Identifying the Intergenic <i>ALK</i> Fusion <i>LOC388942‐ALK</i> as a Driver of Non–Small Cell Lung Cancer

<i>ALK</i> fusions, such as the classic <i>EML4-ALK</i>, are known drivers of lung cancer and effective therapeutic targets. However, variant <i>ALK</i> fusions, including intergenic fusions like <i>LOC388942-ALK</i> (<i>LA</i>), have been detected in increasing numbers of patients, with their roles in tumorigenesis and ALK inhibitor resistance remaining unclear. Using CRISPR/Cas9, we generated the <i>LA</i> fusion in A549 and H441 cells, confirming elevated ALK expression via qRT-PCR and immunohistochemistry (IHC) staining. Functional analyses showed that <i>LA</i> significantly promoted tumor growth in vitro and in vivo while conferring increased resistance to alectinib. RNA-seq revealed upregulation of the <i>FOS</i> pathway in <i>LA</i> tumors, identifying <i>FOS</i> as a potential therapeutic target. Subsequently, we demonstrated that FOS disruption and inhibition sensitized <i>LA</i> tumors to treatment. RNA-seq profiling demonstrated that <i>FOS</i> depletion in <i>LOC388942-ALK</i> tumor significantly downregulated multiple oncogenic pathways related to cell cycle progression, DNA replication fidelity, and extracellular matrix remodeling, suggesting a pivotal role of <i>FOS</i> in maintaining tumor growth. These findings establish <i>LOC388942-ALK</i> as a novel oncogenic driver in lung cancer, highlighting its role in tumor growth and ALK inhibitor resistance. Targeting <i>FOS</i> may provide a promising therapeutic strategy for tumors harboring this intergenic fusion.