Premium
Mechanism of increased sensitivity to etoposide in a mitomycin C‐resisitant human bladder cancer cell line
Author(s) -
Xia Hong,
Bleicher Richard J.,
Gupta Vicram,
Zaren Howard A.,
Singh Shivendra V.
Publication year - 1997
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/(sici)1097-0215(19970304)70:5<606::aid-ijc19>3.0.co;2-a
Subject(s) - mitomycin c , etoposide , medicine , cell culture , pharmacology , biology , surgery , chemotherapy , genetics
The mechanism of increased sensitivity to etoposide (VP‐16) in a human bladder cancer cell line (J82/MMC‐2), which is >9‐fold more resistant to mitomycin C (MMC) compared with parental cells (J82/WT), was investigated. Colony formation assays, following 1 hr drug exposure, revealed that about a 2.2‐fold higher concentration of VP‐16 was required to kill 50% of the J82/WT cell line compared with J82/MMC‐2. The MTT assays, following continuous drug exposure, also showed that the J82/MMC‐2 cell line was significantly more sensitive to VP‐16 compared with J82/WT. Accumulation of VP‐16 was significantly higher in the J82/MMC‐2 cell line compared with J82/WT at every drug concentration tested. Likewise, intracellular VP‐16 retention was significantly higher in the J82/MMC‐2 cell line compared with J82/WT when drug uptake was measured as a function of varying incubation time and at a fixed VP‐16 concentration. The efflux of VP‐16 from the J82/MMC‐2 cell line was equivalent to that from J82/WT. In agreement with the results of drug uptake studies, the levels of VP‐16‐induced protein‐DNA complexes were markedly higher in the J82/MMC‐2 cell line compared with J82/WT. The catalytic activity of topoisomerase II (topo II) in 0.35 M NaCl nuclear extract of J82/WT cells was equivalent to that of J82/MMC‐2. The levels of topo II mRNA were also comparable in these cells. Our results suggest that the mechanism responsible for the collateral sensitivity of the J82/MMC‐2 cell line to VP‐16 may be attributable to a relatively higher drug accumulation in this cell line compared with parental cells. Int. J. Cancer 70:612–618. © 1997 Wiley‐Liss Inc.