CA9 and neoplasm: As shown here, the effect and role of CA IX has been reported in different tumour settings and, even if the in vivo data clearly reveal the key role of these proteins in tumour progression, resistance to therapy and promotion of tumour invasion, extensive in vitro data showed that CA IX inhibition may affect tumour cell survival and proliferation27 and/or motility and invasion28, dependently on the tumour cell type.