Sorafenib inhibits STAT3 activation to enhance TRAIL-mediated apoptosis in human pancreatic cancer cells

MCL1 inhibition: a promising approach to augment the efficacy of sorafenib in NSCLC through ferroptosis induction

Ferroptosis, an iron-dependent form of regulated cell death, plays a crucial role in modulating the therapeutic response in non-small cell lung cancer (NSCLC) patients. Studies have identified the signal transducer and activator of transcription 3 (STAT3) and myeloid cell leukemia-1 (MCL1) as potential targets for sorafenib, which exhibits activities in inducing ferroptosis. However, the role of STAT3-MCL1 axis in sorafenib-induced ferroptosis in NSCLC is still unclear. This study provided evidence that ferroptosis is a critical driver of sorafenib-induced cell death in NSCLC, supported by the accumulation of lipid peroxidation products, indicative of oxidative stress-induced cell death. Additionally, both in vitro and in vivo experiments showed that ferroptosis contributed to a significant portion of the anti-cancer effects elicited by sorafenib in NSCLC. The noticeable accumulation of lipid peroxidation products in sorafenib-treated mice underscored the significance of ferroptosis as a contributing factor to the therapeutic response of sorafenib in NSCLC. Furthermore, we identified the involvement of the STAT3/MCL1 axis in sorafenib-induced antitumor activity in NSCLC. Mechanistically, sorafenib inhibited endogenous STAT3 activation and downregulated MCL1 protein expression, consequently unleashing the ferroptosis driver BECN1 from the BECN1-MCL1 complex. Conversely, there is an augmented association of BECN1 with the catalytic subunit of system Xc-, SLC7A11, whose activity to import cystine and alleviate lipid peroxidation is hindered upon its binding with BECN1. Notably, we found that MCL1 upregulation correlated with ferroptosis resistance in NSCLC upon sorafenib treatment. Our findings highlight the importance of sorafenib-triggered ferroptosis in NSCLC and offer a novel strategy to treat advanced NSCLC patients: by downregulating MCL1 and, in turn, predispose NSCLC cells to ferroptosis.

5-Methoxytryptophan enhances the sensitivity of sorafenib on the inhibition of proliferation and metastasis for lung cancer cells

BACKGROUND

Lung cancer is a leading cause of cancer-related mortality worldwide, and effective therapies are limited. Lung cancer is a leading cause of cancer-related mortality worldwide with limited effective therapy. Sorafenib is a multi-tyrosine kinase inhibitor frequently used to treat numerous types of malignant tumors. However, it has been demonstrated that sorafenib showed moderate antitumor activity and is associated with several side effects in lung cancer, which restricted its clinical application. This study aimed to examine the antitumor effect of the combination treatment of sorafenib and 5-methoxytryptophan (5-MTP) on cell growth and metastasis of Lewis lung carcinoma (LLC) cells.

METHOD

The anticancer effect of the combination treatment of sorafenib and 5-MTP was determined through cytotoxicity assay and colony forming assays. The mechanism was elucidated using flow cytometry and western blotting. Wound healing and Transwell assays were conducted to evaluate the impact of the combination treatment on migration and invasion abilities. An in vivo model was employed to analyze the effect of the combination treatment on the tumorigenic ability of LLC cells.

RESULT

Our results demonstrated that the sorafenib and 5-MTP combination synergistically reduced viability and proliferation compared to sorafenib or 5-MTP treatment alone. Reduction of cyclin D1 expression was observed in the sorafenib alone or combination treatments, leading to cell cycle arrest. Furthermore, the sorafenib-5-MTP combination significantly increased the inhibitory effect on migration and invasion of LLC cells compared to the single treatments. The combination also significantly downregulated vimentin and MMP9 levels, contributing to the inhibition of metastasis. The reduction of phosphorylated Akt and STAT3 expression may further contribute to the inhibitory effect on proliferation and metastasis. In vivo, the sorafenib-5-MTP combination further reduced tumor growth and metastasis compared to the treatment of sorafenib alone.

CONCLUSIONS

In conclusion, our data indicate that 5-MTP sensitizes the antitumor activity of sorafenib in LLC cells in vitro and in vivo, suggesting that sorafenib-5-MTP has the potential to serve as a therapeutic option for patients with lung cancer.

Consideration of SHP-1 as a Molecular Target for Tumor Therapy

Abnormal activation of receptor tyrosine kinases (RTKs) contributes to tumorigenesis, while protein tyrosine phosphatases (PTPs) contribute to tumor control. One of the most representative PTPs is Src homology region 2 (SH2) domain-containing phosphatase 1 (SHP-1), which is associated with either an increased or decreased survival rate depending on the cancer type. Hypermethylation in the promoter region of PTPN6, the gene for the SHP-1 protein, is a representative epigenetic regulation mechanism that suppresses the expression of SHP-1 in tumor cells. SHP-1 comprises two SH2 domains (N-SH2 and C-SH2) and a catalytic PTP domain. Intramolecular interactions between the N-SH2 and PTP domains inhibit SHP-1 activity. Opening of the PTP domain by a conformational change in SHP-1 increases enzymatic activity and contributes to a tumor control phenotype by inhibiting the activation of the Janus kinase/signal transducer and activator of transcription (JAK/STAT3) pathway. Although various compounds that increase SHP-1 activation or expression have been proposed as tumor therapeutics, except sorafenib and its derivatives, few candidates have demonstrated clinical significance. In some cancers, SHP-1 expression and activation contribute to a tumorigenic phenotype by inducing a tumor-friendly microenvironment. Therefore, developing anticancer drugs targeting SHP-1 must consider the effect of SHP-1 on both cell biological mechanisms of SHP-1 in tumor cells and the tumor microenvironment according to the target cancer type. Furthermore, the use of combination therapies should be considered.

Emerging Potential Mechanism and Therapeutic Target of Ferroptosis in PDAC: A Promising Future

Pancreatic cancer (PC) is a devastating malignant tumor of gastrointestinal (GI) tumors characterized by late diagnosis, low treatment success and poor prognosis. The most common pathological type of PC is pancreatic ductal adenocarcinoma (PDAC), which accounts for approximately 95% of PC. PDAC is primarily driven by the Kirsten rat sarcoma virus (KRAS) oncogene. Ferroptosis was originally described as ras-dependent cell death but is now defined as a regulated cell death caused by iron accumulation and lipid peroxidation. Recent studies have revealed that ferroptosis plays an important role in the development and therapeutic response of tumors, especially PDAC. As the non-apoptotic cell death, ferroptosis may minimize the emergence of drug resistance for clinical trials of PDAC. This article reviews what has been learned in recent years about the mechanisms of ferroptosis in PDAC, introduces the association between ferroptosis and the KRAS target, and summarizes several potential strategies that are capable of triggering ferroptosis to suppress PDAC progression.

Sorafenib suppresses radioresistance and synergizes radiotherapy-mediated CD8+ T cell activation to eradicate hepatocellular carcinoma

Radiotherapy (RT) is applied to eradicate tumors in the clinic. However, hepatocellular carcinoma (HCC) exhibits resistance against RT. It is demonstrated that RT directly inhibits tumor growth but which induces type I interferons (IFNs) expression to phosphorylate STATs and increase STATs-downstream PD-L1 levels in the survival tumor cells. Since sorafenib is capable of suppressing STATs, we, therefore, hypothesize that sorafenib suppresses IFNs-mediated radioresistance and PD-L1 in the residual tumor cells and may synergistically enhance RT-mediated reactivation of CD8⁺ T immunological activity to eradicate HCC cells. We found that combined RT, sorafenib, and PBMCs significantly suppress the colony formation in the HCC cells, whereas CD8⁺ T cells expressed high granzyme B (GZMB) and perforin (PRF1) in co-cultured with RT-treated HCC cells. We demonstrated RT significantly inhibited HCC cell viability but induced IFNα and IL-6 expression in the RT-treated HCC cells, resulting in immune checkpoint PD-L1 and anti-apoptosis MCL1 and BCL2 overexpression in the non-RT HCC cells. We found that sorafenib decreased RT-PLC5 medium (RT-PLC5-m)-mediated cell growth by suppressing IFNα- and IL-6-mediated STAT1 and STAT3 phosphorylation. Sorafenib also reduced IFNα-mediated PD-L1 levels in HCC cells. Meanwhile, RT-PLC5-m reactivated CD8⁺ T cells and non-CD8⁺ PBMCs, resulting in high IFNγ and IL-2 levels in CD8⁺ T cells, and cytokines IFNα, IFNγ, IL-2, and IL-6 in non-CD8⁺ PBMCs. Particularly, CD8⁺ T cells expressed higher GZMB and PRF1 and non-CD8⁺ PBMCs expressed higher IFNα, IFNγ, IL-2, IL-6, CXCL9, and CXCL10 in co-cultured with RT-treated HCC cells compared to parental cells. Although we demonstrated that sorafenib slightly inhibited RT-mediated GZMB and PRF1 expression in CD8⁺ T cells, and cytokines levels in non-CD8⁺ PBMCs. Based on sorafenib significantly suppressed IFNα- and IL-6-mediated radioresistance and PD-L1 expression, we demonstrated that sorafenib synergized RT and immune surveillance for suppressing PLC5 cell viability in vitro. In conclusion, this study revealed that RT induced IFNα and IL-6 expression to phosphorylate STAT1 and STAT3 by autocrine and paracrine effect, leading to radioresistance and PD-L1 overexpression in HCC cells. Sorafenib not only suppressed IFNα- and IL-6-mediated PLC5 cell growth but also inhibited IFNα-mediated PD-L1 expression, synergistically enhancing RT-mediated CD8⁺ T cell reactivation against HCC cells.

Sorafenib Chemosensitization by Caryophyllane Sesquiterpenes in Liver, Biliary, and Pancreatic Cancer Cells: The Role of STAT3/ABC Transporter Axis

A combination of anticancer drugs and chemosensitizing agents has been approached as a promising strategy to potentiate chemotherapy and reduce toxicity in aggressive and chemoresistant cancers, like hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), and pancreatic ductal adenocarcinoma (PDAC). In the present study, the ability of caryophyllane sesquiterpenes to potentiate sorafenib efficacy was studied in HCC, CCA, and PDAC cell models, focusing on the modulation of STAT3 signaling and ABC transporters; tolerability studies in normal cells were also performed. Results showed that the combination of sorafenib and caryophyllane sesquiterpenes synergized the anticancer drug, especially in pancreatic Bx-PC3 adenocarcinoma cells; a similar trend, although with lower efficacy, was found for the standard ABC transporter inhibitors. Synergistic effects were associated with a modulation of MDR1 (or Pgp) and MRP transporters, both at gene and protein level; moreover, activation of STAT3 cascade and cell migration appeared significantly affected, suggesting that the STAT3/ABC-transporters axis finely regulated efficacy and chemoresistance to sorafenib, thus appearing as a suitable target to overcome drawbacks of sorafenib-based chemotherapy in hepato-biliary-pancreatic cancers. Present findings strengthen the interest in caryophyllane sesquiterpenes as chemosensitizing and chemopreventive agents and contribute to clarifying drug resistance mechanisms in HCC, CCA, and PDAC cancers and to developing possible novel therapeutic strategies.

DRP1 Promotes BRAFV600E-Driven Tumor Progression and Metabolic Reprogramming in Colorectal Cancer

Background

Mitochondria are highly dynamic organelles which remain in a continuous state of fission/ fusion dynamics to meet the metabolic needs of a cell. However, this fission/fusion dynamism has been reported to be dysregulated in most cancers. Such enhanced mitochondrial fission is demonstrated to be positively regulated by some activating oncogenic mutations; such as those of KRAS (Kristen rat sarcoma viral oncogene homologue) or BRAF (B- rapidly accelerated fibrosarcoma), thereby increasing tumor progression/ chemotherapeutic resistance and metabolic deregulation. However, the underlying mechanism(s) are still not clear, thus highlighting the need to further explore possible mechanism(s) of intervention. We sought to investigate how BRAF^V600E driven CRC (colorectal cancer) progression is linked to mitochondrial fission/fusion dynamics and whether this window could be exploited to target CRC progression.

Methods

Western blotting was employed to study the differences in expression levels of key proteins regulating mitochondrial dynamics, which was further confirmed by confocal microscopy imaging of mitochondria in endogenously expressing BRAF^WT and BRAF^V600E CRC cells. Proliferation assays, soft agar clonogenic assays, glucose uptake/lactate production, ATP/ NADPH measurement assays were employed to study the extent of carcinogenesis and metabolic reprograming in BRAF^V600E CRC cells. Genetic knockdown (shRNA/ siRNA) and/or pharmacologic inhibition of Dynamin related protein1/Pyruvate dehydrogenase kinase1 (DRP1/PDK1) and/or BRAF^V600E were employed to study the involvement and possible mechanism of these proteins in BRAF^V600E driven CRC. Statistical analyses were carried out using Graph Pad Prism v 5.0, data was analyzed by unpaired t-test and two-way ANOVA with appropriate post hoc tests.

Results

Our results demonstrate that BRAF^V600E CRC cells have higher protein levels of mitochondrial fission factor- DRP1/pDRP1^S616 leading to a more fragmented mitochondrial state compared to those harboring BRAF^WT . This fragmented mitochondrial state was found to confer glycolytic phenotype, clonogenic potential and metastatic advantage to cells harboring BRAF^V600E . Interestingly, such fragmented mitochondrial state seemed positively regulated by mitochondrial PDK1 as observed through pharmacologic as well as genetic inhibition of PDK1.

Conclusion

In conclusion, our data suggest that BRAF^V600E driven colorectal cancers have fragmented mitochondria which confers glycolytic phenotype and growth advantage to these tumors, and such phenotype is dependent at least in part on PDK1- thus highlighting a potential therapeutic target.

Arsenic trioxide induces macrophage autophagy and atheroprotection by regulating ROS-dependent TFEB nuclear translocation and AKT/mTOR pathway

Inducing autophagy and inhibiting apoptosis may provide a therapeutic treatment for atherosclerosis (AS). For the treatment of progressive AS, arsenic trioxide (ATO) has been used to coat vascular stents. However, the effect of ATO on autophagy of macrophages is still unknown. Therefore, the aims of this study were to characterize the effects and the mechanism of actions of ATO on autophagy in macrophages. Our results showed that ATO-induced activation of autophagy was an earlier event than ATO-induced inhibition of the expression of apoptosis markers in macrophages and foam cells. Nuclear transcription factor EB (TFEB) prevents atherosclerosis by activating macrophage autophagy and promoting lysosomal biogenesis. Here, we report that ATO triggered the nuclear translocation of TFEB, which in turn promoted autophagy and autophagosome-lysosome fusion. Both the latter events were prevented by TFEB knockdown. Moreover, ATO decreased the p-AKT and p-mTOR in the PI3K/AKT/mTOR signaling pathway, thus inducing autophagy. Correspondingly, treatment with the autophagy inhibitor 3-methyladenine (3-MA) abolished the autophagy-inducing effects of ATO. Meanwhile, PI3K inhibitor (LY294002) and mTOR inhibitor (rapamycin) cooperated with ATO to induce autophagy. Furthermore, reactive oxygen species (ROS) were generated in macrophages after treatment with ATO. The ROS scavenger N-acetyl-1-cysteine (NAC) abolished ATO-induced nuclear translocation of TFEB, as well as changes in key molecules of the AKT/mTOR signaling pathway and downstream autophagy. More importantly, ATO promoted autophagy in the aorta of ApoE-/- mice and reduced atherosclerotic lesions in early AS, which were reversed by 3-MA treatment. In summary, our data indicated that ATO promoted ROS induction, which resulted in nuclear translocation of TFEB and inhibition of the PI3K/AKT/mTOR pathway. These actions ultimately promoted macrophage autophagy and reduced atherosclerotic lesions at early stages. These findings may provide a new perspective for the clinical treatment of early-stage atherosclerosis and should be further studied.

The role of cell signaling in the crosstalk between autophagy and apoptosis in the regulation of tumor cell survival in response to sorafenib and neratinib

The molecular mechanisms by which tumor cells survive or die following therapeutic interventions are complex. There are three broadly defined categories of cell death processes: apoptosis (Type I), autophagic cell death (Type II), and necrosis (Type III). In hematopoietic tumor cells, the majority of toxic stimuli cause these cells to undergo a death process called apoptosis; apoptosis specifically involves the cleavage of DNA into large defined pieces and their subsequent localization in vesicles. Thus, 'pure' apoptosis largely lacks inflammatory potential. In carcinomas, however, the mechanisms by which tumor cells ultimately die are considerably more complex. Although the machinery of apoptosis is engaged by toxic stimuli, other processes such as autophagy ("self-eating") and replicative cell death can lead to observations that do not simplistically correspond to any of the individual Type I-III formalized death categories. The 'hybrid' forms of cell death observed in carcinoma cells result in cellular materials being released into the extracellular space without packaging, which promotes inflammation, potentially leading to the accelerated re-growth of surviving tumor cells by macrophages. Drugs as single agents or in combinations can simultaneously initiate signaling via both apoptotic and autophagic pathways. Based on the tumor type and its oncogene drivers, as well as the drug(s) being used and the duration and intensity of the autophagosome signal, apoptosis and autophagy have the potential to act in concert to kill or alternatively that the actions of either pathway can act to suppress signaling by the other pathway. And, there also is evidence that autophagic flux, by causing lysosomal protease activation, with their subsequent release into the cytosol, can directly mediate killing. This review will discuss the interactive biology between apoptosis and autophagy in carcinoma cells. Finally, the molecular actions of the FDA-approved drugs neratinib and sorafenib, and how they enhance both apoptotic and toxic autophagic processes, alone or in combination with other agents, is discussed in a bench-to-bedside manner.

Shp1 in Solid Cancers and Their Therapy

Shp1 is a cytosolic tyrosine phosphatase that regulates a broad range of cellular functions and targets, modulating the flow of information from the cell membrane to the nucleus. While initially studied in the hematopoietic system, research conducted over the past years has expanded our understanding of the biological role of Shp1 to other tissues, proposing it as a novel tumor suppressor gene functionally involved in different hallmarks of cancer. The main mechanism by which Shp1 curbs cancer development and progression is the ability to attenuate and/or terminate signaling pathways controlling cell proliferation, survival, migration, and invasion. Thus, alterations in Shp1 function or expression can contribute to several human diseases, particularly cancer. In cancer cells, Shp1 activity can indeed be affected by mutations or epigenetic silencing that cause failure of Shp1-mediated homeostatic maintenance. This review will discuss the current knowledge of the cellular functions controlled by Shp1 in non-hematopoietic tissues and solid tumors, the mechanisms that regulate Shp1 expression, the role of its mutation/expression status in cancer and its value as potential target for cancer treatment. In addition, we report information gathered from the public available data from The Cancer Genome Atlas (TCGA) database on Shp1 genomic alterations and correlation with survival in solid cancers patients.

A promising approach to develop nanostructured lipid carriers from solid lipid nanoparticles: preparation, characterization, cytotoxicity and nucleic acid binding ability

We aimed to develop nanostructured lipid carriers (NLCs) displaying similar characteristics - particle size, polydispersity index, and zeta potential - with the model solid lipid nanoparticles (SLNs) for better comparability. By considering the hydrophilic-lipophilic balance values of solid and liquid lipids, five out of six NLCs and eight out of eight cationic NLCs (cNLCs) were successfully prepared with similar characteristics to their precursor SLN and cationic SLNs (cSLNs), respectively. Among cationic formulations, two cSLNs containing different surfactant/co-surfactant concentrations (4% and 8% S/CoS; w/w) and their cNLC versions prepared with Labrafac lipophile WL 1349 (LWL) or Labrafac PG were selected to compare cytotoxicity, stability, and nucleic acid binding ability. All formulations are well-tolerated by L-929 cells, cSLNs being least toxic. The formulations containing 4% S/CoS had higher stability after 24-months. All nanoparticles formed complexes with pDNA (Binding ability: cNLCs > cSLNs). cSLN and LWL-cNLC containing 4% S/CoS showed the highest pDNA binding capacity in each group, and their spherical/oval shape was revealed by electron microscopy. However, they did not form complexes with siRNA. The developed approach has the potential to simplify the production of (c)NLCs having similar physicochemical properties with the optimum (c)SLN and may provide better insight for (c)SLN vs.

The Synergistic Cytotoxic Effect of Laser-Irradiated Gold Nanoparticles and Sorafenib Against the Growth of a Human Hepatocellular Carcinoma Cell Line

Gold nanoparticles are the most promising candidate in cancer treatment due to their physiochemical properties and increased use in photothermal therapy (PTT). In the present study, spherical gold nanoparticles (AuNPs) were synthesized using citrate reduction method. The particles were then characterized using UV-VIS spectroscopy and transmission electron microscope. A hepatocellular carcinoma cell line (HepG2) was incubated with sorafenib and/or non-irradiated or laser-irradiated AuNPs for 48 hrs. The cytotoxic effect of different treatment modalities was determined using MTT assay. Furthermore, apoptosis was determined by flow cytometry using annexin V/propidium iodide, as well as estimating the level of caspases. Results showed that AuNPs and sorafenib reduced HepG2 cell viability, and the cytotoxicity was associated with increased release of LDH in the culture medium. The recorded cytotoxicity was attributed to enhanced apoptosis as revealed by increased cellular caspases (3, 8 and 9), that was further confirmed by flow cytometry. The most notable cytotoxic effect was recorded when combining sorafenib with laser-irradiated AuNPs. In conclusion, a synergistic cytotoxic effect was observed between sorafenib and laser-irradiated AuNPs against the growth of HepG2, suggesting the potential substitution of large toxic doses of sorafenib by lower doses in combination with photothermal therapy.

Ligand-Free Estrogen Receptor α (ESR1) as Master Regulator for the Expression of CYP3A4 and Other Cytochrome P450 Enzymes in the Human Liver

Cytochrome P450 3A4 isoform (CYP3A4) transcription is controlled by hepatic transcription factors (TFs), but how TFs dynamically interact remains uncertain. We hypothesize that several TFs form a regulatory network with nonlinear, dynamic, and hierarchical interactions. To resolve complex interactions, we have applied a computational approach for estimating Sobol's sensitivity indices (SSI) under generalized linear models to existing liver RNA expression microarray data (GSE9588) and RNA-seq data from genotype-tissue expression (GTEx), generating robust importance ranking of TF effects and interactions. The SSI-based analysis identified TFs and interacting TF pairs, triplets, and quadruplets involved in CYP3A4 expression. In addition to known CYP3A4 TFs, estrogen receptor α (ESR1) emerges as key TF with the strongest main effect and as the most frequently included TF interacting partner. Model predictions were validated using small interfering RNA (siRNA)/short hairpin RNA (shRNA) gene knockdown and clustered regularly interspaced short palindromic repeats (CRISPR)-mediated transcriptional activation of ESR1 in biliary epithelial Huh7 cells and human hepatocytes in the absence of estrogen. Moreover, ESR1 and known CYP3A4 TFs mutually regulate each other. Detectable in both male and female hepatocytes without added estrogen, the results demonstrate a role for unliganded ESR1 in CYP3A4 expression consistent with unliganded ESR1 signaling reported in other cell types. Added estrogen further enhances ESR1 effects. We propose a hierarchical regulatory network for CYP3A4 expression directed by ESR1 through self-regulation, cross regulation, and TF-TF interactions. We also demonstrate that ESR1 regulates the expression of other P450 enzymes, suggesting broad influence of ESR1 on xenobiotics metabolism in human liver. Further studies are required to understand the mechanisms underlying role of ESR1 in P450 regulation. SIGNIFICANCE STATEMENT: This study focuses on identifying key transcription factors and regulatory networks for CYP3A4, the main drug metabolizing enzymes in liver. We applied a new computational approach (Sobol's sensitivity analysis) to existing hepatic gene expression data to determine the role of transcription factors in regulating CYP3A4 expression, and used molecular genetics methods (siRNA/shRNA gene knockdown and CRISPR-mediated transcriptional activation) to test these interactions in life cells. This approach reveals a robust network of TFs, including their putative interactions and the relative impact of each interaction. We find that ESR1 serves as a key transcription factor function in regulating CYP3A4, and it appears to be acting at least in part in a ligand-free fashion.

Myeloid maturation potentiates STAT3-mediated atypical IFN-γ signaling and upregulation of PD-1 ligands in AML and MDS

Interferon (IFN)-γ is the major mediator of anti-tumor immune responses; nevertheless, cancer cells use intrigue strategies to alter IFN-γ signaling and avoid elimination. Understanding the immune regulatory mechanisms employed by acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) cells upon exposure to IFN-γ is critical for development of immunotherapy and checkpoint blockade therapy approaches. This study aims to explore the influence of myeloid maturation on IFN-γ-induced PD-L1 and PD-L2 expression and on pro-leukemogenic transcription factor STAT3 signaling in AML and MDS. Stimulation of myeloid blasts’ maturation by all-trans retinoic acid (ATRA) or 1α,25-dihydroxyvitamin D3 (vitamin D) increased the CD11b⁺ fraction that expressed PD-1 ligands in response to IFN-γ. Intriguingly, STAT3 pathway was potently induced by IFN-γ and strengthened upon prolonged exposure. Nonetheless, STAT3-mediated atypical IFN-γ signaling appeared as a negligible factor for PD-L1 and PD-L2 expression. These negative influences of IFN-γ could be alleviated by a small-molecule inhibitor of STAT3, stattic, which also inhibited the upregulation of PD-L1. In conclusion, induction of myeloid maturation enhances the responsiveness of AML and MDS cells to IFN-γ. However, these malignant myeloid cells can exploit both STAT3 pathway and PD-1 ligands to survive IFN-γ-mediated immunity and maintain secondary immune resistance.

Targeting STAT3 signaling in kidney disease

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway is a multifaceted transduction system that regulates cellular responses to incoming signaling ligands. STAT3 is a central member of the JAK/STAT signaling cascade and has long been recognized for its increased transcriptional activity in cancers and autoimmune disorders but has only recently been in the spotlight for its role in the progression of kidney disease. Although genetic knockout and manipulation studies have demonstrated the salutary benefits of inhibiting STAT3 activity in several kidney disease models, pharmacological inhibition has yet to make it to the clinical forefront. In recent years, significant effort has been aimed at suppressing STAT3 activation for treatment of cancers, which has led to the development of a wide variety of STAT3 inhibitors, but only a handful have been tested in kidney disease models. Here, we review the detrimental role of dysregulated STAT3 activation in a variety of kidney diseases and the current progress in the treatment of kidney diseases with pharmacological inhibition of STAT3 activity.

Rho GTPase Activating Protein 24 (ARHGAP24) Regulates the Anti-Cancer Activity of Sorafenib Against Breast Cancer MDA-MB-231 Cells via the Signal Transducer and Activator of Transcription 3 (STAT3) Signaling Pathway

BACKGROUND STAT3 has emerged as a novel potential target for sorafenib, a multikinase inhibitor, in the context of cancer therapy. ARHGAP24 is a Rac-specific Rho GTPase-activating protein (Rho GAP), which can convert Rho GTPases to an inactive state. It has been proved to be an oncosuppressor protein in renal cancer. In the present study, we investigated its anti-cancer effect in breast cancer (BC). MATERIAL AND METHODS Quantitative real-time PCR (qRT-PCR) and Western blot analysis were performed to detect the expression of ARHGAP24 in clinical tissue samples. Then, BC MDA-MB-231 cells were virally transduced with ARHGAP24 silencing or overexpression lentiviral vectors in the absence or presence of sorafenib. Cell viability and metastatic ability were evaluated by using the Cell Counting Kit-8 (CCK-8) and Transwell assays. Proteins belonging to the STAT3 pathway were detected by Western blot. RESULTS ARHGAP24 decreased in BC tissues compared with the adjacent normal tissues. Forced expression of ARHGAP24 and sorafenib treatment significantly suppressed the viability, migration, and invasion of MDA-MB-231 cells. Conversely, elimination of the endogenous ARHGAP24 with shRNA promoted cell viability, migration, and invasion. The phosphorylation of STAT3 and the expression of MMP-2 and MMP-9 were attenuated by ARHGAP24 ectopic expression and sorafenib treatment. Furthermore, forced expression of ARHGAP24 significantly enhanced sorafenib-induced decrease of cell viability, migration, and invasion of MDA-MB-231 cells, while elimination of the endogenous ARHGAP24 with shRNA inhibited it. CONCLUSIONS ARHGAP24 can suppress the development of MDA-MB-231 cells via the STAT3 signaling pathway, and sorafenib inhibits cell viability, migration, invasion, and STAT3 activation in MDA-MB-231 cells through ARHGAP24.

Combined inhibition of the PI3K/mTOR/MEK pathway induces Bim/Mcl-1-regulated apoptosis in pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) progression and chemotherapy insensitivity have been associated with aberrant PI3K/mTOR/MEK signalling. However, cell death responses activated by inhibitors of these pathways can differ – contextually varying with tumour genetic background. Here, we demonstrate that combining the dual PI3K/mTOR inhibitor PF5212384 (PF384) and MEK inhibitor PD325901 (PD901) more effectively induces apoptosis compared with either agent alone, independent of KRAS mutational status in PDAC cell lines. Additionally, a non-caspase dependent decrease in cell viability upon PF384 treatment was observed, and may be attributed to autophagy and G0/G1 cell cycle arrest. Using reverse phase protein arrays, we identify key molecular events associated with the conversion of cytostatic responses (elicited by single inhibitor treatments) into a complete cell death response when PF384 and PD901 are combined. This response was also independent of KRAS mutation, occurring in both BxPC3 (KRAS wildtype) and MIA-PaCa-2 (KRAS^G12C mutated) cells. In both cell lines, Bim expression increased in response to PF384/PD901 treatment (by 60% and 48%, respectively), while siRNA-mediated silencing of Bim attenuated the apoptosis induced by combination treatment. In parallel, Mcl-1 levels decreased by 36% in BxPC3, and 30% in MIA-PaCa-2 cells. This is consistent with a functional role for Mcl-1, and siRNA-mediated silencing enhanced apoptosis in PF384/PD901-treated MIA-PaCa-2 cells, whilst Mcl-1 overexpression decreased apoptosis induction by 24%. Moreover, a novel role was identified for PDCD4 loss in driving the apoptotic response to PF384/PD901 in BxPC3 and MIA-PaCa-2 cell lines. Overall, our data indicates PF384/PD901 co-treatment activates the same apoptotic mechanism in wild-type or KRAS mutant PDAC cells.

A Synthetic Disaccharide Derivative of Diphyllin, TAARD, Activates Human Natural Killer Cells to Secrete Interferon-Gamma via Toll-Like Receptor-Mediated NF-κB and STAT3 Signaling Pathways

Natural products and their derivatives have long been used as pharmacological agents in the fight against cancer. Human natural killer (NK) cells are critical in our immune system in that they are capable of destroying tumor cells directly. However, there are few reports that elucidate the role of natural products in activating NK cells. In this study, we discovered that a synthetic disaccharide derivative of diphyllin, 4-O-{[2′′,3′′,4′′-tri-O-acetyl-α-D-arabinopyranosyl-(1′′→4′)]-2′,3′-di-O-acetyl-α-L-rhamnopyranosyl}diphyllin (TAARD), can alone stimulate interferon (IFN)-γ secretion in primary human NK cells and the NKL cell line. Additionally, it had an additive effect with IL-12 or IL-15 on IFN-γ production, but little adverse effects on NK cells. Mechanistically, TAARD induced the phosphorylation of NF-κB and STAT3, resulting in their binding on the IFNG promoter, which was dependent on TLR1 and TLR3 signaling, respectively. STAT3 and NF-κB knockdown with lentivirus shRNA as well as the NF-κB-specific inhibitor, N-tosyl-l-phenylalaninechloromethyl ketone, significantly suppressed TAARD-induced IFN-γ generation in primary NK cells. Blockade of TLR1 and TLR3 with neutralizing antibodies considerably decreased TAARD-induced activation of NF-κB and STAT3, respectively, as well as IFN-γ generation in NK cells. Collectively, our data suggest that TAARD can induce NK cell IFN-γ production through TLR1-NF-κB and TLR3-STAT3 signaling pathways, rendering its potential use as an agent for cancer prevention or treatment.

Embryonic Stem Cell-Derived Peripheral Auditory Neurons Form Neural Connections with Mouse Central Auditory Neurons In Vitro via the α2δ1 Receptor

Integration of stem cell-derived neurons into the central nervous system (CNS) remains a challenge. A co-culture system is developed to understand whether mouse embryonic stem cell (ESC)-derived spiral ganglion neuron (SGN)-like cells (ESNs) synapse with native mouse cochlear nucleus (CN) neurons. A Cre system is used to generate Cop-GFP ESCs, which are induced into ESNs expressing features similar to auditory SGNs. Neural connections are observed between ESNs and CN neurons 4–6 days after co-culturing, which is stimulated by thrombospondin-1 (TSP1). Antagonist and loss-of-function small hairpin RNA studies indicate that the α2δ1 receptor is critical for TSP1-induced synaptogenesis effects. Newly generated synapse-like structures express pre- and post-synaptic proteins. Synaptic vesicle recycling, pair recording, and blocker electrophysiology suggest functional synaptic vesicles, transsynaptic activities, and formation of glutamatergic synapses. These results demonstrate the synaptogenesis capability of ESNs, which is important for pluripotent ESC-derived neurons to form functional synaptic connections to CNS neurons.

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Embryonic stem cell-derived neurons form functional synapses with CNS neurons

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Thrombospondin-1 stimulates stem cell-based synaptogenesis via the α2δ1 receptor

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A co-culture system is developed to study stem cell-based synapse formation

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Stem cell-based synaptogenesis exhibits functional synapse features

STAT-3 regulation of CXCR4 is necessary for the prenylflavonoid Icaritin to enhance mesenchymal stem cell proliferation, migration and osteogenic differentiation

Mesenchymal stem cell (MSC) dysfunction has been implicated in the pathogenesis of osteoporosis. MSCs derived from osteoporotic subjects demonstrate significant impairment in proliferation, adhesion and chemotaxis, and osteogenic differentiation, leading to reduced functional bone-forming osteoblasts and ultimately nett bone loss and osteoporosis. Epimedium herbs and its active compound Icaritin (ICT) have been used in Chinese ethnopharmacology for the treatment of metabolic bone diseases. Using an in-vitro cell culture model, we investigated the benefits of ICT treatment in enhancing MSC proliferation, migration and osteogenic differentiation, and provide novel data to describe its mechanism of action. ICT enhances MSC proliferation, chemotaxis to stromal cell-derived factor-1 (SDF-1) and osteogenic differentiation through the activation of signal transduction activator transcription factor 3 (STAT-3), with a consequential up-regulation in the expression and activity of cysteine (C)-X-C motif chemokine receptor 4 (CXCR4). These findings provide a strong basis for future clinical studies to confirm the therapeutic potential of ICT for the prevention and treatment of osteoporosis and fragility fractures.

The prenylflavonoid Icaritin enhances osteoblast proliferation and function by signal transducer and activator of transcription factor 3 (STAT-3) regulation of C-X-C chemokine receptor type 4 (CXCR4) expression

In this study, we examined the effects of a natural prenylflavonoid Icaritin (ICT), on human osteoblast proliferation and osteogenic function. We observed that ICT dose-dependently enhanced osteoblast proliferation by ~15% over a 7day period. This increase in cell proliferation was associated with corresponding increases in osteoblast functions as measured by ALP secretion, intracellular calcium ions influx and calcium deposition. These anabolic effects were associated with a 4-fold increase in CXCR4 mRNA and protein expression. Silencing of CXCR4 protein expression using small interfering RNA reversed ICT-induced increase in cell proliferation, ALP activity and calcium deposition. Interestingly, we observed that ICT dose-dependently increased STAT-3 phosphorylation; and this resulted in increased binding of phosphorylated STAT-3 to the promoter region of the CXCR4 gene, to increase CXCR4 protein expression. Furthermore, we found that inhibition of STAT-3 phosphorylation resulted in a decrease in CXCR4 protein expression; whilst increasing phosphorylation of STAT-3 using a constitutive active STAT-3 vector significantly increased CXCR4 levels. Moreover, the chemical inhibition of STAT-3 phosphorylation annulled our previously observed ICT-induced increases of osteoblast proliferation and function. Finally, in a rat model of estrogen-deficient osteoporosis, ICT restored both osteoblasts numbers and CXCR4 expression. Taken together, both cellular and animal models support the novel findings that ICT; through the phosphorylation of STAT-3, up-regulated CXCR4, to increase osteoblast proliferation and function.

Alteration of SHP-1/p-STAT3 Signaling: A Potential Target for Anticancer Therapy

The Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 1 (SHP-1), a non-receptor protein tyrosine phosphatase, has been reported as a negative regulator of phosphorylated signal transducer and activator of transcription 3 (STAT3) and linked to tumor development. In this present review, we will discuss the importance and function of SHP-1/p-STAT3 signaling in nonmalignant conditions as well as malignancies, its cross-talk with other pathways, the current clinical development and the potential role of inhibitors of this pathway in anticancer therapy and clinical relevance of SHP-1/p-STAT3 in cancers. Lastly, we will summarize and highlight work involving novel drugs/compounds targeting SHP-1/p-STAT3 signaling and combined strategies that were/are discovered in our and our colleagues’ laboratories.

Preparation and characterization of lipid nanoparticle/pDNA complexes for STAT3 downregulation and overcoming chemotherapy resistance in lung cancer cells

Developments in the field of molecular oncology have revealed that resistance to chemotherapeutics is acqured through several mechanisms including overexpression of common oncogenic proteins. Signal Transducer and Activator of Transcription 3 (STAT3) is one of these oncogenes that is overexpressed in many cancer types. RNA interference (RNAi) is proven powerful tool for downregulating STAT3, allowing re-sensitization of resistant cancer cells. However, delivery of RNA interference-mediating molecules for STAT3 downregulation in lung cancer cells is limited to a small number of studies most of which employ commercially available transfection kits. The aim of this study was to develop and evaluate cationic solid lipid nanoparticles for delivery of RNAi-mediating plasmid DNA in order to down regulate STAT3 in cisplatin resistant lung cancer cells. We focused on obtaining cSLN:plasmid DNA complexes with size below or equal to 100nm, and a positive zeta potential. Two successful candidate cSLN:plasmid DNA complexes (K2 and K3) were selected for in vitro tests and cell culture studies. These formulations have particle sizes of 98 and 93nm, and zeta potential values of 10.5 and 8.9mV, respectively. Plasmid DNA in these complexes was protected against DNaseI and serum-mediated degradation. Substantial part of DNA retained its supercoiled and circular conformation. TEM images showed nearly spherical complex structure. Both formulations reduced STAT3 expression by approx. 5-fold in cisplatin resistant Calu1 cell line and increased the sensitivity of cells to cisplatin.

Bax/Bak-independent mitochondrial depolarization and reactive oxygen species induction by sorafenib overcome resistance to apoptosis in renal cell carcinoma

Renal cell carcinoma (RCC) is polyresistant to chemo- and radiotherapy and biologicals, including TNF-related apoptosis-inducing ligand (TRAIL). Sorafenib, a multikinase inhibitor approved for the treatment of RCC, has been shown to sensitize cancer cells to TRAIL-induced apoptosis, in particular by down-regulation of the Bak-inhibitory Bcl-2 family protein Mcl-1. Here we demonstrate that sorafenib overcomes TRAIL resistance in RCC by a mechanism that does not rely on Mcl-1 down-regulation. Instead, sorafenib induces rapid dissipation of the mitochondrial membrane potential (ΔΨ_m) that is accompanied by the accumulation of reactive oxygen species (ROS). Loss of ΔΨ_m and ROS production induced by sorafenib are independent of caspase activities and do not depend on the presence of the proapoptotic Bcl-2 family proteins Bax or Bak, indicating that both events are functionally upstream of the mitochondrial apoptosis signaling cascade. More intriguingly, we find that it is sorafenib-induced ROS accumulation that enables TRAIL to activate caspase-8 in RCC. This leads to apoptosis that involves activation of an amplification loop via the mitochondrial apoptosis pathway. Thus, our mechanistic data indicate that sorafenib bypasses central resistance mechanisms through a direct induction of ΔΨ_m breakdown and ROS production. Activation of this pathway might represent a useful strategy to overcome the cell-inherent resistance to cancer therapeutics, including TRAIL, in multiresistant cancers such as RCC.

Effects of RAF inhibitors on PI3K/AKT signalling depend on mutational status of the RAS/RAF signalling axis

Targeted therapies within the RAS/RAF/MEK/ERK signalling axis become increasingly popular, yet cross-talk and feedbacks in the signalling network lead to unexpected effects. Here we look systematically into how inhibiting RAF and MEK with clinically relevant inhibitors result in changes in PI3K/AKT activation. We measure the signalling response using a bead-based ELISA, and use a panel of three cell lines, and isogenic cell lines that express mutant forms of the oncogenes KRAS and BRAF to interrogate the effects of the MEK and RAF inhibitors on signalling. We find that treatment with the RAF inhibitors have opposing effects on AKT phosphorylation depending on the mutational status of two important oncogenes, KRAS and BRAF. If these two genes are in wildtype configuration, RAF inhibitors reduce AKT phosphorylation. In contrast, if BRAF or KRAS are mutant, RAF inhibitors will leave AKT phosphorylation unaffected or lead to an increase of AKT phosphorylation. Down-regulation of phospho-AKT by RAF inhibitors also extends to downstream transcription factors, and correlates with apoptosis induction. Our results show that oncogenes rewire signalling such that targeted therapies can have opposing effects on parallel pathways, which depend on the mutational status of the cell.

C2-ceramide enhances sorafenib-induced caspase-dependent apoptosis via PI3K/AKT/mTOR and Erk signaling pathways in HCC cells

Sorafenib as an effective multikinase inhibitor has been approved for the clinical treatment against advanced hepatocellular carcinoma (HCC). HCC treatment requires usually combined therapy because of its complex pathogenesis. Ceramide has been confirmed to induce remarkable apoptosis in human tumor cells and has attracted increasing attention in investigations on combination therapy. In this paper, the anti-HCC effect of sorafenib combined with C2-ceramide was investigated on cell vitality, apoptosis, and migration, and the underlying mechanism was examined using flow cytometry and western blot. Bel7402 cells coincubated with sorafenib and C2-ceramide exhibited lower cell vitality and more irregular cellular morphology and cell cycle arrest. Sorafenib plus C2-ceramide stimulated significantly the production of reactive oxygen species (ROS) and mitochondrial depolarization, which promoted caspases-dependent cell apoptosis as illustrated by related protein expression including caspase 3, caspase 9, Bax, Bcl-2, and cytochrome c. Combination treatment of sorafenib and C2-ceramide inhibited obviously cell growth and proliferation via PI3K/AKT/mTOR and Erk signaling pathways. Furthermore, the combination treatment was proved to inhibit cell migration and epithelial-mesenchymal transition (EMT). These findings indicated that the combination of C2-ceramide and sorafenib provided synergistic inhibitory effects on HCC cells.

A randomized, double-blind, placebo-controlled phase II study to assess the efficacy and safety of mapatumumab with sorafenib in patients with advanced hepatocellular carcinoma

BACKGROUND

This randomized, double-blind, placebo-controlled, phase II study evaluated the efficacy and safety of mapatumumab (a human agonistic monoclonal antibody against tumor necrosis factor-related apoptosis-inducing ligand receptor 1) in combination with sorafenib in patients with advanced hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Patients with advanced HCC (stratified by Barcelona Clinic Liver Cancer stage and Eastern Cooperative Oncology Group performance status) were randomized 1:1 to receive sorafenib (400 mg, twice daily per 21-day cycle) and either placebo (placebo-sorafenib arm) or mapatumumab (30 mg/kg on day 1 per 21-day cycle; mapatumumab-sorafenib arm). The primary end point was time to (radiologic) progression (TTP), assessed by blinded independent central review. Key secondary end points included progression-free survival, overall survival, and objective response.

RESULTS

In total, 101 patients were randomized (placebo-sorafenib arm: N = 51; mapatumumab-sorafenib arm: N = 50). There was no significant difference in median TTP between both arms [5.6 versus 4.1 months, respectively; adjusted hazard ratio (one-sided 90% confidence interval) 1.192 (0-1.737)]. No mapatumumab-related benefit was identified when TTP was evaluated in the stratified subgroups. The addition of mapatumumab to sorafenib did not demonstrate improvement in the secondary efficacy end points. The reported frequency of adverse events (AEs) and serious AEs was comparable in both treatment arms.

CONCLUSIONS

The addition of mapatumumab to sorafenib did not improve TTP or other efficacy end points, nor did it substantially change the toxicity profile of sorafenib in patients with advanced HCC. Based on these results, further development of the combination of mapatumumab and sorafenib in HCC is not planned.

Discovery of a new class of 16-membered (2Z,11Z)-3,11-di(aryl/naphthyl)-1,13-dioxa-5,9-dithia-2,12-diazacyclohexadeca-2,11-dienes as anti-tumor agents

A series of new 16-membered macrocyclic compounds were synthesized and evaluation of in vitro anti-tumor activities on MDAMB-231 cell lines reveal that the macrocycles, 1a, 1f, 1g, 1i and 1k are promising anti-tumor agents.

Signal transducer and activator of transcription 3-mediated CD133 up-regulation contributes to promotion of hepatocellular carcinoma

Enhanced expression of the cancer stem cell (CSC) marker, CD133, is closely associated with a higher rate of tumor formation and poor prognosis in hepatocellular carcinoma (HCC) patients. Despite its clinical significance, the molecular mechanism underlying the deregulation of CD133 during tumor progression remains to be clarified. Here, we report on a novel mechanism by which interleukin-6/signal transducer and activator of transcription 3 (IL-6/STAT3) signaling up-regulates expression of CD133 and promotes HCC progression. STAT3 activated by IL-6 rapidly bound to CD133 promoter and increased protein levels of CD133 in HCC cells. Reversely, in hypoxic conditions, RNA interference silencing of STAT3 resulted in decrease of CD133 levels, even in the presence of IL-6, with a concomitant decrease of hypoxia-inducible factor 1 alpha (HIF-1α) expression. Active STAT3 interacted with nuclear factor kappa B (NF-κB) p65 subunit to positively regulate the transcription of HIF-1α providing a mechanistic explanation on how those three oncogenes work together to increase the activity of CD133 in a hypoxic liver microenvironment. Activation of STAT3 and its consequent induction of HIF-1α and CD133 expression were not observed in Toll-like receptor 4/IL-6 double-knockout mice. Long-term silencing of CD133 by a lentiviral-based approach inhibited cancer cell-cycle progression and suppressed in vivo tumorigenicity by down-regulating expression of cytokinesis-related genes, such as TACC1, ACF7, and CKAP5. We also found that sorafenib and STAT3 inhibitor nifuroxazide inhibit HCC xenograft formation by blocking activation of STAT3 and expression of CD133 and HIF-1α proteins.

CONCLUSION

IL-6/STAT3 signaling induces expression of CD133 through functional cooperation with NF-κB and HIF-1α during liver carcinogenesis. Targeting STAT3-mediated CD133 up-regulation may represent a novel, effective treatment by eradicating the liver tumor microenvironment.

Cryptotanshinone suppresses the proliferation and induces the apoptosis of pancreatic cancer cells via the STAT3 signaling pathway

Pancreatic cancer remains a challenging disease worldwide. Cryptotanshinone (CPT) is one of the active constituents of Salvia miltiorrhiza Bunge and exhibits significant antitumor activities in several human cancer cells. However, the efficacy and molecular mechanism of CPT in pancreatic cancer remains to be elucidated. In the present study, the effect of CPT on the proliferation, apoptosis and cell cycle of human pancreatic cancer cell BxPC‑3 cells was evaluated. The results demonstrated that CPT inhibited proliferation of the BxPC‑3 cells in a concentration‑dependent manner, and significantly induced cell apoptosis and cell cycle arrest. The protein levels of cleaved caspase‑3, caspase‑9 and poly ADP ribose polymerase were upregulated, while the levels of c‑myc, survivin and cyclin D1 were downregulated following treatment with CPT. In addition, CPT decreased the activities of signal transducer and activator of transcription 3 (STAT3) and several upstream regulatory signaling pathways after 24 h. However, CPT only inhibited the phosphorylation of STAT3 Tyr705 within 30 min, without marked effects on the phosphorylation of the other proteins. These results suggested that the inhibition of STAT3 activity by CPT was directly and independent of the upstream regulators in human pancreatic cancer. The present study demonstrated that CPT exerts anticancer effects by inducing apoptosis and cell cycle arrest via inhibition of the STAT3 signaling pathway in human BxPC-3 cells.

The iron chelator Dp44mT inhibits hepatocellular carcinoma metastasis via N-Myc downstream-regulated gene 2 (NDRG2)/gp130/STAT3 pathway

Here we showed that hepatocellular carcinoma (HCC) cell lines with high metastatic potential had low levels of NDRG2. The iron chelator Dp44mT up-regulated NDRG2, suppressed epithelial-mesenchymal transition (EMT) and inhibited tumor metastasis in HCC having high metastatic potential. Also Dp44mT attenuated the TGF-β1-induced EMT in HCC having low metastatic potential. In agreement, silencing endogenous NDRG2 with shNDRG2 in HCC cells attenuated the effect of Dp44mT. We showed that the NDRG2/gp130/STAT3 pathway can mediate Dp44mT effects. In agreement, we found that a combination of NDRG2 expression and p-STAT3 levels is a strong predictor of prognosis in HCC patients. We suggest that up-regulation of NDRG2 by Dp44mT is a promising therapeutic approach in HCC.

G-CSF Promotes Neuroblastoma Tumorigenicity and Metastasis via STAT3-Dependent Cancer Stem Cell Activation

Increasing evidence suggests that inflammatory cytokines play a critical role in tumor initiation and progression. A cancer stem cell (CSC)-like subpopulation in neuroblastoma is known to be marked by expression of the G-CSF receptor (G-CSFR). Here, we report on the mechanistic contributions of the G-CSFR in neuroblastoma CSCs. Specifically, we demonstrate that the receptor ligand G-CSF selectively activates STAT3 within neuroblastoma CSC subpopulations, promoting their expansion in vitro and in vivo. Exogenous G-CSF enhances tumor growth and metastasis in human xenograft and murine neuroblastoma tumor models. In response to G-CSF, STAT3 acts in a feed-forward loop to transcriptionally activate the G-CSFR and sustain neuroblastoma CSCs. Blockade of this G-CSF-STAT3 signaling loop with either anti-G-CSF antibody or STAT3 inhibitor depleted the CSC subpopulation within tumors, driving correlated tumor growth inhibition, decreased metastasis, and increased chemosensitivity. Taken together, our results define G-CSF as a CSC-activating factor in neuroblastoma, suggest a comprehensive reevaluation of the clinical use of G-CSF in these patients to support white blood cell counts, and suggest that direct targeting of the G-CSF-STAT3 signaling represents a novel therapeutic approach for neuroblastoma.

Genetic and Pharmacological Screens Converge in Identifying FLIP, BCL2, and IAP Proteins as Key Regulators of Sensitivity to the TRAIL-Inducing Anticancer Agent ONC201/TIC10

ONC201/TIC10 is a small-molecule inducer of the TRAIL gene under current investigation as a novel anticancer agent. In this study, we identify critical molecular determinants of ONC201 sensitivity offering potential utility as pharmacodynamic or predictive response markers. By screening a library of kinase siRNAs in combination with a subcytotoxic dose of ONC201, we identified several kinases that ablated tumor cell sensitivity, including the MAPK pathway-inducer KSR1. Unexpectedly, KSR1 silencing did not affect MAPK signaling in the presence or absence of ONC201, but instead reduced expression of the antiapoptotic proteins FLIP, Mcl-1, Bcl-2, cIAP1, cIAP2, and survivin. In parallel to this work, we also conducted a synergy screen in which ONC201 was combined with approved small-molecule anticancer drugs. In multiple cancer cell populations, ONC201 synergized with diverse drug classes, including the multikinase inhibitor sorafenib. Notably, combining ONC201 and sorafenib led to synergistic induction of TRAIL and its receptor DR5 along with a potent induction of cell death. In a mouse xenograft model of hepatocellular carcinoma, we demonstrated that ONC201 and sorafenib cooperatively and safely triggered tumor regressions. Overall, our results established a set of determinants for ONC201 sensitivity that may predict therapeutic response, particularly in settings of sorafenib cotreatment to enhance anticancer responses.

Cancer-type-specific crosstalk between autophagy, necroptosis and apoptosis as a pharmacological target

Cell death plays an essential role in the development of organs, homeostasis, and cancer. Apoptosis and programmed necrosis are two major types of cell death, characterized by different cell morphology and pathways. Accumulating evidence shows autophagy as a new alternative target to treat tumor resistance. Besides its well-known pro-survival role, autophagy can be a physiological cell death process linking apoptosis and programmed necrosis cell death pathways, by various molecular mediators. Here, we summarize the effects of pharmacologically active compounds as modulators of different types of cancer cell death depending on the cellular context. Indeed, current findings show that both natural and synthetic compounds regulate the interplay between apoptosis, autophagy and necroptosis stimulating common molecular mediators and sharing common organelles. In response to specific stimuli, the same death signal can cause cells to switch from one cell death modality to another depending on the cellular setting. The discovery of important interconnections between the different cell death mediators and signaling pathways, regulated by pharmacologically active compounds, presents novel opportunities for the targeted treatment of cancer. The aim of this review is to highlight the potential role of these compounds for context-specific anticancer therapy.

Specific-detection of clinical samples, systematic functional investigations, and transcriptome analysis reveals that splice variant MUC4/Y contributes to the malignant progression of pancreatic cancer by triggering malignancy-related positive feedback loops signaling

Background

MUC4 plays important roles in the malignant progression of human pancreatic cancer. But the huge length of MUC4 gene fragment restricts its functional and mechanism research. As one of its splice variants, MUC4/Y with coding sequence is most similar to that of the full-length MUC4 (FL-MUC4), together with alternative splicing of the MUC4 transcript has been observed in pancreatic carcinomas but not in normal pancreas. So we speculated that MUC4/Y might be involved in malignant progression similarly to FL-MUC4, and as a research model of MUC4 in pancreatic cancer. The conjecture was confirmed in the present study.

Methods

MUC4/Y expression was detected by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) using gene-specific probe in the clinic samples. The effects of MUC4/Y were observed by serial in vitro and in vivo experiments based on stable over-expressed cell model. The underlying mechanisms were investigated by sequence-based transcriptome analysis and verified by qRT-PCR, Western blot and enzyme-linked immunosorbent assays.

Results

The detection of clinical samples indicates that MUC4/Y is significantly positive-correlated with tumor invasion and distant metastases. Based on stable forced-expressed pancreatic cancer PANC-1 cell model, functional studies show that MUC4/Y enhances malignant activity in vitro and in vivo, including proliferation under low-nutritional-pressure, resistance to apoptosis, motility, invasiveness, angiogenesis, and distant metastasis. Mechanism studies indicate the novel finding that MUC4/Y triggers malignancy-related positive feedback loops for concomitantly up-regulating the expression of survival factors to resist adverse microenvironment and increasing the expression of an array of cytokines and adhesion molecules to affect the tumor milieu.

Conclusions

In light of the enormity of the potential regulatory circuitry in cancer afforded by MUC4 and/or MUC4/Y, repressing MUC4 transcription, inhibiting post-transcriptional regulation, including alternative splicing, or blocking various pathways simultaneously may be helpful for controlling malignant progression. MUC4/Y- expression model is proven to a valuable tool for the further dissection of MUC4-mediated functions and mechanisms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-014-0309-8) contains supplementary material, which is available to authorized users.

(E)-2,4-Bis(p-hydroxyphenyl)-2-butenal inhibits tumor growth via suppression of NF-κB and induction of death receptor 6

The Maillard reaction products are known to be effective in chemoprevention. Here, we focused on the anti-cancer effects of (E)-2,4-bis(p-hydroxyphenyl)-2-butenal on in vitro and in vivo colon cancer. We analysed the anti-cancer activity of (E)-2,4-bis(p-hydroxyphenyl)-2-butenal on colon cancer cells by using cell cycle and apoptosis analysis. To elucidate it's mechanism, NF-κB DNA binding activity, docking model as well as pull-down assay. Further, a xenograft model of colon cancer was studied to test the in vivo effects of (E)-2,4-bis(p-hydroxyphenyl)-2-butenal. (E)-2,4-Bis(p-hydroxyphenyl)-2-butenal inhibited colon cancer cells (SW620 and HCT116) growth followed by induction of apoptosis in a concentration-dependent manner via down-regulation of NF-κB activity. In docking model as well as pull-down assay, (E)-2,4-bis(p-hydroxyphenyl)-2-butenal directly binds to three amino acid residues of IKKβ, thereby inhibited IKKβ activity in addition to induction of death receptor 6 (DR6) as well as their target apoptotic genes. Finally, (E)-2,4-bis(p-hydroxyphenyl)-2-butenal suppressed anchorage-independent cancer cell growth, and tumor growth in xenograft model accompanied with apoptosis through inhibition of IKKβ/NF-κB activity, and overexpression of DR6. These results suggest that (E)-2,4-bis(p-hydroxyphenyl)-2-butenal inhibits colon cancer cell growth through inhibition of IKKβ/NF-κB activity and induction of DR6 expression.

In comparative analysis of multi-kinase inhibitors for targeted medulloblastoma therapy pazopanib exhibits promising in vitro and in vivo efficacy

Regardless of the recent advances in cytotoxic therapies, 30% of children diagnosed with medulloblastoma. succumb to the disease. Therefore, novel therapeutic approaches are warranted. Here we demonstrate that Pazopanib a clinically approved multi-kinase angiogenesis inhibitor (MKI) inhibits proliferation and apoptosis in medulloblastoma cell lines. Moreover, Pazopanib profoundly attenuates medulloblastoma cell migration, a prerequisite for tumor invasion and metastasis. In keeping with the observed anti-neoplastic activity of Pazopanib, we also delineate reduced phosphorylation of the STAT3 protein, a key regulator of medulloblastoma proliferation and cell survival. Finally, we document profound in vivo activity of Pazopanib in an orthotopic mouse model of the most aggressive c-myc amplified human medulloblastoma variant. Pazopanib reduced the growth rate of intracranial growing medulloblastoma and significantly prolonged the survival. Furthermore, to put these results into a broader perspective we analysed Pazopanib side by side with the MKI Sorafenib. Both compounds share a similar target profile but display different pharmacodynamics and pharmacokinetics with distinct cytotoxic activity in different tumor entities. Thus, we identified Pazopanib as a new promising candidate for a rational clinical assessment for targeted paediatric medulloblastoma therapy.

Inhibition of myeloid cell leukemia-1: Association with sorafenib-induced apoptosis in human mucoepidermoid carcinoma cells and tumor xenograft

BACKGROUND

The purpose of our study was to investigate the anticancer effect of sorafenib on mucoepidermoid carcinoma (MEC) and find its new molecular mechanism.

METHODS

The apoptotic effects of sorafenib were performed using MTS assay, diamidino-phenylindole (DAPI) staining, Western blotting, reverse transcription-polymerase chain reaction (RT-PCR), siRNA, and xenograft.

RESULTS

Sorafenib had apoptotic effects on MC-3 and YD15 cells and decreased myeloid cell leukemia-1 (Mcl-1) through proteasome-dependent protein degradation and the inhibition of protein synthesis. Sorafenib significantly affected truncated bid (t-Bid) and siMcl-1 resulting in the upregulation of t-Bid to induce apoptosis. Signal transducer and activator of transcription 3 (STAT3) phosphorylation was also blocked by sorafenib and a potent STAT3 inhibitor, cryptotanshinone clearly induced poly ADP-ribose polymerase (PARP) cleavage by inhibiting Mcl-1 and increasing t-Bid. Finally, administration of sorafenib significantly suppressed tumor growth and induced apoptosis in tumor xenograft model in association with downregulation of Mcl-1 without any side effects.

CONCLUSION

Taken together, these findings suggest that sorafenib can be a good anticancer drug candidate for the treatment of MEC.

Hepatic stellate cell coculture enables sorafenib resistance in Huh7 cells through HGF/c-Met/Akt and Jak2/Stat3 pathways

Purpose. Tumor microenvironment confers drug resistance to kinase inhibitors by increasing RKT ligand levels that result in the activation of cell-survival signaling including PI3K and MAPK signals. We assessed whether HSC-LX2 coculture conferred sorafenib resistance in Huh7 and revealed the mechanism underlying the drug resistance. Experimental Design. The effect of LX2 on sorafenib resistance was determined by coculture system with Huh7 cells. The rescue function of LX2 supernatants was assessed by MTT assay and fluorescence microscopy. The underlying mechanism was tested by administration of pathway inhibitors and manifested by Western blotting. Results. LX2 coculture significantly induced sorafenib resistance in Huh7 by activating p-Akt that led to reactivation of p-ERK. LX2 secreted HGF into the culture medium that triggered drug resistance, and exogenous HGF could also induce sorafenib resistance. The inhibition of p-Akt blocked sorafenib resistance caused by LX2 coculture. Increased phosphorylation of Jak2 and Stat3 was also detected in LX2 cocultured Huh7 cells. The Jak inhibitor tofacitinib reversed sorafenib resistance by blocking Jak2 and Stat3 activation. The combined administration of sorafenib and p-Stat3 inhibitor S3I-201 augmented induced apoptosis even in the presence of sorafenib resistance. Conclusions. HSC-LX2 coculture induced sorafenib resistance in Huh7 through multiple pathways: HGF/c-Met/Akt pathway and Jak2/Stat3 pathway. A combined administration of sorafenib and S3I-201 was able to augment sorafenib-induced apoptosis even in the presence of LX2 coculture.

Synergistic inhibitory effect of hyperbaric oxygen combined with sorafenib on hepatoma cells

OBJECTIVES

Hypoxia is a common phenomenon in solid tumors, associated with chemotherapy and radiotherapy resistance, recurrence and metastasis. Hyperbaric oxygen (HBO) therapy can increase tissue oxygen pressure and content to prevent the resistance, recurrence and metastasis of cancer. Presently, Sorafenib is a first-line drug, targeted for hepatocellular carcinoma (HCC) but effective in only a small portion of patients and can induce hypoxia. The purpose of this study is to investigate the effect of HBO in combination with sorafenib on hepatoma cells.

METHODS

Hepatoma cell lines (BEL-7402 and SK-Hep1) were treated with HBO at 2 atmosphere absolute pressure for 80 min per day or combined with sorafenib or cisplatin. At different time points, cells were tested for cell growth, colony formation, apoptosis, cell cycle and migration. Finally, miRNA from the hepatoma cells was detected by microRNA array and validated by qRT-PCR.

RESULTS

Although HBO, sorafenib or cisplatin alone could inhibit growth of hepatoma cells, HBO combined with sorafenib or cisplatin resulted in much greater synergistic growth inhibition (cell proliferation and colony formation) in hepatoma cells. Similarly, the synergistic effect of HBO and sorafenib on induction of apoptosis was also observed in hepatoma cells. HBO induced G1 arrest in SK-Hep1 not in BEL-7402 cells, but enhanced cell cycle arrest induced by sorafenib in BEL-7402 treated cells. However, HBO had no obvious effect on the migration of hepatoma cells, and microRNA array analysis showed that hepatoma cells with HBO treatment had significantly different microRNA expression profiles from those with blank control.

CONCLUSIONS

We show for the first time that HBO combined with sorafenib results in synergistic growth inhibition and apoptosis in hepatoma cells, suggesting a potential application of HBO combined with sorafenib in HCC patients. Additionally, we also show that HBO significantly altered microRNA expression in hepatoma cells.

Herbal extract SH003 suppresses tumor growth and metastasis of MDA-MB-231 breast cancer cells by inhibiting STAT3-IL-6 signaling

Cancer inflammation promotes cancer progression, resulting in a high risk of cancer. Here, we demonstrate that our new herbal extract, SH003, suppresses both tumor growth and metastasis of MDA-MB-231 breast cancer cells via inhibiting STAT3-IL-6 signaling path. Our new herbal formula, SH003, mixed extract from Astragalus membranaceus, Angelica gigas, and Trichosanthes kirilowii Maximowicz, suppressed MDA-MB-231 tumor growth and lung metastasis in vivo and reduced the viability and metastatic abilities of MDA-MB-231 cells in vitro. Furthermore, SH003 inhibited STAT3 activation, which resulted in a reduction of IL-6 production. Therefore, we conclude that SH003 suppresses highly metastatic breast cancer growth and metastasis by inhibiting STAT3-IL-6 signaling path.

Pancreatic ductal adenocarcinoma: a review of immunologic aspects

With the continued failures of both early diagnosis and treatment options for pancreatic cancer, it is now time to comprehensively evaluate the role of the immune system on the development and progression of pancreatic cancer. It is important to develop strategies that harness the molecules and cells of the immune system to treat this disease. This review will focus primarily on the role of immune cells in the development and progression of pancreatic ductal adenocarcinoma and to evaluate what is known about the interaction of immune cells with the tumor microenvironment and their role in tumor growth and metastasis. We will conclude with a brief discussion of therapy for pancreatic cancer and the potential role for immunotherapy. We hypothesize that the role of the immune system in tumor development and progression is tissue specific. Our hope is that better understanding of this process will lead to better treatments for this devastating disease.

Regorafenib inhibits colorectal tumor growth through PUMA-mediated apoptosis

PURPOSE

Regorafenib, a multikinase inhibitor targeting the Ras/Raf/MEK/ERK pathway, has recently been approved for the treatment of metastatic colorectal cancer. However, the mechanisms of action of regorafenib in colorectal cancer cells have been unclear. We investigated how regorafenib suppresses colorectal cancer cell growth and potentiates effects of other chemotherapeutic drugs.

EXPERIMENTAL DESIGN

We determined whether and how regorafenib induces the expression of PUMA, a p53 target and a critical mediator of apoptosis in colorectal cancer cells. We also investigated whether PUMA is necessary for the killing and chemosensitization effects of regorafenib in colorectal cancer cells. Furthermore, xenograft tumors were used to test if PUMA mediates the in vivo antitumor, antiangiogenic, and chemosensitization effects of regorafenib.

RESULTS

We found that regorafenib treatment induces PUMA in colorectal cancer cells irrespective of p53 status through the NF-κB pathway following ERK inhibition and glycogen synthase kinase 3β activation. Upregulation of PUMA is correlated with apoptosis induction in different colorectal cancer cell lines. PUMA is necessary for regorafenib-induced apoptosis in colorectal cancer cells. Chemosensitization by regorafenib is mediated by enhanced PUMA induction through different pathways. Furthermore, deficiency in PUMA abrogates the in vivo antitumor, antiangiogenic, and chemosensitization effects of regorafenib.

CONCLUSIONS

Our results demonstrate a key role of PUMA in mediating the anticancer effects of regorafenib in colorectal cancer cells. They suggest that PUMA induction can be used as an indicator of regorafenib sensitivity, and also provide a rationale for manipulating the apoptotic machinery to improve the therapeutic efficacy of regorafenib and other targeted drugs.

The role of cell signalling in the crosstalk between autophagy and apoptosis

Not surprisingly, the death of a cell is a complex and well controlled process. For several decades, apoptosis, the first genetically programmed death process to be identified has taken centre stage as the principal mechanism of programmed cell death (type I cell death) in mammalian tissues. Apoptosis has been extensively studied and its contribution to the pathogenesis of disease well documented. However, apoptosis does not function alone in determining the fate of a cell. More recently, autophagy, a process in which de novo formed membrane enclosed vesicles engulf and consume cellular components, has been shown to engage in complex interplay with apoptosis. As a result, cell death has been subdivided into the categories apoptosis (Type I), autophagic cell death (Type II), and necrosis (Type III). The boundary between Type I and II cell death is not completely clear and as we will discuss in this review and perhaps a discrete difference does not exist, due to intrinsic factors among different cell types and crosstalk among organelles within each cell type. Apoptosis may begin with autophagy and autophagy can often end with apoptosis, inhibition or a blockade of caspase activity may lead a cell to default into Type II cell death from Type I.