LAPTM4B promotes gefitinib resistance and tumor stemness in non-small cell lung cancer by stabilizing RPS3 through inhibiting its ubiquitination.

Gefitinib resistance remains a major obstacle to the effective treatment of non-small cell lung cancer (NSCLC), and the underlying molecular mechanisms have not yet been fully elucidated. Lysosomal-associated transmembrane protein 4B (LAPTM4B) has been shown to be involved in cancer progression, but its specific role in gefitinib resistance and the prognosis of NSCLC patients remains unclear. In this study, we conducted functional experiments including CCK-8, Transwell, and tumor sphere formation assays in LAPTM4B-overexpressing or knockdown HCC827 cells and gefitinib-resistant HCC827-R cells. In vivo validation was performed using a NSCLC xenograft model in nude mice. The results showed that LAPTM4B was upregulated in NSCLC, with a further increase in gefitinib-resistant NSCLC samples. Functional experiments demonstrated that knockdown or overexpression of LAPTM4B regulated gefitinib resistance, cell migration, and stemness in HCC827 cells. Furthermore, RPS3 was identified as a key interacting target of LAPTM4B, and LAPTM4B could enhance the stability of RPS3 protein by inhibiting its ubiquitination. In vivo xenograft experiments showed that knockdown of LAPTM4B significantly suppressed tumor growth and tumor stemness, and this inhibitory effect could be reversed by overexpression of RPS3. Collectively, our findings indicate that LAPTM4B promotes gefitinib resistance and NSCLC progression by stabilizing RPS3 protein through inhibiting its ubiquitination, and the LAPTM4B-RPS3 axis may serve as a potential therapeutic target for overcoming gefitinib resistance in NSCLC.