Identification of Somatic and Germline Mutations Influencing Treatment Outcomes and Disease Susceptibility in Tunisian Triple-Negative Breast Cancer Using Next-Generation Sequencing

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype characterized by marked molecular heterogeneity and limited targeted therapeutic options. Its incidence is rising in many low- and middle-income countries, where genetic profiling of affected patients remains largely unexplored despite evident clinical disparities. This study aimed to characterize, for the first time in a Tunisian cohort, the spectrum of germline and somatic mutations in TNBC patients and to assess their potential impact on therapeutic response. Targeted next-generation sequencing (NGS) of hotspot regions across 50 cancer-related genes was performed in twelve patients using the AmpliSeq for Illumina Cancer Hotspot Panel v2, applied to both tumor tissues and matched adjacent non-tumoral tissues. Bioinformatics analysis revealed recurrent germline variants present in all samples, notably in TP53 (rs1042522), CSF1R (rs2066933), FGFR3 (rs7688609), RET (rs1800861), KDR (rs7692791), and PDGFRA (rs1873778). In tumor tissues, 32 deleterious somatic variants were detected across 20 oncogenes, with TP53 emerging as the most frequently mutated gene (58%). Distinct mutational patterns were observed in relation to treatment response. Notably, the co-occurrence of AKT1 (rs121434592) and TP53 (rs876660754) was observed in a patient with treatment resistance, whereas an in-frame deletion in NOTCH1 (p.Val1578del) was uniquely detected in patients who subsequently experienced disease recurrence. These findings provide the first comprehensive characterization of germline and somatic alterations in Tunisian TNBC patients, representing a North African cohort. They reveal the heterogeneity of mutation patterns linked to treatment response, and emphasize the importance of genomic profiling into clinical practice and guide personalized therapeutic strategies.