Evidence that systemic gentamicin suppresses premature stop mutations in patients with cystic fibrosis

Here we report the effects of gentamicin treatment on cystic fibrosis trans membrane regulator (CFTR) production and function in CF airway cells and pa tients with CF with premature stop mutations. Using immunocytochemical and functional [6-methoxy-N-(3-sulfopropyl) quinolinium (SPQ)-based] techniques , ex vivo exposure of airway cells from stop mutation CF patients led to th e identification of surface-localized CFTR in a dose-dependent fashion. Nex t, five patients with CF with stop mutations and five CF control subjects w ere treated with parenteral gentamicin for 1 wk, and underwent repeated in vivo measures of CFTR function (nasal potential difference [PD] measurement s and sweat chloride [Cl-] testing). During the treatment period, the numbe r of nasal PD readings in the direction of Cl- secretion was increased appr oximately 3-fold in the stop mutation patient group compared with controls (p < 0.001), and four of five stop mutation patients with CF had at least o ne reading during gentamicin treatment with a Cl- secretory response of mor e than -5 mV (hyperpolarized). A response of this magnitude was not seen in any of the CF control subjects (p < 0.05). In an independent series of exp eriments designed to test the ability of repeat nasal PDs to detect wild-ty pe CFTR function, evidence of Cl- secretion was seen in 88% of control (non -CF) nasal PDs, and 71% were more than -5 mV hyperpolarized. Together, thes e results suggest that gentamicin treatment can suppress premature stop mut ations in airway cells from patients with CF, and produce small increases i n CFTR Cl- conductance (as measured by the nasal PD) in vivo.