Quantitation of resistance to cytosine arabinoside by myeloid leukemic cells expressing bcl-2.
The presence of bcl-2 in myeloid leukemias has been associated with a decrease in therapy-induced apoptosis, reduced patient survival and in vitro autonomous growth of leukemic cells. The present study focuses on the quantitation of resistance to increasing doses of 1-beta-d-arabinofuranosylcytosine (Ara-C) by using hematological tumors expressing different levels of bcl-2. Scanning densitometry of Western blots demonstrated that the myeloid U-937 cells express low levels of bcl-2 (RD = 0.008), whereas the follicular lymphoma RL-7 expressed very high levels (RD = 3.084). Colony formation was also examined following incubation with Ara-C and RL-7 cells demonstrated a higher clonogenic survival (LD50 = 0.5 microns) when compared with U-937 cells (LD50 = 0.005 microM). Similarly, the level of bcl-2 expression in each cell line was also related to apoptosis with U-937 cells demonstrating increased DNA fragmentation when compared with RL-7 cells. To further evaluate the effect of upregulated bcl-2 on Ara-C treatment, U-937 cells were transfected with a retroviral vector carrying the murine bcl-2 or vector alone. Upregulation of bcl-2 by myeloid leukemic cells increased the resistance by 3 logs to Ara-C when comparing LD50 values from clonogenic assays, and decreased apoptosis by at least 3 logs when measuring dUTP positive cells by flow cytometry.
Guedez
L
L
Department of Medicine, University of Florida, Gainesville 32610, USA.
Suresh
A
A
Tung
F
F
Zucali
J
J
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology*; D053938:DNA Fragmentation; D018076:DNA, Complementary / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007951:Leukemia, Myeloid / Q000235:genetics / Q000473:pathology*; D008224:Lymphoma, Follicular / Q000235:genetics / Q000473:pathology*; D016403:Lymphoma, Large B-Cell, Diffuse / Q000235:genetics / Q000473:pathology*; D051379:Mice; D009363:Neoplasm Proteins / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics; D014411:Neoplastic Stem Cells / Q000187:drug effects*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000964:Antimetabolites, Antineoplastic; D018076:DNA, Complementary; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D003561:Cytarabine