Matrix metalloproteinase-9 is required for tumor vasculogenesis but not for angiogenesis: role of bone marrow-derived myelomonocytic cells

ESMO-ESTRO framework for assessing the interactions and safety of combining radiotherapy with targeted cancer therapies or immunotherapy

With the emergence of targeted therapies and immunotherapy, various cellular pathways are utilized to improve tumor control and patient survival. In patients receiving these new agents, radiotherapy is commonly applied with both radical and palliative intent. Combining radiotherapy with targeted therapies or immunotherapy may improve treatment outcomes, but may also lead to increased toxicity. High-quality toxicity data and evidence-based guidelines regarding combined therapy are very limited. The present framework, developed by ESMO and ESTRO, explores the main biological effects and interaction mechanisms of radiotherapy combined with targeted agents or immunotherapy. It addresses general clinical factors to take into consideration when deciding on whether and/or how to combine radiotherapy with these agents. Furthermore, it provides pragmatic, biological mechanism-based clinical considerations for combining radiotherapy with various targeted agents or immunotherapy.

Exploring molecular and cellular mechanisms of Pre-Metastatic niche in renal cell carcinoma

Renal cell carcinoma (RCC) is among the most frequently occurring types of cancer, and its metastasis is a major contributor to its elevated mortality. Before the primary tumor metastasizes to secondary or distant organs, it remodels the microenvironment of these sites, creating a pre-metastatic niche (PMN) conducive to the colonization and growth of metastatic tumors. RCC releases a variety of biomolecules that induce angiogenesis, alter vascular permeability, modulate immune cells to create an immunosuppressive microenvironment, affect extracellular matrix remodeling and metabolic reprogramming, and determine the organotropism of metastasis through different signaling pathways. This review summarizes the principal processes and mechanisms underlying the formation of the premetastatic niche in RCC. Additionally, we emphasize the significance and potential of targeting PMNs for the prevention and treatment of tumor metastasis in future therapeutic approaches. Finally, we summarized the currently potential targeted strategies for detecting and treating PMN in RCC and provide a roadmap for further in-depth studies on PMN in RCC.

The epigenetic hallmarks of immune cells in cancer

Targeting the dysregulation of epigenetic mechanisms in cancer has emerged as a promising therapeutic strategy. Although the significant rationale progress of epigenetic therapies in blocking cancer cells, how epigenetic regulation shapes tumor microenvironment (TME) and establishes antitumor immunity remains less understood. Recent study focus has been put on the epigenetic-mediated changes in the fate of immune cells, including the differentiation, expansion, recruitment, functionalization, and exhaustion of T cells, natural killer (NK) cells, tumor-associated macrophages (TAMs), dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs), and B cells within the TME. Here, we review the latest molecular and clinical insights into how DNA modifications, histone modification, and epitranscriptome-related regulations shape immune cells of various cancers. We also discuss opportunities for leveraging epigenetic therapies to improve cancer immunotherapies. This review provides the epigenetic foundations of cancer immunity and proposes the future direction of combination therapies.

Metalloproteinases are involved in the regulation of prenatal tooth morphogenesis

During development, tooth germs undergo various morphological changes resulting from interactions between the oral epithelium and ectomesenchyme. These processes are influenced by the extracellular matrix, the composition of which, along with cell adhesion and signaling, is regulated by metalloproteinases. Notably, these include matrix metalloproteinases (MMPs), a disintegrin and metalloproteinases (ADAMs), and a disintegrin and metalloproteinases with thrombospondin motifs (ADAMTSs). Our analysis of previously published scRNAseq datasets highlight that these metalloproteinases show dynamic expression patterns during tooth development, with expression in a wide range of cell types, suggesting multiple roles in tooth morphogenesis. To investigate this, Marimastat, a broad-spectrum inhibitor of MMPs, ADAMs, and ADAMTSs, was applied to ex vivo cultures of mouse molar tooth germs. The treated samples exhibited significant changes in tooth germ size and morphology, including an overall reduction in size and an inversion of the typical bell shape. The cervical loop failed to extend, and the central area of the inner enamel epithelium protruded. Marimastat treatment also disrupted proliferation, cell polarization, and organization compared with control tooth germs. In addition, a decrease in laminin expression was observed, leading to a disruption in continuity of the basement membrane at the epithelial-mesenchymal junction. Elevated hypoxia-inducible factor 1-alpha gene (Hif-1α) expression correlated with a disruption to blood vessel development around the tooth germs. These results reveal the crucial role of metalloproteinases in tooth growth, shape, cervical loop elongation, and the regulation of blood vessel formation during prenatal tooth development.NEW & NOTEWORTHY Inhibition of metalloproteinases during tooth development had a wide-ranging impact on molar growth affecting proliferation, cell migration, and vascularization, highlighting the diverse role of these proteins in controlling development.

Human monocyte-derived macrophages shift subcellular metalloprotease activity depending on their activation state

Proteases are key effectors in macrophage function during the initiation and resolution of inflammation. Recent studies have shown that some proteases, traditionally considered extracellular, also exhibit enzymatic and non-enzymatic functions within the cell. This study explores the differential protease landscapes of macrophages based on their phenotype. Human monocytes were isolated from healthy volunteers and stimulated with M-CSF (resting macrophages), LPS/IFN-γ (inflammatory macrophages), or IL-4 (immunosuppressive macrophages). IL-4-stimulated macrophages secreted higher levels of MMPs and natural protease inhibitors compared to LPS/IFN-γ-stimulated macrophages. Increased extracellular proteolytic activity was detected in LPS/IFN-γ-stimulated macrophages while IL-4 stimulation increased cell-associated proteolytic activity, particularly for MMPs. Subcellular fractionation and confocal microscopy revealed the uptake of extracellular MMP-9 and its relocation to the nucleus in IL-4-stimulated, though not in LPS/IFN-γ-stimulated macrophages. Collectively, macrophages alter the subcellular location and activity of their MMPs based on the stimuli received, suggesting another mechanism for protease regulation in macrophage biology.

NF-κB signaling pathway in tumor microenvironment

The genesis and progression of tumors are multifaceted processes influenced by genetic mutations within the tumor cells and the dynamic interplay with their surrounding milieu, which incessantly impacts the course of cancer. The tumor microenvironment (TME) is a complex and dynamic entity that encompasses not only the tumor cells but also an array of non-cancerous cells, signaling molecules, and the extracellular matrix. This intricate network is crucial in tumor progression, metastasis, and response to treatments. The TME is populated by diverse cell types, including immune cells, fibroblasts, endothelial cells, alongside cytokines and growth factors, all of which play roles in either suppressing or fostering tumor growth. Grasping the nuances of the interactions within the TME is vital for the advancement of targeted cancer therapies. Consequently, a thorough understanding of the alterations of TME and the identification of upstream regulatory targets have emerged as a research priority. NF-κB transcription factors, central to inflammation and innate immunity, are increasingly recognized for their significant role in cancer onset and progression. This review emphasizes the crucial influence of the NF-κB signaling pathway within the TME, underscoring its roles in the development and advancement of cancer. By examining the interactions between NF-κB and various components of the TME, targeting the NF-κB pathway appears as a promising cancer treatment approach.

Tissue engineering approaches for dental pulp regeneration: The development of novel bioactive materials using pharmacological epigenetic inhibitors

The drive for minimally invasive endodontic treatment strategies has shifted focus from technically complex and destructive root canal treatments towards more conservative vital pulp treatment. However, novel approaches to maintaining dental pulp vitality after disease or trauma will require the development of innovative, biologically-driven regenerative medicine strategies. For example, cell-homing and cell-based therapies have recently been developed in vitro and trialled in preclinical models to study dental pulp regeneration. These approaches utilise natural and synthetic scaffolds that can deliver a range of bioactive pharmacological epigenetic modulators (HDACis, DNMTis, and ncRNAs), which are cost-effective and easily applied to stimulate pulp tissue regrowth. Unfortunately, many biological factors hinder the clinical development of regenerative therapies, including a lack of blood supply and poor infection control in the necrotic root canal system. Additional challenges include a need for clinically relevant models and manufacturing challenges such as scalability, cost concerns, and regulatory issues. This review will describe the current state of bioactive-biomaterial/scaffold-based engineering strategies to stimulate dentine-pulp regeneration, explicitly focusing on epigenetic modulators and therapeutic pharmacological inhibition. It will highlight the components of dental pulp regenerative approaches, describe their current limitations, and offer suggestions for the effective translation of novel epigenetic-laden bioactive materials for innovative therapeutics.

Study on the mechanism of MDSC-platelets and their role in the breast cancer microenvironment

Myeloid-derived suppressor cells (MDSCs) are key immunosuppressive cells in the tumor microenvironment (TME) that play critical roles in promoting tumor growth and metastasis. Tumor-associated platelets (TAPs) help cancer cells evade the immune system and promote metastasis. In this paper, we describe the interaction between MDSCs and TAPs, including their generation, secretion, activation, and recruitment, as well as the effects of MDSCs and platelets on the generation and changes in the immune, metabolic, and angiogenic breast cancer (BC) microenvironments. In addition, we summarize preclinical and clinical studies, traditional Chinese medicine (TCM) therapeutic approaches, and new technologies related to targeting and preventing MDSCs from interacting with TAPs to modulate the BC TME, discuss the potential mechanisms, and provide perspectives for future development. The therapeutic strategies discussed in this review may have implications in promoting the normalization of the BC TME, reducing primary tumor growth and distant lung metastasis, and improving the efficiency of anti-tumor therapy, thereby improving the overall survival (OS) and progression-free survival (PFS) of patients. However, despite the significant advances in understanding these mechanisms and therapeutic strategies, the complexity and heterogeneity of MDSCs and side effects of antiplatelet agents remain challenging. This requires further investigation in future prospective cohort studies.

C-C chemokine receptor 4 (CCR4)-positive regulatory T cells interact with tumor-associated macrophages to facilitate metastatic potential after radiation

PURPOSE

Our previous study revealed that elevated C-C motif chemokine ligand 2 (CCL2) secretion by irradiated cancer cells recruited C-C motif chemokine receptor 2 (CCR2)-positive myeloid cells and polarized M2-type tumor-associated macrophages (TAMs), promoting lung metastasis in an established mouse model. This study investigated the impact of CCL2 and TAMs on adaptive immunity.

METHODS

We assessed the influence of CCL2 and TAMs on adaptive immunity through two ectopic allograft mouse models constructed with MB49 bladder cancer cells and Lewis lung carcinoma cells. Both models exhibited delayed primary tumor growth following radiation therapy (RT), but RT promoted the development of pulmonary metastases in C57BL/6 mice. Additionally, we employed a direct coculture system to investigate the interaction between macrophages and target cells in the context of adaptive immunity.

RESULTS

C-C motif chemokine receptor 4 (CCR4)-positive regulatory T cells (Tregs) were recruited to the postirradiated tumor microenvironment (TME). Utilizing a CCR4 antagonist to inhibit CCL2-CCR4 activation reversed the infiltration of CCR4 + Tregs and reduced the incidence of pulmonary metastases. In addition, a positive feedback loop between M2-type TAMs and Tregs was observed. The combined blockade of the CCL2-CCR4 and CCL2-CCR2 signaling pathways further decreased the risk of RT-promoted lung metastasis.

CONCLUSION

The recruitment of CCR4 + Tregs to the postirradiated TME increases the metastatic potential of tumor cells through increased interactions with M2-type TAMs. A significant reduction in post-RT lung metastases in ectopic mouse models was achieved by disrupting the recruitment of both CCR4 + Tregs and CCR2 + myeloid cells, which are TAM precursors.

Myeloid-derived suppressor cells in cancer and cancer therapy

Anticancer agents continue to dominate the list of newly approved drugs, approximately half of which are immunotherapies. This trend illustrates the considerable promise of cancer treatments that modulate the immune system. However, the immune system is complex and dynamic, and can have both tumour-suppressive and tumour-promoting effects. Understanding the full range of immune modulation in cancer is crucial to identifying more effective treatment strategies. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells that develop in association with chronic inflammation, which is a hallmark of cancer. Indeed, MDSCs accumulate in the tumour microenvironment, where they strongly inhibit anticancer functions of T cells and natural killer cells and exert a variety of other tumour-promoting effects. Emerging evidence indicates that MDSCs also contribute to resistance to cancer treatments, particularly immunotherapies. Conversely, treatment approaches designed to eliminate cancer cells can have important additional effects on MDSC function, which can be either positive or negative. In this Review, we discuss the interplay between MDSCs and various other cell types found in tumours as well as the mechanisms by which MDSCs promote tumour progression. We also discuss the relevance and implications of MDSCs for cancer therapy.

ICAM-1-decorated extracellular vesicles loaded with miR-146a and Glut1 drive immunomodulation and hinder tumor progression in a murine model of breast cancer

Tumor-associated immune cells play a crucial role in cancer progression. Myeloid-derived suppressor cells (MDSCs), for example, are immature innate immune cells that infiltrate the tumor to exert immunosuppressive activity and protect cancer cells from the host's immune system and/or cancer-specific immunotherapies. While tumor-associated immune cells have emerged as a promising therapeutic target, efforts to counter immunosuppression within the tumor niche have been hampered by the lack of approaches that selectively target the immune cell compartment of the tumor, to effectively eliminate "tumor-protecting" immune cells and/or drive an "anti-tumor" phenotype. Here we report on a novel nanotechnology-based approach to target tumor-associated immune cells and promote "anti-tumor" responses in a murine model of breast cancer. Engineered extracellular vesicles (EVs) decorated with ICAM-1 ligands and loaded with miR-146a and Glut1, were biosynthesized (in vitro or in vivo) and administered to tumor-bearing mice once a week for up to 5 weeks. The impact of this treatment modality on the immune cell compartment and tumor progression was evaluated via RT-qPCR, flow cytometry, and histology. Our results indicate that weekly administration of the engineered EVs (i.e., ICAM-1-decorated and loaded with miR-146a and Glut1) hampered tumor progression compared to ICAM-1-decorated EVs with no cargo. Flow cytometry analyses of the tumors indicated a shift in the phenotype of the immune cell population toward a more pro-inflammatory state, which appeared to have facilitated the infiltration of tumor-targeting T cells, and was associated with a reduction in tumor size and decreased metastatic burden. Altogether, our results indicate that ICAM-1-decorated EVs could be a powerful platform nanotechnology for the deployment of immune cell-targeting therapies to solid tumors.

Investigation of target genes and potential mechanisms related to compound Xiao-ai-fei honey ointment based on network pharmacology and bioinformatics analysis

BACKGROUND

Compound Xiao-ai-fei honey ointment (CXHO) is an anticancer preparation with a long history in Uyghur folk medicine in China and has been used for the treatment of gastric cancer (GC) in Xinjiang, China. Nevertheless, the mechanism of its anticancer effect remains to be investigated.

METHODS

Bioactive ingredients of CXHO were retrieved from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform database. Target genes of ingredients were acquired via the PubChem and Swiss target prediction database. Gene expression profiling of GC was obtained from GSE54129 in the GEO database and analyzed using the limma package in R. The hub genes associated with CXHO in GC were validated using the TIMER2.0 database, GEPIA2 database and Auto Dock tools. The effect of CXHO on migration of GC cells was detected by Transwell chamber assay and Wound healing assay. The effect of CXHO on expression levels of MMP2/MMP9 and NF-κb, PI3K/AKT signaling pathway was detected by Western blot assay.

RESULTS

Forty-five bioactive ingredients and their 819 related genes were found. A total of 462 differentially expressed genes were identified between GC patients and healthy controls. Seventeen common target genes were identified as hub genes CXHO against GC. Among them, MMP2 and MMP9 were significantly associated with tumor immune infiltrates and had good binding affinity with effective ingredients. Moreover, we validated the mRNA and protein expression levels and prognostic value of MMP2 and MMP9 by different databases. In addition, Kyoto encyclopedia of genes and genomes and gene ontology analyses showed that the 17 common target genes were mainly involved in steroid hormone biosynthesis and cancer-related pathways. Experimental results showed that CXHO inhibited migration of GC cells and down regulated the expression levels of MMP2/MMP9, NF-κb. In addition, CXHO can inhibited PI3K/AKT signaling pathway.

CONCLUSION

We identified and experimental validated 2 pivotal target genes of CXHO against GC and preliminarily analyzed the potential mechanisms by which CXHO inhibits the development of GC. All these findings support CXHO as a promising drug for the treatment of GC.

Irradiated Mammary Spheroids Elucidate Mechanisms of Macrophage-Mediated Breast Cancer Recurrence

Introduction

While most patients with triple negative breast cancer receive radiation therapy to improve outcomes, a significant subset of patients continue to experience recurrence. Macrophage infiltration into radiation-damaged sites has been shown to promote breast cancer recurrence in pre-clinical models. However, the mechanisms that drive recurrence are unknown. Here, we developed a novel spheroid model to evaluate macrophage-mediated tumor cell recruitment.

Methods

We characterized infiltrating macrophage phenotypes into irradiated mouse mammary tissue via flow cytometry. We then engineered a spheroid model of radiation damage with primary fibroblasts, macrophages, and 4T1 mouse mammary carcinoma cells using in vivo macrophage infiltration results to inform our model. We analyzed 4T1 infiltration into spheroids when co-cultured with biologically relevant ratios of pro-healing M2:pro-inflammatory M1 macrophages. Finally, we quantified interleukin 6 (IL-6) secretion associated with conditions favorable to tumor cell infiltration, and we directly evaluated the impact of IL-6 on tumor cell invasiveness in vitro and in vivo.

Results

In our in vivo model, we observed a significant increase in M2 macrophages in mouse mammary glands 10 days post-irradiation. We determined that tumor cell motility toward irradiated spheroids was enhanced in the presence of a 2:1 ratio of M2:M1 macrophages. We also measured a significant increase in IL-6 secretion after irradiation both in vivo and in our model. This secretion increased tumor cell invasiveness, and tumor cell invasion and recruitment were mitigated by neutralizing IL-6.

Conclusions

Our work suggests that interactions between infiltrating macrophages and damaged stromal cells facilitate breast cancer recurrence through IL-6 signaling.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00775-x.

Antiproliferative, Antiangiogenic, and Antimigrastatic Effects of Oroxylum indicum (L.) Kurz Extract on Breast Cancer Cell

Breast cancer recurrence continues to pose a major clinical problem, despite significant advancements in early diagnosis and an aggressive mode of treatment. This study aimed at investigating the anticancer activity of Oroxylum indicum extract (OIE) by assessing cell proliferation, cell migration, and angiogenesis in metastatic breast cancer MDA-MB-231 cell lines. This study also estimated the phytochemical profiles of OIE by LC-QTOF-MS. The extract was found to contain six identified flavonoid substances, and baicalein was the most abundant substance in the extract. Cell proliferation capacity was performed by cell counting kit-8 (CCK-8) and colony formation assays. The effect of OIE on cell migration was determined using wound healing and transwell assays. Meanwhile, MDA-MB-231-induced angiogenesis on chick chorioallantoic membrane (CAM) was applied to investigate the ex vivo antiangiogenesis activity of the extracts. OIE at concentrations lower than 600 μg/mL had no cytotoxic effects against MDA-MB-231 cells. OIE was found to inhibit the long-term colony formation ability of MDA-MB-231 cells in a concentration-dependent manner. Antimigration and antiangiogenesis activities were further investigated using noncytotoxic concentrations of OIE ranging from 25 to 150 μg/mL. OIE greatly reduced the migration of MDA-MB-231 breast cancer cells in a dose-dependent manner. OIE significantly suppressed the MDA-MB-231-induced angiogenesis, and there was no substantial toxic effect on natural angiogenesis. Interestingly, the concentration of OIE at 150 μg/mL was as practically potent as pazopanib, the positive anticancer drug, at 4.37 μg/mL in inhibiting MDA-MB-231 cell migration and angiogenesis induced by these cells. Therefore, the inhibitory effects of OIE in cell proliferation and cell migration, together with antiangiogenesis in MDA-MB-231 breast cancer cells, suggesting that OIE has the potential to be a novel adjunct candidate for breast cancer chemotherapeutic agents.

The tissue-specific transcriptional landscape underlines the involvement of endothelial cells in health and disease

Endothelial cells (ECs) that line vascular and lymphatic vessels are being increasingly recognized as important to organ function in health and disease. ECs participate not only in the trafficking of gases, metabolites, and cells between the bloodstream and tissues but also in the angiocrine-based induction of heterogeneous parenchymal cells, which are unique to their specific tissue functions. The molecular mechanisms regulating EC heterogeneity between and within different tissues are modeled during embryogenesis and become fully established in adults. Any changes in adult tissue homeostasis induced by aging, stress conditions, and various noxae may reshape EC heterogeneity and induce specific transcriptional features that condition a functional phenotype. Heterogeneity is sustained via specific genetic programs organized through the combinatory effects of a discrete number of transcription factors (TFs) that, at the single tissue-level, constitute dynamic networks that are post-transcriptionally and epigenetically regulated. This review is focused on outlining the TF-based networks involved in EC specialization and physiological and pathological stressors thought to modify their architecture.

The current understanding of the immune landscape relative to radiotherapy across tumor types

Radiotherapy is part of the standard of care treatment for a great majority of cancer patients. As a result of radiation, both tumor cells and the environment around them are affected directly by radiation, which mainly primes but also might limit the immune response. Multiple immune factors play a role in cancer progression and response to radiotherapy, including the immune tumor microenvironment and systemic immunity referred to as the immune landscape. A heterogeneous tumor microenvironment and the varying patient characteristics complicate the dynamic relationship between radiotherapy and this immune landscape. In this review, we will present the current overview of the immunological landscape in relation to radiotherapy in order to provide insight and encourage research to further improve cancer treatment. An investigation into the impact of radiation therapy on the immune landscape showed in several cancers a common pattern of immunological responses after radiation. Radiation leads to an upsurge in infiltrating T lymphocytes and the expression of programmed death ligand 1 (PD-L1) which can hint at a benefit for the patient when combined with immunotherapy. In spite of this, lymphopenia in the tumor microenvironment of 'cold' tumors or caused by radiation is considered to be an important obstacle to the patient's survival. In several cancers, a rise in the immunosuppressive populations is seen after radiation, mainly pro-tumoral M2 macrophages and myeloid-derived suppressor cells (MDSCs). As a final point, we will highlight how the radiation parameters themselves can influence the immune system and, therefore, be exploited to the advantage of the patient.

Role of voltage-gated proton channel (Hv1) in cancer biology

The acid-base characteristics of tumor cells and the other elements that compose the tumor microenvironment have been topics of scientific interest in oncological research. There is much evidence confirming that pH conditions are maintained by changes in the patterns of expression of certain proton transporters. In the past decade, the voltage-gated proton channel (Hv1) has been added to this list and is increasingly being recognized as a target with onco-therapeutic potential. The Hv1 channel is key to proton extrusion for maintaining a balanced cytosolic pH. This protein-channel is expressed in a myriad of tissues and cell lineages whose functions vary from producing bioluminescence in dinoflagellates to alkalizing spermatozoa cytoplasm for reproduction, and regulating the respiratory burst for immune system response. It is no wonder that in acidic environments such as the tumor microenvironment, an exacerbated expression and function of this channel has been reported. Indeed, multiple studies have revealed a strong relationship between pH balance, cancer development, and the overexpression of the Hv1 channel, being proposed as a marker for malignancy in cancer. In this review, we present data that supports the idea that the Hv1 channel plays a significant role in cancer by maintaining pH conditions that favor the development of malignancy features in solid tumor models. With the antecedents presented in this bibliographic report, we want to strengthen the idea that the Hv1 proton channel is an excellent therapeutic strategy to counter the development of solid tumors.

Radiation Therapies in Cancer

A crucial element of cancer treatment is radiation therapy that is used to destroy tumors and cancer cells through radiation. Another essential component is immunotherapy that helps immune system to combat cancer. The combination of both radiation therapy and immunotherapy is being focused recently for the treatment of many tumors. Chemotherapy includes the use of some chemical agent to control the growth of cancer, whereas irradiation involves the use of radiations of high energy to kill cancer cells. The union of both became the strongest practice in cancer treatment techniques. Specific chemotherapies are combined with radiation in the treatment of cancer after proper preclinical assessment of their effectiveness. Some classes of compounds include platinum-based drugs, antimicrotubules, antimetabolites (5-Fluorouracil, Capecitabine, Gemcitabine, Pemetrexed), topoisomerase I inhibitors, alkylating agents (Temozolomide), and other agents (Mitomycin-C, Hypoxic Sensitizers, Nimorazole).

Photon- and Proton-Mediated Biological Effects: What Has Been Learned?

The current understanding of the effects of radiation is gradually becoming broader. However, it still remains unclear why some patients respond to radiation with a pronounced positive response, while in some cases the disease progresses. This is the motivation for studying the effects of radiation therapy not only on tumor cells, but also on the tumor microenvironment, as well as studying the systemic effects of radiation. In this framework, we review the biological effects of two types of radiotherapy: photon and proton irradiations. Photon therapy is a commonly used type of radiation therapy due to its wide availability and long-term history, with understandable and predictable outcomes. Proton therapy is an emerging technology, already regarded as the method of choice for many cancers in adults and children, both dosimetrically and biologically. This review, written after the analysis of more than 100 relevant literary sources, describes the local effects of photon and proton therapy and shows the mechanisms of tumor cell damage, interaction with tumor microenvironment cells and effects on angiogenesis. After systematic analysis of the literature, we can conclude that proton therapy has potentially favorable toxicological profiles compared to photon irradiation, explained mainly by physical but also biological properties of protons. Despite the fact that radiobiological effects of protons and photons are generally similar, protons inflict reduced damage to healthy tissues surrounding the tumor and hence promote fewer adverse events, not only local, but also systemic.

The role of KiSS1 gene on the growth and migration of prostate cancer and the underlying molecular mechanisms

Metastatic prostate cancers have a high mortality rate. KiSS1 was originally identified as a metastasis suppressor gene in metastatic melanoma and breast cancer, but its role in prostate cancer has been contradictory. This study was therefore undertaken to investigate the effects of KiSS1 overexpression on the growth and migration of human metastatic prostate cancer cells. We first tested the effect of KiSS1 overexpression on the growth and migration of DU145 human metastatic prostate cancer cells in vitro. DU145 cells were infected with the culture medium of 293T cells, which produce lentivirus particles containing KiSS1. A 2.5-fold increase in proliferation of KiSS1-overexpressing cancer cells was observed, and these cells formed tumor spheroids about 3 times larger than the vector control group. qPCR and immunoblotting revealed the association between increased cell growth and regulation of the PI3K/Akt and cell cycle genes, and also that increases in β-catenin and CD133 contribute to tumor aggregation. KiSS1 overexpression resulted in upregulation of the β-arrestin1/2 and Raf-MEK-ERK-NF-κB pathways via KiSS1R. Moreover, the migration and invasion of KiSS1-overexpressing cells were determined to be faster than the control group, along with 1.6-fold increased metastatic colonization of the KiSS1-overexpressing cancer cells. These were associated to the regulation of EMT gene expressions, such as E-cadherin and N-cadherin, and the upregulation of MMP9. In a xenograft mouse model inoculated with DU145 cells infected GFP or KiSS1 via a lentiviral vector, KiSS1 statistically significantly increased the tumor growth, with upregulation of PCNA and Ki-67 in the tumor tissues. In addition, KiSS1 increased the angiogenic capacity by upregulating VEGF-A and CD31, both in vitro and in vivo. Taken together, our results indicate that KiSS1 not only induces prostate cancer proliferation, but also promotes metastasis by increasing the migration, invasion, and angiogenesis of malignant cells.

Role of myeloid-derived suppressor cells in the formation of pre-metastatic niche

Metastasis is a complex process, which depends on the interaction between tumor cells and host organs. Driven by the primary tumor, the host organ will establish an environment suitable for the growth of tumor cells before their arrival, which is called the pre-metastasis niche. The formation of pre-metastasis niche requires the participation of a variety of cells, in which myeloid-derived suppressor cells play a very important role. They reach the host organ before the tumor cells, and promote the establishment of the pre-metastasis niche by influencing immunosuppression, vascular leakage, extracellular matrix remodeling, angiogenesis and so on. In this article, we introduced the formation of the pre-metastasis niche and discussed the important role of myeloid-derived suppressor cells. In addition, this paper also emphasized the targeting of myeloid-derived suppressor cells as a therapeutic strategy to inhibit the formation of pre-metastasis niche, which provided a research idea for curbing tumor metastasis.

HIF-1α Inhibition Improves Anti-Tumor Immunity and Promotes the Efficacy of Stereotactic Ablative Radiotherapy (SABR)

Simple Summary

Stereotactic ablative radiotherapy (SABR), which irradiates tumors with high-dose radiation per fraction, promotes anti-tumor immunity by stimulating various immune processes. SABR also induces vascular damage and obstructs blood flow, thereby increasing tumor hypoxia and upregulation of hypoxia-inducible factors HIF-1α and HIF-2α, master transcription factors for the cellular response to hypoxia. HIF-1α and HIF-2α are key players in the upregulation of immune suppression in hypoxia. Therefore, the radiation-induced increase in anti-tumor immunity is masked by the HIF-mediated immune suppression. Pre-clinical experiments show that inhibition of HIF-1α effectively prevents immune suppression and improves anti-tumor immunity. A combination of HIF-1α inhibitors with immunotherapy with checkpoint blocking antibodies may represent a novel approach to boost anti-tumor immunity and enhance the efficacy of SABR.

Abstract

High-dose hypofractionated radiation such as SABR (stereotactic ablative radiotherapy) evokes an anti-tumor immune response by promoting a series of immune-stimulating processes, including the release of tumor-specific antigens from damaged tumor cells and the final effector phase of immune-mediated lysis of target tumor cells. High-dose hypofractionated radiation also causes vascular damage in tumors, thereby increasing tumor hypoxia and upregulation of hypoxia-inducible factors HIF-1α and HIF-2α, the master transcription factors for the cellular response to hypoxia. HIF-1α and HIF-2α are critical factors in the upregulation of immune suppression and are the master regulators of immune evasion of tumors. Consequently, SABR-induced increase in anti-tumor immunity is counterbalanced by the increase in immune suppression mediated by HIFα. Inhibition of HIF-1α with small molecules such as metformin downregulates immunosuppressive pathways, including the expression of immune checkpoints, and it improves or restores the anti-tumor immunity stimulated by irradiation. Combinations of HIFα inhibitors, particularly HIF-1α inhibitors, with immune checkpoint blocking antibodies may represent a novel approach to boost the overall anti-tumor immune profile in patients and thus enhance outcomes after SABR.

Tumor-derived C-C motif ligand 2 (CCL2) induces the recruitment and polarization of tumor-associated macrophages and increases the metastatic potential of bladder cancer cells in the postirradiated microenvironment

PURPOSE

Radiotherapy (RT) is mainly used for bladder preservation in patients with muscle-invasive bladder cancer. The response of urothelial tumors to RT remains unsatisfactory. We investigated the interaction of RT and tumor-associated macrophages (TAMs) in the context of bladder cancer radioresistance.

METHODS

We evaluated the therapeutic effects of RT and TAM distribution by establishing an ectopic allograft mouse model. A Transwell coculture system was used to simulate the interaction between TAMs and MB49 bladder cancer cells in the tumor microenvironment. Cytokines and chemokines were analyzed in irradiated MB49 cells. Colony formation and Boyden chamber assays were used to assess the cytotoxic effects and the effects of TAMs on MB49 cell invasion, respectively.

RESULTS

Local RT delayed primary tumor growth but promoted pulmonary metastases in C57BL/6 mice. Increased secretion of C-C motif chemokine ligand (CCL2) by irradiated MB49 cells, especially in the presence of M1-type TAMs, contributed to the infiltration of bone marrow-derived C-C motif chemokine receptor 2 (CCR2)-positive myeloid cells and the polarization of M1-type TAMs toward the M2 type to promote MB49 cell invasion. Blockade of CCL2-CCR2 activation by a CCR2 antagonist reversed the phenotypic TAM transformation and suppressed pulmonary metastases.

CONCLUSION

Bladder cancer cells responded to RT by producing CCL2, which recruited TAM precursors from bone marrow and polarized M1-type TAMs toward the M2 type. This phenotypic TAM transformation promoted the pulmonary metastasis of bladder cancer cells after RT. Disrupting the CCL2-CCR2 signaling axis in combination with RT holds promise for improving RT efficacy in bladder cancer.

Breast Cancer Tumor Microenvironment and Molecular Aberrations Hijack Tumoricidal Immunity

Simple Summary

Immune therapy is designed to stimulate tumoricidal effects in a variety of solid tumors including breast carcinomas. However, the emergence of resistant clones leads to treatment failure. Understanding the molecular, cellular, and microenvironmental aberrations is crucial to uncovering underlying mechanisms and developing advanced strategies for preventing or combating these resistant malignancies. This review will summarize research findings revealing various mechanisms employed to hijack innate and adaptive immune surveillance mechanisms, develop hypoxic and tumor promoting metabolism, and foster an immune tolerance microenvironment. In addition, it will highlight potential targets for therapeutic approaches.

Abstract

Breast cancer is the most common malignancy among females in western countries, where women have an overall lifetime risk of >10% for developing invasive breast carcinomas. It is not a single disease but is composed of distinct subtypes associated with different clinical outcomes and is highly heterogeneous in both the molecular and clinical aspects. Although tumor initiation is largely driven by acquired genetic alterations, recent data suggest microenvironment-mediated immune evasion may play an important role in neoplastic progression. Beyond surgical resection, radiation, and chemotherapy, additional therapeutic options include hormonal deactivation, targeted-signaling pathway treatment, DNA repair inhibition, and aberrant epigenetic reversion. Yet, the fatality rate of metastatic breast cancer remains unacceptably high, largely due to treatment resistance and metastases to brain, lung, or bone marrow where tumor bed penetration of therapeutic agents is limited. Recent studies indicate the development of immune-oncological therapy could potentially eradicate this devastating malignancy. Evidence suggests tumors express immunogenic neoantigens but the immunity towards these antigens is frequently muted. Established tumors exhibit immunological tolerance. This tolerance reflects a process of immune suppression elicited by the tumor, and it represents a critical obstacle towards successful antitumor immunotherapy. In general, immune evasive mechanisms adapted by breast cancer encompasses down-regulation of antigen presentations or recognition, lack of immune effector cells, obstruction of anti-tumor immune cell maturation, accumulation of immunosuppressive cells, production of inhibitory cytokines, chemokines or ligands/receptors, and up-regulation of immune checkpoint modulators. Together with altered metabolism and hypoxic conditions, they constitute a permissive tumor microenvironment. This article intends to discern representative incidents and to provide potential innovative therapeutic regimens to reinstate tumoricidal immunity.

Therapeutic targeting of the hypoxic tumour microenvironment

Hypoxia is prevalent in human tumours and contributes to microenvironments that shape cancer evolution and adversely affect therapeutic outcomes. Historically, two different tumour microenvironment (TME) research communities have been discernible. One has focused on physicochemical gradients of oxygen, pH and nutrients in the tumour interstitium, motivated in part by the barrier that hypoxia poses to effective radiotherapy. The other has focused on cellular interactions involving tumour and non-tumour cells within the TME. Over the past decade, strong links have been established between these two themes, providing new insights into fundamental aspects of tumour biology and presenting new strategies for addressing the effects of hypoxia and other microenvironmental features that arise from the inefficient microvascular system in solid tumours. This Review provides a perspective on advances at the interface between these two aspects of the TME, with a focus on translational therapeutic opportunities relating to the elimination and/or exploitation of tumour hypoxia.

Circulating Tumor Cells: A Promising Biomarker in the Management of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is a malignancy that arises from the mucosal epithelium of the nasopharynx, and its prognosis is relatively favorable. The 5-year overall survival rate in patients with locally advanced NPC currently exceeds 80%, but the development of individualized diagnosis and treatment at the molecular level is relatively lacking. Circulating tumor cells (CTCs) is the generic term for tumor cells that are present in the peripheral blood circulation. As a new biomarker with good clinical application prospects, the detection of CTCs has the advantages of being non-invasive, simple, and repeatable. By capturing and detecting CTCs in peripheral blood and monitoring the dynamic variation of its type and quantity, we can assess the biological characteristics of tumor in a timely manner and evaluate the therapeutic effect and prognosis of patients in advance, which will help to develop individualized treatments of tumors. The primary purposes of this review were the clinical application of CTCs in tumor stage determination, treatment efficacy evaluation, and prognosis prediction of NPC. In addition, we estimated the correlation between Epstein-Barr virus infection and CTCs and analyzed the difference in karyotypes and specific markers expressed on CTCs. We believe that our study will provide new insights and biomarkers for the individualized treatment of patients with NPC.

Normalization of the tumor microvasculature based on targeting and modulation of the tumor microenvironment

Angiogenesis is an essential process for tumor development. Owing to the imbalance between pro- and anti-angiogenic factors, the tumor vasculature possesses the characteristics of tortuous, hyperpermeable vessels and compressive force, resulting in a reduction in the effect of traditional chemotherapy and radiotherapy. Anti-angiogenesis has emerged as a promising strategy for cancer treatment. Tumor angiogenesis, however, has been proved to be a complex process in which the tumor microenvironment (TME) plays a vital role in the initiation and development of the tumor microvasculature. The host stromal cells in the TME, such as cancer associated fibroblasts (CAFs), tumor associated macrophages (TAMs) and Treg cells, contribute to angiogenesis. Furthermore, the abnormal metabolic environment, such as hypoxia and acidosis, leads to the up-regulated expression of angiogenic factors. Indeed, normalization of the tumor microvasculature via targeting and modulating the TME has become a promising strategy for anti-angiogenesis and anti-tumor therapy. In this review, we summarize the abnormalities of the tumor microvasculature, tumor angiogenesis induced by an abnormal metabolic environment and host stromal cells, as well as drug delivery therapies to restore the balance between pro- and anti-angiogenic factors by targeting and normalizing the tumor vasculature in the TME.

Neutrophils in cancer carcinogenesis and metastasis

In recent years, neutrophils have attracted increasing attention because of their cancer-promoting effects. An elevated neutrophil-to-lymphocyte ratio is considered a prognostic indicator for patients with cancer. Neutrophils are no longer regarded as innate immune cells with a single function, let alone bystanders in the pathological process of cancer. Their diversity and plasticity are being increasingly recognized. This review summarizes previous studies assessing the roles and mechanisms of neutrophils in cancer initiation, progression, metastasis and relapse. Although the findings are controversial, the fact that neutrophils play a dual role in promoting and suppressing cancer is undeniable. The plasticity of neutrophils allows them to adapt to different cancer microenvironments and exert different effects on cancer. Given the findings from our own research, we propose a reasonable hypothesis that neutrophils may be reprogrammed into a cancer-promoting state in the cancer microenvironment. This new perspective indicates that neutrophil reprogramming in the course of cancer treatment is a problem worthy of attention. Preventing or reversing the reprogramming of neutrophils may be a potential strategy for adjuvant cancer therapy.

Matrix metalloproteinase-9 inhibition or deletion attenuates portal hypertension in rodents

Liver cirrhosis and portal hypertension are accompanied by hyperdynamic circulation, angiogenesis and portosystemic collaterals. Matrix metalloproteinases (MMPs) participate in fibrogenesis and angiogenesis, however, whether they can be targeted in cirrhosis treatment is unclear. Therefore, we performed three series of experiments to investigate this issue. Liver cirrhosis was induced by common bile duct ligation (BDL) in Sprague‐Dawley rats. Sham‐operated rats served as controls. Rats were randomly allocated to receive vehicle, minocycline (a nonselective MMP inhibitor) or SB‐3CT (MMP‐2 and −9 inhibitor) for 28 days in the first and second series, respectively. MMP‐9 knockout mice were used in the third series. The results showed that minocycline ameliorated portal hypertension, hemodynamic abnormalities, reduced collateral shunting, mesenteric vascular density, plasma VEGF level and alleviated liver fibrosis. SB‐3CT attenuated portal hypertension, hemodynamic derangements, reduced shunting, mesenteric vascular density, mesenteric VEGF protein expression, and liver fibrosis. Knockout BDL mice had significantly alleviated portal hypertension, liver fibrosis, liver α‐SMA and mesenteric eNOS protein expressions compared to wild‐type BDL mice. Liver SMAD2 phosphorylation was down‐regulated in all series with MMP inhibition or knock‐out. In conclusion, MMP‐9 inhibition or deletion ameliorated the severity of cirrhosis, portal hypertension, and associated derangements. MMP‐9 may be targeted in the treatment of liver cirrhosis.

Impact of solitons on the progression of initial lesion in aortic dissection

Aortic dissection (AD) is the most common catastrophic disease reported at cardiovascular emergency in hospitals. Herein, a tear in the tunica intima results into separation of layers of aortic wall leading to rupture and torrential bleed. Hypoxia and oxidative stress are associated with AD. The release of hypoxia inducible factor (HIF)-1[Formula: see text] from the initial flap lesion in the tunica intima is the basis for aneurysmal prone factors. We framed a boundary value problem (BVP) to evaluate homeostatic saturation for oxygen dynamics using steady-state analysis. We prove uniqueness and existence of the solution of the BVP for gas exchange at capillary–tissue interface as a normal physiological function. Failure of homeostatic mechanism establishes hypoxia, a new quasi-steady-state in AD. We model permeation of two-layer fluid comprised of blood and HIF-1[Formula: see text] through tunica media as a generalized [Formula: see text]-dimensional nonlinear evolution equation and solve it using Lie group of transformations method. We note that the two-layer fluid permeates the tunica media as solitary wave including solitons such as bright soliton, dark soliton, peregrine soliton, topological soliton, kink soliton, breather soliton and multi-soliton complex. Also, we introduce the main result and discuss the implications of soliton solution, using graphic interpretation, to describe the early stage of progression of AD.

Short-course radiotherapy promotes pro-inflammatory macrophages via extracellular vesicles in human rectal cancer

BACKGROUND

Tumor-associated macrophages (TAM) constitute the most abundant immune cells in the tumor stroma initiating pro-inflammatory (M1) or immunosuppressive (M2) responses depending on their polarization status. Advances in tumor immunotherapy call for a detailed understanding of potential immunogenic mechanisms of irradiation routinely applied in rectal cancer patients.

METHODS

To test the effects of radiotherapy on TAM, we ex vivo irradiated tissue samples of human rectal cancer and assessed the phenotype by flow cytometry. We furthermore evaluated the distribution of leucocyte subsets in tissue sections of patients after short-course radiotherapy and compared findings to non-pretreated rectal cancer using an immunostaining approach. Organotypic assays (OTA) consisting of macrophages, cancer-associated fibroblast and cancer cell lines were used to dissect the immunological consequences of irradiation in macrophages.

RESULTS

We demonstrate that short-course neoadjuvant radiotherapy in rectal cancer patients is associated with a shift in the polarization of TAM towards an M1-like pro-inflammatory phenotype. In addition, ex vivo irradiation caused an increase in the phagocytic activity and enhanced expression of markers associated with stimulatory signals necessary for T-cell activation. In OTA we observed that this alteration in macrophage polarization could be mediated by extracellular vesicles (EV) derived from irradiated tumor cells. We identified high mobility group box 1 in EV from irradiated tumor cells as a potential effector signal in that crosstalk.

CONCLUSIONS

Our findings highlight macrophages as potential effector cells upon irradiation in rectal cancer by diminishing their immunosuppressive phenotype and activate pro-inflammation. Our data indicate that clinically applied short-term radiotherapy for rectal cancer may be exploited to stimulate immunogenic macrophages and suggest to target the polarization status of macrophages to enhance future immunotherapeutic strategies.

Correlation between the number of viable tumor cells and immune cells in the tumor microenvironment in non-small cell lung cancer after induction therapy

This study aims to determine the correlation between the percent viable tumor cells (%VTC) and the tumor microenvironment in resected non-small cell lung cancer after induction therapy. We enrolled 72 patients with non-small cell lung cancer (NSCLC) who received chemoradiotherapy (CRT) or chemotherapy (CT) prior to surgery. The ratio of the area of viable tumor cells to the total tumor area was calculated to obtain the %VTC. We also examined the number of CD4 (+), CD8 (+), CD20 (+) and FOXP3 (+) tumor-infiltrating lymphocytes (TILs), podoplanin (PDPN) (+) cancer-associated fibroblasts (CAFs), and CD204 (+) tumor-associated macrophages (TAMs) by immunohistochemistry (IHC). In the CRT group (n = 37), the tumors had significantly lower %VTC than the CT group (n = 35) (P < 0.001). In both of the CT group and CRT group, the %VTC showed a significant positive correlation with the number of CD204 (+)-TAMs (P = 0.014 and 0.005, respectively). Only in the CRT group, a higher number of CD204 (+) TAMs was associated with a shorter overall survival (OS) (P = 0.007) and recurrence-free survival (RFS) (P = 0.015). In the CRT group, the number of CD204 (+) TAMs is associated with %VTC and prognosis, suggesting that these cells may have tumor-promoting effects on the residual lung cancer in specific microenvironments after CRT.

Hair follicle stem cells as a skin-organizing signaling center during adult homeostasis

Stem cells are the essential source of building blocks for tissue homeostasis and regeneration. Their behavior is dictated by both cell-intrinsic cues and extrinsic cues from the microenvironment, known as the stem cell niche. Interestingly, recent work began to demonstrate that hair follicle stem cells (HFSCs) are not only passive recipients of signals from the surroundings, but also actively send out signals to modulate the organization and function of their own niches. Here, we discuss recent findings, and briefly refer to the old, on the interaction of HFSCs and their niches with the emphasis on the outwards signals from HFSCs toward their niches. We also highlight recent technology advancements that further promote our understanding of HFSC niches. Taken together, the HFSCs emerge as a skin-organizing center rich in signaling output for niche remodeling during various stages of adult skin homeostasis. The intricate crosstalk between HFSCs and their niches adds important insight to skin biology that will inform clinical and bioengineering fields aiming to build complete and functional 3D organotypic cultures for skin replacement therapies.

Nano drug delivery system reconstruct tumour vasculature for the tumour vascular normalisation

The abnormal structure and function of blood vessels in the TME are obvious characteristics of the tumour. Abnormal blood vessels with high leakage support the occurrence of malignant tumours and increase the possibility of tumour cell invasion and metastasis. The formation of abnormal vascular also enhances immunosuppression and prevents the delivery of chemotherapy drugs to deeper tumours. Therefore, the normalisation of tumour blood vessels is a very promising approach to improve anti-tumour efficacy, aiming to restore the structural integrity of vessels and improve drug delivery efficiency and anti-tumour immunity. In this review, we have summarised strategies to improve cancer treatment that via nano drug delivery technology regulates the normalisation of tumour blood vessels. The treatment strategies related to the structure and function of tumour blood vessels such as angiogenesis factors, tumour-associated macrophages, tumour vascular endothelial cells, tumour-associated fibroblasts and immune checkpoints in the TME were mainly discussed. The normalisation of tumour blood vessels presents new opportunities and challenges for the more efficient delivery of nanoparticles to tumour tissues and cells and an innovative combination of treatments for cancer.

Combined Radiochemotherapy: Metalloproteinases Revisited

Besides cytotoxic DNA damage irradiation of tumor cells triggers multiple intra- and intercellular signaling processes, that are part of a multilayered, treatment-induced stress response at the unicellular and tumor pathophysiological level. These processes are intertwined with intrinsic and acquired resistance mechanisms to the toxic effects of ionizing radiation and thereby co-determine the tumor response to radiotherapy. Proteolysis of structural elements and bioactive signaling moieties represents a major class of posttranslational modifications regulating intra- and intercellular communication. Plasma membrane-located and secreted metalloproteinases comprise a family of metal-, usually zinc-, dependent endopeptidases and sheddases with a broad variety of substrates including components of the extracellular matrix, cyto- and chemokines, growth and pro-angiogenic factors. Thereby, metalloproteinases play an important role in matrix remodeling and auto- and paracrine intercellular communication regulating tumor growth, angiogenesis, immune cell infiltration, tumor cell dissemination, and subsequently the response to cancer treatment. While metalloproteinases have long been identified as promising target structures for anti-cancer agents, previous pharmaceutical approaches mostly failed due to unwanted side effects related to the structural similarities among the multiple family members. Nevertheless, targeting of metalloproteinases still represents an interesting rationale alone and in combination with other treatment modalities. Here, we will give an overview on the role of metalloproteinases in the irradiated tumor microenvironment and discuss the therapeutic potential of using more specific metalloproteinase inhibitors in combination with radiotherapy.

Alternative Vascularization Mechanisms in Tumor Resistance to Therapy

Simple Summary

Tumors rely on blood vessels to grow and metastasize. Malignant tumors can employ different strategies to create a functional vascular network. Tumor cells can use normal processes of vessel formation but can also employ cancer-specific mechanisms, by co-opting normal vessels present in tissues or by turning themselves into vascular cells. These different types of tumor vessels have specific molecular and functional characteristics that profoundly affect tumor behavior and response to therapies, including drugs targeting the tumor vasculature (antiangiogenic therapies). In this review, we discuss how vessels formed by different mechanisms affect the intrinsic sensitivity of tumors to therapy and, on the other hand, how therapies can affect tumor vessel formation, leading to resistance to drugs, cancer recurrence, and treatment failure. Potential strategies to avoid vessel-mediated resistance to antineoplastic therapies will be discussed.

Abstract

Blood vessels in tumors are formed through a variety of different mechanisms, each generating vessels with peculiar structural, molecular, and functional properties. This heterogeneity has a major impact on tumor response or resistance to antineoplastic therapies and is now emerging as a promising target for strategies to prevent drug resistance and improve the distribution and efficacy of antineoplastic treatments. This review presents evidence of how different mechanisms of tumor vessel formation (vasculogenesis, glomeruloid proliferation, intussusceptive angiogenesis, vasculogenic mimicry, and vessel co-option) affect tumor responses to antiangiogenic and antineoplastic therapies, but also how therapies can promote alternative mechanisms of vessel formation, contributing to tumor recurrence, malignant progression, and acquired drug resistance. We discuss the possibility of tailoring treatment strategies to overcome vasculature-mediated drug resistance or to improve drug distribution and efficacy.

Aldose reductase regulates doxorubicin-induced immune and inflammatory responses by activating mitochondrial biogenesis

We have recently demonstrated that aldose reductase (AR) inhibitor; fidarestat prevents doxorubicin (Dox)-induced cardiotoxic side effects and inflammation in vitro and in vivo. However, the effect of fidarestat and its combination with Dox on immune cell activation and the immunomodulatory effects are not known. In this study, we examined the immunomodulatory effects of fidarestat in combination with Dox in vivo and in vitro. We observed that fidarestat decreased Dox-induced upregulation of CD11b in THP-1 monocytes. Fidarestat further attenuated Dox-induced upregulation of IL-6, IL-1β, and Nos2 in murine BMDM. Fidarestat also attenuated Dox-induced activation and infiltration of multiple subsets of inflammatory immune cells identified by expression of markers CD11b+, CD11b+F4/80+, Ly6C+CCR2high, and Ly6C+CD11b+ in the mouse spleen and liver. Furthermore, significant upregulation of markers of mitochondrial biogenesis PGC-1α, COX IV, TFAM, and phosphorylation of AMPKα1 (Ser485) was observed in THP-1 cells and livers of mice treated with Dox in combination with fidarestat. Our results suggest that fidarestat by up-regulating mitochondrial biogenesis exerts protection against Dox-induced immune and inflammatory responses in vitro and in vivo, providing further evidence for developing fidarestat as a combination agent with anthracycline drugs to prevent chemotherapy-induced inflammation and toxicity.

Peptide Receptor Radionuclide Therapy (PRRT) with 177Lu-DOTATATE; Differences in Tumor Dosimetry, Vascularity and Lesion Metrics in Pancreatic and Small Intestinal Neuroendocrine Neoplasms

Simple Summary

Patients suffering from disseminated, progressive, neuroendocrine neoplasms with a sufficient amount of somatostatin receptors and good kidney function can be treated with radioactive hormone-like molecules to prolong their life. In this study, the radioactivity in one tumor per patient at each treatment cycle was calculated and compared between 23 patients with pancreatic and 25 patients with small intestinal neuroendocrine neoplasia. Both types of tumors absorb a larger amount of radioactivity during early cycles that subsequently decline in the later cycles. This finding was more pronounced in the pancreatic tumors, which also expressed higher blood perfusion in the early cycles, known to facilitate the effect of radiation. This could be part of the reason why the pancreatic tumors shrunk more rapidly than the small intestinal ones. Our results also imply that increased administered activity in the early therapy cycles may be beneficial, at least in pancreatic neuroendocrine tumor patients.

Abstract

Dosimetry during peptide receptor radionuclide therapy (PRRT) has mainly focused on normal organs and less on the tumors. The absorbed dose in one target tumor per patient and several response related factors were assessed in 23 pancreatic neuroendocrine neoplasms (P-NENs) and 25 small-intestinal NEN (SI-NENs) during PRRT with ¹⁷⁷Lu-DOTATATE. The total administered activity per patient was (mean ± standard error of mean (SEM) 31.8 ± 1.9 GBq for P-NENs and 36 ± 1.94 GBq for SI-NENs. The absorbed tumor dose was 143.5 ± 2 Gy in P-NENs, 168.2 ± 2 Gy in SI-NENs. For both NEN types, a dose–response relationship was found between the absorbed dose and tumor shrinkage, which was more pronounced in P-NENs. A significant drop in the absorbed dose per cycle was shown during the course of PRRT. Tumor vascularization was higher in P-NENs than in SI-NENs at baseline but equal post-PRRT. The time to progression (RECIST 1.1) was similar for patients with P-NEN (mean ± SEM 30 ± 1 months) and SI-NEN (33 ± 1 months). In conclusion, a dose response relationship was established for both P-NENs and SI-NENs and a significant drop in the absorbed dose per cycle was shown during the course of PRRT, which warrants further investigation to understand the factors impacting PRRT to improve personalized treatment protocol design.

Polymorphonuclear-MDSCs Facilitate Tumor Regrowth After Radiation by Suppressing CD8+ T Cells

PURPOSE

Radiation therapy (RT) is widely used in the treatment of cancer. Unfortunately, RT alone is insufficient to control the disease in most cases, as regrowth after irradiation still occur. Thus, it would be meaningful to explore the underlying mechanism of tumor regrowth after irradiation. Myeloid-derived suppressor cells (MDSCs) contribute to the immunosuppressive tumor microenvironment and hinder the therapeutic efficacy of RT. However, it is unclear whether MDSCs-mediated immune suppression contributes to local relapse after irradiation. In this article, we tried to figure out how MDSCs sabotage the therapeutic effect of RT, and tried to determine the potential synergistic effect of combination between targeting MDSCs and RT.

METHODS AND MATERIALS

A syngeneic murine model of Lewis lung cancer was used. The abundance of tumor infiltrating MDSCs and tumor growth after irradiation was assessed. The percentage and functional state of CD8⁺ T cells were measured by flow cytometry, with or without polymorphonuclear (PMN)-MDSCs depletion. Arginase 1 (ARG1) expression and activity of MDSCs were examined by hematoxylin and eosin staining and flow cytometry. ARG1 inhibitor and phosphodiesterase 5 inhibitor sildenafil were administered after RT to figure out the underlying mechanism of MDSCs-mediated immunosuppression.

RESULTS

We demonstrated that irradiation recruited MDSCs, especially the polymorphonuclear subset, into the tumor microenvironment. PMN-MDSCs inhibited the CD8⁺ T cell response by elevating ARG1 expression. Selective depletion of PMN-MDSCs or inhibition on ARG1 promoted the infiltration and activation of intratumoral CD8⁺ T cells, and delayed tumor regrowth after irradiation. We showed that sildenafil reduced the accumulation and ARG1 expression of PMN-MDSCs after irradiation, thus abrogating the MDSCs-mediated immunosuppression.

CONCLUSIONS

Our results have suggested that PMN-MDSCs participate in the irradiation-induced immune suppression through ARG1 activation. We have also found that sildenafil has the potential to facilitate antitumor immunity, which provides a new alternative to delay tumor recurrence after RT.

Role of Myeloid-Derived Suppressor Cells in High-Dose-Irradiated TRAMP-C1 Tumors: A Therapeutic Target and an Index for Assessing Tumor Microenvironment

PURPOSE

To investigate the temporal and spatial infiltration of TRAMP-C1 tumors by myeloid-derived suppressor cells (MDSCs) after high-dose radiation therapy (RT), and to explore their effect on tumor growth.

METHODS AND MATERIALS

TRAMP-C1 intramuscularly tumors were irradiated with a single dose of 8 Gy or 25 Gy. The dynamics of infiltrated MDSCs and their intratumoral spatial distribution were assessed by immunohistochemistry and flow cytometry. Cytokine levels in the blood and tumor were analyzed by multiplex immunoassay. Mice were injected with anti-Gr-1 antibody to determine whether MDSCs affect tumor growth after RT.

RESULTS

CD11b⁺Gr-1⁺ MDSCs infiltrated TRAMP-C1 tumors irradiated with 25 Gy, but not 8 Gy, within 4 hours and recruitment persisted for at least 2 weeks. Both CD11b⁺Ly6G⁺Ly6C⁺ polymorphonuclear-MDSCs (PMN-MDSCs) and CD11b⁺Ly6G^-Ly6C^hi monocytic-MDSCs (M-MDSCs) were involved. Tumor RT also increased the representation of both MDSC subpopulations in the spleen and peripheral blood. Levels of multiple cytokines were increased in the tumors at 2 weeks, including GM-CSF, G-CSF, CCL-3, CCL-5, CXCL-5, IL-6, IL-17α, and VEGF-a; while G-CSF, IL-6, and TNF-α levels increased in the blood. PMN-MDSCs aggregated in the central necrotic region of the irradiated tumors over time, where they were associated with avascular hypoxia (CD31^-PIMO⁺). MDSCs expressed the proangiogenic factor, matrix metalloproteinase-9, and, within the necrotic area, high levels of arginase-1 and indoleamine 2,3-dioxygenase. Depletion of PMN-MDSCs by Gr-1 antibody increased the efficacy of high-dose RT.

CONCLUSIONS

PMN-MDSCs infiltrate TRAMP-C1 tumors after high-dose RT. Their spatial distribution suggests they are involved in the evolution of an intratumoral state of necrosis associated with avascular hypoxia, and their phenotype is consistent with them being immunosuppressive. They appear to promote tumor growth after RT, making them a prime therapeutic target for therapeutic intervention. Assessment of MDSCs and cytokine levels in blood could be an index of the need for such an intervention.

Reprogramming the tumour microenvironment by radiotherapy: implications for radiotherapy and immunotherapy combinations

Radiotherapy (RT) is a highly effective anti-cancer therapy delivered to around 50-60% of patients. It is part of therapy for around 40% of cancer patients who are cured of their disease. Until recently, the focus of this anti-tumour efficacy has been on the direct tumour cytotoxicity and RT-induced DNA damage. Recently, the immunomodulatory effects of RT on the tumour microenvironment have increasingly been recognized. There is now intense interest in potentially using RT to induce an anti-tumour immune response, which has led to rethinking into how the efficacy of RT could be further enhanced. Following the breakthrough of immune check point inhibitors (ICIs), a new era of immuno-oncology (IO) agents has emerged and established immunotherapy as a routine part of cancer treatment. Despite ICI improving outcomes in many cancer types, overall durable responses occur in only a minority of patients. The immunostimulatory effects of RT make combinations with ICI attractive to potentially amplify anti-tumour immunity resulting in increased tumour responses and improved outcomes. In contrast, tumours with profoundly immunosuppressive tumour microenvironments, dominated by myeloid-derived cell populations, remain a greater clinical challenge and RT may potentially further enhance the immunosuppression. To harness the full potential of RT and IO agent combinations, further insights are required to enhance our understanding of the role these immunosuppressive myeloid populations play, how RT influences these populations and how they may be therapeutically manipulated in combination with RT to improve outcomes further. These are exciting times with increasing numbers of IO targets being discovered and IO agents undergoing clinical evaluation. Multidisciplinary research collaborations will be required to establish the optimal parameters for delivering RT (target volume, dose and fractionation) in combination with IO agents, including scheduling to achieve maximal therapeutic efficacy.

Enhanced stability and efficacy of GEM-TOS prodrug by co-assembly with antimetastatic shell LMWH-TOS

Chemotherapy agents have been widely used for cancer treatment, while the insolubility, instability and toxicity seriously restrict their efficacy. Thus, prodrug strategy was devised. Since some prodrugs are still with poor solubility or stability, a synergy strategy is needed to enhance their efficacy. Gemcitabine (GEM) is a prescribed anticancer drug, however, the rapid clearance, growing resistance and serious side effects limit its clinical efficacy. Conjugating GEM with d-α-tocopherol succinate (TOS) is an effective solution, while the GEM-TOS (GT) is unstable in aqueous solution. d-α-Tocopherol polyethylene glycol succinate (TPGS) has been used to enhance the stability, but GT stabilized by TPGS (GTT) has limited effect on tumor metastases. Tumor metastases lead to high mortality in patients suffering from cancers. In order to further achieve antimetastatic effect, an amphiphilic polymer (LT) was synthesized by connecting low-molecular-weight heparin (LMWH) with TOS, and eventually obtained desired self-delivery micellar NPs (GLT) by co-assembly GT with LT. The GLT not only possessed excellent stability, but also inhibited the metastases by acting on different phases of the metastatic cascade. The hydrophobic TOS inhibited the secretion of matrix metalloproteinase-9 (MMP-9), the hydrophilic LMWH inhibited the interaction between tumor cells and platelets. As a result, GLT reduced tumor cells entering the blood and implanting at the distant organs, leading to a much more excellent inhibitory effect on the lung metastasis than GEM and GTT.

Aptamer-Based In Vivo Therapeutic Targeting of Glioblastoma

Glioblastoma (GBM) is the most aggressive, infiltrative, and lethal brain tumor in humans. Despite the extensive advancement in the knowledge about tumor progression and treatment over the last few years, the prognosis of GBM is still very poor due to the difficulty of targeting drugs or anticancer molecules to GBM cells. The major challenge in improving GBM treatment implicates the development of a targeted drug delivery system, capable of crossing the blood–brain barrier (BBB) and specifically targeting GBM cells. Aptamers possess many characteristics that make them ideal novel therapeutic agents for the treatment of GBM. They are short single-stranded nucleic acids (RNA or ssDNA) able to bind to a molecular target with high affinity and specificity. Several GBM-targeting aptamers have been developed for imaging, tumor cell isolation from biopsies, and drug/anticancer molecule delivery to the tumor cells. Due to their properties (low immunogenicity, long stability, and toxicity), a large number of aptamers have been selected against GBM biomarkers and tested in GBM cell lines, while only a few of them have also been tested in in vivo models of GBM. Herein, we specifically focus on aptamers tested in GBM in vivo models that can be considered as new diagnostic and/or therapeutic tools for GBM patients’ treatment.

High versus low dose irradiation for tumor immune reprogramming

Local administration of ionizing radiation to tumors can promote anticancer immune responses that lead to the abscopal regression of distant metastases, especially in patients receiving systemic immune-checkpoint inhibitors. Growing preclinical evidence indicates that high-dose irradiation administered locally to destroy malignant lesions, can promote the release of danger-associated molecular patterns that lead to the recruitment of immune cells, thus inducing a systemic response against tumor antigens that protects against local disease relapse and also mediates distant antineoplastic effects. An accumulating body of preclinical evidence supports also the implementation of low-dose irradiation to induce tumor immune reprogramming. Here, we provide the rationale for a clinical research agenda to refine future clinical practice based on innovative combinations of radiation-immunotherapy.

Organoids as Complex In Vitro Models for Studying Radiation-Induced Cell Recruitment

Patients with triple negative breast cancer (TNBC) typically receive chemotherapy, surgery, and radiation therapy. Although this treatment improves prognosis for most patients, some patients continue to experience recurrence within 5 years. Preclinical studies have shown that immune cell infiltration at the irradiated site may play a significant role in tumor cell recruitment; however, little is known about the mechanisms that govern this process. This lack of knowledge highlights the need to evaluate radiation-induced cell infiltration with models that have controllable variables and maintain biological integrity. Mammary organoids are multicellular three-dimensional (3D) in vitro models, and they have been used to examine many aspects of mammary development and tumorigenesis. Organoids are also emerging as a powerful tool to investigate normal tissue radiation damage. In this review, we evaluate recent advances in mammary organoid technology, consider the advantages of using organoids to study radiation response, and discuss future directions for the applications of this technique.

Snail promotes the generation of vascular endothelium by breast cancer cells

A further understanding of tumor angiogenesis is urgently needed due to the limited therapeutic efficacy of anti-angiogenesis agents. However, the origin of endothelial cells (EC) in tumors remains widely elusive and controversial. Snail has been thoroughly elucidated as a master regulator of the epithelial-mesenchymal transition (EMT), but its role in endothelium generation is not yet established. In this study, we reported a new and unexpected function of Snail in endothelium generation by breast cancer cells. We showed that high Snail-expressing breast cancer cells isolated from patients showed more endothelium generated from these cells. Expression of Snail was positively correlated with endothelial markers in breast cancer patients. The ectopic expression of Snail induced endothelial marker expression, tube formation and DiI-AcLDL uptake of breast cancer cells in vitro, and enhanced tumor growth and microvessel density in vivo. Snail-mediated endothelium generation depended on VEGF and Sox2. Mechanistically, Snail promoted the expression of VEGF and Sox2 through recruiting the p300 activator complex to these promoters. We showed the dual function of Snail in tumor initiation and angiogenesis in vivo and in vitro through activation of Sox2 and VEGF, suggesting Snail may be an ideal target for cancer therapy.

Radiation Damage to Tumor Vasculature Initiates a Program That Promotes Tumor Recurrences

This review, mostly of preclinical data, summarizes the evidence that radiation at doses relevant to radiation therapy initiates a pathway that promotes the reconstitution of the tumor vasculature leading to tumor recurrence. The pathway is not specific to tumors; it promotes repair of damaged and ischemic normal tissues by attracting proangiogenic cells from the bone marrow. For irradiated tumors the pathway comprises: (1) loss of endothelial cells and reduced tumor blood perfusion leading to increased tumor hypoxia and increased levels of hypoxia inducible factor-1 (HIF-1). Alternatively, increased HIF-1 levels may arise by reactive oxygen species (ROS) production caused by tumor reoxygenation. (2) Increased HIF-1 levels lead to increased levels in the tumor of the chemokine stromal cell-derived factor-1 (SDF-1, CXCL12), which captures monocytes/macrophages expressing the CXCR4 receptor of CXCL12. (3) The increased levels of tumor-associated macrophages (TAMs) become highly proangiogenic (M2 polarized) and restore the tumor vasculature, thereby promoting tumor recurrence. The relevance of this pathway for radiation therapy is that it can be blocked in a number of different ways including by inhibitors of monocytes/macrophages, of HIF-1, of CXCL12, of CXCR4, and of CSF-1R, the latter of which is responsible for the M2 polarization of the TAMs. All of these inhibitors produce a robust enhancement of the radiation response of a wide variety of preclinical tumor models. Further, the same inhibitors actually provide protection against radiation damage of several normal tissues. Some of these pathway inhibitors are available clinically, and a first-in-human trial of the CXCR4 inhibitor, plerixafor, with radiation therapy of glioblastoma has yielded promising results, including an impressive increase in local tumor control. Further clinical trials are warranted.

Radiation Potentiates Monocyte Infiltration into Tumors by Ninjurin1 Expression in Endothelial Cells

Radiation is a widely used treatment for cancer patients, with over half the cancer patients receiving radiation therapy during their course of treatment. Considerable evidence from both preclinical and clinical studies show that tumor recurrence gets restored following radiotherapy, due to the influx of circulating cells consisting primarily of monocytes. The attachment of monocyte to endothelial cell is the first step of the extravasation process. However, the exact molecules that direct the transmigration of monocyte from the blood vessels to the tumors remain largely unknown. The nerve injury-induced protein 1 (Ninjurin1 or Ninj1) gene, which encodes a homophilic adhesion molecule and cell surface protein, was found to be upregulated in inflammatory lesions, particularly in macrophages/monocytes, neutrophils, and endothelial cells. More recently Ninj1 was reported to be regulated following p53 activation. Considering p53 has been known to be activated by radiation, we wondered whether Ninj1 could be increased in the endothelial cells by radiation and it might contribute to the recruiting of monocytes in the tumor. Here we demonstrate that radiation-mediated up-regulation of Ninj1 in endothelial cell lines such as human umbilical vein endothelial cells (HUVECs), EA.hy926, and immortalized HUVECs. Consistent with this, we found over-expressed Ninj1 in irradiated xenograft tumors, and increased monocyte infiltration into tumors. Radiation-induced Ninj1 was transcriptionally regulated by p53, as confirmed by transfection of p53 siRNA. In addition, Ninj1 over-expression in endothelial cells accelerated monocyte adhesion. Irradiation-induced endothelial cells and monocyte interaction was inhibited by knock-down of Ninj1. Furthermore, over-expressed Ninj1 stimulated MMP-2 and MMP-9 expression in monocyte cell lines, whereas the MMP-2 and MMP-9 expression were attenuated by Ninj1 knock-down in monocytes. Taken together, we provide evidence that Ninj1 is a key molecule that generates an interaction between endothelial cells and monocytes. This result suggests that radiation-mediated Ninj1 expression in endothelial cells could be involved in the post-radiotherapy recurrence mechanism.

Deciphering and Reversing Immunosuppressive Cells in the Treatment of Hepatocellular Carcinoma

Use of immune checkpoint inhibitors (ICIs) in hepatocellular carcinoma (HCC) has been partially successful. However, most HCC patients do not respond to immunotherapy. HCC has been shown to induce several immune suppressor mechanisms in patients. These suppressor mechanisms include involvement of myeloid-derived suppressor cells, regulatory T-cells, functionally impaired dendritic cells (DCs), neutrophils, monocytes, and tumor associated macrophages. The accumulation of immunosuppressive cells may lead to an immunosuppressive tumor microenvironment as well as the dense fibrotic stroma which may contribute to immune tolerance. Our laboratory has been investigating different cellular mechanisms of immune suppression in HCC patients. In vitro as well as in vivo studies have demonstrated that abrogation of the suppressor cells enhances or unmasks tumor-specific antitumor immune responses. Two or three effective systemic therapies including ICIs and/or molecular targeted therapies and the addition of innovative combination therapies targeting immune suppressor cells may lead to increased immune recognition with a greater tumor response. We reviewed the literature for the latest research on immune suppressor cells in HCC, and here we provide a comprehensive summary of the recent studies in this field.