Identification of FEN1 as a prognostic marker and novel therapeutic target in gastric cancer harboring TP53 mutations

e16057 Background: As a common tumor suppressor gene, TP53 gene mutation leads to persistent activation of multiple downstream effectors that drive the cancer phenotype. Approximately 50% of gastric cancer (GC) patients harbor TP53 mutations, which confer stronger tumor biology and shorter overall survival (OS). Given that TP53-mutated proteins have proven difficult to target directly, identifying genes that function closely with TP53 and targeting these genes appears to be a promising therapeutic strategy for TP53-mutated GC patients. Methods: TP53 functionally sensitive genes were identified by evaluating the correlation between gene-dependent scores from CRISPR knockout screens and TP53 mRNA expression in TP53 mutant GC cell lines in the Cancer Cell Line Encyclopedia (CCLE) database. If the correlation coefficient is ≥0.6, the gene was considered as TP53 functional sensitive gene. Then TP53 functionally sensitive genes associated with prognosis were screened out in The Cancer Genome Atlas (TCGA). PockDrug-Server was used to predict drug susceptibility of candidate genes. Results: The results showed that in 9 GC cell lines with TP53 mutations and 14 with TP53 wild-type, 4 genes (KLF5, FEN1, CCNA2, CCNB1) were identified as TP53 functional sensitive genes. Among the 4 genes, only FEN1 expression was significantly correlated with OS (HR=1.85, 95CI 1.06−3.26, P=0.029). Multivariate Cox regression analysis showed that high FEN1 expression was an independent predictor of prognosis in TP53-mutated GC. Pocket druggability prediction analysis presented that FEN1 had 8 drug-able pockets, four of which all have a druggability score of 0.8 or higher, including one pocket with a score of 1. Conclusions: These findings suggested that FEN1 was promising prognostic marker and therapeutic target in TP53-mutated GC.