Targeting RAC1 in glioblastoma: prognostic value, immune landscape, and small molecule therapeutic potential

RAC1, a Rho GTPase family member involved in cell motility, is irregularly expressed in solid tumors. However, the specific tumor cell states in which RAC1 operates and its influence on the immune microenvironment remain poorly understood.

RAC1 expression and prognostic value were evaluated across cancers using TCGA, HPA, CPTAC, and GEO data. After identifying GBM as the most prognostically relevant cancer type, Lasso-Cox regression and multivariate Cox analysis confirmed RAC1 as the key prognostic member among Rho GTPase family members. RAC1 expression was validated in GBM cell lines and mouse tumor tissues by qPCR and Western blotting. Effects on proliferation, migration, and invasion were assessed by CCK-8, wound healing, and Transwell assays. Immune infiltration, immunotherapy responsiveness, and drug sensitivity were analyzed using TCGA data. Single-cell RNA sequencing analysis was performed to resolve RAC1 expression across tumor cell states and the immune microenvironment. Molecular docking and in vitro CCK-8 assays were used to evaluate Palbociclib as a candidate drug.

RAC1 was upregulated in most cancers, with the highest prognostic accuracy in GBM. Lasso-Cox regression retained RAC1 across OS, DSS, and PFI endpoints, and multivariate Cox analysis confirmed it as the sole family member with HR exceeding 2 (HR = 2.61, P = 0.003). NSC23766 suppressed GBM cell proliferation, migration, and invasion without altering total RAC1 protein, confirming dependence on RAC1 activation state. Single-cell analysis revealed RAC1 enrichment in the NPC-like tumor state, independent of cell cycle. RAC1-high cells exhibited PI3K-AKT-mTOR and IFN-gamma pathway activation with upregulated MHC-I but absent PD-L1, explaining ICI resistance. Palbociclib inhibited GBM cell viability in a dose- and time-dependent manner.

RAC1 serves as a prognostic biomarker and therapeutic stratification indicator in GBM, marking IFN-responsive tumor subpopulations that may benefit from CDK4/6 inhibitor-based strategies rather than ICI monotherapy.