Macrophages prolong the survival of PDX-RS cells in vitro, and their depletion delays the expansion of adoptively transferred TCL1 leukemia cells in vivo. (A) Representative annexin V/propidium iodide (PI) analysis of RS1316 cells cultured for 72 hours in the presence or absence of PC-isolated Mφ (left); summary of 3 independent experiments using RS1316 and RS9737 cells (right). (B) Representative annexin V/PI analysis of RS1316 cells cultured for 72 hours in the presence or absence of bone marrow (BM)-derived Mφ generated by differentiating BM mononuclear cells for 4 days in culture with M-CSF (left); summary of 3 independent experiments using RS1316 and RS9737 cells (right). (C) Percentage of viable RS1316 or RS9737 cells following coculture with peritoneal cavity–derived macrophages that had previously been exposed to 1μM R191 for 24 hours. Macrophages were washed to remove R191 prior to coculture with the RS-PDX cells. Viability was assessed by annexin V/PI staining. Graph represents summary of 3 independent experiments. (D) Analysis of leukemia cell counts (CD5⁺/CD19⁺) in peripheral blood, peritoneal cavity, and spleen of mice treated with vehicle control (n = 6), mice treated for 21 days with R221 (n = 5), or mice pretreated for 14 days with R221 prior to tumor transfer and then treated for additional 21 days (n = 5). Statistical analysis was done using 1-way ANOVA with Tukey test for multiple comparisons.