Measurements of Functional Responses in Human Primary Lung Cells as a Basis for Personalized Therapy for Cystic Fibrosis

Abstract

BackgroundThe best investigational drug to treat cystic fibrosis (CF) patients with the most common CF-causing mutation (F508del) is VX-809 (lumacaftor) which recently succeeded in Phase III clinical trial in combination with ivacaftor. This corrector rescues F508del-CFTR from its abnormal intracellular localization to the cell surface, a traffic defect shared by all Class II CFTR mutants. Our goal here is to test the efficacy of lumacaftor in other Class II mutants in primary human bronchial epithelial (HBE) cells derived from CF patients.MethodsThe effect of lumacaftor was investigated in primary HBE cells from non-CF and CF patients with F508del/F508del, A561E/A561E, N1303K/G542X, F508del/G542X and F508del/Y1092X genotypes by measurements of Forskolin plus Genistein-inducible equivalent short-circuit current (Ieq-SC-Fsk + Gen) in perfused open-circuit Ussing chambers. Efficacy of corrector C18 was also assessed on A561E/A561E and F508del/F508del cells.ResultsOur data indicate that A561E (when present in both alleles) responds positively to lumacaftor treatment at equivalent efficacy of F508del in primary HBE cells. Similarly, lumacaftor has a positive impact on Y1092X, but not on N1303K. Our data also show that cells with only one copy of F508del-CFTR respond less to VX-809. Moreover, there is great variability in lumacaftor responses among F508del-homozygous cells from different donors. Compound C18 failed to rescue A561E-CFTR but not in F508del-CFTR, thus plausibly it has a different mechanism of action distinct from lumacaftor.ConclusionsCF patients with A561E (and likely also those with Y1029X) can potentially benefit from lumacaftor. Moreover, the methodology used here exemplifies how ex vivo approaches may apply personalized therapies to CF and possibly other respiratory diseases.

Nasospheroids permit measurements of CFTR-dependent fluid transport

“…Effective therapeutic strategies without understanding the mechanism of defect in hundreds of different rare mutant CFTR alleles appears impossible without a personalized efficacy assay derived from a patient's own cells. This hypothesis is supported by observations that even the latest regimens do not fully restore CFTR activity, and individuals with similar or the same mutations may respond differently (20,(25)(26)(27). Therefore, it is imperative to implement methods to target the therapeutic strategy to the individual, regardless of genotype, genetic context, and environmental background.…”

Transformative therapies for rare CFTR missense alleles

“…Notably, studies conducted in FRT cells have shown p.P67L responds robustly to both compounds, reaching nearly wild-type levels of CFTR activity [24], suggesting that patients would benefit from these drugs. Conversely, the p.N1303K variant is 8 times more common (reported in over 2,000 individuals), but it is unresponsive to VX-770 or VX-809 in FRT cells [23] and primary airway epithelia [25]. Although sufficient numbers of patients may be available for a robust clinical study, preclinical evidence strongly suggests against clinical improvement in this setting.…”

“…Many immortalized mammalian cell lines have proven essential for distinguishing specific features of CFTR biogenesis, as well as mechanisms invoked by investigational compounds [10,28]. Recently, primary human nasal or bronchial epithelia [25,29] and induced pluripotent stem cells [30,31,32] have emerged as strong predictive tools. Organoids generated from patients represent another topical area of progress with the potential to predict individual response to a therapeutic strategy (i.e.…”

Hallmarks of therapeutic management of the cystic fibrosis functional landscape

“…Emerging insights suggest that these links are mismanaged through multiple mechanisms, leading to both the loss and/or gain of aberrant protein interactions 2–4,7,19–21 (Pankow et. al.…”

“…Such cell-based, overexpression models can be useful to detect potential underlying general principles that could be operational within complex proteome networks in the patient, particularly given the very low abundance of CFTR expression in human primary tissue when expressed under control of endogenous promoters. Because CFBE41o-cells clearly do not recapitulate human tissue environments, it will also be essential to explore the role of the PN and SN for different CFR variants in, for example, tissue-derived primary human bronchial epithelial (hBE) cells obtained from CF patients and grown on transwell environments 19 , in organoid cultures derived from rectal and lung biopsy 126 , and/ or in tissue explants.…”