Abstract: Activating transcription factor 4 (ATF4), one of the activating transcription factors, belongs to the cyclic AMP response element binding protein family. The expression of ATF4 is up-regulated by tumor micro-environmental factors. And ATF4 regulates the processes of tumor growth, infiltration, metastasis, apoptosis and drug resistance. Therefore, ATF4 might serve as a potential therapeutic target in cancer.