Recombinant VP1, an Akt Inhibitor, Suppresses Progression of Hepatocellular Carcinoma by Inducing Apoptosis and Modulation of CCL2 Production

Abstract

BackgroundThe application of viral elements in tumor therapy is one facet of cancer research. Recombinant capsid protein VP1 (rVP1) of foot-and-mouth disease virus has previously been demonstrated to induce apoptosis in cancer cell lines. Here, we aim to further investigate its apoptotic mechanism and possible anti-metastatic effect in murine models of hepatocellular carcinoma (HCC), one of the most common human cancers worldwide.Methodology/Principal FindingsTreatment with rVP1 inhibited cell proliferation in two murine HCC cell lines, BNL and Hepa1-6, with IC50 values in the range of 0.1–0.2 µM. rVP1 also induced apoptosis in these cells, which was mediated by Akt deactivation and dissociation of Ku70-Bax, and resulted in conformational changes and mitochondrial translocation of Bax, leading to the activation of caspases-9, -3 and -7. Treatment with 0.025 µM rVP1, which did not affect the viability of normal hepatocytes, suppressed cell migration and invasion via attenuating CCL2 production. The production of CCL2 was modulated by Akt-dependent NF-κB activation that was decreased after rVP1 treatment. The in vivo antitumor effects of rVP1 were assessed in both subcutaneous and orthotopic mouse models of HCC in immune-competent BALB/c mice. Intratumoral delivery of rVP1 inhibited subcutaneous tumor growth as a result of increased apoptosis. Intravenous administration of rVP1 in an orthotopic HCC model suppressed tumor growth, inhibited intra-hepatic metastasis, and prolonged survival. Furthermore, a decrease in the serum level of CCL2 was observed in rVP1-treated mice.Conclusions/SignificanceThe data presented herein suggest that, via inhibiting Akt phosphorylation, rVP1 suppresses the growth, migration, and invasion of murine HCC cells by inducing apoptosis and attenuating CCL2 production both in vitro and in vivo. Recombinant protein VP1 thus has the potential to be developed as a new therapeutic agent for HCC.

Autophagy-mediated regulation of macrophages and its applications for cancer

“…16 Several studies have shown that treatments targeting autophagy can modify the activation states of macrophages. 62,63,66,67,72 These findings should encourage studies to develop genetic and pharmacological approaches to skew TAM polarization to the M1 phenotype by targeting autophagy. For example, even if TLR2 deficiency causes a reduction of macrophage infiltration, this ablation also induces a significant suppression of autophagy and a reduction in the expression of TNF/ TNFα (tumor necrosis factor), IFNG (interferon, gamma) and CXCL2 (chemokine [C-X-C motif] ligand 2) in liver tissues, indicating an increase of M2 macrophage polarization, which in turn promotes hepatocarcinogenesis.…”

“…Inhibition of autophagy under these circumstances attenuates M2 macrophage polarization, which directly indicates that autophagy plays a key role in macrophage polarization. 67 Sorafenib is an antiangiogenic agent that has been approved for cancer treatment. However, some studies also demonstrated that antiangiogenic drugs may, in some conditions, accelerate cancer progression.…”

Chemokines, chemokine receptors and the gastrointestinal system

“…This combination was also shown to induce an innate immune response involving monocytes/macrophages and NK cells, leading to prolongation of anti-metastatic effects [144][145][146] . CCL2 was also identified by Chen et al [147] as a potential target for development of future HCC treatment. Using the recombinant foot-and-mouth disease virus capsid protein VP1 (rVP1), they were able to induce apoptosis of HCC cell lines through deactivation of the AKT pathway and stimulation of caspase cascades via Bax.…”

“…Using the recombinant foot-and-mouth disease virus capsid protein VP1 (rVP1), they were able to induce apoptosis of HCC cell lines through deactivation of the AKT pathway and stimulation of caspase cascades via Bax. Furthermore, rVP1 downregulated the expression of CCL2 in an AKT-dependent manner, which can support the survival and migration of HCC tumor cell lines [147] . CXCR7, a CXCL12 receptor, has also been reported to be upregulated in HCC [148] .…”

“…Application to prevent metastasis, application to prevent HCC by deactivating AKT pathway [144][145][146][147] …”