Expression of the MDR1 gene and P-glycoprotein in canine mast cell tumor cell lines

Munekazu Nakaichi, Yoko Takeshita, Masaru Okuda, Yuya Nakamoto, Kazuhito Itamoto, U. N.E. Satoshi, Nobuo Sasaki, Tsuyoshi Kadosawa, Tomoko Takahashi, Yasuho Taura

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


Cellular drug resistance to antineoplastic drugs is often due to the presence of a drug efflux pump that reduces intracellular drug accumulation and chemosensitivity. P-glycoprotein (P-gp), which is encoded by the MDR1 gene, is considered to function as an ATP-driven membrane drug efflux pump and appears to play an important role in tumor cell resistance. In the present report, we assessed the expression of MDR1 by RT-PCR in three canine mast cell tumor cell lines, TiMC, CoMS and LuMC, originating from a cutaneous tumor, an oral-mucosal tumor and a gastrointestinal tumor, respectively. P-gp expression was also examined by Western blot analysis, while the functional activity of P-gp was assessed by flowcytometric analysis of intracellular rhodamine-123 (Rhd-123) uptake. The results revealed that MDR1 gene and P-gp were both expressed in CoMS and LuMC cells, whereas neither was present in TiMC cells. In CoMS and LuMC cells, intracellular uptake of Rhd-123 increased in the presence of verapamil, a functional modulator of P-gp. In contrast, TiMC cells did not show any changes in the intracellular accumulation of Rhd-123 after the verapamil addition. These findings suggest that the expressions of MDR1 gene and P-gp probably contribute to cellular drug resistance in canine mast cell tumors.

Original languageEnglish
Pages (from-to)111-115
Number of pages5
JournalJournal of Veterinary Medical Science
Issue number2
Publication statusPublished - Feb 2007


  • Canine mast cell tumor
  • Cellular chemosensitivity
  • MDR1
  • P-glycoprotein


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