Pro-neoplastic effects of amphiregulin in colorectal carcinogenesis.

PURPOSE: Epidermal growth factor (EGF) family plays critical roles in intestinal epithelial growth and transformation. Amphiregulin (AREG) is a member of the EGF family, and has been suggested to be more important to tumor versus normal growth. The precise roles of AREG in colorectal carcinogenesis have not been thoroughly elucidated. METHODS: AREG expression was analyzed in colon cancer specimens using immunohistochemistry. Genetically disruption of AREG in APC (min/+) mouse was achieved by crossbreeding AREG knockout mouse with APC (min/+) mice. Knockdown AREG expression was accomplished by using plasmid-based RNA interference. Growth-stimulatory effects of AREG were determined using cell co-culture systems. RESULTS: AREG was expressed in both epithelial and stromal compartments in human colon cancer; however, it was regulated by different mechanisms. AREG was predominantly regulated at transcriptional level in colon cancer cells while both transcriptional and post-transcriptional mechanisms were involved in colon cancer derived myofibroblasts. Functionally, knockout of AREG strongly reduced tumorigenicity in APC (min/+) mice. Immunohistochemistry demonstrated the coordinate expression of AREG, EGF receptor activity, and cell proliferation marker in APC (min/+) mouse adenoma, indicating the growth-stimulatory function of AREG signaling in tumor development. Furthermore, we demonstrated that AREG may stimulate tumor cell growth through both autocrine and paracrine pathways in cell culture models. Knockdown of AREG impaired the ability of anchorage-independent growth of transformed intestinal epithelial cells. On the other hand, myofibroblast-produced AREG stimulated the growth of colon cancer cells when co-cultured in extracellular matrix. CONCLUSIONS: AREG plays pro-neoplastic roles in colorectal carcinogenesis and may be targeted for colon cancer prevention and treatment.