ADAM9 drives the immunosuppressive microenvironment by cholesterol biosynthesis-mediated activation of IL6-STAT3 signaling for lung tumor progression.

ABSTRACT

Chronic inflammation associated with lung cancers contributes to immunosuppressive tumor microenvironments, reducing CD8+ T-cell function and leading to poor patient outcomes. A disintegrin and metalloprotease domain 9 (ADAM9) promotes cancer progression. Here, we aim to elucidate the role of ADAM9 in the immunosuppressive tumor microenvironment. A bioinformatic analysis of TIMER2.0 was used to investigate the correlation of ADAM9 and to infiltrate immune cells in the human lung cancer database and mouse lung tumor samples. Flow cytometry, immunohistochemistry, and RNA sequencing (RNA-seq) were performed to investigate the ADAM9-mediated immunosuppressive microenvironment. The coculture system of lung cancer cells with immune cells, cytokine array assays, and proteomic approach was used to investigate the mechanism. By analyzing the human LUAD database and the mouse lung cancer models, we showed that ADAM9 was associated with the immunosuppressive microenvironment. Additionally, ADAM9 released IL6 protein from cancer cells to inhibit IL12p40 secretion from dendritic cells, therefore leading to dendritic cell dysfunction and further affecting T-cell functions. Proteomic analysis indicated that ADAM9 promoted cholesterol biosynthesis and increased IL6-STAT3 signaling. Mechanistically, ADAM9 reduced the protein stability of LDLR, resulting in reduced cholesterol uptake and induced cholesterol biosynthesis. Moreover, LDLR reduction enhanced IL6-STAT3 activation. We reveal that ADAM9 has a novel biological function that drives the immunosuppressive tumor microenvironment by linking lung cancer's metabolic and signaling axes. Thus, by targeting ADAM9 an innovative and promising therapeutic opportunity was indicated for regulating the immunosuppression of lung cancer.