ZHX2 promotes HIF1α oncogenic signaling in triple-negative breast cancer.

Chengheng Liao,Wentong Fang,William Y Kim,Cheng Fan,Lei Bao,Weibo Luo,Leng Han,Giada Zurlo,Jeremy M Simon,Youqiong Ye,Ujjawal Manocha,Qing Zhang,Travis S Ptacek,Rachel Shi,Lee-Wei Yang,Hong-Rui Lin,Yan Peng,Christopher Llynard Ortiz

doi:10.7554/elife.70412

Abstract

Triple-negative breast cancer (TNBC) is an aggressive and highly lethal disease, which warrants the critical need to identify new therapeutic targets. We show that Zinc Fingers and Homeoboxes 2 (ZHX2) is amplified or overexpressed in TNBC cell lines and patients. Functionally, depletion of ZHX2 inhibited TNBC cell growth and invasion in vitro, orthotopic tumor growth, and spontaneous lung metastasis in vivo. Mechanistically, ZHX2 bound with hypoxia-inducible factor (HIF) family members and positively regulated HIF1α activity in TNBC. Integrated ChIP-seq and gene expression profiling demonstrated that ZHX2 co-occupied with HIF1α on transcriptionally active promoters marked by H3K4me3 and H3K27ac, thereby promoting gene expression. Among the identified ZHX2 and HIF1α coregulated genes, overexpression of AP2B1, COX20, KDM3A, or PTGES3L could partially rescue TNBC cell growth defect by ZHX2 depletion, suggested that these downstream targets contribute to the oncogenic role of ZHX2 in an accumulative fashion. Furthermore, multiple residues (R491, R581, and R674) on ZHX2 are important in regulating its phenotype, which correspond with their roles on controlling ZHX2 transcriptional activity in TNBC cells. These studies establish that ZHX2 activates oncogenic HIF1α signaling, therefore serving as a potential therapeutic target for TNBC.

Highlights

Triple-negative breast cancer (TNBC) accounts for 15-20% of all breast cancer (Anders and Carey, 2009)
We showed that Zinc Fingers and Homeoboxes 2 (ZHX2) shRNA induced phenotypes in TNBC cells could be completely rescued by shRNA-resistant ZHX2 in two TNBC cell lines (Figure 2I-N and Figure 2-figure supplement 1A-G), suggesting that these phenotypes were due to on-target depletion of ZHX2 by shRNAs. 193 ZHX2 is important for TNBC cell proliferation in vivo to examine the ability of ZHX2 to maintain TNBC tumor growth in vivo, we first constructed firefly luciferase stably expressing MDA-MB-231 cells (MDA-MB-231-luc) followed by infecting these cells with doxycycline (Dox) inducible control or ZHX2 shRNAs (Teton sh[43], sh45)
It is important to note that the detailed mechanism on how ZHX2 binds with HIF1 and 293 transactivates HIF1 signaling remains unclear, which awaits future investigation

Summary

Introduction

Triple-negative breast cancer (TNBC) accounts for 15-20% of all breast cancer (Anders and Carey, 2009). TNBC is associated with a more aggressive clinical history, a higher likelihood of distant metastasis, shorter survival and a higher mortality rate compared to other subtypes of breast cancer (Anders and Carey, 2009). Recent studies illustrate high rates of brain metastasis in TNBC that is associated with poor survival (Heitz et al, 2009; Lin et al, 2008; Niwińska et al, 2010). Since TNBCs do not express estrogen receptor (ER), progesterone receptor (PR) or human epidermal growth factor receptor 2 (HER2), treatment options have historically been limited to chemotherapy (Masui et al, 2013), which has significant toxicity and a suboptimal impact on the five-year relapse rate. It is critical to identify novel therapeutic targets in TNBC.

Objectives

Results

Conclusion