Identification of GREM-1 and GAS6 as Specific Biomarkers for Cancer-Associated Fibroblasts Derived from Patients with Non-Small-Cell Lung Cancer

<b>Background/Objectives:</b> Cancer-associated fibroblasts (CAFs) play a pivotal role in the tumor microenvironment. We conducted an analysis using RNA sequencing to identify specific markers for CAFs compared to normal fibroblasts (NFs) in non-small-cell carcinoma (NSCLC). <b>Methods:</b> CAFs and NFs were isolated and cultured from tumor tissues (primary tumor or metastatic lymph nodes) and matched non-tumor tissues, respectively. Bulk RNA sequencing was conducted on isolated CAFs and normal fibroblast NFs. Differential expressions, gene set enrichment, and CAF subpopulation prediction analyses were performed. <b>Results:</b> During the study period, 27 CAFs and 12 NFs were isolated and cultured from tumor and non-tumor tissues in patients with treatment-naïve NSCLC. Among them, 22 CAFs and 11 NFs were included in the RNA sequencing analysis. The 22 CAF samples consisted of 12 adenocarcinomas and 10 squamous cell carcinomas (SqCC), with 16 samples from the lungs and 6 samples from the lymph nodes. Notably, <i>COL11A1</i>, <i>GREM1</i>, <i>CD36</i>, and <i>GAS6</i> showed a higher expression in CAFs than in NFs, whereas <i>TNC</i> and <i>CXCL2</i> were more abundantly expressed in NFs. <i>CD36</i> levels were elevated in CAFs from lymph nodes (LN-CAFs) compared with those from lung specimens (Lung-CAFs) and NFs. <i>COL11A1</i> levels in Lung-CAFs surpassed those in LN-CAFs and NFs. Both <i>GREM1</i> and <i>GAS6</i> showed a strong expression in Lung-CAFs and LN-CAFs relative to NFs. CAFs exhibited features of the myofibroblast CAF subpopulation, whereas NFs displayed traits of the antigen-presenting CAF subtype. In the co-culture model of CAFs and THP-1 cells, the knockdown of <i>GREM1</i> or <i>GAS6</i> in CAFs significantly decreased the M2 marker expression in macrophages. <b>Conclusions:</b> In NSCLC, <i>GREM1</i> and <i>GAS6</i> can be valuable diagnostic targets for CAFs from primary tumors and metastatic sites; they warrant further study.