ATF4 and cholangiocarcinoma: Recent studies have reported that multiple kinases interfere with tumor progression by affecting purine de novo pathway via regulation of important transcription factors or intervention with rate-limiting enzymes: DYRK3 regulates ATF4 transcriptional activity and inhibits PPAT to suppress hepatocellular carcinoma proliferation and metastasis [287]; UHMK1 modulates the NCOA3/ATF4 axis and may activates ATIC to promote gastric cancer development [288]; CLK3 stabilizes the USP13/Fbxl14/c-Myc axis to enhance cholangiocarcinoma aggressiveness [289].