Abstract
The effect of recombinant tumor necrosis factor-alpha (rTNF-alpha) on the primary leukemic blasts and leukemic cell lines derived from children with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) was studied. The proliferation of leukemic cells from the bone marrow of 11 of 13 patients (seven at diagnosis, four in relapse) and from the 697 (BCP-ALL) cell line was significantly inhibited by rTNF-alpha at the lowest dose tested (0.1 ng/mL), as measured by 3H-TdR uptake. The degree of inhibition was variable, ranging from 17% to 78%. Furthermore, a dose-dependent inhibitory effect was observed, with approximately 70% mean inhibition of DNA synthesis detected when cells from 12 of 13 patients were incubated with 100 ng/mL of rTNF-alpha for 3 days. In contrast, rTNF-alpha did not inhibit another BCP-ALL cell line (EU-1/ALL) established recently in our laboratory. Studies indicated that the TNF-alpha gene was expressed by the primary leukemic blasts of one TNF-resistant case in his third relapse and by EU-1 cells. Also, TNF-alpha protein was detected by Western blot analysis and enzyme-linked immunoabsorbent assay in the supernatant of EU-1 cells; this is the first report of TNF production by a BCP-ALL cell lines. The production of TNF-alpha mRNA and protein was not detected in the 697 cell line and in the primary leukemic blasts from six patients (four at diagnosis, two in relapse) whose leukemic cells were inhibited by TNF. The partially purified TNF-alpha obtained from the EU-1 cell line also suppressed the proliferation of TNF-sensitive primary leukemic cells, and this inhibitory activity was abolished by an anti- TNF-alpha specific antibody. Our results demonstrate that TNF-alpha is an inhibitor of in vitro proliferation of BCP-ALL cells from most patients. The TNF-resistant leukemic cells from a few patients and the EU-1 cell line express TNF mRNA, suggesting that the induction of TNF gene expression is associated with the development of TNF resistance.
