Detection of c-fms and CSF-1 RNA by in situ hybridization.

Recent studies have demonstrated by Northern blot analysis that both the c-fms proto-oncogene and the CSF-1 gene are expressed during human monocytic differentiation. In order to examine c-fms and CSF-1 expression at the cellular level, we have applied alkaline phosphatase detection of biotinylated v-fms and CSF-1 cDNA probes in situ. Using this approach, we demonstrate that c-fms and CSF-1 transcripts are detectable in HL 60 cells induced along the monocytic lineage but not in uninduced cells. The specific detection of these transcripts is further supported by the absence of histochemical staining in RNase-treated cells and when using pBR322 plasmid without insert as the biotinylated probe. Finally, the results indicate that most of the induced HL-60 cells have detectable levels of both c-fms and CSF-1 RNA. This approach should be useful for studying expression of these genes in populations of leukemic blasts and normal hematopoietic cells.