Furthermore, in breast cancer patients with clinically confirmed disease recurrence on AI therapy, ex vivo treatment of the resistant tumors with dasatinib in combination with letrozole maintained ERα expression, reduced Ki67, and switched off S100β expression in comparison to letrozole treatment alone (n = 2) (Fig. 5d and Additional file 2: Table S4). The gene discussed is ESR1; the disease is breast carcinoma.