Human-fms gene is retained in acute lymphoblastic leukemia cells with del(5)(q32)

Cytogenetic and molecular investigations of NALM 6 cells (a pre-B-lymphoblastic acute leukemia cell line) revealed them to contain both alleles of the c-fms gene, though the cells had chromosomal changes of 5q- and 12p+. The amount of DNA fragments hybridized to the 1.4 kb PstI/PstI v-fms probe in the NALM 6 cells was approximately the same, when compared with cells of an Epstein-Barr virus-transformed lymphoblastoid cell line with a normal karyotype. Chromosome banding analysis revealed that the breakpoint of the 5q- in the NALM 6 cells was at the proximal portion of the 5q32 band. Chromosomal in situ hybridization of NALM 6 cells showed a significant accumulation of grains on the terminal portions of the abnormal 5q- chromosomes (5q32), as well as on the normal chromosomes #5 with a peak at 5q32-q33. These findings indicate that the human c-fms gene is not deleted in the lymphoblastic leukemia cells with a 5q- studied by us and that it does not show rearrangement or amplification. Thus, the results indicate that a difference in the dosage of the c-fms gene in acute lymphoblastic leukemia cells with the 5q- versus that in cells with the 5q- change in nonlymphocytic neoplasia; in the latter a hemizgosity of the c-fms gene has been suggested.