Construction and mechanism of a small cell lung cancer cell line resistant to EP chemotherapy scheme

To construct the etoposide (VP-16) combined with cisplatin (DDP) chemotherapy scheme (EP chemotherapy scheme) resistant small cell lung cancer (SCLC) cell line H446/EP and to identify the drug resistance characteristics and explore the mechanism.

NCI-H446 cells were treated with increasing concentrations of VP-16 and DDP to construct an H446/EP cell line. H446/EP and NCI-H446 cells were used as the research objects. The cell viability was detected by MTT assay, and the resistance index (RI) of H446/EP cells was calculated. Cell cloning assay and Incucyte cell proliferation (label-free) assay were used to detect cell proliferation ability. Transcriptome sequencing was performed to analyze the enrichment of differentially expressed genes (DEGs) in the 2 cell lines. Western blotting was applied to detect the protein expression levels of drug resistance, DNA damage repair (DDR), and autophagy markers.

MTT assay showed that the resistance index (RI) of H446/EP cells to VP-16, DDP, and DOX were 6.14, 3.43, and 1.96, respectively. The results of cell cloning assay and Incucyte cell proliferation assay indicated that the proliferation ability was significantly higher in the H446/EP cells than the NCI-H446 cells (P<0.01). Transcriptome sequencing and pathway enrichment analysis displayed that the DEGs between H446/EP and NCI-H446 cells were enriched in tumor chemoresistance, DDR, and autophagy pathways. Western blot results showed the expression levels of MRP1, BCRP, RAD51, γ-H2AX, and LC3-II/LC3-I were significantly increased, and that of p62 was obviously decreased in the H446/EP cells when compared with the NCI-H446 cells (P<0.05).

An EP chemotherapy-resistant H446/EP cell line is successfully constructed. Stronger proliferation ability, increased expression of efflux transporters, and enhanced DDR and autophagy may be the mechanisms of the resistance of SCLC to EP chemotherapy scheme.