Co-amplification of dhfr and a homologue of hmsh3 in a Chinese hamster methotrexate-resistant cell line correlates with resistance to a range of chemotherapeutic drugs

Citation
B. Pandit et al., Co-amplification of dhfr and a homologue of hmsh3 in a Chinese hamster methotrexate-resistant cell line correlates with resistance to a range of chemotherapeutic drugs, CANC CHEMOT, 48(4), 2001, pp. 312-318
Citations number
36
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Oncology,"Onconogenesis & Cancer Research
Journal title
CANCER CHEMOTHERAPY AND PHARMACOLOGY
ISSN journal
0344-5704 → ACNP
Volume
48
Issue
4
Year of publication
2001
Pages
312 - 318
Database
ISI
SICI code
0344-5704(200110)48:4<312:CODAAH>2.0.ZU;2-A
Abstract
Purpose: To characterize a methotrexate-resistant Chinese hamster cell line . designated as M5, which had previously been shown to be resistant to gamm a radiation, at the cellular and molecular levels. Methods: Sensitivity tow ards a number of chemotherapeutic drugs was determined by colony-forming ab ility and compared with that of parental V79 cells. Expression of the hamst er homologue of the human mismatch repair gene hmshO was also determined by RT-PCR. Results: Induced killing by chemotherapeutic agents cis-diamminedi chloroplatinum II (cisplatin). the antimetabolite 6-thioguanine (6-TG). cam ptothecin, a topoisomerase I inhibitor, and 4-(9-acridinyl-amino)methanesul fon-m-anisidide (mAMSA). an inhibitor of topoisomerase II. was less in M5 c ells than in the parental V79 cells. The IC50 values, defined as the concen tration of the drug that reduced the survival to 50% that of the untreated control. in V79 cells for mAMSA and camptothecin treatment were 0.35 +/- 0. 02 mug/ml and 84.3 +/- 16.0 ng/ml, respectively. For M5 cells, equivalent v alues were 0.52 mu 0.10 etag/ml and 186 +/- 40.8 ng/ml. Treatment with 30 m uM cisplatin reduced the survival of V79 cells to 0.09 +/- 0.07. whereas th e same treatment reduced the survival of M5 cells to 0.67 +/- 0.16. Treatme nt of M5 cells with 6-TG did not induce appreciable killing up to the conce ntrations studied. However, for V79 cells. 6-TG was very toxic. We further observed that the dihydrofolate reductase (dhfr) gene as well as the hamste r homologue of the human mismatch repair gene hmsh3 was amplified in the me thotrexate-resistant M5 cells. Conclusion: Resistance to this group of chem otherapeutic drugs observed in M5 cells could be due to the amplification o f the hamster homologue of hMSH3, which in turn possibly sequesters all the hMSH2 making M5 cells functionally deficient in the mismatch repair system .