The Endogenous GRP78 Interactome in Human Head and Neck Cancers: A Deterministic Role of Cell Surface GRP78 in Cancer Stemness

Hsin-Ying Chen,Ann-Joy Cheng,Yun-Shien Lee,Joseph Tung-Chieh Chang,Guo-Rung You,Kun-Yi Chien

doi:10.1038/s41598-017-14604-5

Abstract

Cell surface glucose regulated protein 78 (GRP78), an endoplasmic reticulum (ER) chaperone, was suggested to be a cancer stem cell marker, but the influence of this molecule on cancer stemness is poorly characterized. In this study, we developed a mass spectrometry platform to detect the endogenous interactome of GRP78 and investigated its role in cancer stemness. The interactome results showed that cell surface GRP78 associates with multiple molecules. The influence of cell population heterogeneity of head and neck cancer cell lines (OECM1, FaDu, and BM2) according to the cell surface expression levels of GRP78 and the GRP78 interactome protein, Progranulin, was investigated. The four sorted cell groups exhibited distinct cell cycle distributions, asymmetric/symmetric cell divisions, and different relative expression levels of stemness markers. Our results demonstrate that cell surface GRP78 promotes cancer stemness, whereas drives cells toward a non-stemlike phenotype when it chaperones Progranulin. We conclude that cell surface GRP78 is a chaperone exerting a deterministic influence on cancer stemness.

Highlights

glucose regulated protein 78 (GRP78) has two reported functions in subcellular compartments: as an endoplasmic reticulum (ER) chaperone in the intracellular compartment, and as a proposed signaling receptor in the plasma membrane (PM) compartment
GRP78 was detected in the non-PM compartments of both OECM1 and FaDu cells (Fig. 1B), demonstrating that our platform is capable of detecting GRP78 and its endogenous interactome
Except keratin-related proteins and GRP78, the top 25 candidates in the non-PM compartments of OECM1 and FaDu cells ranked by their D4/H4 ratios are listed in supplemental Tables S1 and S2

Summary

Introduction

GRP78 has two reported functions in subcellular compartments: as an endoplasmic reticulum (ER) chaperone in the intracellular compartment, and as a proposed signaling receptor in the plasma membrane (PM) compartment. Several types of malignant cancers express GRP78 on their cell surface[9,10] Because of this cell surface expression, GRP78 has been hypothesized to function as a signaling receptor that contributes to malignancy. Receptor in a different subcellular compartment is unknown It is unknown whether endogenous GRP78 simultaneously associates with multiple molecules on the cell surface of human cancer cells. In this study, we examined the endogenous interactome of GRP78 in the subcellular compartments of cancer cells using mass spectrometry and human head and neck cancer (HNC) cell lines as the study model. Serial dilutions of sorted HNC cells based on cell surface GRP78 levels has a direct influence on xenograft tumorigenesis in mice[16], suggesting that cell surface GRP78 can influence the self-renewal ability of cancer stem cells. We investigated the influence of the association between cell surface GRP78 and the chosen interactome candidate on cell cycle distribution, asymmetric cell division, and expression of stemness associated markers

Methods

Results

Conclusion