REDUCTION OF HEAT-INDUCED HAEMOTOXICITY IN A HYPERTHERMIC PURGING PROTOCOL OF MURINE ACUTE MYELOID LEUKEMIC STEM-CELLS BY ACSDKP

The tetrapeptide AcSDKP (Goralatide) is a cytokine with known inhibito ry effects on cell proliferation, Many purging agents used in autologo us bone marrow transplantation protocols, including hyperthermia, pref erentially kill cycling cells. A pretreatment with Goralatide offers a possibility to reduce the haemotoxicity in many purging settings. The impact of Goralatide on the hyperthermic purging protocol was investi gated in normal and myeloid leukaemic (SA8) murine cells. The median s urvival time after transplantation (i.e. leukaemia incidences) was use d as an in vivo parameter to determine the effects on leukaemic cells. The hyperthermic effect on normal and leukaemic cells was also invest igated in vitro using the cobblestone area-forming cell (CAFC) assay. A heat treatment of 90 min at 43 degrees C resulted in a 4-log depleti on of leukaemic stem cells. For normal progenitor cells (CFU-GM) a 2-l og cell kill was shown. The reduction in proliferative activity of the CFU-GM after an 8 h incubation with 10(-9) M Goralatide resulted in a decrease in the heat sensitivity of the progenitor subset to approxim ately a 1-log cell kill, The leukaemic precursor cells seem insensitiv e to Goralatide inhibition, implicating an increase in the therapeutic window of the hyperthermic purging protocol. Finally, simulated remis sion bone marrow (5% leukaemic blasts) was incubated with Goralatide f ollowed by a heat treatment of 90 min at 43 degrees C. Lethally irradi ated (10 Gy) mice transplanted with heat-treated remission bone marrow (10(6) normal bone marrow cells versus 5x10(4) leukaemic cells) died of aplasia while Goralatide-pretreated remission bone marrow could res cue the irradiated mice without revealing leukaemic engraftment, These findings confirmed the enhanced protection against hyperthermia of th e normal haemopoietic subsets by Goralatide and thus increased the suc cess of the hyperthermic purging protocol.