Carbonic Anhydrase Expression in TNBC Breast Cancer Cells and Human Tumor Grafts

Abstract

Carbonic anhydrase IX (CAIX) has emerged as a potential target for triple negative breast cancer (TNBC). Our goal is to utilize the tumor graft model to demonstrate the efficacy of carbonic anhydrase (CA) inhibitors in reducing tumor load and metastasis. Here, we compare the expression of CAIX in TNBC human breast cancer cell lines with a bank of tumor tissues generated from subject‐derived breast tumor grafts in mice that retain characteristics of the original patient samples (Dr. Alana Welm). In our sampling of TNBC cell lines, CAIX expression was observed in four of the five lines. Two showed exclusive expression of CAIX relative to other cell surface CA family members, allowing us to evaluate catalytic activity. We observed that CAIX activity, measured by 18O exchange between H216O and H13C18O3−, was related to the level of CAIX expressed and inhibited by an impermeant sulfonamide (N‐3500). We then analyzed CAIX expression in tumor‐grafted tissue. Thirteen samples were available and represented the three major breast cancer phenotypes: estrogen and progesterone receptor‐positive (ER/PR), HER2‐positive, and TNBC. Of the six TNBC tissues, four expressed CAIX. No carbonic anhydrase XII (CAXII) was observed. Cryogenically preserved TNBC tissue was used to develop orthotopic tumors in nude mice. Immunohistochemistry showed high mitotic activity with CAIX expression adjacent to necrotic tissue. The tissue was negative for ER/PR and CAXII. These observations demonstrate that the tumor graft model will be useful in evaluating the efficacy of CA inhibitors for potential clinical use. We gratefully acknowledge funding from NIH (GM25253‐DNS and CA165284‐SCF), the UF Cancer Center (SCF), and the CSCRB, Inc (SCF).