In vivo antitumor efficacy of STAT3 blockade using a transcription factor decoy approach: implications for cancer therapy

Curcumin and its Derivatives Targeting Multiple Signaling Pathways to Elicit Anticancer Activity: A Comprehensive Perspective

The uncontrolled growth and spread of aberrant cells characterize the group of disorders known as cancer. According to GLOBOCAN 2022 analysis of cancer patients in either developed countries or developing countries the main concern cancers are breast cancer, lung cancer, and liver cancer which may rise eventually. Natural substances with dietary origins have gained interest for their low toxicity, anti-inflammatory, and antioxidant effects. The evaluation of dietary natural products as chemopreventive and therapeutic agents, the identification, characterization, and synthesis of their active components, as well as the enhancement of their delivery and bioavailability, have all received significant attention. Thus, the treatment strategy for concerning cancers must be significantly evaluated and may include the use of phytochemicals in daily lifestyle. In the present perspective, we discussed one of the potent phytochemicals, that has been used over the past few decades known as curcumin as a panacea drug of the "Cure-all" therapy concept. In our review firstly we included exhausted data from in vivo and in vitro studies on breast cancer, lung cancer, and liver cancer which act through various cancer-targeting pathways at the molecular level. Now, the second is the active constituent of turmeric known as curcumin and its derivatives are enlisted with their targeted protein in the molecular docking studies, which help the researchers design and synthesize new curcumin derivatives with respective implicated molecular and cellular activity. However, curcumin and its substituted derivatives still need to be investigated with unknown targeting mechanism studies in depth.

The Role of STATs in Ovarian Cancer: Exploring Their Potential for Therapy

Ovarian cancer (OvCa) is a deadly gynecologic malignancy that presents many clinical challenges due to late-stage diagnoses and the development of acquired resistance to standard-of-care treatment protocols. There is an increasing body of evidence suggesting that STATs may play a critical role in OvCa progression, resistance, and disease recurrence, and thus we sought to compile a comprehensive review to summarize the current state of knowledge on the topic. We have examined peer reviewed literature to delineate the role of STATs in both cancer cells and cells within the tumor microenvironment. In addition to summarizing the current knowledge of STAT biology in OvCa, we have also examined the capacity of small molecule inhibitor development to target specific STATs and progress toward clinical applications. From our research, the best studied and targeted factors are STAT3 and STAT5, which has resulted in the development of several inhibitors that are under current evaluation in clinical trials. There remain gaps in understanding the role of STAT1, STAT2, STAT4, and STAT6, due to limited reports in the current literature; as such, further studies to establish their implications in OvCa are necessitated. Moreover, due to the deficiency in our understanding of these STATs, selective inhibitors also remain elusive, and therefore present opportunities for discovery.

Investigating regulated signaling pathways in therapeutic targeting of non-small cell lung carcinoma

Non-small cell lung carcinoma (NSCLC) is the most common malignancy worldwide. The signaling cascades are stimulated via genetic modifications in upstream signaling molecules, which affect apoptotic, proliferative, and differentiation pathways. Dysregulation of these signaling cascades causes cancer-initiating cell proliferation, cancer development, and drug resistance. Numerous efforts in the treatment of NSCLC have been undertaken in the past few decades, enhancing our understanding of the mechanisms of cancer development and moving forward to develop effective therapeutic approaches. Modifications of transcription factors and connected pathways are utilized to develop new treatment options for NSCLC. Developing designed inhibitors targeting specific cellular signaling pathways in tumor progression has been recommended for the therapeutic management of NSCLC. This comprehensive review provided deeper mechanistic insights into the molecular mechanism of action of various signaling molecules and their targeting in the clinical management of NSCLC.

Transcription Factors and Cancer: Approaches to Targeting

ABSTRACT

Cancer is defined by the presence of uncontrollable cell growth, whereby improper proliferative signaling has overcome regulation by cellular mechanisms. Transcription factors are uniquely situated at the helm of signaling, merging extracellular stimuli with intracellular responses. Therefore, this class of proteins plays a pivotal role in coordinating the correct gene expression levels for maintaining normal cellular functions. Dysregulation of transcription factor activity unsurprisingly drives tumorigenesis and oncogenic transformation. Although this imparts considerable therapeutic potential to targeting transcription factors, their lack of enzymatic activity renders intervention challenging and has contributed to a sense that transcription factors are "undruggable." Yet, enduring efforts to elucidate strategies for targeting transcription factors as well as a deeper understanding of their interactions with binding partners have led to advancements that are emerging to counter this narrative. Here, we highlight some of these approaches, focusing primarily on therapeutics that have advanced to the clinic.

Disrupting autorepression circuitry generates "open-loop lethality" to yield escape-resistant antiviral agents

Across biological scales, gene-regulatory networks employ autorepression (negative feedback) to maintain homeostasis and minimize failure from aberrant expression. Here, we present a proof of concept that disrupting transcriptional negative feedback dysregulates viral gene expression to therapeutically inhibit replication and confers a high evolutionary barrier to resistance. We find that nucleic-acid decoys mimicking cis-regulatory sites act as "feedback disruptors," break homeostasis, and increase viral transcription factors to cytotoxic levels (termed "open-loop lethality"). Feedback disruptors against herpesviruses reduced viral replication >2-logs without activating innate immunity, showed sub-nM IC50, synergized with standard-of-care antivirals, and inhibited virus replication in mice. In contrast to approved antivirals where resistance rapidly emerged, no feedback-disruptor escape mutants evolved in long-term cultures. For SARS-CoV-2, disruption of a putative feedback circuit also generated open-loop lethality, reducing viral titers by >1-log. These results demonstrate that generating open-loop lethality, via negative-feedback disruption, may yield a class of antimicrobials with a high genetic barrier to resistance.

STAT3 pathway in cancers: Past, present, and future

Signal transducer and activator of transcription 3 (STAT3), a member of the STAT family, discovered in the cytoplasm of almost all types of mammalian cells, plays a significant role in biological functions. The duration of STAT3 activation in normal tissues is a transient event and is strictly regulated. However, in cancer tissues, STAT3 is activated in an aberrant manner and is induced by certain cytokines. The continuous activation of STAT3 regulates the expression of downstream proteins associated with the formation, progression, and metastasis of cancers. Thus, elucidating the mechanisms of STAT3 regulation and designing inhibitors targeting the STAT3 pathway are considered promising strategies for cancer treatment. This review aims to introduce the history, research advances, and prospects concerning the STAT3 pathway in cancer. We review the mechanisms of STAT3 pathway regulation and the consequent cancer hallmarks associated with tumor biology that are induced by the STAT3 pathway. Moreover, we summarize the emerging development of inhibitors that target the STAT3 pathway and novel drug delivery systems for delivering these inhibitors. The barriers against targeting the STAT3 pathway, the focus of future research on promising targets in the STAT3 pathway, and our perspective on the overall utility of STAT3 pathway inhibitors in cancer treatment are also discussed.

Insights into the role of STAT3 in intrahepatic cholangiocarcinoma (Review)

Intrahepatic cholangiocarcinoma (ICC) is a primary malignant liver tumour whose incidence is second only to that of hepatocellular carcinoma. ICC is a highly heterogeneous disease arising from neoplastic transformation of intrahepatic biliary epithelial cells (cholangiocytes), and it is characterized by a very poor prognosis. Signal transducer and activator of transcription 3 (STAT3) is an important oncogene that is widely expressed in numerous cancers. STAT3 is a candidate target for the treatment of ICC. However, studies on STAT3 and the occurrence and development of ICC require improvements. Therefore, the present review summarized the mechanism of STAT3 in ICC and provided a theoretical basis for STAT3 to become an effective target for determining the prognosis and treatment of ICC.

Microbial Colonization and Inflammation as Potential Contributors to the Lack of Therapeutic Success in Oral Squamous Cell Carcinoma

This review discusses the microenvironment of evolving and established conventional oral squamous cell carcinoma, by far the most common oral cancer. The focus of this paper is mainly on the more recent data that describe the role of microorganisms, host-microbial interactions, and in particular, the contributions of cell-surface toll-like receptors on immune system cells and on normal and malignant epithelial cells to their functions that support carcinogenesis. Because carcinomas arising at various host surfaces share much in common, additional information available from studies of other carcinomas is included in the discussion. Accumulating evidence reveals the complex toll-like receptor-mediated tumor-supporting input into many aspects of carcinogenesis via malignant cells, stromal immune cells and non-immune cells, complicating the search for effective treatments.

Chemotherapeutic Drug-Regulated Cytokines Might Influence Therapeutic Efficacy in HCC

Hepatocellular carcinoma (HCC), the most common type of liver cancer, is the second leading cause of cancer-related mortality worldwide. Processes involved in HCC progression and development, including cell transformation, proliferation, metastasis, and angiogenesis, are inflammation-associated carcinogenic processes because most cases of HCC develop from chronic liver damage and inflammation. Inflammation has been demonstrated to be a crucial factor inducing tumor development in various cancers, including HCC. Cytokines play critical roles in inflammation to accelerate tumor invasion and metastasis by mediating the migration of immune cells into damaged tissues in response to proinflammatory stimuli. Currently, surgical resection followed by chemotherapy is the most common curative therapeutic regimen for HCC. However, after chemotherapy, drug resistance is clearly observed, and cytokine secretion is dysregulated. Various chemotherapeutic agents, including cisplatin, etoposide, and 5-fluorouracil, demonstrate even lower efficacy in HCC than in other cancers. Tumor resistance to chemotherapeutic drugs is the key limitation of curative treatment and is responsible for treatment failure and recurrence, thus limiting the ability to treat patients with advanced HCC. Therefore, the capability to counteract drug resistance would be a major clinical advancement. In this review, we provide an overview of links between chemotherapeutic agents and inflammatory cytokine secretion in HCC. These links might provide insight into overcoming inflammatory reactions and cytokine secretion, ultimately counteracting chemotherapeutic resistance.

Current and Emerging Molecular Therapies for Head and Neck Squamous Cell Carcinoma

Head and neck cancer affects nearly 750,000 patients, with more than 300,000 deaths annually. Advances in first line surgical treatment have improved survival rates marginally particularly in developed countries, however survival rates for aggressive locally advanced head and neck cancer are still poor. Recurrent and metastatic disease remains a significant problem for patients and the health system. As our knowledge of the genomic landscape of the head and neck cancers continues to expand, there are promising developments occurring in molecular therapies available for advanced or recalcitrant disease. The concept of precision medicine is underpinned by our ability to accurately sequence tumour samples to best understand individual patient genomic variations and to tailor targeted therapy for them based on such molecular profiling. Not only is their purported response to therapy a factor of their genomic variation, but so is their inclusion in biomarker-driven personalised medicine therapeutic trials. With the ever-expanding number of molecular druggable targets explored through advances in next generation sequencing, the number of clinical trials assessing these targets has significantly increased over recent years. Although some trials are focussed on first-line therapeutic approaches, a greater majority are focussed on locally advanced, recurrent or metastatic disease. Similarly, although single agent monotherapy has been found effective in some cases, it is the combination of drugs targeting different signalling pathways that seem to be more beneficial to patients. This paper outlines current and emerging molecular therapies for head and neck cancer, and updates readers on outcomes of the most pertinent clinical trials in this area while also summarising ongoing efforts to bring more molecular therapies into clinical practice.

An update on investigational therapies that target STAT3 for the treatment of cancer

INTRODUCTION

Signal transducer and activator of transcription 3 (STAT3) is involved in cancer initiation and resistance to chemo-radiation therapies and targeted agents. The role of STAT3 in inflammation and immunity together with its involvement in a variety of diseases including genitourinary, gastrointestinal, lung, ovarian and brain tumors makes STAT3 an ideal candidate for therapeutic strategies.

AREAS COVERED

The authors provided an overview on STAT3 inhibitors and examined the most recent results obtained by these agents in cancer patients. The authors discussed the results published since 2015 and the ongoing clinical trials on anti-STAT3 agents in cancer patients. The authors also provide our opinion on the future perspectives of this therapeutic approach in this context. The manuscript includes information from trial databases and scientific literature.

EXPERT OPINION

Future challenges include the development of non-peptide small-molecule inhibitors of STAT3 designed to directly inhibit STAT3 activity. In addition, inhibitors of STAT3/STAT3 nuclear translocation or DNA binding activity are also emerging as novel promising therapeutic approaches A better comprehension of the role of STAT3 in modulating immune response together with advances in understanding the mechanisms of STAT3-induced chemo and/or radio-resistance will also help the design of combined strategies in cancer patients.

Targeting the JAK/STAT Signaling Pathway Using Phytocompounds for Cancer Prevention and Therapy

Cancer is a prevalent cause of mortality around the world. Aberrated activation of Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway promotes tumorigenesis. Natural agents, including phytochemicals, exhibit potent anticancer activities via various mechanisms. However, the therapeutic potency of phytoconstituents as inhibitors of JAK/STAT signaling against cancer has only come into focus in recent days. The current review highlights phytochemicals that can suppress the JAK/STAT pathway in order to impede cancer cell growth. Various databases, such as PubMed, ScienceDirect, Web of Science, SpringerLink, Scopus, and Google Scholar, were searched using relevant keywords. Once the authors were in agreement regarding the suitability of a study, a full-length form of the relevant article was obtained, and the information was gathered and cited. All the complete articles that were incorporated after the literature collection rejection criteria were applied were perused in-depth and material was extracted based on the importance, relevance, and advancement of the apprehending of the JAK/STAT pathway and their relation to phytochemicals. Based on the critical and comprehensive analysis of literature presented in this review, phytochemicals from diverse plant origins exert therapeutic and cancer preventive effects, at least in part, through regulation of the JAK/STAT pathway. Nevertheless, more preclinical and clinical research is necessary to completely comprehend the capability of modulating JAK/STAT signaling to achieve efficient cancer control and treatment.

STAT3 signaling in ovarian cancer: a potential therapeutic target

Accumulating evidence has shown that Signal Transducer and Activator of Transcription 3 (STAT3) is thought to be a promising target for cancer therapy as STAT3 is frequently overexpressed in a wide range of cancer cells as well as clinical specimens, promoting tumor progression. It is widely accepted that STAT3 regulates a variety of cellular processes, such as tumor cell growth, survival, invasion, cancer stem cell-like characteristic, angiogenesis and drug-resistance. In this review, we focus on the role of STAT3 in tumorigenesis in ovarian cancer and discuss the existing inhibitors of STAT3 signaling that can be promisingly developed as the strategies for ovarian cancer therapy.

Targeting STAT3 in Cancer with Nucleotide Therapeutics

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in promoting the proliferation and survival of tumor cells. As a ubiquitously-expressed transcription factor, STAT3 has commonly been considered an "undruggable" target for therapy; thus, much research has focused on targeting upstream pathways to reduce the expression or phosphorylation/activation of STAT3 in tumor cells. Recently, however, novel approaches have been developed to directly inhibit STAT3 in human cancers, in the hope of reducing the survival and proliferation of tumor cells. Several of these agents are nucleic acid-based, including the antisense molecule AZD9150, CpG-coupled STAT3 siRNA, G-quartet oligodeoxynucleotides (GQ-ODNs), and STAT3 decoys. While the AZD9150 and CpG-STAT3 siRNA interfere with STAT3 expression, STAT3 decoys and GQ-ODNs target constitutively activated STAT3 and modulate its ability to bind to target genes. Both STAT3 decoy and AZD9150 have advanced to clinical testing in humans. Here we will review the current understanding of the structures, mechanisms, and potential clinical utilities of the nucleic acid-based STAT3 inhibitors.

Natural Sesquiterpene Lactones Enhance Chemosensitivity of Tumor Cells through Redox Regulation of STAT3 Signaling

STAT3 is a nuclear transcription factor that regulates genes involved in cell cycle, cell survival, and immune response. Although STAT3 activation drives cells to physiological response, its deregulation is often associated with the development and progression of many solid and hematological tumors as well as with drug resistance. STAT3 is a redox-sensitive protein, and its activation state is related to intracellular GSH levels. Under oxidative conditions, STAT3 activity is regulated by S-glutathionylation, a reversible posttranslational modification of cysteine residues. Compounds able to suppress STAT3 activation and, on the other hand, to modulate intracellular redox homeostasis may potentially improve cancer treatment outcome. Nowadays, about 35% of commercial drugs are natural compounds that derive from plant extracts used in phytotherapy and traditional medicine. Sesquiterpene lactones are an interesting chemical group of plant-derived compounds often employed in traditional medicine against inflammation and cancer. This review focuses on sesquiterpene lactones able to downmodulate STAT3 signaling leading to an antitumor effect and correlates the anti-STAT3 activity with their ability to decrease GSH levels in cancer cells. These properties make them lead compounds for the development of a new therapeutic strategy for cancer treatment.

STAT3 in Breast Cancer Onset and Progression: A Matter of Time and Context

Signal transducer and activator of transcription 3 (STAT3) is responsible for mediating the transcriptional programs downstream of several cytokine, growth factor, and oncogenic stimuli. Its expression and activity are consistently linked to cellular transformation, as well as tumor initiation and progression. Due to this central role, STAT3 is widely considered a good target for anti-cancer therapy; however, the success of these approaches has been, so far, very limited. Notably, on one side, STAT3 is aberrantly active in many breast cancers, on the other, at the physiological level, it is the main mediator of epithelial cell death during post-lactation mammary-gland involution, thus strongly suggesting that its biological functions are highly context-specific. One of the most peculiar features of STAT3 is that it can act both in cell-autonomous and non-cell-autonomous manners, simultaneously modulating the phenotypes of the tumor cells and their microenvironment. Here, we focus on the role of STAT3 in breast cancer progression, discussing the potential contrasting roles of STAT3 activation in the establishment of locally recurrent and distant metastatic disease. Based on the most recent literature, depending on the tumor cell type, the local microenvironment status, and the stage of the disease, either STAT3 activation or inactivation can support disease progression. Accordingly, cancer cells dynamically exploit STAT3 activity to carry out transcriptional programs somehow contrasting and complementary, such as supporting survival and growth, dormancy and awakening, stem cell-like features, and inflammation, immune response, and immune evasion. As a consequence, to achieve clinical efficacy, the conception and testing of anti-STAT3 targeted therapies will need a very careful evaluation of these opposing roles and of the most appropriate tumor context, disease stage and patient population to treat.

Biochemical Properties of a Decoy Oligodeoxynucleotide Inhibitor of STAT3 Transcription Factor

Cyclic STAT3 decoy (CS3D) is a second-generation, double-stranded oligodeoxynucleotide (ODN) that mimics a genomic response element for signal transducer and activator of transcription 3 (STAT3), an oncogenic transcription factor. CS3D competitively inhibits STAT3 binding to target gene promoters, resulting in decreased expression of proteins that promote cellular proliferation and survival. Previous studies have demonstrated antitumor activity of CS3D in preclinical models of solid tumors. However, prior to entering human clinical trials, the efficiency of generating the CS3D molecule and its stability in biological fluids should be determined. CS3D is synthesized as a single-stranded ODN and must have its free ends ligated to generate the final cyclic form. In this study, we report a ligation efficiency of nearly 95 percent. The ligated CS3D demonstrated a half-life of 7.9 h in human serum, indicating adequate stability for intravenous delivery. These results provide requisite biochemical characterization of CS3D that will inform upcoming clinical trials.

Targeting the IL-6/JAK/STAT3 signalling axis in cancer

The IL-6/JAK/STAT3 pathway is aberrantly hyperactivated in many types of cancer, and such hyperactivation is generally associated with a poor clinical prognosis. In the tumour microenvironment, IL-6/JAK/STAT3 signalling acts to drive the proliferation, survival, invasiveness, and metastasis of tumour cells, while strongly suppressing the antitumour immune response. Thus, treatments that target the IL-6/JAK/STAT3 pathway in patients with cancer are poised to provide therapeutic benefit by directly inhibiting tumour cell growth and by stimulating antitumour immunity. Agents targeting IL-6, the IL-6 receptor, or JAKs have already received FDA approval for the treatment of inflammatory conditions or myeloproliferative neoplasms and for the management of certain adverse effects of chimeric antigen receptor T cells, and are being further evaluated in patients with haematopoietic malignancies and in those with solid tumours. Novel inhibitors of the IL-6/JAK/STAT3 pathway, including STAT3-selective inhibitors, are currently in development. Herein, we review the role of IL-6/JAK/STAT3 signalling in the tumour microenvironment and the status of preclinical and clinical investigations of agents targeting this pathway. We also discuss the potential of combining IL-6/JAK/STAT3 inhibitors with currently approved therapeutic agents directed against immune-checkpoint inhibitors.

The relationship between total and phosphorylated STAT1 and STAT3 tumour cell expression, components of tumour microenvironment and survival in patients with invasive ductal breast cancer

The aim of the present study was to examine the relationship between tumour cell expression of total and phosphorylated STAT1 (ph-STAT1) and STAT3 (ph-STAT-3), components of tumour microenvironment and survival in patients with invasive ductal breast cancer.

Immunohistochemical analysis of total and ph-STAT1, and STAT3 were performed on tissue microarray of 384 breast cancer specimens. Tumour cell expression of STAT1 and STAT3 at both cytoplasmic and nuclear locations were combined and identified as STAT1/STAT3 tumour cell expression. These results were related to cancer specific survival (CSS) and phenotypic features of the tumour and the host.

High ph-STAT1 and ph-STAT3 tumour cell expression were associated with increased ER (both P≤0.001) and PR (both P <0.05), reduced tumour grade (P=0.015 and P<0.001 respectively) and necrosis (both P=0.001). Ph-STAT1 was associated with increased general inflammatory infiltrate (P=0.007) and ph-STAT3 was associated with lower CD4+ infiltration (P=0.024). In multivariate survival analysis, only high ph-STAT3 tumour cell expression was a predictor of improved CSS (P=0.010) independent of other tumour and host-based factors.

STAT1 and STAT3 tumour cell expression appeared to be an important determinant of favourable outcome in patients with invasive ductal breast cancer. The present results suggest that STAT1 and STAT3 may affect disease outcome through direct impact on tumour cells, counteracting aggressive tumour features, as well as interaction with the surrounding microenvironment.

Dual radiosensitization and anti-STAT3 anti-proliferative strategy based on delivery of gold nanoparticle - oligonucleotide nanoconstructs to head and neck cancer cells

Constitutively activated signal transducer and activator of transcription 3 (STAT3) factor is an important therapeutic target in head and neck cancer (HNC). Despite early promising results, a reliable systemic delivery system for STAT3- targeted oligonucleotide (ODN) drugs is still needed for future clinical translation of anti-STAT3 therapies. We engineered and tested a novel ODN duplex/gold nanoparticle (AuNP)-based system carrying a therapeutic STAT3 decoy (STAT3d) payload. This strategy is two-pronged because of the additive STAT3 antagonism and radiosensitizing properties of AuNP. The specificity to head and neck cancer cell surface was imparted by using a nucleolin aptamer (NUAP) that was linked to AuNP for taking the advantage of an aberrant presentation of a nuclear protein nucleolin on the cell surface. STAT3d and nucleolin aptamer constructs were independently linked to AuNPs via Au-S bonds. The synthesized AuNP constructs (AuNP-NUAP-STAT3d) exhibited internalization in cells that was quantified by using radiolabeled STAT3d. AuNP-NUAP-STAT3d showed radiosensitizing effect in human HNC FaDu cell culture experiments that resulted in an increase of cell DNA damage as determined by measuring γ-H2AX phosphorylation levels by flow cytometry. The radiosensitization study also demonstrated that AuNP-NUAP-STAT3d as well as STAT3d alone resulted in the efficient inhibition of A431 cell proliferation. While FaDu cells did not show instant proliferation inhibition after incubating with AuNP-NUAP-STAT3d, the cell DNA damage in these cells showed nearly a 50% increase in AuNP-NUAP-STAT3d group after treating with radiation. Compared with anti-EGFR humanized antibody (Cetuximab), AuNP-NUAP-STAT3d system had an overall stronger radiosensitization effect in both A431 and FaDu cells.

MicroRNA-519a inhibits the proliferation and promotes the apoptosis of ovarian cancer cells through targeting signal transducer and activator of transcription 3

Ovarian cancer is a highly prevalent cancer among women. Recent studies have indicated that microRNAs (miRs) may serve important roles in the pathogenesis of ovarian cancer. miR-519a was observed to be downregulated in tissue samples of patients with ovarian cancer; however, its role in ovarian cancer requires further investigation. The aim of the present study was to examine the role of miR-519a in the pathogenesis of ovarian cancer and determine its direct target. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was performed to examine the expression of miR-519a in 20 patients ovarian cancer and 20 normal ovarian tissue samples. Subsequently, SKOV3 cells were cultured and transfected with miR-519a mimics, while MTT and Annexin V assays were performed to investigate the role of miR-519a in the proliferation and apoptosis of SKOV3 cells. In addition, RT-qPCR and western blotting were used to determine the expression levels of miR-519a, signal transducer and activator of transcription 3 (STAT3), myeloid cell leukemia 1 (Mcl-1) and B-cell lymphoma-extra large (Bcl-xl) in untransfected and miR-519a mimic-transfected SKOV3 cells. Dual-luciferase reporter assay was also performed to confirm whether STAT3 was a direct target of miR-519a. The results revealed that miR-519a was significantly downregulated in tissue samples of patients with ovarian cancer as compared with the normal ovarian tissues. Furthermore, transient overexpression of miR-519a inhibited the proliferation and promoted the apoptosis of SKOV3 cells, as well as decreased the mRNA and protein expression levels of STAT3, Mcl-1 and Bcl-xl. Finally, dual-luciferase reporter assay confirmed that STAT3 was a direct target of miR-519a. In conclusion, the present study proved for the first time that miR-519a functions as a tumor suppressor by targeting STAT3 in ovarian cancer, suggesting that miR-519a may be a potential biomarker for the diagnosis and treatment of ovarian cancer.

Simultaneous targeted inhibition of Sox2-Oct4 transcription factors using decoy oligodeoxynucleotides to repress stemness properties in mouse embryonic stem cells

Transcriptional master regulators like Sox2 and Oct4, which are expressed in various human tumors, have been shown to cause tumor growth promotion as well as epithelial dysplasia by means of interfering with progenitor cell differentiation. In order to investigate the potential of Sox2-Oct4 transcription factor decoy (TFD) strategy for differentiation therapy, mouse embryonic stem cells (mESCs) were used in this study as a model of cancer stem cells (CSCs). Sox2-Oct4 complex decoy ODNs (cd-ODNs) were designed according to their elements in the promoter region of Sox2 gene. DNA-protein interactions between decoy ODNs and their corresponding proteins were examined by electrophoretic mobility shift assay (EMSA). Then, decoy and scrambled ODNs were transfected into mESCs with lipofectamine under 2 inhibitors (2i) conditions. Fluorescence and confocal microscopy, cell viability, cell cycle and apoptosis analysis, alkaline phosphatase, embryoid body formation assay, and real-time PCR were used to conduct further investigations. EMSA data showed that Sox2-Oct4 decoy ODNs bound specifically to their recombinant proteins. The results revealed that the synthesized complex decoy can concomitantly target Sox2 and Oct4, which subsequently represses the stemness properties of mESCs compared to controls through decreasing cell viability, arresting cell cycle in G₀ /G₁ phases, inducing apoptosis, and modulating differentiation in mESCs despite the presence of 2i/LIF in cell culture. While cd-ODN strategy seems to offer great promise for cancer therapy, further studies are still required to put this powerful investigative tool in practice for a wide range of human cancers.

STAT3 blockade enhances the efficacy of conventional chemotherapeutic agents by eradicating head neck stemloid cancer cell

Signaling transducer and activator 3 (STAT3) and cancer stem cells (CSCs) have garnered huge attention as a therapeutic focus, based on evidence that they may represent an etiologic root of tumor initiation and radio-chemoresistance. Here, we investigated the high phosphorylation status of STAT3 (p-STAT3) and its correlation with self-renewal markers in head neck squamous cell carcinoma (HNSCC). Over-expression of p-STAT3 was found to have increased in post chemotherapy HNSCC tissue. We showed that blockade of p-STAT3 eliminated both bulk tumor and side population (SP) cells with characteristics of CSCs in vitro. Inhibition of p-STAT3 using small molecule S3I-201 significantly delayed tumorigenesis of spontaneous HNSCC in mice. Combining blockade of p-STAT3 with cytotoxic drugs cisplatin, docetaxel, 5-fluorouracil (TPF) enhanced the antitumor effect in vitro and in vivo with decreased tumor sphere formation and SP cells. Taken together, our results advocate blockade of p-STAT3 in combination with conventional chemotherapeutic drugs enhance efficacy by improving CSCs eradication in HNSCC.

STAT3 as a Chemoprevention Target in Carcinogen-Induced Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a frequently fatal disease due, in large part, to a high rate of second primary tumor (SPT) formation. The 4-nitroquinoline 1-oxide (4-NQO) mouse model of oral carcinogenesis provides a robust system in which to study chemopreventive agents in the context of chemically induced HNSCC tumors. STAT3 is a potent oncogene that is hyperactivated by tyrosine phosphorylation early in HNSCC carcinogenesis and is a rational therapeutic target. We recently reported that loss-of-function of the STAT3 phosphatase PTPRT promotes STAT3 activation in HNSCC tumors and preclinical models and may serve as a predictive biomarker of response to STAT3 inhibitors, including the small-molecule Stattic. We therefore investigated the hypothesis that Ptprt-knockout (KO) mice would be more susceptible to 4-NQO-induced oral carcinogenesis and more sensitive to Stattic-mediated chemoprevention compared with wild-type (WT) mice. Herein, we demonstrate that Ptprt WT and KO mice develop similar spectra of HNSCC disease severity upon 12 weeks of 4-NQO administration, with no apparent effect of Ptprt genotype on carcinogenesis or treatment outcome. Targeting of STAT3 with Stattic resulted in a chemopreventive effect against 4-NQO-induced oral cancer (P = 0.0402). While these results do not support a central role for PTPRT in 4-NQO-induced HNSCC carcinogenesis, further investigation of STAT3 as a chemoprevention target in this cancer is warranted. Cancer Prev Res; 9(8); 657-63. ©2016 AACR.

SUMOylation and SENP3 regulate STAT3 activation in head and neck cancer

Hyperphosphorylation of signal transducer and activator of transcription 3 (STAT3) has been found in various types of human cancers, including head and neck cancer (HNC). Although smoking is critical in the development and progression of HNC, how tobacco components activate STAT3 is unclear. We demonstrated that exposure of HNC cell lines to a tobacco extract induced a rapid Y705 phosphorylation of STAT3 and a rapid increase in the SUMO protease SENP3 that depended on a simultaneous increase in reactive oxygen species. We identified that SUMOylation at the lysine 451 site facilitated STAT3 binding to the phosphatase TC45 through an SUMO-interacting motif of TC45. SENP3 could thus enhance STAT3 phosphorylation by de-conjugating the SUMO2/3 modification of STAT3. Knocking-down of SENP3 greatly impaired basal and induced STAT3 phosphorylation by tobacco extract or interleukin 6. A correlation between SENP3 protein levels and STAT3 Y705 phosphorylation levels in human laryngeal carcinoma specimens was found, which was more significant in the specimens derived from the smoker patients and with poor clinicopathological parameters. Our data identified SUMOylation as a previously undescribed post-translational modification of STAT3 and SENP3 as a critical positive modulator of tobacco- or cytokine-induced STAT3 activation. These findings provide novel insights into the hyperphosphorylation of STAT3 in development of HNC.

Applying Small Molecule Signal Transducer and Activator of Transcription-3 (STAT3) Protein Inhibitors as Pancreatic Cancer Therapeutics

Constitutively activated STAT3 protein has been found to be a key regulator of pancreatic cancer and a target for molecular therapeutic intervention. In this study, PG-S3-001, a small molecule derived from the SH-4-54 class of STAT3 inhibitors, was found to inhibit patient-derived pancreatic cancer cell proliferation in vitro and in vivo in the low micromolar range. PG-S3-001 binds the STAT3 protein potently, Kd = 324 nmol/L by surface plasmon resonance, and showed no effect in a kinome screen (>100 cancer-relevant kinases). In vitro studies demonstrated potent cell killing as well as inhibition of STAT3 activation in pancreatic cancer cells. To better model the tumor and its microenvironment, we utilized three-dimensional (3D) cultures of patient-derived pancreatic cancer cells in the absence and presence of cancer-associated fibroblasts (CAF). In this coculture model, inhibition of tumor growth is maintained following STAT3 inhibition in the presence of CAFs. Confocal microscopy was used to verify tumor cell death following treatment of 3D cocultures with PG-S3-001. The 3D model was predictive of in vivo efficacy as significant tumor growth inhibition was observed upon administration of PG-S3-001. These studies showed that the inhibition of STAT3 was able to impact the survival of tumor cells in a relevant 3D model, as well as in a xenograft model using patient-derived cells. Mol Cancer Ther; 15(5); 794-805. ©2016 AACR.

Prioritization schema for immunotherapy clinical trials in glioblastoma

BACKGROUND

Emerging immunotherapeutic strategies for the treatment of glioblastoma (GBM) such as dendritic cell (DC) vaccines, heat shock proteins, peptide vaccines, and adoptive T-cell therapeutics, to name a few, have transitioned from the bench to clinical trials. With upcoming strategies and developing therapeutics, it is challenging to critically evaluate the practical, clinical potential of individual approaches and to advise patients on the most promising clinical trials.

METHODS

The authors propose a system to prioritize such therapies in an organized and data-driven fashion. This schema is based on four categories of factors: antigenic target robustness, immune-activation and -effector responses, preclinical vetting, and early evidence of clinical response. Each of these categories is subdivided to focus on the most salient elements for developing a successful immunotherapeutic approach for GBM, and a numerical score is generated.

RESULTS

The Score Card reveals therapeutics that have the most robust data to support their use, provides a reference prioritization score, and can be applied in a reiterative fashion with emerging data.

CONCLUSIONS

The authors hope that this schema will give physicians an evidence-based and rational framework to make the best referral decisions to better guide and serve this patient population.

The STAT3 pathway as a therapeutic target in head and neck cancer: Barriers and innovations

Proteins of the signal transducer and activator of transcription (STAT) family mediate cellular responses to cytokines and growth factors. Aberrant regulation of the STAT3 oncogene contributes to tumor formation and progression in many cancers, including head and neck squamous cell carcinoma (HNSCC), where hyperactivation of STAT3 is implicated in both treatment resistance and immune escape. There are no oncogenic gain-of-function mutations in HNSCC. Rather, aberrant STAT3 signaling is primarily driven by upstream growth factor receptors, such as Janus kinase (JAK) and epidermal growth factor receptor (EGFR). Moreover, genomic silencing of select protein tyrosine phosphatase receptors (PTPRs), tumor suppressors that dephosphorylate STAT3, may lead to prolonged phosphorylation and activation of STAT3. This review will summarize current knowledge of the STAT3 pathway and its contribution to HNSCC growth, survival, and resistance to standard therapies, and discuss STAT3-targeting agents in various phases of clinical development.

Cell-cell and cell-matrix adhesion in survival and metastasis: Stat3 versus Akt

Both cell-cell and cell-matrix adhesion are important for epithelial cell differentiation and function. Classical cadherins mediate cell to cell interactions and are potent activators of the signal transducer and activator of transcription (Stat3), thereby offering survival signaling. While the epithelial (E)-cadherin is required for cells to remain tightly associated within differentiated epithelial tissues, cadherin-11 promotes invasion and metastasis, preferentially to the bone. Cell adhesion to the extracellular matrix is mediated through the integrin receptors that bind to the focal adhesion kinase (FAK)/Src complex, thus activating downstream effectors such as Ras/Erk1/2 and PI3k/Akt, but not Stat3. Therefore, at high densities of cultured cells or in epithelial tissues, co-ordinate activation of the complementary cadherin/Stat3 and integrin/FAK pathways can greatly enhance survival and growth of tumor cells. In neoplastically transformed cells on the other hand, a variety of oncogenes including activated Src or receptor tyrosine kinases, activate both pathways. Still, most single-agent therapies directed against these signaling pathways have proven disappointing in the clinic. Combined targeting of the Src/FAK and Stat3 pathways with inhibitory drugs would be expected to have greater efficacy in inhibiting tumor cell survival, and enhancing sensitivity to conventional cytotoxic drugs for treatment of metastatic disease.

A STAT inhibitor patent review: progress since 2011

INTRODUCTION

The clinical utility of effective direct STAT inhibitors, particularly STAT3 and STAT5, for treating cancer and other diseases is well studied and known.

AREAS COVERED

This review will highlight the STAT inhibitor patent literature from 2011 to 2015 inclusive. Emphasis will be placed on inhibitors of the STAT3, STAT5a/b, and STAT1 proteins for cancer treatment. The review will, where suitably investigated, describe the mode and the site of inhibition, list indications that were evaluated, and rank the inhibitor's relative potency among compounds in the same class. The reader will gain an understanding of the diverse set of approaches, used both in academia and industry, to target STAT proteins.

EXPERT OPINION

There is still much work to be done to directly target the STAT3 and STAT5 proteins. As yet, there is still no direct STAT3 inhibitor in the clinic. While the SH2 domain remains a popular target for therapeutic intervention, the DNA-binding domain and N-terminal region are now attracting attention as possible sites for inhibition. Multiple putative STAT3 and STAT5 inhibitors have now been patented across a broad spectrum of chemotypes, each with their own advantages and limitations.

The JAK/STAT signaling cascade in gastric carcinoma (Review)

Gastric carcinoma remains one of the most prevalent forms of cancer worldwide, despite the decline in incidence rates, increased awareness of the disease and advancement in treatment strategies. Helicobacter pylori infection, dietary factors, lifestyle influences and various genetic aberrations have been shown to contribute to the development and progression of gastric cancer. Recent studies on the genomic landscape of gastric adenocarcinoma have identified several key signaling molecules, including epidermal growth factor receptor family (ErbB) members, vascular endothelial growth factor receptor family (VEGFR) members and PI3K/Akt/mTOR pathway components, that have been implicated in the molecular pathogenesis of gastric cancers. However, clinical trials with compounds that target these molecules have failed to show a significant improvement in overall survival rates when supplemented with conventional therapies. Therefore, it is essential to identify effective prognostic and/or diagnostic biomarkers and develop molecular targeted therapies. The JAK/STAT cascade is a principal signal transduction pathway in cytokine and growth factor signaling, regulating various cellular processes such as cell proliferation, differentiation, migration and survival. Numerous in vivo and in vitro studies have shown that dysregulated JAK/STAT signaling is a driving force in the pathogenesis of various solid cancers as well as hematopoietic malignancies. Hence, a large number of preclinical and clinical studies of drugs targeting this pathway are currently underway. Notably, aberrant JAK/STAT signaling has also been implicated in gastric cancers. In this review, we focus on the ongoing research on the JAK/STAT cascade in gastric carcinoma and discuss the therapeutic potential of targeting JAK/STAT signaling for the treatment of gastric cancer.

Nucleic acid-based approaches to STAT inhibition

Silencing of abnormally activated genes can be accomplished in a highly specific manner using nucleic acid based approaches. The focus of this review includes the different nucleic acid based inhibition strategies such as antisense oligodeoxynucleotides, small interfering RNA (siRNA), dominant-negative constructs, G-quartet oligonucleotides and decoy oligonucleotides, their mechanism of action and the effectiveness of these approaches to targeting the STAT (signal transducer and activator of transcription) proteins in cancer. Among the STAT proteins, especially STAT3, followed by STAT5, are the most frequently activated oncogenic STATs, which have emerged as plausible therapeutic cancer targets. Both STAT3 and STAT5 have been shown to regulate numerous oncogenic signaling pathways including proliferation, survival, angiogenesis and migration/invasion.

Identification of a natural product-like STAT3 dimerization inhibitor by structure-based virtual screening

STAT3 regulates a variety of genes involved with cell proliferation, differentiation, apoptosis, angiogenesis, metastasis, inflammation, and immunity. The purpose of this study was to apply molecular docking techniques to identify STAT3 inhibitors from a database of over 90000 natural product and natural product-like compounds. The virtual screening campaign furnished 14 hit compounds, from which compound 1 emerged as a top candidate. Compound 1 inhibited STAT3 DNA-binding activity in vitro and attenuated STAT3-directed transcription in cellulo with selectivity over STAT1 and with comparable potency to the well-known STAT3 inhibitor S3I-201. Furthermore, compound 1 inhibited STAT3 dimerization and decreased STAT3 phosphorylation in cells without affecting STAT1 dimerization and phosphorylation. Compound 1 also exhibited selective anti-proliferative activity against cancer cells over normal cells in vitro. Molecular docking analysis suggested that compound 1 might putatively function as an inhibitor of STAT3 dimerization by binding to the SH2 domain. This study also validates the use of in silico techniques to identify inhibitors of protein-protein interactions, which are typically considered difficult to target with small molecules.

Transcription Factor STAT3 as a Novel Molecular Target for Cancer Prevention

Signal Transducers and Activators of Transcription (STATs) are a family of transcription factors that regulate cell proliferation, differentiation, apoptosis, immune and inflammatory responses, and angiogenesis. Cumulative evidence has established that STAT3 has a critical role in the development of multiple cancer types. Because it is constitutively activated during disease progression and metastasis in a variety of cancers, STAT3 has promise as a drug target for cancer therapeutics. Recently, STAT3 was found to have an important role in maintaining cancer stem cells in vitro and in mouse tumor models, suggesting STAT3 is integrally involved in tumor initiation, progression and maintenance. STAT3 has been traditionally considered as nontargetable or undruggable, and the lag in developing effective STAT3 inhibitors contributes to the current lack of FDA-approved STAT3 inhibitors. Recent advances in cancer biology and drug discovery efforts have shed light on targeting STAT3 globally and/or specifically for cancer therapy. In this review, we summarize current literature and discuss the potential importance of STAT3 as a novel target for cancer prevention and of STAT3 inhibitors as effective chemopreventive agents.

A specific STAT3-binding peptide exerts antiproliferative effects and antitumor activity by inhibiting STAT3 phosphorylation and signaling

STAT3 promotes the survival, proliferation, metastasis, immune escape, and drug resistance of cancer cells, making its targeting an appealing prospect. However, although multiple inhibitors of STAT3 and its regulatory or effector pathway elements have been developed, bioactive agents have been somewhat elusive. In this report, we report the identification of a specific STAT3-binding peptide (APTSTAT3) through phage display of a novel "aptide" library. APTSTAT3 bound STAT3 with high specificity and affinity (∼231 nmol/L). Addition of a cell-penetrating motif to the peptide to yield APTSTAT3-9R enabled uptake by murine B16F1 melanoma cells. Treatment of various types of cancer cells with APTSTAT3-9R blocked STAT3 phosphorylation and reduced expression of STAT targets, including cyclin D1, Bcl-xL, and survivin. As a result, APTSTAT3-9R suppressed the viability and proliferation of cancer cells. Furthermore, intratumoral injection of APTSTAT3-9R exerted potent antitumor activity in both xenograft and allograft tumor models. Our results offer a preclinical proof-of-concept for APTSTAT3 as a tractable agent for translation to target the broad array of cancers harboring constitutively activated STAT3.

Novel inhibitors of signal transducer and activator of transcription 3 signaling pathway: an update on the recent patent literature

INTRODUCTION

The signal transducer and activator of transcription 3 (STAT3) is a transcription factor that plays a key role in normal cell growth and is constitutively activated in about 70% of solid and hematological cancers. Thus, the development of potent and selective inhibitors that target STAT3 is of interest especially in the cancer therapeutic area.

AREAS COVERED

This review updates new patents claiming STAT3 inhibitors and their uses published from 2011 to 2013. Pre-2011 patents have been extensively covered in previous reviews. Comments on the context of each chemical series are given where applicable to orientate the readers on the bewildering array of molecular designs now available.

EXPERT OPINION

The growing number of preclinical studies in numerous malignances as well as the first clinical trials of STAT3 inhibitors suggest that STAT3 remains a valid target for the treatment of human cancers as well as inflammatory diseases and/or autoimmune disorders. So, the future looks bright for patients because many new drugs are being developed and now combinations of STAT3 inhibitors with other targeted agents can diminish the resistance to traditional chemotherapy. These advances are expected to lead to further significant progress improving patient outcomes and quality of life.

Honokiol inhibits epithelial-mesenchymal transition in breast cancer cells by targeting signal transducer and activator of transcription 3/Zeb1/E-cadherin axis

Epithelial-mesenchymal transition (EMT), a critical step in the acquisition of metastatic state, is an attractive target for therapeutic interventions directed against tumor metastasis. Honokiol (HNK) is a natural phenolic compound isolated from an extract of seed cones from Magnolia grandiflora. Recent studies from our lab show that HNK impedes breast carcinogenesis. Here, we provide molecular evidence that HNK inhibits EMT in breast cancer cells resulting in significant downregulation of mesenchymal marker proteins and concurrent upregulation of epithelial markers. Experimental EMT induced by exposure to TGFβ and TNFα in spontaneously immortalized nontumorigenic human mammary epithelial cells is also completely reversed by HNK as evidenced by morphological as well as molecular changes. Investigating the downstream mediator(s) that may direct EMT inhibition by HNK, we found functional interactions between HNK, Stat3, and EMT-signaling components. In vitro and in vivo analyses show that HNK inhibits Stat3 activation in breast cancer cells and tumors. Constitutive activation of Stat3 abrogates HNK-mediated activation of epithelial markers whereas inhibition of Stat3 using small molecule inhibitor, Stattic, potentiates HNK-mediated inhibition of EMT markers, invasion and migration of breast cancer cells. Mechanistically, HNK inhibits recruitment of Stat3 on mesenchymal transcription factor Zeb1 promoter resulting in decreased Zeb1 expression and nuclear translocation. We also discover that HNK increases E-cadherin expression via Stat3-mediated release of Zeb1 from E-cadherin promoter. Collectively, this study reports that HNK effectively inhibits EMT in breast cancer cells and provide evidence for a previously unrecognized cross-talk between HNK and Stat3/Zeb1/E-cadherin axis.

STAT3 oligonucleotide inhibits tumor angiogenesis in preclinical models of squamous cell carcinoma

PURPOSE

Signal transducer and activator of transcription 3 (STAT3) has shown to play a critical role in head and neck squamous cell carcinoma (HNSCC) and we have recently completed clinical trials of STAT3 decoy oligonucleotide in patients with recurrent or metastatic HNSCC. However, there is limited understanding of the role of STAT3 in modulating other aspects of tumorigenesis such as angiogenesis. In this study, we aimed to examine the effects of STAT3 decoy oligonucleotide on tumor angiogenesis.

EXPERIMENTAL DESIGN

A STAT3 decoy oligonucleotide and small interfering RNA (siRNA) were used to inhibit STAT3 in endothelial cells in vitro and in vivo. The biochemical effects of STAT3 inhibition were examined in conjunction with the consequences on proliferation, migration, apoptotic staining, and tubule formation. Additionally, we assessed the effects of STAT3 inhibition on tumor angiogenesis using murine xenograft models.

RESULTS

STAT3 decoy oligonucleotide decreased proliferation, induces apoptosis, decreased migration, and decreased tubule formation of endothelial cells in vitro. The STAT3 decoy oligonucleotide also inhibited tumor angiogenesis in murine tumor xenografts. Lastly, our data suggest that the antiangiogenic effects of STAT3 decoy oligonucleotide were mediatedthrough the inhibition of both STAT3 and STAT1.

CONCLUSIONS

The STAT3 decoy oligonucleotidewas found to be an effective antiangiogenic agent, which is likely to contribute to the overall antitumor effects of this agent in solid tumors.Taken together with the previously demonstrated antitumor activity of this agent, STAT3 decoy oligonucleotide represents a promising single agent approach to targeting both the tumor and vascular compartments in various malignancies.

Blockage of STAT3 signaling pathway with a decoy oligodeoxynucleotide inhibits growth of human ovarian cancer cells

Transcription factor decoy oligodeoxynucleotides (ODN) represent a novel tool for targeted inhibition of the STAT3 signaling pathway. To investigate its therapeutic potential in ovarian cancer, a double-stranded decoy ODN mimicking STAT3-specific cis-elements was transfected into two ovarian cancer cell lines OVCAR3 and SKOV3. The STAT3 decoy ODN treatment specifically blocked STAT3 signaling, and inhibited cell proliferation by inducing apoptosis and cell cycle arrest. These results suggest that targeted blockade of the STAT3 signaling pathway with a decoy ODN may represent a potential therapeutic approach in the treatment of ovarian cancer.

Potent Targeting of the STAT3 Protein in Brain Cancer Stem Cells: A Promising Route for Treating Glioblastoma

The STAT3 gene is abnormally active in glioblastoma (GBM) and is a critically important mediator of tumor growth and therapeutic resistance in GBM. Thus, for poorly treated brain cancers such as gliomas, astrocytomas, and glioblastomas, which harbor constitutively activated STAT3, a STAT3-targeting therapeutic will be of significant importance. Herein, we report a most potent, small molecule, nonphosphorylated STAT3 inhibitor, 31 (SH-4-54) that strongly binds to STAT3 protein (K D = 300 nM). Inhibitor 31 potently kills glioblastoma brain cancer stem cells (BTSCs) and effectively suppresses STAT3 phosphorylation and its downstream transcriptional targets at low nM concentrations. Moreover, in vivo, 31 exhibited blood-brain barrier permeability, potently controlled glioma tumor growth, and inhibited pSTAT3 in vivo. This work, for the first time, demonstrates the power of STAT3 inhibitors for the treatment of BTSCs and validates the therapeutic efficacy of a STAT3 inhibitor for GBM clinical application.

Role of STAT3 in cancer metastasis and translational advances

Signal transducer and activator of transcription 3 (STAT3) is a latent cytoplasmic transcription factor, originally discovered as a transducer of signal from cell surface receptors to the nucleus. It is activated by tyrosine phosphorylation at position 705 leading to its dimerization, nuclear translocation, DNA binding, and activation of gene transcription. Under normal physiological conditions, STAT3 activation is tightly regulated. However, compelling evidence suggests that STAT3 is constitutively activated in many cancers and plays a pivotal role in tumor growth and metastasis. It regulates cellular proliferation, invasion, migration, and angiogenesis that are critical for cancer metastasis. In this paper, we first describe the mechanism of STAT3 regulation followed by how STAT3 is involved in cancer metastasis, then we summarize the various small molecule inhibitors that inhibit STAT3 signaling.

Inhibition of STAT3 by niclosamide synergizes with erlotinib against head and neck cancer

Epidermal growth factor receptor (EGFR) is extensively expressed in head and neck cancer. However, EGFR-targeted therapy has only modest efficacy in head and neck cancer, through mechanisms that are not fully understood. Here, we found that inhibition of EGFR by erlotinib stimulated phosphorylation and activation of STAT3 leading to increased Bcl2/Bcl-XL expression in head and neck cancer cells, which may dampen the therapeutic efficacy of erlotinib against head and neck cancer. Erlotinib-enhanced STAT3 phosphorylation results, at least in part, from suppression of its physiological phosphatase, PTPMeg2. Specific knockdown of STAT3 by RNA interference significantly sensitized head and neck cancer cells to erlotinib treatment. Pharmacological inhibition of STAT3 by niclosamide not only blocked erlotinib-stimulated STAT3 phosphorylation but also synergistically repressed head and neck cancer growth in vitro and in vivo. Combined inhibition of EGFR and STAT3 by erlotinib and niclosamide more effectively induced apoptosis in tumor tissues without toxicity for normal tissues. Based on our findings, treatment with erlotinib combined with niclosamide may offer an effective therapeutic approach to improve the prognosis of head and neck cancer.

Inflammation and gastrointestinal cancer: an overview

Gastrointestinal cancers collectively rank as the most lethal cancers worldwide, and are strongly linked with chronic inflammation. Despite advances over the last decade into our understanding of the etiology of these malignancies, both from a host perspective and with respect to environmental factors, current treatment strategies comprising surgery, chemotherapy and/or radiotherapy are still associated with unacceptably poor patient survival rates. Accordingly, there is a pressing need to identify new molecular targets which can underpin the development of next-generation treatment strategies to improve patient outcomes, and serve as biomarkers for early disease detection. In this review we provide an updated discussion on the identity of such candidate molecules, with a focus on innate immune system regulators within the gastrointestinal mucosal epithelium which promote inflammation and tumorigenesis.

Tissue biomarkers as prognostic variables of cervical cancer

The most important prognostic variables of cervical carcinoma are FIGO stage, lymph node status and clinical-pathological features of primary tumor. Recently, there has been increasing interest in the identification of biomarkers able to predict both response to treatment and survival. The aim of this review is to critically evaluate current published evidence on the ability of various tissue biomarkers to predict the clinical outcome of patients with cervical carcinoma. In particular, the paper takes into account DNA content, cell-cycle and apoptosis-regulatory proteins, epidermal growth factor receptor [EGFR], vascular endothelial growth factor [VEGF], cyclooxygenase [COX]-2, signal transducer and activator of transcription [Stat]3, human papilloma virus [HPV] status, tumor hypoxia, tumor infiltrating lymphocytes [TIL], microarray technology and microRNA (miRNA). The presence of HPV-18 genotype and an elevated VEGF expression appear to be poor prognostic factors in women with early disease treated with primary surgery, whereas the expression of EGFR, VEGF, COX-2 and tumor hypoxia may have a major impact on the survival of patients treated with definitive radiotherapy or chemoradiation. The data supporting the reliability of ΔNp73 and TAp73α as novel biomarkers of response to radiotherapy are interesting but still limited. DNA microarray technology could offer new laboratory tools for a rationale planning of treatment strategy, and miRNAs might represent new candidate targets to be investigated for both prognostic and therapeutic purposes. Moreover, the assessment of different types of TIL and their ligands in tumor biopsies could enable the identification of a subset of high-risk patients, paving the way to novel immune therapies aimed at blocking T-reg cell activity.