Liquid biopsy, which allows the isolation of circulating cell-free (ccf)
DNA from blood, is an emerging noninvasive tool widely used in oncology for diagnostic and prognosis purposes. Previous data have shown that serum
cfDNA discriminates
idiopathic pulmonary fibrosis (IPF) from other
interstitial lung diseases. Our study aimed to measure plasma levels of ccfDNA in 59 consecutive
therapy-naive and clinically stable IPF patients. The single nucleotide polymorphism (SNP) of the MUC5B gene promoter (rs35705950), associated with increased susceptibility of developing IPF, has been sought in plasma
cfDNA and genomic
DNA for comparison. Thirty-five age- and sex-matched healthy volunteers were recruited as the control group. Our results show that concentrations of small-size ccfDNA fragments were significantly higher in IPF patients than in controls and inversely correlated with lung function deterioration. Moreover, the median level of 104 ng/mL allowed discriminating patients with mild disease from those more advanced. The rs35705950 polymorphism was found in 11.8% of IPF patients and 8% of controls, with no differences. Complete concordance between ccfDNA and genomic
DNA was detected in all control samples, while four out of seven IPF cases (57%) carrying the rs35705950 polymorphism were discordant from genomic
DNA (7% of total IPF). Liquid biopsy is a suitable tool with optimistic expectations of application in the field of IPF. In analogy with
cancer biology, finding some discrepancies between ccfDNA and genomic
DNA in IPF patients suggests that the former may convey specific genetic information present in the primary site of the disease.