The decreases observed in cyclin E, cyclin A, Cdc25A, and CDK2 protein levels and mRNA expression are consistent with a previous report that triptolide induced S phase arrest in multiple myeloma cells by inhibiting cyclin E, cyclin A, Cdc25A, and CDK2 expression and up-regulating p21 and p27 expression [69]. Here, CCNA2 is linked to plasma cell myeloma.