Abstract
Resistance to androgen receptor (AR)-targeted therapies such as enzalutamide in castration-resistant prostate cancer (CRPC) often arises through lineage plasticity, yet the molecular mechanisms that define this process remain incompletely understood. While previous studies reported that Notch1 and Notch2 exert distinct and sometimes opposing effects in prostate cancer differentiation, the integrated role of Notch pathway activity has not been systematically explored. Here, we identify Notch signaling as a graded Rheostat that governs prostate cancer cell fate transitions. Integrative transcriptomic and functional analyses revealed that intermediate Notch activity maintains a stem-like progenitor state, whereas reduced or elevated signaling drives divergent differentiation trajectories toward luminal or neuroendocrine lineages, respectively. During CRPC progression and enzalutamide resistance, Notch signaling becomes dynamically rewired, peaking in progenitor-like populations that sustain plasticity and survival. Both CRISPR-mediated knockout and pharmacologic inhibition of Notch signaling depleted these progenitor cells and restored enzalutamide sensitivity. These findings demonstrate that the level, rather than the binary presence, of Notch signaling dictates lineage directionality and therapeutic response in CRPC, establishing it as a tunable and actionable driver of resistance.