The inhibitory effect of connexin 32 gene on metastasis in renal cell carcinoma.
We have previously reported that connexin (Cx) 32 gene, a member of gap junctions, was specifically downregulated in human renal cell carcinoma (RCC) and it acts as a tumor suppressor against RCC. Because there is no standard therapy for advanced RCC, we investigated the anti-metastatic effect of Cx32 to seek a possibility of new RCC therapy. In this study, we used human metastatic RCC cell (Caki-1), and established Cx32-expressed cell clone (Caki-1T) or only mock-transfected cell clone (Caki-1W). For experimental production of metastases, the cells were injected into the lateral tail vein of SCID mice. Seventy days after inoculation, metastatic colonies were observed in Caki-1W inoculated group, though none of them were in Caki-1T inoculated group. The plasma VEGF concentration was significantly lower in Caki-1T group compared to Caki-1W group. To investigate where Cx32 effects on, we also tried in vitro analysis and found that the malignant phenotypes involving metastasis steps were significantly decreased in Caki-1T under hypoxia, a mimic condition of internal tumor environment. After hypoxia treatment, the protein level of HIF-2alpha, which plays main role for hypoxia adaptation, was observed to increase in Caki-1W, whereas no expression was observed in Caki-1T. We investigated the activation of Src, which is required for stabilization of HIF-2alpha, is suppressed in Caki-1T compared to Caki-1W. These results suggest that Cx32 inhibits hypoxia adaptation governed by HIF-2alpha, and this may help to reduce the metastasis of RCC cells.
Sato
Hiromi
H
Project for Complementary Factors, National Institute of Health and Nutrition, Shinjuku-ku, Tokyo, Japan.
Hagiwara
Hiromi
H
Senba
Hironobu
H
Fukumoto
Keiko
K
Nagashima
Yoji
Y
Yamasaki
Hiroshi
H
Ueno
Koichi
K
Yano
Tomohiro
T
D000818:Animals; D001483:Base Sequence; D002292:Carcinoma, Renal Cell / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D017630:Connexins / Q000502:physiology*; D017931:DNA Primers; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics / Q000473:pathology*; D008212:Lymphocyte Depletion; D051379:Mice; D016513:Mice, SCID; D009362:Neoplasm Metastasis; D017395:Plasminogen Activator Inhibitor 1 / Q000097:blood; D012333:RNA, Messenger / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A / Q000097:blood; D000097002:Gap Junction beta-1 Protein
D017630:Connexins; D017931:DNA Primers; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D000097002:Gap Junction beta-1 Protein