.

Insulin-like growth factor (IGF) axis in cancerogenesis

Determination of the role of insulin-like growth factor (IGF) family components in carcinogenesis of several human tumors is based on numerous epidemiological and pre-clinical studies, experiments in vivo and in vitro and on attempts at application of drugs affecting the IGF axis. Investigative hypotheses in original studies were based on biological functions manifested by the entire family of IGF (ligands, receptors, linking proteins, adaptor molecules). In the context of carcinogenesis the most important functions of IGF family involve intensification of proliferation and inhibition of cell apoptosis and effect on cell transformation through synthesis of several regulatory proteins. IGF axis controls survival and influences on metastases of cells. Interactions of IGF axis components may be of a direct or indirect nature. The direct effects are linked to activation of PI3K/Akt signaling pathway, in which the initiating role is first of all played by IGF-1 and IGF-1R. Activity of this signaling pathway leads to an increased mitogenesis, cell cycle progression, and protection against different apoptotic stresses. Indirect effects of the axis depend on interactions between IGF and other molecules important for cancer etiology (e.g. sex hormones, products of suppressor genes, viruses, and other GFs) and the style of life (nutrition, physical activity). From the clinical point of view, components of IGF system are first of all considered as diagnostic serous and/or tissue biomarkers of a given cancer, prognostic factors and attractive target of modern anti-tumor therapies. Several mechanisms in which IGF system components act in the process of carcinogenesis need to be clarified, mainly due to multifactorial etiology of the neoplasms. Pin-pointing of the role played in carcinogenesis by any single signaling pathway remains particularly difficult. The aim of this review is to summarize the current data of several epidemiological studies, experiments in vitro and on animal models, to increase our understanding of the complex role of IGF family components in the most common human cancers.

Genetic Variants in the Insulin-like Growth Factor Pathway and Colorectal Cancer Risk in the Netherlands Cohort Study

Interrelationships between insulin-like growth factors (IGFs), hyperinsulinaemia, diabetes, and colorectal cancer (CRC) indicate involvement of IGFs in colorectal tumorigenesis. We investigated the CRC risk associated with 24 single nucleotide polymorphisms (SNPs) in 9 genes related to the IGF pathway and an IGF1 19-CA repeat polymorphism. Variants were selected from literature and genotyped in toenail DNA from 3,768 subcohort members and 2,580 CRC cases from the Netherlands Cohort Study, which has a case-cohort design (n = 120,852). We used the follow-up period 1986–2002. Eighteen SNPs were unequivocally associated with selected endpoints in the literature and unfavorable alleles were aggregated into a genetic sum score. Cox regression showed that a higher genetic sum score significantly increased CRC risk at all subsites, except the rectum, in men (highest vs. lowest tertile: HR for CRC = 1.36, 95% CI: 1.11, 1.65; P-trend = 0.002). Single SNPs (except the IGF1 SNP rs5742694) were not associated with risk. Models including the total number of IGF1 19-CA repeats showed CRC risk was halved at all subsites in women carrying <38 repeats but not >38 repeats (≤36 versus 38 repeats: HR for CRC = 0.44; 95% CI: 0.33, 0.58; P-trend < 0.001). These findings support a role for variants in IGF-related genes in colorectal tumorigenesis.

Body size, physical activity, genetic variants in the insulin-like growth factor pathway and colorectal cancer risk

Insulin-like growth factors (IGFs) have been associated with growth, body size, physical activity and colorectal cancer (CRC). We hypothesized that variants in IGF-related genes increase the CRC susceptibility associated with a larger body size and a lack of physical activity. We assessed this in The Netherlands Cohort Study. Participants (n = 120852) completed a baseline questionnaire on diet and cancer. ~75% returned toenail clippings. Using a case-cohort approach and 16.3 years of follow-up, toenail DNA from 3768 subcohort members and 2580 CRC cases was genotyped. We aggregated unfavorable alleles (potentially increasing CRC risk) for 18 single nucleotide polymorphisms in 8 genes into a sum score. The sum score (in tertiles) and an IGF1 19-CA repeat polymorphism (19/19, 19/non-19 and non-19/non-19 repeats) in combination with body size (mostly in tertiles) and (non-)occupational physical activity (>12, 8-12 and <8 kJ/min in the job and >90, >60-90, >30-60 and ≤30 min/day) were analyzed by Cox regression. Increasingly higher hazard ratios (HRs) for CRC were observed for a larger adult body mass index, larger trouser size and tallness in the presence of more unfavorable alleles in men. HRs (95% confidence intervals) for joint effects were 1.55 (1.06-2.25), 1.78 (1.29-2.46) and 1.48 (1.01-2.17), respectively. In women, variant repeat alleles halved CRC risk irrespective of body size and physical activity. Almost no interactions tested significant. To conclude, a larger body size was a CRC risk factor in men in the presence of an accumulation of unfavorable alleles in IGF-related genes, but interactions were generally nonsignificant.

IFN-γ-mediated IRF1/miR-29b feedback loop suppresses colorectal cancer cell growth and metastasis by repressing IGF1

To investigate the clinicopathological significance and underlying mechanism of microRNA-29b (miR-29b) in colorectal cancer (CRC), the role of miR-29b was investigated using in vivo and in vitro assays. Luciferase reporter assays were conducted to determine the association between miR-29b and the insulin-like growth factor 1 (IGF1) 3' untranslated region (3'UTR). Chromatin immunoprecipitation (ChIP) assays were employed to assess the direct binding of interferon regulatory factor 1 (IRF1) to miR-29b. We found that interferon (IFN)-γ could induce miR-29b by recruiting IRF1 to binding sites in the miR-29b promoter. A low level of miR-29b was significantly associated with an aggressive phenotype. MiR-29b inhibited CRC cell growth and invasion. IGF1, an activator of PI3K/Akt signaling, was confirmed as a novel target of miR-29b. Moreover, miR-29b increased IRF1 expression, and the inhibition of miR-29b suppressed IFN-γ-induced apoptosis. We elucidated the potential signaling pathway, IFN-γ/IRF1/miR-29b/IGF1, and its implication for CRC tumorigenesis. A positive feedback loop between IRF1 and miR-29b may contribute to the sensitivity of CRC cells to IFN-γ. Targeting miR-29b may provide a strategy for blocking CRC growth and metastasis.

An exon variant in insulin receptor gene is associated with susceptibility to colorectal cancer in women

Given the role of insulin resistance in colorectal cancer (CRC), we explored whether genetic variants in insulin (INS), insulin receptor (INSR), insulin receptor substrate 1 (IRS1), insulin receptor substrate 2 (IRS2), insulin-like growth factor 1 (IGF1), and insulin-like growth factor binding protein 3 (IGFBP3) genes were associated with CRC risk. A total of 600 subjects, including 261 cases with CRC and 339 controls, were enrolled in this case-control study. Six polymorphisms in INS (rs689), INSR (rs1799817), IRS1 (rs1801278), IRS2 (rs1805097), IGF1 (rs5742612), and IGFBP3 (rs2854744) genes were genotyped using PCR-RFLP method. No significant difference was observed for INS, INSR, IRS1, IRS2, IGF1, and IGFBP3 genes between the cases and controls. However, the INSR rs1799817 "TT + CT" genotype and "CT" genotype compared with "CC" genotype occurred more frequently in the women with CRC than women controls (P = 0.007; OR = 1.93, 95 %CI = 1.20-3.11 and P = 0.002, OR = 2.15, 95 %CI = 1.31-3.53, respectively), and the difference remained significant after adjustment for confounding factors including age, BMI, smoking status, NSAID use, and family history of CRC (P = 0.018; OR = 1.86, 95 %CI = 1.11-3.10 and P = 0.004, OR = 2.18, 95 %CI = 1.28-3.71, respectively). In conclusion, to our knowledge, this study indicated for the first time that the INSR rs1799817 TT + CT genotype and CT genotype compared with the CC genotype had 1.86-fold and 2.18-fold increased risks for CRC among women, respectively. Furthermore, this finding is in line with previous studies which found significant associations between other variants of the INSR gene and CRC risk. Nevertheless, further studies are required to confirm our findings.

Is there an association between variants in candidate insulin pathway genes IGF-I, IGFBP-3, INSR, and IRS2 and risk of colorectal cancer in the Iranian population?

BACKGROUND

Several epidemiological studies have shown associations between colorectal cancer (CRC) risk and type 2 diabetes and obesity. Any effects would be expected to be mediated through the insulin pathway. Therefore it is possible that variants of genes encoding components of the insulin pathway play roles in CRC susceptibility. In this study, we hypothesized that polymorphisms in the genes involving the insulin pathway are associated with risk of CRC.

MATERIALS AND METHODS

The associations of four single nucleotide polymorphisms (SNPs) in IGF-I (rs6214), IGFBP-3 (rs3110697), INSR (rs1052371), and IRS2 (rs2289046) genes with the risk of CRC were evaluated using a case-control design with 167 CRC cases and 277 controls by the PCR-RFLP method.

RESULTS

Overall, we observed no significant difference in genotype and allele frequencies between the cases and controls for the IGF-I, IGFBP-3, INSR, IRS2 gene variants and CRC before or after adjusting for confounders (age, BMI, sex, and smoking status). However, we observed that the IRS2 (rs2289046) GG genotype compared with AA+AG genotypes has a protective effect for CRC in normal weight subjects (p=0.035, OR=0.259, 95%CI= 0.074-0.907).

CONCLUSIONS

These findings do not support plausible associations between polymorphic variations in IGF-I, IGFBP-3, INSR, IRS2 genes and risk of CRC. However, the evidence for a link between the IRS2 (rs2289046) variant and risk of CRC dependent on the BMI of the subjects, requires confirmation in subsequent studies with greater sample size.

Downregulation of hematopoietic MUC1 during experimental colitis increases tumor-promoting myeloid-derived suppressor cells

PURPOSE

MUC1 is a tumor-associated antigen that is aberrantly expressed in cancer and inflammatory bowel disease (IBD). Even though immune cells express low MUC1 levels, their modulations of MUC1 are important in tumor progression. Consistent with previous clinical data that show increased myeloid-derived suppressor cells (MDSCs) in IBD, we now show that downregulation of MUC1 on hematopoietic cells increases MDSCs in IBD, similar to our data in tumor-bearing mice. We hypothesize that MDSC expansion in IBD is critical for tumor progression.

EXPERIMENTAL DESIGN

To mechanistically confirm the linkage between Muc1 downregulation and MDSC expansion, we generated chimeric mice that did not express Muc1 in the hematopoietic compartment (KO→WT). These mice were used in two models of colitis and colitis-associated cancer (CAC) and their responses were compared with wild-type (WT) chimeras (WT→WT).

RESULTS

KO→WT mice show increased levels of MDSCs during colitis and increased protumorigenic signaling in the colon during CAC, resulting in larger colon tumors. RNA and protein analysis show increased upregulation of metalloproteinases, collagenases, defensins, complements, growth factors, cytokines, and chemokines in KO→WT mice as compared with WT→WT mice. Antibody-mediated depletion of MDSCs in mice during colitis reduced colon tumor formation during CAC.

CONCLUSION

Development of CAC is a serious complication of colitis and our data highlight MDSCs as a targetable link between inflammation and cancer. In addition, the lack of MUC1 expression on MDSCs can be a novel marker for MDSCs, given that MDSCs are still not well characterized in human cancers.

Meta-analysis of the association between insulin-like growth factor binding protein 3 genetic polymorphisms and colorectal cancer susceptibility

Insulin-like growth factor binding protein 3 (IGFBP-3) plays an important role in the development and progress of cancers. The association between IGFBP-3 polymorphisms and colorectal cancer remains controversial and ambiguous. The aim of this study is to explore the association between IGFBP3 A-202C and Gly32Ala polymorphisms and colorectal cancer susceptibility using meta-analyisi. Case-control studies on the association between IGFBP3 A-202C and Gly32Ala polymorphisms and colorectal cancer, which had sufficient data for estimating an odds ratio (OR) with 95% confidence interval (CI), were included in the meta-analysis. Abstracts, case reports, editorials, and review articles were excluded. Heterozygous and homozygous mutants were compared with the wild types to estimate combined OR values and 95%CIs with Review Manager 5.0. Six eligible studies were included, with 3157 patients and 6027 controls for A-202C and 1711 patients and 2995 controls for Gly32Ala. No significant association was found in all genetic models (for A-202C, AC vs. AA, OR = 0.99(0.88–1.11), CC vs. AA, OR = 1.06(0.92–1.22), dominant model, OR = 0.98(0.88–1.09), recessive model, OR = 0.94(0.84–1.05); and for Gly32Ala polymorphism, GC vs. GG, OR = 1.10(0.92–1.31), CC vs. GG, OR = 0.93(0.76–1.14), dominant model, OR = 1.05(0.89–1.24), recessive model, OR = 0.90(0.77–1.05)). The results suggest that the IGFBP3 A-202C and Gly32Ala polymorphisms are not associated with colorectal cancer susceptibility.

IGF-I 3' untranslated region: strain-specific polymorphisms and motifs regulating IGF-I in osteoblasts

Reduced IGF-I is associated with low bone mass in humans and mice. C3H/He/J (C3H) mice have higher skeletal IGF-I and greater bone mass than C57BL/6J (B6). We hypothesized that strain-related genotypic differences in Igf1 affected skeletal function. The Igf1 coding region is nonpolymorphic, but its 3' untranslated region (UTR) is polymorphic between C3H and B6. Luciferase-Igf1 3' UTR reporter constructs showed that these polymorphic regions did not affect UTR function. IGF-I splice variants give rise to a common mature IGF-I peptide, but different E peptides. We identified two splice products, exon 4+6 (Ea) and exon 4+5+6 (Eb, mechano-growth factor) and found that their abundance was unchanged during osteoblastic differentiation. The Igf1 3' UTR encoded by exon 6 contains alternative polyadenylation sites. Proximal site use produces a short 3' UTR of approximately 195 bases, whereas distal site usage results in an approximately 6300-base UTR. Although Igf1 mRNA levels did not change during osteoblastic differentiation, distal polyadenylation site usage was increased in B6 cells but not in C3H. The resulting long Igf1 RNA isoform is less stable and has decreased translation efficiency, which may be one mechanism contributing to decreased IGF-I in B6 vs. C3H mice. Although the long UTR contains a conserved [GU](18) repeat, which is a positive regulator of UTR activity, it is also targeted by negative regulators, miR-29 and miR-365. These microRNAs are increased in B6 and C3H cells during osteoblastic differentiation. Differential expression of the long Igf1 3' UTR isoform may be a possible mechanism for enhanced IGF-I regulation in B6 vs. C3H mice.

Genetic variants in IGF-I, IGF-II, IGFBP-3, and adiponectin genes and colon cancer risk in African Americans and Whites

PURPOSE

Evaluating genetic susceptibility may clarify effects of known environmental factors and also identify individuals at high risk. We evaluated the association of four insulin-related pathway gene polymorphisms in insulin-like growth factor-1 (IGF-I) (CA)( n ) repeat, insulin-like growth factor-2 (IGF-II) (rs680), insulin-like growth factor-binding protein-3 (IGFBP-3) (rs2854744), and adiponectin (APM1 rs1501299) with colon cancer risk, as well as relationships with circulating IGF-I, IGF-II, IGFBP-3, and C-peptide in a population-based study.

METHODS

Participants were African Americans (231 cases and 306 controls) and Whites (297 cases, 530 controls). Consenting subjects provided blood specimens and lifestyle/diet information. Genotyping for all genes except IGF-I was performed by the 5'-exonuclease (Taqman) assay. The IGF-I (CA)(n) repeat was assayed by PCR and fragment analysis. Circulating proteins were measured by enzyme immunoassays. Odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated by logistic regression.

RESULTS

The IGF-I (CA)( 19 ) repeat was higher in White controls (50 %) than African American controls (31 %). Whites homozygous for the IGF-I (CA)(19) repeat had a nearly twofold increase in risk of colon cancer (OR = 1.77; 95 % CI = 1.15-2.73), but not African Americans (OR = 0.73, 95 % CI 0.50-1.51). We observed an inverse association between the IGF-II Apa1 A-variant and colon cancer risk (OR = 0.49, 95 % CI 0.28-0.88) in Whites only. Carrying the IGFBP-3 variant alleles was associated with lower IGFBP-3 protein levels, a difference most pronounced in Whites (p-trend <0.05).

CONCLUSIONS

These results support an association between insulin pathway-related genes and elevated colon cancer risk in Whites but not in African Americans.

Clinical significance of insulin-like growth factor gene polymorphisms with survival in patients with gastrointestinal stromal tumors

Purpose

Insulin-like growth factors (IGFs) regulate a wide range of biological functions including cell proliferation, differentiation, and apoptosis through paracrine and autocrine mechanisms. Accordingly, the present study analyzed polymorphisms of IGF genes and their impact on the prognosis for patients with gastrointestinal stromal tumors (GISTs).

Methods

Two hundred-thirteen consecutive patients with GISTs who underwent curative surgery from 5 medical centers were enrolled in the present study. The genomic DNA was extracted from paraffin-embedded tumor tissue, and four IGF-1 (+2995C/A, +533C/T, IVS2-16540A/G, Ex4-177G/C) and one IGF-2 (IVS1+1280A/G) gene polymorphisms were determined using a Sequenom MassARRAY system.

Results

With a median follow-up of 18.4 months, the estimated 5-year relapse-free survival and overall survival rates were 69.9% and 86.7%, respectively. In a multivariate analysis including age, gender, primary site of disease, pathology, and risk stratification, no significant association was observed between the polymorphism of the IGF-1 and IGF-2 genes and survival.

Conclusion

None of the five IGF-1 and IGF-2 gene polymorphisms investigated in this study was found to be an independent prognostic marker for Korean patients with surgically resected GIST. However, further studies on a larger scale are warranted to clarify the role of IGF-1 and IGF-2 gene polymorphisms as a prognostic biomarker for GIST patients.

Review: Single nucleotide polymorphisms associated with the oncogenesis of colorectal cancer

Colorectal cancer (CRC) is provoked by interactions between genetic and environmental factors. We herein review the incidence and the mechanisms of action of the reported single nucleotide polymorphisms (SNPs) in the oncogenesis of CRC. More than 15 reports have studied the SNPs at 8q24, which are associated with the incidence of CRC as well as prostate cancer. We have also reported a SNP at the 10p14 locus, and the risks of other loci for CRC oncogenesis. With regard to the underlying mechanism for CRC, 8q24 is a locus of the long-enhancer site for MYC, which could determine the efficacy of MYC transcription. We suggest that 8q24 SNPs might be associated with the progression of CRC cases mediated by MYC expression. In this report, we summarize the published studies of the genetic background SNPs in the oncogenesis of CRC. The level of risk (most studies indicated less than a twofold increase) for CRC was lower than anticipated. Therefore, it is necessary to identify bona fide SNPs that precisely predict the risk for CRC. Alternatively, it is important to consider other factors, such as environmental or lifestyle-related factors, for the future prevention of CRC.

Body mass index and risk of colorectal cancer in Chinese Singaporeans: the Singapore Chinese Health Study

BACKGROUND

The authors chose to examine the association between body mass index (BMI) and incident colorectal cancer across the spectrum of BMI, including underweight persons, because detailed prospective cohort data on this topic in Asians is scarce, as is data on underweight persons (BMI, <18.5 kg/m(2)) in any population.

METHODS

Analysis of the Singapore Chinese Health Study included 51,251 men and women aged 45-74 years enrolled in 1993-1998 and followed through 2007. Incident cancer cases and deaths among cohort members were identified through record linkage, and 980 cases were identified. Cox regression models were used to investigate the association of baseline BMI with risk of incident colorectal cancer during a mean of 11.5 years of follow-up.

RESULTS

A significant, U-shaped, quadratic association was observed between BMI and colon cancer risk, with increased risk in BMIs ≥27.5 and <18.5 kg/m(2). The association was more pronounced in never smokers and most prominent when further limiting the sample to those free of diabetes and cases with longer than 5 years of follow-up. Localized cases had a more pronounced association in BMIs ≥27.5, whereas advanced cases had a more pronounced association in BMIs <18.5 kg/m(2) . No association was found in relation to rectal cancer risk. The association was also stronger among patients aged 65 years and older.

CONCLUSIONS

BMI displays a U-shaped, quadratic association with colon cancer risk in this Chinese population in Southeast Asia.

Linking obesity to colorectal cancer: application of nutrigenomics

Diet is one of the most affective environmental factors in cancer development. Due to complicated nature of the diet, it has been very difficult to provide clear explanations for the role of dietary components in carcinogenesis. However, as high-throughput omics techniques became available, researchers are now able to analyze large sets of gene transcripts, proteins, and metabolites to identify molecules involved in disease development. Bioinformatics uses these data to perform network analyses and suggest possible interactions between metabolic processes and environmental factors. Obesity is known as one of the most closely related risk factors of colorectal cancer (CRC). Metabolic disturbances due to a positive energy balance may trigger and accelerate CRC development. In this review, we have summarized reports on genes, proteins and metabolites that are related to either obesity or CRC, and suggested candidate molecules linking obesity and CRC based on currently available literature. Possible application of bioinformatics for a large scale network analysis in studying cause-effect relationship between dietary components and CRC are suggested.

Bladder cancer SNP panel predicts susceptibility and survival

Bladder cancer is the fourth most common malignancy in men and the eighth most common in women in western countries. Single nucleotide polymorphisms (SNPs) in genes that regulate telomere maintenance, mitosis, inflammation, and apoptosis have not been assessed extensively for this disease. Using a population-based study with 832 bladder cancer cases and 1,191 controls, we assessed genetic variation in relation to cancer susceptibility or survival. Findings included an increased risk associated with variants in the methyl-metabolism gene, MTHFD2 (OR 1.7 95% CI 1.3-2.3), the telomerase TEP1 (OR 1.8 95% CI 1.2-2.6) and decreased risk associated with the inflammatory response gene variant IL8RB (OR 0.6 95% CI 0.5-0.9) compared to wild-type. Shorter survival was associated with apoptotic gene variants, including CASP9 (HR 1.8 95% CI 1.1-3.0). Variants in the detoxification gene EPHX1 experienced longer survival (HR 0.4 (95% CI 0.2-0.8). These genes can now be assessed in multiple study populations to identify and validate SNPs appropriate for clinical use.

Recreational physical activity modifies the association between a common GH1 polymorphism and colorectal cancer risk

Growth hormone may be associated with the development of colorectal cancer directly and/or indirectly via increased serum level of insulin-like growth factor (IGF-I). Regular physical activity can decrease insulin resistance and modulates IGF-I production. A common polymorphism in the GH1 gene, rs2665802, was previously shown to be associated with lower IGF-I levels and decreased colorectal cancer (CRC) risk. We investigated the association of this polymorphism and physical activity with colorectal cancer risk in a case-control study.

METHODS

The analysis includes 3,041 (1,402 cases and 1,639 controls) participants in the Molecular Epidemiology of Colorectal Cancer study, a population-based case-control study in Northern Israel. Analysis was carried out separately in two sets. The first set included 1,248 subjects (625 cases, 623 controls), and the second validation set consisted of 1,793 subjects (777 cases, 1,016 controls).

RESULTS

No association was found between the studied polymorphism and CRC risk. However, evaluation of gene environment interactions revealed an interaction between leisure time physical activity and the GH1 polymorphism, which was consistent in both sets (P(interaction) = 0.005). The genotype AA was associated with decreased risk of CRC among individuals who did not engage in any such activity (odds ratio, 0.76; 95% confidence interval, 0.52-0.98), whereas the same genotype was marginally associated with increased risk among individuals who reported physical activity (odds ratio, 1.38; 95% confidence interval, 0.98-1.94).

CONCLUSIONS

We found that the A allele of the rs2665802 polymorphism is associated with reduced risk of CRC only among physically inactive individuals, indicating an interaction between physical activity and the growth hormone/IGF-I system. A replication of the observed findings and further investigation of the underlying mechanism is warranted.

Insulin, insulin-like growth factors and colon cancer: a review of the evidence

Insulin and insulin-like growth factor (IGF) axes are major determinants of proliferation and apoptosis and thus may influence carcinogenesis. In various animal models, modulation of insulin and IGF-1 levels through various means, including direct infusion, energy excess or restriction, genetically induced obesity, dietary quality including fatty acid and sucrose content, inhibition of normal insulin secretion and pharmacologic inhibition of IGF-1, influences colonic carcinogenesis. Human evidence also associates high levels of insulin and IGF-1 with increased risk of colon cancer. Clinical conditions associated with high levels of insulin (noninsulin-dependent diabetes mellitus and hypertriglyceridemia) and IGF-1 (acromegaly) are related to increased risk of colon cancer, and increased circulating concentrations of insulin and IGF-1 are related to a higher risk of colonic neoplasia. Determinants and markers of hyperinsulinemia (physical inactivity, high body mass index, central adiposity) and high IGF-1 levels (tall stature) are also related to higher risk. Many studies indicate that dietary patterns that stimulate insulin resistance or secretion, including high consumption of sucrose, various sources of starch, a high glycemic index and high saturated fatty acid intake, are associated with a higher risk of colon cancer. Although additional environmental and genetic factors affect colon cancer, the incidence of this malignancy was invariably low before the technological advances that rendered sedentary lifestyles and obesity common, and increased availability of highly processed carbohydrates and saturated fatty acids. Efforts to counter these patterns are likely to have the most potential to reduce colon cancer incidence, as well as cardiovascular disease and diabetes mellitus.