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J Korean Rheum Assoc. 2003 Mar;10(1):53-60. Korean. Original Article.
Kim SG , Suh HS , Choe JY , Lee JW , Suh JS , Kim TY .
Department of Laboratory Medicine School of Medicine, Catholic University of Daegu, Korea.
Department of Internal Medicine School of Medicine, Catholic University of Daegu, Korea.
Biochemistry School of Medicine, Catholic University of Daegu, Korea.
Department of Laboratory Medicine, Kyung-pook National University School of Medicine, Daegu, Korea.
The Hospital for Rheumatic Diseases Department of Laboratory Medicine, Hanyang University College of Medicine, Seoul, Korea.

OBJECTIVE: A number of disease-modifying anti-rheumatic drugs (DMARDs) have been shown to be more effective than placebo in the management of rheumatoid arthritis (RA). However, most course of DMARDs, except methotrexate, are discontinued after 2 or 3 years, because of toxicity, lack of efficacy or escape from control. The multi-drug resistance (MDR) is a phenomenon in which cells develop cross-resistance to many agents such as anthracyclin, vinca alkaloids and colchicine. In our hypothesis, MDR phenomenon could be implicated in acquired resistance to DMARDs in RA. We have established a mdr1 cell line and tested whether DMARDs are substrate for P-glycoprotein (P-gp). METHODS: The mdr1-cDNA was cloned into retroviral vector, and the recombinant retroviral vector was transfected into PA317 cells. The target cells, NIH3T3, were infected with recombinant retroviruses. A colony most resistant to vinblastin was selected for the following experiments; expression of mdr1 gene in NIH3T3 cells was confirmed by RT-PCR, and biological function of mdr1 gene product, P-gp, was tested using Rhodamine-123 (Rh123) efflux assay. Resistance of the target cells expression P-gp which can survive against hydroxychloroquine (HCQ) and methotrxate (MTX) were measured by MTT assay. RESULTS: RT-PCR for mdr1 gene showed successful transfer of the gene into the NIH3T3 cells. Rh123 assay revealed expression of P-gp on the selected cells as follows; Rh123 efflux activity of uninfected NIH3T3 cells was 6%, that of PLXSN was 0.2%, and that of selected cells was 44%. The 50% proliferation inhibitory capacity of the selected cells were twice for HCQ but there was no difference of that for MTX. CONCLUSION: We established a mdr1 cell line and using the cell line, HCQ was a substrate of MDR, but MTX was not related to MDR.

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