Exploring the protective role of EMILIN-1 in Gastric Cancer: insights into microenvironment modifications and lymphatic function.

Gastric Cancer (GC) is the fifth most common neoplastic malignancy worldwide, whose aggressiveness is significantly influenced by the tumor microenvironment (TME). GC progression is closely related to profound alterations in lymphatic vessels (LVs), with lymphatic metastasis being a pivotal determinant of clinical outcome. Recent research has revealed the functional relationship between the Extra-Cellular Matrix (ECM) protein EMILIN-1, tumor growth, and lymphangiogenesis. EMILIN-1, an essential structural element for maintaining the integrity of the LVs, exhibits anti-proliferative and oncosuppressive properties through interactions with α4β1 integrin. Our study revealed lower EMILIN-1 levels in human malignant and pre-neoplastic gastric samples, which were correlated with the presence of abnormal LVs. Through in vivo experiments with genetically modified EMILIN-1 mouse models (knock-out and E933A knock-in mice), we observed earlier and greater tumor development, and enhanced intratumoral lymphangiogenesis in EMILIN-1 transgenic mice. In a model of peritoneal carcinomatosis and dissemination, mutant animals displayed higher histopathological scores for invasion. Consistent with these results, EMILIN1 transgenic animals showed higher tumor incidence, larger adenomas and lower survival when the N-Methyl-N-nitrosourea protocol for gastric carcinogenesis was performed. In vitro studies using fibroblasts and lymphatic endothelial cells (LECs), both primary sources of EMILIN-1 in the gastric microenvironment, further supported our findings. Indeed, the treatment of stromal cells with conditioned media derived from GC cell lines (but not normal gastric cells) dramatically affected EMILIN1 expression, both at the mRNA and protein levels. In addition, downregulation of EMILIN-1 in LECs impaired their ability to form tubes, indicating an important role of this protein also in maintaining homeostasis of the lymphatic tissue. Preliminary investigations into the mechanisms involved in this complex regulatory network suggest that a candidate for downregulation of EMILIN-1 in small RNAs secreted by GC cells could be identified. Overall, our study demonstrates how loss of EMILIN-1 affects microenvironment changes, including lymphatic dysfunction and proliferative imbalance that contribute to tumorigenesis in the stomach. Importantly, we present a novel animal model targeting an ECM component in the gastric TME, that sheds light on the role of EMILIN-1 in the onset, progression, and spread of GC.