Connexin 32 down-regulates the fibrinolytic factors in metastatic renal cell carcinoma cells.
Fibrinolytic factors have an important role in tumor progression through the degradation of extracellular matrix. The increased levels of urokinase-type plasminogen activator (uPA), uPA-receptor (uPAR) and type-1 PA inhibitor (PAI-1) are reported in human renal cell carcinoma (RCC). Connexin (Cx) gene, a member of gap junction, is known to act as a tumor suppressor gene. We have reported that Cx32 improves malignant phenotypes of metastatic RCC cells via the inhibition of Src-dependent signaling. In this study, we examined the effect of expression of Cx32 gene on the production of uPA, uPAR and PAI-1, and on the induction of PAI-1 stimulated by hypoxia in a human metastatic RCC cell line, Caki-1 cells. Cx32 expression decreased both mRNA level and production of PAI-1, uPA and uPAR in Caki-1 cells. Cx32 also decreased hypoxia-inducible factor (HIF)-1alpha and HIF-2alpha mRNA level. PP1, a Src inhibitor, significantly decreased PAI-1, uPA, uPAR and HIF-alpha mRNA levels in Caki-1 cells. Furthermore, Cx32 suppressed the induction of HIF-2alpha protein in Caki-1 cells under hypoxia. PAI-1 mRNA level in Cx32-transfected Caki-1 cells was lower than that of mock transfectant under hypoxic conditions. These results suggest that Cx32 might reduce PAI-1, uPA and uPAR production in metastatic RCC cells via the inhibition of Src-dependent induction of HIF-1alpha and HIF-2alpha gene expression and that Cx32 might suppress hypoxia-inducible gene expression under hypoxic conditions.
Hagiwara
Hiromi
H
Department of Food Science Research for Health, National Institute of Health and Nutrition, Toyama, Shinjuku, Tokyo, Japan. hiromi-h@nih.go.jp
Sato
Hiromi
H
Shirai
Sumiko
S
Kobayashi
Shigeto
S
Fukumoto
Keiko
K
Ishida
Tatsuya
T
Seki
Taiichiro
T
Ariga
Toyohiko
T
Yano
Tomohiro
T
D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis; D002292:Carcinoma, Renal Cell / Q000378:metabolism* / Q000473:pathology; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D017630:Connexins / Q000235:genetics / Q000502:physiology*; D015536:Down-Regulation; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis; D007680:Kidney Neoplasms / Q000378:metabolism* / Q000473:pathology; D009362:Neoplasm Metastasis; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis*; D011956:Receptors, Cell Surface / Q000096:biosynthesis*; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator / Q000096:biosynthesis*; D000097002:Gap Junction beta-1 Protein; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D017630:Connexins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D017395:Plasminogen Activator Inhibitor 1; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator; D000097002:Gap Junction beta-1 Protein; D000099162:Endothelial PAS Domain-Containing Protein 1; C524898:PLAUR protein, human; C051321:SERPINE1 protein, human