View Abstract

A2838 - Identification of an Uncommon CFTR Mutation that Responds to Correctors
Author Block: C. Cotton1, M. Rezaee1, M. Wilson1, A. Parsons2, J. Chmiel2; 1Pediatrics, Case Western Reserve University, Cleveland, OH, United States, 2Rainbow Babies and Childrens Hosp, Cleveland, OH, United States.
Primary human airway epithelial cell cultures maintained at air/liquid interface (ALI) are an important model system for preclinical testing of CFTR modulators. Human bronchial epithelial (HBE) cells obtained from transplanted CF lungs were used extensively in the development of VX-770 (Ivacaftor) and VX-809 (Lumacaftor) as modulators to improve gating (G551D; F508del) and trafficking (F508del) of mutant CFTR. Cells obtained from transplanted CF lungs are limited and do not represent the full spectrum of CFTR mutations. Patient-derived nasal epithelial (HNE) cells overcome these limitations and are an important resource for studying uncommon CFTR mutations. We tested primary HNE cell cultures derived from CF subjects and identified a Class II trafficking mutation, L138ins, that responds to CFTR correctors. HNE cells were collected from a CF subject who is a CFTR compound heterozygote (F508del/L138ins). The subject is a 25 year old female with a sweat Cl = 53 mEq/L, pancreatic sufficient, and FEV1 = 56% predicted. Primary HNE cells from 19 non-CF subjects and 23 CF subjects homozygous for F508del were also collected and tested. Cells were expanded and seeded onto permeable supports, maintained as ALI cultures, and transepithelial electrophysiology was used to assess CFTR function. Primary HNE cultures from non-CF subjects exhibited large amiloride-sensitive sodium current and cAMP-stimulated, I172-sensitive CFTR current of ~15 uA/cm2. The CFTR Cl current in non-CF HNE cells was insensitive to CFTR modulators (potentiator, VX-770; and corrector, VX-809). Primary HNE ALI cultures derived from F508del homozygous subjects had large amiloride-sensitve sodium current, but the cAMP-stimulated, I172-sensitive Cl current was small (~6% of non-CF). Treatment of F508del homozygous ALI cultures with VX-809 increased CFTR current by ~3-fold (~18% of non-CF). Cultures derived from the F508del/L138ins subject exhibited large amiloride-sensitive sodium current and intermediate cAMP-stimulated, I172-sensitive Cl current (~15% of non-CF). Treatment with VX-809 increased the I172-sensitive Cl current ~4.5-fold (~67% of non-CF). Interestingly, acute addition of a CFTR potentiator (VX-770) increased F508del CFTR currents, but caused only a small additional increase in F508del/L138ins CFTR current. These data suggest that most of the residual CFTR function (intermediate sweat Cl and pancreatic sufficient) is contributed by the L138ins CFTR, but the relatively poor lung function (FEV1 56 %predicted) indicates that this level of CFTR function is not sufficient to prevent lung disease. Our findings support the use of CFTR corrector therapy in CF patients who carry the L138ins CFTR mutation with or without F508del. (Supported by NIH-2R44HL134012-02, NIH-1P01 HL128192-01A1, CFFT COTTON14XX0)