As an example of pyrimidine nucleoside analog, fludarabine (2-fluoro-ara-AMP) has synergic effect with nutlin-3a in chronic lymphocytic leukemia (CLL) by increasing p53 levels, inducing Bax conformational changes and apoptosis in p53wt cells [48]. The gene discussed is TP53; the disease is B-cell chronic lymphocytic leukemia.