In order to understand whether such signaling pathway contributes to the effect of UCN-01 on CRC-SCs, we evaluated the expression levels of total and phosphorylated PDK1 (pS241), PKCα/β II (pT638/41), CDC25C (pS216) and Chk1 (pS345) in two representative CRC-SC lines. The gene discussed is CHEK1; the disease is colorectal carcinoma.