Downregulation of the enhancer of zeste homolog 1 transcriptional factor predicts poor prognosis of triple-negative breast cancer patients

PeerJ. 2022 Jul 12:10:e13708. doi: 10.7717/peerj.13708. eCollection 2022.

Abstract

Background: Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer and lacks effective biomarkers. This study seeks to unravel the expression status and the prospective transcriptional mechanisms of EZH1/EZH2 in TNBC tissue samples. Moreover, another objective of this study is to reveal the prognostic molecular signatures for risk stratification in TNBC patients.

Methods: To determine the expression status of EZH1/EZH2 in TNBC tissue samples, microarray analysis and immunohistochemistry were performed on in house breast cancer tissue samples. External mRNA expression matrices were used to verify its expression patterns. Furthermore, the prospective transcriptional mechanisms of EZH1/EZH2 in TNBC were explored by performing differential expression analysis, co-expression analysis, and chromatin immunoprecipitation sequencing analysis. Kaplan-Meier survival analysis and univariate Cox regression analysis were utilized to detect the prognostic molecular signatures in TNBC patients. Nomogram and time-dependent receiver operating characteristic curves were plotted to predict the risk stratification ability of the prognostic-signatures-based Cox model.

Results: In-house TMAs (66 TNBC vs. 106 non-TNBC) and external gene microarrays, as well as RNA-seq datasets (1,135 TNBC vs. 6,198 non-TNBC) results, confirmed the downregulation of EZH1 at both the protein and mRNA levels (SMD = -0.59 [-0.80, -0.37]), as is opposite to that of EZH2 (SMD = 0.74 [0.40, 1.08]). The upregulated transcriptional target genes of EZH1 were significantly aggregated in the cell cycle pathway, where CCNA2, CCNB1, MAD2L1, and PKMYT1 were determined as key transcriptional targets. Additionally, the downregulated transcriptional targets of EZH2 were enriched in response to the hormone, where ESR1 was identified as the hub gene. The six-signature-based prognostic model produced an impressive performance in this study, with a training AUC of 0.753, 0.981, and 0.977 at 3-, 5-, and 10-year survival probability, respectively.

Conclusion: EZH1 downregulation may be a key modulator in the progression of TNBC through negative transcriptional regulation by targeting CCNA2, CCNB1, MAD2L1, and PKMYT1.

Keywords: EZH1; Molecular approaches; Transcriptional regulation; Triple-negative breast cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle Proteins / genetics
  • Down-Regulation / genetics
  • Humans
  • Membrane Proteins / genetics
  • Prognosis
  • Prospective Studies
  • Protein Serine-Threonine Kinases / genetics
  • Protein-Tyrosine Kinases / genetics
  • RNA, Messenger
  • Triple Negative Breast Neoplasms* / genetics

Substances

  • Cell Cycle Proteins
  • Membrane Proteins
  • PKMYT1 protein, human
  • Protein Serine-Threonine Kinases
  • Protein-Tyrosine Kinases
  • RNA, Messenger
  • EZH1 protein, human

Grants and funding

This study was funded by the National Natural Science Foundation of China (NSFC82060309), the Natural Science Foundation of Guangxi, China (2022GXNSFAA), the Key R&D Plan of Science and Technology Plan Project in Qingxiu District, Nanning City (2020020), and the Guangxi Zhuang Autonomous Region Health Commission Self-Financed Scientific Research Project (Z2014245). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.