Abstract 2569: Evaluation of TGFBR2 gene polymorphisms with TGF-βRII protein expression in breast cancer tissues: results from the Shanghai Breast Cancer Study

The transforming growth factor (TGF)-β signaling pathway plays a significant role in the carcinogenic process of breast cancer. We have previously shown that the minor G allele of the single nucleotide polymorphism (SNP) rs1078985 in the TGFBR2 gene was associated with reduced risk of breast cancer. To further investigate the role of genetic variants of TGFBR2 in breast cancer etiology, we systematically evaluated common genetic variants (minor allele frequency > 5%) in the TGFBR2 gene (80 SNPs) for associations with TGF-βRII protein expression in breast tissue from 970 women with invasive breast cancer who participated in the Shanghai Breast Cancer Study. Expression of TGF-βRII was detected by immunofluorescence staining. The immunofluorescence signals were designated as negative, positive, or strong-positive based on a modified Allred scoring system. Associations of genetic polymorphisms with TGF-βRII protein expression were estimated using linear regression models adjusted for age at diagnosis. Variant alleles of SNPs rs1078985 and rs3773634 were associated with increased TGF-βRII expression intensity in breast cancer tissue (P = 0.0004 for rs1078985 and 0.0022 for rs3773634). However, these two SNPs were not associated with TGF-βRII protein expression intensity in adjacent normal tissue or in in situ breast cancer tissue. The sample sizes for the adjacent normal tissue and in situ breast cancer groups were small. SNPs rs1078985 (located in intron 3) and rs3773634 (located in intron 4) are approximately 7 Kb apart with strong linkage disequilibrium (r2=0.962 in Asians). We then performed electrophoretic mobility shift assays to examine whether the DNA sequence containing SNPs rs1078985 or rs3773634 interacts with nuclear proteins and whether the single nucleotide change in these polymorphic sites alters protein-DNA interactions. The variant G allele of SNP rs1078985 altered both DNA-protein complex intensity and patterns in breast cancer MCF7 and MDA231 cells, but not in MCF10A cells, whereas SNP rs3773634 did not change DNA-protein intensity or patterns in any of the three types of cells. Our data suggest that common variants in the TGFBR2 gene are associated with TGF-βRII protein expression in breast cancer tissue. The variant G allele of SNP rs1078985 may affect transcription factor binding, and in turn, increase TGF-βRII protein expression in breast tumor tissue. Characterization of genetic variants and their associations with protein expression in