TBX3 and melanoma: To this end, the AKT3 target site was mutated to either alanine (A), to abolish phosphorylation or glutamic acid (E), to mimic phosphorylation and the ME1402 and MM200 VGP melanoma cells were transiently transfected with either WT-TBX3, TBX3 S720A or TBX3 S720E mutant HA-expressing constructs.