Genome‐scale CRISPR–Cas9 screen identifies <i>PAICS</i> as a therapeutic target for <i>EGFR</i> wild‐type non‐small cell lung cancer

Abstract

Epidermal growth factor receptor-targeted (<i>EGFR</i>-targeted) therapies show promise for non-small cell lung cancer (NSCLC), but they are ineffective in a third of patients who lack <i>EGFR</i> mutations. This underlines the need for personalized treatments for patients with <i>EGFR</i> wild-type NSCLC. A genome-wide CRISPR/Cas9 screen has identified the enzyme phosphoribosylaminoimidazole carboxylase/phosphoribosylaminoimidazole succinocarboxamide synthetase (<i>PAICS</i>), which is vital in de novo purine biosynthesis and tumor development, as a potential drug target for <i>EGFR</i> wild-type NSCLC. We have further confirmed that PAICS expression is significantly increased in NSCLC tissues and correlates with poor patient prognosis. Knockdown of <i>PAICS</i> resulted in a marked reduction in both in vitro and in vivo proliferation of <i>EGFR</i> wild-type NSCLC cells. Additionally, <i>PAICS</i> silencing led to cell-cycle arrest in these cells, with genes involved in the cell cycle pathway being differentially expressed. Consistently, an increase in cell proliferation ability and colony number was observed in cells with upregulated <i>PAICS</i> in <i>EGFR</i> wild-type NSCLC. <i>PAICS</i> silencing also caused DNA damage and cell-cycle arrest by interacting with DNA repair genes. Moreover, decreased IMPDH2 activity and activated PI3K-AKT signaling were observed in NSCLC cells with <i>EGFR</i> mutations, which may compromise the effectiveness of <i>PAICS</i> knockdown. Therefore, <i>PAICS</i> plays an oncogenic role in <i>EGFR</i> wild-type NSCLC and represents a potential therapeutic target for this disease.