Abstract 2906: Inducing and disabling COX-2 S-nitrosylation to investigate its role in breast cancer progression

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Abstract Background: We aim to assess the effect of S-nitrosylation of COX-2 on tumor attributes in models of early breast cancer. COX-2 is involved in tumor progression in many solid cancers. It is a known oncogene in murine breast cancer models, and targetable by NSAIDs. In women, its clinical correlation to breast cancer progression as well as its efficacy as a therapeutic target have yielded mixed results. These incongruities may be due, in part, to a post-translational modification, as COX-2 undergoes S-nitrosylation on Cys-526. Commercially-available antibodies selectively bind to either the S-nitrosylated (SNO-COX-2) or non-nitrosylated (nCOX-2) forms, and immunohistochemical staining of human tissue reveals that the two forms of COX-2 localize to different cellular sites in normal breast tissue and have opposite associations with breast cancer progression (PMID 33298921). Hypothesis: S-Nitrosylated and non-nitrosylated COX-2 have distinct roles in cancer progression. Approach: MCF10DCIS.com is a human breast cancer cell line chosen due to its ability to form DCIS-like (“stage 0”) lesions in culture and xenografting, which can progress to invasion when induced by signals from the tumor microenvironment (TME). Approach 1: Detect extracellular matrix (ECM) and ligand factors that upregulate SNO-COX-2, independently or in ECM/ligand pairs. We utilized a 2D microenvironment microarray (MEMA) and tested 357 TME conditions. Approach 2: Validate TME conditions in 3D culture. Approach 3: Develop a mutant MCF10DCIS.com line in which COX-2 cannot be S-nitrosylated by inducing a single disabling missense mutation at Cys-526 via CRISPR. Results: The MEMA revealed several conditions in which SNO-COX-2 was upregulated, including fibular collagens and SSP1. In 3D culture, increased SNO-COX-2 was associated with the presence of markers for EMT and an invasive growth phenotype, whereas nCOX-2 was not. Following CRISPR transformation, 59 individual MCF10DCIS.com clones were isolated and the target site of each sequenced. We identified 10 heterozygotic clones with the desired mutation, including a classical heterozygote that also retained the WT allele. Ongoing: Current studies include a second round of CRISPR to produce a homozygous mutant cell line as well as validation of the mutant protein. The resulting cell lines will model the loss of COX-2 S-nitrosylation in breast cancer cells while retaining otherwise-functional COX-2. Citation Format: Reuben J. Hoffmann, AeSoon Bensen, Elise de Wilde, James E. Korkola, Pepper Schedin. Inducing and disabling COX-2 S-nitrosylation to investigate its role in breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2906.

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