1530 Background: PALB2 (Partner and Localizer of BRCA2) is recently recognized as a breast cancer predisposition gene, which plays a critical role in genome maintenance via interacting with BRCA1/2 and RAD51 when DNA break. Germline loss-of-function mutations in PALB2 lead to increased breast cancer risk. Since the germline mutation frequency of PALB2 is much less than BRCA1/2, the distinct mutation spectrum of PALB2 is still obscure. Therefore, we assessed the mutational frequency, spectrum and predictors of the PALB2 gene in a sequential series of Chinese breast cancer patients from our Research DNA Bank, to verify the utility of PALB2 genetic testing in Chinese population. Methods: We examined Chinese breast cancer cases (n = 2279) who agreed to participate in research DNA banking, recruited from 1990 through 2016. To identify the mutations, complete coding sequence and intron–exon boundaries of PALB2 were screened with Next Generation Sequencing. Personal and family histories were synchronously collected for mutation identification. Results: Among the 2279 breast cancer patients, 307 patients were familial breast cancer cases and the rest 1972 patients were sporadic breast cancer cases. PALB2 mutation carriers accounted for 7.8% (n = 24) and 4.8% (n = 95) in familial and sporadic breast cancer cohort separately. In total, 31 missense, 4 nonsense, 3 frameshift, 3 splicing and 1 codon mutations of PALB2 were identified in this study. Among the pathologic variants, PALB2 c.1744C > T, c.2748+1G > A, c.2749-1G > C, c.3114-1G > A were newly identified in sporadic breast cancer, and c.3271delC newly found in familial breast cancer. Based on in silico analysis, a total of 6 potential damaging missense variants were novelly found in this study, among which the PALB2 c.3035C > T was detected in both sporadic and familial breast cancer. Conclusions: Our data presents the germline mutation status of PALB2 in Chinese patients with breast cancer, suggesting that loss-of-function germline mutations of PALB2 are important in both familial and sporadic breast cancer. Clinically, this information may be helpful in genetic counseling of breast cancer patients with PALB2 germline mutation.
P4: CIRCULATING MIRNA PROFILES POINT TO DYSREGULATION IN TGFBETA/SMAD3 TUMOR SUPPRESSOR SIGNATURE IN BRCA POSITIVE BREAST CANCER PATIENTS
