title: Inhibition of Rho-associated coiled-coil containing protein kinase enhances the activation of epidermal growth factor receptor in pancreatic cancer cells.
abstract: BACKGROUND
  Rho-associated coiled-coil containing protein kinase (Rho-kinase/ROCK) is involved in various cellular functions including cell proliferation, and is generally considered to be oncogenic, while some studies show that ROCK functions as a negative regulator of cancer progression. As a result, the precise role of ROCK remains controversial. We have previously reported that Rho-kinase/ROCK negatively regulates epidermal growth factor (EGF)-induced cell proliferation in SW480 colon cancer cells. In the present study, we investigated the role of ROCK in EGF receptor (EGFR) signaling in the pancreatic cancer cell lines, Panc1, KP3 and AsPc1.
  
  
  RESULTS
  In these cells, Y27632, a specific ROCK inhibitor, enhanced EGF-induced BrdU incorporation. The blockade of EGF stimulation utilizing anti-EGFR-neutralizing antibodies suppressed Panc1 cell proliferation. EGF induced RhoA activity, as well as the phosphorylation of cofilin and myosin light chain (MLC), both targets of ROCK signaling, and Y27632 suppressed both of these processes, indicating that the phosphorylation of cofilin and MLC by EGF occurs through ROCK in Panc1 cells. EGF-induced phosphorylation of EGFR at tyrosine residues was augmented when the cells were pretreated with Y27632 or were subjected to gene silencing using ROCK-siRNA. We also obtained similar results using transforming growth factor-α. In addition, EGF-induced phosphorylation of p44/p42 mitogen-activated protein kinase and Akt were also enhanced by Y27632 or ROCK-siRNA. Moreover, an immunofluorescence microscope study revealed that pretreatment with Y27632 delayed EGF-induced internalization of EGFR. Taken together, these data indicate that ROCK functions to switch off EGFR signaling by promoting the internalization of the EGFR.
  
  
  CONCLUSIONS
  While EGF first stimulates the activation of the EGFR and subsequently increases cancer cell proliferation, EGF concurrently induces the activation of ROCK, which then turns off the activated EGFR pathway via a negative feedback system.
authors: Department of Gastroenterology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan.
authors: Masanori
authors: M
authors: Nakashima
authors: Seiji
authors: S
authors: Adachi
authors: Ichiro
authors: I
authors: Yasuda
authors: Takahiro
authors: T
authors: Yamauchi
authors: Junji
authors: J
authors: Kawaguchi
authors: Toshimasa
authors: T
authors: Hanamatsu
authors: Takashi
authors: T
authors: Yoshioka
authors: Yukio
authors: Y
authors: Okano
authors: Yoshinobu
authors: Y
authors: Hirose
authors: Osamu
authors: O
authors: Kozawa
authors: Hisataka
authors: H
authors: Moriwaki
mesh_terms: D000577:Amides / Q000494:pharmacology; D057134:Antibodies, Neutralizing / Q000494:pharmacology; D002277:Carcinoma / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000819:agonists* / Q000276:immunology / Q000378:metabolism; D006801:Humans; D010190:Pancreatic Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology
chemical_list: D000577:Amides; D057134:Antibodies, Neutralizing; D047428:Protein Kinase Inhibitors; D011725:Pyridines; C108830:Y 27632; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D054460:rho-Associated Kinases