Acquisition and reversal of glioblastoma chemoresistance are mediated by the Rho GTPase pathway

Glioblastoma (GBM) are highly aggressive tumors treated mainly with surgery, radiotherapy, and chemotherapy. Innovative multimodal therapies are needed, targeting the immune system, tumor metabolism, and cell signaling. Our research focuses on the role of the actin cytoskeleton and Rho GTPases in modulating DNA damage repair and therapeutic sensitivity in GBM cells. We developed GBM sublines resistant to temozolomide (TMZ) and cisplatin (CP), and assessed actin stress fiber organization, Rho pathway activity, and resistance phenotype. TMZ-resistant clones exhibited increased Rho pathway activity, elevated p53 and DNA double-strand break (DSB) repair pathways, but reduced MMR protein levels. Importantly, Rho GTPase inhibition restored TMZ-resistant clones sensitivity to TMZ and CP, counteracting chemoresistance. While both drugs reduced DNA repair capacity in normal GBM cells--exacerbated by Rho inhibition--TMZ-resistant clones with overactivated Rho pathways did not show this effect. This response was p53-wild-type dependent, as p53-mutant GBM cells were unresponsive to Rho inhibition. However, p53-mutant cells treated with PRIMA-1 showed restored sensitivity to chemotherapeutics with Rho inhibition. Furthermore, modulation of the actin cytoskeleton and Rho GTPases affected sensitivity and viability in GBM spheroid models exposed to chemotherapy. In summary, Rho pathway activity and actin cytoskeleton dynamics are critical for both the development and reversal of chemoresistance in GBM tumors. STATEMENT OF SIGNIFICANCEChemoresistance in glioblastomas modulates the Rho GTPases pathway and actin cytoskeleton, while negatively affecting DNA repair. Downmodulating the actin circuitry in resistant GBMs sensitizes them to TMZ and CP drugs.