Inhibitory Effects of Circulating Natural Autoantibodies to CD47-derived Peptides on Oral Squamous Cell Carcinoma Cells

Abstract

Background Natural autoantibodies serve as an important anti-tumorigenic system due to its immune surveillance function. The present study aims to investigate whether circulating natural IgG autoantibodies against cluster of differentiation 47 (CD47) could inhibit the proliferation of oral squamous cell carcinoma (OSCC) cells. Methods The expression of 14 tumor-targeted genes in three OSCC cell lines was analyzed with quantitative real-time PCR. The in-house enzyme-linked immunosorbent assay (ELISA) was then performed to detect plasma IgG antibodies against CD47. Three OSCC cell lines were treated with 20% human plasma positive and negative for anti-CD47 IgG, respectively, followed by analysis of cell proliferation, apoptosis and invasion/metastasis. Results CD 47 showed highest expression among all 14 genes detected in three OSCC cell lines. Plasma anti-CD47 IgG significantly inhibited the viability of all three OSCC cell lines. The proportions of apoptotic cells were remarkably higher in OSCC cells treated with anti-CD47 IgG-positive plasma than those treated with IgG-negative plasma. Furthermore, the cell invasion/metastasis was attenuated evidently with the attribution of plasma anti-CD47 IgG. Conclusions Natural autoantibodies against CD47 may be a potential target for OSCC immunotherapy.