Embryonic Origin and Subclonal Evolution of Tumor-Associated Macrophages Imply Preventive Care for Cancer

Tissue-Resident Macrophages in Cancer: Friend or Foe?

INTRODUCTION

Macrophages are essential in maintaining homeostasis, combating infections, and influencing the process of various diseases, including cancer. Macrophages originate from diverse lineages: Notably, tissue-resident macrophages (TRMs) differ from hematopoietic stem cells and circulating monocyte-derived macrophages based on genetics, development, and function. Therefore, understanding the recruited and TRM populations is crucial for investigating disease processes.

METHODS

By searching literature databses, we summarized recent relevant studies. Research has shown that tumor-associated macrophages (TAMs) of distinct origins accumulate in tumor microenvironment (TME), with TRM-derived TAMs closely resembling gene signatures of normal TRMs.

RESULTS

Recent studies have revealed that TRMs play a crucial role in cancer progression. However, organ-specific effects complicate TRM investigations. Nonetheless, the precise involvement of TRMs in tumors is unclear. This review explores the multifaceted roles of TRMs in cancer, presenting insights into their origins, proliferation, the latest research methodologies, their impact across various tumor sites, their potential and strategies as therapeutic targets, interactions with other cells within the TME, and the internal heterogeneity of TRMs.

CONCLUSIONS

We believe that a comprehensive understanding of the multifaceted roles of TRMs will pave the way for targeted TRM therapies in the treatment of cancer.

Immunotherapies Targeting Tumor-Associated Macrophages (TAMs) in Cancer

Tumor-associated macrophages (TAMs) are one of the most plentiful immune compositions in the tumor microenvironment, which are further divided into anti-tumor M1 subtype and pro-tumor M2 subtype. Recent findings found that TAMs play a vital function in the regulation and progression of tumorigenesis. Moreover, TAMs promote tumor vascularization, and support the survival of tumor cells, causing an impact on tumor growth and patient prognosis. Numerous studies show that reducing the density of TAMs, or modulating the polarization of TAMs, can inhibit tumor growth, indicating that TAMs are a promising target for tumor immunotherapy. Recently, clinical trials have found that treatments targeting TAMs have achieved encouraging results, and the U.S. Food and Drug Administration has approved a number of drugs for use in cancer treatment. In this review, we summarize the origin, polarization, and function of TAMs, and emphasize the therapeutic strategies targeting TAMs in cancer treatment in clinical studies and scientific research, which demonstrate a broad prospect of TAMs-targeted therapies in tumor immunotherapy.

Exosome-mediated repair of spinal cord injury: a promising therapeutic strategy

Spinal cord injury (SCI) is a catastrophic injury to the central nervous system (CNS) that can lead to sensory and motor dysfunction, which seriously affects patients' quality of life and imposes a major economic burden on society. The pathological process of SCI is divided into primary and secondary injury, and secondary injury is a cascade of amplified responses triggered by the primary injury. Due to the complexity of the pathological mechanisms of SCI, there is no clear and effective treatment strategy in clinical practice. Exosomes, which are extracellular vesicles of endoplasmic origin with a diameter of 30-150 nm, play a critical role in intercellular communication and have become an ideal vehicle for drug delivery. A growing body of evidence suggests that exosomes have great potential for repairing SCI. In this review, we introduce exosome preparation, functions, and administration routes. In addition, we summarize the effect and mechanism by which various exosomes repair SCI and review the efficacy of exosomes in combination with other strategies to repair SCI. Finally, the challenges and prospects of the use of exosomes to repair SCI are described.

Unraveling the enigma of tumor-associated macrophages: challenges, innovations, and the path to therapeutic breakthroughs

Tumor-associated macrophages (TAMs) are integral to the tumor microenvironment (TME), influencing cancer progression significantly. Attracted by cancer cell signals, TAMs exhibit unparalleled adaptability, aligning with the dynamic tumor milieu. Their roles span from promoting tumor growth and angiogenesis to modulating metastasis. While substantial research has explored the fundamentals of TAMs, comprehending their adaptive behavior, and leveraging it for novel treatments remains challenging. This review delves into TAM polarization, metabolic shifts, and the complex orchestration of cytokines and chemokines determining their functions. We highlight the complexities of TAM-targeted research focusing on their adaptability and potential variability in therapeutic outcomes. Moreover, we discuss the synergy of integrating TAM-focused strategies with established cancer treatments, such as chemotherapy, and immunotherapy. Emphasis is laid on pioneering methods like TAM reprogramming for cancer immunotherapy and the adoption of single-cell technologies for precision intervention. This synthesis seeks to shed light on TAMs' multifaceted roles in cancer, pinpointing prospective pathways for transformative research and enhancing therapeutic modalities in oncology.

Functionally and Metabolically Divergent Melanoma-Associated Macrophages Originate from Common Bone-Marrow Precursors

Tumor-associated macrophages (TAMs) can be widely heterogeneous, based on their ontogeny and function, and driven by the tissue-specific niche. TAMs are highly abundant in the melanoma tumor microenvironment (TME), usually correlating with worse prognoses. However, the understanding of their diversity may be harnessed for therapeutic purposes. Here, we used the clinically relevant YUMM1.7 model to study melanoma TAM origin and dynamics during tumor progression. In i.d. YUMM1.7 tumors, we identified distinct TAM subsets based on F4/80 expression, with the F4/80^high fraction increasing over time and displaying a tissue-resident-like phenotype. While skin-resident macrophages showed mixed ontogeny, F4/80⁺ TAM subsets in the melanoma TME originated almost exclusively from bone-marrow precursors. A multiparametric analysis of the macrophage phenotype showed a temporal divergence of the F4/80⁺ TAM subpopulations, which also differed from the skin-resident subsets and their monocytic precursors. Overall, the F4/80⁺ TAMs displayed co-expressions of M1- and M2-like canonical markers, while RNA sequencing showed differential immunosuppressive and metabolic profiles. Gene-set enrichment analysis (GSEA) revealed F4/80^high TAMs to rely on oxidative phosphorylation, with increased proliferation and protein secretion, while F4/80^low cells had high pro-inflammatory and intracellular signaling pathways, with lipid and polyamine metabolism. Overall, we provide an in-depth characterization of and compelling evidence for the BM-dependency of melanoma TAMs. Interestingly, the transcriptomic analysis of these BM-derived TAMs matched macrophage subsets with mixed ontogeny, which have been observed in other tumor models. Our findings may serve as a guide for identifying potential ways of targeting specific immunosuppressive TAMs in melanoma.

Reprogramming tumor-associated macrophages as a unique approach to target tumor immunotherapy

In the last ten years, it has become increasingly clear that tumor-infiltrating myeloid cells drive not just carcinogenesis via cancer-related inflammatory processes, but also tumor development, invasion, and metastasis. Tumor-associated macrophages (TAMs) in particular are the most common kind of leucocyte in many malignancies and play a crucial role in establishing a favorable microenvironment for tumor cells. Tumor-associated macrophage (TAM) is vital as the primary immune cell subset in the tumor microenvironment (TME).In order to proliferate and spread to new locations, tumors need to be able to hide from the immune system by creating an immune-suppressive environment. Because of the existence of pro-tumoral TAMs, conventional therapies like chemotherapy and radiotherapy often fail to restrain cancer growth. These cells are also to blame for the failure of innovative immunotherapies premised on immune-checkpoint suppression. Understanding the series of metabolic changes and functional plasticity experienced by TAMs in the complex TME will help to use TAMs as a target for tumor immunotherapy and develop more effective tumor treatment strategies. This review summarizes the latest research on the TAMs functional status, metabolic changes and focuses on the targeted therapy in solid tumors.

Hematologic dysfunction in cancer: Mechanisms, effects on antitumor immunity, and roles in disease progression

With the major advances in cancer immunology and immunotherapy, it is critical to consider that most immune cells are short-lived and need to be continuously replenished from hematopoietic stem and progenitor cells. Hematologic abnormalities are prevalent in cancer patients, and many ground-breaking studies over the past decade provide insights into their underlying cellular and molecular mechanisms. Such studies demonstrate that the dysfunction of hematopoiesis is more than a side-effect of cancer pathology, but an important systemic feature of cancer disease. Here we review these many advances, covering the cancer-associated phenotypes of hematopoietic stem and progenitor cells, the dysfunction of myelopoiesis and erythropoiesis, the importance of extramedullary hematopoiesis in cancer disease, and the developmental origins of tumor associated macrophages. We address the roles of many secreted mediators, signaling pathways, and transcriptional and epigenetic mechanisms that mediate such hematopoietic dysfunction. Furthermore, we discuss the important contribution of the hematopoietic dysfunction to cancer immunosuppression, the possible avenues for therapeutic intervention, and highlight the unanswered questions and directions for future work. Overall, hematopoietic dysfunction is established as an active component of the cancer disease mechanisms and an important target for therapeutic intervention.

Targeting IL-34/MCSF-1R Axis in Colon Cancer

Colorectal carcinoma (CRC) is one of the most common neoplasias in the Western world and it is still one of the most deadly cancers worldwide mainly due to the fact that metastatic CRC is not responsive to current pharmacologic treatment. Identification of pathways that sustain CRC cell behaviour could help develop effective therapeutic compounds. A large body of evidence indicates that colon carcinogenesis is a dynamic process in which multiple cell types present in the tumor microenvironment either stimulate or suppress CRC cell growth, survival, and diffusion mainly via the production of cytokines. Interleukin-34 (IL-34), a cytokine initially known for its ability to regulate monocyte/macrophage survival and function, is highly produced in human CRC by both cancer cells and non-tumoral cells. IL-34 function is mainly mediated by interaction with the macrophage colony-stimulating factor-1 receptor (MCSF-1R), which is also over-expressed by CRC cells as well as by tumour-associated macrophages (TAMs) and cancer-associated fibroblasts. IL-34-driven MCSF-1R activation triggers several pro-tumoral functions in the colon. In this article, we review the current understanding of the involvement of IL-34 and its receptor in CRC, with particular attention to the available evidence about the IL-34/MCSF-1R axis-mediated regulation of TAMs and the role of IL-34 and MCSF-1R in promoting cancer resistance to chemotherapy and immunotherapy

Role of macrophages in tumor progression and therapy (Review)

The number and phenotype of macrophages are closely related to tumor growth and prognosis. Macrophages are recruited to (and polarized at) the tumor site thereby promoting tumor growth, stimulating tumor angiogenesis, facilitating tumor cell migration, and creating a favorable environment for subsequent colonization by (and survival of) tumor cells. These phenomena contribute to the formation of an immunosuppressive tumor microenvironment (TME) and therefore speed up tumor cell proliferation and metastasis and reduce the efficacy of antitumor factors and therapies. The ability of macrophages to remodel the TME through interactions with other cells and corresponding changes in their number, activity, and phenotype during conventional therapies, as well as the association between these changes and drug resistance, make tumor-associated macrophages a new target for antitumor therapies. In this review, advantages and limitations of the existing antitumor strategies targeting macrophages in Traditional Chinese and Western medicine were analyzed, starting with the effect of macrophages on tumors and their interactions with other cells and then the role of macrophages in conventional treatments was explored. Possible directions of future developments in this field from an all-around multitarget standpoint were also examined.

inlF Enhances Listeria monocytogenes Early-Stage Infection by Inhibiting the Inflammatory Response

The internalin family proteins, which carry the leucine repeat region structural motif, play diverse roles in Listeria monocytogenes (Lm) infection and pathogenesis. Although Internalin F, encoded by inlF, was identified more than 20 years ago, its role in the Lm anti-inflammatory response remains unknown. Lm serotype 4b isolates are associated with the majority of listeriosis outbreaks, but the function of InlF in these strains is not fully understood. In this study, we aimed to elucidate the role of inlF in modulating the inflammatory response and pathogenesis of the 4b strain Lm NTSN. Strikingly, although inlF was highly expressed at the transcriptional level during infection of five non-phagocytic cell types, it was not involved in adherence or invasion. Conversely, inlF did contributed to Lm adhesion and invasion of macrophages, and dramatically suppressed the expression of pro-inflammatory cytokines interleukin (IL)-1β and tumor necrosis factor (TNF-α). Consistent with the in vitro results, during Lm infection mice, inlF significantly inhibited the expression of IL-1β and IL-6 in the spleen, as well as IL-1β, IL-6, and TNF-α in the liver. More importantly, inlF contributed to Lm colonization in the spleen, liver, and ileum during the early stage of mouse infection via intragastric administration, inducing severe inflammatory injury and histopathologic changes in the late stage. To our knowledge, this is the first report to demonstrate that inlF mediates the inhibition of the pro-inflammatory response and contributes to the colonization and survival of Lm during the early stage of infection in mice. Our research partly explains the high pathogenicity of serovar 4b strains and will lead to new insights into the pathogenesis and immune evasion of Lm.

Abnormal histidine metabolism promotes macrophage lipid accumulation under Ox-LDL condition

Distinct macrophage populations exert highly heterogeneity and perform various functions, among which, a crucial function of lipid metabolism is highlighted. However, the role of histidine metabolism disorder in macrophage lipid metabolism remains elusive. Addressed this question, we sorted and cultured the bone marrow-derived macrophages (BMDMs) of histidine decarboxylase (Hdc) knockout (Hdc-/-) mice with an in vitro oxidized low-density lipoprotein (ox-LDL) model, and detected the intracellular lipids by Oil Red O staining as well as lipid probe staining. Astemizole, a canonical and long-acting histamine H1 receptor (H1R) antagonist, was applied to elucidate the impact of antagonizing the H1R-dependent signaling pathway on macrophage lipid metabolism. Subsequently, the differential expressed genes were screened and analyzed in the bone marrow-derived CD11b+ immature myeloid cells of Hdc-/- and Hdc+/+ mice with a high fat diet by the microarray study. The expression levels of cholesterol metabolism-related genes were examined by qRT-PCR to explore underlying mechanisms. Lastly, we used a high-sensitivity histidine probe to detect the intracellular histidine in the BMDMs after oxidative stress. The results revealed that histidine metabolism disorder and histamine deficiency aggravated lipid accumulation in the ox-LDL-treated BMDMs. The expression level of H1R gene in the BMDMs was down-regulated after ox-LDL stimulation. The disruption of the H1R-dependent signaling pathway by astemizole further exacerbated ox-LDL-induced lipid deposition in the BMDMs partly by up-regulating scavenger receptor class A (SR-A) for lipid intake, down-regulating neutral cholesteryl ester hydrolase (nCEH) for cholesterol esterification and down-regulating ATP-binding cassette transporters A1 (ABCA1) and ABCG1 for reverse cholesterol transport. The intracellular histidine increased under ox-LDL condition, which was further increased by Hdc knockout. Collectively, these results partially reveal the relationship between histidine metabolism and lipid metabolism in the BMDMs and offer a novel strategy for lipid metabolism disorder-associated diseases.

Role of macrophages in cancer progression and targeted immunotherapies

The vast complexity of the tumor microenvironment (TME) aggrandizes the underlying principles responsible for immune escape, therapy resistance, and treatment failure. The stromal and immune cell population circumjacent to the tumor cells affects the cancer cell cycle leading to tumor progression. Tumor-associated macrophages (TAMs) exhibiting a unique M2 polarization state constitute a significant portion of the TME. They serve as tumor suppressors at early stages and tumor promoters at advanced stages by governing various microenvironmental cues. TAMs secreted various pro-tumoral cytokines, chemokines, and matrix metalloproteases are known to regulate the different cell cycle molecules including checkpoint inhibitors in cancer cells leading to cell cycle progression with faulty cellular components. Moreover, TAMs are well-known immunosuppressors and thereby facilitating the tumor cells' evasion from immune recognition. This chapter will describe the interaction between TAMs and tumor cells, the involvement of TAMs in the regulation of cancer cell progression by controlling cell cycle checkpoints or molecular pathways, and current TAM-based therapies, including restriction of TAM recruitment, anti-survival strategies, or switching polarity. Moreover, this chapter will also emphasize recently developed drug targets and CAR-macrophage cell therapy that restricts tumor progression.

Irradiation Haematopoiesis Recovery Orchestrated by IL-12/IL-12Rβ1/TYK2/STAT3-Initiated Osteogenic Differentiation of Mouse Bone Marrow-Derived Mesenchymal Stem Cells

Purpose

Repairing the irradiation-induced osteogenic differentiation injury of bone marrow mesenchymal stem cells (BM-MSCs) is beneficial to recovering haematopoiesis injury in radiotherapy; however, its mechanism is elusive. Our study aimed to help meet the needs of understanding the effects of radiotherapy on BM-MSC osteogenic potential.

Methods and Materials

Balb/c mice and the BM-MSCs were used to evaluate the irradiation-induced osteogenic differentiation injury in vivo. The cellular and molecular characterization were applied to determine the mechanism for recovery of irradiation-derived haematopoiesis injuries.

Results

We report a functional role of IL-12 in acute irradiation hematopoietic injury recovery and intend to dissect the possible mechanisms through BM-MSC, other than the direct effect of IL-12 on hematopoietic stem and progenitor cells (HSPCs). Specifically, we show that early use of IL-12 enhanced the osteogenic differentiation of BM-MSCs through IL-12Rβ1/TYK2/STAT3 signaling; furthermore, IL-12 induced osteogenesis facilitated bone formation and irradiation hematopoiesis recovery when transplanted BM-MSCs in the femur of Balb/c mice. For the mechanism of action, we found that IL-12 receptor beta 1 (IL-12Rβ1) expression of irradiated BM-MSCs was upregulated rapidly, coincidentally consistent with early use of IL-12 induced osteogenic differentiation enhancement. IL-12Rβ1 and tyrosine kinase 2 gene (Tyk2) silencing experiments and phosphotyrosine of signal transducer and activator of transcription 3 (p-STAT3) suppression experiments indicated the IL-12Rβ1/TYK2/STAT3 signaling was essential in IL-12-induced osteogenic differentiation enhancement of BM-MSCs.

Conclusion

These findings suggested that IL-12 may exert BM-MSCs-based hematopoietic recovery by repairing osteogenic differentiation abilities damages through IL-12Rβ1/TYK2/STAT3 signaling pathway post-irradiation.