Low expression of INHB co-receptor TGFBR3 in connection with metastasis and immune infiltration in lung adenocarcinoma.

Objective: Inhibin B (INHB) is one of the TGF-β superfamily member, consisting of α (INHA) and βB (INHBB) subunits. Studies have found that TGF-β receptor 3 (TGFBR3) binds to a convex α subunit on the surface of INHB, and enhances the binding affinity of activin receptor type-2 (ACVR2A/B) to INHβ subunit. This study tried to evaluate the roles of INHB subunits and its receptors (INHA, ACVR2A, ACVR2B, INHBB, TGFBR3) as prognostic biomarkers and therapeutic targets for the effective treatment of lung adenocarcinoma (LUAD).

Methods: We analyzed INHB subunits and its receptors' expression and the influence of LUAD from Oncomine, GEPIA, HCMDB, CancerSEA, TIMER databases and so on. Then, 41 cases of cancer tissue and 41 cases of adjacent epithelium were detected in LUAD patients by immunohistochemistry.

Results: INHA, ACVR2A, ACVR2B, INHBB were up-regulated while TGFBR3 was down-regulated in LUAD. INHA, ACVR2A and TGFBR3 were found to be strongly associated with high-grade malignancies and advanced TNM, only TGFBR3 expression was negatively correlated with LUAD metastasis probably mainly through cell adhesion molecules and the PI3K-Akt signaling pathway, univariate and multivariate analysis suggested that overall survival was lower in LUAD cases with low TGFBR3 levels. Further analysis revealed that low TGFBR3 expression was related to reduced infiltration of immune cells into the LUAD, promoting metastasis of LUAD cells. TGFBR3 expression negatively correlates with lymphatic metastasis and clinical stage in patients with LUAD.

Conclusion: TGFBR3 could be a potential new metastatic biomarker for LUAD, with potential application as a prognostic marker and for immunotherapy of LUAD.