Moreover, KEGG pathway enrichment reveals that the DEGs were mainly enriched in the PI3K-Akt signalling pathway, the MAPK signalling pathway, the tight junction, the cell adhesion molecules, leukocyte transendothelial migration, small cell lung cancer and the TGF-beta signalling pathway, and those pathways have been shown to be closely associated with promoting the acquired EGFR-TKI resistance and the TME 4, 45, 46. The gene discussed is PIK3CA; the disease is small cell lung carcinoma.