Growth of Kit expressing MTHC in liquid culture. Parental MTHC maintained in murine GM-CSF, WTKit expressing MTHC maintained in human SCF, and V816Kit expressing MTHC maintained without factor were washed and seeded in duplicate wells at 2,000 cells per 200 μL. The upper three panels show the number of viable cells recovered (mean ± standard deviation [SD]) at day 0, 2, and 4 after culture in medium supplemented with (A) murine GM-CSF, (B) human SCF, and (C) no added factor. The middle three panels show the average number of cell divisions of the viable populations in the presence of (D) murine GM-CSF, (E) human SCF, and (F ) no added factor. The bottom three panels show the survival of cells relative to the total viable cells at day 0 in culture containing (G) murine GM-CSF, (H) human SCF, and (I) no added factor.