The role of cytokines and chemokines in the microenvironment of the blood-brain barrier in leukemia central nervous system metastasis

Chemobrain in blood cancers: How chemotherapeutics interfere with the brain's structure and functionality, immune system, and metabolic functions

Cancer treatment brings about a phenomenon not fully clarified yet, termed chemobrain. Its strong negative impact on patients' well-being makes it a trending topic in current research, interconnecting many disciplines from clinical oncology to neuroscience. Clinical and animal studies have often reported elevated concentrations of proinflammatory cytokines in various types of blood cancers. This inflammatory burst could be the background for chemotherapy-induced cognitive deficit in patients with blood cancers. Cancer environment is a dynamic interacting system. The review puts into close relationship the inflammatory dysbalance and oxidative/nitrosative stress with disruption of the blood-brain barrier (BBB). The BBB breakdown leads to neuroinflammation, followed by neurotoxicity and neurodegeneration. High levels of intracellular reactive oxygen species (ROS) induce the progression of cancer resulting in increased mutagenesis, conversion of protooncogenes to oncogenes, and inactivation of tumor suppression genes to trigger cancer cell growth. These cell alterations may change brain functionality, as well as morphology. Multidrug chemotherapy is not without consequences to healthy tissue and could even be toxic. Specific treatment impacts brain function and morphology, functions of the immune system, and metabolism in a unique mixture. In general, a chemo-drug's effects on cognition in cancer are not direct and/or in-direct, usually a combination of effects is more probable. Last but not least, chemotherapy strongly impacts the immune system and could contribute to BBB disruption. This review points out inflammation as a possible mechanism of brain damage during blood cancers and discusses chemotherapy-induced cognitive impairment.

Resveratrol alleviated neuroinflammation induced by pseudorabies virus infection through regulating microglial M1/M2 polarization

BACKGROUND

Pseudorabies virus (PRV) infections in susceptible non-porcine species trigger uncontrolled inflammations and eventually fatal encephalitis. Resveratrol (Res) has broad pharmacological functions including anti-virus, anti-inflammation, and neuroprotective.

PURPOSE

We attempted to investigate the potential of Res in ameliorating PRV infection pathology in mice and decipher the mechanism of Res in treating PRV.

METHODS

The mice were infected by PRV to investigate the protective effect of Res. Blood-brain barrier (BBB) permeability, H&E/Nissl/TUNEL staining, Real-time PCR and ELISA analyses were performed. Primary microglia and neuron were isolated from mice and cultured. The co-culture model of microglia and neuron was established by transwell. Immunofluorescence assay and flow cytometry were used.

RESULTS

In this study, we showed that Res ameliorated brain damage by reducing BBB permeability in PRV-infected mice, and diminished the expressions of MMP-2, MMP-9 and ZO-1 in the cortex. Pathological changes of neurons by H&E/Nissl/TUNEL staining suggested that Res could alleviate neuronal lesions. Moreover, Res inhibited the expressions of pro-inflammatory factors (IL-6, TNF-α) and chemokines (CCL3, CXCL10, MCP-1), but increased the expressions of anti-inflammatory factors (IL-4, IL-10) and neurotrophic factor (TGF-β, NGF and GDNF) in brain. In vitro cultured microglia cells, Res could suppress M1 microglia polarization and activate M2 microglia polarization. Co-culture of PRV-infected microglia with neuron cells by transwell system indicated that Res alleviated inflammatory response and neuronal apoptosis.

CONCLUSION

This study provided evidence that Res could protect mice from PRV-induced encephalitis through regulation of microglia polarization and neuronal apoptosis suggesting the potential for treatment of viral encephalitis.

Cerebrospinal fluid interleukin-6 is a potential diagnostic biomarker for central nervous system involvement in adult acute myeloid leukemia

Objective

We evaluated the correlation between cerebrospinal fluid (CSF) cytokine levels and central nervous system (CNS) involvement in adult acute myeloid leukemia (AML).

Methods

The study sample consisted of 90 patients diagnosed with AML and 20 with unrelated CNS involvement. The AML group was divided into two sub-groups: those with (CNS+, n=30) and without CNS involvement (CNS-, n=60). We used a cytometric bead assay to measure CSF interleukin (IL)-2, IL-4, IL-6, and IL-10, tumor necrosis factor-α, interferon-γ, and IL-17A. We used receiver operating characteristic curves to evaluate the ability of CSF cytokine levels to identify CNS involvement in adult AML.

Results

CSF IL-6 levels were significantly higher in CNS+adult AML patients and positively correlated with the lactate dehydrogenase levels (r=0.738, p<0.001) and white blood cell (WBC) count (r=0.455, p=0.012) in the blood, and the protein (r=0.686, p<0.001) as well as WBC count in the CSF (r=0.427, p=0.019). Using a CSF IL-6 cut-off value of 8.27 pg/ml yielded a diagnostic sensitivity and specificity was 80.00% and 88.46%, respectively (AUC, 0.8923; 95% CI, 0.8168–0.9678). After treating a subset of tested patients, their CSF IL-6 levels decreased. Consequently, the elevated CSF IL-6 levels remaining in CNS+ adult AML patients post-treatment were associated with disease progression.

Conclusion

CSF IL-6 is a promising marker for the diagnosis of adult AML with CNS involvement and a crucial dynamic indicator for therapeutic response.

Loss of IRF7 accelerates acute myeloid leukemia progression and induces VCAM1-VLA-4 mediated intracerebral invasion

Interferon regulatory factor 7 (IRF7) is widely studied in inflammatory models. Its effects on malignant progression have been documented mainly from the perspective of the microenvironment. However, its role in leukemia has not been established. Here we used MLL-AF9-induced acute myeloid leukemia (AML) mouse models with IRF7 knockout or overexpression and xenograft mouse models to explore the intrinsic effects of IRF7 in AML. AML-IRF7^−/− mice exhibited accelerated disease progression with intracerebral invasion of AML cells. AML-IRF7^−/− cells showed increased proliferation and elevated leukemia stem cell (LSC) levels. Overexpression of IRF7 in AML cells decreased cell proliferation and LSC levels. Furthermore, overexpression of transforming growth-interacting factor 1 (TGIF1) rescued the enhanced proliferation and high LSC levels caused by IRF7 deficiency. Moreover, upregulation of vascular cell adhesion molecule 1 (VCAM1), which correlated with high LSC levels, was detected in AML-IRF7^−/− cells. In addition, blocking VCAM1-very late antigen 4 (VLA-4) axis delayed disease progression and attenuated intracerebral invasion of AML cells. Therefore, our findings uncover the intrinsic effects of IRF7 in AML and provide a potential strategy to control central nervous system myeloid leukemia.

Central Nervous System Involvement in Adults with Acute Leukemia: Diagnosis, Prevention, and Management

PURPOSE OF REVIEW

Recent treatment advances in both acute myeloid leukemia and acute lymphoblastic leukemia have drastically improved outcomes for these diseases, but central nervous system (CNS) relapses still occur. Treatment of CNS disease can be challenging due to the impermeability of the blood-brain barrier to many systemic therapies.

RECENT FINDINGS

The diagnosis of CNS leukemia relies on assessment of clinical symptoms, cerebrospinal fluid sampling for conventional cytology and/or flow cytometry, and neuroimaging. While treatment of CNS leukemia with systemic or intrathecal chemotherapy and/or radiation can be curative in some patients, these modalities can also lead to serious toxicities. In the modern era, prophylaxis with intrathecal chemotherapy is the most important strategy to prevent CNS relapses in high risk patients. Accurate risk stratification tools and the use of risk-adapted prophylactic therapy are imperative to improving the outcomes of patients with acute leukemias and preventing the development of CNS leukemia.

Metabolic Reprogramming and Cell Adhesion in Acute Leukemia Adaptation to the CNS Niche

Involvement of the Central Nervous System (CNS) in acute leukemia confers poor prognosis and lower overall survival. Existing CNS-directed therapies are associated with a significant risk of short- or long-term toxicities. Leukemic cells can metabolically adapt and survive in the microenvironment of the CNS. The supporting role of the CNS microenvironment in leukemia progression and dissemination has not received sufficient attention. Understanding the mechanism by which leukemic cells survive in the nutrient-poor and oxygen-deprived CNS microenvironment will lead to the development of more specific and less toxic therapies. Here, we review the current literature regarding the roles of metabolic reprogramming in leukemic cell adhesion and survival in the CNS.

Salting the Soil: Targeting the Microenvironment of Brain Metastases

Paget's "seed and soil" hypothesis of metastatic spread has acted as a foundation of the field for over a century, with continued evolution as mechanisms of the process have been elucidated. The central nervous system (CNS) presents a unique soil through this lens, relatively isolated from peripheral circulation and immune surveillance with distinct cellular and structural composition. Research in primary and metastatic brain tumors has demonstrated that this tumor microenvironment (TME) plays an essential role in the growth of CNS tumors. In each case, the cancerous cells develop complex and bidirectional relationships that reorganize the local TME and reprogram the CNS cells, including endothelial cells, pericytes, astrocytes, microglia, infiltrating monocytes, and lymphocytes. These interactions create a structurally and immunologically permissive TME with malignant processes promoting positive feedback loops and systemic consequences. Strategies to interrupt interactions with the native CNS components, on "salting the soil," to create an inhospitable environment are promising in the preclinical setting. This review aims to examine the general and specific pathways thus far investigated in brain metastases and related work in glioma to identify targetable mechanisms that may have general application across the spectrum of intracranial tumors.

Evaluation of diagnostic and predictive values of the serum VEGF-A level and systemic immune-inflammation index in small cell lung cancer

Purpose: To evaluate diagnostic and predictive values of the serum vascular endothelial growth factor-A (VEGF-A) level and systemic immune-inflammation index (SII) in small cell lung cancer (SCLC) patients.

Methods: From January 2018 to April 2020, we prospectively enrolled 59 untreated SCLC patients in the study group and 50 non-neoplastic patients in the control group. Blood samples were collected at baseline, after the first two cycles of chemotherapy and at progression in the study group and at entry in the control group. Serum VEGF-A was measured by chemiluminescence, SII was calculated based on complete blood count results, and the relationship between the VEGF-A/SII and clinicopathological characteristics, chemotherapeutic efficacy and progression-free survival (PFS) of SCLC patients was analyzed.

Results: Baseline serum VEGF-A was significantly higher in SCLC patients than in non-neoplastic patients (P<0.001), while baseline SII was not (P=0.114). There was no correlation between baseline VEGF-A and SII in SCLC patients (P=0.123); however, there was a significant correlation between baseline VEGF-A and disease stage and central nervous system (CNS) metastasis (P=0.021 and P=0.012, respectively), as well as between baseline SII and disease stage and liver metastasis (P=0.026 and P=0.018, respectively). Serum VEGF-A was significantly lower than the pretreatment level after 2 cycles of treatment (P=0.049) but was not different at progression (P=0.247). Baseline VEGF-A was correlated with the treatment response of first-line chemotherapy (P=0.001), while baseline SII was not (P=0.392). Kaplan-Meier survival analysis suggested that the PFS of first-line chemotherapy was significantly longer in the low-VEGF-A group at baseline than the high-VEGF-A group (11.37 vs. 6.17 months, P<0.001). There was a trend toward longer PFS of first-line chemotherapy in the low-SII group at baseline than the high-SII group, but the difference was not significant (12.10 vs. 9.10 months, P>0.050). Univariate and multivariate Cox regression analyses suggested that baseline VEGF-A (HR: 3.443, 95% CI: 1.330-8.908, P=0.011) was an independent prognostic factor for PFS in SCLC patients.

Conclusions: Baseline serum VEGF-A and SII are associated with important clinicopathological characteristics of SCLC patients. VEGF-A, but not SII, has the ability of diagnosis and predicting first-line chemotherapeutic efficacy and prognosis in SCLC patients.

The Impact of Small Extracellular Vesicles on Lymphoblast Trafficking across the Blood-Cerebrospinal Fluid Barrier In Vitro

Central nervous System (CNS) disease in pediatric acute lymphoblastic leukemia (ALL) is a major concern, but still, cellular mechanisms of CNS infiltration are elusive. The choroid plexus (CP) is a potential entry site, and, to some extent, invasion resembles CNS homing of lymphocytes during healthy state. Given exosomes may precondition target tissue, the present work aims to investigate if leukemia-derived exosomes contribute to a permissive phenotype of the blood-cerebrospinal fluid barrier (BCSFB). Leukemia-derived exosomes were isolated by ultracentrifugation from the cell lines SD-1, Nalm-6, and P12-Ichikawa (P12). Adhesion and uptake to CP epithelial cells and the significance on subsequent ALL transmigration across the barrier was studied in a human BCSFB in vitro model based on the HiBCPP cell line. The various cell lines markedly differed regarding exosome uptake to HiBCPP and biological significance. SD-1-derived exosomes associated to target cells unspecifically without detectable cellular effects. Whereas Nalm-6 and P12-derived exosomes incorporated by dynamin-dependent endocytosis, uptake in the latter could be diminished by integrin blocking. In addition, only P12-derived exosomes led to facilitated transmigration of the parental leukemia cells. In conclusion, we provide evidence that, to a varying extent, leukemia-derived exosomes may facilitate CNS invasion of ALL across the BCSFB without destruction of the barrier integrity.

Revealing the molecular mechanism of central nervous system leukemia with single-cell technology

Central nervous system leukemia (CNSL) is a severe complication of acute leukemia, with serious consequences for life quality and expectancy. The molecular mechanism of CNSL is unclear at present. Thus, determining appropriate prevention and therapeutic strategies for CNSL remain challenging. Currently, inferences regarding gene functions are based on the measurement of average gene expression in a bulk lysate. However, leukemia cells are a heterogeneous population in which the expression of critical genes may be masked by many unrelated genes. Single-cell sequencing may therefore be the best way to explore the development of CNSL in the bone marrow and peripheral blood at diagnosis and subsequent time points, in order to detect potential targets and prevent the development of CNSL. In this review, we first discuss the possible mechanism of CNSL, then describe the heterogeneity of leukemia cells. Finally, we focus on the role of single-cell technology in preventing and treating CNSL.

New attempts for central nervous infiltration of pediatric acute lymphoblastic leukemia

The cure rate of acute lymphoblastic leukemia (ALL), the commonest childhood cancer, has been sharply improved and reached almost 90% ever since the central nervous system (CNS)-directed therapy proposed in the 1960s. However, relapse, particularly in the central nervous system (CNS), is still a common cause of treatment failure. Up to now, the classic CNS-directed treatment for CNS leukemia (CNSL) has been aslant from cranial radiation to high-dose system chemotherapy plus intrathecal (IT) chemotherapy for the serious side effects of cranial radiation. The neurotoxic effects of chemotherapy and IT chemotherapy have been reported in recent years as well. For better prevention and treatment of CNSL, plenty of studies have tried to improve the detection sensitivity for CNSL and prevent CNSL from happening by targeting cytokines and chemokines which could be key factors for the traveling of ALL cells into the CNS. Other studies also have aimed to completely kill ALL cells (including dormant cells) in the CNS by promoting the entering of chemotherapy drugs into the CNS or targeting the components of the CNS niche which could be in favor of the survival of ALL cells in CNS. The aim of this review is to discuss the imperfection of current diagnostic methods and treatments for CNSL, as well as new attempts which could be significant for better elimination of CNSL.

The Potential Role of Dysfunctions in Neuron-Microglia Communication in the Pathogenesis of Brain Disorders

The bidirectional communication between neurons and microglia is fundamental for the proper functioning of the central nervous system (CNS). Chemokines and clusters of differentiation (CD) along with their receptors represent ligand-receptor signalling that is uniquely important for neuron - microglia communication. Among these molecules, CX3CL1 (fractalkine) and CD200 (OX-2 membrane glycoprotein) come to the fore because of their cell-type-specific localization. They are principally expressed by neurons when their receptors, CX3CR1 and CD200R, respectively, are predominantly present on the microglia, resulting in the specific axis which maintains the CNS homeostasis. Disruptions to this balance are suggested as contributors or even the basis for many neurological diseases. In this review, we discuss the roles of CX3CL1, CD200 and their receptors in both physiological and pathological processes within the CNS. We want to underline the critical involvement of these molecules in controlling neuron - microglia communication, noting that dysfunctions in their interactions constitute a key factor in severe neurological diseases, such as schizophrenia, depression and neurodegeneration-based conditions.

Evaluation of multiplexed biomarkers in assessment of CSF infiltration in pediatric acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a very common pediatric malignancy with high survival rates. The course of treatment is modified according to the occurrence of central nervous system (CNS) disease. Aim: To relate serum and cerebrospinal fluid levels of five biomarkers (matrix metalloprotienase 9, CCL-2, sVCAM-1, IFN-γ and inducible protein 10) at diagnosis to the development of CNS infiltration. Methods: The present study was carried on 64 children with ALL and 20 controls. Multiplexed cytokines were measured by Luminex technology (Matrix metalloprotienase 9, CCL-2, sVCAM-1, IFN-γ and inducible protein 10). Results: Significantly higher sMMP-9 and lower sCCL2 were found in patients who developed CNS leukemia. Conclusion: Serum multiplexed parameters at diagnosis of childhood ALL may predict of development of CNS leukemia.

Effects of VEGFR1+ hematopoietic progenitor cells on pre-metastatic niche formation and in vivo metastasis of breast cancer cells

The pre-metastatic niche has been shown to play a critical role in tumor metastasis, and its formation is closely related to the tumor microenvironment. However, the underlying molecular mechanisms remain unclear. In the present study, we successfully established a mouse model of lung metastasis using luciferase-expressing MDA-MB-435s cells. In this model, recruitment of vascular endothelial growth factor receptor-1 (VEGFR1)⁺CD133⁺ hematopoietic progenitor cells (HPCs) was gradually increased in lung but gradually decreased after the formation of tumor colonies in lung. We also established a highly metastatic MDA-MB-435s (MDA-MB-435s-HM) cell line from the mouse model. Changes in protein profiles in different culture conditions were investigated by protein microarray analysis. The levels of CXC chemokine ligand 16, interleukin (IL)-2Rα, IL-2Rγ, matrix metalloproteinase (MMP)-1, MMP-9, platelet-derived growth factor receptor (PDGFR)-α, stromal cell-derived factor (SDF)-1α, transforming growth factor (TGF)-β, platelet endothelial cell adhesion molecule (PECAM)-1 and vascular endothelial (VE)-cadherin were significantly greater (> fivefold) in the culture medium from MDA-MB-435s-HM cells than in that from MDA-MB-435s cells. Moreover, the levels of MMP-9, PDGFR-α, and PECAM-1 were significantly greater in the co-culture medium of MDA-MB-435s-HM cells and CD133⁺ HPCs than in that from MDA-MB-435s-HM cells. Differentially expressed proteins were validated by enzyme-linked immunosorbent assay, and expression of their transcripts was confirmed by quantitative real-time polymerase chain reaction. Moreover, inhibition of MMP-9, PDGFR-α, and PECAM-1 by their specific inhibitors or antibodies significantly decreased cell migration, delayed lung metastasis, and decreased recruitment of VEGFR1⁺CD133⁺ HPCs into lung. Intra-hepatic growth of HPCs enhanced the invasive growth of MDA-MB-435s-HM cells in the liver. Our data indicate that VEGFR1⁺CD133⁺ HPCs contribute to lung metastasis.

Effect of tryptase on mouse brain microvascular endothelial cells via protease-activated receptor 2

Background

Mast cells (MCs), the ‘first responders’ in brain injury, are able to disrupt the blood–brain barrier (BBB), but the underlying mechanism is not well understood. Tryptase is the most abundant MC secretory product. Protease-activated receptor 2 (PAR-2) has been identified as a specific receptor for tryptase, which is abundantly expressed in brain microvascular endothelial cells. The BBB comprises brain microvascular endothelial cells that display specialised molecular properties essential for BBB function and integrity. Therefore, the purpose of the present study was to investigate the effects of tryptase on mouse brain microvascular endothelial cell line bEnd3 and its potential mechanisms of action.

Methods

Induction of mouse brain microvascular endothelial cell activation by tryptase was examined. Then, mouse brain microvascular endothelial cells were pretreated with a PAR-2 antagonist and stimulated with tryptase. Cellular activation, proinflammatory cytokine production, expression of PAR-2, Toll-like receptors (TLRs) and mitogen-activated protein kinases (MAPK), nuclear factor kappa B (NF-kappa B) phosphorylation were assessed.

Results

Tryptase upregulated the production of VCAM-1, MMPs (MMP9 and MMP2), TLR4 and TNF-α and downregulated the expression of the tight junction proteins occludin and claudin-5 in mouse brain microvascular endothelial cell. Among the MAPK and NF-kappa B pathway, ERK and NF-kappa B were activated by tryptase. All of these effects could be eliminated by the PAR-2 inhibitor.

Conclusion

Based on our findings, we conclude that tryptase can trigger brain microvascular endothelial cell activation and proinflammatory mediator release. These findings may further clarify the involvement and mechanism of tryptase in BBB disruption.

A New Method for Recognizing Cytokines Based on Feature Combination and a Support Vector Machine Classifier

Research on cytokine recognition is of great significance in the medical field due to the fact cytokines benefit the diagnosis and treatment of diseases, but the current methods for cytokine recognition have many shortcomings, such as low sensitivity and low F-score. Therefore, this paper proposes a new method on the basis of feature combination. The features are extracted from compositions of amino acids, physicochemical properties, secondary structures, and evolutionary information. The classifier used in this paper is SVM. Experiments show that our method is better than other methods in terms of accuracy, sensitivity, specificity, F-score and Matthew's correlation coefficient.

Pediatric acute lymphoblastic leukemia-Conquering the CNS across the choroid plexus

Despite the high prevalence of central nervous system (CNS) involvement in relapsing pediatric acute lymphoblastic leukemia (ALL), our understanding of CNS invasion is still vague. As lymphoblasts have to overcome the physiological blood-CNS barriers to enter the CNS, we investigated the cellular interactions of lymphoblasts with the choroid plexus (CP) epithelium of the blood-cerebrospinal fluid barrier (BCSFB). Both a precurser B cell ALL (pB-ALL) cell line (SD-1) and a T cell ALL (T-ALL) cell line (P12-Ishikawa) were able to actively cross the CP epithelium in a human in vitro model. We could illustrate a transcellular and (supposedly) paracellular transmigration by 3-dimensional immunofluorescence microscopy as well as electron microscopy. Chemotactic stimulation with CXCL12 during this process led to a significantly increased transmigration and blocking CXCL12/CXCR4-signaling by the CXCR4-inhibitor AMD3100 inhibited this effect. However, CXCR4 expression in primary ALL samples did not correlate to CNS disease, indicating that CXCR4-driven CNS invasion across the BCSFB might be a general property of pediatric ALL. Notably, we present a unique in vitro BCSFB model suitable to study CNS invasion of lymphoblasts in a human setting, providing the opportunity to investigate experimental variables, which may determine CNS disease childhood ALL.