Metronomic CPA induced more than 30 genes important for induction of apoptosis, as seen in both human U251 tumor cells (human array), as well as in host cells of mice bearing U251 or 9L gliomas (mouse array) (Additional file 1: Tables S2A and S5A), consistent with our earlier finding that CPA kills 9L glioma cells by activating caspase 9-dependent apoptosis [99]. This evidence concerns the gene CASP9 and central nervous system cancer.