CHEK2 and hepatocellular carcinoma: Later, Fang and Beland (2009) using a hepatoma cell line (HepG2) indicated that AZT caused a decrease in checkpoint kinase 1 (Chk1) and kinase 2 (Chk2) and an increase in phosphorylated Chk1 (Ser345) and Chk2 (Thr68).