title: Connexin 32 potentiates vinblastine-induced cytotoxicity in renal cell carcinoma cells.
abstract: We have reported that connexin (Cx) 32 gene, a member of gap junction protein family, acts as a tumor suppressor gene in human renal cell carcinoma (RCC). Of solid tumors, RCC is one of the most chemoresistant cancers, and there is no effective cancer chemotherapy against RCC at present. In this study, we examined if the combination of Cx32-dependent tumor-suppressive effect and vinblastine (VBL), a chemotherapeutic agent which has been utilized for clinical RCC treatment, could be effective in enhancing the sensitivity of RCC to VBL treatment. Cx32 expression in a human metastatic RCC cell (Caki-1 cell) significantly enhanced in vitro and in vivo VBL-induced cytotoxicity on the cell. Cx32 expression in the RCC cells potentiated VBL-induced apoptosis compared to the Cx32-negative RCC cells in vitro as well as in vivo. The enhancing apoptosis in the RCC cells by Cx32 mainly depended on the decrease of P-glycoprotein (P-gp), a multidrug resistance gene-1 (MDR-1) product responsible for reduction of VBL accumulation into the cells. We also observed that silencing of Cx32 by short interfering RNA (siRNA) treatment elevated the level of P-gp in Caki-1 cells and that inhibition of P-gp function enhanced VBL-induced apoptosis in the RCC cells. These results suggest that Cx32 is effective to enhance VBL-induced cytotoxicity in Caki-1 cells via the reduction of P-gp. Overall, it seems that the combination of Cx32-dependent tumor-suppressive effect and VBL is promising as a new cancer therapy against RCC.
authors.affiliation: Project for Complementary Factors, National Institute of Health and Nutrition, Tokyo, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sato
authors.forename: Hironobu
authors.initials: H
authors.lastname: Senba
authors.forename: Nantiga
authors.initials: N
authors.lastname: Virgona
authors.forename: Keiko
authors.initials: K
authors.lastname: Fukumoto
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ishida
authors.forename: Hiromi
authors.initials: H
authors.lastname: Hagiwara
authors.forename: Etsuko
authors.initials: E
authors.lastname: Negishi
authors.forename: Koichi
authors.initials: K
authors.lastname: Ueno
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamasaki
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yano
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects*; D002292:Carcinoma, Renal Cell / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003131:Combined Modality Therapy; D017630:Connexins / Q000502:physiology*; D045304:Cytochromes c / Q000378:metabolism; D018432:Drug Resistance, Multiple; D006801:Humans; D007680:Kidney Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008928:Mitochondria / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000633:toxicity*; D000097002:Gap Junction beta-1 Protein
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D017630:Connexins; D045304:Cytochromes c; D014747:Vinblastine; D000097002:Gap Junction beta-1 Protein