A role for ATF3 in tumourigenesis has been implicated through its documented role as an apoptotic factor in cancer models, whose mechanism may be related to ATF3's role in transcriptional regulation of a number of regulators of apoptosis and cell proliferation including pro-apoptotic factor, GADD153/CHOP and cell cycle factor, cyclin D1, respectively [40,41]. The gene discussed is CCND1; the disease is cancer.