Cyclin D1 is transcriptionally regulated by and required for transformation by activated signal transducer and activator of transcription 3

5-AZA Upregulates SOCS3 and PTPN6/SHP1, Inhibiting STAT3 and Potentiating the Effects of AG490 against Primary Effusion Lymphoma Cells

Epigenetic modifications, including aberrant DNA methylation occurring at the promoters of oncogenes and oncosuppressor genes and histone modifications, can contribute to carcinogenesis. Aberrant methylation mediated by histone methylatransferases, alongside histones, can affect methylation of proteins involved in the regulation of pro-survival pathways such as JAK/STAT and contribute to their activation. In this study, we used DNA or histone demethylating agents, 5-Azacytidine (5-AZA) or DS-3201 (valemetostat), respectively, to treat primary effusion lymphoma (PEL) cells, alone or in combination with AG490, a Signal transducer and activator of transcription 3 (STAT3) inhibitor. Cell viability was investigated by trypan blue assay and FACS analysis. The molecular changes induced by 5-AZA and/or AG490 treatments were investigated by Western blot analysis, while cytokine release by PEL cells treated by these drugs was evaluated by Luminex. Statistical analyses were performed with Graphpad Prism® software (version 9) and analyzed by Student's t test or a nonparametric one-way ANOVA test. The results obtained in this study suggest that 5-AZA upregulated molecules that inhibit STAT3 tyrosine phosphorylation, namely Suppressor of Cytokine Signaling 3 (SOCS3) and tyrosine-protein phosphatase non-receptor type (PTPN) 6/Src homology region 2 domain-containing phosphatase-1 (SHP-1), reducing STAT3 activation and downregulating several STAT3 pro-survival targets in PEL cells. As this lymphoma is highly dependent on the constitutive activation of STAT3, 5-AZA impaired PEL cell survival, and when used in combination with AG490 JAK2/STAT3 inhibitor, it potentiated its cytotoxic effect. Differently from 5-AZA, the inhibition of the EZH1/2 histone methyltransferase by DS-3201, reported to contribute to STAT3 activation in other cancers, slightly affected STAT3 phosphorylation or survival in PEL cells, either alone or in combination with AG490. This study suggests that 5-AZA, by upregulating the expression level of SOCS3 and PTPN6/SHP1, reduced STAT3 activation and improved the outcome of treatment targeting this transcription factor in PEL cells.

CDK4/6 inhibitors in lung cancer: current practice and future directions

Lung cancer is the leading cause of cancer-related deaths worldwide, and ∼85% of lung cancers are classified as nonsmall cell lung cancer (NSCLC). These malignancies can proliferate indefinitely, in part due to dysregulation of the cell cycle and the resulting abnormal cell growth. The specific activation of cyclin-dependent kinases 4 and 6 (CDK4/6) is closely linked to tumour proliferation. Approximately 80% of human tumours exhibit abnormalities in the cyclin D-CDK4/6-INK4-RB pathway. Specifically, CDK4/6 inhibitors either as monotherapy or combination therapy have been investigated in pre-clinical and clinical studies for the treatment of NSCLC, and promising results have been achieved. This review article focuses on research regarding the use of CDK4/6 inhibitors in NSCLC, including the characteristics and mechanisms of action of approved drugs and progress of pre-clinical and clinical research.

IκB kinase-α coordinates BRD4 and JAK/STAT signaling to subvert DNA damage-based anticancer therapy

Activation of the IκB kinase (IKK) complex has recurrently been linked to colorectal cancer (CRC) initiation and progression. However, identification of downstream effectors other than NF-κB has remained elusive. Here, analysis of IKK-dependent substrates in CRC cells after UV treatment revealed that phosphorylation of BRD4 by IKK-α is required for its chromatin-binding at target genes upon DNA damage. Moreover, IKK-α induces the NF-κB-dependent transcription of the cytokine LIF, leading to STAT3 activation, association with BRD4 and recruitment to specific target genes. IKK-α abrogation results in defective BRD4 and STAT3 functions and consequently irreparable DNA damage and apoptotic cell death upon different stimuli. Simultaneous inhibition of BRAF-dependent IKK-α activity, BRD4, and the JAK/STAT pathway enhanced the therapeutic potential of 5-fluorouracil combined with irinotecan in CRC cells and is curative in a chemotherapy-resistant xenograft model. Finally, coordinated expression of LIF and IKK-α is a poor prognosis marker for CRC patients. Our data uncover a functional link between IKK-α, BRD4, and JAK/STAT signaling with clinical relevance.

Identification of Bulbocodin D and C as novel STAT3 inhibitors and their anticancer activities in lung cancer cells

Cancer stands as one of the predominant causes of mortality globally, necessitating ongoing efforts to develop innovative therapeutics. Historically, natural products have been foundational in the quest for anticancer agents. Bulbocodin D (BD) and Bulbocodin C (BC), two bibenzyls derived from Pleione bulbocodioides (Franch.) Rolfe, have demonstrated notable in vitro anticancer activity. In human lung cancer A549 cells, the IC50s for BD and BC were 11.63 and 11.71 μmol·L-1, respectively. BD triggered apoptosis, as evidenced by an upsurge in Annexin V-positive cells and elevated protein expression of cleaved-PARP in cancer cells. Furthermore, BD and BC markedly inhibited the migratory and invasive potentials of A549 cells. The altered genes identified through RNA-sequencing analysis were integrated into the CMap dataset, suggesting BD's role as a potential signal transducer and activator of transcription 3 (STAT3) inhibitor. SwissDock and MOE analyses further revealed that both BD and BC exhibited a commendable binding affinity with STAT3. Additionally, a surface plasmon resonance assay confirmed the direct binding affinity between these compounds and STAT3. Notably, treatment with either BD or BC led to a significant reduction in p-STAT3 (Tyr 705) protein levels, regardless of interleukin-6 stimulation in A549 cells. In addition, the extracellular signal-regulated kinase (ERK) was activated after BD or BC treatment. An enhancement in cancer cell mortality was observed upon combined treatment of BD and U0126, the MEK1/2 inhibitor. In conclusion, BD and BC emerge as promising novel STAT3 inhibitors with potential implications in cancer therapy.

AMPK-induced novel phosphorylation of RUNX1 inhibits STAT3 activation and overcome imatinib resistance in chronic myelogenous leukemia (CML) subjects

Imatinib resistance remains an unresolved problem in CML disease. Activation of JAK2/STAT3 pathway and increased expression of RUNX1 have become one reason for development of imatinib resistance in CML subjects. Metformin has gained attention as an antileukemic drug in recent times. However, the molecular mechanism remains elusive. The present study shows that RUNX1 is a novel substrate of AMP-activated kinase (AMPK), where AMPK phosphorylates RUNX1 at Ser 94 position. Activation of AMPK by metformin could lead to increased cytoplasmic retention of RUNX1 due to Ser 94 phosphorylation. RUNX1 Ser 94 phosphorylation resulted in increased interaction with STAT3, which was reflected in reduced transcriptional activity of both RUNX1 and STAT3 due to their cytoplasmic retention. The reduced transcriptional activity of STAT3 and RUNX1 resulted in the down-regulation of their signaling targets involved in proliferation and anti-apoptosis. Our cell proliferation assays using in vitro resistant cell line models and PBMCs isolated from CML clinical patients and normal subjects demonstrate that metformin treatment resulted in reduced growth and improved imatinib sensitivity of resistant subjects.

Targeting cyclin D1 as a therapeutic approach for papillary thyroid carcinoma

Cyclin D1 functions as a mitogenic sensor that specifically binds to CDK4/6, thereby integrating external mitogenic inputs and cell cycle progression. Cyclin D1 interacts with transcription factors and regulates various important cellular processes, including differentiation, proliferation, apoptosis, and DNA repair. Therefore, its dysregulation contributes to carcinogenesis. Cyclin D1 is highly expressed in papillary thyroid carcinoma (PTC). However, the particular cellular mechanisms through which abnormal cyclin D1 expression causes PTC are poorly understood. Unveiling the regulatory mechanisms of cyclin D1 and its function in PTC may help determine clinically effective strategies, and open up better opportunities for further research, leading to the development of novel PTC regimens that are clinically effective. This review explores the mechanisms underlying cyclin D1 overexpression in PTC. Furthermore, we discuss the role of cyclin D1 in PTC tumorigenesis via its interactions with other regulatory elements. Finally, recent progress in the development of therapeutic options targeting cyclin D1 in PTC is examined and summarized.

A dual-action niclosamide-based prodrug that targets cancer stem cells and inhibits TNBC metastasis

Chemotherapy typically destroys the tumor mass but rarely eradicates the cancer stem cells (CSCs) that can drive metastatic recurrence. A key current challenge is finding ways to eradicate CSCs and suppress their characteristics. Here, we report a prodrug, Nic-A, created by combining a carbonic anhydrase IX (CAIX) inhibitor, acetazolamide, with a signal transducer and transcriptional activator 3 (STAT3) inhibitor, niclosamide. Nic-A was designed to target triple-negative breast cancer (TNBC) CSCs and was found to inhibit both proliferating TNBC cells and CSCs via STAT3 dysregulation and suppression of CSC-like properties. Its use leads to a decrease in aldehyde dehydrogenase 1 activity, CD44high/CD24low stem-like subpopulations, and tumor spheroid-forming ability. TNBC xenograft tumors treated with Nic-A exhibited decreased angiogenesis and tumor growth, as well as decreased Ki-67 expression and increased apoptosis. In addition, distant metastases were suppressed in TNBC allografts derived from a CSC-enriched population. This study thus highlights a potential strategy for addressing CSC-based cancer recurrence.

STAT3 protects HSCs from intrinsic interferon signaling and loss of long-term blood-forming activity

STAT3 function in hematopoietic stem and progenitor cells (HSPCs) has been difficult to discern as Stat3 deficiency in the hematopoietic system induces systemic inflammation, which can impact HSPC activity. To address this, we established mixed bone marrow (BM) chimeric mice with CreER-mediated Stat3 deletion in 20% of the hematopoietic compartment. Stat3-deficient HSPCs had impaired hematopoietic activity and failed to undergo expansion in BM in contrast to Stat3-sufficient (CreER) controls. Single-cell RNA sequencing of Lin-ckit+Sca1+ BM cells revealed altered transcriptional responses in Stat3-deficient hematopoietic stem cells (HSCs) and multipotent progenitors, including intrinsic activation of cell cycle, stress response, and interferon signaling pathways. Consistent with their deregulation, Stat3-deficient Lin-ckit+Sca1+ cells accumulated γH2AX over time. Following secondary BM transplantation, Stat3-deficient HSPCs failed to reconstitute peripheral blood effectively, indicating a severe functional defect in the HSC compartment. Our results reveal essential roles for STAT3 in HSCs and suggest the potential for using targeted synthetic lethal approaches with STAT3 inhibition to remove defective or diseased HSPCs.

Synthesis and evaluation of naphthalene derivatives as potent STAT3 inhibitors and agents against triple-negative breast cancer growth and metastasis

PURPOSE

Triple-negative breast cancer (TNBC) represents the worst prognostic subtype of breast cancer and lacks targeted therapeutic drugs. Signal transducer and activator of transcription 3 (STAT3) is overexpressed and constitutively activated in TNBCs and associated with poor patient outcomes. However, no agents targeting STAT3 have been successfully developed and marketed. Selective Estrogen Receptor Modulators (SERMs) have been reported as potential inhibitors of the IL-6/STAT3 signaling pathway. Naphthalene compounds have good pharmacological activity and significant anti-cancer activity. In this study, we synthesized a new series of naphthalene derivatives with the general structure of SERM and evaluated their effects on TNBC and STAT3 signals.

METHODS

A new series of compounds based on the scaffold of SERMs and an amino group were designed and screened based on the structure-activity relationship by MTT assay. The binding activity of SMY002 to STAT3 was predicted and validated by docking and SPR. The STAT3 signaling target and anti-cancer effects of SMY002 were evaluated with three TNBC cell lines and the mice transplanted tumor model.

RESULTS

Among the compounds, SMY002 displayed the most potent activity, which could directly interact with STAT3 SH2-domain, and strongly inhibit the phosphorylation, dimerization, nuclear distribution, transcriptional activity, and target genes expression of STAT3. Furthermore, SMY002 markedly suppressed migration, invasion, survival, growth, and metastasis of TNBC cells in vitro and in vivo via down-regulating the expression of Cyclin D1 and MMP9.

CONCLUSIONS

SMY002 can significantly inhibit the growth and metastasis of TNBC cells by targeting the STAT3 signal.

Exposure of Immunogenic Tumor Antigens in Surrendered Immunity and the Significance of Autologous Tumor Cell-Based Vaccination in Precision Medicine

The mechanisms by which immune systems identify and destroy tumors, known as immunosurveillance, have been discussed for decades. However, several factors that lead to tumor persistence and escape from the attack of immune cells in a normal immune system have been found. In the process known as immunoediting, tumors decrease their immunogenicity and evade immunosurveillance. Furthermore, tumors exploit factors such as regulatory T cells, myeloid-derived suppressive cells, and inhibitory cytokines that avoid cytotoxic T cell (CTL) recognition. Current immunotherapies targeting tumors and their surroundings have been proposed. One such immunotherapy is autologous cancer vaccines (ACVs), which are characterized by enriched tumor antigens that can escalate specific CTL responses. Unfortunately, ACVs usually fail to activate desirable therapeutic effects, and the low immunogenicity of ACVs still needs to be elucidated. This difficulty highlights the significance of immunogenic antigens in antitumor therapies. Previous studies have shown that defective host immunity triggers tumor development by reprogramming tumor antigenic expressions. This phenomenon sheds new light on ACVs and provides a potential cue to improve the effectiveness of ACVs. Furthermore, synergistically with the ACV treatment, combinational therapy, which can reverse the suppressive tumor microenvironments, has also been widely proposed. Thus, in this review, we focus on tumor immunogenicity sculpted by the immune systems and discuss the significance and application of restructuring tumor antigens in precision medicine.

Breast cancers co-opt normal mechanisms of tolerance to promote immune evasion and metastasis

Normal developmental processes, such as those seen during embryonic development and postpartum mammary gland involution, can be reactivated by cancer cells to promote immune suppression, tumor growth, and metastatic spread. In mammalian embryos, paternal-derived antigens are at risk of being recognized as foreign by the maternal immune system. Suppression of the maternal immune response toward the fetus, which is mediated in part by the trophoblast, is critical to ensure embryonic survival and development. The postpartum mammary microenvironment also exhibits immunosuppressive mechanisms accompanying the massive cell death and tissue remodeling that occurs during mammary gland involution. These normal immunosuppressive mechanisms are paralleled during malignant transformation, where tumors can develop neoantigens that may be recognized as foreign by the immune system. To circumvent this, tumors can dedifferentiate and co-opt immune-suppressive mechanisms normally utilized during fetal tolerance and postpartum mammary involution. In this review, we discuss those similarities and how they can inform our understanding of cancer progression and metastasis.

Modulation of SOCS3 Levels via STAT3 and Estrogen-ERαp66 Signaling during Hepatitis E Virus Replication in Hepatocellular Carcinoma Cells

Hepatitis E virus (HEV) infection usually results in a self-limiting acute disease; however, in infected pregnant women, it is associated with increased mortality and fulminant hepatic failure. Estrogen is known to be elevated during pregnancy, and estrogen signaling via classical estrogen receptor-ERα is known to regulate hepatocyte function and host innate immune response, including the STAT3 pathway. In this study, we investigated whether the estrogen classical signaling pathway via ERαp66 has any effect on STAT3 activation during HEV replication and HEV-induced IFN response. We first demonstrated that Huh7-S10-3 liver cells expressed the nonfunctional estrogen receptor ERαp36 isoform and lack the functional ERαp66 isoform. We further showed persistent phosphorylated-STAT3 levels in genotype 3 human HEV (Kernow P6 strain) RNA-transfected cells at later time points. In Huh7-S10-3 cells, estrogen at first-to-third trimester concentration (7.3 to 73 nM) did not significantly affect HEV replication; however, blocking of STAT3 activation led to a decrease in the HEV ORF2 protein level. Our mechanistic study revealed that STAT3 differentially regulates SOCS3 and type-III interferon (IFN) levels during HEV replication and the presence of estrogen-ERαp66 signaling stabilizes SOCS3 levels in vitro. We also demonstrate that HEV infection in pregnant and nonpregnant rabbits led to a significant increase in IFN response as measured by increased levels of IFN-stimulated-gene-15 (ISG15) mRNA levels irrespective of pregnancy status. Collectively, the results indicate that estrogen signaling and STAT3 regulate SOCS3 and IFN responses in vitro during HEV replication. The results have important implications for understanding HEV replication and HEV-induced innate immune response in pregnant women. IMPORTANCE Hepatitis E is usually a self-resolving acute disease; however, in pregnant women, HEV infection is associated with high mortality and fulminant hepatic failure. During pregnancy, estrogen levels are elevated, and in the liver, the estrogen receptor ERα is predominant and estrogen signaling is known to regulate hepatocyte metabolism and leptin-induced STAT3 levels. Viruses can module host innate immune response via STAT3. Therefore, in this study, we investigated whether STAT3 and estrogen-classical signaling via the ERαp66 pathway modulate HEV replication and HEV-induced innate immune response. We demonstrated that estrogen signaling did not affect HEV replication in human liver cells, but blocking of STAT3 activation reduced HEV capsid protein levels in human liver cells. We also showed that inhibition of STAT3 activation reduced SOCS3 levels, while the presence of the estrogen-ERαp66 signaling pathway stabilized SOCS3 levels. The results from this study will aid our understanding of the mechanism of HEV pathogenesis and immune response during pregnancy.

Ethanolic extract of Origanum syriacum L. leaves exhibits potent anti-breast cancer potential and robust antioxidant properties

Background: Breast cancer (BC) is the second most common cancer overall. In women, BC is the most prevalent cancer and the leading cause of cancer-related mortality. Triple-negative BC (TNBC) is the most aggressive BC, being resistant to hormonal and targeted therapies. Hypothesis/Purpose: The medicinal plant Origanum syriacum L. is a shrubby plant rich in bioactive compounds and widely used in traditional medicine to treat various diseases. However, its therapeutic potential against BC remains poorly investigated. In the present study, we screened the phytochemical content of an ethanolic extract of O. syriacum (OSEE) and investigated its anticancer effects and possible underlying mechanisms of action against the aggressive and highly metastatic human TNBC cell line MDA-MB-231. Methods: MTT, trans-well migration, and scratch assays were used to assess cell viability, invasion, or migration, respectively. Antioxidant potential was evaluated in vitro using the DPPH radical-scavenging assay and levels of reactive oxygen species (ROS) were assessed in cells in culture using DHE staining. Aggregation assays were used to determine cell-cell adhesion. Flow cytometry was used to analyze cell cycle progression. Protein levels of markers of apoptosis (BCL-2, pro-Caspase3, p53), proliferation (p21, Ki67), cell migration, invasion, or adhesion (FAK, E-cadherin), angiogenesis (iNOS), and cell signaling (STAT3, p38) were determined by immunoblotting. A chorioallantoic Membrane (CAM) assay evaluated in ovo angiogenesis. Results: We demonstrated that OSEE had potent radical scavenging activity in vitro and induced the generation of ROS in MDA-MB-231 cells, especially at higher OSEE concentrations. Non-cytotoxic concentrations of OSEE attenuated cell proliferation and induced G₀/G₁ cell cycle arrest, which was associated with phosphorylation of p38 MAPK, an increase in the levels of tumor suppressor protein p21, and a decrease of proliferation marker protein Ki67. Additionally, only higher concentrations of OSEE were able to attenuate inhibition of proliferation induced by the ROS scavenger N-acetyl cysteine (NAC), indicating that the anti-proliferative effects of OSEE could be ROS-dependent. OSEE stimulated apoptosis and its effector Caspase-3 in MDA-MB-231 cells, in correlation with activation of the STAT3/p53 pathway. Furthermore, the extract reduced the migration and invasive properties of MDA-MB-231 cells through the deactivation of focal adhesion kinase (FAK). OSEE also reduced the production of inducible nitric oxide synthase (iNOS) and inhibited in ovo angiogenesis. Conclusion: Our findings reveal that OSEE is a rich source of phytochemicals and has robust anti-breast cancer properties that significantly attenuate the malignant phenotype of MD-MB-231 cells, suggesting that O. syriacum may not only act as a rich source of potential TNBC therapeutics but may also provide new avenues for the design of novel TNBC drugs.

Role of STAT3 in the initiation, progression, proliferation and metastasis of breast cancer and strategies to deliver JAK and STAT3 inhibitors

INTRODUCTION

Breast cancer (BC) accounts for the majority of cancers among the female population. Anomalous activation of various signaling pathways has become an issue of concern. The JAK-STAT signaling pathway is activated in numerous cancers, including BC. STAT3 is widely involved in BCs, as 40 % of BCs display phosphorylated STAT3. JAK-STAT signaling is crucial for proliferation, survival, metastasis and other cellular events associated with the tumor microenvironment. Hence, targeting this pathway has become an area of interest among researchers.

KEY FINDINGS

This review article focuses on the role of STAT3 in the initiation, proliferation, progression and metastasis of BC. The roles of various phytochemicals, synthetic molecules and biologicals against JAK-STAT and STAT3 in various cancers have been discussed, with special emphasis on BC.

SIGNIFICANCE

JAK and STAT3 are involved in various phases from initiation to metastasis, and targeting this pathway is a promising approach to inhibit the various stages of BC development and to prevent metastasis. A number of phytochemicals and synthetic and biological molecules have demonstrated potential inhibitory effects on JAK and STAT3, thereby paving the way for the development of better therapeutics against BC.

Multifunctionality of Calebin A in inflammation, chronic diseases and cancer

Chronic diseases including cancer have high case numbers as well as mortality rates. The efficient treatment of chronic diseases is a major ongoing medical challenge worldwide, because of their complexity and many inflammatory pathways such as JNK, p38/MAPK, MEK/ERK, JAK/STAT3, PI3K and NF-κB among others being implicated in their pathogenesis. Together with the versatility of chronic disease classical mono-target therapies are often insufficient. Therefore, the anti-inflammatory as well as anti-cancer capacities of polyphenols are currently investigated to complement and improve the effect of classical anti-inflammatory drugs, chemotherapeutic agents or to overcome drug resistance of cancer cells. Currently, research on Calebin A, a polyphenolic component of turmeric (Curcuma longa), is becoming of growing interest with regard to novel treatment strategies and has already been shown health-promoting as well as anti-tumor properties, including anti-oxidative and anti-inflammatory effects, in diverse cancer cells. Within this review, we describe already known anti-inflammatory activities of Calebin A via modulation of NF-κB and its associated signaling pathways, linked with TNF-α, TNF-β and COX-2 and further summarize Calebin A’s tumor-inhibiting properties that are known up to date such as reduction of cancer cell viability, proliferation as well as metastasis. We also shed light on possible future prospects of Calebin A as an anti-cancer agent.

Tanshinone IIA-regulation of IL-6 antagonizes PM2 .5 -induced proliferation of human bronchial epithelial cells via a STAT3/miR-21 reciprocal loop

Particulate matter 2.5 (PM_2.5 ), a component of atmospheric particulate matter, leads to changes in gene expression and cellular functions. Epidemiological evidence confirms that PM_2.5 has a positive correlation with lung injury. However, the molecular mechanisms involved remain poorly understood, and preventive methods are needed. In the present study, with human bronchial epithelial (HBE) cells in culture, we showed that low concentrations of PM_2.5 resulted in acceleration of the G1/S transition and cell proliferation. Consistent with these effects, expression of the pro-inflammatory factor interleukin-6 (IL-6) was elevated in HBE cells exposed to PM_2.5 . Accordingly, signal transducer and activator of transcription 3 (STAT3) was activated, which down-regulated expression of cyclin D1. In addition, PM_2.5 exposure led to higher levels of miR-21, and there was a reciprocal loop between miR-21 and STAT3. For HBE cells, tanshinone IIA (Tan IIA) reversed the PM_2.5 -induced cell cycle alteration and cell proliferation, and reduced the expression of cytokines (IL-6, STAT3, and miR-21). These results show that, for HBE cells, Tan IIA attenuates the PM_2.5 -induced G1/S alteration and cell proliferation, and indicate that it has potential clinical application for PM_2.5 -induced respiratory injuries.

The TRiCky Business of Protein Folding in Health and Disease

Maintenance of the cellular proteome or proteostasis is an essential process that when deregulated leads to diseases like neurological disorders and cancer. Central to proteostasis are the molecular chaperones that fold proteins into functional 3-dimensional (3D) shapes and prevent protein aggregation. Chaperonins, a family of chaperones found in all lineages of organisms, are efficient machines that fold proteins within central cavities. The eukaryotic Chaperonin Containing TCP1 (CCT), also known as Tailless complex polypeptide 1 (TCP-1) Ring Complex (TRiC), is a multi-subunit molecular complex that folds the obligate substrates, actin, and tubulin. But more than folding cytoskeletal proteins, CCT differs from most chaperones in its ability to fold proteins larger than its central folding chamber and in a sequential manner that enables it to tackle proteins with complex topologies or very large proteins and complexes. Unique features of CCT include an asymmetry of charges and ATP affinities across the eight subunits that form the hetero-oligomeric complex. Variable substrate binding capacities endow CCT with a plasticity that developed as the chaperonin evolved with eukaryotes and acquired functional capacity in the densely packed intracellular environment. Given the decades of discovery on the structure and function of CCT, much remains unknown such as the scope of its interactome. New findings on the role of CCT in disease, and potential for diagnostic and therapeutic uses, heighten the need to better understand the function of this essential molecular chaperone. Clues as to how CCT causes cancer or neurological disorders lie in the early studies of the chaperonin that form a foundational knowledgebase. In this review, we span the decades of CCT discoveries to provide critical context to the continued research on the diverse capacities in health and disease of this essential protein-folding complex.

IL-6/JAK/STAT3 Signaling in Breast Cancer Metastasis: Biology and Treatment

Breast cancer is the most commonly diagnosed cancer in women. Metastasis is the primary cause of mortality for breast cancer patients. Multiple mechanisms underlie breast cancer metastatic dissemination, including the interleukin-6 (IL-6)-mediated signaling pathway. IL-6 is a pleiotropic cytokine that plays an important role in multiple physiological processes including cell proliferation, immune surveillance, acute inflammation, metabolism, and bone remodeling. IL-6 binds to the IL-6 receptor (IL-6Rα) which subsequently binds to the glycoprotein 130 (gp130) receptor creating a signal transducing hexameric receptor complex. Janus kinases (JAKs) are recruited and activated; activated JAKs, in turn, phosphorylate signal transducer and activator of transcription 3 (STAT3) for activation, leading to gene regulation. Constitutively active IL-6/JAK/STAT3 signaling drives cancer cell proliferation and invasiveness while suppressing apoptosis, and STAT3 enhances IL-6 signaling to promote a vicious inflammatory loop. Aberrant expression of IL-6 occurs in multiple cancer types and is associated with poor clinical prognosis and metastasis. In breast cancer, the IL-6 pathway is frequently activated, which can promote breast cancer metastasis while simultaneously suppressing the anti-tumor immune response. Given these important roles in human cancers, multiple components of the IL-6 pathway are promising targets for cancer therapeutics and are currently being evaluated preclinically and clinically for breast cancer. This review covers the current biological understanding of the IL-6 signaling pathway and its impact on breast cancer metastasis, as well as, therapeutic interventions that target components of the IL-6 pathway including: IL-6, IL-6Rα, gp130 receptor, JAKs, and STAT3.

Ailanthone suppresses the activity of human colorectal cancer cells through the STAT3 signaling pathway

Ailanthone (AIL) is a major quassinoid extracted from the Chinese medicinal herb, Ailanthus altissima, which has been reported to exert anti-proliferative effects on various cancer cells. The present study aimed to investigate the anti-tumor effects of AIL on HCT116 and SW620 colon cancer cells, and to analyze the underlying molecular mechanisms. CCK-8 assay was used to detect cell viability. Furthermore, colony formation and Transwell assays, and flow cytometry were used to examine the effects of AIL on cell proliferation, apoptosis and migration. Finally, the expression levels of cell cycle control proteins, and caspase and Bcl-2 family-related proteins involved in the regulation of apoptosis, as well as those of cell migration- and pathway-related proteins were examined using western blot analysis. Reverse transcription-quantitative PCR was used to quantitatively analyze the changes in the JAK and STAT3 gene levels in each group. The in vitro cell function tests revealed that AIL inhibited the proliferation and migration, and induced the apoptosis and cell cycle arrest of HCT116 and SW620 cells. It was further found exerted these effects via the JAK/STAT3 signaling pathway, as well as through caspase and Bcl-2 family proteins. On the whole, the present study demonstrates that AIL suppresses the activity of colon cancer cells via the STAT3 pathway.

Pharmacologic Antagonization of Cannabinoid Receptor 1 Improves Cholestasis in Abcb4-/- Mice

BACKGROUND & AIMS

The endocannabinoid system is involved in the modulation of inflammatory, fibrotic, metabolic, and carcinogenesis-associated signaling pathways via cannabinoid receptor (CB)1 and CB2. We hypothesized that the pharmacologic antagonization of CB1 receptor improves cholestasis in Abcb4^-/- mice.

METHODS

After weaning, male Abcb4^-/- mice were treated orally with rimonabant (a specific antagonist of CB1) or ACEA (an agonist of CB1) until up to 16 weeks of age. Liver tissue and serum were isolated and examined by means of serum analysis, quantitative real time polymerase chain reaction, Western blot, immunohistochemistry, and enzyme function. Untreated Abcb4^-/- and Bagg Albino Mouse/c wild-type mice served as controls.

RESULTS

Cholestasis-induced symptoms such as liver damage, bile duct proliferation, and enhanced circulating bile acids were improved by CB1 antagonization. Rimonabant treatment also improved Phosphoenolpyruvat-Carboxykinase expression and reduced inflammation and the acute-phase response. The carcinogenesis-associated cellular-Jun N-terminal kinase/cellular-JUN and signal transducer and activator of transcription 3 signaling pathways activated in Abcb4^-/- mice were reduced to wild-type level by CB1 antagonization.

CONCLUSIONS

We showed a protective effect of oral CB1 antagonization in chronic cholestasis using the established Abcb4^-/- model. Our results suggest that pharmacologic antagonization of the CB1 receptor could have a therapeutic benefit in cholestasis-associated metabolic changes, liver damage, inflammation, and carcinogenesis.

Multicellular Effects of STAT3 in Non-small Cell Lung Cancer: Mechanistic Insights and Therapeutic Opportunities

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and accounts for 85% of lung cancer cases. Aberrant activation of the Signal Transducer and Activator of Transcription 3 (STAT3) is frequently observed in NSCLC and is associated with a poor prognosis. Pre-clinical studies have revealed an unequivocal role for tumor cell-intrinsic and extrinsic STAT3 signaling in NSCLC by promoting angiogenesis, cell survival, cancer cell stemness, drug resistance, and evasion of anti-tumor immunity. Several STAT3-targeting strategies have also been investigated in pre-clinical models, and include preventing upstream receptor/ligand interactions, promoting the degradation of STAT3 mRNA, and interfering with STAT3 DNA binding. In this review, we discuss the molecular and immunological mechanisms by which persistent STAT3 activation promotes NSCLC development, and the utility of STAT3 as a prognostic and predictive biomarker in NSCLC. We also provide a comprehensive update of STAT3-targeting therapies that are currently undergoing clinical evaluation, and discuss the challenges associated with these treatment modalities in human patients.

The concerted change in the distribution of cell cycle phases and zone composition in germinal centers is regulated by IL-21

Humoral immune responses require germinal centres (GC) for antibody affinity maturation. Within GC, B cell proliferation and mutation are segregated from affinity-based positive selection in the dark zone (DZ) and light zone (LZ) substructures, respectively. While IL-21 is known to be important in affinity maturation and GC maintenance, here we show it is required for both establishing normal zone representation and preventing the accumulation of cells in the G1 cell cycle stage in the GC LZ. Cell cycle progression of DZ B cells is unaffected by IL-21 availability, as is the zone phenotype of the most highly proliferative GC B cells. Collectively, this study characterises the development of GC zones as a function of time and B cell proliferation and identifies IL-21 as an important regulator of these processes. These data help explain the requirement for IL-21 in normal antibody affinity maturation.

STAT proteins: a kaleidoscope of canonical and non-canonical functions in immunity and cancer

STAT proteins represent an important family of evolutionarily conserved transcription factors that play key roles in diverse biological processes, notably including blood and immune cell development and function. Classically, STAT proteins have been viewed as inducible activators of transcription that mediate cellular responses to extracellular signals, particularly cytokines. In this 'canonical' paradigm, latent STAT proteins become tyrosine phosphorylated following receptor activation, typically via downstream JAK proteins, facilitating their dimerization and translocation into the nucleus where they bind to specific sequences in the regulatory region of target genes to activate transcription. However, growing evidence has challenged this paradigm and identified alternate 'non-canonical' functions, such as transcriptional repression and roles outside the nucleus, with both phosphorylated and unphosphorylated STATs involved. This review provides a revised framework for understanding the diverse kaleidoscope of STAT protein functional modalities. It further discusses the implications of this framework for our understanding of STAT proteins in normal blood and immune cell biology and diseases such as cancer, and also provides an evolutionary context to place the origins of these alternative functional modalities.

Molecular Biology Networks and Key Gene Regulators for Inflammatory Biomarkers Shared by Breast Cancer Development: Multi-Omics Systems Analysis

As key inflammatory biomarkers C-reactive protein (CRP) and interleukin-6 (IL6) play an important role in the pathogenesis of non-inflammatory diseases, including specific cancers, such as breast cancer (BC). Previous genome-wide association studies (GWASs) have neither explained the large proportion of genetic heritability nor provided comprehensive understanding of the underlying regulatory mechanisms. We adopted an integrative genomic network approach by incorporating our previous GWAS data for CRP and IL6 with multi-omics datasets, such as whole-blood expression quantitative loci, molecular biologic pathways, and gene regulatory networks to capture the full range of genetic functionalities associated with CRP/IL6 and tissue-specific key drivers (KDs) in gene subnetworks. We applied another systematic genomics approach for BC development to detect shared gene sets in enriched subnetworks across BC and CRP/IL6. We detected the topmost significant common pathways across CRP/IL6 (e.g., immune regulatory; chemokines and their receptors; interferon γ, JAK-STAT, and ERBB4 signaling), several of which overlapped with BC pathways. Further, in gene–gene interaction networks enriched by those topmost pathways, we identified KDs—both well-established (e.g., JAK1/2/3, STAT3) and novel (e.g., CXCR3, CD3D, CD3G, STAT6)—in a tissue-specific manner, for mechanisms shared in regulating CRP/IL6 and BC risk. Our study may provide robust, comprehensive insights into the mechanisms of CRP/IL6 regulation and highlight potential novel genetic targets as preventive and therapeutic strategies for associated disorders, such as BC.

Targeting of cyclin-dependent kinases in atypical teratoid rhabdoid tumors with multikinase inhibitor TG02

OBJECTIVE

Atypical teratoid rhabdoid tumors (ATRTs) are aggressive pediatric brain tumors with no current standard of care and an estimated median patient survival of 12 to 18 months. Previous genetic analyses have implicated cyclin D1 and enhancer of zeste homolog 2 (EZH2), a histone methyltransferase that is implicated in many cancers, as key drivers of tumorigenicity in ATRTs. Since the effects of EZH2 and cyclin D1 are facilitated by a host of cyclin-dependent kinases (CDKs), the authors sought to investigate the potential therapeutic effects of targeting CDKs in ATRTs with the multi-CDK inhibitor, TG02.

METHODS

Human ATRT cell lines BT12, BT37, CHLA05, and CHLA06 were selected for investigation. The effects of TG02 on cell viability, proliferation, clonogenicity, and apoptosis were assessed via Cell Counting Kit-8 assays, cell counting, clonogenic assays, and flow cytometry, respectively. Similar methods were used to determine the effects of TG02 combined with radiation therapy (RT) or cisplatin. Synergism indices for TG02-cisplatin combination therapy were calculated using CompuSyn software.

RESULTS

TG02 was observed to significantly impair ATRT cell growth in vitro by limiting cell proliferation and clonogenicity, and by inducing apoptosis. TG02 inhibited ATRT cell proliferation and decreased cell viability in a dose-dependent manner with nanomolar half maximal effective concentration (EC50) values (BT12, 207.0 nM; BT37, 127.8 nM; CHLA05, 29.7 nM; CHLA06, 18.7 nM). TG02 (150 nM) dramatically increased the proportion of apoptotic ATRT cells 72 hours posttreatment (TG02 8.50% vs control 1.52% apoptotic cells in BT12, p < 0.0001; TG02 70.07% vs control 15.36%, p < 0.0001). Combination therapy studies revealed that TG02 acted as a potent radiosensitizer in ATRT cells (BT12 surviving fraction, RT 51.2% vs RT + TG02 21.7%). Finally, CompuSyn analysis demonstrated that TG02 acted synergistically with cisplatin against ATRT cells at virtually all therapeutic doses. These findings were consistent in cell lines that cover all three molecular subgroups of ATRTs.

CONCLUSIONS

The results of this investigation have established that TG02 is an effective therapeutic against ATRTs in vitro. Given the lack of standard therapy for ATRTs, these findings help fill an unmet need and support further study of TG02 as a potential therapeutic option for patients with this deadly disease.

Resolvin D1 suppresses inflammation-associated tumorigenesis in the colon by inhibiting IL-6-induced mitotic spindle abnormality

While failure in resolution of inflammation is considered to increase the risk of tumorigenesis, there is paucity of experimental as well as clinical evidence supporting this association. Resolvin D1 (RvD1) is a representative pro-resolving lipid mediator that is endogenously generated from docosahexaenoic acid for the resolution of inflammation. Here, we report a decreased level of RvD1 in the blood from colorectal cancer patients and mice having inflammation-induced colon cancer, suggesting plasma RvD1 as a potential biomarker for monitoring colorectal cancer. Administration of RvD1 attenuated dextran sodium sulfate (DSS)-induced colitis and azoxymethane (AOM) plus DSS-induced colorectal carcinogenesis by suppressing the production of interleukin-6 (IL-6) and IL-6-mediated chromosomal instability. The protective effect of RvD1 against chromosomal instability is associated with downregulation of IL-6-induced Cyclin D1 expression, which appears to be mediated by blocking the Janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) axis. RvD1 inhibited the STAT3 signaling pathway by interfering with the binding of IL-6 to its receptor (IL-6R), suggesting the novel function of RvD1 as a putative IL-6R antagonist. Together, our findings suggest that RvD1-mediated blockade of IL-6 signal transmission may contribute to inhibition of chromosomal instability and tumorigenesis.

Tumor-Induced Inflammatory Cytokines and the Emerging Diagnostic Devices for Cancer Detection and Prognosis

Chronic inflammation generated by the tumor microenvironment is known to drive cancer initiation, proliferation, progression, metastasis, and therapeutic resistance. The tumor microenvironment promotes the secretion of diverse cytokines, in different types and stages of cancers. These cytokines may inhibit tumor development but alternatively may contribute to chronic inflammation that supports tumor growth in both autocrine and paracrine manners and have been linked to poor cancer outcomes. Such distinct sets of cytokines from the tumor microenvironment can be detected in the circulation and are thus potentially useful as biomarkers to detect cancers, predict disease outcomes and manage therapeutic choices. Indeed, analyses of circulating cytokines in combination with cancer-specific biomarkers have been proposed to simplify and improve cancer detection and prognosis, especially from minimally-invasive liquid biopsies, such as blood. Additionally, the cytokine signaling signatures of the peripheral immune cells, even from patients with localized tumors, are recently found altered in cancer, and may also prove applicable as cancer biomarkers. Here we review cytokines induced by the tumor microenvironment, their roles in various stages of cancer development, and their potential use in diagnostics and prognostics. We further discuss the established and emerging diagnostic approaches that can be used to detect cancers from liquid biopsies, and additionally the technological advancement required for their use in clinical settings.

Inhibition of Ras and STAT3 activity of 4-(tert-butyl)-N-carbamoylbenzamide as antiproliferative agent in HER2-expressing breast cancer cells

OBJECTIVES

Human epidermal growth factor receptor type 2 (HER2)-expressing breast cancer patients indicate poor prognosis in disease progression. HER2 overexpression can increase activities of Ras-mitogen activated protein kinase (Ras-MAPK) pathway and Janus Kinase (JAK)-STAT3, increasing breast cancer cell proliferation as demonstrated by marker Ki67. Therapeutic options for HER2-expressing breast cancer are limited and have major side effects, so anticancer development as an antiproliferative is needed. From previous research, synthetic chemical 4-(tert-butyl)-N-carbamoylbenzamide (4TBCB) compound has cytotoxic activity in vitro on HER2-expressing breast cancer cells. This study wanted to determine the mechanism 4TBCB compound in inhibiting HER2 signaling through Rat Sarcoma (Ras) and signal transducer and activator of transcription 3 (STAT3) pathway in HER2-expressing breast cancer cells.

METHODS

Breast cancer cells were isolated from the biopsy tissue of breast cancer patients. The isolated cells were cultured and given 4TBCB test compound with three concentrations (0.305, 0.61, and 1.22 mM) and lapatinib 0.05 mM as a comparison compound. Cancer cell cultures were stained with monoclonal antibodies phosphorylated HER2 (pHER2), phosphorylated Ras (pRas), phosphorylated STAT3 (pSTAT3), and Ki67. The expression of pHER2, pRas, pSTAT3, and Ki67 proteins was observed using the immunofluorescence method and the results were compared with control cells, namely cancer cells that were not given 4TBCB and lapatinib but stained with monoclonal antibodies.

RESULTS

4TBCB compounds (0.61 and 1.22 mM) and lapatinib can reduce pHER2, pRas, pSTAT3, and Ki67 expressions compared to control cells.

CONCLUSIONS

4TBCB compounds (0.61 and 1.22 mM) can reduce pHER2, pRas, pSTAT3, Ki67 expressions and predicted to inhibit HER2 signaling through the Ras and STAT3 pathways in HER2-expressing breast cancer cells.

STAT3 activation in thymic epithelial tumors: correlation with cyclin D1, JAK3, and clinical behavior

OBJECTIVES

Thymic epithelial tumors are the most common adult mediastinal tumors; however, their growth mechanism remains relatively unknown. Among the JAK/STAT pathway-related proteins, which control various intracellular events, STAT3 is deeply involved in cell proliferation. Constitutive activation of STAT3 and the resulting overexpression of cyclin D1 have been confirmed in various tumors, but have not been thoroughly investigated in thymic epithelial tumors. In this study, we immunohistochemically examined STAT3 activation, cyclin D1 expression, and JAK3 activation in thymic epithelial tumors and statistically analyzed their correlation with clinicopathological features.

METHODS

Formalin-fixed paraffin-embedded specimens of 94 thymic epithelial tumors surgically resected at Kyorin University Hospital between 2005 and 2018 were included in this study. pSTAT3, cyclin D1, and pJAK3 were immunohistochemically examined, and the correlation with histology, Masaoka stage, and survival time was statistically analyzed.

RESULTS

Cyclin D1 was found to be significantly overexpressed in the STAT3-activated group. This phenomenon was associated with histology and Masaoka stage. JAK3 was also activated in thymic epithelial tumors; however, JAK3 and STAT3 activation were not always correlated. Using survival time analysis, the STAT3-activated group, cyclin D1-expressed group, and JAK3-activated group had significantly lower progression-free survival times than those for both the non-activated and non-expressed groups.

CONCLUSIONS

STAT3 activation may promote cyclin D1 overexpression in thymic epithelial tumors, and intracellular signaling pathways other than JAK3 may be involved in STAT3 activation. STAT3 activation, cyclin D1 overexpression, and JAK3 activation are biomarker candidates that indicate clinically poor prognosis.

Periplogenin suppresses the growth of esophageal squamous cell carcinoma in vitro and in vivo by targeting STAT3

The mortality rate of esophageal squamous cell carcinoma (ESCC) is higher than that of other cancers worldwide owing to a lack of therapeutic targets and related drugs. This study aimed to find new drugs by targeting an efficacious therapeutic target in ESCC patients. Signal transducer and activator of transcription 3 (STAT3) is hyperactive in ESCC. Herein, we identified a novel STAT3 inhibitor, periplogenin, which strongly inhibited phosphorylation of STAT3 at Tyr705. Docking models and pull-down assays revealed that periplogenin bound directly and specifically to STAT3, leading to significant suppression of subsequent dimerization, nuclear import, and transcription activities. In addition, STAT3 knockdown cell lines were insensitive to periplogenin, whereas in contrast, STAT3-overexpressing cells were more sensitive to periplogenin, indicating that STAT3 was a target of periplogenin. Intraperitoneally administered periplogenin exhibited efficacious therapeutic effects in ESCC patient-derived xenograft models and dramatically impaired the phosphorylation of STAT3 and expression levels of STAT3-mediated downstream genes. Thus, our study demonstrated that periplogenin acted as a new STAT3 inhibitor, suppressing the growth of ESCC in vitro and in vivo, providing a basis for its potential application in ESCC treatment and prevention.

A comprehensive review on anticancer mechanism of bazedoxifene

Cancer is counted as a second leading cause of death among nontransmissible diseases. Identification of novel anticancer drugs is therefore necessary for the effective treatment of cancer. Conventional drug discovery is time consuming and expensive process. Unlike conventional drug discovery, drug repositioning offers a novel strategy for urgent drug discovery since it is a cost-effective and faster process. Bazedoxifene (BZA) is a synthetic selective estrogen receptor modulator, approved by the United States Food and Drug Administration for the treatment of osteoporosis in postmenopausal women. BZA is now being studied for its anticancer activity in various cancers including breast cancer, liver cancer, pancreatic cancer, colon cancer, head and neck cancer, medulloblastoma, brain cancer, and gastrointestinal cancer. Studies have reported that BZA is effective in reducing cancer progression through multiple mechanisms. BZA could effectively inhibit STAT3, PI3K/AKT, and MAPK signaling pathways and induce apoptosis. In addition to its anticancer activity as monotherapy, BZA has been shown to enhance the chemotherapeutic efficacy of clinical drugs such as paclitaxel, cisplatin, palbociclib, and oxaliplatin in multiple neoplasms. This review mainly focused on the anticancer activity, cellular targets, and anticancer mechanism of BZA, which may help the further design and conduct of research and repositioning it for oncological clinic trials.

The regulation of cyclin D promoters - review

Cyclins are key regulators of cell cycle progression and survival. Particularly cyclins D (cyclin D1, D2, and D3) act in response to the mitogenic stimulation and are pivotal mediators between proliferative pathways and the nuclear cell cycle machinery. Dysregulation of cyclins expression results in impaired development, abnormal cell growth or tumorigenesis. In this review we summarize current knowledge about regulatory role of the cyclin D promoters, transcriptional factors: regulators, co-activators and adaptor proteins necessary to their activation. We focused on the intracellular signaling pathways vital to cell growth, differentiation and apoptosis including transcription factor families: activator protein 1 (AP1), nuclear factor (NFκB), signal transducer and activator of transcription (STAT), cAMP response element-binding protein (CREB) and Sp/NF-Y, with a special insight into the tissue specific cyclin representation.

CREPT/RPRD1B promotes tumorigenesis through STAT3-driven gene transcription in a p300-dependent manner

BACKGROUND

Signal transducer and activator of transcription 3 (STAT3) has been shown to upregulate gene transcription during tumorigenesis. However, how STAT3 initiates transcription remains to be exploited. This study is to reveal the role of CREPT (cell cycle-related and elevated-expression protein in tumours, or RPRD1B) in promoting STAT3 transcriptional activity.

METHODS

BALB/c nude mice, CREPT overexpression or deletion cells were employed for the assay of tumour formation, chromatin immunoprecipitation, assay for transposase-accessible chromatin using sequencing.

RESULTS

We demonstrate that CREPT, a recently identified oncoprotein, enhances STAT3 transcriptional activity to promote tumorigenesis. CREPT expression is positively correlated with activation of STAT3 signalling in tumours. Deletion of CREPT led to a decrease, but overexpression of CREPT resulted in an increase, in STAT3-initiated tumour cell proliferation, colony formation and tumour growth. Mechanistically, CREPT interacts with phosphorylated STAT3 (p-STAT3) and facilitates p-STAT3 to recruit p300 to occupy at the promoters of STAT3-targeted genes. Therefore, CREPT and STAT3 coordinately facilitate p300-mediated acetylation of histone 3 (H3K18ac and H3K27ac), further augmenting RNA polymerase II recruitment. Accordingly, depletion of p300 abolished CREPT-enhanced STAT3 transcriptional activity.

CONCLUSIONS

We propose that CREPT is a co-activator of STAT3 for recruiting p300. Our study provides an alternative strategy for the therapy of cancers related to STAT3.

The Multifaced Role of STAT3 in Cancer and Its Implication for Anticancer Therapy

Signal transducer and activator of transcription (STAT) 3 is one of the most complex regulators of transcription. Constitutive activation of STAT3 has been reported in many types of tumors and depends on mechanisms such as hyperactivation of receptors for pro-oncogenic cytokines and growth factors, loss of negative regulation, and excessive cytokine stimulation. In contrast, somatic STAT3 mutations are less frequent in cancer. Several oncogenic targets of STAT3 have been recently identified such as c-myc, c-Jun, PLK-1, Pim1/2, Bcl-2, VEGF, bFGF, and Cten, and inhibitors of STAT3 have been developed for cancer prevention and treatment. However, despite the oncogenic role of STAT3 having been widely demonstrated, an increasing amount of data indicate that STAT3 functions are multifaced and not easy to classify. In fact, the specific cellular role of STAT3 seems to be determined by the integration of multiple signals, by the oncogenic environment, and by the alternative splicing into two distinct isoforms, STAT3α and STAT3β. On the basis of these different conditions, STAT3 can act both as a potent tumor promoter or tumor suppressor factor. This implies that the therapies based on STAT3 modulators should be performed considering the pleiotropic functions of this transcription factor and tailored to the specific tumor type.

STAT3 plays an important role in DNA replication by turning on WDHD1

BACKGROUND

Signal transducers and activators of transcription 3 (STAT3) is a transcription factor that plays a key role in many cellular processes such as cell growth and cancer. However, the functions and mechanisms by which STAT3 regulates cellular processes are not fully understood.

RESULTS

Here we describe a novel function of STAT3. We demonstrated that STAT3 plays an important role in DNA replication. Specifically, knockdown of STAT3 reduced DNA replication while activation and ectopic expression of STAT3 promoted DNA replication. We further identified the WD repeat and HMG-box DNA-binding protein 1 (WDHD1), which plays an important role in DNA replication initiation, as a novel STAT3 target gene that mediated the DNA replication function of STAT3. We showed that STAT3 bind the promoter/up regulatory region of WDHD1 gene.

CONCLUSIONS

These studies identified a novel function of STAT3 that is mediated by its newly identified target gene WDHD1 and have important implications.

Selective inhibition of CDK4/6: A safe and effective strategy for developing anticancer drugs

The sustained cell proliferation resulting from dysregulation of the cell cycle and activation of cyclin-dependent kinases (CDKs) is a hallmark of cancer. The inhibition of CDKs is a highly promising and attractive strategy for the development of anticancer drugs. In particular, third-generation CDK inhibitors can selectively inhibit CDK4/6 and regulate the cell cycle by suppressing the G1 to S phase transition, exhibiting a perfect balance between anticancer efficacy and general toxicity. To date, three selective CDK4/6 inhibitors have received approval from the U.S. Food and Drug Administration (FDA), and 15 CDK4/6 inhibitors are in clinical trials for the treatment of cancers. In this perspective, we discuss the crucial roles of CDK4/6 in regulating the cell cycle and cancer cells, analyze the rationale for selectively inhibiting CDK4/6 for cancer treatment, review the latest advances in highly selective CDK4/6 inhibitors with different chemical scaffolds, explain the mechanisms associated with CDK4/6 inhibitor resistance and describe solutions to overcome this issue, and briefly introduce proteolysis targeting chimera (PROTAC), a new and revolutionary technique used to degrade CDK4/6.

Progress in Understanding the IL-6/STAT3 Pathway in Colorectal Cancer

As a pleiotropic cytokine, interleukin-6 (IL-6) not only regulates the cellular immune response, but it also promotes tumor development by activating multiple carcinogenic pathways. IL-6 expression is significantly elevated in colorectal cancer (CRC) and is closely related to CRC development and patient prognosis. In CRC, IL-6 activates signal transducers and activators of transduction-3 (STAT3) to promote tumor initiation and tumor growth. IL-6/STAT3 signalling has a profound effect on tumor-infiltrating immune cells in the tumor immune microenvironment in CRC. Additionally, IL-6/STAT3 pathway activates downstream target genes to protect tumor cells from apoptosis; drive tumor cell proliferation, cell cycle progression, invasion and metastasis; promote tumor angiogenesis; and stimulate drug resistance. Therefore, a thorough understanding of the many effects of the IL-6/STAT3 pathway in CRC is needed, which the present review examines.

Case report: 16-yr life history and genomic evolution of an ER+ HER2- breast cancer

Metastatic breast cancer is one of the leading causes of cancer-related death in women. Limited studies have been done on the genomic evolution between primary and metastatic breast cancer. We reconstructed the genomic evolution through the 16-yr history of an ER+ HER2- breast cancer patient to investigate molecular mechanisms of disease relapse and treatment resistance after long-term exposure to hormonal therapy. Genomic and transcriptome profiling was performed on primary breast tumor (2002), initial recurrence (2012), and liver metastasis (2015) samples. Cell-free DNA analysis was performed at 11 time points (2015-2017). Mutational analysis revealed a low mutational burden in the primary tumor that doubled at the time of progression, with driver mutations in PI3K-Akt and RAS-RAF signaling pathways. Phylogenetic analysis showed an early branching off between primary tumor and metastasis. Liquid biopsies, although initially negative, started to detect an ESR1 E380Q mutation in 2016 with increasing allele frequency until the end of 2017. Transcriptome analysis revealed 721 (193 up, 528 down) genes to be differentially expressed between primary tumor and first relapse. The most significantly down-regulated genes were TFF1 and PGR, indicating resistance to aromatase inhibitor (AI) therapy. The most up-regulated genes included PTHLH, S100P, and SOX2, promoting tumor growth and metastasis. This phylogenetic reconstruction of the life history of a single patient's cancer as well as monitoring tumor progression through liquid biopsies allowed for uncovering the molecular mechanisms leading to initial relapse, metastatic spread, and treatment resistance.

STAT3, the Challenge for Chemotherapeutic and Radiotherapeutic Efficacy

Chemoradiotherapy is one of the most effective and extensively used strategies for cancer treatment. Signal transducer and activator of transcription 3 (STAT3) regulates vital biological processes, such as cell proliferation and cell growth. It is constitutively activated in various cancers and limits the application of chemoradiotherapy. Accumulating evidence suggests that STAT3 regulates resistance to chemotherapy and radiotherapy and thereby impairs therapeutic efficacy by mediating its feedback loop and several target genes. The alternative splicing product STAT3β is often identified as a dominant-negative regulator, but it enhances sensitivity to chemotherapy and offers a new and challenging approach to reverse therapeutic resistance. We focus here on exploring the role of STAT3 in resistance to receptor tyrosine kinase (RTK) inhibitors and radiotherapy, outlining the potential of targeting STAT3 to overcome chemo(radio)resistance for improving clinical outcomes, and evaluating the importance of STAT3β as a potential therapeutic approach to overcomes chemo(radio)resistance. In this review, we discuss some new insights into the effect of STAT3 and its subtype STAT3β on chemoradiotherapy sensitivity, and we explore how these insights influence clinical treatment and drug development for cancer.

The impact of sex on hepatotoxic, inflammatory and proliferative responses in mouse models of liver carcinogenesis

Liver cancer is the third most common cause of cancer-related death but is almost 4-fold more prevalent in men than in women. Increased risk in men may be due in part to elevated chronic inflammation, which is a crucial driving force for many cancers. Male mice also have a greater incidence of liver cancer than females after postnatal exposure to procarcinogens such as 4-aminobiphenyl (ABP) or diethylnitrosamine (DEN), or in mice that transgenically express hepatitis B virus (HBV) proteins. Liver damage, inflammation and proliferation are central to liver cancer development, and previous studies have shown that hepatocellular damage, inflammation and proliferation are acutely elevated to a greater extent in adult male mice than in females after high-dose exposure to DEN. In contrast, postnatal exposure of mice to tumor-inducing doses of either DEN or ABP produces no such acute responses. However, it is not known whether sex differences in responses to postnatal carcinogen exposure or to HBV protein expression may develop over time following sexual maturation. We conducted an extended time course study to compare markers of liver damage, inflammation and proliferation between male and female mice exposed postnatally to 600 nmol ABP or 10 mg/kg DEN, and also in HBV transgenic (HBVTg) mice, over the duration of time that mice are normally maintained for standard liver tumor development protocols. Postnatal exposure to either ABP or DEN produced no evidence of either acute or chronic hepatocyte damage, liver inflammation or proliferation in either male or female mice. In contrast, HBVTg mice showed increased liver damage, inflammation and proliferation with age, but with no observed sex difference. These findings suggest that although chronic liver damage, inflammation and proliferation may be drivers for liver cancer development, they are unlikely to contribute directly to observed sex differences in liver tumor risk.

STAT3 and mutp53 Engage a Positive Feedback Loop Involving HSP90 and the Mevalonate Pathway

Oncosuppressor TP53 and oncogene STAT3 have been shown to engage an interplay in which they negatively influence each other. Conversely, mutant (mut) p53 may sustain STAT3 phosphorylation by displacing SH2 phosphatase while whether STAT3 could influence mutp53 has not been clarified yet. In this study we found that pharmacologic or genetic inhibition of STAT3 in both glioblastoma and pancreatic cancer cells, carrying mutp53 protein, reduced mutp53 expression level by down-regulating chaperone HSP90 as well as molecules belonging to the mevalonate pathway. On the other hand, HSP90 and the mevalonate pathway were involved in sustaining STAT3 phosphorylation mediated by mutp53. In conclusion, this study unveils for the first time that mutp53 can establish with STAT3, similarly to what observed with other oncogenic pathways, a criminal alliance with a crucial role in promoting cancerogenesis.

STAT3 is a key molecule in the oncogenic behavior of diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG) is one of the most lethal childhood brain tumors. This tumor is unique because it is detected exclusively in the ventral pons of patients aged between 6 and 7 years, which suggests a developmental nature of its formation. Signal transducer and activator of transcription 3 (STAT3) is a critical molecule for the differentiation of neural stem cells into astrocytes during neurodevelopment. Additionally, STAT3 is associated with oncogenesis and the epithelial-mesenchymal transition (EMT) in various types of tumor. In recent years, several studies have demonstrated the oncogenic role of STAT3 in high-grade gliomas. However, the role of STAT3 in DIPG at the cellular level remains unknown. To assess the possible association between gliogenesis and DIPG, the expression levels of various molecules participating in the differentiation of neural stem cells were compared between normal brain control tissues and DIPG tissues using open public data. All of the screened genes exhibited significantly increased expression in DIPG tissues compared with normal tissues. As STAT3 expression was the most increased, the effect of STAT3 inhibition in a DIPG cell line was assessed via STAT3 short hairpin (sh)RNA transfection and treatment with AG490, a STAT3 inhibitor. Changes in viability, apoptosis, EMT and radiation therapy efficiency were also evaluated. Downregulation of STAT3 resulted in decreased cyclin D1 expression and cell viability, migration and invasion. Additionally, treatment with STAT3 shRNA or AG490 suppressed the EMT phenotype. Finally, when radiation was administered in combination with STAT3 inhibition, the therapeutic efficiency, assessed by cell viability and DNA damage repair, was increased. The present results suggest that STAT3 is a potential therapeutic target in DIPG, especially when combined with radiation therapy.

Ring-Substituted 1-Hydroxynaphthalene-2-Carboxanilides Inhibit Proliferation and Trigger Mitochondria-Mediated Apoptosis

Ring-substituted 1-hydroxynaphthalene-2-carboxanilides were previously investigated for their antimycobacterial properties. In our study, we have shown their antiproliferative and cell death-inducing effects in cancer cell lines. Cell proliferation and viability were assessed by WST-1 assay and a dye exclusion test, respectively. Cell cycle distribution, phosphatidylserine externalization, levels of reactive oxygen or nitrogen species (RONS), mitochondrial membrane depolarization, and release of cytochrome c were estimated by flow cytometry. Levels of regulatory proteins were determined by Western blotting. Our data suggest that the ability to inhibit the proliferation of THP-1 or MCF-7 cells might be referred to meta- or para-substituted derivatives with electron-withdrawing groups -F, -Br, or -CF₃ at anilide moiety. This effect was accompanied by accumulation of cells in G1 phase. Compound 10 also induced apoptosis in THP-1 cells in association with a loss of mitochondrial membrane potential and production of mitochondrial superoxide. Our study provides a new insight into the action of salicylanilide derivatives, hydroxynaphthalene carboxamides, in cancer cells. Thus, their structure merits further investigation as a model moiety of new small-molecule compounds with potential anticancer properties.

Erchen Plus Huiyanzhuyu Decoction Inhibits the Growth of Laryngeal Carcinoma in a Mouse Model of Phlegm-Coagulation-Blood-Stasis Syndrome via the STAT3/Cyclin D1 Pathway

Erchen plus Huiyanzhuyu decoction (EHD), a Chinese herbal medicine (CHM) formula that consists of Erchen decoction and Huiyanzhuyu decoction, has achieved satisfactory results in the clinic. The main function of EHD is to remove phlegm and blood stasis, and EHD is suitable for phlegm-coagulation-blood-stasis (PCBS) syndrome in laryngeal cancer (LC). In this study, a xenograft mouse model of LC with PCBS syndrome was constructed by feeding a high-fat diet, swimming in ice water, and subcutaneously injecting epinephrine hydrochloride for 2 weeks. Based on the successful Chinese medicine syndrome model, Hep2-luciferase-GFP cells were injected subcutaneously under the armpit of the right upper limb in mice to form tumours. A mouse model of LC with PCBS syndrome was established via heterotopic transplantation. Then, the mice received intragastric administration of different concentrations of EHD daily, and cisplatin (DDP) was intraperitoneally injected every week for 21 days. Tumour fluorescence in mice was measured with a living animal imager on days 7, 14, 21, and 28 during treatment. The results of this experiment confirmed that a mouse model of Chinese medicine syndrome was successfully constructed. Moreover, EHD slowed the growth of xenograft tumours in nude mice; decreased the expression levels of STAT3, p-STAT3, and cyclin D1; and upregulated the expression level of P27. In brief, EHD inhibited laryngeal tumour growth in a xenograft mouse model of PCBS syndrome and regulated the STAT3/cyclin D1 signalling pathway. This study was the first to construct a Chinese medicine xenograft mouse model of LC with PCBS syndrome; in addition, this study clarified that EHD regulated the STAT3/cyclin D1 signalling pathway to inhibit the growth of LC and that EHD may be a promising novel therapeutic compound for the treatment of patients with LC.

SerpinB1 promotes the proliferation of porcine pancreatic stem cells through the STAT3 signaling pathway

Porcine pancreatic stem cells (pPSCs) can be induced to insulin-secreting cells and therefore considered the most promising seeding cells for curing human diabetes in future. However, insufficient pPSCs number is one of the bottleneck problems before its clinical application. SerpinB1 is a serine protease inhibitor in neutrophils and can directly promote the proliferation of β cells. Whether SerpinB1 is involved in pPSC proliferation and differentiation remains unknown. The effects of SerpinB1 on pPSCs proliferation were measured by Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine, qRT-PCR, western blot, and flow cytometry assays. We found that pPSCs did not efficiently reach the S phase when SerpinB1 expression was knocked down with short hairpin RNA (sh-SerpinB1), the expression of Cyclin D1, CDK-2, and PCNA also decreased. Meanwhile, cell viability and proliferation ability were both declined. Further analyses showed that the expression level of phosphorylated STAT3/STAT3was downregulated, along with an upregulation of p53 and p21. We used a two-step induction method to induce pPSCs to insulin-secreting cells and found that SerpinB1 expression in insulin-secreting cells was higher than in pPSCs. Meanwhile, the protein expression level of phosphorylated STAT3/STAT3 was increased while p53 and p21 was decreased in induced insulin-secreting cells in comparison with control cells. The insulin-secreting cells derived from the sh-SerpinB1 cells secreted less insulin and showed poor sensitivity to high glucose than control group. However, the insulin-secreting cells derived from the ov-SerpinB1 cells has a quite contrary tendency. In conclusion, this study demonstrates that SerpinB1 promotes the proliferation of pPSCs through the STAT3 signaling pathway, and SerpinB1 is a key factor for maintaining the viability of pPSCs during the transition to insulin-secreting cells.

MicroRNA-125b exerts antitumor functions in cutaneous squamous cell carcinoma by targeting the STAT3 pathway

Background

MicroRNA-125b (miR-125b) is downregulated in human cutaneous squamous cell carcinoma (CSCC). However, its function in CSCC has yet to be extensively explored. Here, we analyze the relationship between signal transducer and activator of transcription 3 (STAT3) and miR-125b in CSCC.

Methods

Western blotting and quantitative RT-PCR were used to determine the expression of the miR-125b–STAT3 axis in human CSCC tissues and cell lines. The direct regulatory effect of miR-125b on STAT3 expression was assessed using a luciferase reporter gene assay and RNA immunoprecipitation assay. The MTT assay and flow cytometry were used to determine the role of the miR-125b–STAT3 axis in CSCC cell proliferation and apoptosis.

Results

MiR-125b expression levels were significantly lower in CSCC cell lines and tissues than in normal cell lines and tissues. STAT3 was identified as the direct target of miR-125b. Upregulation of miR-125b and downregulation of STAT3 suppressed cell proliferation and promoted cell apoptosis. Cyclin D1 and Bcl2 were identified as the downstream targets of the miR-125–STAT3 axis.

Conclusions

Our findings indicate that miR-125b acts as a tumor suppressor in CSCC by targeting the STAT3 pathway. This observation increases our understanding of the molecular mechanisms of CSCC. Therapies aimed at activating miR-125b or inhibiting STAT3 signaling should be explored as potential treatments for CSCC.

A three-dimensional dementia model reveals spontaneous cell cycle re-entry and a senescence-associated secretory phenotype

A hexanucleotide repeat expansion on chromosome 9 open reading frame 72 (C9orf72) is associated with familial amyotrophic lateral sclerosis (ALS) and a subpopulation of patients with sporadic ALS and frontotemporal dementia. We used inducible pluripotent stem cells from neurotypic and C9orf72+ (C9+) ALS patients to derive neuronal progenitor cells. We demonstrated that C9+ and neurotypic neuronal progenitor cells differentiate into neurons. The C9+ neurons, however, spontaneously re-expressed cyclin D1 after 12 weeks, suggesting cell cycle re-engagement. Gene profiling revealed significant increases in senescence-associated genes in C9+ neurons. Moreover, C9+ neurons expressed high levels of mRNA for CXCL8, a chemokine overexpressed by senescent cells, while media from C9+ neurons contained significant levels of CXCL8, CXCL1, IL13, IP10, CX3CL1, and reactive oxygen species, which are components of the senescence-associated secretory phenotype. Thus, re-engagement of cell cycle-associated proteins and a senescence-associated secretory phenotype could be fundamental components of neuronal dysfunction in ALS and frontotemporal dementia.

Blockade of JAK2 protects mice against hypoxia-induced pulmonary arterial hypertension by repressing pulmonary arterial smooth muscle cell proliferation

Objectives

Hypoxia is an important risk factor for pulmonary arterial remodelling in pulmonary arterial hypertension (PAH), and the Janus kinase 2 (JAK2) is believed to be involved in this process. In the present report, we aimed to investigate the role of JAK2 in vascular smooth muscle cells during the course of PAH.

Methods

Smooth muscle cell (SMC)‐specific Jak2 deficient mice and their littermate controls were subjected to normobaric normoxic or hypoxic (10% O₂) challenges for 28 days to monitor the development of PAH, respectively. To further elucidate the potential mechanisms whereby JAK2 influences pulmonary vascular remodelling, a selective JAK2 inhibitor was applied to pre‐treat human pulmonary arterial smooth muscle cells (HPASMCs) for 1 hour followed by 24‐hour hypoxic exposure.

Results

Mice with hypoxia‐induced PAH were characterized by the altered JAK2/STAT3 activity in pulmonary artery smooth muscle cells. Therefore, induction of Jak2 deficiency in SMCs protected mice from hypoxia‐induced increase of right ventricular systolic pressure (RVSP), right ventricular hypertrophy and pulmonary vascular remodelling. Particularly, loss of Jak2 significantly attenuated chronic hypoxia‐induced PASMC proliferation in the lungs. Similarly, blockade of JAK2 by its inhibitor, TG‐101348, suppressed hypoxia‐induced human PASMC proliferation. Upon hypoxia‐induced activation, JAK2 phosphorylated signal transducer and activator of transcription 3 (STAT3), which then bound to the CCNA2 promoter to transcribe cyclin A2 expression, thereby promoting PASMC proliferation.

Conclusions

Our studies support that JAK2 could be a culprit contributing to the pulmonary vascular remodelling, and therefore, it could be a viable target for prevention and treatment of PAH in clinical settings.