Rab23 Drives Cutaneous Squamous Cell Carcinoma Invasion via ERK-Mediated Autophagy Activation

Background: Cutaneous squamous cell carcinoma (cSCC) is the second most prevalent non-melanoma skin cancer worldwide, with increasing incidence and considerable mortality following metastasis. Ras-associated binding protein 23 (Rab23) has been implicated in cSCC progression, but its molecular mechanisms remain incompletely understood. Methods: Rab23, Beclin1, and LC3-II protein expression was compared across human cSCC, actinic keratosis, and normal skin tissues. Rab23-dependent changes in autophagy-related markers, autophagic vacuoles, migration, invasion, and wound healing were investigated in oral SCC-derived Sa3 cells and cSCC models A431 and HSC-5. GTP dependence, responses to rapamycin and chloroquine, and AKT/mTOR and MEK/ERK1/2 signaling were assessed, including MEK1/2 inhibition with U0126. Public transcriptomic and spatial transcriptomic datasets were also analyzed. Results: Rab23 protein expression was significantly elevated in cSCC lesions compared with normal skin and actinic keratosis, accompanied by increased Beclin1 and LC3-II levels, and correlated positively with both markers. Rab23 overexpression increased Beclin1 and LC3-II expression and decreased p62 in a GTP-dependent manner. It also enhanced autophagic vacuole formation, migration, invasion, and wound healing. Rapamycin potentiated these effects, whereas chloroquine abrogated them. Rab23 activated both AKT/mTOR and MEK/ERK1/2 signaling; however, U0126 abolished Rab23-induced autophagy marker upregulation and migratory capacity. Transcriptomic and spatial transcriptomic analyses further supported the clinical relevance of the Rab23-ERK-autophagy axis in SCC aggressiveness. Conclusions: Rab23 promotes cSCC invasion, at least in part, through ERK-dependent autophagy enhancement, highlighting this signaling axis as a potential therapeutic target for cSCC.