Combination of Cisplatin and Irradiation Induces Immunogenic Cell Death and Potentiates Postirradiation Anti-PD-1 Treatment Efficacy in Urothelial Carcinoma

Durable response to nivolumab rechallenge in a patient with metastatic clear cell renal cell carcinoma

Introduction

While immune checkpoint inhibitors represent the mainstream treatment for metastatic renal cell carcinoma, a standardized approach following immune checkpoint inhibitors remains unclear. We report a case of metastatic renal cell carcinoma treated with nivolumab rechallenge.

Case presentation

A 60-year-old male with metastatic melanoma was referred to the urology division due to right renal cancer. He was undergoing nivolumab treatment for metastatic melanoma. Radical nephrectomy revealed clear cell renal cell carcinoma, pT3a. Two months post-surgery, multiple metastases were identified. Despite subsequent administration of interferon-α, axitinib, and temsirolimus, the metastases progressed. Consequently, nivolumab rechallenge and palliative radiotherapy were initiated, resulting in a durable response for 20 months. However, disease progression occurred, and he died of cancer 4 years after nephrectomy.

Conclusion

This is the first report of nivolumab rechallenge in metastatic renal cell carcinoma. Although the utility remains unclear, this case suggests that some patients may benefit from nivolumab rechallenge.

Investigating cellular similarities and differences between upper tract urothelial carcinoma and bladder urothelial carcinoma using single-cell sequencing

Background

Upper tract urothelial carcinoma (UTUC) and bladder urothelial carcinoma (BLCA) both originate from uroepithelial tissue, sharing remarkably similar clinical manifestations and therapeutic modalities. However, emerging evidence suggests that identical treatment regimens may lead to less favorable outcomes in UTUC compared to BLCA. Therefore, it is imperative to explore molecular processes of UTUC and identify biological differences between UTUC and BLCA.

Methods

In this study, we performed a comprehensive analysis using single-cell RNA sequencing (scRNA-seq) on three UTUC cases and four normal ureteral tissues. These data were combined with publicly available datasets from previous BLCA studies and RNA sequencing (RNA-seq) data for both cancer types. This pooled analysis allowed us to delineate the transcriptional differences among distinct cell subsets within the microenvironment, thus identifying critical factors contributing to UTUC progression and phenotypic differences between UTUC and BLCA.

Results

scRNA-seq analysis revealed seemingly similar but transcriptionally distinct cellular identities within the UTUC and BLCA ecosystems. Notably, we observed striking differences in acquired immunological landscapes and varied cellular functional phenotypes between these two cancers. In addition, we uncovered the immunomodulatory functions of vein endothelial cells (ECs) in UTUC, and intercellular network analysis demonstrated that fibroblasts play important roles in the microenvironment. Further intersection analysis showed that MARCKS promote UTUC progression, and immunohistochemistry (IHC) staining revealed that the diverse expression patterns of MARCKS in UTUC, BLCA and normal ureter tissues.

Conclusion

This study expands our multidimensional understanding of the similarities and distinctions between UTUC and BLCA. Our findings lay the foundation for further investigations to develop diagnostic and therapeutic targets for UTUC.

Neoadjuvant Chemoradiotherapy Followed by Radical Cystectomy for Muscle-Invasive Bladder Cancer: Analysis of Efficacy and Safety in 119 Patients

INTRODUCTION

Cisplatin-based systemic chemotherapy is recommended as neoadjuvant treatment for muscle-invasive bladder cancer (MIBC) before radical cystectomy (RC). However, clinical challenges include the possibility of primary chemoresistance and limited feasibility in patients with renal impairment. This study investigated the efficacy and safety profiles of neoadjuvant chemoradiotherapy (NCRT) followed by RC.

MATERIALS AND METHODS

We retrospectively analyzed 119 patients with nonmetastatic MIBC, who were pathologically diagnosed with urothelial carcinoma and underwent NCRT before RC. The pathological response to NCRT was evaluated using RC specimens. Recurrence-free survival (RFS) and cancer-specific survival (CSS) were compared according to pathological responses to NCRT.

RESULTS

Of the 119 patients, 111 (93%) underwent RC; ypT0 and downstaging to ≤ypT1 were observed in 42 (38%) and 76 (68%) patients, respectively. In the multivariable analysis, smaller tumor size was independently associated with ypT0. During a median follow-up of 5.2 years, 28 (25%) patients developed recurrence and 22 (20%) died of bladder cancer after RC. The 5-year RFS and CSS rates were 75% and 80%, respectively. The 5-year RFS rates in patients with ypT0, ypTa/is/1, and ≥ypT2 were 87%, 87%, and 46%, respectively. Similarly, patients with ypT0 and ypTa/is/1 had more favorable CSS (90% and 87% at 5 years, respectively) than those with ≥ypT2 (60%, P = .001). None of the patients experienced ≥grade 4 adverse events related to NCRT or ≥grade 4 complications of RC.

CONCLUSIONS

This study demonstrated sufficient efficacy and safety profile of NCRT followed by RC. Chemoradiotherapy may be a helpful alternative for neoadjuvant treatment before RC.

Latest evidence on clinical outcomes and prognostic factors of advanced urothelial carcinoma in the era of immune checkpoint inhibitors: a narrative review

The management of advanced (locally advanced or metastatic) urothelial carcinoma has been revolutionized since pembrolizumab was introduced in 2017. Several prognostic factors for advanced urothelial carcinoma treated with pembrolizumab have been reported, including conventional parameters such as performance status and visceral (especially liver) metastasis, laboratory markers such as the neutrophil-to-lymphocyte ratio, sarcopenia, histological/genomic markers such as programmed cell death ligand 1 immunohistochemistry and tumor mutational burden, variant histology, immune-related adverse events, concomitant medications in relation to the gut microbiome, primary tumor site (bladder cancer versus upper tract urothelial carcinoma) and history/combination of radiotherapy. The survival time of advanced urothelial carcinoma has been significantly prolonged (or 'doubled' from 1 to 2 years) after the advent of pembrolizumab, which will be further improved with novel agents such as avelumab and enfortumab vedotin. This review summarizes the latest evidence on clinical outcomes and prognostic factors of advanced urothelial carcinoma in the contemporary era of immune checkpoint inhibitors.

Cisplatin-Based Combination Therapy for Enhanced Cancer Treatment

Cisplatin, a primary chemotherapeutic drug, is of great value in the realm of tumor treatment. However, its clinical efficacy is strictly hindered by issues, such as drug resistance, relapse, poor prognosis, and toxicity to normal tissue. Cisplatin-based combination therapy has garnered increasing attention in both preclinical and clinical cancer research for its ability to overcome resistance, reduce toxicity, and enhance anticancer effects. This review examines three primary co-administration strategies of cisplatin-based drug combinations and their respective advantages and disadvantages. Additionally, seven types of combination therapies involving cisplatin are discussed, focusing on their main therapeutic effects, mechanisms in preclinical research, and clinical applications. This review also discusses future prospects and challenges, aiming to offer guidance for the development of optimal cisplatin-based combination therapy regimens for improved cancer treatment.

The diverse effects of cisplatin on tumor microenvironment: Insights and challenges for the delivery of cisplatin by nanoparticles

Cisplatin is a well-known platinum-based chemotherapy medication that is widely utilized for some malignancies. Despite the direct cytotoxic consequences of cisplatin on tumor cells, studies in the recent decade have revealed that cisplatin can also affect different cells and their secretions in the tumor microenvironment (TME). Cisplatin has complex impacts on the TME, which may contribute to its anti-tumor activity or drug resistance mechanisms. These regulatory effects of cisplatin play a paramount function in tumor growth, invasion, and metastasis. This paper aims to review the diverse impacts of cisplatin and nanoparticles loaded with cisplatin on cancer cells and also non-cancerous cells in TME. The impacts of cisplatin on immune cells, tumor stroma, cancer cells, and also hypoxia will be discussed in the current review. Furthermore, we emphasize the challenges and prospects of using cisplatin in combination with other adjuvants and therapeutic modalities that target TME. We also discuss the potential synergistic effects of cisplatin with immune checkpoint inhibitors (ICIs) and other agents with anticancer potentials such as polyphenols and photosensitizers. Furthermore, the potential of nanoparticles for targeting TME and better delivery of cisplatin into tumors will be discussed.

Current trends in the promising immune checkpoint inhibition and radiotherapy combination for locally advanced and metastatic urothelial carcinoma

Locally advanced and metastatic urothelial carcinoma (UC) remains a challenging malignancy, though several novel therapeutic drugs have been developed in recent years. Over the past decade, immune checkpoint inhibitors (ICI) have shifted the paradigm of therapeutic strategies for UC; however, only a limited number of patients respond to ICI. Since radiotherapy (RT) is widely known to induce systemic immune activation, it may boost the efficacy of ICI. Conversely, RT also causes exhaustion of cytotoxic T cells, and the activation and recruitment of immunosuppressive cells; ICI may help overcome these immunosuppressive effects. Therefore, the combination of ICI and RT has attracted attention in recent years. The therapeutic benefits of this combination therapy and its optimal regimen have not yet been determined through prospective studies. Therefore, this review article aimed to provide an overview of the current preclinical and clinical studies that illustrate the underlying mechanisms and explore the optimization of the RT regimen along with the ICI and RT combination sequence. We also analyzed ongoing prospective studies on ICI and RT combination therapies for metastatic UC. We noted that the tumor response to ICI and RT combination seemingly differs among cancer types. Thus, our findings highlight the need for well-designed prospective trials to determine the optimal combination of ICI and RT for locally advanced and metastatic UC.

Selective multimodal bladder-sparing therapy for muscle-invasive bladder cancer: the present and the future

INTRODUCTION

Despite the lack of level 1 evidence, selective bladder-sparing therapy using trimodal therapy is currently recommended by guidelines as a standard of care in patients with non-metastatic, muscle-invasive bladder cancer who are eligible for the treatment.

AREAS COVERED

This article reviews major studies of selective, bladder-sparing therapy utilizing multiple modalities for muscle-invasive bladder cancer and those comparing the oncological outcomes between bladder-sparing therapy and radical cystectomy. Also discussed are predictive biomarkers potentially capable of guiding treatment decisions by patients with muscle-invasive bladder cancer and a novel strategy for boosting the antitumor immune response in bladder-sparing therapy. PubMed databases were searched for records of 30 June 2023 or earlier.

EXPERT OPINION

Selective, bladder-sparing therapy appears to be underutilized at present. To promote its use, measures should be taken to facilitate the referral of eligible patients to specialist centers and broaden the number of facilities providing the therapy. Recent studies have suggested a prognostic benefit of radiotherapy for the primary lesion in patients with metastatic bladder cancer. Given that irradiation can induce the abscopal effect, particularly in combination with immune checkpoint inhibitors, demand for bladder-sparing therapies may increase in the context of treatments for metastases.

Chemo-Immunotherapy: A New Trend in Cancer Treatment

Chemotherapy has been the basis of advanced cancer treatment for decades. This therapy has largely been considered immunosuppressive, yet accumulated preclinical and clinical evidence shows that certain chemotherapeutic drugs, under defined conditions, may stimulate antitumor immunity and potentiate immune checkpoint inhibitor (ICI)-based therapy. Its effectiveness has been highlighted by recent regulatory approvals of various combinations of chemotherapy with ICIs in several tumors, particularly in some difficult-to-treat cancers. This review discusses the immune modulatory properties of chemotherapy and how they may be harnessed to develop novel chemo-immunotherapy combinations. It also highlights the key determinants of the success of chemo-immunotherapy and provides an overview of the combined chemo-immunotherapies that have been clinically approved.

Chemotherapy to potentiate the radiation-induced immune response

Chemoradiation (CRT) is a conventional therapy used in local cancers, especially when they are locally advanced. Studies have shown that CRT induces strong anti-tumor responses involving several immune effects in pre-clinical models and humans. In this review, we have described the various immune effects involved in CRT efficacy. Indeed, effects such as immunological cell death, activation and maturation of antigen-presenting cells, and activation of an adaptive anti-tumor immune response are attributed to CRT. As often described in other therapies, various immunosuppressive mechanisms mediated, in particular, by Treg and myeloid populations may reduce the CRT efficacy. We have therefore discussed the relevance of combining CRT with other therapies to potentiate the CRT-induced anti-tumor effects.

Novel immunogenic cell death-related risk signature to predict prognosis and immune microenvironment in lung adenocarcinoma

PURPOSE

Immunogenic cell death (ICD) is a type of regulated cell death (RCD) which was discovered to activate adaptive immunity. To date, the effect of ICD on lung adenocarcinoma (LUAD) remains unclear. In this research, we will study the role of ICD-related genes (ICDG) in LUAD.

METHODS

RNA sequencing and clinical data were gathered from TCGA-LUAD cohorts and GEO database. Using unsupervised cluster analysis, three clusters were identified with distinctive immune characteristics and significant overall survival based on 18 ICDG. Using LASSO Cox regression, three genes were identified and used to construct the prognosis signature. The association between the 3-ICDG risk signature and immune microenvironment analysis, somatic mutation, and enriched molecular pathways was investigated.

RESULTS

Consensus clustering separated the LUAD samples into three clusters (ICDcluster A, B and C), and ICDcluster B had the best prognosis. Different TME cell infiltration characteristics and biological behavior were found in three ICD clusters. Prognostic risk model was contrasted based on the 3 best prognostic ICD-related genes. Subsequently, vitro experiments verified the above analysis results. The high-risk group showed a poor prognosis and enrichment of cancer promoting signal pathway. Multivariate analysis indicated that this 3-ICDG prognostic model might be an accurate prediction parameter for LUAD. Moreover, conducting immune related analysis, we found that the 3-ICDG risk signature was characterized by an immune-active subtype on account of the high infiltration of immune-active cells.

CONCLUSION

This study expands our cognition of ICD in LUAD microenvironment, excavated prognostic biomarkers, and provided potential value for guiding immunotherapy and chemotherapy.

Research progress in inducing immunogenic cell death of tumor cells

Immunogenic cell death (ICD) is a regulated cell death (RCD) pathway. In response to physical and chemical signals, tumor cells activate specific signaling pathways that stimulate stress responses in the endoplasmic reticulum (ER) and expose damage-associated molecular patterns (DAMPs), which promote antitumor immune responses. As a result, the tumor microenvironment is altered, and many tumor cells are killed. The ICD response in tumor cells requires inducers. These inducers can be from different sources and contribute to the development of the ICD either indirectly or directly. The combination of ICD inducers with other tumor treatments further enhances the immune response in tumor cells, and more tumor cells are killed; however, it also produces side effects of varying severity. New induction methods based on nanotechnology improve the antitumor ability and significantly reduces side effects because they can target tumor cells precisely. In this review, we introduce the characteristics and mechanisms of ICD responses in tumor cells and the DAMPs associated with ICD responses, summarize the current methods of inducing ICD response in tumor cells in five distinct categories: chemical sources, physical sources, pathogenic sources, combination therapies, and innovative therapies. At the same time, we introduce the limitations of current ICD inducers and make a summary of the use of ICD responses in clinical trials. Finally, we provide an outlook on the future of ICD inducer development and provide some constructive suggestions.

Impact of sarcopenia in bladder preservation therapy for muscle-invasive bladder cancer patients: a narrative review

BACKGROUND AND OBJECTIVE

Muscle-invasive bladder cancer (MIBC) is a biologically aggressive disease and its prognosis is poor. Radical cystectomy (RC) with urinary diversion and lymph node dissection is the gold standard treatment for MIBC patients. Accumulating evidence indicates that sarcopenia, the degenerative and systemic loss of skeletal muscle mass, is a significant predictor of higher rates of mortality and perioperative complications following RC. Recently, bladder preservation therapy has been offered as an alternative in appropriately selected MIBC patients who desire to preserve their bladders and those unfit or unwilling for RC. Here, we performed a narrative review on the impact of sarcopenia on oncological outcomes and complication rates in MIBC patients treated with bladder preservation therapy.

METHODS

A literature review was performed using the PubMed and Scopus databases.

KEY CONTENT AND FINDINGS

We identified two studies reported the impact of sarcopenia on responses to trimodal therapy and survival outcomes in MIBC patients. Consolidative partial cystectomy was performed in patients who achieved clinical complete response (CR) to trimodal therapy in one of the two studies. In both studies, CR rates to trimodal therapy are comparable between sarcopenic and non-sarcopenic patients. Sarcopenia was not significantly associated with shorter survival after completing bladder preservation therapy in either study. For complication rates of bladder preservation therapy, one study showed equivalent complication rates of consolidative partial cystectomy between sarcopenic and non-sarcopenic patients. In addition, in another small series of trimodal therapy, sarcopenic patients showed a higher rate of complications of trimodal therapy compared with non-sarcopenic patients.

CONCLUSIONS

According to the result of our literature review, sarcopenia would not affect responses to trimodal therapy and prognosis in MIBC patients treated with bladder preservation therapy. Although the effect of sarcopenia on complication rates of bladder preservation therapy is inconclusive due to limited evidence, bladder preservation therapy could be a viable alternative option in carefully selected MIBC patients regardless of the presence of sarcopenia.

Immunogenic Cell Death Role in Urothelial Cancer Therapy

Purpose: Bladder cancer is the 13th most common cause of cancer death with the highest lifetime cost for treatment of all cancers. This scoping review clarifies the available evidence on the role of a novel therapeutic approach called immunogenic cell death (ICD) in urothelial cancer of the bladder. Methods: In accordance with the recommendations of the Joanna Briggs Institute, we searched MEDLINE (Ovid), EMBASE, CENTRAL databases, and supplemented with manual searches through the conferences, Google scholar, and clinicaltrials.gov for published studies up to April 2022. We included literature that studied molecular mechanisms of ICD and the role of certain danger-associated molecular patterns (DAMPs) in generating ICD, safety and efficacy of different ICD inducers, and their contributions in combination with other urothelial cancer treatments. Results: Oncolytic viruses, radiotherapy, certain chemo/chemo radiation therapy combinations, photodynamic therapy, and novel agents were studied as ICD-inducing treatment modalities in the included studies. ICD was observed in vitro (murine or human urothelial carcinoma) in ten studies, eight studies were performed on mouse models (orthotopic or subcutaneous), and five clinical trials assessed patient response to ICD inducing agents. The most common studied DAMPs were Calreticulin, HMGB1, ATP, and Heat Shock Proteins (HSP) 70 and 90, which were either expressed on the cancer cells or released. Conclusion: ICD inducers were able to generate lasting antitumor immune responses with memory formation in animal studies (vaccination effect). In clinical trials these agents generally had low side effects, except for one trial, and could be used alone or in combination with other cancer treatment strategies in urothelial cancer patients.

Association of Cell Death Markers With Tumor Immune Cell Infiltrates After Chemo-Radiation in Cervical Cancer

Irradiation induces distinct cellular responses such as apoptosis, necroptosis, iron-dependent cell death (a feature of ferroptosis), senescence, and mitotic catastrophe. Several of these outcomes are immunostimulatory and may represent a potential for immunogenic type of cell death (ICD) induced by radiotherapy triggering abscopal effects. The purpose of this study is to determine whether intra-tumoral ICD markers can serve as biomarkers for the prediction of patient's outcomes defined as the metastasis status and survival over a 5-year period. Thirty-eight patients with locally advanced cervical cancer, treated with neoadjuvant chemoradiotherapy using cisplatin were included in this study. Pre-treatment tumor biopsy and post-treatment hysterectomy samples were stained for cell death markers and danger associated molecular patterns (DAMPs): cleaved caspase-3 (apoptosis), phosphorylated mixed lineage kinase domain like pseudokinase (pMLKL; necroptosis), glutathione peroxidase 4 (GPX4; ferroptosis) and 4-hydroxy-2-noneal (4-HNE; ferroptosis), high mobility group box 1 (HMGB1) and calreticulin. Although these markers could not predict the patient's outcome in terms of relapse or survival, many significantly correlated with immune cell infiltration. For instance, inducing ferroptosis post-treatment seems to negatively impact immune cell recruitment. Measuring ICD markers could reflect the impact of treatment on the tumor microenvironment with regard to immune cell recruitment and infiltration.

One Sentence Summary

Cell death readouts during neoadjuvant chemoradiation in cervical cancer.

Neoadjuvant Immunotherapy in Gastrointestinal Cancers - The New Standard of Care?

The development of immune checkpoint inhibitors (ICI) offers novel treatment possibilities for solid cancers, with the crucial benefit of providing higher cure rates. These agents have become part of standard treatments in the metastatic and adjuvant setting for select cancers, such as melanoma, non-small cell lung cancer (NSCLC) or urological malignancies. Currently, there is ample clinical interest in employing ICI in a neoadjuvant setting with a curative intent. This approach is especially supported by the scientific rationale that ICI primarily stimulate the host immune system to eradicate tumor cells, rather than being inherently cytotoxic. Aside from tumor downstaging, neoadjuvant immunotherapy offers the potential of an in situ cancer vaccination, leading to a systemic adjuvant immunological effect after tumor resection. Moreover, preclinical data clearly demonstrate a synergistic effect of ICI with radiotherapy (RT), chemoradiotherapy (CRT) or chemotherapy (ChT). This review harmonizes preclinical concepts with real world data (RWD) in the field of neoadjuvant ICI in gastrointestinal (GI) cancers and discusses their limitations. We believe this is a crucial approach, since up to now, neoadjuvant strategies have been primarily developed by clinicians, whereas the advances in immunotherapy primarily originate from preclinical research. Currently there is limited published data on neoadjuvant ICI in GI cancers, even though neoadjuvant treatments including RT, CRT or ChT are frequently employed in locally advanced/oligometastatic GI cancers (i.e. rectal, pancreatic, esophagus, stomach, etc.). Utilizing established therapies in combination with ICI provides an abundance of opportunities for innovative treatment regimens to further improve survival rates.

Spatial Distribution and Predictive Significance of Dendritic Cells and Macrophages in Esophageal Cancer Treated With Combined Chemoradiotherapy and PD-1 Blockade

Background

The first clinical study (NCT03671265) of first-line chemoradiotherapy combined with PD-1 blockade showed promising treatment outcomes in locally advanced esophageal squamous cell carcinoma (ESCC). However, partial patients did not respond to the combination treatment. The roles of dendritic cells (DCs) and macrophages in this combination treatment remain poorly understood.

Methods

We performed multiplexed immunofluorescence method to identify CD11c⁺ DCs, CD68⁺ macrophages, and their PD-L1^- or PD-L1⁺ subpopulations in paired tumor biopsies (n = 36) collected at baseline and during the combination treatment (after radiation, 40 Gy) from the phase Ib trial (NCT03671265). We applied whole exome sequencing in the baseline tumor biopsies (n = 14) to estimate tumor mutation burden (TMB). We dynamically investigated the spatial distribution of DCs and macrophages under chemoradiotherapy combined with PD-1 blockade, and evaluated the association between their spatial distribution and combination outcome, and TMB.

Results

The results showed that high percentages of PD-L1^- DCs and macrophages in the baseline tumor compartment, but not in the stromal compartment, predicted improved OS and PFS. Chemoradiotherapy combined with PD-1 blockade promoted DCs and macrophages to migrate closer to tumor cells. During combination treatment, PD-L1^- tumor cells were nearest to PD-L1^- DCs and macrophages, while PD-L1⁺ tumor cells were next to PD-L1⁺ DCs and macrophages. High TMB was closely associated with a shorter distance from tumor cells to DCs and macrophages. Shorter distance between PD-L1⁺ tumor cells and PD-L1⁺ DCs or PD-L1^- macrophages during the combination was correlated with better OS. Shorter distance between PD-L1^- tumor cells and PD-L1^- macrophages during combination was associated with both longer OS and PFS.

Conclusions

PD-L1^- or PD-L1⁺ DCs and macrophages exhibit distinct spatial distribution in ESCC. The close distance between tumor cells and these antigen-presenting cells (APCs) is critical to the clinical outcome in chemoradiotherapy combined with PD-1 blockade in ESCC patients. Our results highlight the predictive potential of spatial patterns of APCs in chemoradiotherapy combined with immunotherapy and reveal the underlying mechanism of APCs participating in chemoradiotherapy-induced antitumor immune response in ESCC.

The role of tumor-associated macrophages in osteosarcoma progression - therapeutic implications

BACKGROUND

Osteosarcoma (OS) is the most common primary malignant bone tumor. Compared with previous treatment modalities, such as amputation, more recent comprehensive treatment modalities based on neoadjuvant chemotherapy combined with limb salvage surgery have improved the survival rates of patients. Osteosarcoma treatment has, however, not further improved in recent years. Therefore, attention has shifted to the tumor microenvironment (TME) in which osteosarcoma cells are embedded. Therapeutic targets in the TME may be key to improving osteosarcoma treatment. Tumor-associated macrophages (TAMs) are the most common immune cells within the TME. TAMs in osteosarcoma may account for over 50% of the immune cells, and may play important roles in tumorigenesis, angiogenesis, immunosuppression, drug resistance and metastasis. Knowledge on the role of TAMs in the development, progression and treatment of osteosarcoma is gradually improving, although different or even opposing opinions still remain.

CONCLUSIONS

TAMs may participate in the malignant progression of osteosarcoma through self-polarization, the promotion of blood vessel and lymphatic vessel formation, immunosuppression, and drug resistance. Besides, various immune checkpoint proteins expressed on the surface of TAMs, such as PD-1 and CD47, provide the possibility of the application of immune checkpoint inhibitors. Several clinical trials have been carried out and/or are in progress. Mifamotide and the immune checkpoint inhibitor Camrelizumab were both found to be effective in prolonging progression-free survival. Thus, TAMs may serve as attractive therapeutic targets. Targeting TAMs as a complementary therapy is expected to improve the prognosis of osteosarcoma. Further efforts may be made to identify potential beneficiaries of TAM-targeted therapies.