GLUT3 enhances chemosensitivity in glioblastoma by transporting temozolomide and capecitabine

Glioblastoma multiforme (GBM), the most aggressive brain cancer, is highly resistant to chemotherapy, which profoundly affects patient survival and prognosis. Temozolomide (TMZ), the sole first-line chemotherapeutic agent for GBM, faces substantial challenges in overcoming this resistance. Despite the belief that TMZ is well-absorbed in the small intestine and can effectively cross the blood-brain barrier due to its small molecular size, emerging evidence suggests that its uptake is not merely through passive diffusion across the lipid bilayer but is regulated by Wnt signaling. However, the precise mechanism governing TMZ uptake remains elusive. GLUT3, which is highly expressed in GBM and primarily functions as a glucose transporter, has emerged as a promising therapeutic target. This study demonstrates that GLUT3 upregulation in GBM cells enhances sensitivity to both TMZ and capecitabine (CAPE). Uptake assays revealed that GLUT3 overexpression (OE) or knockdown (KD) significantly influenced the uptake of these chemotherapeutic agents. We further validated the interaction between GLUT3 and TMZ/CAPE through molecular docking, dynamics simulations, and MST assay. Site-directed mutagenesis identified eight amino acids involved in GLUT3-mediated binding and transport of TMZ and CAPE. A mouse xenograft model confirmed that GLUT3 OE significantly increases TMZ/CAPE uptake and cytotoxicity, particularly under fasting conditions. Our findings establish GLUT3 as a multifunctional transporter for TMZ, CAPE, and glucose, thereby enhancing GBM chemosensitivity. These results challenge the prevailing notion that GLUT3's role in tumors is solely related to glucose transport. Our work suggests tailoring chemotherapy based on GLUT3 expression level in GBM patients and reevaluating GLUT inhibitors in combination with chemotherapeutic agents.