Since cell proliferation signatures were associated with a higher sensitivity to Chk1-inhibition and since MCL is the only lymphoma bearing the t(11;14)(q13;q32) [1] that leads to an increased activation of the CDK/cyclins involved in G1-S transition [4], we next asked if the deregulation of the cyclin D1 might be correlated with the high sensitivity to Chk1 inhibitor. This evidence concerns the gene CHEK1 and mantle cell lymphoma.