EXPRESSION OF BOMAPIN, A NOVEL HUMAN SERPIN, IN NORMAL MALIGNANT HEMATOPOIESIS AND IN THE MONOCYTIC CELL-LINES THP-1 AND AML-193/

Our group recently cloned the cDNA-encoding bomapin, a member of the s erine protease inhibitor (serpin) superfamily, from a human bone marro w cDNA library (J Biol Chem 270:2675, 1995). To understand its express ion within the hematopoietic compartment, RNA extracted from bone marr ow or peripheral blood from normal donors and patients with leukemia w as reverse transcribed and analyzed by polymerase chain reaction (PCR) . Bomapin PCR products were readily detected in normal bone marrow, wh ich was designated as a medium mRNA level. In peripheral blood, bomapi n expression was low or undetectable in normal donors (n = 6) and pati ents with chronic lymphocytic leukemia (n = 6). Blood from patients wi th chronic myeloid leukemia (n = 6), chronic myelomonocytic leukemia ( n = 6), acute myeloid leukemia (n = 5), and acute lymphocytic leukemia (n = 5) exhibited low to medium levels of bomapin expression. Further more, a high level of bomapin expression was detected in one individua l with acute monocytic leukemia. These data suggest that bomapin expre ssion may be elevated in hematopoietic cells of monocytic lineage. The refore, we analyzed the expression of bomapin within cell lines that e xhibited characteristics of the monocytic lineage. Bomapin FOR product s were detected in the monocytic THP-1 and AML-193 cell lines but not in CRL 7607, CRL 7541, KG-1, or K562 cells. Induction of bomapin trans cripts was not detected in the latter series of cell lines following a 24-hour treatment with phorbol myristate acetate (PMA, 10(-8) mol/L) or tumor necrosis factor-alpha (TNF-alpha, 30 U/mL), whereas treatment of THP-1 or AML-193 cells with these agents reduced the intensity of the bomapin PCR products. Northern blotting confirmed these results an d showed that the expression of bomapin in THP-1 cells was downregulat ed over a 4-day period by PMA and, to a lesser extent, TNF-alpha. Immu noblotting was used to show the presence of a 40-kD protein in THP-1 c ytosol preparations. Bomapin antigen levels were correspondingly reduc ed after treatment with PMA. Because PMA and TNF-alpha, induce monocyt ic differentiation in THP-1 and AML-193 cells, these data increase the possibility that bomapin may play a role in the regulation of proteas e activities specifically in early stages of cellular differentiation. (C) 1998 by The American Society of Hematology.