Marc Terrones ^1,2 Ken Op de Beeck ^1,2 Guy Van Camp ^1,2 Geert Vandeweyer ^1,3* Ligia Mateiu ¹

• ¹ Center for Medical Genetics, Faculty of Medicine and Health Sciences, University of Antwerp, Edegem, Belgium
• ² Center for Oncological Research, Faculty of Medicine and Health Sciences, University of Antwerp, Wilrijk, Antwerp, Belgium
• ³ Antwerp University Hospital, Antwerp, Antwerp, Belgium

Introduction: The transcriptomic characteristics of ROS1+ non-small cell lung cancer (NSCLC) represent a crucial aspect of its tumor biology. These features provide valuable insights into key dysregulated pathways, potentially leading to the discovery of novel targetable alterations or biomarkers. Methods: From The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) databases, all available ROS1+ (n = 10), ALK+ (n = 5) and RET+ (n = 5) NSCLC tumor and ROS1+ cell line (n = 7) RNA-sequencing files were collected. In addition, 10 healthy lung RNA-seq samples were included. Differential gene expression with DESeq2 (R package) and gene co-expression (WGCNA, R package) analyses were performed. Functional annotation was performed through Gene Set Enrichment Analysis (GSEA) using Webgestalt and RNAseqChef, Over-Representation Analysis (ORA) through Enrichr. iRegulon was used to identify enriched transcription factors that regulate a gene co-expression module. Results: ROS1+ NSCLC samples were significantly enriched for the nucleotide synthesis and cell adhesion KEGG pathways compared to ALK+ and RET+ samples. Moreover, NOTCH1 was significantly downregulated in ROS1+ NSCLC and PD-L1 was weakly expressed. When comparing ROS1+ tumor versus cell line transcriptomes, an upregulation of MYC and MET was found in cell lines together with a significantly decreased expression of HER3, HER4 and BRAF. Within ROS1-tumors, GJB2 was overexpressed in the CD74- and CLTC-ROS1+ subgroups. The differential expression of IL20RB and GJB2 in cell lines was confirmed through RT-qPCR. Finally, the gene co-expression analysis unveils a gene cluster involving cell cycle-related genes which significantly correlates with the disease stage of patients. In addition, we propose TDFPI and ISL1 as key ROS1-specific transcription factors. Conclusion: This study highlights cell adhesion and nucleotide synthesis as crucial signatures in ROS1+ NSCLC. The upregulation of GJB2 may serve as a prognostic biomarker, along with IL20RB, a known mediator of bone metastases. Furthermore, TDFP1 and ISL1 were identified as relevant transcription factors that could potentially regulate the biological processes in ROS1-rearranged NSCLC.