Reg IV activates the epidermal growth factor receptor/Akt/AP-1 signaling pathway in colon adenocarcinomas.
OBJECTIVE
Reg IV, a secreted protein and member of the Reg multigene family, is up-regulated in malignancies of the human gastrointestinal tract, including colorectal carcinoma (CRC). However, in vitro signal transduction pathway(s) utilized by Reg IV are not yet known.


METHODS
To determine the signaling pathway(s) responsive to Reg IV, we examined the effects of purified recombinant human Reg IV (rhR4) on HCT116 and HT29 colon adenocarcinoma cells.


RESULTS
Addition of rhR4 to cultures led to a dose-dependent increase in cell number similar to that observed after treatment with epidermal growth factor (EGF). In addition, rhR4 treatment resulted in rapid phosphorylation of EGF receptor at Tyr992 and Tyr1068 and Akt at Thr308 and Ser473. Using luciferase reporter gene assays, we demonstrated that Reg IV signaling through EGF receptor and Akt results in increased activator protein-1 (AP-1) transcription factor activity. Real-time reverse-transcription polymerase chain reaction and Western blot analyses revealed quantitative increases in c-Jun, JunB, JunD, and FosB expression associated with increased AP-1 activity. Electrophoretic mobility shift assay further revealed significant increases in AP-1 binding activity in rhR4-treated cells, with increased supershift in the presence of antibodies to JunB, JunD, and FosB. Furthermore, rhR4 treatments led to the increased expression of Bcl-2, Bcl-XL, survivin, and matrilysin, genes associated with a poor prognosis in advanced CRC.


CONCLUSIONS
Reg IV is a potent activator of the EGF receptor/Akt/AP-1 signaling pathway in CRC. Disruption of Reg signaling may have utility as a therapeutic intervention for human gastrointestinal adenocarcinomas.
Bishnupuri
Kumar S
KS
Department of Internal Medicine, Washington University School of Medicine, St Louis, Missouri 63110, USA.
Luo
Qizhi
Q
Murmu
Nabendu
N
Houchen
Courtney W
CW
Anant
Shrikant
S
Dieckgraefe
Brian K
BK
D000230:Adenocarcinoma / Q000235:genetics* / Q000503:physiopathology*; D017209:Apoptosis; D003110:Colonic Neoplasms / Q000235:genetics* / Q000503:physiopathology*; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D037181:Lectins, C-Type / Q000502:physiology*; D009362:Neoplasm Metastasis; D000073718:Pancreatitis-Associated Proteins; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014407:Tumor Cells, Cultured
D037181:Lectins, C-Type; D000073718:Pancreatitis-Associated Proteins; C428528:REG4 protein, human; D018808:Transcription Factor AP-1; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt