KLHL18 inhibits the proliferation, migration, and invasion of non-small cell lung cancer by inhibiting PI3K/PD-L1 axis activity

The expression of Kelch-like protein 18 (KLHL18) in non-small cell lung cancer (NSCLC) is lower than that in normal lung tissue according to the Gene Expression Profiling Interactive Analysis database. KLHL18 is a BTB domain protein and binds cullin 3 (CUL3). However, whether this complex participates in ubiquitination-mediated protein degradation in NSCLC is unclear. Therefore, we aimed to investigate the role of KLHL18 in human NSCLC cells. We found that KLHL18 is downregulated in cancer cells and is associated with poor prognosis. Further, its expression was significantly associated with tumor node metastasis (TNM) stage, lymph node metastasis, and tumor size. In vitro analysis of NSCLC cells showed that overexpressing KLHL18 inhibited cell proliferation, migration, and invasion. We found that the tumor-inhibitory effect of the KLHL18 protein was achieved by promoting the ubiquitination and degradation of phosphatidylinositol 3-kinase (PI3K) p85[alpha] and inhibiting the expression of PD-L1 protein, ultimately preventing tumor cell immune escape. Our results identified the tumor-suppressive mechanism of KLHL18 and suggested that it is closely related to NSCLC occurrence and development. Further investigation of the underlying mechanism may provide new targets for NSCLC treatment.