NSCLC cells acquire resistance to AZD9291 by reducing CAMSAP3

AZD9291, also known as Osimertinib, is a highly potent and selective EGFR mutants (including exon 19 deletion, L858R/T790M) inhibitor that significantly inhibits EGFR phosphorylation signaling. However, acquired resistance to AZD9291 is inevitable in the treatment of non-small cell lung cancer (NSCLC). Microtubules, key cytoskeletal components involved in intracellular cargo transport, mediate EGFR-endosomal recycling, yet their specific role in AZD9291 resistance remains to be elucidated. In this study, we found that centrosomal microtubule formation was increased in AZD9291-resistant NSCLC cells, and calmodulin-regulated hemosiderin-associated protein 3 (CAMSAP3) was identified as the key molecule responsible for the change of microtubule morphology. Genetic modulation of CAMSAP3 expression through silencing or overexpression directly altered microtubule architecture and restored AZD9291 sensitivity. Furthermore, we demonstrated that full-length CAMSAP3 is essential for proper localization of the microtubule-dependent endosomal-lysosomal system. CAMSAP3 depletion caused EGFR translocation to the perinuclear microtubule organizing center (MTOC), thereby blocking plasma membrane recycling and promoting lysosomal degradation. These findings establish CAMSAP3 as a key regulator of EGFR signaling and AZD9291 response in NSCLC, suggesting its therapeutic potential for overcoming drug resistance in lung cancer.