CA9 and cancer: This study provides useful information pertaining to the tagging ability of cG250 to the cancer cells, which gives two advantages: (1) the radioactively labeled cG250 would bind to and tag cancer cells exhibiting high CA IX expression and thus elicit an immune response against the tumor cells, which can consequently destroy them; (2) the cG250 antibody may also be tagged with chemotherapeutic drugs or radioactive agents, which can deliver different therapeutic payloads to tumor cells through receptor mediated internalization.