Integrative analysis of AGR2 based on data mining reveals new insights in breast cancer

Abstract

Background: Belonging to the protein disulfide isomerase (PDI) family, anterior gradient 2 (AGR2) is overexpressed in mucus-secreting cells and endocrine organs such as breast, lung, and ovarian, but its exact function and regulation remain unclear. We aimed to perform integrative analysis of AGR2 in breast cancer.Methods: In our study, a serious of bioinformatic online databases were used to analyze the expression, regulation, prognostic value, and function of AGR2 in breast cancer.Results: The results suggested that AGR2 mRNA was overexpressed in non-basal-like or non-triple-negative breast cancer, but underexpressed in basal-like/ triple-negative breast cancer. AGR2 mRNA expression was correlated with its protein expression. Moreover, the expression of AGR2 was lower in more malignant breast cancer. Furthermore, we also found that DNA methylation, rather than copy number variation, led to AGR2 mRNA overexpression. Prognosis analysis showed no significant correlation between AGR2 level and survival, but in subtype investigation, patients with higher AGR2 level had a significantly better outcome in patients with basal-like / triple-negative breast cancer. Enrichment analysis for co-expression genes of AGR2 revealed that gene sets enriched for chromosome segregation, DNA conformation change, chromosomal region, and GABA receptor activity may play important roles in breast cancer, and that the most significant pathway was “ribosome biogenesis in eukaryotes”, in which negative co-expression genes of AGR2 were enriched.Conclusions: Overexpression of AGR2 was found in less malignant breast cancer, for the first time, our results propose that DNA methylation rather than copy number variation leads to AGR2 overexpression, which can predict favorable prognosis in basal-like/ triple-negative breast cancer, and AGR2 could be a possible regulator of ribosome biogenesis in patients with breast cancer.