Angiopoietin pathway gene expression associated with poor breast cancer survival.

PURPOSE

Angiogenesis is one of the hallmarks of cancer and is essential for cancer progression and metastasis. However, clinical trials with vascular endothelial growth factor (VEGF) pathway inhibitors have failed to show overall survival benefit in breast cancer. Targeted therapy against the angiopoietin pathway, a downstream angiogenesis cascade, could be effective in breast cancer. This study investigates the association of angiopoietin pathway gene expression with breast cancer survival using a "big data" approach employing RNA sequencing data from The Cancer Genome Atlas (TCGA).

METHODS

A total of 888 patients with adequate gene expression, disease-free survival (DFS), and overall survival (OS) data were selected for analysis. DFS and OS were calculated for patients with high and low expression of angiopoietin and VEGF pathway genes using TCGA data. Gene-specific thresholds to dichotomize patients into high and low expression were determined and survival plots were generated.

RESULTS

The TCGA cohort was representative of national breast cancer patients with respect to stage, pathology, and survival. High Ang2 gene expression was associated with not only decreased DFS (p = 0.05), but also decreased OS (p < 0.05). High co-expression of Ang2 and its receptor Tie2 was associated with both decreased DFS and OS (p < 0.05). There was strong correlation between angiopoietin and VEGF pathway genes. While high expression of VEGFA alone was not associated with survival, high co-expression with Ang2 was associated with decreased OS.

CONCLUSIONS

This study validates TCGA as a representative database providing genomic data and survival outcomes in breast cancer. Our TCGA data support the angiopoietin pathway as a key mediator in the pathologic angiogenic switch in breast cancer.