A recessive variant of XRCC4 predisposes to non- BRCA1/2 breast cancer in chinese women and impairs the DNA damage response via dysregulated nuclear localization.

XRCC4 plays a crucial role in the non-homologous end joining pathway that maintains genome stability. In this two-stage case-control study with 1,764 non-BRCA1/2 breast cancer patients and 1,623 cancer-free controls, we investigated the contribution of genetic variants of XRCC4 to breast cancer susceptibility in Chinese women. We identified a recessive missense variant, rs3734091 (c.739G>T, p.Ala247Ser), of XRCC4 that was significantly associated with an increased risk of breast cancer (odds ratio [OR] = 3.92, P = 0.007), particularly with the risk of developing triple-negative breast cancer (OR = 18.65, P < 0.0001). This p.Ala247Ser variant disturbed the nuclear localization of XRCC4 in cells homozygous for the rs3734091-T allele but not in heterozygous cells at both the cellular and tissue levels. In heterozygous cells, wild-type XRCC4 facilitated the nuclear localization of the XRCC4A247S mutant, thus compensating for the impaired localization of XRCC4A247S. This provided a biological mechanism by which rs3734091 conferred an increased susceptibility to non-BRCA1/2 breast cancer exclusively under a recessive model. Further functional analyses revealed that p.Ala247Ser impaired the DNA damage repair capacity and ultimately perturbed genomic stability. Taken together, our findings document the role of XRCC4 in non-BRCA1/2 breast cancer predisposition and reveal its underlying biological mechanism of action.

Clinico-pathological features and prognosis of invasive micropapillary carcinoma compared to invasive ductal carcinoma: a population-based study from China.

BACKGROUND: Invasive micropapillary carcinoma (IMPC) of the breast is a rare subtype of breast cancer that is associated with a high incidence of regional lymph node metastases and a poor clinical outcome. However, the clinico-pathological features and prognostic factors of IMPC are not well understood. PATIENTS AND METHODS: A total of 188 IMPC cases and 1,289 invasive ductal carcinoma (IDC) cases were included. The clinical features, breast cancer-specific survival (BCSS) and recurrence/metastasis-free survival (RFS) of the patients were compared between these two groups. RESULTS: The IMPC patients exhibited more features of aggressive carcinoma than the IDC patients, including larger tumor size, higher tumor stage, a greater proportion of nodal involvement and an increased incidence of lymphovascular invasion. Patients with IMPC had lower 5-year BCSS and RFS rates (75.9% and 67.1%, respectively) than patients with IDC (89.5% and 84.5%, respectively). Compared to IDC patients, the patients with IMPC had a significantly higher percentage of stage III breast cancer (51.3% versus 21.7%). In a stage-matched Kaplan-Meier analysis, the patients with stage III IMPC had lower 5-year BCSS and RFS rates than patients with stage III IDC (BCSS, P = 0.004; RFS, P = 0.034). A multivariate analysis revealed that TNM stage was an independent prognostic factor for patients with IMPC. The proportion of cancers with a luminal-like subtype was significantly higher in IMPC than in IDC (P<0.001). However, after matching by molecular subtype, the patients with IMPC had significantly worse clinical outcomes than patients with IDC. CONCLUSIONS: In Chinese women, IMPCs displayed more aggressive behaviors than IDCs, resulting in poorer clinical outcomes for patients with IMPC, regardless of a favorable molecular subtype. Our findings illustrate that the poorer survival of patients with IMPC might be due to an increased incidence and aggressiveness of tumors in TNM stage III.