PROJECT SUMMARY Scleroderma (SSc) patients have more than a 300% increased risk of lung cancer, or Cancerous Scleroderma (CSc). SSc is a chronic autoimmune connective tissue disease of unknown etiology, and has the highest morbidity of all rheumatologic diseases. Moreover, aging is a key risk factor in SSc patients for pathological airway remodeling or idiopathic pulmonary fibrosis (IPF), the leading cause of death in SSc patients. Intriguingly, aging is associated with increased senescent cells, likely contributing to increased fibrosis. Published reports show that fibroblasts from IPF patients are senescent and produce a pro-tumorigenic senescence associated secretory phenotype (SASP), suggesting a potential key role for senescent myofibroblasts, the key cell type responsible for fibrosis, in driving the pathogenesis of CSc. Although it is evident that there is a tight link between fibrosis and cancer in CSc, the directionality of this progression and molecular circuits linking the two are unknown. Published data by our lab show that the TNF superfamily member 14, LIGHT, signals through LTβR expressed on myofibroblasts to drive collagen deposition and α-smooth muscle actin hypertrophy – the hallmarks of fibrosis. Our novel preliminary data suggests that senescent myofibroblasts drive cancer in a LIGHT dependent manner: In gain-of-function studies, intratracheal (I.T.) LIGHT led to enhanced fibrosis and senescent myofibroblasts in aged mice, while in loss-of-function studies comparing aged to young mice given lung adenocarcinoma cells I.T., LIGHT deletion abrogated cancer engraftment in aged mice, while young WT and LIGHT-/- mice were protected from cancer engraftment. Additionally, in a mouse lung organoid system, we showed that senescent myofibroblasts expressing LTβR increase tumor growth. Therefore, we hypothesize that senescent myofibroblasts are responsible for driving pulmonary fibrosis in scleroderma and promote lung cancer through expression of a SASP. Notably, in a novel model we established of CSc, LIGHT deletion decreased fibrosis, cancer engraftment, and senescent myofibroblasts. One key question is how LIGHT affects senescent myofibroblasts to drive cancer, therefore we will address this through the following Specific Aims: 1) To identify the molecular circuits that LIGHT uses to drive cancerous scleroderma and 2) To directly investigate the role of senescent myofibroblasts in promoting cancer ex vivo. For aim 1, we will modulate LIGHT signaling and fibrosis in mice and induce our novel model of CSc, monitoring disease. For aim 2, we will use RNA-sequencing and human lung organoids to identify the molecular pathways that drive CSc downstream of LIGHT in senescent myofibroblasts to translate findings from mouse to human. The research described in aim 1 will provide an understanding as to how LIGHT signaling drives CSc pathogenesis, while the research described in aim 2 will establish the role of senescent myofibroblasts as the key p...