Using a Personalized Medicine Approach to Develop Care for an Atypical Cystic Fibrosis Patient

Authors: Zhang, Weiqiang; LEE, JESUN - Cedars-Sinai Medical Center; HUSAMI, AMMAR - Cincinnati Children'S Research Hospital; KADRI, FERDOUS - Cedars-Sinai Medical Center; YARLAGADDA, SUNITHA - Cincinnati Children'S Research Hospital; MOON, CHANGSUK - Cincinnati Children'S Research Hospital; MUN, KYU SHIK - Cedars-Sinai Medical Center; ZHANG, KEJIAN - Cincinnati Children'S Research Hospital; ARORA, KAVISHA - Cedars-Sinai Medical Center; NAREN, ANJAPARAVANDA - Cedars-Sinai Medical Center; BREWINGTON, JOHN - Cedars-Sinai Medical Center; CLANCY, JOHN - Cincinnati Children'S Research Hospital

Submitted to: Journal of Clinical Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Mutations in the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene could cause severe health complications in many organ systems, including the respiratory and digestive systems. Atypical CF is a mild form of CF disorder associated with various mutations. Due to the uncommon presentation, late onset of symptoms, and unknown/uncharacterized mutations, patients with atypical CF usually cannot get a timely diagnosis or optimal treatment. Using a personalized medicine approach, we developed a treatment plan for an atypical CF patient. Specifically, we (1) isolated the intestinal stem cells from the patient and tested the CFTR channel function in these cells. We found the CFTR channel function was impaired but could be rescued by using some currently available CFTR-modulating drugs; (2) identified three CFTR mutations in this patient, P750L, V470M, and N417K, by using genetic sequencing; (3) used several biomedical methods and identified the defects of these CFTR mutations; and (4) based on these experimental data, conducted a clinical study and successfully improved the patient’s health.

Technical Abstract: Mutations in the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene could cause severe health complications in many organ systems, including the respiratory and digestive systems. Atypical CF is a mild form of CF disorder associated with various mutations. Due to the uncommon presentation, late onset of symptoms, and unknown/uncharacterized mutations, patients with atypical CF usually cannot get a timely diagnosis or optimal treatment. Using a personalized medicine approach, we developed a treatment plan for an atypical CF patient. Specifically, we first tested the CFTR channel activity using the forskolin (FSK)-induced swelling assay in intestinal organoids derived from the patient. We found residual CFTR channel activity in these organoids, and, more importantly, CFTR modulators could significantly augment CFTR channel function. We next used Whole Exome Sequencing (WES) and Variant Analysis to identify her specific mutations. We identified three compound heterozygous mutations: c.2249C>T (p.P750L), c.1408G>A (p.V470M), and c.1251C>A (p.N417K), among which the channel function and nature of defects for both V470M and N417K mutations were not previously characterized. To understand the defects associated with these mutations, we used whole cell patch clamp and Western blotting to study mutant CFTR expression, maturation, and channel function. We found that P750L has the features of Class II CFTR mutations, whereas V470M/N417K exhibits characteristics of Class II, III, and IV mutations. All these mutations responded well to Trikafta® treatment, with channel functions reaching wild-type (WT)-CFTR level. Collectively, our in vitro data correlate with the clinical features of this patient and validate the option of using Trikafta® for her therapy. Indeed, after 18 months of Trikafta® treatment, we observed significant improvement in this patient's symptoms and major clinical parameters. Our study suggests that a personalized medicine approach can be used to care for CF patients with atypical symptoms and/or rare CFTR mutations.