title: Invasive ability of human renal cell carcinoma cell line Caki-2 is accelerated by gamma-aminobutyric acid, via sustained activation of ERK1/2 inducible matrix metalloproteinases.
abstract: Gamma-aminobutyric acid (GABA) was first discovered as an inhibitory neurotransmitter in the central nervous system (CNS) and has been reported to have a variety of functions, including regulation of cell division, cell differentiation and maturation, and to be involved in the development of certain cancers outside the CNS. In the present study, using the human renal cell carcinoma cell line Caki-2, we demonstrated that GABA stimulation significantly increased the expression of MMP-2 and -9 and subsequently increased the invasive activity of the cancer cells. Because MAPK signaling is one of the key regulators of MMP expression, we further evaluated MAPK signaling after stimulation with GABA. It was found that GABA stimulation promoted the phosphorylation of MAPKs, including ERK1/2, JNK, and p38. ERK1/2 phosphorylation was sustained for up to 12 h, while phosphorylation of JNK and p38 returned to the endogenous level by 30 min. It was noteworthy that the ras/raf/MEK/ERK pathway inhibitor PD98059 attenuated GABA-induced MMP-9 expression and that both PD98059 and MMP inhibitors attenuated the GABA-induced invasive activity of Caki-2 cells. Moreover, data obtained by depletion of the MEK/ERK pathway using interfering RNA transfection of Caki-2 cells clearly corroborated the above results, as both MMP-9 expression and GABA-induced invasive ability were decreased significantly. We also demonstrated that the GABA-induced increase in invasive ability via ERK1/2 up-regulation was mediated mainly through the GABA-B receptor. These results indicate that GABA stimulation promotes cancer cell invasion and that the effect is partly due to ERK1/2-dependent up-regulation of MMPs.
authors.affiliation: Department of Urology, Osaka Medical College, Osaka, Japan.
authors.forename: Teruo
authors.initials: T
authors.lastname: Inamoto
authors.forename: Haruhito
authors.initials: H
authors.lastname: Azuma
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kiyama
authors.forename: Takanobu
authors.initials: T
authors.lastname: Ubai
authors.forename: Yatsugu
authors.initials: Y
authors.lastname: Kotake
authors.forename: Masahito
authors.initials: M
authors.lastname: Watanabe
authors.forename: Yoji
authors.initials: Y
authors.lastname: Katsuoka
mesh_terms: D002292:Carcinoma, Renal Cell / Q000201:enzymology / Q000473:pathology*; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D006801:Humans; D007680:Kidney Neoplasms / Q000201:enzymology / Q000473:pathology*; D020782:Matrix Metalloproteinases / Q000096:biosynthesis*; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology*; D009361:Neoplasm Invasiveness; D018079:Receptors, GABA / Q000032:analysis / Q000502:physiology; D015398:Signal Transduction; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D018079:Receptors, GABA; D005680:gamma-Aminobutyric Acid; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020782:Matrix Metalloproteinases