Phorbol ester-mediated inhibition of growth and regulation of proto-oncogene expression in the human T cell leukemia line JURKAT.
The expression and function of several proto-oncogenes were examined in a human acute T cell leukemia line, JURKAT, during phorbol ester-induced terminal differentiation. Treating JURKAT cells with the phorbol ester tetradecanoyl phorbol acetate (TPA) inhibited their proliferation and induced expression of the gene for the interleukin 2 receptor alpha chain (IL2R-alpha), consistent with previous reports. In unstimulated proliferating JURKAT cells, high levels of C-MYC, N-RAS, and BCL2 mRNAs were found that diminished rapidly following TPA-induced cessation of growth. In contrast, accumulation of mRNAs for the C-FOS, C-JUN, and EGR-1 genes increased markedly in TPA-treated cells and preceded the induction of IL2R-alpha mRNA. Expression of C-MYB, C-RAF-1, C-LCK, C-FYN, and C-FGR proto-oncogenes was relatively unchanged. To explore directly the function of two of these protooncogenes in regulating the growth of JURKAT T cells, we stably transferred C-MYC and BCL2 expression plasmids into these cells. Despite sustained expression of C-MYC, BCL2, or the combination of these protooncogenes, TPA continued to inhibit JURKAT cell growth and to induce IL2R expression. Thus, although C-MYC and BCL2 proto-oncogene expression correlated with proliferation in TPA-treated JURKAT cells, continuous over-expression of even the combination of these oncogenes was insufficient for abrogating the effects of TPA in these leukemic T cells. Because human lymphoid malignancies frequently contain chromosomal translocations that deregulate the expression of C-MYC and BCL2, our findings could have relevance for attempts to induce terminal differentiation of leukemic cells by in vitro exposure of patients' bone marrow cells to phorbol esters.
Makover
D
D
Department of Internal Medicine, University of Pennsylvania, Philadelphia 19104.
Cuddy
M
M
Yum
S
S
Bradley
K
K
Alpers
J
J
Sukhatme
V
V
Reed
J C
JC
D015152:Blotting, Northern; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D015458:Leukemia, T-Cell / Q000235:genetics* / Q000473:pathology; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000235:genetics; D015375:Receptors, Interleukin-2 / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014162:Transfection; D014407:Tumor Cells, Cultured
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D015375:Receptors, Interleukin-2; D013755:Tetradecanoylphorbol Acetate