previous work has shown that the presence of a phorbol ester tumor promoter , phorbol 12-myristate 13-acetate ( pma ) , during a single-step selection for methotrexate ( mtx ) -resistant mouse 3t6 cells results in an up to 100-fold increase in the incidence of mtx-resistant , colony-forming cells .
C0031586
phorbol ester
C0039654
phorbol