D816V mutation in the KIT gene activation loop has greater cell-proliferative and anti-apoptotic ability than N822K...

In core-binding factor acute myeloid leukemia (CBF-AML), there have been conflicting reports regarding the status as an unfavorable prognostic factor of mutation in the KIT gene, the significance of which remains unclear. We previously reported that prognoses differ between the KIT D816V and N822K mutations. In the present study, we compared in vitro the cell-proliferative and anti-apoptotic ability of D816V and N822K. We transduced these KIT mutations into the interleukin-3-dependent cell line TF-1 (TF-1 KIT^D816V, TF-1 KIT^N822K). When these KIT mutations were transduced into TF-1 cells, the cells acquired a proliferative ability independent of growth factor, which was significantly higher in TF-1 KIT^D816V than in TF-1 KIT^N822K (p = 0.022). When Ara-C was added in the absence of growth factor, Annexin V assay revealed that TF-1 KIT^D816V was associated with a significantly lower proportion of apoptotic cells than TF-1 KIT^N822K (p < 0.001). Regarding signal transduction pathways, both KIT D816V and KIT N822K underwent autophosphorylation in the absence of growth factor. This was followed in KIT D816V by downstream activation of the SRC family kinase pathway in addition to the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway, and in KIT N822K by downstream activation of the mitogen-activated protein kinase (MAPK) pathway in addition to the JAK/STAT pathway. These findings establish that D816V and N822K mutations are situated closely on the KIT receptor activation loop, but D816V has greater cell-proliferative and anti-apoptotic ability than N822K.