The Role of MATN3 in Cancer Prognosis and Immune Infiltration Across Multiple Tumor Types

<b>Background:</b> MATN3 is a member of the matrix protein family and is involved in the regulation of osteoarthritis as well as the development of gastric cancer. We investigated the role of MATN3 in pan-cancer and validated this result by <i>in vitro</i> experiments. <b>Material and Methods:</b> We applied multiple databases to explore the expression of MATN3 in 33 types of tumors. Kaplan-Meier survival analysis is performed to understand the effect of MATN3 on Prognostic value in patients with different cancer types. The TIMER database was applied to explore the relationship between MATN3 and immune checkpoint genes, immunomodulatory genes, and immune infiltration, the Sanger box was applied to explore the relationship between MATN3 and methylation, the Genomic Cancer Analysis database was utilized to explore the relationship between MATN3 expression and pharmacological sensitivity, and the STRING database was used to explore the co-expressed genes and to complete the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Data from The Cancer Genome Atlas as well as Genotype-Tissue Expression databases were statistically analyzed and visualized using the R software. Immunohistochemistry and Western blotting for detection of MATN3 expression. CCK-8 and clone formation were used to detect cell proliferation, Wound-healing assay and transwell invasion were used to detect cell migration and invasion ability. <b>Results:</b> MATN3 is overexpressed in most cancer types, indicating a poorer prognosis. It is closely linked to methylation, immunomodulatory genes, and immune checkpoint genes, contributing to immune infiltration in various cancer types. <i>In vitro</i> experiments showed that silencing MATN3 inhibited cell proliferation, migration, and invasion ability. <b>Conclusions:</b> MATN3 is involved in the immune infiltration of cancer and affects the prognosis of many cancer types, and can be used as an immune as well as prognostic biomarker for pan-cancer.