A) After subcutaneous inoculation of FVB mice with 1.5×105 KPL-3M cells, ATRA (purple box) treatment was started on day 5 and given daily until the end of the study, and anti-PD-1 (blue box) therapy was given in five doses as indicated. Growth curves and corresponding tumor weights at the time of euthanasia are presented. Results are representative of at least three biological replicates of 6–10 mice per group. B) 1.5×105 KPL-3M cells were injected subcutaneously on the flank of NSG mice, and mice were treated daily with either vehicle control or ATRA. * P<0.05; **, P< 0.01; ****, P< 0.0001.