Impact of tumour associated macrophages in pancreatic cancer

During cancer progression, bone marrow derived myeloid cells, including immature myeloid cells and macrophages, progressively accumulate at the primary tumour site where they contribute to the establishment of a tumour promoting microenvironment. A marked infiltration of macrophages into the stromal compartment and the generation of a desmoplastic stromal reaction is a particular characteristic of pancreatic ductal adenocarcinoma (PDA) and is thought to play a key role in disease progression and its response to therapy. Tumour associated macrophages (TAMs) foster PDA tumour progression by promoting angiogenesis, metastasis, and by suppressing an anti-tumourigenic immune response. Recent work also suggests that TAMs contribute to resistance to chemotherapy and to the emergence of cancer stem-like cells. Here we will review the current understanding of the biology and the pro-tumourigenic functions of TAMs in cancer and specifically in PDA, and highlight potential therapeutic strategies to target TAMs and to improve current therapies for pancreatic cancer. [BMB Reports 2013; 46(3): 131-138]     

Proangiogenic TIE2+/CD31+ macrophages are the predominant population of tumor-associated macrophages infiltrating metastatic lymph nodes

Tumor-associated macrophages (TAMs) accumulate in various cancers and promote tumor angiogenesis and metastasis, and thus may be ideal targets for the clinical diagnosis of tumor metastasis with high specificity. However, there are few specific markers to distinguish between TAMs and normal or inflammatory macrophages. Here, we show that TAMs localize in green fluorescent protein-labeled tumors of metastatic lymph nodes (MLNs) from B16F1 melanoma cells but not in necrotic tumor regions, suggesting that TAMs may promote the growth of tumor cells and the progression of tumor metastasis. Furthermore, we isolated pure populations of TAMs from MLNs and characterized their gene expression signatures compared to peritoneal macrophages (PMs), and found that TAMs significantly overexpress immunosuppressive cytokines such as IL-4, IL-10, and TGF-β as well as proangiogenic factors such as VEGF, TIE2, and CD31. Notably, immunological analysis revealed that TIE2⁺/CD31⁺ macrophages constitute the predominant population of TAMs that infiltrate MLNs, distinct from tissue or inflammatory macrophages. Importantly, these TIE2⁺/CD31⁺ macrophages also heavily infiltrated MLNs from human breast cancer biopsies but not reactive hyperplastic LNs. Thus, TIE2⁺/CD31⁺ macrophages may be a unique histopathological biomarker for detecting metastasis in clinical diagnosis, and a novel and promising target for TAM-specific cancer therapy.     

Current research progress in targeted anti‐angiogenesis therapy for osteosarcoma

Osteosarcoma (OS) is the most common primary malignant bone tumour with a peak in incidence during adolescence. Delayed patient presentation and diagnosis is common with approximately 15% of OS patients presenting with metastatic disease at initial diagnosis. With the introduction of neoadjuvant chemotherapy in the 1970s, disease prognosis improved from 17% to 60%‐70% 5‐year survival, but outcomes have not significantly improved since then. Novel and innovative therapeutic strategies are urgently needed as an adjunct to conventional treatment modalities to improve outcomes for OS patients. Angiogenesis is crucial for tumour growth, metastasis and invasion, and its prevention will ultimately inhibit tumour growth and metastasis. Dysregulation of angiogenesis in bone microenvironment involving osteoblasts and osteoclasts might contribute to OS development. This review summarizes existing knowledge regarding pre‐clinical and developmental research of targeted anti‐angiogenic therapy for OS with the aim of highlighting the limitations associated with this application. Targeted anti‐angiogenic therapies include monoclonal antibody to VEGF (bevacizumab), tyrosine kinase inhibitors (Sorafenib, Apatinib, Pazopanib and Regorafenib) and human recombinant endostatin (Endostar). However, considering the safety and efficacy of these targeted anti‐angiogenesis therapies in clinical trials cannot be guaranteed at this point, further research is needed to completely understand and characterize targeted anti‐angiogenesis therapy in OS.     

CDDO-Me Redirects Activation of Breast Tumor Associated Macrophages

Tumor-associated macrophages can account for up to 50% of the tumor mass in breast cancer patients and high TAM density is associated with poor clinical prognosis. Because TAMs enhance tumor growth, development, and metastatic potential, redirection of TAM activation may have significant therapeutic benefit. Our studies in primary human macrophages and murine breast TAMs suggest that the synthetic oleanane triterpenoid CDDO-methyl ester (CDDO-Me) reprograms the activation profile of TAMs from tumor-promoting to tumor-inhibiting. We show that CDDO-Me treatment inhibits expression of IL-10 and VEGF in stimulated human M2 macrophages and TAMs but increases expression of TNF-α and IL-6. Surface expression of CD206 and CD163, which are characteristic of M2 activation, is significantly attenuated by CDDO-Me. In contrast, CDDO-Me up-regulates surface expression of HLA-DR and CD80, which are markers of M1 activation, and importantly potentiates macrophage activation of autologous T cells but inhibits endothelial cell vascularization. These results show for the first time that CDDO-Me redirects activation of M2 macrophages and TAMs from immune-suppressive to immune-stimulatory, and implicate a role for CDDO-Me as an immunotherapeutic in the treatment of breast and potentially other types of cancer.     

IL-12 rapidly alters the functional profile of tumor-associated and tumor-infiltrating macrophages in vitro and in vivo

Tumor-associated macrophages (TAMs) play a major role in promoting tumor growth and metastasis and in suppressing the antitumor immune response. Despite the immunosuppressive environment created by the tumor and enforced by tumor-associated macrophages, treatment of tumor-bearing mice with IL-12 induces tumor regression associated with appearance of activated NK cells and activated tumor-specific CTLs. We therefore tested the hypothesis that IL-12 treatment could alter the function of these tumor-associated suppressor macrophages. Analysis of tumor-infiltrating macrophages and distal TAMs revealed that IL-12, both in vivo and in vitro, induced a rapid (<90 min) reduction of tumor supportive macrophage activities (IL-10, MCP-1, migration inhibitory factor, and TGFbeta production) and a concomitant increase in proinflammatory and proimmunogenic activities (TNF-alpha, IL-15, and IL-18 production). Similar shifts in functional phenotype were induced by IL-12 in tumor-infiltrating macrophages isolated from the primary tumor mass and in TAMs isolated from lung containing metastases, spleen, and peritoneal cavity. Therefore, although TAMs display a strongly polarized immunosuppressive functional profile, they retain the ability to change their functional profile to proinflammatory activities given the appropriate stimulus. The ability of IL-12 to initiate this functional conversion may contribute to early amplification of the subsequent destructive antitumor immune response.     

Cancer Cell Expression of Autotaxin Controls Bone Metastasis Formation in Mouse through Lysophosphatidic Acid-Dependent Activation of Osteoclasts

Background

Bone metastases are highly frequent complications of breast cancers. Current bone metastasis treatments using powerful anti-resorbtive agents are only palliative indicating that factors independent of bone resorption control bone metastasis progression. Autotaxin (ATX/NPP2) is a secreted protein with both oncogenic and pro-metastatic properties. Through its lysosphospholipase D (lysoPLD) activity, ATX controls the level of lysophosphatidic acid (LPA) in the blood. Platelet-derived LPA promotes the progression of osteolytic bone metastases of breast cancer cells. We asked whether ATX was involved in the bone metastasis process. We characterized the role of ATX in osteolytic bone metastasis formation by using genetically modified breast cancer cells exploited on different osteolytic bone metastasis mouse models.

Methodology/Principal Findings

Intravenous injection of human breast cancer MDA-B02 cells with forced expression of ATX (MDA-B02/ATX) to inmmunodeficiency BALB/C nude mice enhanced osteolytic bone metastasis formation, as judged by increased bone loss, tumor burden, and a higher number of active osteoclasts at the metastatic site. Mouse breast cancer 4T1 cells induced the formation of osteolytic bone metastases after intracardiac injection in immunocompetent BALB/C mice. These cells expressed active ATX and silencing ATX expression inhibited the extent of osteolytic bone lesions and decreased the number of active osteoclasts at the bone metastatic site. In vitro, osteoclast differentiation was enhanced in presence of MDA-B02/ATX cell conditioned media or recombinant autotaxin that was blocked by the autotaxin inhibitor vpc8a202. In vitro, addition of LPA to active charcoal-treated serum restored the capacity of the serum to support RANK-L/MCSF-induced osteoclastogenesis.

Conclusion/Significance

Expression of autotaxin by cancer cells controls osteolytic bone metastasis formation. This work demonstrates a new role for LPA as a factor that stimulates directly cancer growth and metastasis, and osteoclast differentiation. Therefore, targeting the autotaxin/LPA track emerges as a potential new therapeutic approach to improve the outcome of patients with bone metastases.     

Expression of cyclo-oxygenase-2 in macrophages associated with cutaneous melanoma at different stages of progression

The biological significance of the almost constant presence of macrophages in the tumoral microenvironment is an issue debated by several authors. The major difficulty in understanding the role played by tumor-associated macrophages (TAMs) in tumor progression is due to the contrasting effects of TAMs found in different studies. In addition, there is a limited information on which of the many biological activities expressed by TAMs are critical in inducing stimulatory or inhibitory effect on tumor growth. The aim of our study was: (a) to explore to what extent cyclo-oxygenase-2 (COX-2) in TAMs associated with human melanoma is expressed at different stages of tumor progression; and (b) to explore whether COX-2 expression in TAMs is stimulated by melanoma cells. In order to answer this question, we determined COX-2 positive TAMs associated with cutaneous melanocytic nevi, in situ, invasive and metastatic melanoma. In addition, we investigated whether COX-2 is expressed in peritoneal thioglycollate-elicited macrophages after co-cultivation with murine B16 melanoma cells. We found that COX-2-positive TAMs, as revealed by immunohistochemical analysis, were rare in common nevi and "dysplastic nevi", but present in a high percentage in in situ and thin melanoma. COX-2-positive TAMs were also found in more advanced tumors and metastatic melanoma, although at a significantly lower percentage in these latter. The in vitro protocol revealed that COX-2 was expressed in peritoneal macrophages upon contact with B16 murine melanoma cells, but not with normal murine fibroblasts. On the whole, the results of in vivo and in vitro studies suggest that COX-2 expressed in TAMs appears to act as an effective biomarker of melanoma progression, and melanoma cells themselves might stimulate COX-2 in macrophages.     

BMP2 signalling activation enhances bone metastases of non‐small cell lung cancer

Distant metastases occur when non‐small cell lung cancer (NSCLC) is at late stages. Bone metastasis is one of the most frequent metastases of NSCLC and leads to poor prognosis. It has been reported that high expression of BMP2 in NSCLC correlates with poor survival, but whether BMP2 contributes to NSCLC bone metastasis remains largely unknown. The activation of BMP signalling is found in metastatic bone tumours of mice Lewis lung carcinoma and predicts poor survival in human NSCLC. BMP2 signalling activation can enhance bone metastasis of Lewis lung carcinoma. Moreover, BMP2 secreted by stroma fibroblasts can promote the migration and invasion of NSCLC cells. Besides, in combination with pre‐osteoblast and LLCs, BMP2 could enhance the differentiation of macrophages into osteoclasts to play roles in the osteolytic mechanism of NSCLC bone metastasis. Interestingly, NSCLC cells can also enrich BMP2 to pre‐osteoblasts to function in the osteoblastic mechanism. Our results firstly demonstrate the detailed mechanisms about what roles BMP2 signalling play in enhancing NSCLC bone metastases. These findings provide a new potential therapy choice for preventing bone metastases of NSCLC via the inhibition of BMP2 signalling.     

SNAIL Induces EMT and Lung Metastasis of Tumours Secreting CXCL2 to Promote the Invasion of M2-Type Immunosuppressed Macrophages in Colorectal Cancer

Background: There is increasing evidence that tumour-associated macrophages (TAMs) are critical in the formation of lung metastases. However, the molecular mechanisms of tumour interactions with TAMs via EMT are largely unknown.Methods: The mechanism of lung metastasis was studied in patient tissues. The mechanism of SNAIL regulation of the interaction between mesenchymal cells and M2 macrophages was elucidated using coculture of M2 macrophages and Transwell assays in vitro and in vivo in nude mice and NOD-SCID mice.Results: We demonstrated for the first time that SNAIL and CXCL2 were abnormally overexpressed in colorectal cancer, especially lung metastasis, and were associated with poor prognosis in colorectal cancer patients. We demonstrated that SNAIL promoted the secretion of CXCL2 by mesenchymal cells and induced the activation of M2 macrophages. We found that CXCL2 attracted M2-type macrophages to infiltrate and promote tumour metastasis.Conclusion: These findings suggest that SNAIL promotes epithelial tumour transformation, and that transformed mesenchymal cells secrete CXCL2, which promotes M2 macrophage infiltration and tumour cell metastasis. These findings elucidate the tumour-TAM interaction in the metastatic microenvironment, which is mediated by tumour-derived CXCL2 and affects lung metastasis. This study also provides a theoretical basis for the occurrence of secondary lung cancer.     

Prognostic significance of tumor-associated macrophages polarization markers in lung cancer: a pooled analysis of 5105 patients

Background: The prognostic significance of tumor-associated macrophages (TAMs) in patients with lung cancer (LCa) remains controversial. We therefore conducted the present study to systematically evaluate the role of different TAMs markers and histologic locations on the prognosis of LCa.Methods: Searches of Web of Science, PubMed, and EMBASE databases were performed up to 28 February 2022. The pooled analysis was conducted in random-effect or fixed-effects model with hazard risk (HR) and 95% confidence interval (CI) for survival data including overall survival (OS), and disease-free survival (DFS) from raw or adjusted measures, according to different TAMs markers and histologic locations.Results: Including a total of 5105 patients from 30 eligible studies, the results indicated that the total count of CD68+ TAMs was negatively associated with OS and DFS, which was also observed in the relationship of CD68+ or CD204+ TAMs in tumor stroma (TS) with OS and DFS (all P<0.05). Conversely, higher CD68+ TAMs density in tumor nest (TN) or TN/TS ratio of CD68+ TAMs predicted better OS (all P<0.05). Similarly, higher HLA-DR+ TAMs density was correlated with better OS in TN and TS (all P<0.05). Besides, neither nest CD163+ TAM density nor stromal CD163+ TAM density was a prognostic factor in LCa patients (all P>0.05).Conclusion: Our study indicated that different TAMs markers and histologic locations could bring about different prognostic effects in LCa patients. Great understanding of the infiltration modes of TAMs may contribute to improve outcomes of LCa patients.     

Matrix Metalloproteinase 1 promotes tumor formation and lung metastasis in an intratibial injection osteosarcoma mouse model

Proteolytic degradation of the extracellular matrix (ECM) is an important process during tumor invasion. Matrix Metalloproteinase 1 (MMP-1) is one of the proteases that degrade collagen type I, a major component of bone ECM. In the present study, the biological relevance of MMP-1 in osteosarcoma (OS) tumor growth and metastasis was investigated in vitro and in vivo. Human OS cells in primary culture expressed MMP-1 encoding mRNA at considerably higher levels than normal human bone cells. In addition, MMP-1 mRNA and protein expression in the highly metastatic human osteosarcoma 143-B cell line was remarkably higher than in the non-metastatic parental HOS cell line. Stable shRNA-mediated downregulation of MMP-1 in 143-B cells impaired adhesion to collagen I and anchorage-independent growth, reflected by a reduced ability to grow in soft agar. Upon intratibial injection into SCID mice, 143-B cells with shRNA-downregulated MMP-1 expression formed smaller primary tumors and significantly lower numbers of lung micro- and macrometastases than control cells. Conversely, HOS cells stably overexpressing MMP-1 showed an enhanced adhesion capability to collagen I and accelerated anchorage-independent growth compared to empty vector-transduced control cells. Furthermore, and most importantly, individual MMP-1 overexpression in HOS cells enabled the formation of osteolytic primary tumors and lung metastasis while the HOS control cells did not develop any tumors or metastases after intratibial injection. The findings of the present study reveal an important role of MMP-1 in OS primary tumor and metastasis formation to the lung, the major organ of OS metastasis.     

Progression of Osteosarcoma from a Non-Metastatic to a Metastatic Phenotype Is Causally Associated with Activation of an Autocrine and Paracrine uPA Axis

Pulmonary metastasis is the major untreatable complication of osteosarcoma (OS) resulting in 10–20% long-term survival. The factors and pathways regulating these processes remain unclear, yet their identification is crucial in order to find new therapeutic targets. In this study we used a multi-omics approach to identify molecules in metastatic and non-metastatic OS cells that may contribute to OS metastasis, followed by validation in vitro and in vivo. We found elevated levels of the urokinase plasminogen activator (uPA) and of the uPA receptor (uPAR) exclusively in metastatic OS cells. uPA was secreted in soluble form and as part of the protein cargo of OS-secreted extracellular vesicles, including exosomes. In addition, in the tumour microenvironment, uPA was expressed and secreted by bone marrow cells (BMC), and OS- and BMC-derived uPA significantly and specifically stimulated migration of metastatic OS cells via uPA-dependent signaling pathways. Silencing of uPAR in metastatic OS cells abrogated the migratory response to uPA in vitro and decreased metastasis in vivo. Finally, a novel small-molecule inhibitor of uPA significantly (P = 0.0004) inhibited metastasis in an orthotopic mouse model of OS. Thus, we show for the first time that malignant conversion of OS cells to a metastatic phenotype is defined by activation of the uPA/uPAR axis in both an autocrine and paracrine fashion. Furthermore, metastasis is driven by changes in OS cells as well as in the microenvironment. Finally, our data show that pharmacological inhibition of the uPA/uPAR axis with a novel small-molecule inhibitor can prevent the emergence of metastatic foci.     

Anti-tumor effect in human breast cancer by TAE226, a dual inhibitor for FAK and IGF-IR in vitro and in vivo

Focal adhesion kinase (FAK) is a 125-kDa non-receptor type tyrosine kinase that localizes to focal adhesions. FAK overexpression is frequently found in invasive and metastatic cancers of the breast, colon, thyroid, and prostate, but its role in osteolytic metastasis is not well understood. In this study, we have analyzed anti-tumor effects of the novel FAK Tyr³⁹⁷ inhibitor TAE226 against bone metastasis in breast cancer by using TAE226. Oral administration of TAE226 in mice significantly decreased bone metastasis and osteoclasts involved which were induced by MDA-MB-231 breast cancer cells and increased the survival rate of the mouse models of bone metastasis. TAE226 also suppressed the growth of subcutaneous tumors in vivo and the proliferation and migration of MDA-MB-231 cells in vitro. Significantly, TAE226 inhibited the osteoclast formation in murine pre-osteoclastic RAW264.7 cells, and actin ring and pit formation in mature osteoclasts. Moreover, TAE226 inhibited the receptor activator for nuclear factor κ B Ligand (RANKL) gene expression induced by parathyroid hormone-related protein (PTHrP) in bone stromal ST2 cells and blood free calcium concentration induced by PTHrP administration in vivo. These findings suggest that FAK was critically involved in osteolytic metastasis and activated in tumors, pre-osteoclasts, mature osteoclasts, and bone stromal cells and TAE226 can be effectively used for the treatment of cancer induced bone metastasis and other bone diseases.     

Silencing of CD44 Gene Expression in Human 143-B Osteosarcoma Cells Promotes Metastasis of Intratibial Tumors in SCID Mice

Osteosarcoma (OS) is the most frequent primary malignant bone cancer in children and adolescents with a high propensity for lung metastasis. Therefore, it is of great importance to identify molecular markers leading to increased metastatic potential in order to devise more effective therapeutic strategies that suppress metastasis, the major cause of death in OS. CD44, the principal receptor for the extracellular matrix component hyaluronan (HA), is frequently found overexpressed in tumor cells and has been implicated in metastatic spread in various cancer types. Here, we investigated the effects of stable shRNA-mediated silencing of CD44 gene products on in vitro and in vivo metastatic properties of the highly metastatic human 143-B OS cell line. In vitro, CD44 knockdown resulted in a 73% decrease in the adhesion to HA, a 57% decrease in the migration rate in a trans-filter migration assay, and a 28% decrease in the cells'' capacity for anchorage-independent growth in soft agar compared to the control cells, implicating that CD44 expression contributes to the metastatic activity of 143-B cells. However, making use of an orthotopic xenograft OS mouse model, we demonstrated that reduced CD44 expression facilitated primary tumor growth and formation of pulmonary metastases. The enhanced malignant phenotype was associated with decreased adhesion to HA and reduced expression of the tumor suppressor merlin in vivo. In conclusion, our study identified CD44 as a metastasis suppressor in this particular experimental OS model.     

Activation state of stromal inflammatory cells in murine metastatic pancreatic adenocarcinoma

The histologic presence of macrophages (tumor-associated macrophages, TAMs) and neutrophils (tumor-associated neutrophils, TANs) has been linked to poor clinical outcomes for solid tumors. The exact mechanism for this association with worsened prognosis is unclear. It has been theorized that TAMs are immunomodulated to an alternatively activated state and promote tumor progression. Similarly, TANs have been shown to promote angiogenesis and tumor detachment. TAMs and TANs were characterized for activation state and production of prometastatic mediators in an immunocompetent murine model of pancreatic adenocarcinoma. Specimens from liver metastases were evaluated by immunofluorescence and immunoblotting. TAMS have upregulated expression of CD206 and CD163 markers of alternative activation, (4.14 ± 0.55-fold and 7.36 ± 1.13-fold over control, respectively, P < 0.001) but do not have increased expression of classically activated macrophage markers CCR2 and CCR5. TAMs also express oncostatin M (OSM). We found that TANs, not TAMs, predominantly produce matrix metalloproteinase-9 (MMP-9) in this metastatic tumor microenvironment, while MMP-2 production is pan-tumoral. Moreover, increased expression of VEGF colocalized with TAMs as opposed to TANs. TAMs and TANs may act as distinct effector cells, with TAMs phenotypically exhibiting alternative activation and releasing OSM and VEGF. TANs are localized at the invasive front of the metastasis, where they colocalize with MMP-9. Improved understanding of these interactions may lead to targeted therapies for pancreas adenocarcinoma.     

肿瘤相关巨噬细胞：在肿瘤演进中的作用及潜在抗肿瘤靶点

炎症是公认的肿瘤十大特征之一,而肿瘤相关巨噬细胞是肿瘤微环境的重要组成部分,它影响肿瘤的生长、血管生成、免疫抑制、 转移和药物抗性。最新研究表明,肿瘤相关巨噬细胞还会影响抗肿瘤治疗的临床疗效。鉴于肿瘤相关巨噬细胞在肿瘤演进中起重要作用, 其作为潜在抗肿瘤靶点备受关注。基于最新的研究,对人类癌症中肿瘤相关巨噬细胞的主要功能、作用和特征以及用作新兴肿瘤治疗干预 靶点作一综述。     

Tumor associated macrophage × cancer cell hybrids may acquire cancer stem cell properties in breast cancer

Breast cancer is one of the most frequently diagnosed cancers among women, and metastasis makes it lethal. Tumor-associated macrophages (TAMs) that acquire an alternatively activated macrophage (M2) phenotype may promote metastasis. However, the underlying mechanisms are still elusive. Here, we examined how TAMs interact with breast cancer cells to promote metastasis. Immunohistochemistry was used to examine the expression of the M2-specific antigen CD163 in paraffin-embedded mammary carcinoma blocks to explore fusion events in breast cancer patients. U937 cells were used as a substitute for human monocytes, and these cells differentiated into M2 macrophages following phorbol 12-myristate 13-acetate (PMA) and M-CSF stimulation. M2 macrophages and the breast cancer cell lines MCF-7 and MDA-MB-231 fused in the presence of 50% polyethylene glycol. Hybrids were isolated by fluorescence-activated cell sorting, and the relevant cell biological properties were compared with their parental counterparts. Breast cancer stem cell (BCSC)-related markers were quantified by immunofluorescence staining, RT-PCR, quantitative RT-PCR and/or western blotting. The tumor-initiating and metastatic capacities of the hybrids and their parental counterparts were assessed in NOD/SCID mice. We found that the CD163 expression rate in breast cancer tissues varied significantly and correlated with estrogen receptor status (p<0.05). The fusion efficiency of either breast cancer cell line with M2 macrophages ranged from 1.81 to 6.47% in the presence of PEG, and no significant difference was observed between the breast cancer cell lines used (p>0.05). Characterization of the fusion hybrids revealed a more aggressive phenotype, including increased migration, invasion and tumorigenicity, but reduced proliferative ability, compared with the parental lines. The hybrids also gained a CD44(+)CD24(-/low) phenotype and over-expressed epithelial-mesenchymal transition-associated genes. These results indicate that TAMs may promote breast cancer metastasis through cell fusion, and the hybrids may gain a BCSC phenotype.     

CD169-positive macrophages enhance abscopal effect of radiofrequency ablation therapy in liver cancer

Radiofrequency ablation (RFA) is a widely used and effective treatment for primary or metastatic liver cancer with small-size lesions. However, the therapeutic effectiveness of RFA in controlling metastatic lesion or recurrence is still limited. As the major cell population in tumor microenvironment (TME), macrophages have been reported to be recruited to RFA-treated lesion, but their roles are still unclear. Herein, we successfully established the mouse model mimicking RFA-induced abscopal effect, in which RFA eliminated the local orthotopic liver tumor but failed to control growth of distant tumor. Correspondently, RFA suppressed protumoral activation of local tumor-associated macrophages (TAMs), but failed to reprogram TAMs in distance. Importantly, although RFA led to reduced proportion of hepatic CD169⁺ macrophages in local and decreased expression of immune inhibitory molecules Tim-3 and PD-L1, these alterations were not observed for CD169⁺ macrophages in distant TME. Further RNA-seq and flow cytometry analysis showed that hepatic CD169⁺ macrophages contributed to reprograming TME through recruiting CD8⁺ T/NK cells and suppressing accumulation of MDSCs/Tregs. Consistently, depletion of CD169⁺ macrophages in CD169-DTR mouse greatly promoted liver tumor progression and largely dampened RFA-induced tumor suppression. Notably, transfer of CD169⁺ macrophages synergistically enhanced RFA-induced inhibition of distant tumor. To our knowledge, this is the first study which demonstrates hepatic CD169⁺ macrophages as a key factor responsible for RFA-induced abscopal effect. Our data suggest RFA with transfer of CD169⁺ macrophages as a promising combination therapy to lessen metastasis or recurrence of liver cancer in patients.