Enrichment for DNA mismatch repair-deficient cells during treatment with cisplatin.
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 IC50 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 IC90 exposure. When grown as a xenograft, a single LD10 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 preexisting mismatch repair-deficient cells, and that this contributes to the frequent development of clinical resistance.
Fink
D
D
Cancer Center, University of California at San Diego, La Jolla, USA. dfk@fhk.smtp.usz.ch
Nebel
S
S
Norris
P S
PS
Baergen
R N
RN
Wilczynski
S P
SP
Costa
M J
MJ
Haas
M
M
Cannistra
S A
SA
Howell
S B
SB
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D016466:CHO Cells; D002352:Carrier Proteins; D002470:Cell Survival / Q000187:drug effects; D002471:Cell Transformation, Neoplastic; D002945:Cisplatin / Q000494:pharmacology* / Q000627:therapeutic use*; D002999:Clone Cells; D006224:Cricetinae; D004260:DNA Repair; D004268:DNA-Binding Proteins; D005260:Female; D005818:Genetic Engineering; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000096:biosynthesis; D051379:Mice; D008819:Mice, Nude; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000032:analysis / Q000096:biosynthesis; D009687:Nuclear Proteins; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000096:biosynthesis; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014162:Transfection; D014183:Transplantation, Heterologous
D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; C501486:MLH1 protein, human; C501485:Mlh1 protein, mouse; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C497172:MSH2 protein, human; C497173:Msh2 protein, mouse; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D002945:Cisplatin