S-nitrosylated COX-2 is a microenvironment-regulated breast cancer cell biomarker of mesenchymal phenotypes.

COX-2, an inducible enzyme key to production of inflammatory prostaglandins, has tumor cell-intrinsic oncogenic activity. Previously, we reported Cys-526-nitrosylated COX-2 (SNO-COX-2) associates with breast cancer progression and poor-prognostic young onset breast cancer. Here, using a 3D culture model of early-stage human breast cancer (MCF10DCIS cells), we report SNO-COX-2, but not non-nitrosylated COX-2, closely associated with mesenchymal cell phenotypes induced by fibrillar Col1. Inhibition of nitric oxide synthase (NOS) activity did not reduce SNO-COX-2 levels, suggesting alternative nitrosylation mechanisms. In 3D MCF10DCIS culture, mesenchymal phenotypes and SNO-COX-2 protein induced by Col1 did not associate with transcription of classic epithelial-to-mesenchymal transition (EMT) markers nor common cancer signaling pathways. Conversely, TGFβ-1 strongly induced EMT- and cancer signaling-related transcripts but was insufficient to increase SNO-COX-2 protein or mesenchymal phenotypes. These data suggest the mesenchymal phenotype and SNO-COX-2 expression in MCF10DCIS are driven by a non-transcriptional mechanism dependent on Col1. We tested 300 additional microenvironmental conditions and find SNO-COX-2 expression is driven by inflammatory, wound-resolving, and cancer-associated TME factors, including TNC, SPP1, decorin, Col1, Col3, INF-γ, and IL-4/13, with specific extracellular matrix-ligand combinations driving both high and low SNO-COX-2 expression. In sum, these observations show that in MCF10DCIS cells, SNO-COX-2 associates with mesenchymal phenotypes more strongly than non-nitrosylated COX-2; expression of classic EMT transcripts is neither sufficient nor necessary for acquisition of mesenchymal phenotypes; and expression of SNO-COX-2 is highly microenvironment-dependent. Future studies evaluating SNO-COX-2 as a biomarker for early-stage breast cancer with increased risk for progression, and its regulation, are warranted.