To identify extracellular matrix molecules secreted by CAFs, we reanalyzed the proteomic profiling results using less strict criteria (G-test > 1.65) and identified multiple collagen isoforms (Col1a2, Col5a1, and Col5a3) that were secreted more abundantly by CAFs than LFs; this finding was validated by confocal microscopic analysis of a human lung adenocarcinoma, which showed papillary tumor structures surrounded by collagenous stroma containing αSMA+ cells (Fig. 7). Here, COL1A2 is linked to lung adenocarcinoma.