Bone metastasis is associated with acquisition of mesenchymal phenotype and immune suppression in a model of spontaneous breast cancer metastasis

Combining TIGIT Blockade with MDSC Inhibition Hinders Breast Cancer Bone Metastasis by Activating Antitumor Immunity

Bone is the most common site of breast cancer metastasis. Bone metastasis is incurable and is associated with severe morbidity. Utilizing an immunocompetent mouse model of spontaneous breast cancer bone metastasis, we profiled the immune transcriptome of bone metastatic lesions and peripheral bone marrow at distinct metastatic stages, revealing dynamic changes during the metastatic process. We show that cross-talk between granulocytes and T cells is central to shaping an immunosuppressive microenvironment. Specifically, we identified the PD-1 and TIGIT signaling axes and the proinflammatory cytokine IL1β as central players in the interactions between granulocytes and T cells. Targeting these pathways in vivo resulted in attenuated bone metastasis and improved survival, by reactivating antitumor immunity. Analysis of patient samples revealed that TIGIT and IL1β are prominent in human bone metastasis. Our findings suggest that cotargeting immunosuppressive granulocytes and dysfunctional T cells may be a promising novel therapeutic strategy to inhibit bone metastasis. Significance: Temporal transcriptome profiling of the immune microenvironment in breast cancer bone metastasis revealed key communication pathways between dysfunctional T cells and myeloid derived suppressor cells. Cotargeting of TIGIT and IL1β inhibited bone metastasis and improved survival. Validation in patient data implicated these targets as a novel promising approach to treat human bone metastasis.

Unique macrophage phenotypes activated by BMP signaling in breast cancer bone metastases

Metastatic breast cancer (mBC) tissue in bone was systematically profiled to define the composition of the tumor microenvironment. Gene expression identified a high myeloid signature of patients with improved survival outcomes. Bone metastases were profiled by spatial proteomics to examine myeloid populations within the stroma that correlated with macrophage functions. Single-cell spatial analysis uncovered macrophage activation in the stroma of mBC bone lesions. Matched BC patient samples of primary breast tumor and bone metastasis tissues were compared for gene expression in the bone, where bone morphogenetic protein 2 (BMP2) was most significantly upregulated. Immune cell changes from breast to bone demonstrated a loss of lymphoid cells but a consistent population of macrophages. BMP-activated macrophages were increased uniquely in bone. Bone marrow-derived macrophage activation coupled with BMP inhibition increased inflammatory responses. Using experimental mouse models of mBC bone metastasis and trained immunity, we found that BMP inhibition restricts progression of metastases early in the macrophage activation state but not after tumors were established in the bone. This study revealed unique myeloid BMP activation states that are distinctly integrated with bone metastases.

Challenges and Future Directions in the Management of Tumor Mutational Burden-High (TMB-H) Advanced Solid Malignancies

A standardized assessment of Tumor Mutational Burden (TMB) poses challenges across diverse tumor histologies, treatment modalities, and testing platforms, requiring careful consideration to ensure consistency and reproducibility. Despite clinical trials demonstrating favorable responses to immune checkpoint inhibitors (ICIs), not all patients with elevated TMB exhibit benefits, and certain tumors with a normal TMB may respond to ICIs. Therefore, a comprehensive understanding of the intricate interplay between TMB and the tumor microenvironment, as well as genomic features, is crucial to refine its predictive value. Bioinformatics advancements hold potential to improve the precision and cost-effectiveness of TMB assessments, addressing existing challenges. Similarly, integrating TMB with other biomarkers and employing comprehensive, multiomics approaches could further enhance its predictive value. Ongoing collaborative endeavors in research, standardization, and clinical validation are pivotal in harnessing the full potential of TMB as a biomarker in the clinic settings.

A global bibliometric and visualized analysis of the status and trends of bone metastasis in breast cancer research from 2002 to 2021

Bone metastasis of breast cancer considerably reduces not only overall survival but also health-related quality of life due to pain, fatigue, and skeletal-related events.

OBJECTIVE

This study aims to analyze the research hotspots and trends of global research on bone metastasis of breast cancer in the past 20 years to provide a reference for relevant personnel in this field to carry out academic research.

METHODS

The literature related to bone metastasis of breast cancer from 2002 to 2021 was retrieved from the Web of Science. The bibliometric research method and VOSviewer and CiteSpace were used to analyze the publications, and the research status and development direction in the last 20 years were visualized.

RESULTS

A total of 7381 articles were included. The number of global publications is increasing every year. The United States contributes the most to global research, with the most citations and the highest H-index. The journal Cancer Research published the most articles on this issue. "Macrophage" and "skeletal related event" will receive more attention and be the next popular hotspot in the future.

CONCLUSION

There will be an increasing number of publications on bone metastasis of breast cancer based on current global trends. The United States made the largest contribution to this field. More focus will be placed on the mechanisms of metastasis research, which may be the next popular topic in bone metastasis of breast cancer.

The relationship between the Hippo signaling pathway and bone metastasis of breast cancer

Bone is the most common site of metastasis from breast cancer, which is the most prevalent cancer affecting women globally. Bone metastasis from breast cancer severely affects the quality of life of patients and increases mortality. The molecular mechanisms of metastasis, colonization, and proliferation of breast cancer cells in bone are complex and involve the interaction between breast cancer cells and the bone microenvironment. However, the precise mechanism is not clear at present. In recent years, the Hippo signaling pathway has attracted much attention due to its important role in regulating the expression of major effector molecules during tumor development. In particular, studies have found that the mutation and aberrant expression of the core components of the Hippo signaling pathway affect breast cancer cell migration and invasion, indicating that this pathway plays a role in bone metastasis, although the molecular mechanism of this pathway in breast cancer metastasis has not been fully elucidated. In this review, we discuss the function of the Hippo signaling pathway, introducing its role in breast cancer metastasis, especially bone metastasis of breast cancer, so as to lay a solid theoretical foundation for further research and for the development of effective targeted therapeutic agents.

Locally sourced: site-specific immune barriers to metastasis

Tumour cells migrate very early from primary sites to distant sites, and yet metastases often take years to manifest themselves clinically or never even surface within a patient's lifetime. This pause in cancer progression emphasizes the existence of barriers that constrain the growth of disseminated tumour cells (DTCs) at distant sites. Although the nature of these barriers to metastasis might include DTC-intrinsic traits, recent studies have established that the local microenvironment also controls the formation of metastases. In this Perspective, I discuss how site-specific differences of the immune system might be a major selective growth restraint on DTCs, and argue that harnessing tissue immunity will be essential for the next stage in immunotherapy development that reliably prevents the establishment of metastases.

TOR1B: a predictor of bone metastasis in breast cancer patients

Recent therapeutic advances in breast cancer (BC) have improved survival outcomes; however, the prognosis for patients with bone metastasis (BM) remains poor. Hence, novel clinical biomarkers are needed to accurately predict BC BM as well as to promote personalized medicine. Here, we discovered a novel biomarker, TOR1B, for BM in BC patients via analysis of BC gene expression data and clinical information downloaded from open public databases. In cancer cells, we found high expression levels of TOR1B in the nucleus and endoplasmic reticulum. Regarding gene expression, the level of TOR1B was significantly upregulated in BC patients with BM (p < 0.05), and the result was externally validated. In addition, gene expression clearly demonstrated two distinct types of prognoses in ER- and PR-positive patients. In multivariate regression, the gene could be an independent predictor of BM in BC patients, i.e., a low expression level of TOR1B was associated with delayed metastasis to bone in BC patients (HR, 0.28; 95% CI 0.094-0.84). Conclusively, TOR1B might be a useful biomarker for predicting BM; specifically, patients with ER- and PR-positive subtypes would benefit from the clinical use of this promising prognostic biomarker.

SFRP2 Overexpression Induces an Osteoblast-like Phenotype in Prostate Cancer Cells

Prostate cancer bone metastasis is still one of the most fatal cancer diagnoses for men. Survival of the circulating prostate tumor cells and their adaptation strategy to survive in the bone niche is the key point to determining metastasis in early cancer stages. The promoter of SFRP2 gene, encoding a WNT signaling modulator, is hypermethylated in many cancer types including prostate cancer. Moreover, SFRP2 can positively regulate osteogenic differentiation in vitro and in vivo. Here, we showed SFRP2 overexpression in the prostate cancer cell line PC3 induces an epithelial mesenchymal transition (EMT), increases the attachment, and modifies the transcriptome towards an osteoblast-like phenotype (osteomimicry) in a collagen 1-dependent manner. Our data reflect a novel molecular mechanism concerning how metastasizing prostate cancer cells might increase their chance to survive within bone tissue.

Muscle and Bone Defects in Metastatic Disease

PURPOSE OF REVIEW

The present review addresses most recently identified mechanisms implicated in metastasis-induced bone resorption and muscle-wasting syndrome, known as cachexia.

RECENT FINDINGS

Metastatic disease in bone and soft tissues is often associated with skeletal muscle defects. Recent studies have identified a number of secreted molecules and extracellular vesicles that contribute to cancer cell growth and metastasis leading to bone destruction and muscle atrophy. In addition, alterations in muscle microenvironment including dysfunctions in hepatic and mitochondrial metabolism have been implicated in cancer-induced regeneration defect and muscle loss. Moreover, we review novel in vitro and animal models including promising new drug candidates for bone metastases and cancer cachexia. Preservation of bone health could be highly beneficial for maintaining muscle mass and function. Therefore, a better understanding of molecular pathways implicated in bone and muscle crosstalk in metastatic disease may provide new insights and identify new strategies to improve current anticancer therapeutics.

Nomogram Models Based on the Gene Expression in Prediction of Breast Cancer Bone Metastasis

Objective

The aim of this study is to design a weighted co-expression network and build gene expression signature-based nomogram (GESBN) models for predicting the likelihood of bone metastasis in breast cancer (BC) patients.

Methods

Dataset GSE124647 was used as a training set, while GSE16446, GSE45255, and GSE14020 were taken as validation sets. In the training cohort, the limma package in R was adopted to obtain differentially expressed genes (DEGs) between BC nonbone metastasis and bone metastasis patients, which were used for functional enrichment analysis. After weighted co-expression network analysis (WGCNA), univariate Cox regression and Kaplan–Meier plotter analyses were performed to screen potential prognosis-related genes. Then, GESBN models were constructed and evaluated. The prognostic value of the GESBN models was investigated in the GSE124647 dataset, which was validated in GSE16446 and GSE45255 datasets. Further, the expression levels of genes in the models were explored in the training set, which was validated in GSE14020. Finally, the expression and prognostic value of hub genes in BC were explored.

Results

A total of 1858 DEGs were obtained. The WGCNA result showed that the blue module was most significantly related to bone metastasis and prognosis. After survival analyses, GAJ1, SLC24A3, ITGBL1, and SLC44A1 were subjected to construct a GESBN model for overall survival (OS). While GJA1, IGFBP6, MDFI, TGFBI, ANXA2, and SLC24A3 were subjected to build a GESBN model for progression-free survival (PFS). Kaplan–Meier plotter and receiver operating characteristic analyses presented the reliable prediction ability of the models. Cox regression analysis further revealed that GESBN models were independent prognostic predictors for OS and PFS in BC patients. Besides, GJA1, IGFBP6, ITGBL1, SLC44A1, and TGFBI expressions were significantly different between the two groups in GSE124647 and GSE14020. The hub genes had a significant impact on patient prognosis.

Conclusion

Both the four-gene signature and six-gene signature could accurately predict patient prognosis, which may provide novel treatment insights for BC bone metastasis.

Macrophage-mediated anti-tumor immunity against high-risk neuroblastoma

Neuroblastoma is the most common extracranial childhood solid tumor. The majority of high-risk neuroblastoma is resistant/refractory to the current high intensity therapy. Neuroblastoma lacks classical HLA Class I expression and exhibits low mutation burden, allowing neuroblastoma cells to evade CD8+ T cell-mediated immunity. Neuroblastoma cells do not express PD-L1, and tumor-associated macrophages are the predominant PD-L1+ cells in the tumor. In this study, we performed gene expression profiling and survival analyses on large neuroblastoma datasets to address the prognostic effect of PD-L1 gene expression and the possible involvement of the SLAMF7 pathway in the anti-neuroblastoma immunity. High-level expression of PD-L1 was found significantly associated with better outcome of high-risk neuroblastoma patients; two populations of PD-1+ PD-L1+ macrophages could be present in high-risk tumors with PD-1/PD-L1 ratios, ≈1 and >1. Patients with the PD-1/PD-L1 ratio >1 tumor showed inferior survival. High-level co-expression of SLAMF7 and SH2D1B was significantly associated with better survival of the high-risk neuroblastoma patients. Together, this study supports the hypothesis that macrophages are important effector cells in the anti-high-risk neuroblastoma immunity, that PD-1 blockade therapy can be beneficial to the high-risk neuroblastoma subset with the PD-1/PD-L1 expression ratio >1, and that SLAMF7 is a new therapeutic target of high-risk neuroblastoma.

Diagnosis of bone metastases in breast cancer: Lesion-based sensitivity of dual-time-point FDG-PET/CT compared to low-dose CT and bone scintigraphy

We compared lesion-based sensitivity of dual-time-point FDG-PET/CT, bone scintigraphy (BS), and low-dose CT (LDCT) for detection of various types of bone metastases in patients with metastatic breast cancer. Prospectively, we included 18 patients with recurrent breast cancer who underwent dual-time-point FDG-PET/CT with LDCT and BS within a median time interval of three days. A total of 488 bone lesions were detected on any of the modalities and were categorized by the LDCT into osteolytic, osteosclerotic, mixed morphologic, and CT-negative lesions. Lesion-based sensitivity was 98.2% (95.4-99.3) and 98.8% (96.8-99.5) for early and delayed FDG-PET/CT, respectively, compared with 79.9% (51.1-93.8) for LDCT, 76.0% (36.3-94.6) for BS, and 98.6% (95.4-99.6) for the combined BS+LDCT. BS detected only 51.2% of osteolytic lesions which was significantly lower than other metastatic types. SUVs were significantly higher for all lesion types on delayed scans than on early scans (P<0.0001). Osteolytic and mixed-type lesions had higher SUVs than osteosclerotic and CT-negative metastases at both time-points. FDG-PET/CT had significantly higher lesion-based sensitivity than LDCT and BS, while a combination of the two yielded sensitivity comparable to that of FDG-PET/CT. Therefore, FDG-PET/CT could be considered as a sensitive one-stop-shop in case of clinical suspicion of bone metastases in breast cancer patients.

A glitch in the matrix: organ-specific matrisomes in metastatic niches

Modification of the extracellular matrix (ECM) is a critical aspect of developing a metastasis-supportive organ niche. Recent work investigating ECM changes that facilitate metastasis has revealed ways in which different metastatic organ niches are similar as well as the distinct characteristics that make them unique. In this review, we present recent findings regarding how ECM modifications support metastasis in four frequent metastatic sites: the lung, liver, bone, and brain. We discuss ways in which these modifications are shared between metastatic organs as well as features specific to each location. We also discuss areas of technical innovation that could be advantageous to future research and areas of inquiry that merit further investigation.

Modulating cell differentiation in cancer models

Cancer has been traditionally viewed as a disease characterised by excessive and uncontrolled proliferation, leading to the development of cytotoxic therapies against highly proliferating malignant cells. However, tumours frequently relapse due to the presence of slow-cycling cancer stem cells eluding chemo and radiotherapy. Since these malignant stem cells are largely undifferentiated, inducing their lineage commitment has been proposed as a potential intervention strategy to deplete tumours from their most resistant components. Pro-differentiation approaches have thus far yielded clinical success in the reversion of acute promyelocytic leukaemia (APL), and new developments are fast widening their therapeutic applicability to solid carcinomas. Recent advances in cancer differentiation discussed here highlight the potential and outstanding challenges of differentiation-based approaches.

Breast Cancer with Bone Metastasis: Molecular Insights and Clinical Management

Despite the remarkable advances in the diagnosis and treatment of breast cancer patients, the presence or development of metastasis remains an incurable condition. Bone is one of the most frequent sites of distant dissemination and negatively impacts on patient's survival and overall frailty. The interplay between tumor cells and the bone microenvironment induces bone destruction and tumor progression. To date, the clinical management of bone metastatic breast cancer encompasses anti-tumor systemic therapies along with bone-targeting agents, aimed at slowing bone resorption to reduce the risk of skeletal-related events. However, their effect on patients' survival remains controversial. Unraveling the biology that governs the interplay between breast neoplastic cells and bone tissue would provide means for the development of new therapeutic agents. This article outlines the state-of-the art in the characterization and targeting the bone metastasis in breast cancer, focusing on the major clinical and translational studies on this clinically relevant topic.

The past, present, and future of breast cancer models for nanomedicine development

Even given recent advances in nanomedicine development of breast cancer treatment in recent years and promising results in pre-clinical models, cancer nanomedicines often fail at the clinical trial stage. Limitations of conventional in vitro models include the lack of representation of the stromal population, the absence of a three-dimensional (3D) structure, and a poor representation of inter-tumor and intra-tumor heterogeneity. Herein, we review those cell culture strategies that aim to overcome these limitations, including cell co-cultures, advanced 3D cell cultures, patient-derived cells, bioprinting, and microfluidics systems. The in vivo evaluation of nanomedicines must consider critical parameters that include the enhanced permeability and retention effect, the host's immune status, and the site of tumor implantation. Here, we critically discuss the advantages and limitations of current in vivo models and report how the improved selection and application of breast cancer models can improve the clinical translation of nanomedicines.

How to Target Spinal Metastasis in Experimental Research: An Overview of Currently Used Experimental Mouse Models and Future Prospects

The spine is one of the organs that is most affected by metastasis in cancer patients. Since the control of primary tumor is continuously improving, treatment of metastases is becoming one of the major challenges to prevent cancer-related death. Due to the anatomical proximity to the spinal cord, local spread of metastasis can directly cause neurological deficits, severely limiting the patient’s quality of life. To investigate the underlying mechanisms and to develop new therapies, preclinical models are required which represent the complexity of the multistep cascade of metastasis. Current research of metastasis focuses on the formation of the premetastatic niche, tumor cell dormancy and the influence and regulating function of the immune system. To unveil whether these influence the organotropism to the spine, spinal models are irreplaceable. Mouse models are one of the most suitable models in oncologic research. Therefore, this review provides an overview of currently used mouse models of spinal metastasis. Furthermore, it discusses technical aspects clarifying to what extend these models can picture key steps of the metastatic process. Finally, it addresses proposals to develop better mouse models in the future and could serve as both basis and stimulus for researchers and clinicians working in this field.

Immune Responses against Disseminated Tumor Cells

Most cancer-related deaths are a consequence of metastases, a series of linear events, notably the invasion-metastasis cascade. The current understanding of cancer immune surveillance derives from studies in primary tumors, but disseminated cancer cells acquire mutations and, in some cases, appear to progress independently after spreading from primary sites. An early step in this process is micrometastatic dissemination. As such, the equilibrium between the immune system and disseminated cancer cells controls the fate of the cancer. Immune checkpoint inhibitors (ICIs) exhibit significant clinical activity in patients, but the efficacy of ICIs depends on both the tumor and its microenvironment. Data often suggest that disseminated cancer cells are not adequately targeted by the immune system. In this review, we summarize the main basic findings of immune responses against disseminated tumor cells and their organ-specific characteristics. Such studies may provide new directions for cancer immune therapy.

The Role of Inflammation in Breast and Prostate Cancer Metastasis to Bone

Tumor metastasis to bone is a common event in multiple forms of malignancy. Inflammation holds essential functions in homeostasis as a defense mechanism against infections and is a strategy to repair injured tissue and to adapt to stress conditions. However, exaggerated and/or persistent (chronic) inflammation may eventually become maladaptive and evoke diseases such as autoimmunity, diabetes, inflammatory tissue damage, fibrosis, and cancer. In fact, inflammation is now considered a hallmark of malignancy with prognostic relevance. Emerging studies have revealed a central involvement of inflammation in several steps of the metastatic cascade of bone-homing tumor cells through supporting their survival, migration, invasion, and growth. The mechanisms by which inflammation favors these steps involve activation of epithelial-to-mesenchymal transition (EMT), chemokine-mediated homing of tumor cells, local activation of osteoclastogenesis, and a positive feedback amplification of the protumorigenic inflammation loop between tumor and resident cells. In this review, we summarize established and evolving concepts of inflammation-driven tumorigenesis, with a special focus on bone metastasis.

Post-transcriptional repression of circadian component CLOCK regulates cancer-stemness in murine breast cancer cells

Disruption of the circadian clock machinery in cancer cells is implicated in tumor malignancy. Studies on cancer therapy reveal the presence of heterogeneous cells, including breast cancer stem-like cells (BCSCs), in breast tumors. BCSCs are often characterized by high aldehyde dehydrogenase (ALDH) activity, associated with the malignancy of cancers. In this study, we demonstrated the negative regulation of ALDH activity by the major circadian component CLOCK in murine breast cancer 4T1 cells. The expression of CLOCK was repressed in high-ALDH-activity 4T1, and enhancement of CLOCK expression abrogated their stemness properties, such as tumorigenicity and invasive potential. Furthermore, reduced expression of CLOCK in high-ALDH-activity 4T1 was post-transcriptionally regulated by microRNA: miR-182. Knockout of miR-182 restored the expression of CLOCK, resulted in preventing tumor growth. Our findings suggest that increased expression of CLOCK in BCSCs by targeting post-transcriptional regulation overcame stemness-related malignancy and may be a novel strategy for breast cancer treatments.