| Popis: |
Signals from many receptor-ligand interactions are mediated by enhancement of phospholipid hydrolysis which generates metabolic intermediates stimulating protein kinase C (PKC) and elevating cellular calcium. Pharmacologic agents such as phorbol 12, 13-dibutyrate (PDBu) and ionomycin selectively stimulate PKC and elevate intracellular calcium to directly stimulate downstream mechanisms critical to cell growth and function. This study examines the effects of PDBu, ionomycin, and rIL-2 on childhood ALL blasts of early B lineage with respect to various aspects of cell activation, including DNA synthesis, induction of non-MHC restricted tumoricidal activity, and changes in morphology and phenotype. Five childhood ALL samples were tested. A marked heterogeneity was seen among the ALL samples with respect to in vitro growth following manipulation with PDBu, ionomycin, and/or rIL-2, whereas normal peripheral blood lymphocytes (PBL) were consistently stimulated to grow with the combination of PDBu and ionomycin. Growth responsiveness did not appear to correlate with morphologic or phenotypic classification of the leukemia samples. Four of the five leukemia samples developed substantial non-MHC restricted cytotoxicity to K562 (natural killer cell (NK) sensitive) and Daudi (NK resistant) targets in response to rIL-2. This functional cytotoxic response correlated with morphologic changes in the cells and the appearance of granules. Phenotypic analyses of the ALL samples at the time of their peak cytotoxic function were consistent with the fresh ALL phenotype and showed no major change in cell populations. Three of the five ALL samples also retained rIL-2 induced cytotoxic capabilities when exposed simultaneously to the combination of PDBu and ionomycin, whereas rIL-2 induced tumoricidal activity in normal PBL and bone marrow cultures was inhibited by these reagents. These data show that morphologically and phenotypically similar ALL blasts have heterogeneous proliferative responses to the PKC and calcium modulators PDBu and ionomycin, as well as to rIL-2. Cytotoxic responses are also different from those of normal PBL and bone marrow cells with respect to kinetics and responsiveness to inducing agents. Thus current morphologic and phenotypic classifications of ALL may not adequately reflect the heterogeneity of this disorder as described here. |
