Epigenetic Activation of Sox11 in Recurrence and Progression of Ductal Carcinoma In Situ

Background

Ductal Carcinoma In Situ (DCIS) is a non-invasive breast cancer characterized by the excessive proliferation of luminal epithelial cells surrounded by myoepithelial cells. DCIS accounts for approximately 25% of breast cancer screenings, and its potential biological characteristics and prognosis are heterogeneous. Although DCIS itself is not an invasive disease, the risk of its progression to invasive ductal carcinoma (IDC) remains a significant clinical challenge. Therefore, there is an urgent need to develop biomarkers that can predict the progression of DCIS to invasive cancer.

Currently, despite some potential biomarkers like estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2) being available to predict the prognosis of DCIS, more biomarkers for DCIS progression remain an unresolved issue. Previous studies have suggested that TP53 mutations and COX2 overexpression may promote the invasive progression of DCIS, but these have not been clinically validated. Although commercial tests like Oncotype DX DCIS and DCISionRT are used to predict recurrence and progression risk, there is still a need for more research to assess the risks among different DCIS subtypes.

Source of Study

This paper was published in the journal “British Journal of Cancer,” with leading authors Warapen Treekitkarnmongkol, Vandna Shah, Kazuharu Kai, and others. They are affiliated with the University of Texas MD Anderson Cancer Center, King’s College London, and Baylor College of Medicine. The paper was published in May 2024, with background research and sample collection starting from May 2023.

Research Methods

Overview of Research Methods

This study used human cell lines and mouse models to identify and validate candidate risk prediction biomarkers in two independent DCIS cohorts. The research process included gene expression profiling, immunohistochemical analysis, cell experiments, and mouse model analysis.

Detailed Experimental Procedures and Methods

First, the researchers collected 48 samples from the University of Texas MD Anderson Cancer Center, including 40 DCIS tissues and 8 matched normal breast tissues. After obtaining informed consent, a macrodissection of these samples was performed, and RNA was extracted using Qiagen’s RNeasy FFPE Kit (Catalog No: 73504). Gene expression analysis was conducted using Nanostring nCounter technology, profiling 53 target genes related to DCIS and 5 housekeeping genes for normalization.

For the mouse models, the researchers used two types of mice: breast-specific Pten homozygous knockout mice and MMTV-Her2 transgenic mice overexpressing Her2. These mouse models can recapitulate the pathological process of DCIS progression to breast cancer. Mammary gland tissues were collected at different time points for pathological and molecular analysis.

The study also included cell line experiments, using a series of cell lines including MCF10A, 21T series, and DCIS.com, for cell proliferation and spheroid formation assays. Sox11 expression and function were detected using RNA interference techniques and western blot analysis.

Statistical and Data Analysis

All statistical analyses were performed using GraphPad Prism and R software. Statistical tests used included unpaired Student’s t-test and Pearson correlation coefficient. The primary outcome was recurrence-free survival (RFS) time, calculated from the date of initial diagnosis to the subsequent event (DCIS or invasive cancer). Kaplan-Meier method was used to construct survival curves, and Cox proportional hazards model was used to assess the impact of clinical characteristics of DCIS on RFS.

Research Results

Expression of Sox11 in DCIS Recurrence and Progression

RNA sequencing and Nanostring analysis of DCIS samples revealed that high expression of Sox11 was significantly positively correlated with DCIS recurrence score, proliferation marker MKI67, and epigenetic regulator protein EZH2 expression. Further experiments validated that in 21T series cell lines and mouse models, high expression of Sox11 was associated with the progression of DCIS to invasive cancer.

Immunohistochemical analysis showed that the expression of Sox11 and EZH2 was significantly higher in DCIS tissues compared to normal breast tissues, especially in high-grade and HER2+ subtypes. Additionally, Kaplan-Meier survival analysis demonstrated that high expression of Sox11 was significantly associated with shorter RFS time.

Epigenetic Regulation Mechanism

The study also revealed the epigenetic regulatory mechanism of Sox11 in the progression of DCIS. The research indicated that activation of Akt kinase could regulate Sox11 expression by altering histone modifications in the Sox11 promoter region (such as H3K4me3 and H3K27ac). Inhibiting Akt activity significantly reduced these active histone marks, thereby decreasing Sox11 expression and cell proliferation capacity.

Research Conclusion

This study revealed the crucial role of Sox11 in DCIS recurrence and progression and its epigenetic regulatory mechanism. These findings suggest that Sox11 could be a potential prognostic biomarker and may serve as a powerful tool for personalized treatment and management of DCIS. Future research should focus on the therapeutic potential of Sox11 and its upstream regulatory pathways, such as HER2, Akt, and EZH2.

Research Highlights

1. Significant Discovery: Sox11 expression is significantly associated with DCIS recurrence and progression.
2. Epigenetic Mechanism: Revealed the role of Akt-mediated histone modifications in regulating Sox11 expression.
3. Clinical Significance: Sox11 could serve as a potential biomarker for personalized treatment of DCIS patients.