CHEK1 and colorectal carcinoma: Immunoblotting analysis demonstrated that UCN-01 alone or in combination with irinotecan affects the ATR-mediated phosphorylation of Chk1 and PKC directly blocking the activation of the Chk1 target CDC25C (Figure 4B), confirming the contribution of several targets in determining the response of CRC-SCs to UCN-01.