Carbonic anhydrase IX (CA IX) mediates tumor cell interactions with microenvironment.

Expression of CA IX is normally restricted to the mucosa of alimentary tract, but on the other hand, it takes place in a high percentage of human cancers derived from tissues which are normally CA IX-negative. It is a transmembrane protein with two extracellular domains: carbonic anhydrase (CA) with a high catalytic activity and a proteoglycan-like segment (PG), mediating cell-cell adhesion. Both CA and PG domains interact with the microenvironment and they could play a role in tumorigenesis, but their roles are poorly understood.

Gastric hyperplasia in mice with targeted disruption of the carbonic anhydrase gene Car9.

Background & Aims: Carbonic anhydrase (CA) IX is a highly active enzyme with adhesion capacity that is functionally implicated in acid-base balance and intercellular communication. It is normally present in basolateral membranes of gastrointestinal epithelial cells and ectopically expressed in various carcinomas. To show its physiologic relevance, we have cloned the Car9 gene and generated CA IX-deficient mice.