Dual inhibition of Janus and Src family kinases by novel indirubin derivative blocks constitutively-activated Stat3 signaling associated with apoptosis of human pancreatic cancer cells

Rethinking therapeutic strategies of dual-target drugs: An update on pharmacological small-molecule compounds in cancer

Oncogenes and tumor suppressors are well-known to orchestrate several signaling cascades, regulate extracellular and intracellular stimuli, and ultimately control the fate of cancer cells. Accumulating evidence has recently revealed that perturbation of these key modulators by mutations or abnormal protein expressions are closely associated with drug resistance in cancer therapy; however, the inherent drug resistance or compensatory mechanism remains to be clarified for targeted drug discovery. Thus, dual-target drug development has been widely reported to be a promising therapeutic strategy for improving drug efficiency or overcoming resistance mechanisms. In this review, we provide an overview of the therapeutic strategies of dual-target drugs, especially focusing on pharmacological small-molecule compounds in cancer, including small molecules targeting mutation resistance, compensatory mechanisms, synthetic lethality, synergistic effects, and other new emerging strategies. Together, these therapeutic strategies of dual-target drugs would shed light on discovering more novel candidate small-molecule drugs for the future cancer treatment.

Construction and validation of a RARRES3-based prognostic signature related to the specific immune microenvironment of pancreatic cancer

Background

Tumor immune microenvironment (TiME) is prognostically instructive in Pancreatic adenocarcinoma (PAAD). However, the potential value of TiME-related genes in the individualized immunotherapy of PAAD has not been clarified.

Methods

Correlation between Immune-Related Genes (IRGs) and immune-related transcription factors (TFs) was performed to prove the immune correlation of selected genes. Immune-related molecular subtypes were identified by consensus clustering. The TiME-score, an immune microenvironment-related prognostic signature for PAAD, was constructed using minimum absolute contraction and selection operator regression (Lasso-Cox). The International Cancer Genome Consortium (ICGC) dataset validated the reliability of TiME-score as external validation. Single-cell samples from GSE197177 confirmed microenvironment differences of TiME-score hub genes between tumor and its paracancer tissues. Then, RARRES3, a hub gene in TiME-score, was further analyzed about its upstream TP53 mutation and the specific immune landscape of itself in transcriptome and Single-cell level. Eventually, TiME-score were validated in different therapeutic cohorts of PAAD mice models.

Results

A 14-genes PAAD immune-related risk signature, TiME-score, was constructed based on IRGs. The differences of TiME-score hub genes in single-cell samples of PAAD cancer tissues and adjacent tissues were consistent with the transcriptome. Single-cell samples of cancer tissues showed more pronounced immune cell infiltration. The upstream mutation factor TP53 of RARRES3 was significantly enriched in immune-related biological processes. High RARRES3 expression was correlated with a worse prognosis and high macrophages M1 infiltration. Additionally, the immunohistochemistry of hub genes AGT, DEFB1, GH1, IL20RB, and TRAF3 in different treatment cohorts of mice PAAD models were consistent with the predicted results. The combination of immunotherapy, chemotherapy and targeted therapy has shown significantly better therapeutic effects than single drug therapy in PAAD.

Conclusion

TiME-score, as a prognostic signature related to PAAD-specific immune microenvironment constructed based on RARRES3, has predictive value for prognosis and the potential to guide individualized immunotherapy for PAAD patients.

Natural STAT3 Inhibitors for Cancer Treatment: A Comprehensive Literature Review

Cancer is one of the leading causes of mortality and morbidity worldwide, affecting millions of people physically and financially every year. Over time, many anticancer treatments have been proposed and studied, including synthetic compound consumption, surgical procedures, or grueling chemotherapy. Although these treatments have improved the daily life quality of patients and increased their survival rate and life expectancy, they have also shown significant drawbacks, including staggering costs, multiple side effects, and difficulty in compliance and adherence to treatment. Therefore, natural compounds have been considered a possible key to overcoming these problems in recent years, and thorough research has been done to assess their effectiveness. In these studies, scientists have discovered a meaningful interaction between several natural materials and signal transducer and activator of transcription 3 molecules. STAT3 is a transcriptional protein that is vital for cell growth and survival. Mechanistic studies have established that activated STAT3 can increase cancer cell proliferation and invasion while reducing anticancer immunity. Thus, inhibiting STAT3 signaling by natural compounds has become one of the favorite research topics and an attractive target for developing novel cancer treatments. In the present article, we intend to comprehensively review the latest knowledge about the effects of various organic compounds on inhibiting the STAT3 signaling pathway to cure different cancer diseases.

The Fundamental Role of Oxime and Oxime Ether Moieties in Improving the Physicochemical and Anticancer Properties of Structurally Diverse Scaffolds

The present review explores the critical role of oxime and oxime ether moieties in enhancing the physicochemical and anticancer properties of structurally diverse molecular frameworks. Specific examples are carefully selected to illustrate the distinct contributions of these functional groups to general strategies for molecular design, modulation of biological activities, computational modeling, and structure-activity relationship studies. An extensive literature search was conducted across three databases, including PubMed, Google Scholar, and Scifinder, enabling us to create one of the most comprehensive overviews of how oximes and oxime ethers impact antitumor activities within a wide range of structural frameworks. This search focused on various combinations of keywords or their synonyms, related to the anticancer activity of oximes and oxime ethers, structure-activity relationships, mechanism of action, as well as molecular dynamics and docking studies. Each article was evaluated based on its scientific merit and the depth of the study, resulting in 268 cited references and more than 336 illustrative chemical structures carefully selected to support this analysis. As many previous reviews focus on one subclass of this extensive family of compounds, this report represents one of the rare and fully comprehensive assessments of the anticancer potential of this group of molecules across diverse molecular scaffolds.

Vortioxetine hydrobromide inhibits the growth of gastric cancer cells in vivo and in vitro by targeting JAK2 and SRC

Gastric cancer is the fourth leading cause of cancer deaths worldwide. Most patients are diagnosed in the advanced stage. Inadequate therapeutic strategies and the high recurrence rate lead to the poor 5-year survival rate. Therefore, effective chemopreventive drugs for gastric cancer are urgently needed. Repurposing clinical drugs is an effective strategy for discovering cancer chemopreventive drugs. In this study, we find that vortioxetine hydrobromide, an FDA-approved drug, is a dual JAK2/SRC inhibitor, and has inhibitory effects on cell proliferation of gastric cancer. Computational docking analysis, pull-down assay, cellular thermal shift assay (CETSA) and in vitro kinase assays are used to illustrate vortioxetine hydrobromide directly binds to JAK2 and SRC kinases and inhibits their kinase activities. The results of non-reducing SDS-PAGE and Western blotting indicate that vortioxetine hydrobromide suppresses STAT3 dimerization and nuclear translocation activity. Furthermore, vortioxetine hydrobromide inhibits the cell proliferation dependent on JAK2 and SRC and suppresses the growth of gastric cancer PDX model in vivo. These data demonstrate that vortioxetine hydrobromide, as a novel dual JAK2/SRC inhibitor, curbs the growth of gastric cancer in vitro and in vivo by JAK2/SRC-STAT3 signaling pathways. Our results highlight that vortioxetine hydrobromide has the potential application in the chemoprevention of gastric cancer.

Design, synthesis and biological evaluation of novel tubulin inhibitors targeting colchicine sites

Tubulin, a potential target for antitumor drug discovery, contains three main binding sites for clinical inhibitors: colchicine, vinblastine, and paclitaxel. CA-4 has been reported to be a classic tubulin inhibitor targeting the colchicine site. Herein, based on the structural modification of CA-4, 48 novel compounds were designed and synthesized by selecting structural fragments with various biological activities to replace the cis double bond of CA-4. Among these compounds, compound 8p was the most effective tubulin inhibitor (IC₅₀ = 65 nM aganist HepG2 cells). Immunofluorescence experiment confirmed the anti-tumor effect of 8p by destroying the network structure of microtubules. Further studies showed that 8p induced tumor cell apoptosis, arrested cell cycle, inhibited tumor cell migration and invasion.

Synthesis and antibacterial activity studies in vitro of indirubin-3'-monoximes

Multi-drug-resistant microbial pathogens are a serious global health problem. New compounds with antibacterial activity serve as good candidates for developing novel antibacterial drugs which is very urgent and important. In this work, based on the unique scaffold of indirubin, an active ingredient of traditional Chinese medicine formulation Danggui Luhui Wan, we synthesized 29 indirubin-3'-monoximes and preliminarily evaluated their antibacterial activities. The antibacterial activity results demonstrated that the synthesized indirubin-3'-monoximes 5a-5z and 5aa-5ad displayed good potency against S. aureus ATCC25923 (MIC = 0.4-25.6 μg mL-1). Among them, we found that the 5-F, 5-Cl and 7-CF3 substituted indirubin-3'-monoximes 5r, 5s and 5aa also showed better antibacterial efficiency for S. aureus (MICs up to 0.4 μg mL-1) than the prototype natural product indirubin (MIC = 32 μg mL-1). More importantly, indirubin-3'-monoxime 5aa has certain synergistic effect with levofloxacin against clinic multidrug-resistant S. aureus (fractional inhibitory concentration index: 0.375). In addition, relevant experiments including electron microscopy observations, PI staining and the leakage of extracellular potassium ions and nucleic acid (260 nm) have been performed after treating S. aureus with indirubin-3'-monoxime 5aa, and the results revealed that indirubin-3'-monoximes could increase the cell membrane permeability of S. aureus. Although indirubin-3'-monoxime 5aa showed some cytotoxicity toward SH-SY5Y cells relative to compounds 5r and 5s, the skin irritation test of male mice after shaving showed that compound 5aa at a concentration of 12.8 μg mL-1 had no toxicity to mouse skin, and it could be used as a leading compound for skin antibacterial drugs.

Pharmacological properties of indirubin and its derivatives

BACKGROUND

Indirubin is the main bioactive component of the traditional Chinese medicine Indigo naturalis and is a bisindole alkaloid. Multiple studies have shown that indirubin exhibits good anticancer, anti-inflammatory and neuroprotective properties.

METHODS

The purpose of this review is to provide a summary of the pharmacological mechanisms of indirubin and its derivatives.

RESULTS

Indirubin and its derivatives exert anticancer effects by regulating the expression of cyclin-dependent kinases (CDKs), GSK-3β, Bax, Bcl-2, C-MYC, matrix metalloproteinases (MMPs), and focal adhesion kinase (FAK) through the PI3K/AKT/mTOR, nuclear factor (NF)-κB, mitogen-activated protein kinase (MAPK), JAK/signal transducer and activator of transcription 3 (STAT3) pathways and other signaling pathways. We also reviewed the anti-inflammatory and neuroprotective properties of indirubin and its derivatives.

CONCLUSION

The findings of recent studies assessing indirubin and its derivatives suggest that these compounds can be used as potential drugs to treat tumors, inflammation, neuropathy and bacterial infection.

Dual-target Janus kinase (JAK) inhibitors: Comprehensive review on the JAK-based strategies for treating solid or hematological malignancies and immune-related diseases

Janus kinases (JAKs) are the non-receptor tyrosine kinases covering JAK1, JAK2, JAK3, and TYK2 which regulate signal transductions of hematopoietic cytokines and growth factors to play essential roles in cell growth, survival, and development. Dysregulated JAK activity leading to a constitutively activated signal transducers and activators of transcription (STAT) is strongly associated with immune-related diseases and cancers. Targeting JAK to interfere the signaling of JAK/STAT pathway has achieved quite success in the treatment of these diseases. However, inadequate clinical response and serious adverse events come along by the treatment of monotherapy of JAK inhibitors. With better and deeper understanding of JAK/STAT pathway in the pathogenesis of diseases, researchers start to show huge interest in combining inhibition of JAK and other oncogenic targets to realize a broader regulation on pathological processes to block disease development and progression, which has hastened extensive research of dual JAK inhibitors over the past decades. Until now, studies of dual JAK inhibitors have added BTK, SYK, FLT3, HDAC, Src, and Aurora kinases to the overall inhibitory profile and demonstrated significant advantage and superiority over single-target inhibitors. In this review, we elucidated the possible mechanism of synergic effects caused by dual JAK inhibitors and briefly describe the development of these agents.

Anticancer potential of indirubins in medicinal chemistry: Biological activity, structural modification, and structure-activity relationship

Indirubin is the crucial ingredient of Danggui Longhui Wan and Qing-Dai, traditional Chinese medicine herbal formulas used for the therapy of chronic myelocytic leukemia in China for hundreds of years. Although the monomeric indirubin has been used in China for the treatment human chronic myelocytic leukemia. However, due to low water solubility, poor pharmacokinetic properties and low therapeutic effects are the major obstacle, and had significantly limited its clinical application. Consequently, the attractive anticancer profile of indirubin has enthused numerous researchers to discover novel indirubin derivatives with improved pharmacodynamic activity as well as good pharmacokinetic property. In this paper, we comprehensively review the recent progress of anticancer potential of indirubins, structural modification and structure-activity relationship, which may provide useful direction for the further development of novel indirubins with improved pharmacological profiles for the treatment of various types of cancer.

Oximes: Novel Therapeutics with Anticancer and Anti-Inflammatory Potential

Oximes have been studied for decades because of their significant roles as acetylcholinesterase reactivators. Over the last twenty years, a large number of oximes have been reported with useful pharmaceutical properties, including compounds with antibacterial, anticancer, anti-arthritis, and anti-stroke activities. Many oximes are kinase inhibitors and have been shown to inhibit over 40 different kinases, including AMP-activated protein kinase (AMPK), phosphatidylinositol 3-kinase (PI3K), cyclin-dependent kinase (CDK), serine/threonine kinases glycogen synthase kinase 3 α/β (GSK-3α/β), Aurora A, B-Raf, Chk1, death-associated protein-kinase-related 2 (DRAK2), phosphorylase kinase (PhK), serum and glucocorticoid-regulated kinase (SGK), Janus tyrosine kinase (JAK), and multiple receptor and non-receptor tyrosine kinases. Some oximes are inhibitors of lipoxygenase 5, human neutrophil elastase, and proteinase 3. The oxime group contains two H-bond acceptors (nitrogen and oxygen atoms) and one H-bond donor (OH group), versus only one H-bond acceptor present in carbonyl groups. This feature, together with the high polarity of oxime groups, may lead to a significantly different mode of interaction with receptor binding sites compared to corresponding carbonyl compounds, despite small changes in the total size and shape of the compound. In addition, oximes can generate nitric oxide. This review is focused on oximes as kinase inhibitors with anticancer and anti-inflammatory activities. Oximes with non-kinase targets or mechanisms of anti-inflammatory activity are also discussed.

Small Molecules in the Treatment of Squamous Cell Carcinomas: Focus on Indirubins

Simple Summary

In this review, the genetic landscape of squamous cell carcinoma is related to the potential targets of indirubin-based small molecules in cancer therapy. Being a component of traditional Chinese medicine, indirubins are used to treat chronic or inflammatory diseases, and have received increasing attention in cancer treatment due to their proapoptotic and antiproliferative activity. Frequent genetic alterations of squamous cell carcinomas are summarized, and it is discussed how these may render tumors susceptible to indirubin-based small molecule inhibitors.

Abstract

Skin cancers are the most common malignancies in the world. Among the most frequent skin cancer entities, squamous cell carcinoma (SCC) ranks second (~20%) after basal cell carcinoma (~77%). In early stages, a complete surgical removal of the affected tissue is carried out as standard therapy. To treat advanced and metastatic cancers, targeted therapies with small molecule inhibitors are gaining increasing attention. Small molecules are a heterogeneous group of protein regulators, which are produced by chemical synthesis or fermentation. The majority of them belong to the group of receptor tyrosine kinase inhibitors (RTKIs), which specifically bind to certain RTKs and directly influence the respective signaling pathway. Knowledge of characteristic molecular alterations in certain cancer entities, such as SCC, can help identify tumor-specific substances for targeted therapies. Most frequently, altered genes in SCC include TP53, NOTCH, EGFR, and CCND1. For example, the gene CCND1, which codes for cyclin D1 protein, is upregulated in nearly half of SCC cases and promotes proliferation of affected cells. A treatment with the small molecule 5′-nitroindirubin-monoxime (INO) leads to inhibition of cyclin D1 and thus inhibition of proliferation. As a component of Danggui Longhui Wan, a traditional Chinese medicine, indirubins are used to treat chronic diseases and have been shown to inhibit inflammatory reactions. Indirubins are pharmacologically relevant small molecules with proapoptotic and antiproliferative activity. In this review, we discuss the current literature on indirubin-based small molecules in cancer treatment. A special focus is on the molecular biology of squamous cell carcinomas, their alterations, and how these are rendered susceptible to indirubin-based small molecule inhibitors. The potential molecular mechanisms of the efficacy of indirubins in killing SCC cells will be discussed as well.

Dauricine inhibits proliferation and promotes death of melanoma cells via inhibition of Src/STAT3 signaling

Melanoma is the most common type of skin cancer. Signal transducer and activator of transcription 3 (STAT3) signaling has been demonstrated to be a therapeutic target for melanoma. Dauricine (Dau), an alkaloid compound isolated from the root of Menispermum dauricum DC., has shown tumor-suppressing effects in multiple human cancers, but its potential in melanoma remains unexplored. In this study, we demonstrated that Dau significantly inhibited the viability and proliferation of A375 and A2058 melanoma cells. Death of melanoma cells was also markedly promoted by Dau. Moreover, Dau inhibited phosphorylation-mediated activation of STAT3 and Src in a dose-dependent manner. Notably, constitutive activation of Src partially abolished the antiproliferative and cytotoxic activities of Dau on melanoma cells. Molecular docking showed that Dau could dock on the kinase domain of Src with a binding energy of -10.42 kcal/mol. Molecular dynamics simulations showed that Src-Dau binding was stable. Surface plasmon resonance imaging analysis also showed that Dau has a strong binding affinity to Src. In addition, Dau suppressed the growth of melanoma cells and downregulated the activation of Src/STAT3 in a xenograft model in vivo. These data demonstrated that Dau inhibits proliferation and promotes cell death in melanoma cells by inhibiting the Src/STAT3 pathways.

UXT antisense RNA 1 sever as a novel prognostic long non-coding RNA in early stage pancreatic ductal adenocarcinoma patients after receiving pancreaticoduodenectomy

Objective: The principal objective of this project was to investigate the prognostic value of UXT antisense RNA 1 (UXT-AS1) in pancreatic ductal adenocarcinoma (PDAC), as well as its biological function mechanisms and the screening of targeted drugs using The Cancer Genome Atlas (TCGA) PDAC genome-wide RNA sequencing (RNA-seq) dataset.

Methods: We used TCGA 112 early stage PDAC patients to screen the prognostic value of UXT-AS1. Biological functions and mechanisms of UXT-AS1 were investigated by co-expression analysis, differentially expressed genes (DEGs) and gene set enrichment analysis, while targeted drug screening was investigated by connectivity Map (CMap).

Results: By analyzing the dataset from TCGA cohort, we found that UXT-AS1 was significantly up-regulated in pancreatic cancer tissues. Multivariate survival analysis demonstrated that PDAC patients with high UXT-AS1 expression had an unfavourable prognosis (adjusted P=0.033, HR=1.830, 95%CI=1.051-3.188). Genome-wide co-expression analysis and gene set enrichment analysis suggested that UXT-AS1 may act as a pivotal part in PDAC by participating in nuclear factor kappa beta, regulation of tumor necrosis factor, cell adhesion, T cell receptor signaling pathway, and numerous immune-related biological processes and signaling pathways. Functional enrichment analysis of DEGs between high- and low-UXT-AS1 expression groups suggested that these DEGs were significant enriched in B cell receptor complex, response to drug chemical carcinogenesis and drug metabolism-cytochrome P450. CMap analysis revealed that quipazine and terazosin may be targeted drugs for UXT-AS1 in PDAC.

Conclusion: Our current study has identified UXT-AS1 as a novel biomarker for the prognosis of early stage PDAC. We also clarified its biological functional mechanisms and identified two targeted drugs of UXT-AS1 in PDAC.

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.

IGFBP2 promotes tumor progression by inducing alternative polarization of macrophages in pancreatic ductal adenocarcinoma through the STAT3 pathway

Tumor-associated macrophages (TAMs) represent the M2-like phenotype with potent immunosuppressive activity, and play a pro-tumor role in pancreatic ductal adenocarcinoma (PDAC) biology. In this study, we investigated the role of the insulin-like growth factor binding protein 2 (IGFBP2) as a determinant of TAM polarity. Clinical data revealed that the levels of IGFBP2 correlated with M2 TAMs accumulation and disease progression in human PDAC. In vivo mouse model experiments showed that IGFBP2 promoted an immunosuppressive microenvironment and tumor growth in a macrophage dependent manner. Bioinformatics analysis of PDAC transcriptomes revealed a significant association between IGFBP2 expression and M2 macrophage polarization and signal transducer and activator of transcription 3 (STAT3) activation. Mechanistic investigations demonstrated that IGFBP2 augmented the expression and secretion of IL-10 through STAT3 activation in PDAC cells, which induced TAM polarization toward an M2 phenotype. IGFBP2-polarized M2 macrophages significantly increased Tregs infiltration and impaired antitumor T-cell immunity in a mouse model. Thus, our investigations have illuminated the IGFBP2 signaling pathway that contributes to the macrophage-based immunosuppressive microenvironment in PDAC, suggesting that blocking the IGFBP2 axis constitutes a potential treatment strategy to reset TAM polarization toward an antitumor state in PDAC.

STAT3 transcription factor as target for anti-cancer therapy

STATs constitute a large family of transcription activators and transducers of signals that have an important role in many cell functions as regulation of proliferation and differentiation of the cell also regulation of apoptosis and angiogenesis. STAT3 as a member of that family, recently was discovered to have a vital role in progression of different types of cancers. The activation of STAT3 was observed to regulate multiple gene functions during cancer-like cell proliferation, differentiation, apoptosis, metastasis, inflammation, immunity, cell survival, and angiogenesis. The inhibition of STAT3 activation has been an important target for cancer therapy. Inhibitors of STAT3 have been used for a long time for treatment of many types of cancers like leukemia, melanoma, colon, and renal cancer. In this review article, we summarize and discuss different drugs inhibiting the action of STAT3 and used in treatment of different types of cancer.

NHE1 Mediates 5-Fu Resistance in Gastric Cancer via STAT3 Signaling Pathway

BACKGROUND

Several recent studies have addressed the role of Na+/H+ exchanger isoform 1 (NHE1) in tumor cell growth and apoptosis, including in gastric cancer. However, the role of NHE1 expression related to the 5-Fu resistance in gastric cancer has not been investigated.

METHODS

The expression of NHE1 was examined by qPCR in the SGC7901/5-FU cell line and its parental cell line. pcDNA3.1-NHE1 and NHE1-siRNA were transfected to SGC7901/5-FU resistance cells and cell apoptosis was detected via TUNEL assay. The upstream activators in NHE1 mediated 5-Fu resistant gastric cancer cells were detected by Western blot and immunofluorescent.

RESULTS

A significant increase of the expression of NHE1 was observed in SGC7901 5-FU resistance cells compared to the GES-1 and SGC7901 cell line. NHE1 can suppress the cell apoptosis of SGC7901 5-FU resistance cells and involved in cell cycle. Also, the migration and invasion of SGC7901 5-FU resistance cells were promoted by NHE1. NHE1 also increases the intracellular pH. The results of Western blot analysis showed that NHE1 overexpression induced an increase in the expression of phosphorylated activator transcription factor 3 (pSTAT3). The more obvious phosphorylated level was shown in the phosphorylated STAT3 at pSTAT3tyr705. Further investigations revealed that the constitutive activation of STAT3 may be induced by JAK1 and JAK2, and thus effect the 5-FU resistance by regulating NHE1.

DISCUSSION

In summary, our findings provided evidence that NHE1 contributed to 5-Fu resistance in gastric cancer cells by regulating the JAK/STAT3 pathway. Therefore, NHE1 can be a useful marker for predicting and monitoring 5-Fu resistance.

Highlighted STAT3 as a potential drug target for cancer therapy

Signal transducer and activator of transcription 3 (STAT3) is a cytoplasmic transcription factor that regulates cell proliferation, differentiation, apoptosis, angiogenesis, inflammation and immune responses. Aberrant STAT3 activation triggers tumor progression through oncogenic gene expression in numerous human cancers, leading to promote tumor malignancy. On the contrary, STAT3 activation in immune cells cause elevation of immunosuppressive factors. Accumulating evidence suggests that the tumor microenvironment closely interacts with the STAT3 signaling pathway. So, targeting STAT3 may improve tumor progression, and anti-cancer immune response. In this review, we summarized the role of STAT3 in cancer and the tumor microenvironment, and present inhibitors of STAT3 signaling cascades.

Janus Kinase 1 Plays a Critical Role in Mammary Cancer Progression

Janus kinases (JAKs) and their downstream STAT proteins play key roles in cytokine signaling, tissue homeostasis, and cancer development. Using a breast cancer model that conditionally lacks Janus kinase 1, we show here that JAK1 is essential for IL-6-class inflammatory cytokine signaling and plays a critical role in metastatic cancer progression. JAK1 is indispensable for the oncogenic activation of STAT1, STAT3, and STAT6 in ERBB2-expressing cancer cells, suggesting that ERBB2 receptor tyrosine kinase complexes do not directly activate these STAT proteins in vivo. A genome-wide gene expression analysis revealed that JAK1 signaling has pleiotropic effects on several pathways associated with cancer progression. We established that FOS and MAP3K8 are targets of JAK1/STAT3 signaling, which promotes tumorsphere formation and cell migration. The results highlight the significance of JAK1 as a rational therapeutic target to block IL-6-class cytokines, which are master regulators of cancer-associated inflammation.

Indirubin 3'-Oxime Inhibits Migration, Invasion, and Metastasis InVivo in Mice Bearing Spontaneously Occurring Pancreatic Cancer via Blocking the RAF/ERK, AKT, and SAPK/JNK Pathways

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with high invasive and metastatic potential. We generated a spontaneous PDAC mouse model and examined the therapeutic potential of indirubin 3'-oxime (Indox) against PDAC bearing mouse in vivo.

METHODS

Randomized 3-month-old LSL-Kras^G12D/+;Trp53^flox/+;Pdx-1-cre (KPC^flox) mice were intraperitoneally injected with 40 mg/kg Indox (n = 9) or a vehicle (n = 10) twice a week. At the end point, tumor status including proliferation, direct invasion, and distant metastasis was analyzed histopathologically. The inhibitory potentials of Indox for proliferation, migration/invasion, and the phosphorylation of target molecules were determined in KPC^flox-derived PDAC cells in vitro.

RESULTS

Prolonged survival by Indox via intraperitoneal administration was observed in the KPC^flox mice. Indox inhibited tumor proliferation accompanied with low levels of nuclear phosphorylated cyclin-dependent kinase (p-CDK) and cyclin B1 in vivo. Furthermore, Indox inhibited the migration/invasive activities of PDAC via down-regulation of matrix metalloproteinase (MMP)-9 in vitro and in vivo. Antibody array and immunoblotting analysis revealed that Indox inhibited the phosphorylation of multiple molecules, including key upstream proteins of MMP-9 in RAF/extracellular signal-regulated kinase (ERK), AKT, and stress-activated protein kinase/c-Jun-N-terminal kinase (SAPK/JNK) pathways.

CONCLUSION

Indox inhibited the proliferative, invasive, and metastatic potentials of PDAC in vitro and in vivo. Therefore, Indox could a therapeutic candidate for treating spontaneously occurring PDAC via blocking the RAF/ERK, AKT and SAPK/JNK pathways.

A thiazole-derived oridonin analogue exhibits antitumor activity by directly and allosterically inhibiting STAT3

Constitutive activation of signal transducer and activator of transcription 3 (STAT3) occurs in ∼70% of human cancers, and STAT3 is regarded as one of the most promising targets for cancer therapy. However, specific direct STAT3 inhibitors remain to be developed. Oridonin is an ent-kaurane plant-derived diterpenoid with anti-cancer and anti-inflammatory activities. Here, using an array of cell-based and biochemical approaches, including cell proliferation and apoptosis assays, pulldown and reporter gene assays, site-directed mutagenesis, and molecular dynamics analyses, we report that a thiazole-derived oridonin analogue, CYD0618, potently and directly inhibits STAT3. We found that CYD0618 covalently binds to Cys-542 in STAT3 and suppresses its activity through an allosteric effect, effectively reducing STAT3 dimerization and nuclear translocation, as well as decreasing expression of STAT3-targeted oncogenes. Remarkably, CYD0618 not only strongly inhibited growth of multiple cancer cell lines that harbor constitutive STAT3 activation, but it also suppressed in vivo tumor growth via STAT3 inhibition. Taken together, our findings suggest Cys-542 as a druggable site for selectively inhibiting STAT3 and indicate that CYD0618 represents a promising lead compound for developing therapeutic agents against STAT3-driven diseases.

A novel small molecule A2A adenosine receptor agonist, indirubin-3′-monoxime, alleviates lipid-induced inflammation and insulin resistance in 3T3-L1 adipocytes

Saturated free fatty acid-induced adipocyte inflammation plays a pivotal role in implementing insulin resistance and type 2 diabetes. Recent reports suggest A2A adenosine receptor (A2AAR) could be an attractive choice to counteract adipocyte inflammation and insulin resistance. Thus, an effective A2AAR agonist devoid of any toxicity is highly appealing. Here, we report that indirubin-3′-monoxime (I3M), a derivative of the bisindole alkaloid indirubin, efficiently binds and activates A2AAR which leads to the attenuation of lipid-induced adipocyte inflammation and insulin resistance. Using a combination of in silico virtual screening of potential anti-diabetic candidates and in vitro study on insulin-resistant model of 3T3-L1 adipocytes, we determined I3M through A2AAR activation markedly prevents lipid-induced impairment of the insulin signaling pathway in adipocytes without any toxic effects. While I3M restrains lipid-induced adipocyte inflammation by inhibiting NF-κB dependent pro-inflammatory cytokines expression, it also augments cAMP-mediated CREB activation and anti-inflammatory state in adipocytes. However, these attributes were compromised when cells were pretreated with the A2AAR antagonist, SCH 58261 or siRNA mediated knockdown of A2AAR. I3M, therefore, could be a valuable option to intervene adipocyte inflammation and thus showing promise for the management of insulin resistance and type 2 diabetes.

Clinical and molecular characteristics of bladder urothelial carcinoma subtypes

Bladder urothelial carcinoma (BLCA) is a common malignancy with high heterogeneity. A reasonable molecular subtyping can facilitate biological study and personalized therapy of BLCA. In this study, unsupervised consensus clustering was used to acquire the molecular subtypes of BLCA based on messenger RNA (mRNA) and microRNA (miRNA) data. Gene signature markers and canonical signaling pathways were compared between different subtypes. The Database for Annotation, Visualization and Integrated Discovery (DAVID) was used for the functional annotation of overexpressed genes in different subtypes for Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Three molecular subtypes were identified including C1 (luminal-P53 like), C2 (luminal-other), and C3 (basal-immune-squamous). C2 was different from C1 and C3 in clinical characteristics, including younger, better prognosis, and a higher proportion of papillary, Asian, low-grade, early-stage, lymph node negative, and complete remission patients (P < 0.05). Three molecular subtypes also showed distinct mRNA and miRNA expression patterns. luminal and P53-like markers were highly expressed in subtype C1, luminal markers were highly expressed in subtype C2, and basal, EMT/claudin-low, immune and squamous-differentiation markers were highly expressed in subtype C3. In addition, highly expressed genes in C1 were involved in extracellular signal transduction and cell-cell interaction, highly expressed genes in C2 were associated with oxygen transport, energy and steroid metabolism, and highly expressed genes in C3 were related with inflammatory, immune, cytokine, and signal transduction. BLCA in different molecular subtypes showed different clinical and molecular characteristics and personalized therapy needed to be adopted according to the molecular subtypes.

Indirubin suppresses ovarian cancer cell viabilities through the STAT3 signaling pathway

Background

Indirubin is the active component of Danggui Longhui Wan, a traditional Chinese medicine formulation. Due to its anti-inflammation and anti-tumor effects, indirubin has been widely used for the treatment of inflammation, cancer, and other chronic disease. Herein, we aimed to investigate the role and mechanism of indirubin in human ovarian cancer cell proliferation.

Materials and methods

The cell viability was determined by Cell Counting Kit-8 and colony formation assays by treatment with different dosages of indirubin over 72 hours. Apoptosis was examined by flow cytometry with fluorescein isothiocyanate Annexin V Apoptosis Detection Kit. Western blot assay was finally applied to analyze the expression of cancer-related STAT3 pathway and its downstream proteins.

Results

Indirubin was found to significantly inhibit cell viability and induce apoptosis in 2 human ovarian cancer cell lines. Mechanistic studies revealed that indirubin treatment led to reduced levels of phosphorylated-STAT3, thus repressing the downstream pro-survival proteins and elevating pro-apoptosis ones.

Conclusion

Our study provided the evidence for anti-survival activity of indirubin by inhibiting cell viability and inducing apoptosis in human ovarian cancer cells, which involved impaired STAT3 signaling pathway. Our findings further support indirubin as a potential drug candidate against human ovarian cancer.

Multi-Kinase Inhibitor with Anti-p38γ Activity in Cutaneous T-Cell Lymphoma

Current cutaneous T-cell lymphoma (CTCL) therapies are marked by an abbreviated response, subsequent drug resistance, and poor prognosis for patients with advanced disease. An understanding of molecular regulators involved in CTCL is needed to develop effective targeted therapies. One candidate regulator is p38γ, a mitogen-activated protein kinase crucial for malignant T-cell activity and growth. p38γ gene expression is selectively increased in CTCL patient samples and cell lines but not in healthy T cells. In addition, gene silencing of p38γ reduced CTCL cell viability, showing a key role in CTCL pathogenesis. Screening p38γ inhibitors is critical for understanding the mechanism of CTCL tumorigenesis and developing therapeutic applications. We prioritized a potent p38γ inhibitor (F7, also known as PIK75) through a high-throughput kinase inhibitor screen. At nanomolar concentrations, PIK75, a multiple kinase inhibitor, selectively killed CD4⁺ malignant CTCL cells but spared healthy CD4⁺ cells; induced significant reduction of tumor size in mouse xenografts; and effectively inhibited p38γ enzymatic activity and phosphorylation of its substrate, DLGH1, in CTCL cells and mouse xenografts. Here, we report that PIK75 has a potential clinical application to serve as a scaffold molecule for the development of a more selective p38γ inhibitor.

OSU-A9 inhibits pancreatic cancer cell lines by modulating p38-JAK-STAT3 signaling

Pancreatic cancer is an aggressive malignancy that is the fourth leading cause of death worldwide. Since there is a dire need for novel and effective therapies to improve the poor survival rates of advanced pancreatic cancer patients, we analyzed the antitumor effects of OSU-A9, an indole-3-carbinol derivative, on pancreatic cancer cell lines in vitro and in vivo. OSU-A9 exhibited a stronger antitumor effect than gemcitabine on two pancreatic cancer cell lines, including gemcitabine-resistant PANC-1 cells. OSU-A9 treatment induced apoptosis, the down-regulation of Akt phosphorylation, up-regulation of p38 phosphorylation and decreased phosphorylation of JAK and STAT3. Cell migration and invasiveness assays showed that OSU-A9 reduced cancer cell aggressiveness and inhibited BxPC-3 xenograft growth in nude mice. These results suggest that OSU-A9 modulates the p38-JAK-STAT3 signaling module, thereby inducing cytotoxicity in pancreatic cancer cells. Continued evaluation of OSU-A9 as a potential therapeutic agent for pancreatic cancer thus appears warrented.

Santamarine Inhibits NF-кB and STAT3 Activation and Induces Apoptosis in HepG2 Liver Cancer Cells via Oxidative Stress

Sesquiterpene lactones have long been used in traditional Chinese medicines to treat inflammatory diseases. Recently, sesquiterpene lactone family compounds have been recognized as potential anticancer agents. Thus, it is necessary to explore new sesquiterpene lactones and their antitumor mechanism for cancer treatments. In the present study, we have explored the potential anti-cancer activity of a novel sesquiterpene lactone compound “santamarine” (STM) in HepG2 cells. It inhibited proliferation and induced apoptosis dose-dependently with IC₅₀ ~ 70 μM. Induction of apoptosis was found to be linked with increased reactive oxygen species (ROS) generation, decreased activity of thioredoxin reductase (TrxR), glutathione (GSH) depletion, mitochondrial membrane potential (ΔΨm) dissipation, Bcl-2 family proteins modulation, cytochrome c release, caspases-9, -8 and -3 activation and PARP cleavage. Further mechanistic study demonstrated that STM inhibited the constitutive and TNF-α-induced translocation of NF-кB into nucleus by decreasing phosphorylation of IkB-α. Moreover, STM inhibited STAT3 activation by decreasing phosphorylation at tyrosine705. NAC pretreatment reversed the effect of STM-mediated cell death, NF-кB inhibition and blockage of STAT3 activity, indicating the involvement of oxidative stress in STM-mediated anticancer activity. Further studies are needed to explore the exact molecular mechanism of STM-induced apoptosis to develop it into a lead for treatment of liver cancer in future.

Methylisoindigo and Its Bromo-Derivatives Are Selective Tyrosine Kinase Inhibitors, Repressing Cellular Stat3 Activity, and Target CD133+ Cancer Stem Cells in PDAC

Indirubin is an active component of the herbal ingredient ‘Danggui Longhui wan’, which was used for the treatment of inflammation and chronic myeloid leukemia in China. The recent study showed its derivative methylisoindigo (also known as meisoindigo) preferentially targeting cancer stem cells (CSCs) in interference with AMPK and LKB1, the cellular metabolic sensors. In this study, we screened the effect of meisoindigo on a panel of 300 protein kinases and found that it selectively inhibited Stat3-associated tyrosine kinases and further confirmed its activity in cell based assays. To gain a deeper insight into the structure–activity relationship we produced 7 bromo-derivatives exhausting the accessible positions on the bisindole backbone except for in the 4-position due to the space limitation. We compared their anti-proliferative effects on tumor cells. We found that 6-bromomeisoindigo showed improved toxicity in company with increased Stat3 inhibition. Moreover, we detected that 6-bromomeisoindigo induced apoptosis of 95% of CD133+ pancreatic cancer cells. Considering that CD133 is a common marker highly expressed in a range of CSCs, our results imply the potential application of 6-bromomeisoindigo for the treatment of CSCs in different types of cancers.

Deoxyelephantopin and Isodeoxyelephantopin as Potential Anticancer Agents with Effects on Multiple Signaling Pathways

Cancer is the 2nd leading cause of death worldwide. The development of drugs to target only one specific signaling pathway has limited therapeutic success. Developing chemotherapeutics to target multiple signaling pathways has emerged as a new prototype for cancer treatment. Deoxyelephantopin (DET) and isodeoxyelephantopin (IDET) are sesquiterpene lactone components of “Elephantopus scaber and Elephantopus carolinianus”, traditional Chinese medicinal herbs that have long been used as folk medicines to treat liver diseases, diabetes, diuresis, bronchitis, fever, diarrhea, dysentery, cancer, and inflammation. Recently, the anticancer activity of DET and IDET has been widely investigated. Here, our aim is to review the current status of DET and IDET, and discuss their anticancer activity with specific emphasis on molecular targets and mechanisms used by these compounds to trigger apoptosis pathways which may help to further design and conduct research to develop them as lead therapeutic drugs for cancer treatments. The literature has shown that DET and IDET induce apoptosis through multiple signaling pathways which are deregulated in cancer cells and suggested that by targeting multiple pathways simultaneously, these compounds could selectively kill cancer cells. This review suggests that DET and IDET hold promising anticancer activity but additional studies and clinical trials are needed to validate and understand their therapeutic effect to develop them into potent therapeutics for the treatment of cancer.

Identification of a Water-Soluble Indirubin Derivative as Potent Inhibitor of Insulin-like Growth Factor 1 Receptor through Structural Modification of the Parent Natural Molecule

Indirubins have been identified as potent ATP-competitive protein kinase inhibitors. Structural modifications in the 5- and 3'-position have been extensively investigated, but the impact of substituents in 5'-position is not equally well-studied. Here, we report the synthesis of new indirubin 3'- and 5'-derivatives in the search of water-soluble indirubins by introducing basic centers. Antiproliferative activity of all compounds in tumor cells was evaluated along with kinase inhibition of selected compounds. The results show the 3'-position to tolerate large substituents without compromising activity, whereas bulk and rigid substituents in 5'-position appear unfavorable. Screening molecular targets of water-soluble 3'-oxime ethers revealed 6ha as preferential inhibitor of insulin-like growth factor 1 receptor (IGF-1R) in a panel of 22 protein kinases and in cells. Consistently, 6ha inhibited tumor cell growth in the NCI 60 cell line panel and induced apoptosis. The results indicate that the 5'-position provides limited space for chemical modifications and identify 6ha as a potent water-soluble indirubin-based IGF-1R inhibitor.

Induction of cell death in pancreatic ductal adenocarcinoma by indirubin 3'-oxime and 5-methoxyindirubin 3'-oxime in vitro and in vivo

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with a poor prognosis. To identify potential effective therapeutic drugs for PDAC, we established a screening system based on spheroid formation using 170#3 mouse PDAC cells with or without fibroblasts. We found that indirubin 3'-oxime (Indox) and 5-methoxyindirubin 3'-oxime (5MeOIndox) inhibited PDAC cell proliferation. Furthermore, PDAC xenograft growth was also inhibited in BALB/c nu/nu mice after administration of Indox and 5MeOIndox. Both phosphorylated CDK1 and cyclin B1 levels in 170#3 cells were significantly reduced by treatment with Indox and 5MeOIndox in vitro and in vivo. Cell cycle analysis revealed that 5MeOIndox, but not Indox, induced G2/M arrest. Annexin V-propidium iodide double-staining analysis demonstrated that Indox induced abundant non-apoptotic cell death of 170#3 cells, while 5MeOIndox predominantly induced early apoptosis, indicating that the cytotoxicity of 5MeOIndox is lower than that of Indox. These results suggest that one mechanism of 5MeOIndox is to induce G2/M arrest of PDAC cells via inhibition of CDK1/cyclin B1 levels, thereby leading to apoptosis. Our findings suggest 5MeOIndox as a potential useful anticancer agent in PDAC.

Identification of novel inverse agonists of estrogen-related receptors ERRγ and ERRβ

Estrogen-related receptors (ERRs, α, β, and γ) are orphan nuclear receptors most closely related in sequence to estrogen receptors (ERα and ERβ). Much attention has been paid recently to the functions of ERRs for their potential roles as new therapeutic targets implicated in the etiology of metabolic disorders. While no endogenous ligand has been identified for any of the ERR isoforms to date, the potential for using synthetic small molecules to modulate their activity has been demonstrated. In the present study, a series of novel inverse agonists of ERRγ and ERRβ were synthesized using regio- and stereo-specific direct substitution of triarylethylenes. These compounds were evaluated for their ability to modulate the activities of ERRs. The rational directed substitution approach and extensive SAR studies resulted in the discovery of compound 4a (DY40) as the most potent ERRγ inverse agonist described to date with mixed ERRγ/ERRβ functional activities, which potently suppressed the transcriptional functions of ERRγ with IC₅₀=0.01μM in a cell-based reporter gene assay and antagonized ERRγ with a potency approximately 60 times greater than its analog Z-4-OHT (Z-4-hydroxytamoxifen). In addition, compound 3h (DY181) was identified as the most potent synthetic inverse agonist for the ERRβ that exhibited excellent selectivity over ERRα/γ in functional assays. This selectivity was also supported by computational docking models that suggest DY181 forms more extensive hydrogen bound network with ERRβ which should result in higher binding affinity on ERRβ over ERRγ.

TEMPO-catalyzed oxidative homocoupling route to 3,2′-biindolin-2-ones via an indolin-3-one intermediate

A combinative C2 arylation and C3 carbonylation of free indoles using TEMPO catalysis and silver oxidant under non-directing group conditions was successful demonstrated. This new methodology is both atom and step efficient and is applicable to a broad scope of substrates.

Signal transducer and activator of transcription 3 as a therapeutic target for cancer and the tumor microenvironment

Signal transducer and activator of transcription 3 (STAT3) is a cytoplasmic transcription factor that modulates the transcription of a variety of genes to regulate important biological functions, including cell proliferation, differentiation, survival, angiogenesis, and immune response. Constitutive activation of STAT3 is important in oncogenic signaling and occurs at high frequency in human cancers, including diverse solid tumors and hematologic malignancies. Moreover, it is associated with a poor prognosis. The tumor microenvironment has recently been recognized as a key condition for cancer progression, invasion, angiogenesis, metastasis, and drug resistance by activation of STAT3 signaling. Therefore, understanding the biology associated with STAT3-mediated signaling cascades in the tumor microenvironment may offer the therapeutic potential to treat human cancers. This review presents an overview of the critical roles of STAT3 in the tumor microenvironment related to cancer biology and discusses recent advancements in the development of anticancer drugs that therapeutically inhibit STAT3 signaling cascades.

Novel FXR (farnesoid X receptor) modulators: Potential therapies for cholesterol gallstone disease

Metabolic disorders such as diabetes are known risk factors for developing cholesterol gallstone disease (CGD). Cholesterol gallstone disease is one of the most prevalent digestive diseases, leading to considerable financial and social burden worldwide. Ursodeoxycholic acid (UDCA) is the only bile acid drug approved by FDA for the non-surgical treatment of gallstones. However, the molecular link between UDCA and CGD is unclear. Previous data suggest that the farnesoid X receptor (FXR), a bile acid nuclear receptor, may protect against the development of CGD. In studies aimed at identifying the role of FXR, we recently identify a novel chemical tool, 6EUDCA (6-αethyl-ursodeoxycholic acid), a synthetic derivative of UDCA, for studying FXR. We found that 6EUDCA binds FXR stronger than UDCA in a TR-FRET binding assay. This result was supported by computational docking models that suggest 6EUDCA forms a more extensive hydrogen bound network with FXR. Interestingly, neither compound could activate FXR target genes in human nor mouse liver cells, suggesting UDCA and 6EUDCA activate non-genomic signals in an FXR-dependent manner. Overall these studies may lead to the identification of a novel mechanism by which bile acids regulate cell function, and 6EUDCA may be an effective targeted CGD therapeutic.

Small-molecule induction of phospho-eIF4E sumoylation and degradation via targeting its phosphorylated serine 209 residue

As phospho-eIF4E (p-eIF4E), unlike total eIF4E (t-eIF4E) essential for normal cells, is specifically required by cancer cells, it is an attractive, yet unrealized, target for anti-tumor intervention. Here we identify a small molecule, homoharringtonine (HHT), that antagonizes p-eIF4E function and eradicates acute myeloid leukemia (AML) expressing high level of p-eIF4E in vitro and in vivo. HHT selectively reduces p-eIF4E levels of leukemia cells without affecting t-eIF4E. HHT targets the phosphorylated serine 209 residue of p-eIF4E and induces p-eIF4E oligomerization, which enhances its interaction with the small ubiquitin-like protein modifier (SUMO)-conjugating enzyme UBC9, resulting in proteasome-dependent degradation of p-eIF4E via SUMO2/3-mediated SUMOylation. These results suggest that the phosphorylated serine 209 residue of p-eIF4E might be a potential target for developing small molecule-based new therapies for leukemia.

Strategies and Approaches of Targeting STAT3 for Cancer Treatment

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that regulates the expression of genes related to cell cycle, cell survival, and immune response associated with cancer progression and malignancy in a number of cancer types. Once activated, STAT3 forms a homodimer and translocates to the nucleus where it binds DNA promoting the translation of target genes associated with antiapoptosis, angiogenesis, and invasion/migration. In normal cells, levels of activated STAT3 remain transient; however, STAT3 remains constitutively active in approximately 70% of human solid tumors. The pivotal role of STAT3 in tumor progression has promoted a campaign in drug discovery to identify small molecules that disrupt the function of STAT3. A range of approaches have been used to identify novel small molecule inhibitors of STAT3, including high-throughput screening of chemical libraries, computational-based virtual screening, and fragment-based design strategies. The most common approaches in targeting STAT3 activity are either via the inhibition of tyrosine kinases capable of phosphorylating and thereby activating STAT3 or by preventing the formation of functional STAT3 dimers through disruption of the SH2 domains. However, the targeting of the STAT3 DNA-binding domain and disruption of binding of STAT3 to its DNA promoter have not been thoroughly examined, mainly due to the lack of adequate assay systems. This review summarizes the development of STAT3 inhibitors organized by the approach used to inhibit STAT3, the current inhibitors of each class, and the assay systems used to evaluate STAT3 inhibition and offers an insight into future approaches for small molecule STAT3 inhibitor development.

The GRIM-19 plays a vital role in shrimps' responses to Vibrio alginolyticus

GRIM-19 (gene associated with retinoid-interferon-induced mortality 19), a novel cell death regulatory gene, plays important roles in cell apoptosis, mitochondrial respiratory chain and immune response. It has been reported to interact physically with STAT3 and inhibit STAT3-dependent signal transduction. In this study, a new GRIM-19 gene, which is a 789-bp gene encoding a 149 amino acids protein, is identified and characterized from Litopenaeus vannamei. The tissue distribution patterns showed that LvGRIM-19 was widely expressed in all examined tissues, with the highest expression in muscle. Quantitative real-time PCR revealed that LvGRIM-19 was down-regulated in hepatopancreas after infection with the Vibrio alginolyticus. Knockdown of LvGRIM-19 by RNA interference resulted in a lower mortality of L. vannamei under V. alginolyticus infection, as well as an enhancement in the protein expression of STAT gene and JAK gene. V. alginolyticus infection caused an increase apoptotic cell ratio and ROS production of L. vannamei, while LvGRIM-19 silenced shrimps showed significantly lower than GFP group. Our results suggest that the GRIM-19 plays a vital role in shrimps' responses to V. alginolyticus. Interferenced LvGRIM-19 treatment during V. alginolyticus infection could increase 12 h survival rate, which might indicated that LvGRIM-19 is closely related to death of shrimps.

Zeylenone promotes apoptosis in chronic myelogenous leukemia-derived K562 cells by a mechanism involving Jak2 and Src kinase

Chronic myelogenous leukemia (CML) is a hematopoietic malignancy caused by the constitutive activation of BCR–ABL tyrosine kinase.

Single agent BMS-911543 Jak2 inhibitor has distinct inhibitory effects on STAT5 signaling in genetically engineered mice with pancreatic cancer

The Jak/STAT pathway is activated in human pancreatic ductal adenocarcinoma (PDAC) and cooperates with mutant Kras to drive initiation and progression of PDAC in murine models. We hypothesized that the small-molecule Jak2 inhibitor (BMS-911543) would elicit anti-tumor activity against PDAC and decrease immune suppressive features of the disease. We used an aggressive genetically engineered PDAC model with mutant KrasG12D, tp53R270H, and Brca1 alleles (KPC-Brca1 mice). Mice with confirmed tumor burden were treated orally with vehicle or 30 mg/kg BMS-911543 daily for 14 days. Histologic analysis of pancreata from treated mice revealed fewer foci of adenocarcinoma and significantly decreased Ki67+ cells versus controls. In vivo administration of BMS-911543 significantly reduced pSTAT5 and FoxP3 positive cells within the pancreas, but did not alter STAT3 phosphorylation. Continuous dosing of KPC-Brca1 mice with BMS-911543 resulted in a median survival of 108 days, as compared to a median survival of 87 days in vehicle treated animals, a 23% increase (p = 0.055). In vitro experiments demonstrated that PDAC cell lines were poorly sensitive to BMS-911543, requiring high micromolar concentrations to achieve targeted inhibition of Jak/STAT signaling. Similarly, BMS-911543 had little in vitro effect on the viability of both murine and human PDAC-derived stellate cell lines. However, BMS-911543 potently inhibited phosphorylation of pSTAT3 and pSTAT5 at low micromolar doses in human PBMC and reduced in vitro differentiation of Foxp3+ T regulatory cells. These results indicate that single agent Jak2i deserves further study in preclinical models of PDAC and has distinct inhibitory effects on STAT5 mediated signaling.

Indirubin derivatives: a patent review (2010 - present)

INTRODUCTION

Indirubins are bisindole alkaloids naturally occurring in indigo-bearing plants or in mollusks from the Muricidae family. They belong to the rather small family of indigoids, which has nevertheless found an extreme importance in the fields of dyes and medicinal chemistry. Indirubin has been found to be the active ingredient of a traditional Chinese Medicine used to treat the symptoms of leukemia. Further biological explorations revealed the ability of indirubin to bind cyclin-dependent kinases and 6-bromoindirubin, extracted from mollusks, to bind glycogen synthase kinase-3. The high affinity displayed by the two natural products has opened a vast field of research and triggered the development of hundred of derivatives with biological activities.

AREAS COVERED

The traditional use of indirubin for the treatment of leukemia has prompted different research groups to study the cytotoxic effect of indirubin derivatives on both solid tumors and leukemia. Moreover, the affinity of indirubins for kinases also allowed the exploration of their activity towards stem cells.

EXPERT OPINION

The derivatives presented are in accordance with first discoveries and establish the close relation between activity and kinase inhibition. New derivatives have been patented and new interferences in signaling pathways are described. However, few in vivo studies have been performed and more efficient solutions are needed to unravel the major issue of solubility.

Induction of atypical cell death in thyroid carcinoma cells by the indirubin derivative 7-bromoindirubin-3'-oxime (7BIO)

BACKGROUND

The indirubin derivative 7-bromoindirubin-3'-oxime (7BIO) has already shown anticancer properties by causing cell death in some tumour cell lines and may be a new therapeutic option for treatment-resistant tumour cells. Since dedifferentiated and anaplastic thyroid carcinomas do not take up radioiodine and are insensitive to chemotherapeutic treatment and external radiation, direct cell death induction in these tumour cells may be a promising approach. We thus investigated the effect of 7BIO on thyroid carcinoma cell lines of different histological origins and characterized the type of cell death induction by 7BIO.

METHODS

Cell viability was measured with MTT assay. Cell death was analysed by caspase 3/7 activity, lactate dehydrogenase liberation, caspase cleavage products, DNA fragmentation, cell cycle phase distribution and LC3B analysis.

RESULTS

After 7BIO treatment, cell viability was reduced in all 14 thyroid carcinoma cell lines investigated. Treated cells showed DNA fragmentation, cell cycle arrest and lactate dehydrogenase liberation but no LC3B cleavage. Caspase activation following 7BIO treatment was found in five of six cell lines investigated. Interestingly, inhibition of caspases had no effect on viability of the cells after 7BIO incubation.

CONCLUSIONS

Our results indicate that 7BIO efficiently killed dedifferentiated thyroid carcinoma cells. It induced a non-classical kind of cell death that was caspase-independent and includes DNA fragmentation. 7BIO and related indirubin components thus may have value as a new therapeutic option for dedifferentiated thyroid cancer irrespective of the exact target molecules and the kind of cell death they induce.

Indirubin and Indirubin Derivatives for Counteracting Proliferative Diseases

Indirubin is the active component of Danggui Longhui Wan, a traditional Chinese medicine formulation. The encouraging clinical results from the 1980s obtained in chronic myelocytic leukemia patients treated with indirubin stimulated numerous studies on this compound. These investigations explored the use of indirubin in different types of cancer and reported the synthesis of novel derivatives with improved chemical and pharmacokinetic properties. In this paper, we review the impressive progress that has been made in elucidating the mechanistic understanding of how indirubin and its derivatives affect physiological and pathophysiological processes, mainly by inhibition of cell proliferation and induction of cell death. Furthermore, we survey the therapeutic use of these compounds in combating proliferative diseases such as cancer, restenosis, and psoriasis.

MYC in pancreatic cancer: novel mechanistic insights and their translation into therapeutic strategies

Owing to its aggressiveness, late detection and marginal therapeutic accessibility, pancreatic ductal adenocarcinoma (PDAC) remains a most challenging malignant disease. Despite scientific progress in the understanding of the mechanisms that underly PDAC initiation and progression, the successful translation of experimental findings into effective new therapeutic strategies remains a largely unmet need. The oncogene MYC is activated in many PDAC cases and is a master regulator of vital cellular processes. Excellent recent studies have shed new light on the tremendous functions of MYC in cancer and identified inhibition of MYC as a likewise beneficial and demanding effort. This review will focus on mechanisms that contribute to deregulation of MYC expression in pancreatic carcinogenesis and progression and will summarize novel biological findings from recent in vivo models. Finally, we provide a perspective, how regulation of MYC in PDAC may contribute to the development of new therapeutic approaches.

Caveolin-1 is Associated with Tumor Progression and Confers a Multi-Modality Resistance Phenotype in Pancreatic Cancer

Caveolin-1 (Cav-1) is a 21 kDa protein enriched in caveolae, and has been implicated in oncogenic cell transformation, tumorigenesis, and metastasis. We explored roles for Cav-1 in pancreatic cancer (PC) prognostication, tumor progression, resistance to therapy, and whether targeted downregulation could lead to therapeutic sensitization. Cav-1 expression was assessed in cell lines, mouse models, and patient samples, and knocked down in order to compare changes in proliferation, invasion, migration, response to chemotherapy and radiation, and tumor growth. We found Cav-1 is overexpressed in human PC cell lines, mouse models, and human pancreatic tumors, and is associated with worse tumor grade and clinical outcomes. In PC cell lines, disruption/depletion of caveolae/Cav-1 reduces proliferation, colony formation, and invasion. Radiation and chemotherapy up-regulate Cav-1 expression, while Cav-1 depletion induces both chemosensitization and radiosensitization through altered apoptotic and DNA repair signaling. In vivo, Cav-1 depletion significantly attenuates tumor initiation and growth. Finally, Cav-1 depletion leads to altered JAK/STAT, JNK, and Src signaling in PC cells. Together, higher Cav-1 expression is correlated with worse outcomes, is essential for tumor growth and invasion (both in vitro and in vivo), is responsible for promoting resistance to therapies, and may serve as a prognostic/predictive biomarker and target in PC.