CYP2C9 and breast neoplasm: CYP2C enzymes are known to contribute to the activation of prodrugs such as the oxazaphosphorines [65], including CPA shown in Figure 2C. Both RNA and protein-level expression of CYP2C9 and gene-level expression of CYP2C8 have been reported in a small cohort of 10 breast tumour samples [66].