ARTS mimetic small molecules restore the normal-like phenotype in breast pre-malignant 3D organoids

Treatment of patients diagnosed at very early stages of Breast cancer (BC) is a major medical concern. Patients are either over-treated with surgeries and chemotherapy or monitored periodically, which could lead to initiation of BC during that period. ARTS is a pro-apoptotic and a tumor suppressor protein. ARTS promotes cell death by binding directly and degrading two major anti-apoptotic proteins, XIAP and Bcl-2. We have used the isogenic MCF10 cell lines and 3D organoids to study BC progression. M1 cells represent normal epithelium, M2-pre-malignant and M3 are malignant breast cells. We showed that M2 cells exhibit an aberrant, non-functional form of ARTS. Furthermore, silencing only ARTS in normal M1 cells induced their conversion to pre-malignant M2 phenotype. Using a computational structure-based screen we identified an ARTS mimetic (AM) small molecule which induced the degradation of XIAP and Bcl-2, caspase 3 and 9 activation and apoptosis in various cancer cell lines. Surprisingly, treatment of M2 organoids with AM did not induce apoptosis. Rather, AM promoted the reversion of M2 pre-malignant organoids into M1 normal phenotype. We hypothesize that ARTS plays an important role in maintaining breast tissue homeostasis. Furthermore, loss of ARTS alone can mediate the conversion of normal breast cells to pre-malignant phenotype. Restoring the function of ARTS by using ARTS mimetics can promote the reversion of the premalignant cells into normal phenotype. We propose a new approach for prevention of breast cancer by treating early staged premalignant patients, thereby avoiding the initiation of breast cancer.