KIT and gastrointestinal stromal tumor: In GIST-T1 cells, M-COPA treatment significantly decreased the levels of phospho-AKT (pAKT), pERK, and pSTAT5 (to 0.16 ± 0.07, 0.17 ± 0.12, and 0.28 ± 0.09, respectively), indicating that KIT could not cause downstream activation in the ER.