The protein encoded by Chloride channel accessory 2 (CLCA2) gene, on chromosome 1, belongs to the calcium sensitive chloride conductance protein family. Since this protein is expressed predominantly in trachea and lung, it is suggested to play a role in the complex pathogenesis of cystic fibrosis. It may also serve as adhesion molecule for lung metastatic cancer cells, mediating vascular arrest and colonization, and furthermore, it has beenimplicated to act as a tumor suppressor gene for breast cancer. The gene discussed is CLCA2; the disease is cystic fibrosis.