PI3K/mTOR dual inhibitor overcomes ceritinib resistance in ALK-rearranged NSCLC via both apoptosis and autophagy

Anaplastic lymphoma kinase-Tyrosine kinase inhibitors (ALK-TKIs) have substantially improved the treatment landscape for ALK-rearranged NSCLC; however, resistance to these agents remains a persistent clinical challenge. Whereas on-target resistance caused by secondary ALK mutations can be addressed with next-generation inhibitors, off-target resistance driven by activation of alternative RTKs is highly variable and often difficult to predict, making the development of a unifying therapeutic strategy complex. We investigated whether targeting the common downstream PI3K/AKT signaling pathway shared across multiple RTKs could provide an effective strategy to counter ALK-TKI resistance. In NSCLC cells resistant to ceritinib, a second-generation ALK-TKI, we observed that the PI3K/AKT signaling was robustly reactivated despite sustained suppression of ALK activity. Surprisingly, pharmacologic inhibition of AKT alone produced minimal anti-tumor effects, suggesting the presence of additional survival pathways beyond AKT itself. Based on previous reports showing that ALK contains an LC3-interacting region (LIR) motif whose dephosphorylation enhances autophagy, we investigated mTOR signaling as a potential compensatory pathway. Notably, PI3K/mTOR dual inhibition, rather than AKT inhibition alone, induced a markedly stronger anti-cancer response. Dual inhibition resulted in coordinated activation of apoptosis and autophagy-associated cell death, supported by significant changes in both apoptotic and autophagic markers, indicating a synergistic elimination of resistant cells. Because off-target resistance involves diverse and often unpredictable RTK-bypass activations, our findings suggest that PI3K/mTOR dual inhibition can target a broader range of downstream resistance mechanisms whenever ALK function is already pharmacologically suppressed. These results position PI3K/mTOR dual inhibitors as a promising therapeutic option for overcoming non-ALK-mutation-driven resistance in ALK-positive NSCLC, with potential translational relevance for patients who experience repeated TKI failure due to complex RTK-bypass signaling.