Three proteins — complement (C)3, C4A/B, and apolipoprotein (APO)A1 — are worthy of further investigation for their potential involvement in the development of interstitial lung disease (ILD), according to new research. The potential association between ILD and the proteins was identified when the protein profiles of 15 patients with ILD and 64 ILD-free controls were analyzed.

Investigators recruited Japanese patients with non-small-cell lung cancer (NSCLC) who were enrolled in a phase IV study of erlotinib. Serum samples were taken from all participants before the start of erlotinib treatment. Liquid chromatography-mass spectroscopy/mass spectroscopy (LC-MS/MS) was then used to identify proteins and peptides in the serum samples.

No single protein marker was significantly associated with ILD, however when multiple methods of analysis were used, C3, C4A/C4B, and APOA1 appeared within the top 10 markers found among the ILD patients, irrespective of the method of analysis used and irrespective of adjustment for four clinical ILD risk factors.

“There was a tendency for ILD to develop more readily when C3 levels were higher than the median and when C4A/C4B and APOA1 levels were lower than the median,” the authors wrote. “Future research with a focus on these proteins will be significant as a new biological approach for identifying factors predicting the development of ILD.”