EXPRESSION OF THE FLT3 GENE IN HUMAN LEUKEMIA-LYMPHOMA CELL-LINES

The FLT3 gene encodes a protein that appears to function as a receptor for a hematopoietic growth factor; together with the KIT and FMS rece ptors, FLT3 belongs to the superfamily of receptors with tyrosine kina se activity. We examined the expression of FLT3 mRNA in 36 human leuke mia-lymphoma cell lines using Northern blot analysis. FLT3 transcripts were found in seven of seven pre B-ALL cell lines (derived from cases with pre B-acute lymphoblastic leukemia or chronic myeloid leukemia i n lymphoid blast crisis), and in one of six B-cell lines (namely in a cell line established from a hairy cell leukemia). FLT3 message was no t detected in five T-cell, five myeloid, four monocytic, four erythroi d and five megakaryocytic cell lines. Two major mRNA species were expr essed differentially by positive cell lines. KIT mRNA expression was a lso investigated in the same panel of cell lines, but was found only i n cell lines with erythroid and megakaryocytic features (and not in an y of the FLT3-positive cell lines). The pattern of expression of FLT3 contrasts with the transcription of FMS and KIT and suggests that the FLT3 product may play a role primarily in immature lymphoid cells.