TGF-β1/TβRII/Smad3 signaling pathway promotes VEGF expression in oral squamous cell carcinoma tumor-associated macrophages

Abstract

Oral squamous cell carcinoma (OSCC) is the most common type of malignant cancer affecting the oral cavity. Tumor associated macrophages (TAMs) play a vital role in the initiation, progression and metastasis of OSCC. In this study, we investigated the correlation between macrophages and several clinical and pathological indicators, and we also explored how transforming growth factor-β1 (TGF-β1) effect on VEGF expression in TAMs. Seventy-two paraffin-embedded OSCC samples were collected. Association between macrophages density, micro vascular density (MVD) and clinical-pathological feature were explored by immunohistochemical staining. Western blot, ELISA and qRT-PCR were conducted to assess the VEGF expression in TAMs treated with or without neutralizing TGF-β1, TβRII and smad3 antibodies. Results showed that CD68⁺ macrophages were absent in normal tissues. Macrophages density was directly correlated to low pathological differentiation, late clinical staging and poor survival rate. MVD showed positive correlation with clinical staging and macrophages density. Furthermore, OSCC-associated macrophages expressed more VEGF than macrophages in healthy lymph nodes. However, when TGF-β1 or TβRII were neutralized or the Smad3 was inhibited, VEGF expression was down regulated as well. It is concluded that TGF-β1 could promote OSCC-associated macrophages to secrete more VEGF via TβRII/Smad3 signaling pathway. This result might explain the correlation between macrophages density and worse clinical-pathological condition.

Keywords: Angiogenesis; Macrophages; Oral squamous cell carcinoma; Prognosis; VEGF.