We have reported previously that the human promyelocytic
leukemia cell line HL-60, in its undifferentiated state, is devoid of cytoplasmic
intermediate filament proteins and nuclear
lamins A and C, but does express
lamin B. Using immunofluorescence and immunoblotting techniques, we have further investigated the expression of
vimentin and
lamins A and C during differentiation of these
tumor cells along the macrophage or granulocytic pathway in response to the inducing effects of the
phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) or
dimethyl sulfoxide. Our results show that, while the expression of
lamin B remains largely unchanged, the synthesis of
vimentin and
lamins A and C is dramatically enhanced during the maturation of HL-60 cells along both hemopoietic pathways. Northern blot analysis of cellular RNAs isolated from untreated and TPA-treated HL-60 cell populations as well as from control HeLa cells was performed using two
oligonucleotides, one complementary to the 5' region common to human
lamin A/C mRNAs and the other to the 5' region of hamster
vimentin mRNA. Very low but still detectable amounts of
vimentin and
lamin A/C mRNAs were found in untreated HL-60 cell population, in accordance with the detection of small quantities of
vimentin and
lamins A and C in these populations. This is probably due to the presence of a small number of spontaneously differentiating cells. On the other hand, strong signals comparable to those obtained with
RNA from control HeLa cells were detected for the three
mRNA species from TPA-treated cells.(ABSTRACT TRUNCATED AT 250 WORDS)