Amphiregulin Contributes to the Transformed Phenotype of Human Hepatocellular Carcinoma Cells

Abstract

Hepatocellular carcinoma is a major cause of cancer-related deaths. Current treatments are not effective, and the identification of relevant pathways and novel therapeutic targets are much needed. Increasing evidences point to the activation of the epidermal growth factor receptor (EGFR) as an important mechanism in the development of hepatocarcinoma. We previously described that amphiregulin (AR), a ligand of the EGFR, is not expressed in healthy liver but is upregulated during chronic liver injury, the background on which most liver tumors develop. Now, we have studied the expression and role of AR in human hepatocarcinoma. AR expression and function was studied in human liver tumors and cell lines. AR is expressed in human hepatocellular carcinoma tissues and cell lines and behaves as a mitogenic and antiapoptotic growth factor for hepatocarcinoma cells. We provide several lines of evidence, including AR silencing by small interfering RNAs and inhibition of amphiregulin by neutralizing antibodies, showing the existence of an ARmediated autocrine loop that contributes to the transformed phenotype. Indeed, interference with endogenous AR production resulted in reduced constitutive EGFR signaling, inhibition of cell proliferation, anchorage-independent growth, and enhanced apoptosis. Moreover, knockdown of AR potentiated transforming growth factor-B and doxorubicin-induced apoptosis. Conversely, overexpression of AR in SK-Hep1 cells enhanced their proliferation rate, anchorage-independent growth, drug resistance, and in vivo tumorigenic potential. These observations suggest that AR is involved in the acquisition of neoplastic traits in the liver and thus constitutes a novel therapeutic target in human hepatocarcinoma. (Cancer Res 2006; 66(12): 6129-38)

The Human Adenocarcinoma-associated Gene, AGR2, Induces Expression of Amphiregulin through Hippo Pathway Co-activator YAP1 Activation

“…A significant role for AREG has been established in development and neoplasia (19,37,38). Similar to AGR2, AREG expression has also been detected in esophageal, gastric, breast, lung, stomach, colon, prostate, ovarian, and pancreatic cancers (4,5,(22)(23)(24)(25)(26)(27)(28). AREG has also been demonstrated to support the growth of tumor cell lines in vitro and xenografts in vivo (22,39).…”

Involvement of NF-κB/miR-448 regulatory feedback loop in chemotherapy-induced epithelial–mesenchymal transition of breast cancer cells

“…AR has been shown previously to induce differential effects through the EGFR signaling, contributing to the progression of several cancers. [32][33][34][35] The literature showing a connection between AR and EMT is not extensive. A link between EGFR and EMT was found previously; however, these studies have implied that EMT may contribute to resistance to EGFR-directed therapy.…”

Autocrine and Juxtacrine Effects of Amphiregulin on the Proliferative, Invasive, and Migratory Properties of Normal and Neoplastic Human Mammary Epithelial Cells

“…AR is involved in an autocrine loop in several types of cancers, such as colon cancer, pancreatic cancer, and hepatocellular carcinoma, and it is presumed that an AR/EGFR autocrine loop also contributes to breast cancer progression (27)(28)(29). There is significant evidence to support an autocrine loop in breast cancer, since levels of AR protein expression are generally higher in invasive breast carcinomas than in ductal carcinoma in situ (DCIS) or in normal mammary epithelium (30,48,49).…”

“…There is direct evidence that an EGFR/AR autocrine loop exists in pancreatic cancer, colon cancer, and hepatocellular carcinoma (27)(28)(29). AR expression was also found to be strongly correlated with inflammatory breast cancer, and a putative AR/EGFR autocrine loop is suggested to contribute to breast cancer progression (30).…”