Depletion of M2-Like Tumor-Associated Macrophages Delays Cutaneous T-Cell Lymphoma Development In Vivo

Abstract

Macrophages have key roles in tumor development and invasion in several human cancers, but little is known about their pathogenic role in cutaneous T-cell lymphoma (CTCL). Herein, we used PCR arrays to profile the expression of inflammatory cytokines in 12 patients with mycosis fungoides (MF), the most common variant of CTCL. Compared with normal controls, MF skin displayed increased mRNA levels of macrophage-related cytokines. Moreover, we detected CD163, a reliable marker of tumor-associated macrophages, in the tumor microenvironment of MF biopsies. To demonstrate that macrophages had a role in CTCL tumorigenesis, we xenografted human CTCL tumor cells in immunocompromised mice and compared tumor development using clodronate-containing liposomes to deplete macrophages in mice. Mice treated with clodronate-containing liposomes show markedly less tumor growth compared with mice treated with phosphate-buffered saline-containing liposomes (P<0.001). We also noted a strong correlation between macrophage depletion and decreased expression of vascular marker, CD31, and lymphatic marker, podoplanin, suggesting a role for macrophages in angiogenesis. In vitro, clodronate-containing liposomes killed activated murine M2 macrophages, but not Hut78 cells, demonstrating selective ability to induce apoptosis in macrophages. Our data indicate that macrophages have a critical role in the progression of Hut78 cell tumor formation in skin, thus providing a new therapeutic strategy for CTCL.

Highly cytotoxic natural killer cells are associated with poor prognosis in patients with cutaneous T-cell lymphoma

“…For example, previous studies by our group and others have demonstrated alterations in NK-cell signaling because of the presence of suppressive myeloid cells such as myeloid-derived suppressor cells and tumor-associated macrophages in cancer patients, 26 and both populations have been reported among CTCL patients. [27][28][29] Additional checkpoint inhibitors, such as PD-1, CTLA-4, TIGIT, and TIM-3 may also play a role in decreasing NK-cell function in patients, because previous studies demonstrated that these inhibitors may be increased in the presence of IL-15.…”

Tumor-associated M2 macrophages in mycosis fungoides acquire immunomodulatory function by interferon alpha and interferon gamma

“…1). Notably, we identified several genes that were previously reported to correlate with CTCL biological activities (CCL7, CCL17, CCL18, CCL22, CCL26 and CXCL12) [8,9,[13][14][15]. Moreover, among the upregulated MMP-related genes, the mRNA expression of MMP12, which was previously correlated with the risk of progression of MF [8], was highly upregulated (Fig.…”

“…Since CD163 + TAMs promote the formation of CTCL in vivo [9], and since M2 macrophages are the predominant TAMs at the advanced stage of MF [4], first, we investigated the effects of IL-4 on CD163 + macrophages by using monocyte-derived macrophages in vitro. We sorted CD14 + monocytes (CD14 + Mo) from PBMCs of healthy donors by using MACS and then induced their differentiation into macrophages by culture with M-CSF for 5 days, as previously described [11].…”

“…To validate the quantitative RT-PCR results obtained by using M2 macrophages treated with IFNs, we used ELISA to examine chemokine protein production by M2 macrophages 48 h after stimulation with IFN-a2a or IFN-g, especially focusing on chemokines (CCL7, CCL17, CCL18, CCL22, CCL26, CXCL10, CXCL11 and CXCL12) previously reported to contribute to the formation and progression of MF [8,9,[13][14][15]. Consistent with the mRNA expression, the secretion of CXCL10 and CXCL11 protein was significantly augmented by IFN-a2a or IFN-g stimulation, while the secretion of CCL17 and CCL18 protein was significantly decreased compared to untreated cells.…”

“…In cutaneous T-cell lymphoma (CTCL), macrophage-related chemokines and angiogenic factors produced by TAMs have crucial roles in tumor formation in the lesional skin of MF [8,9]. In addition, we have also reported that the stromal factor of MF, periostin, could stimulate macrophages to produce chemokines that affect the formation of MF [4].…”