Pathogenic variants (PVs) in
BRCA
genes have been mainly associated with an increasing risk of triple negative breast cancer (TNBC). The contribution of PVs in non-BRCA genes to TNBC seems likely since the processing of homologous recombination repair of double-strand DNA breaks involves several genes. Here, we investigate the susceptibility of genetic variation of the
BRCA
and non-
BRCA
genes in 30 early-onset Moroccan women with TNBC.
Methods:
Targeted capture-based next generation sequencing (NGS) method was performed with a multigene panel testing (MGPT) for variant screening. Panel sequencing was performed with genes involved in hereditary predisposition to cancer and candidate genes whose involvement remains unclear using Illumina MiSeq platform. Interpretation was conducted by following the American College of Medical Genetics and Genomics-Association for Molecular Pathology (ACMG-AMP) criteria.
Results:
PVs were identified in 20% (6/30) of patients with TNBC. Of these, 16.7% (5/30) carried a
BRCA
PV [10% (3/30) in
BRCA1
, 6.7% (2/30) in
BRCA2
] and 6.6% (2/30) carried a non-
BRCA
PV. The identified PVs in
BRCA
genes (
BRCA1
c.798_799delTT,
BRCA1
c.3279delC,
BRCA2
c.1310_1313del, and
BRCA2
c.1658T>G) have been reported before and were classified as pathogenic. The identified founder PVs
BRCA1
c.798_799del and
BRCA2
c.1310_1313delAAGA represented 10% (3/30). Our MGPT allowed identification of several sequence variations in most investigated genes, among which we found novel truncating variations in
PALB2
and
BARD1
genes. The
PALB2
c.3290dup and
BARD1
c.1333G>T variants are classified as pathogenic. We also identified 42 variants of unknown/uncertain significance (VUS) in 70% (21/30) of patients with TNBC, including 50% (21/42) missense variants. The highest VUS rate was observed in
ATM
(13%, 4/30). Additionally, 35.7% (15/42) variants initially well-known as benign, likely benign or conflicting interpretations of pathogenicity have been reclassified as VUS according to ACMG-AMP.
Conclusions:
PALB2
and
BARD1
along with
BRCA
genetic screening could be helpful for a larger proportion of early-onset TNBC in Morocco.