Variation in LINE-1 ORF1p expression across histologic and demographic subgroups in non-small cell lung cancers.

Aberrant activation of Long Interspersed Element-1 (LINE-1) retrotransposons and their encoded proteins has been linked to poor clinical outcomes across multiple malignancies, including non-small cell lung cancers (NSCLC). In this study, we profiled LINE-1 ORF1p expression and its co-localization with immune cells using multiplex immunofluorescence of NSCLC tumors and matched adjacent non-tumor tissues (N = 76). These data were then integrated with clinicopathologic features to assess the potential clinical utility of such measurements. ORF1p expression was significantly elevated in NSCLC compared to non-tumor lung tissues, with higher levels in lung squamous cell carcinoma (LSQCC) than in lung adenocarcinoma (LUAD). Race-stratified analyses showed markedly higher ORF1p levels in African American compared with Caucasian American patients. Although sex-based differences were less consistent, older males exhibited significantly higher ORF1p levels than other subgroups. Age-stratified analyses revealed a positive correlation between ORF1p and increasing age in tumor samples. Co-expression analyses combined with cellular neighborhood enrichment and spatial auto-correlation analyses demonstrated that ORF1p was most strongly associated with CD68⁺ macrophages across both tumor subtypes and representing the most reliably enriched immune cell population in the immediate spatial vicinity of tumor cells with high ORF1p expression. These findings indicate that LINE-1 ORF1p expression in NSCLC is shaped by tumor histology, race, and age, and may be influenced by macrophage-LINE-1 interactions within the tumor microenvironment.