Abstract 471: M2 macrophages promotes tumor growth and invasion in hepatocellular carcinoma
Authors: Yeung Wai Ho , Lee Kin Wah , Geng Wei , Li Chang Xian , Ng Tak Pan , Lo Chung Mau , Guan Xin Yuan , Poon Tung Ping , Fan Sheung Tat , Man Kwan 
Published: June 2012

Background and Aim: The alternative activated (M2) phenotypes with pro-tumor properties of tumor associated macrophages (TAM) have been demonstrated in many cancers except hepatocellular carcinoma (HCC), which is the fifth most frequent malignancy worldwide with high mortality and recurrence rate. Understanding the properties and functions of TAM is essential for prognostic and therapeutic improvement of HCC. In this study, we intend to investigate the role of macrophage on tumor progress of HCC.

Materials and Methods: M2 macrophages in HCC patients were detected by immunohistostaining using a common macrophage marker [CD68] and a M2 specific marker [CD163]. The expression pattern of M2 macrophage was further correlated with clinical pathological parameters in terms of tumor size, staging, survival and metastasis. The mRNA expression of M2 specific scavenger receptor A (SR-A) and mannose receptor (MR) measured by quantitative real-time RT-PCR were also compared. The function and characteristic of M1 (anti-tumor) and M2 (pro-tumor) polarized macrophages derived from human THP-1 cell line, was examined in a series of in vitro functional studies. The role of M1 and M2 macrophages on liver tumor growth and metastasis were further validated in an orthotopic liver cancer nude mice model.

Results: In the clinical association study, both the numbers of CD68-positive and CD163-positive cells in non-tumor but not the tumor region significantly correlated with poor overall survival (CD68:p=0.023; CD163: p=0.042), large tumor size (CD68: p=0.028; CD163: p=0.027) and high recurrent rate (CD68: p=0.049; CD163: p=0.034). Consistently, mRNA expression of SR-A and MR mRNA also significantly correlated with overall survival, tumor size and recurrence rate (p&lt;0.05). In the in vitro functional studies, by co-culturing with M2 and M1 polarized macrophages, HCC cell line – MHCC97L showed 1.5 folds increased and 3 folds decreased respectively in the growth rate compared with control (p=0.019). In addition, co-culture with M2 but not M1 polarized macrophages induced the releases and activities of matrix metalloproteinase-9 (MMP-9) and MMP-2, which subsequent promoted invasiveness of HCC cell line – MHCC97L detected by cell migration and invasion assays. In the orthotopic model, portal vein injection of M2 macrophages induced the 30% increase of tumor size compared with the control group. On the contrary, M1 macrophage injection decreased the 90% of tumor size. Higher lung metastatic rate (57%) was also noted in M2 treated group compared with the control group (25%, p&lt;0.05).

Conclusions: Clinical analysis and both the in vitro and in vivo studies presented here collectively illustrated that M2 macrophages promoted tumor growth and invasion in HCC. On the other hand, tumor suppression phenotypes of M1 macrophages were also shown. Inhibition or M1 phenotypic conversion of M2 macrophages in situ represents a novel approach for treating the disease.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 471. doi:10.1158/1538-7445.AM2011-471