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Loss of DNA mismatch repair in acquired resistance to cisplatin
S Aebi1, B Kurdi-Haidar, R Gordon
1Department of Medicine and the Cancer Center, University of California at San Diego, La Jolla 92093-0812, USA.
Abstract:
Selection of cells for resistance to cisplatin, a well-recognized mutagen, could result in mutations in genes involved in DNA mismatch repair and thereby to resistance to DNA-alkylating agents. Parental cells of the human ovarian adenocarcinoma cell line 2008 expressed hMLH1 when analyzed with immunoblot. One subline selected for resistance to cisplatin (2008/A) expressed no hMLH1, whereas another (2008/C13*5.25) expressed parental levels. Microsatellite instability was readily demonstrated in 2008/A cells but not in 2008 and in 2008/C13*5.25 cells. In addition, the 2008/A cells were 2-fold resistant to methyl-nitro-nitrosoguanidine and had a 65-fold elevated mutation rate at the HPRT locus as compared to 2008 cells, both of which are consistent with the loss of DNA mismatch repair in these cells. To determine whether the loss of DNA mismatch repair itself contributes to cisplatin resistance, studies were carried out in isogenic pairs of cell lines proficient or defective in this function. HCT116, a human colon cancer cell line deficient in hMLH1 function, was 2-fold resistant to cisplatin when compared to a subline complemented with chromosome 3 and expressing hMLH1. Similarly, the human endometrial cancer cell line HEC59, which expresses no hMSH2, was 2-fold resistant to cisplatin when compared to a subline complemented with chromosome 2 that expresses hMSH2. Therefore, the selection of cells for resistance to cisplatin can result in the loss of DNA mismatch repair, and loss of DNA mismatch repair in turn contributes to resistance to cisplatin.
Insights
Developing cisplatin resistance in cancer cells can lead to defects in DNA mismatch repair. This loss of DNA repair function contributes to resistance against DNA-alkylating agents like cisplatin.
Area of Science:
- Molecular Biology
- Cancer Research
- Genetics
Background:
- Cisplatin is a widely used chemotherapy drug and mutagen.
- DNA mismatch repair (MMR) corrects errors during DNA replication.
- Defects in MMR are linked to cancer development and drug resistance.
Purpose of the Study:
- To investigate the relationship between cisplatin resistance and DNA mismatch repair.
- To determine if loss of MMR function contributes to cisplatin resistance.
Main Methods:
- Utilized human ovarian adenocarcinoma cell line (2008) and its cisplatin-resistant sublines.
- Analyzed expression of MMR proteins (hMLH1, hMSH2) using immunoblotting.
- Assessed microsatellite instability and mutation rates at the HPRT locus.
- Compared cisplatin resistance in isogenic cancer cell lines with proficient versus deficient MMR.
Main Results:
- Cisplatin-resistant cells (2008/A) showed loss of hMLH1 expression and microsatellite instability.
- These cells exhibited increased resistance to methyl-nitro-nitrosoguanidine and elevated mutation rates.
- Isogenic cell lines deficient in hMLH1 (HCT116) or hMSH2 (HEC59) demonstrated 2-fold resistance to cisplatin.
Conclusions:
- Selection for cisplatin resistance can induce loss of DNA mismatch repair function.
- Loss of DNA mismatch repair contributes to acquired resistance to cisplatin.
- This highlights a mechanism of chemotherapy resistance in cancer cells.