TrkA Interacts with and Phosphorylates STAT3 to Enhance Gene Transcription and Promote Breast Cancer Stem Cells in Triple-Negative and HER2-Enriched Breast Cancers.

Angelina T Regua,Yang Yu,Roy Strowd,Hui-Wen Lo,Calvin J Wagner,Daniel L Doheny,Dongqin Zhu,Grace L Wong,Noah R Aguayo,Guangxu Jin,Peiqing Sun,Austin Arrigo,Jiayuh Lin,Sara G Manore,Jimmy Ruiz,Sara Abu Jalboush,Alexandra Thomas,Michael D Chan

doi:10.3390/cancers13102340

Abstract

Simple SummaryBreast cancer is the leading cancer in American women. Due to the inherent aggressiveness of triple-negative and HER2-enriched breast cancers, it is imperative to identify novel molecular targets for therapeutic intervention. Due to their abnormal activities in metastatic breast cancers, JAK2–STAT3 and TrkA pathways have been individually implicated in aggressive breast tumors. However, their co-activation and signaling interactions have not been thoroughly investigated. Therefore, our study aimed to elucidate the extent of crosstalk between JAK2–STAT3 and TrkA signaling pathways and its impact on breast cancer. Our data revealed a novel interaction between TrkA and STAT3, and that this interaction results in STAT3 phosphorylation and activation by TrkA, leading to enhanced stemness gene expression and stem cell renewal. We further found that the co-activation of JAK2–STAT3 and TrkA pathways is correlated with shorter time to develop overall and organ-specific metastasis, suggesting that this signaling crosstalk underlies the aggressiveness of triple-negative and HER2-enriched breast cancers.JAK2–STAT3 and TrkA signaling pathways have been separately implicated in aggressive breast cancers; however, whether they are co-activated or undergo functional interaction has not been thoroughly investigated. Herein we report, for the first time that STAT3 and TrkA are significantly co-overexpressed and co-activated in triple-negative breast cancer (TNBC) and HER2-enriched breast cancer, as shown by immunohistochemical staining and data mining. Through immunofluorescence staining–confocal microscopy and immunoprecipitation–Western blotting, we found that TrkA and STAT3 co-localize and physically interact in the cytoplasm, and the interaction is dependent on STAT3-Y705 phosphorylation. TrkA–STAT3 interaction leads to STAT3 phosphorylation at Y705 by TrkA in breast cancer cells and cell-free kinase assays, indicating that STAT3 is a novel substrate of TrkA. β-NGF-mediated TrkA activation induces TrkA–STAT3 interaction, STAT3 nuclear transport and transcriptional activity, and the expression of STAT3 target genes, SOX2 and MYC. The co-activation of both pathways promotes breast cancer stem cells. Finally, we found that TNBC and HER2-enriched breast cancer with JAK2–STAT3 and TrkA co-activation are positively associated with poor overall metastasis-free and organ-specific metastasis-free survival. Collectively, our study uncovered that TrkA is a novel activating kinase of STAT3, and their co-activation enhances gene transcription and promotes breast cancer stem cells in TNBC and HER2-enriched breast cancer.

Highlights

Breast cancer is the most commonly diagnosed cancer in American women and is the second-leading cause of cancer-related deaths among women [1]
We show that tyrosine kinase A (TrkA) interacts directly with and phosphorylates STAT3 on Y705 to promote oncogenic gene transcription, implicating a novel mechanism to activate STAT3-mediated breast cancer metastasis in TrkA-overexpressing tumors
To determine the extent to which JAK2–STAT3 and TrkA signaling pathways are coactivated in breast tumor samples, we performed IHC staining on 33 node-positive breast carcinomas across three major subtypes to detect phosphorylated TrkA (Y490) and STAT3 (Y705) proteins

Summary

Introduction

Breast cancer is the most commonly diagnosed cancer in American women and is the second-leading cause of cancer-related deaths among women [1]. Breast cancers can be categorized into five separate subtypes: luminal A (ER+/PR+), luminal B With high Ki-67), normal breast-like, HER2-positive (HER2-enriched), and triple-negative (ER−/PR−/HER2−; TNBC). Triple-negative and HER2-enriched subtypes are diagnosed in up to 30% of breast cancer cases and are considered more aggressive than other subtypes. As opposed to surgical resection and adjuvant chemotherapy, most patients with triplenegative and HER2-positive breast cancer undergo systemic neoadjuvant chemotherapy as a standard of care, showing high pathological response and positive long-term outcome [2,3]. Patients with recurrent breast cancer experience high rates of morbidity and mortality [4]. There is an urgent need to identify new molecular targets that drive breast cancer growth and progression and develop therapeutic intervention against these targets

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