5-Aza-2'-deoxycytidine suppresses human renal carcinoma cell growth in a xenograft model via up-regulation of the connexin 32 gene.
OBJECTIVE
The connexin (Cx) 32 gene, a member of the gap junction gene family, acts as a tumour suppressor gene in human renal cell carcinoma (RCC) and is down-regulated by the hypermethylation of CpG islands in a promoter region of the Cx gene. The current study investigated whether the restoration of Cx32 silenced by hypermethylation in RCC by a DNA demethylating agent could be an effective treatment against RCC.


METHODS
Using nude mice bearing Caki-1 cells (a human metastatic RCC cell line), the effects of 5-aza-2'-deoxycytidine (5-aza-CdR), a DNA demethylase inhibitor, on Cx32 mRNA expression and tumour growth were examined by RT-PCR, and by measuring tumour weight and volume. Cx32 expression in Caki-1 tumours was inhibited by Cx32 short interfering (si) RNA, and the effect of siRNA on 5-aza-CdR-dependent suppression of tumour growth in nude mice was evaluated.


RESULTS
5-aza-CdR treatment inhibited the growth of Caki-1 cells in nude mice by 70% and increased 7-fold the level of Cx32 mRNA. The intratumour injection of Cx32 siRNA almost totally inhibited the expression of Cx32 mRNA and significantly reduced the suppression of tumour growth in 5-aza-CdR-treated nude mice.


CONCLUSIONS
5-aza-CdR suppressed the growth of Caki-1 tumours in a xenograft model, by restoring Cx32 expression. This finding suggests that treatment with 5-aza-CdR could be a new effective therapy against human metastatic RCC and that Cx32 could be a potential target for the treatment of RCC.
Hagiwara
H
H
Project for Complementary Factors, National Institute of Health and Nutrition, Shinjuku, Tokyo, Japan.
Sato
H
H
Ohde
Y
Y
Takano
Y
Y
Seki
T
T
Ariga
T
T
Hokaiwado
N
N
Asamoto
M
M
Shirai
T
T
Nagashima
Y
Y
Yano
T
T
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002292:Carcinoma, Renal Cell / Q000188:drug therapy* / Q000235:genetics; D045744:Cell Line, Tumor; D017630:Connexins / Q000187:drug effects* / Q000235:genetics; D000077209:Decitabine; D005260:Female; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays; D000097002:Gap Junction beta-1 Protein
D000964:Antimetabolites, Antineoplastic; D001374:Azacitidine; D017630:Connexins; D000077209:Decitabine; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000097002:Gap Junction beta-1 Protein