Uncommon TGFBRI allele is not associated with increased susceptibility to colon cancer

Abstract

Previous studies have suggested that an allele of the transforming growth factor-beta type I receptor (TGFBRI) gene that codes for six instead of the usual nine alanines in a polyalanine repeat is associated with an increased susceptibility to colon cancer, and that the six-alanine homozygote is seen only in individuals with some form of cancer. We evaluated this TGFBRI polymorphism in a population-based sample of 252 individuals with colon cancer and 362 age- and gender-matched controls from the state of Utah. TGFBRI genotypes were determined by PCR amplification and length determination of the polyalanine repeat. In addition to the common nine-alanine (9A) allele, we identified six- (6A), eight- (8A), ten- (10A), eleven- (11A), and twelve-alanine (12A) TGFBRI alleles. 6A/9A heterozygotes were seen in similar percentages of colon cancer cases (18.3%) and controls (16.0%). 6A/6A homozygotes were slightly more common in controls than in colon cancer cases (1.4% vs. 0.8%), and none of the controls with the 6A/6A genotype had any of the non-colonic cancers reported in previous studies. We conclude that the 6A TGFBRI allele is not associated with an increased susceptibility to colon cancer at the population level, and that the 6A/6A homozygote is not restricted to individuals with some form of cancer.

Phenotypic and Genetic Analyses of the Varroa Sensitive Hygienic Trait in Russian Honey Bee (Hymenoptera: Apidae) Colonies

“…After 6–7 days post introduction, the frame was removed and infestation of the same cohort of brood was determined by pulling 200 cells of purple-eyed to tan-bodied pupae. The examination of 200 brood cells per colony has been the standard procedure for determining brood infestation in our earlier studies [ 24 , 26 , 28 , 37 ] and has been adopted as the optimum number to determine the brood infestation of a colony by [ 38 ]. By measuring the infestation level of the same cohort of capped brood before and after introduction into the test colony, we can conclude that a reduction in infestation is related to hygienic removal of infested brood [ 37 ].…”

“…No overwhelming resistance mechanism has been identified [ 23 ]. However, an increased phoretic period of Varroa on adult bees leads to mites being more susceptible to the bee’s grooming behaviour [ 24 ]. Using the freeze-killed brood (FKB) assay, [ 25 ] showed that RHB colonies consistently removed dead brood at levels high enough to be considered hygienic (>95% brood removed within 48 h over two assays).…”

Lack of an Association between the TGFBR1*6A Variant and Colorectal Cancer Risk

“…The TGFBR1*6A allele has been proposed to act as a low-penetrance susceptibility allele for a number of malignancies (7). Although some studies have suggested that the TGFBR1*6A allele confers an elevated risk of colorectal cancer, findings have been inconsistent (8,9).…”

Genetic Studies of Colorectal Cancer

“…In a systematic review of the literature, four previously published articles reporting TGFBR1*6A genotype and risk of colorectal cancer were identified and used for metaanalyses (Pasche et al 2004;Pasche et al 1999;Samowitz et al 2001;Stefanovska et al 2001). Two of these provided data on more than one case-control study.…”