A STAT3 of Addiction: Adipose Tissue, Adipocytokine Signalling and STAT3 as Mediators of Metabolic Remodelling in the Tumour Microenvironment

Selected miRNA and Psoriasis-Cardiovascular Disease (CVD)-Overweight/Obesity Network-A Pilot Study

Psoriasis is nowadays recognized as a multifactorial systemic disease with complex and not fully understood pathogenesis. In psoriatic patients, the increased cardiovascular disease (CVD) risk and frequent comorbidities like obesity are observed. The aim of this study was to investigate differences in miRNA (miR-22-3p, miR-133a-3p, miR-146a-5p, miR-369-3p, and Let-7b-5p) involved in CVD risk among psoriatic patients with overweight/obesity and with normal weight. The study comprised 28 male psoriatic patients and 16 male healthy controls. miRNA isolated from peripheral blood mononuclear cells was reverse-transcribed and RT-qPCR was performed. We have found decreased levels of miR-22, miR-133a, miR-146a, and miR-369 among the psoriatic patients. There was a statistically significant difference in miR-22 and miR-146a levels between psoriatic patients with overweight/obesity and with normal weight. There were positive correlations between miR-22 and miR-146a levels and psoriatic arthritis (PsA) in psoriatic patients with normal weight and between the miR-133a level and PsA in the overweight/obese patients. The decreased levels of selected miRNA are consistent with the levels observed in CVD indicating their impact on the CVD risk in psoriatic patients. miR-22 and miR-146 may be recognized as one of the contributing factors in the obesity-CVD-psoriasis network.

Suppression of Lipid Accumulation in the Differentiation of 3T3-L1 Preadipocytes and Human Adipose Stem Cells into Adipocytes by TAK-715, a Specific Inhibitor of p38 MAPK

Excessive preadipocyte differentiation is linked with obesity. Although previous studies have shown that p38 MAPK is associated with adipogenesis, the regulation of preadipocyte differentiation by TAK-715, an inhibitor of p38 mitogen-activated protein kinase (MAPK), remains unclear. Interestingly, TAK-715 at 10 μM vastly suppressed the accumulation of lipid and intracellular triglyceride (TG) content with no cytotoxicity during 3T3-L1 preadipocyte differentiation. On mechanistic levels, TAK-715 significantly decreased the expressions of the CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor gamma (PPAR-γ), fatty acid synthase (FAS), and perilipin A. Similarly, the phosphorylation of the signal transducer and activator of transcription-3 (STAT-3) in differentiating 3T3-L1 cells was also reduced with TAK-715 treatment. Moreover, TAK-715 significantly blocked the phosphorylation of activating transcription factor-2 (ATF-2), a p38 MAPK downstream molecule, during 3T3-L1 preadipocyte differentiation. Of importance, TAK-715 also markedly impeded the phosphorylation of p38 MAPK and suppressed lipid accumulation during the adipocyte differentiation of human adipose stem cells (hASCs). Concisely, this is the first report that TAK-715 (10 μM) has potent anti-adipogenic effects on the adipogenesis process of 3T3-L1 cells and hASCs through the regulation of the expression and phosphorylation of p38 MAPK, C/EBP-α, PPAR-γ, STAT-3, FAS, and perilipin A.

Role of STAT3 and NRF2 in Tumors: Potential Targets for Antitumor Therapy

Signal transducer and activator of transcription 3 (STAT3) and nuclear factor erythroid-derived 2-like 2 (NRF2, also known as NFE2L2), are two of the most complicated transcription regulators, which participate in a variety of physiological processes. Numerous studies have shown that they are overactivated in multiple types of tumors. Interestingly, STAT3 and NRF2 can also interact with each other to regulate tumor progression. Hence, these two important transcription factors are considered key targets for developing a new class of antitumor drugs. This review summarizes the pivotal roles of the two transcription regulators and their interactions in the tumor microenvironment to identify potential antitumor drug targets and, ultimately, improve patients' health and survival.

Obesity and Fatty Acids Promote Mitochondrial Translocation of STAT3 Through ROS-Dependent Mechanisms

Obesity promotes the onset and progression of metabolic and inflammatory diseases such as type 2 diabetes. The chronic low-grade inflammation that occurs during obesity triggers multiple signaling mechanisms that negatively affect organismal health. One such mechanism is the persistent activation and mitochondrial translocation of STAT3, which is implicated in inflammatory pathologies and many types of cancers. STAT3 in the mitochondria (mitoSTAT3) alters electron transport chain activity, thereby influencing nutrient metabolism and immune response. PBMCs and CD4+ T cells from obese but normal glucose-tolerant (NGT) middle-aged subjects had higher phosphorylation of STAT3 on residue serine 727 and more mitochondrial accumulation of STAT3 than cells from lean subjects. To evaluate if circulating lipid overabundance in obesity is responsible for age- and sex-matched mitoSTAT3, cells from lean subjects were challenged with physiologically relevant doses of the saturated and monounsaturated fatty acids, palmitate and oleate, respectively. Fatty acid treatment caused robust accumulation of mitoSTAT3 in all cell types, which was independent of palmitate-induced impairments in autophagy. Co-treatment of cells with fatty acid and trehalose prevented STAT3 phosphorylation and mitochondrial accumulation in an autophagy-independent but cellular peroxide-dependent mechanism. Pharmacological blockade of mitoSTAT3 either by a mitochondria-targeted STAT3 inhibitor or ROS scavenging prevented obesity and fatty acid-induced production of proinflammatory cytokines IL-17A and IL-6, thus establishing a mechanistic link between mitoSTAT3 and inflammatory cytokine production.

Silencing GOLGA8B inhibits cell invasion and metastasis by suppressing STAT3 signaling pathway in lung squamous cell carcinoma

Changes to some Golgi subfamily member proteins are reported to be involved in tumor metastasis. However, the functional role and potential mechanism of the Golgi A8 family member B (GOLGA8B) in lung squamous cell carcinoma (LUSC) remains unknown. In the present study, GOLGA8B expression was detected using qRT-PCR, Western blot, and immunohistochemistry (IHC). In vivo animal experiments and in vitro functional assays were performed to explore the function of GOLGA8B in LUSC. Luciferase assays were performed to investigate the underlying targets of GOLGA8B in LUSC. GOLGA8B was shown to be highly expressed in LUSC metastasis tissue, and significantly associated with the distant metastasis-free survival of LUSC patients. Loss-of-function assays indicated that silencing GOLGA8B suppressed LUSC cell tumorigenesis in vivo and weakened in vitro invasion and migration. GOLGA8B silencing-induced inhibition of invasion and migration was associated with the inactivation of STAT3 signaling. Importantly, these results showed that the number of circulating tumor cells (CTCs) was markedly higher in the GOLGA8B silencing group than in the control vector group. GOLGA8B expression was positively associated with p-STAT3 expression in LUSC tissue. Study findings revealed a novel mechanism by which GOLGA8B promotes tumor metastasis in LUSC cells and suggests that this protein could be a promising target for antitumor metastasis therapy in LUSC patients.

Retinal ganglion cell survival after severe optic nerve injury is modulated by crosstalk between Jak/Stat signaling and innate immune responses in the zebrafish retina

Visual information is transmitted from the eye to the brain along the optic nerve, a structure composed of retinal ganglion cell (RGC) axons. The optic nerve is highly vulnerable to damage in neurodegenerative diseases, such as glaucoma, and there are currently no FDA-approved drugs or therapies to protect RGCs from death. Zebrafish possess remarkable neuroprotective and regenerative abilities. Here, utilizing an optic nerve transection (ONT) injury and an RNA-seq-based approach, we identify genes and pathways active in RGCs that may modulate their survival. Through pharmacological perturbation, we demonstrate that Jak/Stat pathway activity is required for RGC survival after ONT. Furthermore, we show that immune responses directly contribute to RGC death after ONT; macrophages/microglia are recruited to the retina and blocking neuroinflammation or depleting these cells after ONT rescues survival of RGCs. Taken together, these data support a model in which crosstalk between macrophages/microglia and RGCs, mediated by Jak/Stat pathway activity, regulates RGC survival after optic nerve injury.

Scaffold compound L971 exhibits anti-inflammatory activities through inhibition of JAK/STAT and NFκB signalling pathways

JAK/STAT and NFκB signalling pathways play essential roles in regulating inflammatory responses, which are important pathogenic factors of various serious immune-related diseases, and function individually or synergistically. To find prodrugs that can treat inflammation, we performed a preliminary high-throughput screening of 18 840 small molecular compounds and identified scaffold compound L971 which significantly inhibited JAK/STAT and NFκB driven luciferase activities. L971 could inhibit the constitutive and stimuli-dependent activation of STAT1, STAT3 and IκBα and could significantly down-regulate the proinflammatory gene expression in mouse peritoneal macrophages stimulated by LPS. Gene expression profiles upon L971 treatment were determined using high-throughput RNA sequencing, and significant differentially up-regulated and down-regulated genes were identified by DESeq analysis. The bioinformatic studies confirmed the anti-inflammatory effects of L971. Finally, L971 anti-inflammatory character was further verified in LPS-induced sepsis shock mouse model in vivo. Taken together, these data indicated that L971 could down-regulate both JAK/STAT and NFκB signalling activities and has the potential to treat inflammatory diseases such as sepsis shock.

In vitro Non-Small Cell Lung Cancer Inhibitory Effect by New Diphenylethane Isolated From Stems and Leaves of Dioscorea oppositifolia L. via ERβ-STAT3 Pathway

Lung cancer is the most leading cause of cancer mortality throughout the world, of which about 85% cases comprise the non-small cell lung cancer (NSCLC). Estrogen and estrogen receptors are known to be involved in the pathogenesis and development of lung cancer. Dioscorea oppositifolia L. is a traditional Chinese medicine and a nutritious food, and can be an excellent candidate as an anti-cancer agent owing to its estrogen-like effects. However, the stems and leaves of D. oppositifolia L. are piled up in the field as a waste, causing environmental pollution and waste of resources. In the present study, a new diphenylethane (D1) was isolated from the stems and leaves of D. oppositifolia L. It was observed that D1 reduced the cell viability, migration, energy metabolism, and induced apoptosis in the A549 cells. Mechanistic studies showed that D1 reduced the STAT3 nuclear localization and downregulated the expression of the STAT3 target genes like Mcl-1, Bcl-xL and MMP-2 that are involved in the cell survival and mobility. Moreover, our results indicated that D1 exhibited estrogenic activities mediated by ERβ, and antagonising ERβ decreased the cytotoxic effect of D1 in A549 cells. In addition, inhibition of the nuclear translocation of STAT3 did not interfere with the binding of D1 and ERβ. However, after antagonizing ERβ, the nuclear translocation of STAT3 increased, thereby demonstrating that STAT3 was the downstream signaling molecule of ERβ. In conclusion, the D1 mediated anti-NSCLC in vitro effects or at least in part can be attributed to the ERβ-STAT3 signaling. Our findings suggest the role of D1 in treating NSCLC on a molecular level, and can help to improve the comprehensive utilization rate of D. oppositifolia L.

Phytochemical Targeting of STAT3 Orchestrated Lipid Metabolism in Therapy-Resistant Cancers

Lipids are critical for maintaining homeostasis and cellular metabolism. However, the dysregulation of lipid metabolism contributes to the pathogenesis of chronic inflammatory diseases and is a hallmark of several cancer types. Tumours exist in a microenvironment of poor vascularization-depleted oxygen and restricted nutrients. Under these conditions, tumours have been shown to increasingly depend on the metabolism of fatty acids for sustained proliferation and survival. Signal transducer and activator of transcription 3 (STAT3) plays a key role in cellular processes such as cell growth, apoptosis and lipid metabolism. Aberrant STAT3 activity, as seen in several cancer types, is associated with tumour progression and malignancy, in addition to propagating crosstalk between tumour cells and the microenvironment. Furthermore, STAT3-regulated lipid metabolism is critical for cancer stem cell self-renewal and therapy resistance. Plant-derived compounds known as phytochemicals are a potential source for novel cancer therapeutic drugs. Dietary phytochemicals are known to modulate key cellular signalling pathways involved in lipid homeostasis and metabolism, including the STAT3 signalling pathways. Targeting STAT3 orchestrated lipid metabolism has shown therapeutic promise in human cancer models. In this review, we summarize the antitumour activity of phytochemicals with an emphasis placed on their effect on STAT3-regulated lipid metabolism and their role in abrogating therapy resistance.

STAT3 Pathway in Gastric Cancer: Signaling, Therapeutic Targeting and Future Prospects

Molecular signaling pathways play a significant role in the regulation of biological mechanisms, and their abnormal expression can provide the conditions for cancer development. The signal transducer and activator of transcription 3 (STAT3) is a key member of the STAT proteins and its oncogene role in cancer has been shown. STAT3 is able to promote the proliferation and invasion of cancer cells and induces chemoresistance. Different downstream targets of STAT3 have been identified in cancer and it has also been shown that microRNA (miR), long non-coding RNA (lncRNA) and other molecular pathways are able to function as upstream mediators of STAT3 in cancer. In the present review, we focus on the role and regulation of STAT3 in gastric cancer (GC). miRs and lncRNAs are considered as potential upstream mediators of STAT3 and they are able to affect STAT3 expression in exerting their oncogene or onco-suppressor role in GC cells. Anti-tumor compounds suppress the STAT3 signaling pathway to restrict the proliferation and malignant behavior of GC cells. Other molecular pathways, such as sirtuin, stathmin and so on, can act as upstream mediators of STAT3 in GC. Notably, the components of the tumor microenvironment that are capable of targeting STAT3 in GC, such as fibroblasts and macrophages, are discussed in this review. Finally, we demonstrate that STAT3 can target oncogene factors to enhance the proliferation and metastasis of GC cells.