The increased number of tumor-associated macrophage is associated with overexpression of VEGF-C, plays an important role in Kazakh ESCC invasion and metastasis

Abstract

Tumor associated macrophages (TAMs) play an important role in the growth, progression, and metastasis of tumors. The distribution of TAMs in Kazakh esophageal squamous cell carcinoma (ESCC) is not determined. We aimed to investigate the role of TAMs in the occurrence and progression of Kazakh ESCC. CD163 was used as the TAM marker, and immunohistochemistry (IHC) counts were used to quantify the density of TAMs in tumor nest and surrounding stroma. IHC staining was used to evaluate the expression of vascular endothelial growth factor C (VEGF-C) in Kazakh ESCC and cancer adjacent normal (CAN) tissues. The density of TAMs in Kazakh ESCCs tumor nest and stromal was significantly higher than that in CAN tissues. The increased number of CD163-positive TAMs in tumor nest and tumor stromal was positively associated with Kazakh ESCC lymph node metastasis and clinical stage progression. Meanwhile, the expression of VEGF-C in Kazakh ESCCs was significantly higher than that in CAN tissues. Overexpression of VEGF-C in Kazakh ESCCs was significantly associated with gender, depth of tumor invasion, lymph node metastasis and tumor clinical stage. The increased number of TAMs, either in the tumor nests or tumor stroma was positively correlated with the overexpression of VEGF-C, which may promote lymphangiogenesis and play an important role in the invasion and metastasis of Kazakh ESCC.

Introduction

Esophageal carcinoma is one of the 10 most common malignant tumors worldwide. Incidence rates vary between physiographic regions, nations, and races (Parkin et al., 2005). China has high esophageal carcinoma incidence and mortality rates (Chen et al., 2013). The Kazakh national minority (ethnic) living in Xinjiang (northwest of China) is demographic with one of the highest rates of esophageal carcinoma incidence and mortality, its esophageal carcinoma mortality rate has reached 155.9/100,000, which is higher than the average Chinese rate of 15.23/100000 (Zhang, 1988). The 5-year survival rate of esophageal carcinoma is only 10%. Primary reasons for poor prognosis are associated with early stage cancer cell invasion and high metastasis (Ekman et al., 2008).

The tumor microenvironment is important for cancer development and metastasis (Lee et al., 2014, Zhang et al., 2011). It contains a range of inflammatory and immune cells. Macrophages (MØ) are essential immune cells that play a critical role in carcinogenesis and tumor progression (Gwak et al., 2015). Similar to Th1 and Th2 T cells, MØ can be classified into M1 and M2 subtypes (Biswas and Mantovani, 2010). M1 MØ are activated by interferon gamma (IFN-γ) and microorganisms, expressing high levels of proinflammatory cytokines (tumor necrosis factor alpha [TNF-α], interleukin [IL]-6, IL-12) and major histocompatibility complex class II (MHC class II). M1 MØ are capable of killing pathogens and promoting antitumor immune responses. By contrast, M2 MØ are activated in vitro by IL-4, IL-10 and IL-13, showing reduced MHC class II and IL-12 expression, but increased expression of IL-10 and arginase (Mantovani and Sica, 2010). Most M2 MØ are considered as tumor associated MØ (TAM) and have the effect of promoting tumor angiogenesis, lymphangiogenesis and metastasis (Sica et al., 2008). CD163 is a confirmed biomarker of the M2 TAMs that can be used to distinguish M2 from M1 MØ. Vascular endothelial growth factor (VEGF) is an important regulator of the progression of pathological angiogenesis and lymphangiogenesis observed in many different tumors (Eveno and Pocard, 2012, Goel and Mercurio, 2013). VEGF-C is a member of VEGFs family, playing an important role in lymphangiogenesis, which it acts on lymphatic endothelial cells (LECs) primarily via its receptor VEGFR-3, promoting survival, growth and migration (Oh et al., 1997). In addition to its effect on lymphatic vessels, it can also promote the growth of blood vessels and regulate their permeability. TAMs produce many proangiogenic factors and express high levels of VEGF-C, which promotes cancer cell invasion, metastasis, angiogenesis and lymphangiogenesis (Obeid et al., 2013, Skobe et al., 2001). However, the precise role of TAMs in Kazakh esophageal squamous cell carcinoma (ESCC) has yet to be elucidated. We aimed to investigate whether TAMs correlate with VEGF-C levels, promoting the occurrence and progression of Kazakh ESCC.