Protease Nexin I is a feedback regulator of EGF/PKC/MAPK/EGR1 signaling in breast cancer cells metastasis and stemness

Tingting Tang,Siwei Deng,Liang Jin,Yi Pan,Lingyu Ni,Xinping Li,Qinhua Zhu,Gaole Zhu,Tiansong Xia,Yanfeng Zhang,Xinyuan Chen,Yingshan Wang,Ke Zen

doi:10.1038/s41419-019-1882-9

Abstract

Breast cancer is the most prevalent cancer in women worldwide, which remains incurable once metastatic. Breast cancer stem cells (BCSCs) are a small subset of breast cancer cells, which are the radical cause of drug resistance, tumor relapse, and metastasis in breast cancer. The extracellular serine protease inhibitor serpinE2, also named protease nexin-1 (PN-1), contributes to enhanced metastasis of cancer cells mainly by remodeling the tumor matrix. In this study, we found that PN-1 was up-regulated in breast cancer, which promoted cell invasion, migration and stemness. Furthermore, by using specific inhibitors, we discovered that epidermal growth factor (EGF) up-regulated PN-1 in breast cancer cells through cascade activation of epidermal growth factor receptor (EGFR) to the activation of protein kinase Cδ (PKCδ), mitogen-activated protein kinase (MEK) and extracellular signal-related kinase (ERK), which finally led to the up-regulation of early growth response protein 1 (EGR1). Moreover, EGF signaling was further activated as a feedback of PN-1 up-regulation through PN-1 blocking HtrA1. Taken together, our findings revealed a novel signaling axis that up-regulated PN-1 expression in breast cancer cells, and the new mechanism of PN-1-promoted breast cancer metastasis, which may provide new insights into identifying novel therapeutic targets for breast cancer.

Highlights

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer-related death among females[1]
By performing RNA sequencing in MCF-7 cells and MCF-7 spheroid cells enriched in BCSCs14, we found protease nexin-1 (PN-1) was the highest up-regulated gene in MCF-7 spheroid cells compared with MCF-7 cells, which was discovered in the aggressive breast cancer cell line, MDA-MB-231 cells and human breast cancer tissues
We cultured MCF-7 spheroid cells by using the 3D semi-solid system[14], in which the cells grew into homogeneous non-adherent spheroids, which were enriched in CD44+/CD24− MCF-7 cells (BCSCs) (Fig. 1a) and had higher expression of stem cell markers, such as aldehyde dehydrogenase 1 family member A1 (ALDH1A1), SRYbox 2 (SOX2), octamer-binding transcription factor 4 (OCT4), and Nanog (Fig. 1b)

Summary

Introduction

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer-related death among females[1]. Tumor metastasis caused the majority of the deaths from breast cancer instead of the primary tumor[2,3]. Accumulating evidence indicated that the recurrent and distant metastatic tumors are related to breast cancer stem cells (BCSCs), which contribute to the development and overall aggressiveness of the recurrent or metastatic. Recent studies showed that increased PN-1 in many cancer types, including breast cancer[7,8,9,10,11], was associated with enhanced tumor metastasis. PN-1 was reported to predict poor outcome in breast cancer patients with estrogen receptor alpha (ER-α)-negative tumors[12].

Methods

Results

Conclusion