Evaluation of carbonic anhydrase IX (CA IX) expression in ovarian cancer xenografts treated with anti-VEGF and CA IX inhibitor by digital pathology

Ovarian cancer is one of the most common malignancies among all types of gynecologic cancers with heterogeneous pathogenesis. Generally, the microenvironment condition of the tumor is a crucial factor in solid cancer progression, in particular angiogenesis which is required to supply nutrients and oxygen in tumor cells. One of the most important activators of angiogenesis is vascular endothelial growth factor (VEGF) which is inhibited by bevacizumab, a monoclonal antibody-based biopharmaceutical agent. However, improvements in the therapeutic approach are required to overcome the resistance that frequently occurs. Hypoxia condition in tumor cells alters the expression pattern of some genes such as carbonic anhydrase IX (CAIX). CAIX is a transmembrane protein, which hydrates the CO2 to bicarbonate ion and the proton and plays a critical role in the pro-survival machinery required by hypoxic tumor cells. CAIX modulates cancer progression in various aspects involved in tumorigenesis like acidification of extracellular pH, loss of cellular adhesion, increased tumor cell migration, metastasis, and tumor invasiveness. Moreover, CAIX expression has been correlated with poor prognosis in several tumor types and with worse clinical outcomes in bevacizumab-treated patients. These findings suggest that CAIX is one strategy of hypoxic adaptation and may contribute to an angiogenesis-independent mechanism of resistance to Bevacizumab treatment. This study aims to evaluate CAIX inhibition as a strategy to potentiate the therapeutic efficacy of Bevacizumab in the treatment of ovarian cancer. In vitro study evaluated to find the ovarian cell lines which express CAIX under the hypoxia condition and viability test to assess CAIX expression as a mechanism of hypoxic adaptation with CA IX inhibitor (SLC-1110). Combinational treatment with Bevacizumab and CA IX inhibitor were assessed in vivo study in xenograft tumor mouse model to quantify the CA IX, angiogenesis, and necrosis under this condition. Digital pathology as a powerful analytical tool was used for the quantification of the biomarkers and the result showed a significant increase of CAIX under the bevacizumab tumor treatment.