Targeting glioblastoma-derived pericytes improves chemotherapeutic outcome

Targeting stromal cells in tumor microenvironment as a novel treatment strategy for glioma

Glioma is the most common primary malignant tumor of the central nervous system in adults, characterized by high mortality, low cure rate and high recurrence rate. Among gliomas, glioblastoma multiforme (GBM) is the most malignant subtype. Currently, the standard treatment for patients with GBM is maximum surgical excision combined with radiotherapy and chemotherapy. But only a small percentage of patients benefit from this standard treatment. The tumor microenvironment plays an important role in the occurrence and development of most tumors. It is primarily composed of tumor cells, peripheral blood vessels, extracellular matrix, signaling molecules, stromal cells, and immune cells. The role of stromal cells in GBM has emerged as the focus of current research. The interaction among tumor, stromal, and immune cells within the tumor microenvironment can influence tumor development. Traditional research and drug therapy in glioma mainly focus on the tumor cells themselves, but recent studies have found that targeting stromal cells in the tumor microenvironment can also modulate tumor progression in GBM. Here, we review the influence of stromal cells in the tumor microenvironment of GBM on tumor cells and its related mechanism, as well as related molecular targets and signaling pathways, providing new ideas for the treatment and prognosis of GBM.

Small-molecule BTK inhibitors: From discovery to clinical application

Bruton's tyrosine kinase (BTK) inhibitors constitute a promising category of small molecules for the therapy of diverse B-cell malignancies and autoimmune disorders. This review examines the journey of BTK inhibitors from their discovery to clinical development, highlighting key milestones in their design, mechanism of action, and progression through preclinical and clinical stages. Initially identified through high-throughput screening of compound libraries, early BTK inhibitors were optimized for selectivity and potency. The discovery of ibrutinib, the first Food and Drug Administration (FDA)-approved BTK inhibitor, marked a significant breakthrough, providing a new therapeutic option for patients with chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). Following this success, numerous second-generation inhibitors have been identified to address resistance mechanisms, improve pharmacokinetics, and target specific patient populations. The challenges faced during the transition from preclinical validation to clinical trials have been discussed. Additionally, ongoing trials and emerging data on novel BTK inhibitors provide insights into their evolving role in oncology and immunology. This review emphasizes the importance of rational drug design and clinical strategy in shaping the future of BTK inhibitors.

Defective autophagy of pericytes enhances radiation-induced senescence promoting radiation brain injury

BACKGROUND

Radiation-induced brain injury (RBI) represents a major challenge for cancer patients undergoing cranial radiotherapy. However, the molecular mechanisms and therapeutic strategies of RBI remain inconclusive. With the continuous exploration of the mechanisms of RBI, an increasing number of studies have implicated cerebrovascular dysfunction as a key factor in RBI-related cognitive impairment. As pericytes are a component of the neurovascular unit, there is still a lack of understanding in current research about the specific role and function of pericytes in RBI.

METHODS

We constructed a mouse model of RBI-associated cognitive dysfunction in vivo and an in vitro radiation-induced pericyte model to explore the effects of senescent pericytes on the blood-brain barrier (BBB) and normal central nervous system cells, even glioma cells. To further clarify the effects of pericyte autophagy on senescence, molecular mechanisms were explored at the animal and cellular levels. Finally, we validated the clearance of pericyte senescence by using a senolytic drug and all-trans retinoic acid to investigate the role of radiation-induced pericyte senescence.

RESULTS

Our findings indicated that radiation-induced pericyte senescence plays a key role in BBB dysfunction, leading to RBI and subsequent cognitive decline. Strikingly, pericyte senescence also contributed to the growth and invasion of glioma cells. We further demonstrated that defective autophagy in pericytes is a vital regulatory mechanism for pericyte senescence. Moreover, autophagy activated by rapamycin could reverse pericyte senescence. Notably, the elimination of senescent cells by senolytic drugs significantly mitigated radiation-induced cognitive dysfunction.

CONCLUSIONS

Our results demonstrated that pericyte senescence may be a promising therapeutic target for RBI and glioma progression.

Single-cell transcriptomic analysis of glioblastoma reveals pericytes contributing to the blood-brain-tumor barrier and tumor progression

The blood-brain barrier is often altered in glioblastoma (GBM) creating a blood-brain-tumor barrier (BBTB) composed of pericytes. The BBTB affects chemotherapy efficacy. However, the expression signatures of BBTB-associated pericytes remain unclear. We aimed to identify BBTB-associated pericytes in single-cell RNA sequencing data of GBM using pericyte markers, a normal brain pericyte expression signature, and functional enrichment. We identified parathyroid hormone receptor-1 (PTH1R) as a potential marker of pericytes associated with BBTB function. These pericytes interact with other cells in GBM mainly through extracellular matrix-integrin signaling pathways. Compared with normal pericytes, pericytes in GBM exhibited upregulation of several ECM genes (including collagen IV and FN1), and high expression levels of these genes were associated with a poor prognosis. Cell line experiments showed that PTH1R knockdown in pericytes increased collagen IV and FN1 expression levels. In mice models, the expression levels of PTH1R, collagen IV, and FN1 were consistent with these trends. Evans Blue leakage and IgG detection in the brain tissue suggested a negative correlation between PTH1R expression levels and blood-brain barrier function. Further, a risk model based on differentially expressed genes in PTH1R+ pericytes had predictive value for GBM, as validated using independent and in-house cohorts.

Cold and hot tumors: from molecular mechanisms to targeted therapy

Immunotherapy has made significant strides in cancer treatment, particularly through immune checkpoint blockade (ICB), which has shown notable clinical benefits across various tumor types. Despite the transformative impact of ICB treatment in cancer therapy, only a minority of patients exhibit a positive response to it. In patients with solid tumors, those who respond well to ICB treatment typically demonstrate an active immune profile referred to as the "hot" (immune-inflamed) phenotype. On the other hand, non-responsive patients may exhibit a distinct "cold" (immune-desert) phenotype, differing from the features of "hot" tumors. Additionally, there is a more nuanced "excluded" immune phenotype, positioned between the "cold" and "hot" categories, known as the immune "excluded" type. Effective differentiation between "cold" and "hot" tumors, and understanding tumor intrinsic factors, immune characteristics, TME, and external factors are critical for predicting tumor response and treatment results. It is widely accepted that ICB therapy exerts a more profound effect on "hot" tumors, with limited efficacy against "cold" or "altered" tumors, necessitating combinations with other therapeutic modalities to enhance immune cell infiltration into tumor tissue and convert "cold" or "altered" tumors into "hot" ones. Therefore, aligning with the traits of "cold" and "hot" tumors, this review systematically delineates the respective immune characteristics, influencing factors, and extensively discusses varied treatment approaches and drug targets based on "cold" and "hot" tumors to assess clinical efficacy.

Effect of Apis mellifera syriaca Bee Venom on Glioblastoma Cancer: In Vitro and In Vivo Studies

Glioblastoma multiforme (GBM) is a highly aggressive and fatal primary brain tumor. The resistance of GBM to conventional treatments is attributed to factors such as the blood-brain barrier, tumor heterogeneity, and treatment-resistant stem cells. Current therapeutic efforts show limited survival benefits, emphasizing the urgent need for novel treatments. In this context, natural anti-cancer extracts and especially animal venoms have garnered attention for their potential therapeutic benefits. Bee venom in general and that of the Middle Eastern bee, Apis mellifera syriaca in particular, has been shown to have cytotoxic effects on various cancer cell types, but not glioblastoma. Therefore, this study aimed to explore the potential of A. mellifera syriaca venom as a selective anti-cancer agent for glioblastoma through in vitro and in vivo studies. Our results revealed a strong cytotoxic effect of A. mellifera syriaca venom on U87 glioblastoma cells, with an IC50 of 14.32 µg/mL using the MTT test and an IC50 of 7.49 µg/mL using the LDH test. Cells treated with the bee venom became permeable to propidium iodide without showing any signs of early apoptosis, suggesting compromised membrane integrity but not early apoptosis. In these cells, poly (ADP-ribose) polymerase (PARP) underwent proteolytic cleavage similar to that seen in necrosis. Subsequent in vivo investigations demonstrated a significant reduction in the number of U87 cells in mice following bee venom injection, accompanied by a significant increase in cells expressing caspase-3, suggesting the occurrence of cellular apoptosis. These findings highlight the potential of A. mellifera syriaca venom as a therapeutically useful tool in the search for new drug candidates against glioblastoma and give insights into the molecular mechanism through which the venom acts on cancer cells.

Neuroprotective effects of chaperone-mediated autophagy in neurodegenerative diseases

ABSTRACT

Chaperone-mediated autophagy is one of three types of autophagy and is characterized by the selective degradation of proteins. Chaperone-mediated autophagy contributes to energy balance and helps maintain cellular homeostasis, while providing nutrients and support for cell survival. Chaperone-mediated autophagy activity can be detected in almost all cells, including neurons. Owing to the extreme sensitivity of neurons to their environmental changes, maintaining neuronal homeostasis is critical for neuronal growth and survival. Chaperone-mediated autophagy dysfunction is closely related to central nervous system diseases. It has been shown that neuronal damage and cell death are accompanied by chaperone-mediated autophagy dysfunction. Under certain conditions, regulation of chaperone-mediated autophagy activity attenuates neurotoxicity. In this paper, we review the changes in chaperone-mediated autophagy in neurodegenerative diseases, brain injury, glioma, and autoimmune diseases. We also summarize the most recent research progress on chaperone-mediated autophagy regulation and discuss the potential of chaperone-mediated autophagy as a therapeutic target for central nervous system diseases.

Ibrutinib disrupts blood-tumor barrier integrity and prolongs survival in rodent glioma model

In malignant glioma, cytotoxic drugs are often inhibited from accessing the tumor site due to the blood-tumor barrier (BTB). Ibrutinib, FDA-approved lymphoma agent, inhibits Bruton tyrosine kinase (BTK) and has previously been shown to independently impair aortic endothelial adhesion and increase rodent glioma model survival in combination with cytotoxic therapy. Yet additional research is required to understand ibrutinib's effect on BTB function. In this study, we detail baseline BTK expression in glioma cells and its surrounding vasculature, then measure endothelial junctional expression/function changes with varied ibrutinib doses in vitro. Rat glioma cells and rodent glioma models were treated with ibrutinib alone (1-10 µM and 25 mg/kg) and in combination with doxil (10-100 µM and 3 mg/kg) to assess additive effects on viability, drug concentrations, tumor volume, endothelial junctional expression and survival. We found that ibrutinib, in a dose-dependent manner, decreased brain endothelial cell-cell adhesion over 24 h, without affecting endothelial cell viability (p < 0.005). Expression of tight junction gene and protein expression was decreased maximally 4 h after administration, along with inhibition of efflux transporter, ABCB1, activity. We demonstrated an additive effect of ibrutinib with doxil on rat glioma cells, as seen by a significant reduction in cell viability (p < 0.001) and increased CNS doxil concentration in the brain (56 ng/mL doxil alone vs. 74.6 ng/mL combination, p < 0.05). Finally, Ibrutinib, combined with doxil, prolonged median survival in rodent glioma models (27 vs. 16 days, p < 0.0001) with brain imaging showing a - 53% versus - 75% volume change with doxil alone versus combination therapy (p < 0.05). These findings indicate ibrutinib's ability to increase brain endothelial permeability via junctional disruption and efflux inhibition, to increase BTB drug entry and prolong rodent glioma model survival. Our results motivate the need to identify other BTB modifiers, all with the intent of improving survival and reducing systemic toxicities.

Highly Accurate Estimation of Cell Type Abundance in Bulk Tissues Based on Single-Cell Reference and Domain Adaptive Matching

Accurately identifies the cellular composition of complex tissues, which is critical for understanding disease pathogenesis, early diagnosis, and prevention. However, current methods for deconvoluting bulk RNA sequencing (RNA-seq) typically rely on matched single-cell RNA sequencing (scRNA-seq) as a reference, which can be limiting due to differences in sequencing distribution and the potential for invalid information from single-cell references. Hence, a novel computational method named SCROAM is introduced to address these challenges. SCROAM transforms scRNA-seq and bulk RNA-seq into a shared feature space, effectively eliminating distributional differences in the latent space. Subsequently, cell-type-specific expression matrices are generated from the scRNA-seq data, facilitating the precise identification of cell types within bulk tissues. The performance of SCROAM is assessed through benchmarking against simulated and real datasets, demonstrating its accuracy and robustness. To further validate SCROAM's performance, single-cell and bulk RNA-seq experiments are conducted on mouse spinal cord tissue, with SCROAM applied to identify cell types in bulk tissue. Results indicate that SCROAM is a highly effective tool for identifying similar cell types. An integrated analysis of liver cancer and primary glioblastoma is then performed. Overall, this research offers a novel perspective for delivering precise insights into disease pathogenesis and potential therapeutic strategies.

Pharmacogenomic and epigenomic approaches to untangle the enigma of IL-10 blockade in oncology

The host immune system status remains an unresolved mystery among several malignancies. An immune-compromised state or smart immune-surveillance tactics orchestrated by cancer cells are the primary cause of cancer invasion and metastasis. Taking a closer look at the tumour-immune microenvironment, a complex network and crosstalk between infiltrating immune cells and cancer cells mediated by cytokines, chemokines, exosomal mediators and shed ligands are present. Cytokines such as interleukins can influence all components of the tumour microenvironment (TME), consequently promoting or suppressing tumour invasion based on their secreting source. Interleukin-10 (IL-10) is an interlocked cytokine that has been associated with several types of malignancies and proved to have paradoxical effects. IL-10 has multiple functions on cellular and non-cellular components within the TME. In this review, the authors shed the light on the regulatory role of IL-10 in the TME of several malignant contexts. Moreover, detailed epigenomic and pharmacogenomic approaches for the regulation of IL-10 were presented and discussed.

Blocking TGF-β- and Epithelial-to-Mesenchymal Transition (EMT)-mediated activation of vessel-associated mural cells in glioblastoma impacts tumor angiogenesis

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. GBM displays excessive and unfunctional vascularization which may, among others, be a reason for its devastating prognosis. Pericytes have been identified as the major component of the irregular vessel structure in GBM. In vitro data suggest an epithelial-to-mesenchymal transition (EMT)-like activation of glioma-associated pericytes, stimulated by GBM-secreted TGF-β, to be involved in the formation of a chaotic and dysfunctional tumor vasculature. This study investigated whether TGF-β impacts the function of vessel associated mural cells (VAMCs) in vivo via the induction of the EMT transcription factor SLUG and whether this is associated with the development of GBM-associated vascular abnormalities. Upon preventing the TGF-β-/SLUG-mediated EMT induction in VAMCs, the number of PDGFRβ and αSMA positive cells was significantly reduced, regardless of whether TGF-β secretion by GBM cells was blocked or whether SLUG was specifically knocked out in VAMCs. The reduced amount of PDGFRβ+ or αSMA+ cells observed under those conditions correlated with a lower vessel density and fewer vascular abnormalities. Our data provide evidence that the SLUG-mediated modulation of VAMC activity is induced by GBM-secreted TGF-β¬ and that activated VAMCs are key contributors in neo-angiogenic processes. We suggest that a pathologically altered activation of GA-Peris in the tumor microenvironment is responsible for the unstructured tumor vasculature. There is emerging evidence that vessel normalization alleviates tumor hypoxia, reduces tumor-associated edema and improves drug delivery. Therefore, avoiding the generation of an unstructured and non-functional tumor vasculature during tumor recurrence might be a promising treatment approach for GBM and identifies pericytes as a potential novel therapeutic target.

Stromal cells in the tumor microenvironment: accomplices of tumor progression?

The tumor microenvironment (TME) is made up of cells and extracellular matrix (non-cellular component), and cellular components include cancer cells and non-malignant cells such as immune cells and stromal cells. These three types of cells establish complex signals in the body and further influence tumor genesis, development, metastasis and participate in resistance to anti-tumor therapy. It has attracted scholars to study immune cells in TME due to the significant efficacy of immune checkpoint inhibitors (ICI) and chimeric antigen receptor T (CAR-T) in solid tumors and hematologic tumors. After more than 10 years of efforts, the role of immune cells in TME and the strategy of treating tumors based on immune cells have developed rapidly. Moreover, ICI have been recommended by guidelines as first- or second-line treatment strategies in a variety of tumors. At the same time, stromal cells is another major class of cellular components in TME, which also play a very important role in tumor metabolism, growth, metastasis, immune evasion and treatment resistance. Stromal cells can be recruited from neighboring non-cancerous host stromal cells and can also be formed by transdifferentiation from stromal cells to stromal cells or from tumor cells to stromal cells. Moreover, they participate in tumor genesis, development and drug resistance by secreting various factors and exosomes, participating in tumor angiogenesis and tumor metabolism, regulating the immune response in TME and extracellular matrix. However, with the deepening understanding of stromal cells, people found that stromal cells not only have the effect of promoting tumor but also can inhibit tumor in some cases. In this review, we will introduce the origin of stromal cells in TME as well as the role and specific mechanism of stromal cells in tumorigenesis and tumor development and strategies for treatment of tumors based on stromal cells. We will focus on tumor-associated fibroblasts (CAFs), mesenchymal stem cells (MSCs), tumor-associated adipocytes (CAAs), tumor endothelial cells (TECs) and pericytes (PCs) in stromal cells.

Occludin Regulates HIV-1 Infection by Modulation of the Interferon Stimulated OAS Gene Family

HIV-1-associated blood brain barrier (BBB) alterations and neurocognitive disorders are frequent clinical manifestations in HIV-1 infected patients. The BBB is formed by cells of the neurovascular unit (NVU) and sealed together by tight junction proteins, such as occludin (ocln). Pericytes are a key cell type of NVU that can harbor HIV-1 infection via a mechanism that is regulated, at least in part, by ocln. After viral infection, the immune system starts the production of interferons, which induce the expression of the 2'-5'-oligoadenylate synthetase (OAS) family of interferon stimulated genes and activate the endoribonuclease RNaseL that provides antiviral protection by viral RNA degradation. The current study evaluated the involvement of the OAS genes in HIV-1 infection of cells of NVU and the role of ocln in controlling OAS antiviral signaling pathway. We identified that ocln modulates the expression levels of the OAS1, OAS2, OAS3, and OASL genes and proteins and, in turn, that the members of the OAS family can influence HIV replication in human brain pericytes. Mechanistically, this effect was regulated via the STAT signaling. HIV-1 infection of pericytes significantly upregulated expression of all OAS genes at the mRNA level but selectively OAS1, OAS2, and OAS3 at the protein level. Interestingly no changes were found in RNaseL after HIV-1 infection. Overall, these results contribute to a better understanding of the molecular mechanisms implicated in the regulation of HIV-1 infection in human brain pericytes and suggest a novel role for ocln in controlling of this process.

Pericyte stem cells induce Ly6G+ cell accumulation and immunotherapy resistance in pancreatic cancer

We report the identification of a cell population that shares pericyte, stromal and stemness features, does not harbor the Kras^G12D mutation and drives tumoral growth in vitro and in vivo. We term these cells pericyte stem cells (PeSCs) and define them as CD45^- EPCAM^- CD29⁺ CD106⁺ CD24⁺ CD44⁺ cells. We perform studies with p48-Cre;Kras^G12D (KC), pdx1-Cre;Kras^G12D ;Ink4a/Arf^fl/fl (KIC) and pdx1-Cre;Kras^G12D ;p53^R172H (KPC) and tumor tissues from PDAC and chronic pancreatitis patients. We also perform single-cell RNAseq analysis and reveal a unique signature of PeSC. Under steady-state conditions, PeSCs are barely detectable in the pancreas but present in the neoplastic microenvironment both in humans and mice. The coinjection of PeSCs and tumor epithelial cells leads to increased tumor growth, differentiation of Ly6G⁺ myeloid-derived suppressor cells, and a decreased amount of F4/80⁺ macrophages and CD11c⁺ dendritic cells. This population induces resistance to anti-PD-1 immunotherapy when coinjected with epithelial tumor cells. Our data reveal the existence of a cell population that instructs immunosuppressive myeloid cell responses to bypass PD-1 targeting and thus suggest potential new approaches for overcoming resistance to immunotherapy in clinical settings.

Tissue-resident glial cells associate with tumoral vasculature and promote cancer progression

Cancer cells are embedded within the tissue and interact dynamically with its components during cancer progression. Understanding the contribution of cellular components within the tumor microenvironment is crucial for the success of therapeutic applications. Here, we reveal the presence of perivascular GFAP+/Plp1+ cells within the tumor microenvironment. Using in vivo inducible Cre/loxP mediated systems, we demonstrated that these cells derive from tissue-resident Schwann cells. Genetic ablation of endogenous Schwann cells slowed down tumor growth and angiogenesis. Schwann cell-specific depletion also induced a boost in the immune surveillance by increasing tumor-infiltrating anti-tumor lymphocytes, while reducing immune-suppressor cells. In humans, a retrospective in silico analysis of tumor biopsies revealed that increased expression of Schwann cell-related genes within melanoma was associated with improved survival. Collectively, our study suggests that Schwann cells regulate tumor progression, indicating that manipulation of Schwann cells may provide a valuable tool to improve cancer patients' outcomes.

Occludin regulates HIV-1 infection by modulation of the interferon stimulated OAS gene family

HIV-1-associated blood brain barrier (BBB) alterations and neurocognitive disorders are frequent clinical manifestations in HIV-1 infected patients. The BBB is formed by cells of the neurovascular unit (NVU) and sealed together by tight junction (TJ) proteins, such as occludin (ocln). Pericytes are a key cell type of NVU that can harbor HIV-1 infection via a mechanism that is regulated, at least in part, by ocln. After viral infection, the immune system starts the production of interferons, which induce the expression of the 2'-5'-oligoadenylate synthetase (OAS) family of interferon stimulated genes and activate the endoribonuclease RNaseL that provides antiviral protection by viral RNA degradation. The current study evaluated the involvement of the OAS genes in HIV-1 infection of cells of NVU and the role of ocln in controlling OAS antiviral signaling pathway. We identified that ocln modulates the expression levels of the OAS1, OAS2, OAS3, and OASL genes and proteins and, in turn, that the members of the OAS family can influence HIV replication in human brain pericytes. Mechanistically, this effect was regulated via the STAT signaling. HIV-1 infection of pericytes significantly upregulated expression of all OAS genes at the mRNA level but selectively OAS1, OAS2 and OAS3 at the protein level. Interestingly no changes were found in RNaseL after HIV-1 infection. Overall, these results contribute to a better understanding of the molecular mechanisms implicated in the regulation of HIV-1 infection in human brain pericytes and suggest a novel role for ocln in controlling of this process.

Targeting the tumor stroma for cancer therapy

Tumors are comprised of both cancer cells and surrounding stromal components. As an essential part of the tumor microenvironment, the tumor stroma is highly dynamic, heterogeneous and commonly tumor-type specific, and it mainly includes noncellular compositions such as the extracellular matrix and the unique cancer-associated vascular system as well as a wide variety of cellular components including activated cancer-associated fibroblasts, mesenchymal stromal cells, pericytes. All these elements operate with each other in a coordinated fashion and collectively promote cancer initiation, progression, metastasis and therapeutic resistance. Over the past few decades, numerous studies have been conducted to study the interaction and crosstalk between stromal components and neoplastic cells. Meanwhile, we have also witnessed an exponential increase in the investigation and recognition of the critical roles of tumor stroma in solid tumors. A series of clinical trials targeting the tumor stroma have been launched continually. In this review, we introduce and discuss current advances in the understanding of various stromal elements and their roles in cancers. We also elaborate on potential novel approaches for tumor-stroma-based therapeutic targeting, with the aim to promote the leap from bench to bedside.

Innovative Approaches for Breast Cancer Metastasis to the Brain

Breast cancer metastasis is a continued concern for patients with recent development in our understanding of disease progression. In this paper, we highlight the pathophysiology behind breast cancer metastasis. Blood brain barrier disruption plays a critical component in progression. We then investigate the current treatment strategies and recommended guidelines. This focuses on radiation and medical management. Finally, we address the role of surgical intervention. The data is organized into tables and figures to highlight key components. Finally, we address emerging treatments and pre-clinical data. The paper will serve as a user-friendly guide for clinicians and researchers to help formulate a strategy to manage breast cancer metastasis patients sufficiently.

Identification of early biomarkers in saliva in genetically engineered mouse model C(3)1-TAg of breast cancer

Breast cancer is one of leading causes of death worldwide in the female population. Deaths from breast cancer could be reduced significantly through earlier and more efficient detection of the disease. Saliva, an oral fluid that contains an abundance of protein biomarkers, has been recognized as a promising diagnostic biofluid that is easy to isolate through non-invasive techniques. Assays on saliva can be performed rapidly and are cost-effective. Therefore, our work aimed to identify salivary biomarkers present in the initial stages of breast cancer, where cell alterations are not yet detectable by histopathological analysis. Using state-of-the-art techniques, we employed a transgenic mouse model of mammary cancer to identify molecular changes in precancerous stage breast cancer through protein analysis in saliva. Through corroborative molecular approaches, we established that proteins related to metabolic changes, inflammatory process and cell matrix degradation are detected in saliva at the onset of tumor development. Our work demonstrated that salivary protein profiles can be used to identify cellular changes associated with precancerous stage breast cancer through non-invasive means even prior to biopsy-evident disease.

Glioma Pericytes Promote Angiogenesis by Producing Periostin

Glioma is the prevalent aggressive primary brain tumor, with a very poor prognosis. The absence of advanced understanding of the roles played by the cells within the glioma microenvironment limits the development of effective drugs. A recent study indicates that periostin expressed by pericytes is crucial for glioma angiogenesis. Here, we describe succinctly the results and implications of this discovery in what we know about pericytes within the glioma microenvironment. The emerging knowledge from this work will benefit the development of therapies for gliomas.

ITGA5 Predicts Dual-Drug Resistance to Temozolomide and Bevacizumab in Glioma

AIMS

Anti-angiotherapy (Bevacizumab) is currently regarded as a promising option for glioma patients who are resistant to temozolomide (TMZ) treatment. But ongoing clinical research failed to meet therapeutic expectations. This study aimed to explore the pivotal genetic feature responsible for TMZ and Bevacizumab resistance in glioma patients.

METHODS

We downloaded the transcriptomic and methylation data of glioma patients from The Cancer Genome Atlas (TCGA), Chinese Glioma Genome Atlas (CGGA), and Gene Expression Omnibus (GEO) databases and grouped these patients into resistant and non-resistant groups based on their clinical profiles. Differentially expressed genes and pathways were identified and exhibited with software in R platform. A TMZ-resistant cell line was constructed for validating the expression change of the candidate gene, ITGA5. An ITGA5-overexpressing cell line was also constructed to investigate its biological function using the CCK8 assay, Western blot, periodic acid-Schiff (PAS) staining, and transcriptional sequencing.

RESULTS

Change of the cell morphology and polarity was closely associated with TMZ mono-resistance and TMZ/Bevacizumab dual resistance in glioma patients. The expression level of ITGA5 was effective in determining drug resistance and the outcome of glioma patients, which is regulated by methylation on two distinct sites. ITGA5 was augmented in TMZ-resistant glioma cells, while overexpressing ITGA5 altered the cell-promoted TMZ resistance through enhancing vascular mimicry (VM) formation correspondingly.

CONCLUSIONS

Both the epigenetic and transcriptional levels of ITGA5 are effective in predicting TMZ and Bevacizumab resistance, indicating that ITGA5 may serve as a predictor of the treatment outcomes of glioma patients.

Size-dependent chemosensitization of doxorubicin-loaded polymeric nanoparticles for malignant glioma chemotherapy

Chemotherapy is a traditional treatment method in clinical cancer treatment. However, it is limited due to the large toxic side effects of chemotherapeutics. Nanomedicines have shown great potential in the application of tumor therapy. The size of nanoparticles as a crucial factor in the enhanced permeability and retention (EPR) effect can be regulated for the enhanced chemotherapy. Therefore, we believe that regulation of nanoparticle size can be used as an effective sensitizer to enhance the therapeutic effect of chemotherapy drugs on tumors. Here, we prepared several nanoparticles of different hydrodynamic diameters commonly found in nanomedical applications by the diblock copolymer of methoxy polyethylene glycol-poly (ϵ -caprolactone) (mPEG-PCL). The blood circulation effect and organ distribution in blood were detected by fluorescence labeled nanoparticles. We found that the small-sized nanoparticles exhibited much longer blood circulation time than the large-sized nanoparticles in vivo, and thus the nanoparticle concentration in the tumor tissue was relatively high. Systematic injection of the doxorubicin (DOX) loaded nanoparticles can effectively inhibit tumor growth. Compared to the free drug, tumor cells were much more sensitive to DOX loaded nanoparticles of small size. Our nano-drug delivery system has been proven to be safe and nontoxic in vivo and was suitable for use as a sensitizer in clinical oncology chemotherapy.

Modulation of the Blood-Brain Barrier for Drug Delivery to Brain

The blood-brain barrier (BBB) precisely controls brain microenvironment and neural activity by regulating substance transport into and out of the brain. However, it severely hinders drug entry into the brain, and the efficiency of various systemic therapies against brain diseases. Modulation of the BBB via opening tight junctions, inhibiting active efflux and/or enhancing transcytosis, possesses the potential to increase BBB permeability and improve intracranial drug concentrations and systemic therapeutic efficiency. Various strategies of BBB modulation have been reported and investigated preclinically and/or clinically. This review describes conventional and emerging BBB modulation strategies and related mechanisms, and safety issues according to BBB structures and functions, to try to give more promising directions for designing more reasonable preclinical and clinical studies.

Clinical Trials of the BTK Inhibitors Ibrutinib and Acalabrutinib in Human Diseases Beyond B Cell Malignancies

The BTK inhibitors ibrutinib and acalabrutinib are FDA-approved drugs for the treatment of B cell malignances. Both drugs have demonstrated clinical efficacy and safety profiles superior to chemoimmunotherapy regimens in patients with chronic lymphocytic leukemia. Mounting preclinical and clinical evidence indicates that both ibrutinib and acalabrutinib are versatile and have direct effects on many immune cell subsets as well as other cell types beyond B cells. The versatility and immunomodulatory effects of both drugs have been exploited to expand their therapeutic potential in a wide variety of human diseases. Over 470 clinical trials are currently registered at ClinicalTrials.gov to test the efficacy of ibrutinib or acalabrutinib not only in almost every type of B cell malignancies, but also in hematological malignancies of myeloid cells and T cells, solid tumors, chronic graft versus host disease (cGHVD), autoimmune diseases, allergy and COVID-19 (http:www.clinicaltrials.gov). In this review, we present brief discussions of the clinical trials and relevant key preclinical evidence of ibrutinib and acalabrutinib as monotherapies or as part of combination therapies for the treatment of human diseases beyond B cell malignancies. Adding to the proven efficacy of ibrutinib for cGVHD, preliminary results of clinical trials have shown promising efficacy of ibrutinib or acalabrutinib for certain T cell malignancies, allergies and severe COVID-19. However, both BTK inhibitors have no or limited efficacy for refractory or recurrent solid tumors. These clinical data together with additional pending results from ongoing trials will provide valuable information to guide the design and improvement of future trials, including optimization of combination regimens and dosing sequences as well as better patient stratification and more efficient delivery strategies. Such information will further advance the precise implementation of BTK inhibitors into the clinical toolbox for the treatment of different human diseases.

Sympathetic nerve-adipocyte interactions in response to acute stress

Psychological stress predisposes our body to several disorders. Understanding the cellular and molecular mechanisms involved in the physiological responses to psychological stress is essential for the success of therapeutic applications. New studies show, by using in vivo inducible Cre/loxP-mediated approaches in combination with pharmacological blockage, that sympathetic nerves, activated by psychological stress, induce brown adipocytes to produce IL-6. Strikingly, this cytokine promotes gluconeogenesis in hepatocytes, that results in the decline of tolerance to inflammatory organ damage. The comprehension arising from this research will be crucial for the handling of many inflammatory diseases. Here, we review recent advances in our comprehension of the sympathetic nerve-adipocyte axis in the tissue microenvironment.

Lung-Resident Mesenchymal Stem Cell Fates within Lung Cancer

Simple Summary

Lung cancer remains the leading cause of cancer-related deaths worldwide. Herein, the heterogeneous tumor stroma decisively impacts on tumor progression, therapy resistance, and, thus, poor clinical outcome. Among the numerous non-epithelial cells constructing the complex environment of lung carcinomas, mesenchymal stem cells (MSC) gained attraction being stromal precursor cells that could be recruited and ‘educated’ by lung cancer cells to adopt a tumor-associated MSC phenotype, serve as source for activated fibroblasts and presumably for vascular mural cells finally reinforcing tumor progression. Lung-resident MSCs should be considered as ‘local MSCs in stand by’ ready to be arranged within the cancer stroma.

Abstract

Lung-resident mesenchymal stem cells (LR-MSCs) are non-hematopoietic multipotent stromal cells that predominately reside adventitial within lung blood vessels. Based on their self-renewal and differentiation properties, LR-MSCs turned out to be important regulators of normal lung homeostasis. LR-MSCs exert beneficial effects mainly by local secretion of various growth factors and cytokines that in turn foster pulmonary regeneration including suppression of inflammation. At the same time, MSCs derived from various tissues of origins represent the first choice of cells for cell-based therapeutic applications in clinical medicine. Particularly for various acute as well as chronic lung diseases, the therapeutic applications of exogenous MSCs were shown to mediate beneficial effects, hereby improving lung function and survival. In contrast, endogenous MSCs of normal lungs seem not to be sufficient for lung tissue protection or repair following a pathological trigger; LR-MSCs could even contribute to initiation and/or progression of lung diseases, particularly lung cancer because of their inherent tropism to migrate towards primary tumors and metastatic sites. However, the role of endogenous LR-MSCs to be multipotent tumor-associated (stromal) precursors remains to be unraveled. Here, we summarize the recent knowledge how ‘cancer-educated’ LR-MSCs impact on lung cancer with a focus on mesenchymal stem cell fates.

Microphysiological systems to study tumor-stroma interactions in brain cancer

Brain tumors still lack effective treatments, and the mechanisms of tumor progression and therapeutic resistance are unclear. Multiple parameters affect cancer prognosis (e.g., type and grade, age, location, size, and genetic mutations) and election of suitable treatments is based on preclinical models and clinical data. However, most candidate drugs fail in human trials due to inefficacy. Cell lines and tissue culture plates do not provide physiologically relevant environments, and animal models are not able to adequately mimic characteristics of disease in humans. Therefore, increasing technological advances are focusing on in vitro and computational modeling to increase the throughput and predicting capabilities of preclinical systems. The extensive use of these therapeutic agents requires a more profound understanding of the tumor-stroma interactions, including neural tissue, extracellular matrix, blood-brain barrier, astrocytes and microglia. Microphysiological brain tumor models offer physiologically relevant vascularized 'minitumors' that can help deciphering disease mechanisms, accelerating the drug discovery and predicting patient's response to anticancer treatments. This article reviews progress in tumor-on-a-chip platforms that are designed to comprehend the particular roles of stromal cells in the brain tumor microenvironment.

Pericytes: Intrinsic Transportation Engineers of the CNS Microcirculation

Pericytes in the brain are candidate regulators of microcirculatory blood flow because they are strategically positioned along the microvasculature, contain contractile proteins, respond rapidly to neuronal activation, and synchronize microvascular dynamics and neurovascular coupling within the capillary network. Analyses of mice with defects in pericyte generation demonstrate that pericytes are necessary for the formation of the blood-brain barrier, development of the glymphatic system, immune homeostasis, and white matter function. The development, identity, specialization, and progeny of different subtypes of pericytes, however, remain unclear. Pericytes perform brain-wide 'transportation engineering' functions in the capillary network, instructing, integrating, and coordinating signals within the cellular communicome in the neurovascular unit to efficiently distribute oxygen and nutrients ('goods and services') throughout the microvasculature ('transportation grid'). In this review, we identify emerging challenges in pericyte biology and shed light on potential pericyte-targeted therapeutic strategies.

Angiogenesis as a hallmark of solid tumors - clinical perspectives

BACKGROUND

Angiogenesis is a key and early step in tumorigenesis, and is known as a hallmark of solid tumors and a key promoter of tumor recurrence. Unlike normal tissue vessels, the architecture of the tumor vasculature is abnormal, being leaky, tortuous, fragile and blind-ended. Perivascular cells are either detached or absent, causing reduction of vascular integrity, an increase in vessel immaturity, incoherent perfusion, defective functionality and enhanced tumor dissemination and metastasis. The abnormal tumor vasculature along with the defective tumor vessel functionality finally causes bouts of hypoxia and acidity in the tumor microenvironment (TME), further reinvigorating tumor aggression. Interstitial hypertension or high interstitial fluid pressure (IFP) is an outcome of tumor hyper-permeability. High IFP can be a barrier for either effective delivery of anti-cancer drugs toward the TME or accumulation of drugs within the tumor area, thus promoting tumor resistance to therapy. Some tumors do, however, not undergo angiogenesis but instead undergo vessel co-option or vascular mimicry, thereby adding another layer of complexity to cancer development and therapy.

CONCLUSIONS

Combination of anti-angiogenesis therapy with chemotherapy and particularly with immune checkpoint inhibitors (ICIs) is a promising strategy for a number of advanced cancers. Among the various approaches for targeting tumor angiogenesis, vascular normalization is considered as the most desired method, which allows effective penetration of chemotherapeutics into the tumor area, thus being an appropriate adjuvant to other cancer modalities.

The adaptive transition of glioblastoma stem cells and its implications on treatments

Glioblastoma is the most malignant tumor occurring in the human central nervous system with overall median survival time <14.6 months. Current treatments such as chemotherapy and radiotherapy cannot reach an optimal remission since tumor resistance to therapy remains a challenge. Glioblastoma stem cells are considered to be responsible for tumor resistance in treating glioblastoma. Previous studies reported two subtypes, proneural and mesenchymal, of glioblastoma stem cells manifesting different sensitivity to radiotherapy or chemotherapy. Mesenchymal glioblastoma stem cells, as well as tumor cells generate from which, showed resistance to radiochemotherapies. Besides, two metabolic patterns, glutamine or glucose dependent, of mesenchymal glioblastoma stem cells also manifested different sensitivity to radiochemotherapies. Glutamine dependent mesenchymal glioblastoma stem cells are more sensitive to radiotherapy than glucose-dependent ones. Therefore, the transition between proneural and mesenchymal subtypes, or between glutamine-dependent and glucose-dependent, might lead to tumor resistance to radiochemotherapies. Moreover, neural stem cells were also hypothesized to participate in glioblastoma stem cells mediated tumor resistance to radiochemotherapies. In this review, we summarized the basic characteristics, adaptive transition and implications of glioblastoma stem cells in glioblastoma therapy.

Neural crest cell-derived pericytes act as pro-angiogenic cells in human neocortex development and gliomas

Central nervous system diseases involving the parenchymal microvessels are frequently associated with a ‘microvasculopathy’, which includes different levels of neurovascular unit (NVU) dysfunction, including blood–brain barrier alterations. To contribute to the understanding of NVU responses to pathological noxae, we have focused on one of its cellular components, the microvascular pericytes, highlighting unique features of brain pericytes with the aid of the analyses carried out during vascularization of human developing neocortex and in human gliomas. Thanks to their position, centred within the endothelial/glial partition of the vessel basal lamina and therefore inserted between endothelial cells and the perivascular and vessel-associated components (astrocytes, oligodendrocyte precursor cells (OPCs)/NG2-glia, microglia, macrophages, nerve terminals), pericytes fulfil a central role within the microvessel NVU. Indeed, at this critical site, pericytes have a number of direct and extracellular matrix molecule- and soluble factor-mediated functions, displaying marked phenotypical and functional heterogeneity and carrying out multitasking services. This pericytes heterogeneity is primarily linked to their position in specific tissue and organ microenvironments and, most importantly, to their ontogeny. During ontogenesis, pericyte subtypes belong to two main embryonic germ layers, mesoderm and (neuro)ectoderm, and are therefore expected to be found in organs ontogenetically different, nonetheless, pericytes of different origin may converge and colonize neighbouring areas of the same organ/apparatus. Here, we provide a brief overview of the unusual roles played by forebrain pericytes in the processes of angiogenesis and barriergenesis by virtue of their origin from midbrain neural crest stem cells. A better knowledge of the ontogenetic subpopulations may support the understanding of specific interactions and mechanisms involved in pericyte function/dysfunction, including normal and pathological angiogenesis, thereby offering an alternative perspective on cell subtype-specific therapeutic approaches.

Neural crest cell-derived pericytes act as pro-angiogenic cells in human neocortex development and gliomas

Central nervous system diseases involving the parenchymal microvessels are frequently associated with a ‘microvasculopathy’, which includes different levels of neurovascular unit (NVU) dysfunction, including blood–brain barrier alterations. To contribute to the understanding of NVU responses to pathological noxae, we have focused on one of its cellular components, the microvascular pericytes, highlighting unique features of brain pericytes with the aid of the analyses carried out during vascularization of human developing neocortex and in human gliomas. Thanks to their position, centred within the endothelial/glial partition of the vessel basal lamina and therefore inserted between endothelial cells and the perivascular and vessel-associated components (astrocytes, oligodendrocyte precursor cells (OPCs)/NG2-glia, microglia, macrophages, nerve terminals), pericytes fulfil a central role within the microvessel NVU. Indeed, at this critical site, pericytes have a number of direct and extracellular matrix molecule- and soluble factor-mediated functions, displaying marked phenotypical and functional heterogeneity and carrying out multitasking services. This pericytes heterogeneity is primarily linked to their position in specific tissue and organ microenvironments and, most importantly, to their ontogeny. During ontogenesis, pericyte subtypes belong to two main embryonic germ layers, mesoderm and (neuro)ectoderm, and are therefore expected to be found in organs ontogenetically different, nonetheless, pericytes of different origin may converge and colonize neighbouring areas of the same organ/apparatus. Here, we provide a brief overview of the unusual roles played by forebrain pericytes in the processes of angiogenesis and barriergenesis by virtue of their origin from midbrain neural crest stem cells. A better knowledge of the ontogenetic subpopulations may support the understanding of specific interactions and mechanisms involved in pericyte function/dysfunction, including normal and pathological angiogenesis, thereby offering an alternative perspective on cell subtype-specific therapeutic approaches.

A vasculature-centric approach to developing novel treatment options for glioblastoma

Introduction: Glioblastoma is invariably deadly and is characterized by extensive vascularization and macrophage-dominant immunosuppression; nevertheless, anti-angiogenesis has so far failed to prolong overall survival of patients. Regardless of the problems in clinical development, the rationale for the application of anti-angiogenics in glioblastoma remains.Areas covered: Resistance to anti-angiogenics is discussed, including vessel co-option and amplification of hypoxic signaling in response to vessel destruction. The modulation of GSC and tumor-associated macrophages by dysfunctional tumor vessels and by hypoxia are outlined. Pharmacologic approaches to sensitizing glioblastomas to anti-angiogenics and evidence for the cooperation of anti-angiogenics with immunotherapies are summarized. Database search: https://pubmed.ncbi.nlm.nih.gov prior to December 12, 2020.Expert opinion: Despite drawbacks in the clinical development of vascular endothelial growth factor A (VEGF)-targeted agents, there is still rationale for the use of anti-angiogenics. The better understanding of vascular co-option and adverse effects of blood vessel destruction guides to improve strategies for vascular targeting. The pivotal role of the vasculature and of angiogenic factors such as VEGF for the induction and maintenance of immunosuppression in glioblastoma supports the use of anti-angiogenics in combination with immunotherapy. Proinflammatory repolarization of perivascular and perinecrotic tumor-associated macrophages is probably paramount for overcoming treatment resistance to virtually any treatment.

The Multifaceted Role of CMA in Glioma: Enemy or Ally?

Chaperone-mediated autophagy (CMA) is a catabolic pathway fundamental for cell homeostasis, by which specific damaged or non-essential proteins are degraded. CMA activity has three main levels of regulation. The first regulatory level is based on the targetability of specific proteins possessing a KFERQ-like domain, which can be recognized by specific chaperones and delivered to the lysosomes. Target protein unfolding and translocation into the lysosomal lumen constitutes the second level of CMA regulation and is based on the modulation of Lamp2A multimerization. Finally, the activity of some accessory proteins represents the third regulatory level of CMA activity. CMA's role in oncology has not been fully clarified covering both pro-survival and pro-death roles in different contexts. Taking all this into account, it is possible to comprehend the actual complexity of both CMA regulation and the cellular consequences of its activity allowing it to be elected as a modulatory and not only catabolic machinery. In this review, the role covered by CMA in oncology is discussed with a focus on its relevance in glioma. Molecular correlates of CMA importance in glioma responsiveness to treatment are described to identify new early efficacy biomarkers and new therapeutic targets to overcome resistance.

Tumor-Derived Pericytes Driven by EGFR Mutations Govern the Vascular and Immune Microenvironment of Gliomas

The extraordinary plasticity of glioma cells allows them to contribute to different cellular compartments in tumor vessels, reinforcing the vascular architecture. It was recently revealed that targeting glioma-derived pericytes, which represent a big percentage of the mural cell population in aggressive tumors, increases the permeability of the vessels and improves the efficiency of chemotherapy. However, the molecular determinants of this transdifferentiation process have not been elucidated. Here we show that mutations in EGFR stimulate the capacity of glioma cells to function as pericytes in a BMX- (bone marrow and X-linked) and SOX9-dependent manner. Subsequent activation of platelet-derived growth factor receptor beta in the vessel walls of EGFR-mutant gliomas stabilized the vasculature and facilitated the recruitment of immune cells. These changes in the tumor microenvironment conferred a growth advantage to the tumors but also rendered them sensitive to pericyte-targeting molecules such as ibrutinib or sunitinib. In the absence of EGFR mutations, high-grade gliomas were enriched in blood vessels, but showed a highly disrupted blood-brain barrier due to the decreased BMX/SOX9 activation and pericyte coverage, which led to poor oxygenation, necrosis, and hypoxia. Overall, these findings identify EGFR mutations as key regulators of the glioma-to-pericyte transdifferentiation, highlighting the intricate relationship between the tumor cells and their vascular and immune milieu. Our results lay the foundations for a vascular-dependent stratification of gliomas and suggest different therapeutic vulnerabilities determined by the genetic status of EGFR. SIGNIFICANCE: This study identifies the EGFR-related mechanisms that govern the capacity of glioma cells to transdifferentiate into pericytes, regulating the vascular and immune phenotypes of the tumors. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/8/2142/F1.large.jpg.

Microglia in the Brain Tumor Microenvironment

Microglia are the brain resident phagocytes that act as the primary form of the immune defense in the central nervous system. These cells originate from primitive macrophages that arise from the yolk sac. Advances in imaging and single-cell RNA-seq technologies provided new insights into the complexity of microglia biology.Microglia play an essential role in the brain development and maintenance of brain homeostasis. They are also crucial in injury repair in the central nervous system. The tumor microenvironment is complex and includes neoplastic cells as well as varieties of host and infiltrating immune cells. Microglia are part of the glioma microenvironment and play a critical part in initiating and maintaining tumor growth and spread. Microglia can also act as effector cells in treatments against gliomas. In this chapter, we summarize the current knowledge of how and where microglia are generated. We also discuss their functions during brain development, injury repair, and homeostasis. Moreover, we discuss the role of microglia in the tumor microenvironment of gliomas and highlight their therapeutic implications.

Pericyte in Oral Squamous Cell Carcinoma: A Systematic Review

The microenvironment of oral cancer is highly dynamic and has been proved to affect tumor progression. Pericytes are blood vessels surrounding cells that have recently gained attention for their roles in vascular and cancer biology. The objective of the present study was to survey the scientific literature for conclusive evidence about whether pericytes are part of blood vessels in oral squamous cell carcinoma (OSCC) and their roles in the tumor microenvironment and clinical outcomes. A systematic electronic search was undertaken in Medline Ovid, PubMed, Web of Science, and Scopus. Eligibility criteria were: publications adopting in vivo models of OSCC that included pericyte detection and assessment by pericyte markers (e.g., α-smooth muscle actin, neuron-glial antigen 2 and platelet-derived growth factor receptor-β). The search yielded seven eligible studies (from 2008 to 2018). The markers most commonly used for pericyte detection were α-smooth muscle actin and neuron-glial antigen 2. The studies reviewed showed the presence of immature vessels exhibiting a reduction of pericyte coverage in OSCC and indicated that anti-cancer therapies could contribute to vessel normalization and pericyte regain. The pericyte population is significantly affected during OSCC development and cancer therapy. While these findings might suggest a role for pericytes in OSCC progression, the limited data available do not allow us to conclude whether they modify the tumor microenvironment and clinical outcome.

Occludin, caveolin-1, and Alix form a multi-protein complex and regulate HIV-1 infection of brain pericytes

HIV-1 enters the brain by altering properties of the blood-brain barrier (BBB). Recent evidence indicates that among cells of the BBB, pericytes are prone to HIV-1 infection. Occludin (ocln) and caveolin-1 (cav-1) are critical determinants of BBB integrity that can regulate barrier properties of the BBB in response to HIV-1 infection. Additionally, Alix is an early acting endosomal factor involved in HIV-1 budding from the cells. The aim of the present study was to evaluate the role of cav-1, ocln, and Alix in HIV-1 infection of brain pericytes. Our results indicated that cav-1, ocln, and Alix form a multi-protein complex in which they cross-regulate each other's expression. Importantly, the stability of this complex was affected by HIV-1 infection. Modifications of the complex resulted in diminished HIV-1 infection and alterations of the cytokine profile produced by brain pericytes. These results identify a novel mechanism involved in HIV-1 infection contributing to a better understanding of the HIV-1 pathology and the associated neuroinflammatory responses.

Sensory nerves in the spotlight of the stem cell niche

Niches are specialized tissue microenvironments that control stem cells functioning. The bone marrow mesenchymal stem cell niche defines a location within the marrow in which mesenchymal stem cells are retained and produce new cells throughout life. Deciphering the signaling mechanisms by which the niche regulates stem cell fate will facilitate the use of these cells for therapy. Recent studies, by using state-of-the-art methodologies, including sophisticated in vivo inducible genetic techniques, such as lineage-tracing Cre/loxP mediated systems, in combination with pharmacological inhibition, provide evidence that sensory neuron is an important component of the bone marrow mesenchymal stem cell niche. Strikingly, knockout of a specific receptor in sensory neurons blocked stem cell function in the bone marrow. The knowledge arising from these discoveries will be crucial for stem cell manipulation in the future. Here, we review recent progress in our understanding of sensory nerves biology in the stem cell niche.

Lipoproteins and the Tumor Microenvironment

The tumor microenvironment (TME) plays a key role in enhancing the growth of malignant tumors and thus contributing to "aggressive phenotypes," supporting sustained tumor growth and metastasis. The precise interplay between the numerous components of the TME that contribute to the emergence of these aggressive phenotypes is yet to be elucidated and currently under intense investigation. The purpose of this article is to identify specific role(s) for lipoproteins as part of these processes that facilitate (or oppose) malignant growth as they interact with specific components of the TME during tumor development and treatment. Because of the scarcity of literature reports regarding the interaction of lipoproteins with the components of the tumor microenvironment, we were compelled to explore topics that were only tangentially related to this topic, to ensure that we have not missed any important concepts.

Modulating microenvironments for treating glioblastoma

Purpose of review

This review focuses on the development and progression of glioblastoma through the brain and glioma microenvironment. Specifically we highlight how the tumor microenvironment contributes to the hallmarks of cancer in hopes of offering novel therapeutic options and tools to target this microenvironment.

Recent findings

The hallmarks of cancer, which represent elements of cancers that contribute to the disease's malignancy, yet elements within the brain tumor microenvironment, such as other cellular types as well as biochemical and biophysical cues that can each uniquely affect tumor cells, have not been well-described in this context and serve as potential targets for modulation.

Summary

Here, we highlight how the brain tumor microenvironment contributes to the progression and therapeutic response of tumor cells. Specifically, we examine these contributions through the lens of Hanahan & Weinberg's Hallmarks of Cancer in order to identify potential novel targets within the brain that may offer a means to treat brain cancers, including the deadliest brain cancer, glioblastoma.

Stellate Cells in the Tumor Microenvironment

As tumor microenvironments share many of the same qualities as chronic wounds, attention is turning to the wound-repair cells that support the growth of cancerous cells. Stellate cells are star-shaped cells that were first discovered in the perisinusoidal spaces in the liver and have been found to support wound healing by the secretion of growth factors and extracellular matrix. They have since been also found to serve a similar function in the pancreas. In both organs, the wound-healing process may become dysregulated and lead to pathological fibrosis (also known as cirrhosis in the liver). In recent years there has been increasing attention paid to the role of these cells in tumor formation and progression. They may be a factor in initiating the first steps of carcinogenesis such as with liver cirrhosis and hepatocellular carcinoma and also contribute to continued tumor growth, invasion, metastasis, evasion of the immune system, and resistance to chemotherapy, in cancers of both the liver and pancreas. In this chapter we aim to review the structure and function of hepatic and pancreatic stellate cells and their contributions to the tumor microenvironment in their respective cancers and also discuss potential new targets for cancer therapy based on our new understanding of these vital components of the tumor stroma.

Ibrutinib Resistance Mechanisms and Treatment Strategies for B-Cell lymphomas

Chronic activation of B-cell receptor (BCR) signaling via Bruton tyrosine kinase (BTK) is largely considered to be one of the primary mechanisms driving disease progression in B-Cell lymphomas. Although the BTK-targeting agent ibrutinib has shown promising clinical responses, the presence of primary or acquired resistance is common and often leads to dismal clinical outcomes. Resistance to ibrutinib therapy can be mediated through genetic mutations, up-regulation of alternative survival pathways, or other unknown factors that are not targeted by ibrutinib therapy. Understanding the key determinants, including tumor heterogeneity and rewiring of the molecular networks during disease progression and therapy, will assist exploration of alternative therapeutic strategies. Towards the goal of overcoming ibrutinib resistance, multiple alternative therapeutic agents, including second- and third-generation BTK inhibitors and immunomodulatory drugs, have been discovered and tested in both pre-clinical and clinical settings. Although these agents have shown high response rates alone or in combination with ibrutinib in ibrutinib-treated relapsed/refractory(R/R) lymphoma patients, overall clinical outcomes have not been satisfactory due to drug-associated toxicities and incomplete remission. In this review, we discuss the mechanisms of ibrutinib resistance development in B-cell lymphoma including complexities associated with genomic alterations, non-genetic acquired resistance, cancer stem cells, and the tumor microenvironment. Furthermore, we focus our discussion on more comprehensive views of recent developments in therapeutic strategies to overcome ibrutinib resistance, including novel BTK inhibitors, clinical therapeutic agents, proteolysis-targeting chimeras and immunotherapy regimens.

Neural stem cell niche heterogeneity

In mammals, new neurons can be generated from neural stem cells in specific regions of the adult brain. Neural stem cells are characterized by their abilities to differentiate into all neural lineages and to self-renew. The specific microenvironments regulating neural stem cells, commonly referred to as neurogenic niches, comprise multiple cell populations whose precise contributions are under active current exploration. Understanding the cross-talk between neural stem cells and their niche components is essential for the development of therapies against neurological disorders in which neural stem cells function is altered. In this review, we describe and discuss recent studies that identified novel components in the neural stem cell niche. These discoveries bring new concepts to the field. Here, we evaluate these recent advances that change our understanding of the neural stem cell niche heterogeneity and its influence on neural stem cell function.

Staphylococcus epidermidis role in the skin microenvironment

Wound healing is a complex dynamic physiological process in response to cutaneous destructive stimuli that aims to restore the cutaneous' barrier role. Deciphering the underlying mechanistic details that contribute to wound healing will create novel therapeutic strategies for skin repair. Recently, by using state-of-the-art technologies, it was revealed that the cutaneous microbiota interact with skin immune cells. Strikingly, commensal Staphylococcus epidermidis-induced CD8+ T cells induce re-epithelization of the skin after injury, accelerating wound closure. From a drug development perspective, the microbiota may provide new therapeutic candidate molecules to accelerate skin healing. Here, we summarize and evaluate recent advances in the understanding of the microbiota in the skin microenvironment.

Pericyte Plasticity in the Brain

Cerebral pericytes are perivascular cells that stabilize blood vessels. Little is known about the plasticity of pericytes in the adult brain in vivo. Recently, using state-of-the-art technologies, including two-photon microscopy in combination with sophisticated Cre/loxP in vivo tracing techniques, a novel role of pericytes was revealed in vascular remodeling in the adult brain. Strikingly, after pericyte ablation, neighboring pericytes expand their processes and prevent vascular dilatation. This new knowledge provides insights into pericyte plasticity in the adult brain.

Cross-talk between lung cancer and bones results in neutrophils that promote tumor progression

Lung cancer is the leading cause of cancer mortality around the world. The lack of detailed understanding of the cellular and molecular mechanisms participating in the lung tumor progression restrains the development of efficient treatments. Recently, by using state-of-the-art technologies, including in vivo sophisticated Cre/loxP technologies in combination with lung tumor models, it was revealed that osteoblasts activate neutrophils that promote tumor growth in the lung. Strikingly, genetic ablation of osteoblasts abolished lung tumor progression via interruption of SiglecF^high-expressing neutrophils supply to the tumor microenvironment. Interestingly, SiglecF^high neutrophil signature was associated with worse lung adenocarcinoma patients outcome. This study identifies novel cellular targets for lung cancer treatment. Here, we summarize and evaluate recent advances in our understanding of lung tumor microenvironment.

Role of Schwann cells in cutaneous wound healing

Dermal wound healing is the process of repairing and remodeling skin following injury. Delayed or aberrant cutaneous healing poses a challenge for the health care system. The lack of detailed understanding of cellular and molecular mechanisms involved in this process hampers the development of effective targeted treatments. In a recent study, Parfejevs et al.-using state-of-the-art technologies, including in vivo sophisticated Cre/loxP techniques in combination with a mouse model of excisional cutaneous wounding-reveal that Schwann cells induce adult dermal wound healing. Strikingly, genetic ablation of Schwann cells delays wound contraction and closure, decreases myofibroblast formation, and impairs skin re-epithelization after injury. From a drug development perspective, Schwann cells are a new cellular candidate to be activated to accelerate skin healing. Here, we summarize and evaluate recent advances in the understanding of Schwann cells roles in the skin microenvironment.

Promyelocytic leukemia protein in mesenchymal stem cells is essential for leukemia progression

The dynamic interactions between leukemic cells and cells resident within the bone marrow microenvironment are vital for leukemia progression. The lack of detailed knowledge about the cellular and molecular mechanisms involved in this cross-talk restricts the design of effective treatments. Guarnerio et al. (2018) by using state-of-the-art techniques, including sophisticated Cre/loxP technologies in combination with leukemia mouse models, reveal that mesenchymal stem cells via promyelocytic leukemia protein (Pml) maintain leukemic cells in the bone marrow niche. Strikingly, genetic deletion of Pml in mesenchymal stem cells raised survival of leukemic mice under chemotherapeutic treatment. The emerging knowledge from this research provides a novel target in the bone marrow niche for therapeutic benefit in leukemia.