Targeting tumor-associated macrophages and granulocytic myeloid-derived suppressor cells augments PD-1 blockade in cholangiocarcinoma

Abstract

Figure 1. TAMs are the predominant source of PD-L1 in CCA. (A) Representative images (left and middle panels) of PD-L1 (brown staining, black arrowhead) plus CD68 (red staining, red arrowhead) coimmunostaining (n = 33) and PD-L1 (brown staining) plus CK-19 (red staining) coimmunostaining (n = 18) in human resected CCA specimens. Percentage of patients with positive PD-L1/CD68 costaining and PD-L1/CK19 costaining, respectively (right panel). Scale bars: 40 μm. (B) Histograms show expression of PD-L1 + macrophages in human CCA tumors. (C-F) Flow cytometry analysis of normal WT mouse livers (from WT mice without tumors) as well as adjacent livers and tumors of mice 28 days after orthotopic implantation of 1 × 10 6 SB (murine CCA) cells. (C) Percentage of PD-L1 + macrophages (Mφ) of total macrophages (CD45 + CD11b + F4/80 + ) in WT mouse normal liver, tumor-adjacent liver, or tumor. Fluorescence Minus One (FMO) controls were used for each independent experiment to establish gates (See Supplemental Figure 1A for gating strategy) (n ≥ 8). Representative histograms show expression of PD-L1 + macrophages. (D) Percentage of CD206 + TAMs (left panel) and PD-L1 + CD206 + TAMs (middle panel) of F4/80 int macrophages (CD45 + CD11b + F4/80 int ) in WT mouse liver, tumor-adjacent liver, or tumor. Representative contour plots (right panel) show CD206 and PD-L1 expression of F4/80 int macrophages (n ≥ 7). (E) Percentage of PD-L1 + CD206macrophages or PD-L1 + CD206 + macrophages (CD11b + F4/80 + ) of CD45 + cells from SB tumors (n = 28). (F) Percentage of PD-L1 expression in myeloid cells from SB tumors.

Dendritic Cells and Myeloid Derived Suppressor Cells Fully Responsive to Stimulation via Toll-Like Receptor 4 Are Rapidly Induced from Bone-Marrow Cells by Granulocyte-Macrophage Colony-Stimulating Factor

“…Here it is shown that GR-1 hi MDSCs are morphologically granulocytic, confirmed by their expression of Ly6G, and GR-1 int MDSCs are monocytic like cells morphologically and express high levels of Ly6C. This is consistent with other reports of GR-1 and Ly6C/G expression [37,38]. MDSCs are potent suppressor cells, and their presence in various pathological conditions has been proven to cause damaging effects and worsen prognosis in patients [39].…”

“…Their phenotype and functions have been studied in detail only more recently [ 31 , 32 ]. Whilst some studies use CD11b+, GR-1+ phenotype to describe MDSCs in different disease models [ 33 , 34 , 35 ], others define granulocytic MDSCs as Ly6Ghi and monocytic MDSCs as Ly6Chi [ 36 , 37 ]. Here it is shown that GR-1 hi MDSCs are morphologically granulocytic, confirmed by their expression of Ly6G, and GR-1 int MDSCs are monocytic like cells morphologically and express high levels of Ly6C.…”

Tumor Burden and Immunotherapy: Impact on Immune Infiltration and Therapeutic Outcomes

“…For example, pharmacological inhibition of PI3K-γ, which is highly expressed on myeloid cells, shifted TAMs from a M2-like immunosuppressive phenotype to an inflammatory M1-like phenotype in the murine 4T1 mammary carcinoma and B16 melanoma models ( 115 ). Paradoxically, reducing TAMs can result in a compensatory increase of MDSCs ( 116 , 117 ). However, this effect can be overcome by blocking both TAMs and gMDSCs, which augments the efficacy of PD-1 blockade in a mouse model of cholangiocarcinoma ( 116 ) and bolsters chemotherapy in a mouse model of PDAC ( 117 ).…”

Myeloid-Derived Suppressor Cells: Facilitators of Cancer and Obesity-Induced Cancer

“…Some of the drugs have also been used in clinical trials, either as stand-alone therapies or in combination with immunotherapy or non-immune-based established cancer therapies, including chemotherapy and radiotherapy. Several studies have demonstrated that combining MDSC inhibition with CBI yields significantly better control of tumor growth compared to monotherapy (Christmas et al 2018, Clavijo et al 2019, Loeuillard et al 2020, Orillion et al 2017. For example, in a clinical trial of advanced melanoma patients treated with all-trans retinoic acid, an inhibitor of MDSC, in combination with the CTLA-4 monoclonal antibody ipilimumab, patients had significantly reduced levels of PD-L1, IL-10, and IDO (indoleamine 2,3dioxygenase)-expressing MDSC (NCT02403778) (Tobin et al 2018).…”