RENCA/carbonic anhydrase-IX: A murine model of a carbonic anhydrase-IX-expressing renal cell carcinoma

<bold>Objectives: </bold>Carbonic anhydrase-IX (CA-IX) is a cell surface tumor-associated antigen expressed by most clear cell renal cell carcinomas (RCCs). The specificity and the prognostic value of CA-IX provide impetus to create a mouse model of CA-IX-expressing RCC for testing CA-IX-targeted therapies against RCC. <bold>Methods: </bold>A retrovirus encoding the human CA-IX gene was used to transduce the murine RCC line, RENCA. In vivo growth kinetics and CA-IX expression were compared between RENCA and RENCA/CA-IX using heterotopic, metastatic, and orthotopic models. <bold>Results: </bold>Transduction of RENCA created the RENCA/CA-IX line with nearly 100% CA-IX surface expression. In the heterotopic model, subcutaneous injection of 500,000 and 50,000 cells led to tumor formation at 2 to 2.5 weeks after injection, with similar growth kinetics between the two cell lines at either cell number. In the pulmonary metastatic model, a similar number of metastases was noted after inoculation of RENCA and RENCA/CA-IX. In the orthotopic model, autopsy revealed a CA-IX-expressing renal tumor, as well as CA-IX-expressing metastases to the lungs, liver, contralateral kidney, intestines, and lymph nodes. In all the above models, the RENCA/CA-IX tumors retained expression of CA-IX, as demonstrated by immunohistochemistry staining. <bold>Conclusions: </bold>RENCA/CA-IX is the first tumor model that manifests in immunocompetent Balb/c mice and stably expresses a defined kidney cancer-associated antigen. It maintains antigen expression, forms metastases, and produces reliable tumor growth kinetics equivalent to that of its parental cell line. [ABSTRACT FROM AUTHOR]