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A lack of detectable modification of topoisomerase II activity in a series of human tumor cell lines expressing only low levels of etoposide resistance
Author(s) -
Hill Bridget T.,
Whelan Richard D. H.,
Hosking Louise K.,
Shellard Sharon A.,
Hinds Michael D.,
Mayes Janice,
Zwelling Leonard A.
Publication year - 1991
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910470619
Subject(s) - amsacrine , etoposide , topoisomerase , in vitro , biology , cell culture , microbiology and biotechnology , biochemistry , genetics , chemotherapy
Etoposide (VP‐16) resistance is expressed following in vitro exposure of HN‐1 and MCF‐7 human tumor cells to the drug itself or to fractionated × irradiation. VP‐16‐selected sublines prove cross‐resistant to Adriamycin, amsacrine and actinomycin D, whilst X‐ray‐pretreated sublines show cross‐resistance to only actinomycin D. These differential responses, in the HN‐1 series, are not associated with significant differences in amounts of immunoreactive topoisomerase (topo) II, altered topo‐II catalytic activity of nuclear extracts or changes in susceptibility of the topo II to VP‐16‐ or amsacrine‐induced DNA‐protein cross‐link formation. Therefore significant modifications in topo II appear not to be implicated in VP‐16 resistance in these HN‐1 sublines.