Reactive astrocytes foster brain metastases via STAT3 signaling

Epigenetic alterations fuel brain metastasis via regulating inflammatory cascade

Brain metastasis (BrM) is a major threat to the survival of melanoma, breast, and lung cancer patients. Circulating tumor cells (CTCs) cross the blood-brain barrier (BBB) and sustain in the brain microenvironment. Genetic mutations and epigenetic modifications have been found to be critical in controlling key aspects of cancer metastasis. Metastasizing cells confront inflammation and gradually adapt in the unique brain microenvironment. Currently, it is one of the major areas that has gained momentum. Researchers are interested in the factors that modulate neuroinflammation during BrM. We review here various epigenetic factors and mechanisms modulating neuroinflammation and how this helps CTCs to adapt and survive in the brain microenvironment. Since epigenetic changes could be modulated by targeting enzymes such as histone/DNA methyltransferase, deacetylases, acetyltransferases, and demethylases, we also summarize our current understanding of potential drugs targeting various aspects of epigenetic regulation in BrM.

Cell-cell communication characteristics in breast cancer metastasis

Breast cancer, a highly fatal disease due to its tendency to metastasize, is the most prevalent form of malignant tumors among women worldwide. Numerous studies indicate that breast cancer exhibits a unique predilection for metastasis to specific organs including the bone, liver, lung, and brain. However, different types of, The understanding of the heterogeneity of metastatic breast cancer has notably improved with the recent advances in high-throughput sequencing techniques. Focusing on the modification in the microenvironment of the metastatic organs and the crosstalk between tumor cells and in situ cells, noteworthy research points include the identification of two distinct modes of tumor growth in bone metastases, the influence of type II pneumocyte on lung metastases, the paradoxical role of Kupffer cells in liver metastases, and the breakthrough of the blood-brain barrier (BBB) breach in brain metastases. Overall, this review provides a comprehensive overview of the characteristics of breast cancer metastases, shedding light on the pivotal roles of immune and resident cells in the development of distinct metastatic foci.

Roles of protein tyrosine phosphatases in hepatocellular carcinoma progression (Review)

Hepatocellular carcinoma (HCC) represents almost 80% of all liver cancers, is the sixth most common cancer and is the second‑highest cause of cancer‑related deaths worldwide. Protein tyrosine phosphatases (PTPs), which are encoded by the largest family of phosphatase genes, play critical roles in cellular responses and are implicated in various signaling pathways. Moreover, PTPs are dysregulated and involved in various cellular processes in numerous cancers, including HCC. Kinases and phosphatases are coordinators that modulate cell activities and regulate signaling responses. There are multiple interacting signaling networks, and coordination of these signaling networks in response to a stimulus determines the physiological outcome. Numerous issues, such as drug resistance and inflammatory reactions in the tumor microenvironment, are implicated in cancer progression, and the role of PTPs in these processes has not been well elucidated. Therefore, the present review focused on discussing the relationship of PTPs with inflammatory cytokines and chemotherapy/targeted drug resistance, providing detailed information on how PTPs can modulate inflammatory reactions and drug resistance to influence progression in HCC.

Feed-forward loops between metastatic cancer cells and their microenvironment-the stage of escalation

Breast cancer is the most frequent cancer among women, and metastases in distant organs are the leading cause of the cancer-related deaths. While survival of early-stage breast cancer patients has increased dramatically, the 5-year survival rate of metastatic patients has barely improved in the last 20 years. Metastases can arise up to decades after primary tumor resection, hinting at microenvironmental factors influencing the sudden outgrowth of disseminated tumor cells (DTCs). This review summarizes how the environment of the most common metastatic sites (lung, liver, bone, brain) is influenced by the primary tumor and by the varying dormancy of DTCs, with a special focus on how established metastases persist and grow in distant organs due to feed-forward loops (FFLs). We discuss in detail the importance of FFL of cancer cells with their microenvironment including the secretome, interaction with specialized tissue-specific cells, nutrients/metabolites, and that novel therapies should target not only the cancer cells but also the tumor microenvironment, which are thick as thieves.

Efficacy of a Three Drug-Based Therapy for Neuroblastoma in Mice

High-risk neuroblastoma (HR-NB) still remains the most dangerous tumor in early childhood. For this reason, the identification of new therapeutic approaches is of fundamental importance. Recently, we combined the conventional pharmacological approach to NB, represented by cisplatin, with fendiline hydrochloride, an inhibitor of several transporters involved in multidrug resistance of cancer cells, which demonstrated an enhancement of the ability of cisplatin to induce apoptosis. In this work, we co-administrated acetazolamide, a carbonic anhydrase isoform IX (CAIX) inhibitor which was reported to increase chemotherapy efficacy in various cancer types, to the cisplatin/fendiline approach in SKNBE2 xenografts in NOD-SCID mice with the aim of identifying a novel and more effective treatment. We observed that the combination of the three drugs increases more than twelvefold the differences in the cytotoxic activity of cisplatin alone, leading to a remarkable decrease of the expression of malignancy markers. Our conclusion is that this approach, based on three FDA-approved drugs, may constitute an appropriate improvement of the pharmacological approach to HR-NB.

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.

JAK/STAT signaling pathway-mediated microRNA-181b promoted blood-brain barrier impairment by targeting sphingosine-1-phosphate receptor 1 in septic rats

Background

Blood-brain barrier (BBB) impairment plays a significant role in the pathogenesis of sepsis-associated encephalopathy (SAE). However, the molecular mechanisms are poorly understood. In the present study, we aimed to investigate the regulatory relationship between the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway, microRNA (miR)-181b and its target genes in sepsis in vivo and in vitro.

Methods

Four rat models (sham, sepsis, sepsis plus STAT3 inhibitor (Stattic), and sepsis plus miR-181b inhibitor [sepsis + anta-miR-181b]) were established. For the in vitro experiments, rat brain microvascular endothelial cells (rBMECs) and rat brain astrocytes (rAstrocytes) were cultured with 10% serum harvested from sham, sepsis, and sepsis + anta-miR-181b rats. Chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-QPCR) analysis was carried out to detect the binding and enrichment of the JAK/STAT3 signal core transcription complex in the miR-181b promoter region. Dual-luciferase reporter gene assay was conducted to test miR-181b and its target genes. The cell adhesion rate of rBMECs was also measured.

Results

During our investigations, the expression levels of miR-181b, p-JAK2, p-STAT3, and C/EBPβ were found to be significantly increased in the septic rats compared with the sham rats. STAT3 inhibitor halted BBB damage by downregulating the expression of miR-181b. In addition, miR-181b targeted sphingosine-1-phosphate receptor 1 (S1PR1) and neurocalcin delta (NCALD). The up-regulated miR-181b significantly decreased the cell adhesion rate of rBMECs. The administration of miR-181b inhibitor reduced damage to the BBB through increasing the expression of S1PR1 and NCALD, which again proved that miR-181b negatively regulates SIPR1 and NCALD to induce BBB damage.

Conclusions

Our study demonstrated that JAK2/STAT3 signaling pathway induced expression of miR-181b, which promoted BBB impairment in rats with sepsis by downregulating S1PR1 and decreasing BBB cell adhesion. These findings strongly suggest JAK2/STAT3/miR-181b axis as therapeutic target in protecting against sepsis-induced BBB damage.

Protein tyrosine phosphatase receptor type delta (PTPRD) suppresses the expression of PD-L1 in human hepatocellular carcinoma by down-regulating STAT3

BACKGROUND

Protein tyrosine phosphatase receptor type delta (PTPRD) is a tumor suppressor that is often inactivated in hepatocellular carcinoma (HCC). However, the mechanisms of how PTPRD inhibits HCC are not well understood. Programmed cell death ligand 1 (PD-L1), an immune checkpoint, plays a seminal role in the regulation of carcinogenesis of HCC. The sustained activation of STAT3 is closely related to PTPRD deletion and PD-L1 overexpression; however, whether there is a relationship between PTPRD and PD-L1 expression in HCC has not been investigated. This study aims to investigate the relationship between PTPRD and PD-L1 in HCC samples and illuminate potential new molecular mechanisms of PTPRD effects on PD-L1 in HepG2 cells.

METHODS

We collected 16 pairs of tumorous tissues and adjacent normal tissues from HCC patients. The mRNA and protein expression levels of PTPRD and PD-L1 in the HCC tissues were detected by RT-PCR and Western blot analysis. Next, Spearman's correlation analysis was performed to evaluate the relationship between PTPRD and PD-L1. Then, we transfected the overexpressed or knocked-down PTPRD genes into the HepG2 cell line, and the effects of PTPRD on PD-L1 in HCC cells were evaluated. The activity from the STAT3 and p-STAT3 in the HepG2 cells transfected with PTPRD gene overexpression and knockdown was determined by Western blotting tests.

RESULTS

The expression of PTPRD was significantly down-regulated in the HCC tissues compared with the adjacent control tissues; however, PD-L1 was significantly higher in the HCC tissues. There was a negative correlation between PTPRD and PD-L1 expression in the HCC tissues. PTPRD over-expression significantly inhibited PD-L1 expression; meanwhile, PTPRD depletion promoted PD-L1 expression in the HepG2 cells. Furthermore, PTPRD over-expression significantly inhibited the expression of STAT3 and p-STAT3, while PTPRD depletion promoted these cytokines. Our studies revealed that PTPRD repressed PD-L1 expression in the HepG2 cells, which might occur via the STAT3 pathway.

CONCLUSIONS

The results from our study show that PTPRD and PD-L1 are negatively correlated in HCC tissues. PTPRD suppresses PD-L1 expression in HepG2 cells by down-regulating STAT3. These findings are expected to become a new target for the immunotherapy of HCC.

Tumor Necrosis Factor-Like Weak Inducer of Apoptosis (TWEAK) Enhances Activation of STAT3/NLRC4 Inflammasome Signaling Axis through PKCδ in Astrocytes: Implications for Parkinson's Disease

Astrocytic dysfunction has been implicated in Parkinson's disease (PD) pathogenesis. While the Tumor necrosis factor-like weak inducer of apoptosis (TWEAK)/Fn14 signaling axis is known to play a role in PD-like neuropathology, the molecular mechanisms that govern this process remain poorly understood. Herein, we show that TWEAK levels are elevated in PD serum compared to controls. Moreover, using both U373 human astrocyte cells and primary mouse astrocytes, we demonstrate that TWEAK induces mitochondrial oxidative stress as well as protein kinase C delta (PKCδ) and signal transducer and activator of transcription 3 (STAT3) activation, accompanied by NLRC4 inflammasome activation and upregulation and release of proinflammatory cytokines, including IL-1β, TNF-α, and IL-18. Mechanistically, TWEAK-induced PKCδ activation enhances the STAT3/NLRC4 signaling pathway and other proinflammatory mediators through a mitochondrial oxidative stress-dependent mechanism. We further show that PKCδ knockdown and mito-apocynin, a mitochondrial antioxidant, suppress TWEAK-induced proinflammatory NLRC4/STAT3 signaling and cellular oxidative stress response. Notably, we validated our in vitro findings in an MPTP mouse model of PD and in mice receiving intrastriatal administration of TWEAK. These results indicate that TWEAK is a key regulator of astroglial reactivity and illustrate a novel mechanism by which mitochondrial oxidative stress may influence dopaminergic neuronal survival in PD.