Int7G24A Variant of Transforming Growth Factor-β Receptor Type I is Associated with Invasive Breast Cancer

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Purpose: The transforming growth factor-β (TGF-β) signaling pathway has been frequently implicated in breast cancer. An intronic variant (Int7G24A) of TGF-β receptor type I (TGFBR1) is associated with kidney and bladder cancers in our recent study. We hypothesize that this germline variant may be involved in development and progression of breast cancer.

Experimental Design: Case-control studies were designed from archived paraffin-embedded tissue specimens from the same geographic area with a homogenous ethnic population. We analyzed 223 patients (25 with preinvasive tumors and 198 with invasive and metastatic breast cancers) and 153 noncancer controls. The Int7G24A was identified by PCR-RFLP. Another germline deletion (TGFBR1*6A) and somatic mutations in theTGFBR1 were also analyzed by PCR and single-strand conformational polymorphism.

Results: The Int7G24A allele was evident in 32% of patients with preinvasive neoplasms and 48% of patients with invasive breast cancers compared with 26% controls (P = 0.00008). In addition, 11 (5.6%) homozygous Int7G24A carriers were found in patients with invasive breast cancers, whereas only 3 (2%) homozygous carriers were found in the control group. The TGFBR1*6A allele was not significantly associated with breast cancer patients and only one somatic mutation was found in 71 breast cancers.

Conclusion: These data suggest that the germline Int7G24A variant may represent a risk factor for invasive breast cancer and a marker for breast cancer progression. A separate study with a larger sample size is warranted to validate the association of the Int7G24Awith human breast cancer.