Erb-b2 Receptor Tyrosine Kinase 2 (ERBB2) Promotes ATG12-Dependent Autophagy Contributing to Treatment Resistance of Breast Cancer Cells

Yongqiang Chen,Jayce Bi,Elizabeth S Henson,Shujun Huang,Ruobing Wang,Spencer B Gibson

doi:10.3390/cancers13051038

Abstract

Simple SummaryExpression of the tyrosine kinase receptor ERBB2 in cancer cells leads to drug resistance. Autophagy, a “self-eating” process inside the cell, is a mechanism for drug resistance in cancer cells. It has been shown that ERBB2 activation leads to increased autophagy in breast cancer cells, but the underlying mechanisms remains unclear. In this study, we demonstrated that ERBB2 promotes autophagy by increasing the protein levels of the autophagy gene ATG12 (autophagy-related 12), contributing to the resistance of breast cancer cells to chemotherapy drugs or ERBB2-targeted antibody treatments. We further showed that ATG12 expression in breast tumors containing ERBB2 correlated with a worse patient survival outcome. Finally, lapatinib is an inhibitor for both EGFR and ERBB2 tyrosine kinases in the EGFR protein family and promotes autophagy in cells containing only EGFR but inhibits autophagy in cells containing only ERBB2. Taken together, this suggests that ERBB2 promotes autophagy through upregulation of ATG12.The epidermal growth factor receptor (EGFR) family member erb-b2 receptor tyrosine kinase 2 (ERBB2) is overexpressed in many types of cancers leading to (radio- and chemotherapy) treatment resistance, whereas the underlying mechanisms are still unclear. Autophagy is known to contribute to cancer treatment resistance. In this study, we demonstrate that ERBB2 increases the expression of different autophagy genes including ATG12 (autophagy-related 12) and promotes ATG12-dependent autophagy. We clarify that lapatinib, a dual inhibitor for EGFR and ERBB2, promoted autophagy in cells expressing only EGFR but inhibited autophagy in cells expressing only ERBB2. Furthermore, breast cancer database analysis of 35 genes in the canonical autophagy pathway shows that the upregulation of ATG12 and MAP1LC3B is associated with a low relapse-free survival probability of patients with ERBB2-positive breast tumors following treatments. Downregulation of ERBB2 or ATG12 increased cell death induced by chemotherapy drugs in ERBB2-positive breast cancer cells, whereas upregulation of ERBB2 or ATG12 decreased the cell death in ERBB2-negative breast cancer cells. Finally, ERBB2 antibody treatment led to reduced expression of ATG12 and autophagy inhibition increasing drug or starvation-induced cell death in ERBB2-positive breast cancer cells. Taken together, this study provides a novel approach for the treatment of ERBB2-positive breast cancer by targeting ATG12-dependent autophagy.

Highlights

The epidermal growth factor receptor (EGFR) members including EGFR, erb-b2 receptor tyrosine kinase 2 (ERBB2/HER2), ERBB3 and ERBB4, are overexpressed or activationmutated in many types of cancers, especially in breast, ovarian and non-small cell lung cancers, which is associated with treatment resistance, metastasis, and poor prognosis [1,2]
We demonstrate that ERBB2 promotes autophagy involving the upregulation of autophagy proteins
To investigate the role of ERBB2 in autophagy, we knocked out ERBB2 in the breast cancer cell line SKBR3 expressing a high level of ERBB2 by a double nickase-based CRISPR/Cas9 system (Figure 1A)

Summary

Introduction

The epidermal growth factor receptor (EGFR) members including EGFR, erb-b2 receptor tyrosine kinase 2 (ERBB2/HER2), ERBB3 and ERBB4, are overexpressed or activationmutated in many types of cancers, especially in breast, ovarian and non-small cell lung cancers, which is associated with (radio- and chemotherapy) treatment resistance, metastasis, and poor prognosis [1,2]. Resistance to ERBB2-targeted therapy including the use of trastuzumab, an anti-ERBB2 monoclonal antibody, and lapatinib, a small molecule kinase inhibitor of ERBB2 and EGFR, is associated with alternations of signal transduction pathways, apoptosis, and cell cycle control in breast cancer [7]. Autophagy (macroautophagy) is known to play important roles in therapy resistance in cancers [8,9] It is an intracellular degradation process characterized by the formation of the double-membraned structure autophagosome [10,11]. Our previous study demonstrated that, when cancer cells were treated under hypoxia, a low level of autophagy promoted cell survival at an early time of hypoxia, whereas an enhanced level of autophagy induced autosis (a type of autophagic cell death) at a later time of hypoxia [12]. The roles of ERBB2 in regulating autophagy and autophagy in ERBB2-induced treatment resistance need to be further defined

Methods

Results

Discussion

Conclusion