EIF2AK4 and small cell lung carcinoma: More recently, in small-cell lung cancer models, a CRISPR-Cas9 screen implicated the kinase GCN2 (encoded by EIF2AK4) as being rapidly activated by AZD1775 via an off-target mechanism; GCN2 triggers the integrated stress response (ISR) and contributes to the cytotoxicity of the drug [21].