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Enrichment for DNA mismatch repair‐deficient cells during treatment with cisplatin
Author(s) -
Fink Daniel,
Nebel Sibylle,
Norris Paula S.,
Baergen Rebecca N.,
Wilczynski Sharon P.,
Costa Michael J.,
Haas Martin,
Cannistra Stephen A.,
Howell Stephen B.
Publication year - 1998
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(19980831)77:5<741::aid-ijc13>3.0.co;2-4
Subject(s) - cisplatin , clonogenic assay , clone (java method) , carboplatin , biology , chinese hamster ovary cell , dna repair , in vivo , microbiology and biotechnology , cancer research , paclitaxel , cancer , chemotherapy , cell culture , dna , genetics
In addition to playing a role in tumorigenesis, loss of DNA mismatch repair results in low‐level intrinsic resistance to cisplatin and carboplatin. We used a mismatch repair‐deficient (clone B) and ‐proficient (clone B/rev) pair of Chinese hamster ovary sublines to determine the ability of cisplatin to enrich for repair‐deficient cells during growth in vitro and in vivo . Clone B cells were 1.8‐fold resistant to cisplatin as measured by a clonogenic assay. These cells were molecularly engineered to express constitutively the green fluorescent protein, and changes in the fraction of these repair‐deficient cells were monitored by flow cytometric analysis. A single 1‐hr exposure to cisplatin at an IC 50 concentration enriched populations initially containing either 5 or 10% clone B cells by 81 and 75%, respectively, when measured at 5 days. Enrichment increased as a function of drug concentration to 158 and 169%, respectively, following an IC 90 exposure. When grown as a xenograft, a single LD 10 dose of cisplatin enriched the tumors by 48% from 4.6 to 6.8% repair‐deficient cells ( p = 0.04). To determine whether similar enrichment occurs during the treatment of human ovarian cancer patients, paired tumor samples were obtained from 38 patients before and after treatment with a minimum of 3 cycles of platinum drug‐based primary chemotherapy and analyzed immunohistochemically for changes in the fraction of tumor cells expressing hMHL1. Following treatment there was a reduction in hMLH1 staining in 66% of the cases ( p = 0.0005). Our results demonstrate that, despite the fact that loss of mismatch repair yields only modest levels of cisplatin resistance, even a single exposure to cisplatin produces quite a marked enrichment for repair‐deficient cells in vitro and in vivo . Our results are consistent with the concept that treatment with cisplatin or carboplatin selects for pre‐existing mismatch repair‐deficient cells, and that this contributes to the frequent development of clinical resistance. Int. J. Cancer 77:741–746, 1998. © 1998 Wiley‐Liss, Inc.