Simultaneous CK2/TNIK/Dyrk1 inhibition by 108600 suppresses triple negative breast cancer stem cells and chemotherapy-resistant disease

Abstract Triple negative breast cancer (TNBC) remains clinically challenging as patients have heterogeneous responses to current standard of care therapies. Chemotherapy sensitivity is a strong predictor of long-term outcomes for patients, and incomplete response of early stage disease to chemotherapy treatment is associated with a much higher risk of disease relapse and metastatic progression, often occurring within a short time from initial diagnosis. Therefore, treatment strategies that target chemotherapy-resistant TNBC and/or enhance chemosensitivity would improve outcomes for these high-risk patients. Breast cancer stem cell-like cells (BCSC) have been proposed to represent a chemotherapy-resistant subpopulation within the tumor which are also responsible for tumor initiation, progression and metastases. Targeting this population could lead to improved TNBC disease control. We have identified a novel multi-kinase inhibitor 108600 from a screen for inhibitors of this TNBC BCSC population. 108600 treatment suppresses growth, colony and mammosphere forming capacity of the BCSC population. Treatment with 108600 induces G2M arrest and eventual apoptosis of TNBC cells in vitro and of TNBC xenografts in vivo , and overcomes chemotherapy (paclitaxel) resistance of triple negative patient-derived xenografts (PDX). Finally, treatment with 108600 and chemotherapy suppressed the growth of already established TNBC metastases, providing additional support for the clinical translation of this agent to clinical trials.