title: Expression of the MDR1 gene and P-glycoprotein in canine mast cell tumor cell lines.
abstract: 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.
authors.affiliation: Department of Veterinary Surgery, Yamaguchi University, Yoshida, Japan.
authors.forename: Munekazu
authors.initials: M
authors.lastname: Nakaichi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Takeshita
authors.forename: Masaru
authors.initials: M
authors.lastname: Okuda
authors.forename: Yuya
authors.initials: Y
authors.lastname: Nakamoto
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Itamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Une
authors.forename: Nobuo
authors.initials: N
authors.lastname: Sasaki
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kadosawa
authors.forename: Tomoko
authors.initials: T
authors.lastname: Takahashi
authors.forename: Yasuho
authors.initials: Y
authors.lastname: Taura
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western / Q000662:veterinary; D045744:Cell Line, Tumor; D004283:Dog Diseases / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D004285:Dogs; D005434:Flow Cytometry / Q000662:veterinary; D005456:Fluorescent Dyes / Q000737:chemistry; D015870:Gene Expression; D019450:Genes, MDR; D034801:Mastocytoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D020112:Rhodamine 123 / Q000737:chemistry; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D005456:Fluorescent Dyes; D020112:Rhodamine 123; D014700:Verapamil