Myeloid Calcium Binding Proteins: Expression in the Differentiated HL-60 Cells and Detection in Sera of Patients with Connective Tissue Diseases1

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Abstract
A differentiation antigen induced in 1,25-dihydroxyvitamin D5 (VD3)-treated HL-60 cells was identified as being comprised of the myeloid calcium binding proteins CaBP-p8 and -pl4 by determining its amino acid and DNA sequence. Northern blot analysis using a DNA fragment of the gene encoding p 14 as a probe indicated that the gene was not expressed in undifferentiated HL-60 cells but transcribed starting on day 1 after VD5 treatment. The level of p 14 mRNA reached a peak on day 2, then declined, and little mRNA remained on day 10, indicating that the p14 gene is activated once and then inactivated during HL-60 differentiation due to VD3. In contrast, thymidylate synthase (TSase) mRNA was present in undifferentiated HL-60 cells but disappeared quickly after VD3 treatment. Both p8 and p14 of CaBP were found at elevated levels in sera of some patients with connective tissue diseases [highly elevated in rheumatoid arthritis (RA), Sjogren's syndrome (SjS), systemic lupus erythematosus (SLE), and progressive systemic sclerosis (PSS), and moderately in polymyositis or dermatomyositis (PM/DM) and mixed connective tissue disease (MCTD)]. These results were in sharp contrast with the finding that p14 is always at a highly elevated level but little p8 is present in the sera of cystic fibrosis (CF) patients [Bruggen et al. (1988) Nature 331, 570).