The level of c-kit transcripts is similarly downregulated in M-07e cells upon interaction with stroma cells. The level is upregulated when the stroma is removed. RNA (12 μg/lane) was subjected to Northern analysis. M-07e cells grown in suspension with rhIL-3 or alternatively on stroma for 1 and 2 weeks were analyzed for c-kit expression. In addition, an aliquot of the M-07e cells was removed from the stroma (at days 7 and 14, respectively) and was grown for 1 day in suspension with IL-3 added. In parallel, TF-1 was used as a control for downregulation and upregulation (lanes 1 through 3). Lane 1, TF-1; lane 2, TF-1, 2 weeks on MS-5; lane 3, TF-1, 2 weeks on MS-5, 1 day in suspension (+GM-CSF); lane 4, MS-5; lane 5, M-07e; lane 6, M-07e, 1 week on MS-5; lane 7, M-07e, 1 week on MS-5, 1 day in suspension (+IL-3); lane 8, M-07e, 2 weeks on MS-5; lane 9, M-07e, 2 weeks on MS-5, 1 day in suspension (+IL-3).