BTNL9 Govern the Malignant Phenotypes of Osteosarcoma Cells by Collaborating with RHOB to Block the PI3K/Akt Signaling Pathway

Abstract

Introduction: Whole transcriptome analysis found substantial variations in butyrophilin-like 9 (BTNL9) expression between osteosarcoma (OS) and healthy bone tissues. The biological involvement of BTNL9 in the physiological regulation of OS cells and its underlying mechanism were investigated herein. Methods: Cell proliferation, colony formation, apoptosis, migration, invasion, and angiogenesis were evaluated to determine the influence of BTNL9 on the malignant phenotypes of OS cells. Given that the STRING (https://string-db.org/) database analysis indicated a potential association between BTNL9 and ras homolog family member B (RHOB), co-immunoprecipitation (Co-IP) was performed to confirm their relationship. To verify the role of RHOB, it was knocked down, and the impacts on the above aspects, as well as the phosphatidylinositol-3-kinase/AKT serine/threonine kinase (PI3K/Akt) signaling pathway, were evaluated. Results: BTNL9 plays a negative role in OS cells, manifested as inhibition of cell proliferation, colony formation, migration, invasion and angiogenesis and promotion of apoptosis. Co-IP results demonstrated a direct association between BTNL9 and RHOB. RHOB knockdown partially reversed the regulatory effect of BTNL9 on the malignant phenotypes of OS cells and the PI3K/Akt signaling pathway. Conclusion: This study highlights that BTNL9 acts as a tumor suppressor in OS and alleviates several malignant phenotypes. BTNL9 collaborates with the recognized tumor suppressor RHOB to block the PI3K/Akt signaling pathway, which is one of the regulatory mechanisms.