BRCA1 and osteosarcoma: Genome-wide gene expression profiling of high-grade osteosarcoma cell lines, in fact, showed an enrichment of differential expression in pathways important in genomic stability (Figure 2), with a role in cell cycle and checkpoint regulation (e.g. p53 signaling, G1/S and G2/M checkpoint regulation), DNA damage response (e.g. ATM signaling, role of BRCA1 in DNA damage response), and purine/pyrimidine metabolism.