Downregulation of signal transducer and activator of transcription 3 by sorafenib: A novel mechanism for hepatocellular carcinoma therapy

Identification of novel STAT3 inhibitors for liver fibrosis, using pharmacophore-based virtual screening, molecular docking, and biomolecular dynamics simulations

The signal transducer and activator of transcription 3 (STAT3) plays a fundamental role in the growth and regulation of cellular life. Activation and over-expression of STAT3 have been implicated in many cancers including solid blood tumors and other diseases such as liver fibrosis and rheumatoid arthritis. Therefore, STAT3 inhibitors are be coming a growing and interesting area of pharmacological research. Consequently, the aim of this study is to design novel inhibitors of STAT3-SH3 computationally for the reduction of liver fibrosis. Herein, we performed Pharmacophore-based virtual screening of databases including more than 19,481 commercially available compounds and in-house compounds. The hits obtained from virtual screening were further docked with the STAT3 receptor. The hits were further ranked on the basis of docking score and binding interaction with the active site of STAT3. ADMET properties of the screened compounds were calculated and filtered based on drug-likeness criteria. Finally, the top five drug-like hit compounds were selected and subjected to molecular dynamic simulation. The stability of each drug-like hit in complex with STAT3 was determined by computing their RMSD, RMSF, Rg, and DCCM analyses. Among all the compounds Sa32 revealed a good docking score, interactions, and stability during the entire simulation procedure. As compared to the Reference compound, the drug-like hit compound Sa32 showed good docking scores, interaction, stability, and binding energy. Therefore, we identified Sa32 as the best small molecule potent inhibitor for STAT3 that will be helpful in the future for the treatment of liver fibrosis.

Potential Treatment Strategies for Hepatocellular Carcinoma Cell Sensitization to Sorafenib

Liver cancer is highly malignant, has a low sensitivity to chemotherapy, and is associated with poor patient prognosis. The last 3 years have seen the emergence of promising targeted therapies for the treatment of hepatocellular carcinoma (HCC). For over 10 years, before the discovery of lenvatinib, sorafenib was only first-line therapeutic agent available for the treatment of advanced HCC. However, several clinical studies have shown that a considerable proportion liver cancer patients are insensitive to sorafenib. Very few patients actually substantially benefit from treatment with sorafenib, and the overall efficacy of the drug has not been satisfactory; therefore, sorafenib has attracted considerable research attention. This study, which is based on previous studies and reports, reviews the potential mechanisms underlying sorafenib resistance and summarizes combination therapies and potential drugs that can be used to sensitize HCC cells to sorafenib.

Modulation of the tumour microenvironment in hepatocellular carcinoma by tyrosine kinase inhibitors: from modulation to combination therapy targeting the microenvironment

Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide. Tyrosine kinase inhibitors (TKIs) remain the backbone of systematic therapy for advanced hepatocellular carcinoma. Sorafenib and lenvatinib are currently approved as first-line therapeutic drugs, and regorafenib and cabozantinib are applied as second-line treatments. With inhibition of angiogenesis as the main target, TKIs exert a profound effect on the tumour microenvironment (TME). The TME is a complex mixture of cellular and noncellular components surrounding the tumour mass, and is associated with tumour progression partially through the epithelial-mesenchymal transition. Specifically, the TME of HCC is characterized by profound extracellular matrix remodelling and an immunosuppressive microenvironment. The purpose of this review is to provide a summary of TME remodelling mediated by four Food and Drug Administration approved TKIs in HCC and thus summarize the rationale and potential targets for combination therapy. The modulatory effect of TKIs on the TME of HCC was reported to enhance the antitumour effect of TKIs through pyroptosis of macrophages and subsequent natural killer cell activation, T cell activation, regulatory T cell reduction in HCC. Meanwhile, TKIs also induce drug resistance via M2 polarization and accumulation, recruitment of tumour-associated neutrophils, and induction of the epithelial-mesenchymal transition. In conclusion, the effect of TKIs on TME can enhance its antitumour effect, but might also partially contribute to the drug resistance that hinders the progression of TKIs as treatment for HCC. Additionally, the effect of TKIs also provides the rationale for combination therapy, including combining TKIs with immune checkpoint inhibitors, to facilitate increased drug efficacy of TKIs.

Oxidative Stress Activated by Sorafenib Alters the Temozolomide Sensitivity of Human Glioma Cells Through Autophagy and JAK2/STAT3-AIF Axis

The development of temozolomide (TMZ) resistance in glioma leads to poor patient prognosis. Sorafenib, a novel diaryl urea compound and multikinase inhibitor, has the ability to effectively cross the blood-brain barrier. However, the effect of sorafenib on glioma cells and the molecular mechanism underlying the ability of sorafenib to enhance the antitumor effects of TMZ remain elusive. Here, we found that sorafenib could enhance the cytotoxic effects of TMZ in glioma cells in vitro and in vivo. Mechanistically, the combination of sorafenib and TMZ induced mitochondrial depolarization and apoptosis inducing factor (AIF) translocation from mitochondria to nuclei, and this process was dependent on STAT3 inhibition. Moreover, the combination of sorafenib and TMZ inhibited JAK2/STAT3 phosphorylation and STAT3 translocation to mitochondria. Inhibition of STAT3 activation promoted the autophagy-associated apoptosis induced by the combination of sorafenib and TMZ. Furthermore, the combined sorafenib and TMZ treatment induced oxidative stress while reactive oxygen species (ROS) clearance reversed the treatment-induced inhibition of JAK2/STAT3. The results indicate that sorafenib enhanced the temozolomide sensitivity of human glioma cells by inducing oxidative stress-mediated autophagy and JAK2/STAT3-AIF axis.

STAT3 phosphorylation in central leptin resistance

Mechanism exploitation of energy homeostasis is urgently required because of the worldwide prevailing of obesity-related metabolic disorders in human being. Although it is well known that leptin plays a central role in regulating energy balance by suppressing food intake and promoting energy expenditure, the existence of leptin resistance in majority of obese individuals hampers the utilization of leptin therapy against these disorders. However, the mechanism of leptin resistance is largely unknown in spite of the globally enormous endeavors. Current theories to interpret leptin resistance include the impairment of leptin transport, attenuation of leptin signaling, chronic inflammation, ER tress, deficiency of autophagy, as well as leptin itself. Leptin-activated leptin receptor (LepRb) signals in hypothalamus via several pathways, in which JAK2-STAT3 pathway, the most extensively investigated one, is considered to mediate the major action of leptin in energy regulation. Upon leptin stimulation the phosphorylation of STAT3 is one of the key events in JAK2-STAT3 pathway, followed by the dimerization and nuclear translocation of this molecule. Phosphorylated STAT3 (p-STAT3), as a transcription factor, binds to and regulates its target gene such as POMC gene, playing the physiological function of leptin. Regarding POMC gene in hypothalamus however little is known about the detail of its interaction with STAT3. Moreover the status of p-STAT3 and its significance in hypothalamus of DIO mice needs to be well elucidated. This review comprehends literatures on leptin and leptin resistance and especially discusses what STAT3 phosphorylation would contribute to central leptin resistance.

Berbamine (BBM), a Natural STAT3 Inhibitor, Synergistically Enhances the Antigrowth and Proapoptotic Effects of Sorafenib on Hepatocellular Carcinoma Cells

Sorafenib (SORA), a multi kinase inhibitor, is the standard first-line targeted therapy approved by the Food and Drug Administration for advanced hepatocellular carcinoma (HCC). However, emerging evidence from clinical practice indicates that SORA alone has only moderate antitumor effects and could not completely inhibit the progression of the disease. Therefore, it is very necessary and urgent to develop novel combination therapy to improve the clinical outcomes of SORA. The pharmacological study on the chemosensitizing effects of natural products has become a hotspot in recent years, which is commonly thought to be a potential way to improve the effectiveness of drugs in clinical use. Berbamine (BBM) has potential sensitizing effects in multiple chemotherapies and target therapy. However, it remains unclarified whether the combination of BBM and SORA as a treatment could exert a synergistic effect on HCC cell lines. In this study, we first investigated whether BBM can increase the sensitivity of HCC cell lines to SORA. The results revealed that the combination of BBM and SORA could synergistically inhibit the growth of two HCC cell lines and promoted their apoptosis. Mechanistically, our results showed that BBM exerted a dose-dependent inhibitory effect on the basal and IL-6-induced STAT3 activation of HCC cell lines. In addition, the combined treatment of BBM and SORA synergistically suppressed STAT3 phosphorylation at Tyr705 and knockdown of STAT3 abolished the sensitization effect of BBM, indicating that BBM's sensitization effect is mainly mediated by its inhibition of STAT3. These findings identify a new type of natural STAT3 inhibitor and provide a novel approach to the enhancement of SORA efficacy by blocking the activation of STAT3.

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.

Down-regulated lncRNA DLX6-AS1 inhibits tumorigenesis through STAT3 signaling pathway by suppressing CADM1 promoter methylation in liver cancer stem cells

Background

Liver cancer stem cells (LCSCs) are a small subset of cells characterized by unlimited self-renewal, cell differentiation, and uncontrollable cellular growth. LCSCs are also resistant to conventional therapies and are thus believed to be held responsible for causing treatment failure of hepatocellular carcinoma (HCC). It has been recently found that long non-coding RNAs (lncRNAs) are important regulators in HCC. This present study aims to explore the underlying mechanism of how lncRNA DLX6-AS1 influences the development of LCSCs and HCC.

Methods

A microarray-based analysis was performed to initially screen differentially expressed lncRNAs associated with HCC. We then analyzed the lncRNA DLX6-AS1 levels as well as CADM1 promoter methylation. The mRNA and protein expression of CADM1, STAT3, CD133, CD13, OCT-4, SOX2, and Nanog were then detected. We quantified our results by evaluating the spheroid formation, proliferation, and tumor formation abilities, as well as the proportion of tumor stem cells, and the recruitment of DNA methyltransferase (DNMT) in LCSCs when lncRNA DLX6-AS1 was either overexpressed or silenced.

Results

LncRNA DLX6-AS1 was upregulated in HCC. The silencing of lncRNA DLX6-AS1 was shown to reduce and inhibit spheroid formation, colony formation, proliferation, and tumor formation abilities, as well as attenuate CD133, CD13, OCT-4, SOX2, and Nanog expression in LCSCs. Furthermore, downregulation of lncRNA DLX6-AS1 contributed to a reduction in CADM1 promoter methylation via suppression of DNMT1, DNMT3a, and DNMT3b in LCSCs and inactivating the STAT3 signaling pathway.

Conclusion

This study demonstrated that down-regulated lncRNA DLX6-AS1 may inhibit the stem cell properties of LCSCs through upregulation of CADM1 by suppressing the methylation of the CADM1 promoter and inactivation of the STAT3 signaling pathway.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1239-3) contains supplementary material, which is available to authorized users.

Chemoprevention of colorectal cancer by black raspberry anthocyanins involved the modulation of gut microbiota and SFRP2 demethylation

Freeze-dried black raspberry (BRB) powder is considered as a potential cancer chemopreventive agent. In this study, we fed azoxymethane (AOM)/dextran sodium sulfate (DSS)-treated C57BL/6J mice with a diet containing BRB anthocyanins for 12 weeks, and this led to a reduction in colon carcinogenesis. These animals had consistently lower tumor multiplicity compared with AOM/DSS-treated mice not receiving BRB anthocyanins. In AOM/DSS-treated mice, the number of pathogenic bacteria, including Desulfovibrio sp. and Enterococcus spp., was increased significantly, whereas probiotics such as Eubacterium rectale, Faecalibacterium prausnitzii and Lactobacillus were dramatically decreased, but BRB anthocyanins supplement could reverse this imbalance in gut microbiota. BRB anthocyanins also caused the demethylation of the SFRP2 gene promoter, resulting in increased expression of SFRP2, both at the mRNA and protein levels. Furthermore, the expression levels of DNMT31 and DNMT3B, as well as of p-STAT3 were downregulated by BRB anthocyanins in these animals. Taken together, these results suggested that BRB anthocyanins could modulate the composition of gut commensal microbiota, and changes in inflammation and the methylation status of the SFRP2 gene may play a central role in the chemoprevention of CRC.

Chemical and genetic inhibition of STAT3 sensitizes hepatocellular carcinoma cells to sorafenib induced cell death

Hepatocellular carcinoma (HCC) has become the second leading cause of cancer related death, with an increasing death rate in recent years. For advanced HCC, sorafenib is the first-line FDA approved drug, with no more than 3 months' overall survival advantage. Recently, a novel strategy has been proposed to improve sorafenib efficacy through enhancing the ability of sorafenib to induce cell death. STAT3 plays a key role in cancer development and recurrence by promoting cell proliferation, survival and immune evasion through its well-established function as a transcription factor in cancer. Notably, STAT3 transcription activity, indicated by its phosphorylation on Y705 is heterogeneous in different liver cancer cell lines. And sorafenib attenuates STAT3 phosphorylation on Y705. However, the role of STAT3 in sorafenib induced cell death is still largely unknown. Here, we show that liver cancer cells also exhibit heterogeneous sensitivities to sorafenib induced cell death, which co-relates with the STAT3-Y705 phosphorylation levels and JAK1/2 expression levels in Hep3B, Huh7 and HepG2 cells. Furthermore, overexpression or knockdown of STAT3 could switch HCC cells between resistant and sensitive to sorafenib induced cell death, which could be partially due to its regulation on Mcl-1, an anti-apoptotic protein. Finally, both inhibitors of STAT3 SH2 domain (S3i-201) or STAT3 upstream kinases JAKs (JAK inhibitor I) could synergistically enhance sorafenib induced cell death. Taken together, these data strongly suggest that STAT3 is not only a downstream effector of sorafenib, but also a key regulator of cellular sensitivity to sorafenib induced cell death, which provide support for the notion to develop STAT3-targeting drugs to improve clinical efficacy of sorafenib in liver cancer.

The Roles of Protein Tyrosine Phosphatases in Hepatocellular Carcinoma

The protein tyrosine phosphatase (PTP) family is involved in multiple cellular functions and plays an important role in various pathological and physiological processes. In many chronic diseases, for example cancer, PTP is a potential therapeutic target for cancer treatment. In the last two decades, dozens of PTP inhibitors which specifically target individual PTP molecules were developed as therapeutic agents. Hepatocellular carcinoma (HCC) is one of the most common malignant tumors and is the second most lethal cancer worldwide due to a lack of effective therapies. Recent studies have unveiled both oncogenic and tumor suppressive functions of PTP in HCC. Here, we review the current knowledge on the involvement of PTP in HCC and further discuss the possibility of targeting PTP in HCC.

Deubiquitinase inhibitor b-AP15 activates endoplasmic reticulum (ER) stress and inhibits Wnt/Notch1 signaling pathway leading to the reduction of cell survival in hepatocellular carcinoma cells

b-AP15, a potent and selective inhibitor of the ubiquitin-specific peptidase 14 (USP14), displays in vitro and in vivo antitumor abilities on some types of cancer cells. However, the mechanism underlying its action is not well elucidated. The purposes of the present study are to observe the potential impacts of b-AP15 on cell survival of hepatocellular carcinoma cells and to investigate whether and how this compound inhibits some survival-promoting signaling pathways. We found that b-AP15 significantly decreased cell viability and increased cell apoptosis in a dose-dependent manner in hepatocellular carcinoma cells, along with the perturbation of cell cycle and the decreased expressions of cell cycle-related proteins. We also demonstrated that the endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) were enhanced by b-AP15 supplementation. The inhibition of ER stress/UPR only partly attenuated the cytotoxicity of b-AP15 on hepatocellular carcinoma cells. In addition, b-AP15 treatment inhibited Wnt/β-catenin and Notch1 signaling pathways, and suppressed phosphorylation of STAT3, Akt, and Erk1/2, which were not restored by the inhibition of ER stress/UPR. Furthermore, the expression levels of signaling molecules in Notch1 were reduced by specific inhibitor of Wnt/β-catenin pathway. Notably, either Wnt or Notch1 signaling inhibitor mitigated phosphorylation of STAT3, Akt, and Erk1/2, and mimicked the cytotoxicity of b-AP15 on hepatocellular carcinoma cells. These results clearly indicate that b-AP15 induced cytotoxic response to hepatocellular carcinoma cells by augmenting ER stress/UPR and inhibiting Wnt/Notch1 signaling pathways. This new finding provides a novel mechanism by which b-AP15 produces its antitumor therapeutic effects.

Cucurbitacin B and cancer intervention: Chemistry, biology and mechanisms (Review)

Cancer is one of the most important healthcare matters, with the worst prognosis but the best possibilities for scientific development. It is likely to increase in the future and cause global havoc designating it as an epidemic. Cancer development requires urgent intervention. Past few decades have witnessed extensive research to challenge carcinogenesis. Treatment involving synthetic discipline is often associated with severe adverse effects, or even worsened prognosis. Accordingly, newer economic and patient friendly molecules are warranted. Many natural substances have proved their potential so far. Cucurbitacin B against cancer and other diseases has achieved towering popularity among the researchers around the world, as detailed in the below sections with summarized tables. In line with the fascinating role of cucurbitacin B against various types of cancers, through various molecular signaling pathways, it is justifiable to propose cucurbitacin B as a mainline chemotherapy before the onset and after the diagnosis of cancer.

Kinome and Transcriptome Profiling Reveal Broad and Distinct Activities of Erlotinib, Sunitinib, and Sorafenib in the Mouse Heart and Suggest Cardiotoxicity From Combined Signal Transducer and Activator of Transcription and Epidermal Growth Factor Receptor Inhibition

BACKGROUND

Most novel cancer therapeutics target kinases that are essential to tumor survival. Some of these kinase inhibitors are associated with cardiotoxicity, whereas others appear to be cardiosafe. The basis for this distinction is unclear, as are the molecular effects of kinase inhibitors in the heart.

METHODS AND RESULTS

We administered clinically relevant doses of sorafenib, sunitinib (cardiotoxic multitargeted kinase inhibitors), or erlotinib (a cardiosafe epidermal growth factor receptor inhibitor) to mice daily for 2 weeks. We then compared the effects of these 3 kinase inhibitors on the cardiac transcriptome using RNAseq and the cardiac kinome using multiplexed inhibitor beads coupled with mass spectrometry. We found unexpectedly broad molecular effects of all 3 kinase inhibitors, suggesting that target kinase selectivity does not define either the molecular response or the potential for cardiotoxicity. Using in vivo drug administration and primary cardiomyocyte culture, we also show that the cardiosafety of erlotinib treatment may result from upregulation of the cardioprotective signal transducer and activator of transcription 3 pathway, as co-treatment with erlotinib and a signal transducer and activator of transcription inhibitor decreases cardiac contractile function and cardiomyocyte fatty acid oxidation.

CONCLUSIONS

Collectively our findings indicate that preclinical kinome and transcriptome profiling may predict the cardiotoxicity of novel kinase inhibitors, and suggest caution for the proposed therapeutic strategy of combined signal transducer and activator of transcription/epidermal growth factor receptor inhibition for cancer treatment.

Sorafenib stimulates human skin type mast cell degranulation and maturation

BACKGROUND

Sorafenib is a multi-kinase inhibitor for treating advanced hepatocellular and renal cell carcinomas by targeting various types of receptors and signaling molecules, including vascular endothelial growth factor receptors, platelet-derived growth factor receptor, and Raf-1. Sorafenib may cause diverse cutaneous adverse reactions, including hand-foot reaction, facial and scalp eruptions, alopecia and pruritus. However, the mechanism of these adverse effects has not been well-investigated.

OBJECTIVE

Mast cells (MCs) are reported to be associated with various types of skin diseases. To investigate the mechanism of sorafenib-induced cutaneous adverse effects, we focused on MCs in situ.

METHODS

We evaluated skin samples of organ cultured normal human skin treated with sorafenib using c-Kit, tryptase, and stem cell factor (SCF), Ki-67, and TUNEL immunohistochemistry as well as quantitative real-time polymerase chain reaction to evaluate MC number, degranulation, proliferation, and apoptosis in situ.

RESULTS

Sorafenib significantly increased the number and degranulation of skin-type MCs compared with the vehicle-treated control group in situ. However, sorafenib did not affect MC proliferation and apoptosis, suggesting that it stimulated MC maturation from resident precursors. Furthermore, sorafenib increased SCF expression in situ. The increase in MC number by sorafenib was abrogated by co-administration of SCF neutralizing antibody or the phosphoinositide 3-kinase (PI3K) inhibitor, wortmannin, but not the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor, PD98059. This suggests that SCF is involved in sorafenib-induced MC maturation. In addition, the compensatory upregulation of PI3K-signaling from inhibition of MAPK signaling by sorafenib might stimulate MC maturation in situ. We also evaluated MCs within the skin samples from patients with drug eruptions by sorafenib administration. The total and degranuated MCs number as well as SCF expression was significantly increased compared to healthy individuals.

CONCLUSION

Our results contribute to a better understanding of the mechanism by which sorafenib induces adverse cutaneous reactions via activation of skin-type MC degranulation and maturation. This activation appears to be related to PI3K signaling and SCF production, which could be a new targets for treating sorafenib-induced adverse reactions.

Evolving role of Sorafenib in the management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant diseases worldwide and comes third in cancer-related mortality. Although there is a broad spectrum of treatment options to choose from, only a few patients are eligible candidates to receive a curative therapy according to their stage of disease, and thus palliative treatment is implemented in the majority of the patients suffering from liver cancer. Sorafenib, a multikinase inhibitor, is the only currently approved agent for systemic therapy in patients with advanced stage HCC and early stage liver disease. It has been shown to improve the overall survival, but with various side effects, while its cost is not negligible. Sorafenib has been in the market for a decade and has set the stage for personalized targeted therapy. Its role during this time has ranged from monotherapy to neoadjuvant and adjuvant treatment with surgical resection, liver transplantation and chemoembolization or even in combination with other chemotherapeutic agents. In this review our aim is to highlight in depth the current position of Sorafenib in the armamentarium against HCC and how that has evolved over time in its use either as a single agent or in combination with other therapies.

Anticancer effect of cucurbitacin B on MKN-45 cells via inhibition of the JAK2/STAT3 signaling pathway

The aim of the present study was to investigate the effect of cucurbitacin B on MKN-45 gastric carcinoma cells. Cell proliferation was determined using a cell counting kit-8 assay, and commercial cell cycle and apoptosis analysis kits were used to determine the cell cycle by flow cytometry. The mRNA expression of genes which mediate cell cycle checkpoints and apoptosis was detected using reverse transcription-quantitative polymerase chain reaction, and a terminal deoxynucleotidyl transferase dUTP nick end labeling assay was used to determine apoptosis rate. Western blot analysis was used to detect the protein expression levels of JAK2/STAT3 signaling pathway-associated proteins. The presented data show that cucurbitacin B significantly inhibited the proliferation of MKN-45 cells in a dose- and time-dependent manner. In accordance with these findings, cucurbitacin B blocked the progression of the cell cycle from G0/G1 to S phase, which was confirmed by the mRNA expression analysis. Cucurbitacin B treatment significantly suppressed the expression of cyclin D1, cyclin E, cyclin-dependent kinase 4 (CDK4) and CDK2, while increasing the expression of p27. Cucurbitacin B also promoted cell apoptosis, as was determined by TUNEL assay and evaluation of mRNA expression. Further experiments suggested that the beneficial effect of cucurbitacin B on blocking the proliferation and inducing the apoptosis of MKN-45 cells may have been associated with suppression of the JAK2/STAT3 signaling pathway. Thus, the present results indicate that cucurbitacin B suppresses proliferation and promoted apoptosis of MKN-45 cells, which may be mediated by inhibition of the JAK2/STAT3 signaling pathway. Cucurbitacin B therefore may warrant further investigation as a feasible therapy for gastric carcinoma.

Signal transducer and activator of transcription 3 in myeloid-derived suppressor cells: an opportunity for cancer therapy

Cancer progression is in part determined by interactions between cancer cells and stromal cells in the tumor microenvironment (TME). The identification of cytotoxic tumor-infiltrating lymphocytes has instigated research into immune stimulating cancer therapies. Although a promising direction, immunosuppressive mechanisms exerted at the TME hamper its success. Myeloid-derived suppressor cells (MDSCs) have come to the forefront as stromal cells that orchestrate the immunosuppressive TME. Consequently, this heterogeneous cell population has been the object of investigation. Studies revealed that the transcription factor signal transducer and activator of transcription 3 (STAT3) largely dictates the recruitment, activation and function of MDSCs in the TME. Therefore, this review will focus on the role of this key transcription factor during the MDSC's life cycle and on the therapeutic opportunities it offers.

Very-long-chain fatty acid sphingomyelin in nuclear lipid microdomains of hepatocytes and hepatoma cells: can the exchange from C24:0 to C16:0 affect signal proteins and vitamin D receptor?

Lipid microdomains localized in the inner nuclear membrane are considered platforms for active chromatin anchoring. Stimuli such as surgery, vitamin D, or glucocorticoid drugs influence their gene expression, DNA duplication, and RNA synthesis. In this study, we used ultrafast liquid chromatography-tandem mass spectrometry to identify sphingomyelin (SM) species coupled with immunoblot analysis to comprehensively map differences in nuclear lipid microdomains (NLMs) purified from hepatocytes and hepatoma cells. We showed that NLMs lost saturated very-long-chain fatty acid (FA; C24:0) SM in cancer cells and became enriched in long-chain FA (C16:0) SM. We also found that signaling proteins, such as STAT3, Raf1, and PKCζ, were increased and vitamin D receptor was reduced in cancer cells. Because recent researches showed a shift in sphingolipid composition from C24:0 to C16:0 in relation to cell life, we performed a comparative analysis of properties among C16:0 SM, C24:0 SM, and cholesterol. Our results led us to hypothesize that the enrichment of C16:0 SM could determine enhanced dynamic properties of NLMs in cancer cells with an increased shuttling of protein signaling molecules.

Sorafenib effect on liver neoplastic changes in rats: more than a kinase inhibitor

Although sorafenib was approved as antiangiogenic agent in case of hepatocellular carcinoma (HCC), the pathways mediating its antitumorigenic effects were not fully examined in vivo. This study was conducted to elucidate the molecular mechanisms underlying the antineoplastic effect of sorafenib in livers of rats exposed to the hepatocarcinogen diethyl nitrosamine (DENA) regarding oxidative stress, proliferation, and apoptotic pathways. Male albino rats were divided into three groups: normal control, DENA group, and sorafenib group. Sorafenib (10 mg/kg) was given daily to rats orally for 2 weeks, started 6 weeks after DENA (200 mg/kg, single i.p. dose). The histopathological results proved that sorafenib corrected neoplastic changes in the liver as evidenced by a decrease in size of hepatocellular foci. The liver index, glutathione, as well as Bcl-2 were significantly decreased in sorafenib group compared with DENA group. Sorafenib also exhibited antiproliferative effect through suppression of gene expression of cyclin D1 and β-catenin. Thus, the apoptotic and proliferative pathways in HCC could be interrupted by sorafenib, supporting the role of sorafenib as antineoplastic agent and nominating it as a candidate drug for other neoplasms.

Comparative Metabolomic Profiling of Hepatocellular Carcinoma Cells Treated with Sorafenib Monotherapy vs. Sorafenib-Everolimus Combination Therapy

Background

Sorafenib-everolimus combination therapy may be more effective than sorafenib monotherapy for hepatocellular carcinoma (HCC). To better understand this effect, we comparatively profiled the metabolite composition of HepG2 cells treated with sorafenib, everolimus, and sorafenib-everolimus combination therapy.

Material/Methods

A 2D HRMAS ¹H-NMR metabolomic approach was applied to identify the key differential metabolites in 3 experimental groups: sorafenib (5 μM), everolimus (5 μM), and combination therapy (5 μM sorafenib +5 μM everolimus). MetaboAnalyst 3.0 was used to perform pathway analysis.

Results

All OPLS-DA models displayed good separation between experimental groups, high-quality goodness of fit (R2), and high-quality goodness of predication (Q2). Sorafenib and everolimus have differential effects with respect to amino acid, methane, pyruvate, pyrimidine, aminoacyl-tRNA biosynthesis, and glycerophospholipid metabolism. The addition of everolimus to sorafenib resulted in differential effects with respect to pyruvate, amino acid, methane, glyoxylate and dicarboxylate, glycolysis or gluconeogenesis, glycerophospholipid, and purine metabolism.

Conclusions

Sorafenib and everolimus have differential effects on HepG2 cells. Sorafenib preferentially affects glycerophospholipid and purine metabolism, while the addition of everolimus preferentially affects pyruvate, amino acid, and glucose metabolism. This phenomenon may explain (in part) the synergistic effects of sorafenib-everolimus combination therapy observed in vivo.

Cross-resistance to clinically used tyrosine kinase inhibitors sunitinib, sorafenib and pazopanib

PURPOSE

When during cancer treatment resistance to a tyrosine kinase inhibitor (TKI) occurs, switching to another TKI is often considered as a reasonable option. Previously, we reported that resistance to sunitinib may be caused by increased lysosomal sequestration, leading to increased intracellular lysosomal storage and, thereby, inactivity. Here, we studied the effect of several other TKIs on the development of (cross-) resistance.

METHODS

TKI resistance was induced by continuous exposure of cancer cell lines to increasing TKI concentrations for 3-4 months. (Cross-) resistance was evaluated using MTT cell proliferation assays. Intracellular TKI concentrations were measured using LC-MS/MS. Western blotting was used to detect lysosome-associated membrane protein-1 and -2 (LAMP1/2) expression.

RESULTS

The previously generated sunitinib-resistant (SUN) renal cancer cells (786-O) and colorectal cancer cells (HT-29) were found to be cross-resistant to pazopanib, erlotinib and lapatinib, but not sorafenib. Exposure of 786-O and HT-29 cells to sorafenib, pazopanib or erlotinib for 3-4 months induced drug resistance to pazopanib and erlotinib, but not sorafenib. Intracellular drug accumulation was found to be increased in pazopanib- and erlotinib-, but not in sorafenib-exposed cells. Lysosomal capacity, reflected by LAMP1/2 expression, was found to be increased in resistant cells and, in addition, to be transient. No cross-resistance to the mTOR inhibitor everolimus was detected.

CONCLUSIONS

Our data indicate that tumor cells can develop (cross-) resistance to TKIs, and that such resistance includes increased intracellular drug accumulation accompanied by increased lysosomal storage. Transient (cross-) resistance was found to occur for several of the TKIs tested, but not for everolimus, indicating that switching from a TKI to a mTOR inhibitor may be an attractive therapeutic option.