A Natural CCR2 Antagonist Relieves Tumor-associated Macrophage-mediated Immunosuppression to Produce a Therapeutic Effect for Liver Cancer

Abstract

Hepatocellular carcinoma (HCC) is a common malignant tumor in the digestive tract with limited therapeutic choices. Although sorafenib, an orally administered multikinase inhibitor, has produced survival benefits for patients with advanced HCC, favorable clinical outcomes are limited due to individual differences and resistance. The application of immunotherapy, a promising approach for HCC is urgently needed. Macrophage infiltration, mediated by the CCL2/CCR2 axis, is a potential immunotherapeutic target. Here, we report that a natural product from Abies georgei, named 747 and related in structure to kaempferol, exhibits sensitivity and selectivity as a CCR2 antagonist. The specificity of 747 on CCR2 was demonstrated via calcium flux, the binding domain of CCR2 was identified in an extracellular loop by chimera binding assay, and in vivo antagonistic activity of 747 was confirmed through a thioglycollate-induced peritonitis model. In animals, 747 elevated the number of CD8 + T cells in tumors via blocking tumor-infiltrating macrophage-mediated immunosuppression and inhibited orthotopic and subcutaneous tumor growth in a CD8 + T cell-dependent manner. Further, 747 enhanced the therapeutic efficacy of low-dose sorafenib without obvious toxicity, through elevating the numbers of intra-tumoral CD8 + T cells and increasing death of tumor cells. Thus, we have discovered a natural CCR2 antagonist and have provided a new perspective on development of this antagonist for treatment of HCC. In mouse models of HCC, 747 enhanced the tumor immunosuppressive microenvironment and potentiated the therapeutic effect of sorafenib, indicating that the combination of an immunomodulator with a chemotherapeutic drug could be a new approach for treating HCC.

Challenges of combination therapy with immune checkpoint inhibitors for hepatocellular carcinoma

“…98 Lower dosages (<30 mg/kg in vivo or <3 lM in vitro) appeared to be associated with a higher likelihood of inducing beneficial immunomodulatory effects, while higher dosages were immunosuppressive through induction of hypoxia and recruitment of MDSCs, TAMs, or other suppressive cells. [99][100][101] (Fig. 1).…”

Immunomodulatory Effects of Current Targeted Therapies on Hepatocellular Carcinoma: Implication for the Future of Immunotherapy

“…On the other hand, all of the seven studies with in vivo treatment of highdose sorafenib (> 30 mg/kg) discovered negative effects of high-dose sorafenib on immune microenvironment, such as an increase in PD-L1 expression, 48 or recruitment of MDSCs, Tregs, F4/80þ TAMs, Ly6Gþ neutrophils, or Gr-1þ monocytic and granulocytic cells. 45,[49][50][51][52] Hypoxia also elevated levels of colony-stimulating factor-1(CSF-1), C-X-C receptor type 4 (CXCR4), and stromal-derived factor 1α(SDF1α), which promoted a complex interaction among tumor cells, stromal cells, and immune cells. 51,53,54 It is also noteworthy that the dosage of 30 mg/kg/day in mice may not be achievable in human.…”

Compound kushen injection relieves tumor-associated macrophage-mediated immunosuppression through TNFR1 and sensitizes hepatocellular carcinoma to sorafenib

“…32 However, for some types of tumors, owing to the complexity of the immunosuppressive microenvironment, targeting CD8 + T cells alone is unlikely to be sufficient for cancer treatment in the clinic. 34 The established HCC microenvironment develops an anti-inflammatory stroma and recruits immunosuppressive immune cells such as MDSCs and TAMs, which block the process of antigen presentation and directly inhibit the proliferation and cytotoxic functions of CD8 + T cells. 35 Notably, TAMs are the primary immunosuppressive cells in the liver cancer microenvironment.…”