Up-regulation of connexin 32 gene by 5-aza-2′-deoxycytidine enhances vinblastine-induced cytotoxicity in human renal carcinoma cells via the activation of JNK signalling

Y. Takano, Hiroki Iwata, Y. Yano, M. Miyazawa, N. Virgona, H. Sato, K. Ueno, T. Yano

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Enforced expression of connexin (Cx) 32 gene, a member of gap junction gene family and a tumor suppressor gene in human renal cell carcinoma (RCC), enhanced vinblastine (VBL)-induced cytotoxicity on RCC cells, due to the suppression of multidrug resistance 1 (MDR1) gene product, P-glycoprotein (P-gp). Also, Cx32 gene in RCC is silenced by hypermethylation of CpG islands in a promoter region of the Cx gene. In this study, we investigated if a DNA demethylating agent, 5-aza-2'-deoxycytidine (5-Aza) could enhance susceptibility of RCC cells (Caki-1) to VBL. We found that 5-Aza treatment up-regulated Cx32 in Caki-1 cells, and the induction of the Cx led to the suppression of P-gp through inhibition of Src and subsequent activation of c-Jun NH2-terminal kinase (JNK). Moreover, increased transcription activity of c-Jun by the JNK activation contributed to the down-regulation of MDR1, thus indicating a central role of JNK signalling to suppress P-gp level in 5-Aza-treated Caki-1 cells. Chemical sensitivity to VBL in Caki-1 cells was increased by 5-Aza pre-treatment, and this effect was abrogated by short interfering RNA (siRNA)-mediated knockdown of Cx32. Furthermore, co-treatment of 5-Aza or a P-gp inhibitor with VBL drastically enhanced JNK activation comparing to only VBL treatment in Caki-1 cells. These results suggest that the restoration of Cx32 by 5-Aza pre-treatment improves chemical tolerance on VBL in Caki-1 cells and that the JNK activation is a key factor to induce the effect.

Original languageEnglish
Pages (from-to)463-470
Number of pages8
JournalBiochemical Pharmacology
Volume80
Issue number4
DOIs
Publication statusPublished - 2010 Aug
Externally publishedYes

Fingerprint

decitabine
Vinblastine
JNK Mitogen-Activated Protein Kinases
Cytotoxicity
Renal Cell Carcinoma
Up-Regulation
Genes
Chemical activation
Cells
P-Glycoprotein
Connexins
CpG Islands
MDR Genes
Transcription
Genetic Promoter Regions
Gap Junctions
Multiple Drug Resistance
Small Interfering RNA
Restoration
connexin 32

Keywords

  • 5-Aza-2′-deoxycytidine
  • Caki-1 cells
  • Connexin32
  • JNK
  • Renal cell carcinoma

ASJC Scopus subject areas

  • Pharmacology
  • Biochemistry

Cite this

Up-regulation of connexin 32 gene by 5-aza-2′-deoxycytidine enhances vinblastine-induced cytotoxicity in human renal carcinoma cells via the activation of JNK signalling. / Takano, Y.; Iwata, Hiroki; Yano, Y.; Miyazawa, M.; Virgona, N.; Sato, H.; Ueno, K.; Yano, T.

In: Biochemical Pharmacology, Vol. 80, No. 4, 08.2010, p. 463-470.

Research output: Contribution to journalArticle

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abstract = "Enforced expression of connexin (Cx) 32 gene, a member of gap junction gene family and a tumor suppressor gene in human renal cell carcinoma (RCC), enhanced vinblastine (VBL)-induced cytotoxicity on RCC cells, due to the suppression of multidrug resistance 1 (MDR1) gene product, P-glycoprotein (P-gp). Also, Cx32 gene in RCC is silenced by hypermethylation of CpG islands in a promoter region of the Cx gene. In this study, we investigated if a DNA demethylating agent, 5-aza-2'-deoxycytidine (5-Aza) could enhance susceptibility of RCC cells (Caki-1) to VBL. We found that 5-Aza treatment up-regulated Cx32 in Caki-1 cells, and the induction of the Cx led to the suppression of P-gp through inhibition of Src and subsequent activation of c-Jun NH2-terminal kinase (JNK). Moreover, increased transcription activity of c-Jun by the JNK activation contributed to the down-regulation of MDR1, thus indicating a central role of JNK signalling to suppress P-gp level in 5-Aza-treated Caki-1 cells. Chemical sensitivity to VBL in Caki-1 cells was increased by 5-Aza pre-treatment, and this effect was abrogated by short interfering RNA (siRNA)-mediated knockdown of Cx32. Furthermore, co-treatment of 5-Aza or a P-gp inhibitor with VBL drastically enhanced JNK activation comparing to only VBL treatment in Caki-1 cells. These results suggest that the restoration of Cx32 by 5-Aza pre-treatment improves chemical tolerance on VBL in Caki-1 cells and that the JNK activation is a key factor to induce the effect.",
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AU - Yano, Y.

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AU - Ueno, K.

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