However, this proposed mechanism of specific ClC-2-mediated Cl- secretion has proven controversial as a number of conflicting studies have indicated a role for the CFTR chloride channel in the overall ion transport and Cl- secretory response to lubiprostone using human IEC lines, isolated human intestinal tissue and enteroids generated from CFTR knockout mice and cystic fibrosis patients harboring the DF508 mutation that prevents appropriate CFTR trafficking to the epithelial apical membrane [5,6,8,10,11,12,13]. This evidence concerns the gene CFTR and cystic fibrosis.