Oncogenic Potential of Truncated-Gli3 via the Gsk3β/Gli3/AR-V7 Axis in Castration-Resistant Prostate Cancer

The functional activation of the androgen receptor (AR) and its interplay with the aberrant Hh/Gli cascade are pivotal in the progression of castration-resistant prostate cancer (CRPC) and resistance to AR-targeted therapies. Our study unveils a novel role of the truncated form of Gli (t-Gli3) in advancing CRPC. Investigation into Gli3 regulation revealed a Smo-independent mechanism for its activation. Despite lacking a transactivation domain, t-Gli3 relies on androgen receptor variant 7 (AR-V7) for its action. Mechanistically, Gsk3β activation leads to the t-Gli3 generation, and inhibition of Gsk3β supports the accumulation of full-length Gli3 through a non-canonical mechanism. Knockdown of Gsk3β (Gsk3β KD) reduces CRPC cell proliferation, induces apoptosis via mitochondrial fragmentation, and triggers metabolomic reprogramming. Orthotropic implantation of Gsk3β KD cells in the mouse prostate results in tumor growth retardation compared to scramble control cells. RNA-seq analysis of Gsk3β KD reveals upregulation of pathways associated with apoptosis, tumor suppressor pathway, and downregulation of oncogenic pathway relative to control. Furthermore, combinational use of a Gsk3β inhibitor with anti-Smo or Gli1 significantly inhibits the growth of CRPC cells, which are resistant to individual Smo or Gli1 inhibitor targeting. Intriguingly, solely targeting Gli3 proves effective in inhibiting CRPC cell growth. Overall, our study underscores the clinical significance of Gli3, emphasizing t-Gli3, and provides novel insights into the interplay of the Gsk3β/t-Gli3/AR-V7 axis in CRPC.