pIXY321 protects against Ara-C or taxol-induced apoptosis and loss of clonogenic survival of normal human bone marrow progenitor cells.
By suppressing apoptosis, hemopoietic growth factors (HGFs) promote the survival of CD34+, HLA-DR+ marrow cells that are enriched for hemopoietic progenitor cells (HPC). In the present studies, we have examined the effects of pIXY321, a genetically engineered fusion protein of GM-CSF and IL-3 (GM-CSF/IL-3), on high-dose Ara-C (HIDAC) and taxol-induced apoptosis and survival of a multilineage HPC, the CFU-GEMM. Exposure to 1.0 mumol/l taxol for 24 h or HIDAC > or = 10 mumol/l for 4 h induced internucleosomal DNA fragmentation and the morphologic features of apoptosis in CD34+, HLA-DR+ cells. These treatments were associated with > or = 50% inhibition of the assayable CFU-GEMM colony numbers. Incubation in serum-free medium (SFM) alone for 24 h also induced apoptosis of CD34+, HLA-DR+ cells, which was associated with reduced intracellular levels of the bcl-2 gene product p26BCL-2. Co-treatment with pIXY321 (10 ng/ml) inhibited apoptosis of CD34+, HLA-DR+ cells incubated in SFM, without significantly increasing the intracellular p26BCL-2 levels. Furthermore, co-treatment with pIXY321 significantly reduced taxol- and Ara-C-induced apoptosis and promoted the survival of CFU-GEMM (P < 0.05). Taxol and Ara-C mediated apoptosis of CD34+, HLA-DR+ cells, and its inhibition by pIXY321, was not accompanied by any significant alteration in the intracellular p26BCL-2 levels. By demonstrating that co-treatment with pIXY321 confers significant protection against apoptosis of CD34+, HLA-DR+ cells as well as promotes survival of normal HPC exposed to clinically relevant schedules and concentrations of taxol of Ara-C, these results support the design of chemotherapy regimens incorporating pIXY321 plus taxol and/or high-dose Ara-C for solid tumors and/or acute leukemias. It is hoped that the use of such a cytokine might maintain normal HPC numbers following chemotherapy, therefore avoiding prolonged suppression.
D018952:Antigens, CD34 / Q000032:analysis; D017209:Apoptosis / Q000187:drug effects*; D001854:Bone Marrow Cells; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003561:Cytarabine / Q000037:antagonists & inhibitors*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006684:HLA-DR Antigens / Q000032:analysis; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology*; D017239:Paclitaxel / Q000037:antagonists & inhibitors*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins / Q000494:pharmacology*
D018952:Antigens, CD34; D006684:HLA-DR Antigens; D007377:Interleukin-3; C078524:PIXY321 fusion protein, recombinant; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D003561:Cytarabine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D017239:Paclitaxel