Effects of homoharringtonine on several oncogene mRNAs in HL-60 cells

The effects of homoharringtonine (HHRT) on several oncogene mRNAs in HL-60 cells were investigated by molecular hybridization technique. The results showed that HHRT decreased the content of c-myc RNA in the cytoplasm but not in the nuclei. When the cells were exposed to HHRT at 40 nmol/L for I h. the contents of c-myc. N-ras. beta2 microglobulin mRNAs and rRNA declined by 82, 30, 3.5 and 0%. respectively. The effects of HHRT were related not only to its concentration. but also to its cell density. Further analysis indicated that HHRT accelerated the degradation of oncogene mRNA in the cytoplasm. but did not alter c-myc mRNA transportation. The change of c-myc mRNA occurred earlier than that of morphology or DNA protein biosyntheses. It is considered to be the primary effect of HHRT.