S-nitrosylated and non-nitrosylated COX2 has differential expression and distinct subcellular localization in normal and breast cancer tissue

Abstract

Immunohistochemical staining in breast cancer shows both gain and loss of COX2 expression with disease risk and progression. We investigated four common COX2 antibody clones and found high specificity for purified human COX2 for three clones; however, recognition of COX2 in cell lysates was clone dependent. Biochemical characterization revealed two distinct forms of COX2, with SP21 recognizing an S-nitrosylated form and CX229 and CX294 appearing to recognize the same non-nitrosylated COX2 antigen. We found S-nitrosylated and nonnitrosylated COX2 occupy different subcellular locations in normal and breast cancer tissue, implicating distinct synthetic/trafficking pathways and function. Dual stains of ~2000 breast cancer cases show early onset breast cancer has increased expression of both forms of COX2 compared to postmenopausal cases. Our results highlight the strengths of using multiple, highly characterized antibody clones for COX2 immunohistochemical studies and raise the prospect that S-nitrosylation of COX2 may play a role in breast cancer biology.

Characterization of weaning-induced breast involution in women: implications for young women’s breast cancer

“…Since previous studies report the mammary epithelial cell as the dominant source of COX-2 in the mammary gland 36 , we evaluated our breast tissue cohort for epithelial cell expression of COX-2. For this analysis, we utilized two COX-2-specific antibody clones reported to differentially recognize posttranslationally modified COX-2, with combined assessment being a better representation of total COX-2 than single antibody staining 37 . Antibody signals were captured by lobule area and grouped by time post-wean, with high and low signals for each antibody clone determined by K-means cluster analysis.…”

S-nitrosylated and non-nitrosylated COX2 have differential expression and distinct subcellular localization in normal and breast cancer tissue

“…The data generated and analyzed during the current study are publicly available in the figshare repository: https://doi.org/10.6084/m9.figshare.13009985 67 . The clinical data that support the findings of this study are available from the corresponding author upon reasonable request, as described in the data record above.…”