Oncoplacental protein SP1--a constitutive and inducible late
differentiation marker of the human myelomonocytic lineage
M Heikinheimo, CG Gahmberg, H Bohn and LC Andersson
Department of Biochemistry, Children's Hospital, University of Helsinki,
Finland.
The oncoplacental protein SP1 is found in large quantities in human
placenta, amniotic fluid, and pregnancy serum. Low levels have been
reported in association with malignancy but also in healthy nonpregnant
individuals. By indirect immunofluorescence, fluorescence-activated cell
sorting, and immunoprecipitation we here demonstrate the presence of SP1
both on the surface and in the cytoplasm of human granulocytes but not in
earlier myeloid progenitor cells in bone marrow. Lymphocytes did not
contain the protein, and only trace amounts could be found in the cytoplasm
of blood monocytes. A major glycoprotein with an apparent mol wt of 90,000
was obtained by immunoprecipitation of surface-labeled granulocytes.
Cultivated blood monocytes, while adhering to surfaces or forming
multinuclear giant cells, displayed a strong membrane and cytoplasmic
expression of SP1. Treatment of the myeloid leukemia cell line ML-2 with
tetraphorbol acetate (TPA) strongly induced SP1 in the membrane and
cytoplasm as revealed by immunofluorescence and polyacrylamide gel
electrophoresis (PAGE) of immunoprecipitates from lysates of surface
radiolabeled cells. The induction of synthesis of SP1 in TPA-treated cells
was confirmed by immunoprecipitation from lysates of cells metabolically
labeled with 35S-methionine. Human lymphoblastoid and erythroleukemic cell
lines did not express SP1 either before or after induced differentiation.
Thus SP1 provides a late differentiation marker for the myelomonocytic
lineage and is strongly induced during macrophage differentiation or by TPA
treatment of ML-2 cells.
Volume 70,
Issue 5,
pp. 1279-1283,
11/01/1987
Copyright © 1987 by The American Society of Hematology
