IGFBP6 and cystic fibrosis: To further investigate the effect of IGFBP-6 in the CF context, we treated the F508del-CFTR CFBE cells with IGFBP-6 (from 0.2 to 200 ng/ml) for 24 h and we then measured the mRNA IGFBP-6 level by qRT-PCR.