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. 2012 Jul;23(7):1127-38.
doi: 10.1007/s10552-012-9981-2. Epub 2012 May 8.

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

Temitope O Keku  1 , Adriana Vidal, Shannon Oliver, Catherine Hoyo, Ingrid J Hall, Oluwaseun Omofoye, Maya McDoom, Kendra Worley, Joseph Galanko, Robert S Sandler, Robert Millikan
Affiliations

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

Temitope O Keku et al. Cancer Causes Control. 2012 Jul.

Abstract

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.

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Figures

Fig. 1
Fig. 1. Distribution of IGF-I alleles among African Americans and Whites
IGF-I (CA)n polymorphic repeats ranged from n=11 (fragment size 174 bp) to n=24 repeats (fragment size 202 bp) and the most common repeat was n=19 (fragment size 192 bp). IGF-I (CA)19 is the most frequent allele among African American and Whites cases and controls
See this image and copyright information in PMC

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