Elsevier

Neoplasia

Volume 10, Issue 3, March 2008, Pages 287-297
Neoplasia

Inhibition of JAK1, 2/STAT3 Signaling Induces Apoptosis, Cell Cycle Arrest, and Reduces Tumor Cell Invasion in Colorectal Cancer Cells

https://doi.org/10.1593/neo.07971Get rights and content
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open access

Abstract

Abnormalities in the STAT3 pathway are involved in the oncogenesis of several cancers. However, the mechanism by which dysregulated STAT3 signaling contributes to the progression of human colorectal cancer (CRC) has not been elucidated, nor has the role of JAK, the physiological activator of STAT3, been evaluated. To investigate the role of both JAK and STAT3 in CRC progression, we inhibited JAK with AG490 and depleted STAT3 with a SiRNA. Our results demonstrate that STAT3 and both JAK1 and 2 are involved in CRC cell growth, survival, invasion, and migration through regulation of gene expression, such as Bcl-2, p16ink4a, p21waf1/cip1, p27kip1, E-cadherin, VEGF, and MMPs. Importantly, the FAK is not required for STAT3-mediated regulation, but does function downstream of JAK. In addition, our data show that proteasome-mediated proteolysis promotes dephosphorylation of the JAK2, and consequently, negatively regulates STAT3 signaling in CRC. Moreover, immunohistochemical staining reveals that nuclear staining of phospho-STAT3 mostly presents in adenomas and adenocarcinomas, and a positive correlation is found between phospho-JAK2 immunoreactivity and the differentiation of colorectal adenocarcinomas. Therefore, our findings illustrate the biologic significance of JAK1, 2/STAT3 signaling in CRC progression and provide novel evidence that the JAK/STAT3 pathway may be a new potential target for therapy of CRC.

Abbreviations

CRC
colorectal cancer
JAK
Janus kinase
MMP9
matrix metalloproteinase 9
STAT
signal transducer and activator of transcription
VEGF
vascular endothelial growth factor

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This work was supported by grants from the National Basic Research Program of China (973 program) (no. 2005CB522400), the National Science Fund for Distinguished Young Scholars to F.J.Y. (no. 30625034), and the National Nature Science Foundation of China to C.Y.X. (no. 30500235).