CHEK1 and neoplasm: Besides the well known mechanisms regulating both activation and expression of Chk1 that have already been described10, 19, 20, 21, 22, 23, Chk1 is also regulated at the post-transcriptional level by microRNAs (miRNAs)24, 25 which are key regulators of tumor growth and response to chemotherapy26, 27, 28.