p210 leukemia expresses the p55 TNFR and is directly sensitive to TNFR-mediated apoptosis. (A) In vitro TNFR levels on P815 and p210 tumor cells were measured by flow cytometry, in which gray represents isotype control and black the TNFR staining. Ex vivo B6D2F1 or B6C3F1 mice were transplanted with B6 BM and P815 or P210 leukemia, respectively. At the time point at which mice would normally succumb to leukemia burden, leukemic cells were analyzed by flow cytometry for p55 and p75 TNFR expression. (B) Tumor cell lines were assessed for sensitivity to TNFR-mediated killing by annexin V staining. A total of 105 cells was incubated for 5 hours with recombinant mouse TNF (150 ng/mL), LTα3 (600 ng/mL), or media alone. Data shown are representative of a minimum of 3 replicate experiments. (C) TNFR-mediated killing of the p210 line is dose dependent. Cells were treated, as described in panel B, with escalating doses of TNF.
