β-catenin interaction with NHERF1 and RASSF1A methylation in metastatic colorectal cancer patients.

Laura Schirosi,Giusi Graziano,Livia Fucci,Giovanni Simone,Stefania Tommasi,Rosamaria Pinto,Anita Mangia,Annalisa Mazzotta,Giuseppina Opinto

doi:10.18632/oncotarget.12280

Abstract

There is an increasing need to identify new biomarkers in colorectal cancer (CRC) to further characterize this malignancy. β-catenin plays a central role in the Wnt signaling pathway. It also binds Na+/H+ exchanger regulating factor 1 (NHERF1) and interacts with the RAS-association domain family 1, isoform A (RASSF1A), but the mechanisms of this possible crosstalk are still not fully understood. In this study, we analyzed for the first time the different subcellular expression of β-catenin, NHERF1, and RASSF1A and their relationships with RASSF1A methylation in the progression of CRC. We assessed immunohistochemical expression and RASSF1A methylation in 51 patients with stage IV colorectal cancer. Biomarker expression analysis was carried out considering the tumor-adjacent normal tissue, the primary tumor, and the paired liver metastases. Regarding the tumor compartment, it was found that cytoplasmic β-catenin expression was positively correlated to membranous (r = 0.3002, p = 0.0323) and nuclear NHERF1 (r = 0.293, p = 0.0368). In the liver metastases, instead, we found a positive correlation of cytoplasmic and nuclear β-catenin expression with RASSF1A methylation (r = 0.4019, p = 0.0068 and r = 0.3194, p = 0.0345, respectively).In conclusion, our results showed that β-catenin was the crucial protagonist in metastatic CRC through different effector proteins involved in this developing process. In tumor tissues, β-catenin was predominantly associated with NHERF1 in a dynamic context, while interestingly in liver metastases, we noted an increase of its oncogenic function through RASSF1A inactivation.

Highlights

Colorectal cancer (CRC) is the third most frequent cancer type and its incidence continues to increase worldwide
We know that β-catenin plays a central role in the Wnt signaling pathway in CRC, binding Na+/H+ exchanger regulating factor 1 (NHERF1) [25] and interacting with RASSF1A [26]
Hayashi’s model reported a cytoplasmic re-expression in CRC progression [11]. These results suggested that cytoplasmic NHERF1 expression could be needed to develop the oncogenic event in carcinoma and different mechanisms could probably control its subcellular sub-localization, such as gene mutations and phosphorylation [30]

Summary

INTRODUCTION

Colorectal cancer (CRC) is the third most frequent cancer type and its incidence continues to increase worldwide. Shibata T et al [9] have suggested a close association between β-catenin and Na+/H+ exchanger regulating factor 1/ezrin-radixin-moesin binding phosphoprotein of 50 kDa (NHERF1/EBP50) through its PDZ domain in vitro and in vivo. This complex enhances Wnt signaling and may cooperate in the development of cancer. We examined the expression and sub-localization of β-catenin, NHERF1 and RASSF1A proteins, in addition to the methylation status of RASSF1A, in tumor adjacent normal tissue, primary tumors, and paired liver metastases of metastatic CRC. For the first time, the interactions and relationships among the three proteins and RASSF1A methylation in order to investigate their biological meaning in metastatic CRC

RESULTS

DISCUSSION

Findings

MATERIALS AND METHODS