Combination of androgen receptor inhibitor enzalutamide with the CDK4/6 inhibitor ribociclib in triple negative breast cancer cells

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer (BC) that currently lacks specific therapy options. Thus, chemotherapy continues to be the primary treatment, and developing novel targets is a top clinical focus. The androgen receptor (AR) has emerged as a therapeutic target in a subtype of TNBC, with substantial clinical benefits shown in various clinical studies. Numerous studies have shown that cancer is associated with changes in components of the cell cycle machinery. Although cell cycle cyclin-dependent kinase (CDK) 4/6 inhibitors are successful in the treatment of ER-positive BC, they are not helpful in the treatment of patients with TNBC. We investigated the possibility of combining CDK4/6 inhibitor(ribociclib) with AR inhibitor(enzalutamide) in the AR-positive TNBC cell line. Ribociclib showed an inhibitory effect in TNBC cells. Additionally, we found that enzalutamide reduced cell migration/invasion, clonogenic capacity, cell cycle progression, and cell growth in AR-positive cells. Enzalutamide therapy could increase the cytostatic impact of ribociclib in AR(+) TNBC cells. Furthermore, dual inhibition of AR and CDK4/6 demonstrated synergy in an AR(+) TNBC model compared to each treatment alone.