TGFBR1 and cancer susceptibility.

Transforming growth factor beta (TGF-β) is a potent inhibitor of cell growth. TGFBR1 6A is a polymorphism consisting of a 9-base pair in-frame deletion within exon 1 of the type I TGF-β receptor (TGFBR1), which results in a receptor with decreased TGF-β signaling capability. The discovery of an association between TGFBR1*6A and cancer susceptibility led to the hypothesis that hypomorphic variants of the TGF-β signaling pathway may predispose to the development of cancer. This hypothesis was tested in vivo with the development of a mouse model of Tgfbr1 haploinsufficiency. Tgfbr1 (+/-) mice developed twice as many intestinal tumors as Tgfbr1 (+/+). Tgfbr1 haploinsufficiency was also associated with early onset adenocarcinoma and increased tumor cell proliferation. A case control study identified two haplotypes associated with constitutively decreased TGFBR1 and substantially increased colorectal cancer risk indicating that TGFBR1 may act as a potent modifier of cancer risk.