PLAT and neoplasm: To determine whether the MCPyV T antigens function as tumor initiators, we treated groups of Rosa26-LSL-MCPyV168 (n = 17), K14E6/E7 (n = 13), and K14Cre-MCPyV168 (n = 12) with TPA only (15 nmol) twice a week for 20 weeks (Figure 1B).