Germline DNA from 1054 BRCA-mutation-negative Hispanic women with hereditary BC (BC diagnosed at age <51 years, bilateral BC, breast and ovarian cancer, or BC diagnosed at ages 51-70 years with ≥2 first-degree or second-degree relatives who had BC diagnosed at age <70 years), 312 local controls, and 887 multiethnic cohort controls was sequenced and analyzed for 12 known and suspected, high-penetrance and moderate-penetrance cancer susceptibility genes (ataxia telangiectasia mutated [ATM], breast cancer 1 interacting protein C-terminal helicase 1 [BRIP1], cadherin 1 [CDH1], checkpoint kinase 2 [CHEK2], nibrin [NBN], neurofibromatosis type 1 [NF1], partner and localizer of BRCA2 [PALB2], phosphatase and tensin homolog [PTEN], RAD51 paralog 3 [RAD51C], RAD51D, serine/threonine kinase 11 [STK11], and TP53).
The youngest affected woman, not known to carry a mutation in BRCA1 or BRCA2, from 747 multiple-case breast cancer families participating in kConFab were selected for PALB2 mutation screening.
Our findings establish L35P as the first pathogenic missense mutation in PALB2 and directly demonstrate the requirement of the PALB2-BRCA1 interaction for breast cancer suppression.
We evaluated the contribution of PALB2 germline mutations in 122 Asian women with breast cancer, all of whom had significant family history of breast and other cancers.
PVs were identified in 9.3% of women tested; 51.5% of PVs were identified in genes other than breast cancer 1 (BRCA1) and BRCA2, including checkpoint kinase 2 (CHEK2) (11.7%), ataxia telangiectasia mutated (ATM; ATM serine/threonine kinase) (9.7%), and partner and localizer of BRCA2 (PALB2) (9.3%).
Furthermore, deletion of mouse Palb2, another breast cancer susceptibility gene with functional similarities to BRCA1, does not rescue Cobra1 knockout-associated mammary defects.
Some of the tagging single-nucleotide polymorphisms of 5 genes ( PALB2, TP53, Nijmegen breakage syndrome 1, PTEN, and BRCA1-interacting protein 1) involved in the monoubiquitinated FANCD2-DNA damage repair pathway were significantly associated with breast cancer risk.
To understand the role of these homologous recombination (HR) proteins in DNA repair, we functionally characterize effects of missense mutants of the PALB2 WD40 domain that have been reported in breast cancer patients.
Identification in 2002 of the Fanconi anaemia (FA) gene FANCD1 as BRCA2 and recent studies indicating that heterozygous mutations in FANCN/PALB2 and FANCJ/ BRIP1 predispose to breast cancer have emphasised an important connection between the FA and BRCA pathway.
Compared with non-carriers, PALB2 pathogenic mutation carriers developed breast cancer at a younger age (47.52 years vs. 51.35 years, p = 0.016) and were more likely to have triple-negative (24.1% vs. 13.4%, p = 0.022) or HER2 negative (87.0% vs. 74.2%, p = 0.031) breast cancer and large breast tumors (> 2 cm) at diagnosis (72.2% vs. 57.0%, p = 0.024).
Therefore, PALB2 mutations might be causative for FPC in a small subset of European families, especially in those with an additional occurrence of breast cancer.