CHEK1 and breast cancer: The 120-gene signature contains genes involved in DNA metabolism and replication (Dhfr, Top2a, Tyms), DNA repair (Claspin, Rrm1, Pola1), chromosome maintenance (Plk4, Mcm genes), cell cycle regulation (Pk2, Chk1), cell replication and proliferation (Cdc28, Ki67, Pcna), microtubule stabilization (Kif11, Stmn1), and apoptosis (Birc5, Casp2), suggesting that the expression of genes contained within this signature could be vital for the survival and maintenance of this aggressive form of human breast cancer.