VP-16-mediated cytotoxicity is modulated by interleukin-3 in a growth factor-dependent leukemic cell line.
A growth factor-dependent cell line (TF-1) was treated with interleukin-3 (IL-3) or medium in combination with variable doses of VP-16 to test whether the latter's cytotoxicity can be modulated by IL-3. The results demonstrated that an augmented cell death occurred with TF-1 cells when pre-incubated for 24 h with IL-3 followed by treatment with VP-16 (10 micrograms/ml) for 1 h. The increased cell death could not be ascribed to an increased number of apoptotic cells as measured with the acridine orange method. However, the IL-3 treatment coincided with an upregulation of DNA topoisomerase II alpha (Topo II alpha) at mRNA and protein level after 24 h, which was preceded by an upregulation of c-myc mRNA. In contrast, Topo II beta did not demonstrate an upregulation at mRNA level in response to IL-3 stimulation. In addition, it was shown that cells treated with IL-3 followed by VP-16 demonstrated a higher number of cleavable DNA complexes which was not due to an increased uptake of VP-16, since cellular concentrations of VP-16 in the presence of IL-3 or medium were 16.8 +/- 7.8 ng/10(6) cells and 19.8 +/- 7.8 ng/10(6) cells (mean +/- SD, n = 3), respectively. These data indicate that IL-3 pretreatment followed by VP-16 results in an increased cell death due to cytotoxicity which may be ascribed to an upregulation of Topo II alpha.
Vellenga
E
E
Department of Hematology and Medical Oncology, University Hospital, Groningen, The Netherlands.
Asschert
L
L
Withoff
S
S
van der Kolk
D
D
de Vries
E G
EG
D017209:Apoptosis / Q000187:drug effects; D015152:Blotting, Northern; D015153:Blotting, Western; D016923:Cell Death / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D005047:Etoposide / Q000378:metabolism / Q000494:pharmacology*; D016259:Genes, myc; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology / Q000502:physiology*; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism / Q000473:pathology*; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism / Q000473:pathology*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D015854:Up-Regulation
D007377:Interleukin-3; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D005047:Etoposide; D004250:DNA Topoisomerases, Type II