Treatment-Resistant Prostate Cancer Stem Cell Plasticity Governed by MUC1-C Uncovers a Common target for ADC Treatment
Androgen receptor positive prostate cancer (PC), castration resistant prostate cancer (CRPC) and neuroendocrine prostate cancer (NEPC) represent a spectrum of malignancies that invariably become resistant to treatment with targeted and cytotoxic agents. There is no known common pathway responsible for these pleotropic mechanisms of resistance. The MUC1 gene is aberrantly expressed in CRPC and NEPC in association with poor clinical outcomes. The present results demonstrate that the oncogenic MUC1-C protein is necessary for resistance of (i) PC cells to enzalutamide (ENZ), and (ii) CRPC and NEPC cells to docetaxel (DTX). We show that MUC1-C-mediated ENZ and DTX resistance is conferred by upregulation of aerobic glycolysis and suppression of reactive oxygen species (ROS) necessary for self-renewal capacity. Common dependence of these drug-resistant phenotypes on MUC1-C for the cancer stem cell (CSC) state thus identified a potential new target for their treatment. cIn this context, we further demonstrate that targeting MUC1-C with an antibody-drug conjugate (ADC) is highly effective in suppressing (i) self-renewal of drug-resistant CRPC and NEPC CSCs and (ii) growth of t-NEPC tumor xenografts derived from drug-resistant cells and a patient with refractory disease. These findings reveal a shared MUC1-C-dependent pathway in drug-resistant CRPC and NEPC progression and identify MUC1-C as a target for their treatment with an ADC. Overall design: RNA Seq in H660 Cell lines with MUC1-C shRNA silencing. We compared DMSO and DOX treatment cells for differential gene expression analysis. MUC1shRNA (MISSION shRNA TRCN0000122938; Sigma, St. Louis, MO, USA)  was inserted into the pLKO-tet-puro vector (Plasmid #21915; Addgene, Cambridge, MA, USA) . Vector-transduced cells were selected for growth in 1–2 µg/ml puromycin. Cells were treated with 0.1% DMSO as the vehicle control or 500 ng/ml doxycycline (DOX; Millipore Sigma).