Uptake of cytosol by tumor cells from lymphocytes causes arrest of cell cycle and prolonged mouse survival.

<div><p>(A)BM185 cell were labeled with CellVue to distinguish the population of tumor cells from CMFDA-labeled lymphocytes. Tumor cells and splenocytes were incubated in equal number for 4 h and uptake of CMFDA was assessed by flow cytometry. Further on, BM185 were separated by cell sorting in non-fluorescent and fluorescent cells.</p> <p>(B)Assessment of transfer of membrane components from CellVue labeled BM185 to lymphocytes after exposure of cells in a ration 1:1 for 4 h. CellVue incorporates into lipid regions of cell membranes.</p> <p>(C)³H thymidine incorporation of BM185 cells exposed to CMFDA-labeled splenocytes from BALB/c and subsequently separated by FACS cell sorting in tumor cells which exchanged cytosol with mouse lymphocytes (CMFDA⁺) or those that remained unaffected (CMFDA^-). Cells were cultured for 3 days in 96 well plates and 16 h after addition of radioactive thymidine. </p> <p>(D)Survival curve of BALB/c mice after i.v. injection of 1x10⁴ BM185 cells (5 mice per group/experiment, the survival curve represents two independent experiments, thus n = 10) with or without uptake of CMFDA after exposure to CMFDA-labeled murine splenocytes. The course of the BM185 elicited leukemia is highly reproducible. The survival of the BM185 cells without the uptake of lymphocyte derived cytosol corresponds completely to this known decline of viablitiy. In contrast, mice injected with BM185 incorporated splenocytes derived cytosol survived significantly longer (p ≤ 0.0042). </p> <p>Results are shown as representative scatter-grams or summarizing 2-4 independent experiments as mean ± SEM.</p>