MYCL and lymphoma: On the other hand, mice transplanted with lymphoma cells from λ-Myc;CreER;Chek1Flox/D130A;Cdkn2a+/− mice (Fig 5C), and to a lesser extent lymphoma cells from λ-Myc;CreER;Chek1Flox/Flox;Cdkn2a+/− mice (Fig 5D), exhibited a rapid decrease in white blood cell count upon tamoxifen treatment.