Systematic pan-cancer analysis identified RASSF1 as an immunological and prognostic biomarker and validated in lung cancer

Background: Ras association domain family member 1 (RASSF1) encodes the RASSF1A protein, serving as a scaffold protein situated at the intersection of a complex signalling network. Aims: To evaluate the immunological and prognostic significance of RASSF1 expression in various types of human cancers, with a specific focus on lung cancer. Methods: Differential expression analysis of RASSF1 was conducted based on data from The Cancer Genome Atlas, Genotype-Tissue Expression, and Cancer Cell Line Encyclopaedia databases. Prognostic analysis was performed using the Cox regression test and Kaplan-Meier test. Spearman's test was utilized for correlation analysis. Gene Ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) gene sets were employed to enrich the associated signaling pathways. Immunohistochemical staining and quantitative real-time PCR were employed to detect protein and mRNA expression levels, respectively. Results: RASSF1 expression was significantly lower in tumour tissues than in normal tissues in most cancers, and Cox regression analysis demonstrated a significant correlation between RASSF1 expression and the prognosis of over 12 types of cancer. Specifically, high RASSF1 expression was associated with poor OS in nine cancer types, including GBMLGG (HR = 4.98, P = 1.2e-31), LGG (HR = 3.72, P = 2.5e-10), and LAML (HR = 1.48, P = 2.4e-3). Further analysis showed that RASSF1 expression was significantly correlated with immune checkpoint- and immune-related genes. Moreover, RASSF1 expression is involved in tumour microenvironment (TME), RNA modification, genomic heterogeneity, and tumour stemness. GO and KEGG analyses showed that RASSF1 was closely related to tumour immune-related pathways. Finally, RASSF1A was moderately correlated with PD-L1 (R = 0.556), and RASSF1A overexpression significantly