| Abstract: |
To test the feasibility of using the human epidermal growth factor receptor (EGFR) as a model for growth factor receptor action in human hematopoietic cells, we infected Burkitt lymphoma cells (Namalwa) with a recombinant amphotrophic retrovirus containing a thymidine kinase promoter-driven human EGFR complementary DNA and the neomycin resistance gene. Neomycin-resistant cells expressing surface EGFR were selected by cell sorting using anti-EGFR monoclonal antibody 225. The selected cells expressed a M, 170,000 protein immunoprecipitated by monoclonal antibody 225 and apparently identical to EGFR from A431 carcinoma cells. Infected Namalwa cells expressed 42,000 epidermal growth factor (EGF) binding sites/cell, and Scatchard analysis showed two affinities (K¿~ 5 n\i and ~0.5 nM). EGFR autophosphorylation was detected using antiphosphotyrosine antibodies after 5 min exposure to EGF. EGF binding induced rapid EGFR internalization u,, = 9 min) and mobilization of transferrin receptors to the cell surface within 1 min. In fetal bovine serum-containing and serum-free cultures, EGF did not stimulate Namalwa cell proliferation. However, in the presence of 1.25% dimethyl sulfoxide (DIVISO), EGF caused a dose-dependent increase in DNA synthesis. DMSO induced a cell cycle block in G,, which was partially reversed by EGF. DIVISO induced changes in some B-cell markers suggesting cellular differentiation and increased surface EGF receptor number. Cells grown in DMSO and EGF were established as an EGF-dependent cell line for >12 weeks, whereas cells grown in DMSO without EGF died within 1-2 weeks. Namalwa cells expressing EGFR demonstrated more rapid tumor growth in athymic mice. These studies demonstrate expression of functional 1(, I K mediating early biochemical and growth responses in a human hematopoietic cell, and indicate that EGFR can be used as an effective model in human hematopoietic cells. Results using DMSO are consistent with studies in other human leukemia cells indicating that agents inducing differentiation can restore growth factor dependence in previously factor-independent leukemia cells. © 1991, American Association for Cancer Research. All rights reserved. |
| Keywords: |
epidermal growth factor; human cell; animal; mice; cell division; gene expression; epidermal growth factor receptor; cell differentiation; receptor, epidermal growth factor; tumor cells, cultured; transfection; tyrosine; phosphorylation; genetic vectors; dimethyl sulfoxide; mice, nude; recombinant proteins; dna, neoplasm; virus infection; neoplasm transplantation; endocytosis; burkitt lymphoma; complementary dna; retrovirus; in vitro; phosphotyrosine; blotting, southern; human; priority journal; article; support, u.s. gov't, p.h.s.
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