Macrophages Polarized by Expression of ToxoGRA15II Inhibit Growth of Hepatic Carcinoma

Abstract

A growing body of evidence suggests that tumor-associated macrophages are deeply involved in the hepatocellular carcinoma proliferation and account for the large proportion of infiltrated cells in tumor tissues and play a major role in promotion of tumor growth. On the other hand, studies have demonstrated that <i>Toxoplasma gondii</i> virulence-associated molecule of dense granule protein (ToxoGRA15_II) tends to induce classically activated macrophages (M1) differentiation. Thus, we explored the M1 induced by ToxoGRA15_II<i>in vitro</i> and its inhibitory impact on the proliferation, invasion, and metastasis of hepatic carcinoma in murine model. Here, we constructed recombinant plasmid of <i>pegfp-gra15_II</i> and subsequently ligate it to lentivirus (Lv) vector, with which RAW264.7 was transfected. The results showed that the transfected macrophages were polarized to M1. Coculture of the M1 with Hepa1-6 cells showed a remarkable inhibition of migration and invasion of the tumor cells and decreased expressions of matrix metalloproteinase (MMP)-9 and MMP-2 without notable apoptosis of Hepa1-6 cells. Subsequently, ToxoGRA15_II-polarized macrophages inoculated to tumor-bearing C57BL/6 mice were seen in both spleen and tumor tissues, and tumor growth was sharply restricted. Particularly, interleukin-6 (IL-6) expression, which is closely associated with the cancer malignant behaviors, was significantly dampened in tumor tissues. In addition, expression of TNF-α and IL-12 mRNAs was increased, whereas IL-6 and interleukin-10 mRNAs were downregulated in splenocytes. Our results indicate that the effector molecule of ToxoGRA15_II may induce macrophage polarization to M1 that has a restrictive effect on tumor growth <i>via</i> its related cytokines profile in tumor and spleen tissues. Besides, ToxoGRA15_II, due to its early activation of specified cell population and non-toxicity to mammalians, has a potential value for a novel therapeutic strategy of enhancing host innate immunity against tumor development.