Roles of ABCB1 gene polymorphisms and haplotype in susceptibility to breast carcinoma risk and clinical outcomes

Genetic variants of ABCB1 gene contributed to cancer susceptibility and interindividual differences in chemotherapy response. Therefore, we investigated the relevance between genetic variations in ABCB1 gene and both risk and clinical outcomes of breast carcinoma.

A case–control study was performed on the SNPs C3435T, C1236T and G2677T/A in 1,173 Chinese breast carcinoma patients and 1,244 age- and sex-matched controls. These SNPs were typed by PCR–restriction fragment length polymorphism assays.

We found the following: (1) ABCB1 C3435T, G2677T/A variants and haplotype 3435T–1236T–2677T significantly increased the risk of breast carcinoma [adjusted OR (95 % CI): 1.281 (1.021–1.285), 1.326 (1.182–1.487) and 1.707 (1.498–1.945), respectively]. (2) A significantly enhanced therapeutic response was observed in both C3435T variants and haplotype 3435T–1236T–2677T after neoadjuvant anthracycline-based chemotherapy (n = 148) [adjusted OR (95 % CI): 2.695 (1.172–6.211) and 8.064 (1.085–58.823), respectively]. (3) Cox proportional hazards regression models showed that the hazards ratio (HR) for progression-free survival (PFS) associated with C3435T CC genotype was 1.664 (95 % CI: 1.022–2.708, P = 0.041). Kaplan–Meier curve showed that C3435T CC carriers had a poor prognosis than those with CT/TT carriers after anthracycline-based chemotherapy (P = 0.043, n = 762). Furthermore, ABCB1 C3435T variants showed a significantly prolonged both PFS and overall survival (OS) in patients with triple-negative (ER−/PR−/HER2−) status (P = 0.001 and P = 0.016, respectively; n = 135). In addition, there was a significantly longer OS in patients with HER2-negative status who had G2677T/A variants (P = 0.036, n = 487). However, we did not find statistically significant association between C1236T genotypes and the risk or prognosis of breast carcinoma.