The GLI3–Androgen Receptor Axis: A Feedback Circuit Sustaining Shh Signaling in Prostate Cancer

The Hedgehog (Hh) signaling pathway regulates key cellular processes, such as proliferation, differentiation, and morphogenesis. Although its canonical activation involves ligand binding to PTCH1, which activates Smoothened (SMO), noncanonical features of the pathway significantly contribute to cancer progression, particularly in prostate cancer (PCa). GLI3, a central transcription factor in the Hh pathway, can act as a repressor or activator depending on posttranslational modifications. In androgen-deprived PCa, GLI3 plays a critical role in driving castration-resistant phenotypes by interacting with the androgen receptor (AR), particularly the AR-V7 variant. This interaction enhances tumor survival and growth even under androgen deprivation therapy (ADT). Aberrant GLI3 activity is further driven by mutations in upstream regulators such as SPOP and MED12, which contribute to the progression of both prostate and other malignancies. Preclinical studies have shown promise in reducing tumor cell proliferation and migration, and in inducing apoptosis, by pharmacologically inhibiting the GLI3 pathway with SMO antagonists or GSK3β inhibitors. Recent evidence also highlights reciprocal interactions between Sonic Hedgehog (Shh) signaling and the AR that sustain tumor growth under ADT. GLI3 engagement with AR reinforces AR-dependent transcription, supporting tumor progression through noncanonical pathways. These findings suggest that targeting GLI3, particularly in combination with AR inhibition, could effectively overcome castration resistance and improve outcomes in patients with castration-resistant prostate cancer (CRPC). This review explores the role of GLI3 in both canonical and noncanonical Hh signaling, its potential as a therapeutic target, and future directions for overcoming resistance in Hh-driven cancers.