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

Abstract

Immunohistochemical (IHC) 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 recognizing non-nitrosylated COX2 antigen. We found S-nitrosylated and non-nitrosylated 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 had 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 IHC studies and raise the prospect that S-nitrosylation of COX2 may play a role in breast cancer biology.

Nitric oxide favours tumour-promoting inflammation through mitochondria-dependent and -independent actions on macrophages

“…Similar to iNOS, COX-2/PGE 2 and HIF-1α pathways have been suggested to favour tumour-promoting inflammation by mechanisms that include direct inhibition of cytotoxic cell infiltration and effector function [ 77 , 78 ]. S-nitrosylation of COX-2, a modification that enhances its catalytic activity, has been found in biopsies from colon and breast cancer patients [ 79 ]. Furthermore, co-expression of iNOS with COX-2 or HIF-1α is extensively reported in histological studies and associates with poor prognosis in several types of cancer [ 7 , 17 ].…”

Reciprocal inflammatory signaling in an ex-vivo explant model for neurofibromatosis type 1-related cutaneous neurofibromas

“…COX2 activity is enhanced by iNOS mediated S-nitrosylation (Kim, Huri et al 2005). We evaluated expression of both S-nitrosylated and non-nitrosylated COX2 by IHC (Jindal, Pennock et al 2020) in CNF PDEs. COX2 expression was highly variable within and between patients, with both S-nitroslyated (Figure 6a) and non-nitrosylated (Figure 6b) forms of COX2 detected to varying degrees in tumor and adjacent tissue.…”

Targeting Nitric Oxide: Say NO to Metastasis

“…Increased production of NO and dysregulated S-nitrosation can influence tumor initiation and metastasis ( 34–38 ). S-nitrosation regulates the enzymatic/catalytic function of critical proteins, thereby influencing the function of signaling pathways such as MAPK, PI3K/Akt, β-catenin, and cytoskeletal processes.…”