Human colon cancer cells surviving high doses of cisplatin or oxaliplatin in vitro are not defective in DNA mismatch repair proteins.
OBJECTIVE
Alterations in the DNA mismatch repair (MMR) proteins have been associated with an increased resistance of many cancer cell lines to cisplatin. The aim of this work was to investigate whether defects in DNA MMR proteins are involved in the survival of human colorectal cancer cells in the presence of high concentrations of cisplatin and oxaliplatin, a diaminocyclohexane (DACH) platinum compound whose adducts are not recognized by the MMR system.


METHODS
Six unselected human colon cancer cell lines (HT29, HCT15, HCT116, Caco2, SW480 and SW620) were treated with a single 3-h exposure to cisplatin or oxaliplatin at suprapharmacological concentrations, ranging from 50 to 200 microg/ml. The microsatellite stability and the expression of MMR proteins in the parental cell lines and in the drug-selected subpopulations were studied.


RESULTS
Most cells underwent apoptosis in the days following the cisplatin or oxaliplatin treatment, but some colonies expanded 3 to 4 weeks after, suggesting the presence of innately resistant cells in the six parental cell lines. Microsatellite instability (MIN), which reflects genetic defects in the DNA MMR system, was detected only in the HCT116 parental cell line and its drug-selected counterparts, due to a known mutation in the hMLH1 gene. No acquired MIN was observed in the other cisplatin-selected sublines derived from the HT29, HCT15, Caco2, SW480 or SW620 parental cells. In the same way, Western blot analysis showed that expression of the DNA MMR proteins hMLH1, hPMS1, hPMS2, hMSH2 and hMSH6 did not differ between the parental and the drug-surviving cells.


CONCLUSIONS
These results indicate that high-level resistance of human colon cancer cells to high doses of cisplatin and oxaliplatin does not seem to be related to acquired defects in the DNA MMR proteins.
Sergent
Catherine
C
Unité INSERM 517, Faculté de Médecine et de Pharmacie, 7 bd Jeanne d'Arc, BP 87900, 21079 Dijon, France. csergent@u-bourgogne.fr
Franco
Noreli
N
Chapusot
Caroline
C
Lizard-Nacol
Sarab
S
Isambert
Nicolas
N
Correia
Maria
M
Chauffert
Bruno
B
D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D020137:Base Pair Mismatch / Q000235:genetics*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D018736:DNA Adducts / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D004260:DNA Repair / Q000235:genetics; D045643:DNA Repair Enzymes; D004273:DNA, Neoplasm / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D005656:Fungal Proteins / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D018895:Microsatellite Repeats; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000378:metabolism*; D009687:Nuclear Proteins; D009944:Organoplatinum Compounds / Q000494:pharmacology*; D000077150:Oxaliplatin; D016133:Polymerase Chain Reaction; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D002352:Carrier Proteins; D018736:DNA Adducts; D017931:DNA Primers; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C501486:MLH1 protein, human; C098790:MSH6 protein, S cerevisiae; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D009944:Organoplatinum Compounds; C088996:PMS1 protein, human; D011518:Proto-Oncogene Proteins; D029701:Saccharomyces cerevisiae Proteins; D000077150:Oxaliplatin; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; C497172:MSH2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes; D002945:Cisplatin