Celastrol inhibits proliferation and induces chemosensitization through down-regulation of NF-κB and STAT3 regulated gene products in multiple myeloma cells

The short-term effect of histone deacetylase inhibitors, chidamide and valproic acid, on the NF‑κB pathway in multiple myeloma cells

Research regarding histone deacetylase (HDAC) inhibitors (HDACis) has garnered interest for the treatment of multiple myeloma (MM). In addition, the high expression of nuclear factor (NF)-κB in MM cells is considered an important factor in the occurrence and development of MM. The present study aimed to determine the short-term effects of HDACis, chidamide and valproic acid (VPA), on MM cells, their effects on NF-κB and the underlying mechanisms. The present study measured HDAC activity, and the proliferation and apoptosis of U266 and RPMI8226 MM cells following treatment with various concentrations of chidamide and VPA for 6 and 48 h. Western blotting was used to detect the expression levels of phosphorylated (p)-IκB kinase (IKK)α/β, NF-κB p65 and inhibitor of NF-κB (IκBα) in U266 and RPMI8226 cells at various time points following treatment with chidamide and VPA (0, 2, 4 and 6 h). The results revealed that chidamide and VPA had no significant effect on the HDAC activity, proliferation and apoptosis of cells at 6 h; however, cell HDAC activity and proliferation were inhibited, and apoptosis was induced at 48 h. Furthermore, the expression levels of IκBα were gradually increased over time, whereas the expression levels of NF-κB p65 gradually decreased. These findings indicated that long-term (48 h) treatment with the HDACis chidamide and VPA inhibited the proliferation and promoted the apoptosis of MM cells; however, these HDACis had little effect on cell proliferation and apoptosis in the short term (6 h). Notably, in the short term (2-6 h), hyperactivation of NF-κB was inhibited via the IκBα-NF-κB p65 pathway. These findings indicated that cell growth may be inhibited and drug susceptibility may be promoted by blocking the NF-κB pathway at an early stage, when HDACis are combined with other drugs in the treatment of MM.

YL064 directly inhibits STAT3 activity to induce apoptosis of multiple myeloma cells

Aberrant activation of signal transducer and activator of transcription 3 (STAT3) plays a critical role in the proliferation and survival of multiple myeloma. And inactivation of STAT3 is considered a promising strategy for the treatment of multiple myeloma. Here we show that the sinomenine derivative YL064 could selectively reduce the cell viability of multiple myeloma cell lines and primary multiple myeloma cells. Moreover, YL064 also induces cell death of myeloma cells in the presence of stromal cells. Western blot analysis showed that YL064 inhibited the constitutive activation and IL-6-induced activation of STAT3, reflected by the decreased phosphorylation of STAT3 on Tyr705. Consistent with this, YL064 inhibited the nuclear translocation of STAT3 and the expression of STAT3 target genes, such as cyclin D1 and Mcl-1. Using biotin- and FITC-labeled YL064, we found that YL064 could pull-down STAT3 from myeloma cells and colocalized with STAT3, suggesting that YL064 directly targets STAT3. Cellular thermal shift assay further demonstrated the engagement of YL064 to STAT3 in cells. Molecular docking studies indicated that YL064 may interact with STAT3 in its SH2 domain, thereby inhibiting the dimerization of STAT3. Finally, YL064 inhibited the growth of human myeloma xenograft in vivo. Taken together, this study demonstrated that YL064 may be a promising candidate compound for the treatment of multiple myeloma by directly targeting STAT3.

The Role of Signal Transducer and Activator of Transcription 3 (STAT3) and Its Targeted Inhibition in Hematological Malignancies

Signal transducer and activator of transcription 3 (STAT3), a member of the STAT protein family, can be phosphorylated by receptor-associated Janus kinases (JAKs) in response to stimulation by cytokines and growth factors. It forms homo- or heterodimers that can translocate to the cell nucleus where they act as transcription activators. Constitutive activation of STAT3 has been found to be associated with initiation and progression of various cancers. It can exert proliferative as well as anti-apoptotic effects. This review focuses on the role of STAT3 in pathogenesis i.e., proliferation, differentiation, migration, and apoptosis of hematological malignancies viz. leukemia, lymphoma and myeloma, and briefly highlights the potential therapeutic approaches developed against STAT3 activation pathway.

Celastrol as a pentacyclic triterpenoid with chemopreventive properties

Celastrol is a highly investigated anticancer moiety. It is a pentacyclic triterpenoid, isolated several decades ago with promising role in chemoprevention. Celastrol has been found to target multiple proinflammatory, angiogenic and metastatic proteins. Inhibition of these targets results in significant reduction of cancer growth, survival and metastasis. This review summarizes the varied molecular targets of celastrol along with insight into the various recently published clinical, preclinical and industrial patents (2011-2017).

Anti-myeloma Effects of Icariin Are Mediated Through the Attenuation of JAK/STAT3-Dependent Signaling Cascade

Because of the essential role of signal transducer and activator of transcription 3 (STAT3) in proliferation, anti-apoptosis, and chemoresistance of multiple myeloma (MM), we investigated whether icariin, a prenylated flavonol glycoside, inhibits both constitutive and inducible STAT3 activation in human myeloma cell lines. We noted that icariin could block constitutive STAT3 phosphorylation as well as its nuclear translocation and DNA binding ability in U266 cells. Icariin also suppressed IL-6-induced STAT3 activation through the inhibition of upstream kinases (Janus activated kinase-1 and -2, and c-Src). We found that icariin downregulated the protein expression of STAT3 downstream target gene products such as Bcl-2, Bcl-xl, survivin, IAP-1/2, COX-2, VEGF, and matrix metallopeptidase 9 (MMP-9) in a concentration-dependent manner. Moreover, this flavonoid also exhibited the capacity to significantly induce apoptosis and suppress proliferation of MM cells. Interestingly, this agent also significantly potentiated the apoptotic effects of bortezomib through the suppression of STAT3 activation in MM cells. Altogether, our data indicates that the potential application of icariin as a STAT3 blocker in myeloma therapy.

Celastrol Attenuates the Invasion and Migration and Augments the Anticancer Effects of Bortezomib in a Xenograft Mouse Model of Multiple Myeloma

Several lines of evidence have demonstrated that deregulated activation of NF-κB plays a pivotal role in the initiation and progression of a variety of cancers including multiple myeloma (MM). Therefore, novel molecules that can effectively suppress deregulated NF-κB upregulation can potentially reduce MM growth. In this study, the effect of celastrol (CSL) on patient derived CD138+ MM cell proliferation, apoptosis, cell invasion, and migration was investigated. In addition, we studied whether CSL can potentiate the apoptotic effect of bortezomib, a proteasome inhibitor in MM cells and in a xenograft mouse model. We found that CSL significantly reduced cell proliferation and enhanced apoptosis when used in combination with bortezomib and upregulated caspase-3 in these cells. CSL also inhibited invasion and migration of MM cells through the suppression of constitutive NF-κB activation and expression of downstream gene products such as CXCR4 and MMP-9. Moreover, CSL when administered either alone or in combination with bortezomib inhibited MM tumor growth and decreased serum IL-6 and TNF-α levels. Overall, our results suggest that CSL can abrogate MM growth both in vitro and in vivo and may serve as a useful pharmacological agent for the treatment of myeloma and other hematological malignancies.

Chemopreventive activity of celastrol in drug-resistant human colon carcinoma cell cultures

Celastrol (tripterine) a pentacyclic triterpenoid extracted from the roots of Tripterygium wilfordii Hook f., exhibits potent antioxidant and anti-inflammatory activity and also exerts important anti-cancer effects, as induction of apoptosis and lowering the level of drug resistance of several cancers. Increased level of cellular resistance to cytostatic drugs is typical for colorectal cancers, and largely determines the failure of chemotherapy for this tumor. The purpose of our research was to evaluate the chemopreventive effect of celastrol on cultures of colon cancer cells resistant to doxorubicin (LOVO/DX). With the use of flow cytometry we have shown that celastrol reduces the cell size of the SP (side population; subpopulation of cancer cells enriched with cancer stem cells), increases frequency of apoptosis and binds to Pgp protein in cell membranes inhibiting its transport function. The inhibition of the Pgp transport function has been shown to increase the accumulation of rhodamine-123 and standard cytostatic- doxorubicin in LOVO/DX cells. Our results prove that celastrol exhibits significant chemopreventive and chemosensitizing activities on drug resistant colon cancer cells. Celastrol appears to be a good candidate for adjuvant medicine that can improve the effectiveness of standard cytostatic therapy in humans.

A Mechanistic Overview of Triptolide and Celastrol, Natural Products from Tripterygium wilfordii Hook F

Triptolide and celastrol are predominantly active natural products isolated from the medicinal plant Tripterygium wilfordii Hook F. These compounds exhibit similar pharmacological activities, including anti-cancer, anti-inflammation, anti-obesity, and anti-diabetic activities. Triptolide and celastrol also provide neuroprotection and prevent cardiovascular and metabolic diseases. However, toxicity restricts the further development of triptolide and celastrol. In this review, we comprehensively review therapeutic targets and mechanisms of action, and translational study of triptolide and celastrol. We systemically discuss the structure-activity-relationship of triptolide, celastrol, and their derivatives. Furthermore, we propose the use of structural derivatives, targeted therapy, and combination treatment as possible solutions to reduce toxicity and increase therapeutic window of these potent natural products from T. wilfordii Hook F.

New sulfurated derivatives of cinnamic acids and rosmaricine as inhibitors of STAT3 and NF-κB transcription factors

A set of new sulfurated drug hybrids, mainly derived from caffeic and ferulic acids and rosmaricine, has been synthesized and their ability to inhibit both STAT3 and NF-κB transcription factors have been evaluated. Results showed that most of the new hybrid compounds were able to strongly and selectively bind to STAT3, whereas the parent drugs were devoid of this ability at the tested concentrations. Some of them were also able to inhibit the NF-κB transcriptional activity in HCT-116 cell line and inhibited HCT-116 cell proliferation in vitro with IC50 in micromolar range, thus suggesting a potential anticancer activity. Taken together, our study described the identification of new derivatives with dual STAT3/NF-κB inhibitory activity, which may represent hit compounds for developing multi-target anticancer agents.

2,5-Dihydroxyacetophenone Induces Apoptosis of Multiple Myeloma Cells by Regulating the MAPK Activation Pathway

2,5-Dihydroxyacetophenone (DHAP) is an active compound obtained from Radix rehmanniae preparata, which is widely used as a herbal medicine in many Asian countries. DHAP has been found to possess anti-inflammatory, anti-anxiety, and neuroprotective qualities. For the present study, we evaluated the anti-cancer effects of DHAP on multiple myeloma cells. It was discovered that DHAP downregulated the expression of oncogenic gene products like Bcl-xl, Bcl-2, Mcl-1, Survivin, Cyclin D1, IAP-1, Cyclin E, COX-2, and MMP-9, and upregulated the expression of Bax and p21 proteins, consistent with the induction of G2/M phase cell cycle arrest and apoptosis in U266 cells. DHAP inhibited cell proliferation and induced apoptosis, as characterized by the cleavage of PARP and the activation of caspase-3, caspase-8, and caspase-9. Mitogen-activated protein kinase (MAPK) pathways have been linked to the modulation of the angiogenesis, proliferation, metastasis, and invasion of tumors. We therefore attempted to determine the effect of DHAP on MAPK signaling pathways, and discovered that DHAP treatment induced a sustained activation of JNK, ERK1/2, and p38 MAPKs. DHAP also potentiated the pro-apoptotic and anti-proliferative effects of bortezomib in U266 cells. Our results suggest that DHAP can be an effective therapeutic agent to target multiple myeloma.

Celastrol: A Spectrum of Treatment Opportunities in Chronic Diseases

The identification of new bioactive compounds derived from medicinal plants with significant therapeutic properties has attracted considerable interest in recent years. Such is the case of the Tripterygium wilfordii (TW), an herb used in Chinese medicine. Clinical trials performed so far using its root extracts have shown impressive therapeutic properties but also revealed substantial gastrointestinal side effects. The most promising bioactive compound obtained from TW is celastrol. During the last decade, an increasing number of studies were published highlighting the medicinal usefulness of celastrol in diverse clinical areas. Here we systematically review the mechanism of action and the therapeutic properties of celastrol in inflammatory diseases, namely, rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel diseases, osteoarthritis and allergy, as well as in cancer, neurodegenerative disorders and other diseases, such as diabetes, obesity, atherosclerosis, and hearing loss. We will also focus in the toxicological profile and limitations of celastrol formulation, namely, solubility, bioavailability, and dosage issues that still limit its further clinical application and usefulness.

Celastrol inhibits migration and invasion through blocking the NF-κB pathway in ovarian cancer cells

Metastatic ovarian cancer is a major clinical challenge with poor prognosis and high mortality. Celastrol is a natural compound that has exhibits antiproliferative activity; however, its effects on metastasis-related phenotypes in ovarian cancer models are unclear. In the current study, the anti-invasive activities and associated signaling pathways of celastrol were determined in ovarian cancer cells. Cell proliferation was tested by MTT assay. Cell migration was detected by wound healing and Transwell assays, while cell invasion was detected by a Matrigel-coated Transwell method. In addition, nuclear factor (NF)-κB and matrix metalloproteinase (MMP) expression was examined by western blotting, and MMP-2/-9 activities were determined by gelatin zymography. At sub-toxic concentrations (<0.5 µM), celastrol inhibited migration and invasion in a concentration-dependent manner in SKOV-3 and OVCAR-3 cells. At the molecular level, celastrol blocked the canonical NF-κB pathway by inhibiting IκBα phosphorylation, and preventing IκBα degradation and p65 accumulation. Furthermore, the expression and activity of the NF-κB target protein MMP-9, but not MMP-2, were inhibited by celastrol. Furthermore, celastrol showed no synergistic effect with MG132, an NF-κB inhibitor. In conclusion, celastrol exhibited significant anti-invasive activities in ovarian cancer cells. Such functions may be mediated via NF-κB pathway blockade. The results of this in vitro study strengthen the value of applying celastrol as a potential clinical intervention modality for delaying ovarian cancer metastasis. This, celastrol warrants further preclinical investigation.

Celastrol and Its Role in Controlling Chronic Diseases

Celastrol, a triterpenoid derived from traditional Chinese medicinal plants, has anti-inflammatory, antioxidant, and anticancer activities. Celastrol has shown preventive/therapeutic effects in experimental models of several chronic diseases. These include, chronic inflammatory and autoimmune diseases (e.g., rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, inflammatory bowel disease, and psoriasis), neurodegenerative disorders (e.g., Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis), atherosclerosis, obesity, Type 2 diabetes, and cancer. Celastrol modulates intricate cellular pathways and networks associated with disease pathology, and it interrupts or redirects the aberrant cellular and molecular events so as to limit disease progression and facilitate recovery, where feasible. The major cell signaling pathways modulated by celastrol include the NF-kB pathway, MAPK pathway, JAK/STAT pathway, PI3K/Akt/mTOR pathway, and antioxidant defense mechanisms. Furthermore, celastrol modulates cell proliferation, apoptosis, proteasome activity, heat-shock protein response, innate and adaptive immune responses, angiogenesis, and bone remodeling. Current understanding of the mechanisms of action of celastrol and information about its disease-modulating activities in experimental models have set the stage for testing celastrol in clinical studies as a therapeutic agent for several chronic human diseases.

Dihydrocelastrol inhibits multiple myeloma cell proliferation and promotes apoptosis through ERK1/2 and IL-6/STAT3 pathways in vitro and in vivo

Multiple myeloma (MM) is the second most frequent malignant hematological disease. Dihydrocelastrol (DHCE) is synthesized by hydrogenated celastrol, a treterpene isolated from Chinese medicinal plant Tripterygium regelii. In this study, we first reported the anti-tumor activity of DHCE on MM cells. We found that DHCE could inhibit cell proliferation and promote apoptosis through caspase-dependent way in vitro. In addition, DHCE could inactivate the expression of interleukin (IL)-6 and downregulate the phosphorylation of extracellular regulated protein kinases (ERK1/2) and the signal transducer and activator of transcription 3 (STAT3) in MM. It also retained its activity against MM cell lines in the presence of IL-6. Furthermore, treatment of MM cells with DHCE resulted in an accumulation of cells in G0/G1 phase of the cell cycle. Notably, DHCE reduced the expression of cyclin D1 and cyclin-dependent kinases 4 and 6 in MM cell lines. Additionally, its efficacy toward the MM cell lines could be enhanced in combination with the histone deacetylase inhibitor panobinostat (LBH589), which implied the possibility of the combination treatment of DHCE and LBH589 as a potential therapeutic strategy in MM. In addition, treatment of NCI-H929 tumor-bearing nude mice with DHCE (10 mg/kg/d, i.p., 1-14 days) resulted in 73% inhibition of the tumor growth in vivo. Taken together, the results of our present study indicated that DHCE could inhibit cellular proliferation and induce cell apoptosis in myeloma cells mediated through different mechanisms, possibly through inhibiting the IL-6/STAT3 and ERK1/2 pathways. And it may provide a new therapeutic option for MM patients.

Ginkgolic Acid C 17:1, Derived from Ginkgo biloba Leaves, Suppresses Constitutive and Inducible STAT3 Activation through Induction of PTEN and SHP-1 Tyrosine Phosphatase

Ginkgolic acid C 17:1 (GAC 17:1) extracted from Ginkgo biloba leaves, has been previously reported to exhibit diverse antitumor effect(s) through modulation of several molecular targets in tumor cells, however the detailed mechanism(s) of its actions still remains to be elucidated. Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor that regulates various critical functions involved in progression of diverse hematological malignancies, including multiple myeloma, therefore attenuating STAT3 activation may have a potential in cancer therapy. We determined the anti-tumor mechanism of GAC 17:1 with respect to its effect on STAT3 signaling pathway in multiple myeloma cell lines. We found that GAC 17:1 can inhibit constitutive activation of STAT3 through the abrogation of upstream JAK2, Src but not of JAK1 kinases in U266 cells and also found that GAC can suppress IL-6-induced STAT3 phosphorylation in MM.1S cells. Treatment of protein tyrosine phosphatase (PTP) inhibitor blocked suppression of STAT3 phosphorylation by GAC 17:1, thereby indicating a critical role for a PTP. We also demonstrate that GAC 17:1 can induce the substantial expression of PTEN and SHP-1 at both protein and mRNA level. Further, deletion of PTEN and SHP-1 genes by siRNA can repress the induction of PTEN and SHP-1, as well as abolished the inhibitory effect of drug on STAT3 phosphorylation. GAC 17:1 down-regulated the expression of STAT3 regulated gene products and induced apoptosis of tumor cells. Overall, GAC 17:1 was found to abrogate STAT3 signaling pathway and thus exert its anticancer effects against multiple myeloma cells.

Ascochlorin Enhances the Sensitivity of Doxorubicin Leading to the Reversal of Epithelial-to-Mesenchymal Transition in Hepatocellular Carcinoma

Increasing evidence has indicated that epithelial-to-mesenchymal transition (EMT) at the advanced stage of liver cancer not only has the ability to self-renew and progress cancer, but also enables greater resistance to conventional chemo- and radiotherapies. Here, we report that ascochlorin (ASC), an isoprenoid antibiotic, could potentiate the cytotoxic effect of doxorubicin on HCCLM3, SNU387, SNU49, and SK-Hep-1 hepatocellular carcinoma cells, which had a predominantly mesenchymal signature with low expression of E-cadherin but high expression of N-cadherin. Co-administration of ASC reduced doxorubicin-induced invasion/migration and modulated EMT characteristics in mesenchymal cells. This process was probably mediated by the E-cadherin repressors Snail and Slug. In addition, ASC increased sensitivity to doxorubicin treatment by directly inhibiting STAT3 binding to the Snail promoter. We also observed that ASC significantly enhanced the effect of doxorubicin against tumor growth and inhibited metastasis in an HCCLM3_Luc orthotopic mouse model. Collectively, our data demonstrate that ASC can increase sensitivity to doxorubicin therapy and reverse the EMT phenotype via the downregulation of STAT3-Snail expression, which could form the basis of a novel therapeutic approach against hepatocellular carcinoma. Mol Cancer Ther; 15(12); 2966-76. ©2016 AACR.

Direct inhibition of c-Myc-Max heterodimers by celastrol and celastrol-inspired triterpenoids

Many oncogenic signals originate from abnormal protein-protein interactions that are potential targets for small molecule inhibitors. However, the therapeutic disruption of these interactions has proved elusive. We report here that the naturally-occurring triterpenoid celastrol is an inhibitor of the c-Myc (Myc) oncoprotein, which is over-expressed in many human cancers. Most Myc inhibitors prevent the association between Myc and its obligate heterodimerization partner Max via their respective bHLH-ZIP domains. In contrast, we show that celastrol binds to and alters the quaternary structure of the pre-formed dimer and abrogates its DNA binding. Celastrol contains a reactive quinone methide group that promiscuously forms Michael adducts with numerous target proteins and other free sulfhydryl-containing molecules. Interestingly, triterpenoid derivatives lacking the quinone methide showed enhanced specificity and potency against Myc. As with other Myc inhibitors, these analogs rapidly reduced the abundance of Myc protein and provoked a global energy crisis marked by ATP depletion, neutral lipid accumulation, AMP-activated protein kinase activation, cell cycle arrest and apoptosis. They also inhibited the proliferation of numerous established human cancer cell lines as well as primary myeloma explants that were otherwise resistant to JQ1, a potent indirect Myc inhibitor. N-Myc amplified neuroblastoma cells showed similar responses and, in additional, underwent neuronal differentiation. These studies indicate that certain pharmacologically undesirable properties of celastrol such as Michael adduct formation can be eliminated while increasing selectivity and potency toward Myc and N-Myc. This, together with their low in vivo toxicity, provides a strong rationale for pursuing the development of additional Myc-specific triterpenoid derivatives.

Control of autoimmune inflammation by celastrol, a natural triterpenoid

Celastrol is a bioactive compound derived from traditional Chinese medicinal herbs of the Celastraceae family. Celastrol is known to possess anti-inflammatory and anti-oxidant activities. Our studies have highlighted the immunomodulatory attributes of celastrol in adjuvant-induced arthritis (AA), an experimental model of human rheumatoid arthritis (RA). RA is an autoimmune disease characterized by chronic inflammation of the synovial lining of the joints, leading eventually to tissue damage and deformities. Identification of the molecular targets of celastrol such as the NF-κB pathway, MAPK pathway, JAK/STAT pathway and RANKL/OPG pathway has unraveled its strategic checkpoints in controlling arthritic inflammation and tissue damage in AA. The pathological events that are targeted and rectified by celastrol include increased production of pro-inflammatory cytokines; an imbalance between pathogenic T helper 17 and regulatory T cells; enhanced production of chemokines coupled with increased migration of immune cells into the joints; and increased release of mediators of osteoclastic bone damage. Accordingly, celastrol is a promising candidate for further testing in the clinic for RA therapy. Furthermore, the results of other preclinical studies suggest that celastrol might also be beneficial for the treatment of a few other autoimmune diseases besides arthritis.

Mangiferin enhances the sensitivity of human multiple myeloma cells to anticancer drugs through suppression of the nuclear factor κB pathway

Multiple myeloma (MM) is still an incurable hematological malignancy with a 5-year survival rate of ~35%, despite the use of various treatment options. The nuclear factor κB (NF-κB) pathway plays a crucial role in the pathogenesis of MM. Thus, inhibition of the NF-κB pathway is a potential target for the treatment of MM. In a previous study, we showed that mangiferin suppressed the nuclear translocation of NF-κB. However, the treatment of MM involves a combination of two or three drugs. In this study, we examined the effect of the combination of mangiferin and conventional anticancer drugs in an MM cell line. We showed that the combination of mangiferin and an anticancer drug decreased the viability of MM cell lines in comparison with each drug used separately. The decrease in the combination of mangiferin and an anticancer drug induced cell viability was attributed to increase the expression of p53 and Noxa and decreases the expression of XIAP, survivin, and Bcl-xL proteins via inhibition of NF-κB pathway. In addition, the combination treatment caused the induction of apoptosis, activation of caspase-3 and the accumulation of the cells in the sub-G1 phase of the cell cycle. Our findings suggest that the combination of mangiferin and an anticancer drug could be used as a new regime for the treatment of MM.

Analysis of the intricate relationship between chronic inflammation and cancer

Deregulated inflammatory response plays a pivotal role in the initiation, development and progression of tumours. Potential molecular mechanism(s) that drive the establishment of an inflammatory-tumour microenvironment is not entirely understood owing to the complex cross-talk between pro-inflammatory and tumorigenic mediators such as cytokines, chemokines, oncogenes, enzymes, transcription factors and immune cells. These molecular mediators are critical linchpins between inflammation and cancer, and their activation and/or deactivation are influenced by both extrinsic (i.e. environmental and lifestyle) and intrinsic (i.e. hereditary) factors. At present, the research pertaining to inflammation-associated cancers is accumulating at an exponential rate. Interest stems from hope that new therapeutic strategies against molecular mediators can be identified to assist in cancer treatment and patient management. The present review outlines the various molecular and cellular inflammatory mediators responsible for tumour initiation, progression and development, and discusses the critical role of chronic inflammation in tumorigenesis.

Dietary phytochemicals alter epigenetic events and signaling pathways for inhibition of metastasis cascade: phytoblockers of metastasis cascade

Cancer metastasis is a multistep process in which a cancer cell spreads from the site of the primary lesion, passes through the circulatory system, and establishes a secondary tumor at a new nonadjacent organ or part. Inhibition of cancer progression by dietary phytochemicals (DPs) offers significant promise for reducing the incidence and mortality of cancer. Consumption of DPs in the diet has been linked to a decrease in the rate of metastatic cancer in a number of preclinical animal models and human epidemiological studies. DPs have been reported to modulate the numerous biological events including epigenetic events (noncoding micro-RNAs, histone modification, and DNA methylation) and multiple signaling transduction pathways (Wnt/β-catenin, Notch, Sonic hedgehog, COX-2, EGFR, MAPK-ERK, JAK-STAT, Akt/PI3K/mTOR, NF-κB, AP-1, etc.), which can play a key role in regulation of metastasis cascade. Extensive studies have also been performed to determine the molecular mechanisms underlying antimetastatic activity of DPs, with results indicating that these DPs have significant inhibitory activity at nearly every step of the metastatic cascade. DPs have anticancer effects by inducing apoptosis and by inhibiting cell growth, migration, invasion, and angiogenesis. Growing evidence has also shown that these natural agents potentiate the efficacy of chemotherapy and radiotherapy through the regulation of multiple signaling pathways. In this review, we discuss the variety of molecular mechanisms by which DPs regulate metastatic cascade and highlight the potentials of these DPs as promising therapeutic inhibitors of cancer.

A Review: Phytochemicals Targeting JAK/STAT Signaling and IDO Expression in Cancer

Cancer remains a major health problem worldwide. Among many other factors, two regulatory defects that are present in most cancer cells are constitutive activation of Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway and the induction of indoleamine 2, 3-dioxygenase (IDO), an enzyme that catalyzes tryptophan degradation, through JAK/STAT signaling. Cytokine signaling activates STAT proteins in regulating cell proliferation, differentiation, and survival through modulation of target genes. Many phytochemicals can inhibit both JAK/STAT signaling and IDO expression in antigen-presenting cells by targeting different pathways. Some of the promising phytochemicals that are discussed in this review include resveratrol, cucurbitacin, curcumin, (-)-epigallocatechin gallate, and others. It is now evident that phytochemicals play key roles in inhibition of tumor proliferation and development and provide novel means for therapeutic targeting of cancer.

Overexpression of caudal type homeobox transcription factor 2 inhibits the growth of the MGC-803 human gastric cancer cell line in vivo

Caudal type homeobox transcription factor 2 (CDX2) is important in intestinal cell fate specification and multiple lines of evidence have substantiated that CDX2 is important in carcinogenesis of the digestive tract. The CDX2 regulatory network is intricate and remains to be fully elucidated in gastric cancer. The aim of the present study was to examine the effects of CDX2 on the growth of the MGC-803 human gastric cancer cell line in vivo, and to elucidate the mechanism involved. The effects of the overexpression of CDX2 in xenograft tumors of MGC-803 cells was investigated in nude mice through the injection of CDX2 recombinant lentiviral vectors. The tumor size was measured using vernier callipers. The expression levels of CDX2, survivin, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), cyclin D1, s-phase kinase-associated protein 2 (Skp2) and c-Myc in the tumor cells were analyzed by western blotting and semi-quantitative reverse transcription polymerase chain reaction. The apoptotic rates were determined using a terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay. The overexpression of CDX2 was observed in the group subjected to the injection of CDX2 recombinant lentiviral vectors. CDX2 had an inhibitory effect on the MGC-803 human gastric cancer cell line and promoted tumor cell apoptosis in vivo. Furthermore, the overexpression of CDX2 upregulated the expression of Bax and downregulated the expression levels of survivin, Bcl-2, cyclin D1, Skp2 and c-Myc in the tumor tissues. These results indicated that CDX2 may serve as a tumor suppressor in gastric cancer, and inhibits gastric cancer cell growth by suppressing the nuclear factor-κB signaling pathway.

Thymoquinone overcomes chemoresistance and enhances the anticancer effects of bortezomib through abrogation of NF-κB regulated gene products in multiple myeloma xenograft mouse model

Multiple myeloma (MM) is a B cell malignancy characterized by clonal proliferation of plasma cells in the bone marrow. With the advent of novel targeted agents, the median survival rate has increased to 5−7 years. However, majority of patients with myeloma suffer relapse or develop chemoresistance to existing therapeutic agents. Thus, there is a need to develop novel alternative therapies for the treatment of MM. Thus in the present study, we investigated whether thymoquinone (TQ), a bioactive constituent of black seed oil, could suppress the proliferation and induce chemosensitization in human myeloma cells and xenograft mouse model. Our results show that TQ inhibited the proliferation of MM cells irrespective of their sensitivity to doxorubicin, melphalan or bortezomib. Interestingly, TQ treatment also resulted in a significant inhibition in the proliferation of CD138+ cells isolated from MM patient samples in a concentration dependent manner. TQ also potentiated the apoptotic effects of bortezomib in various MM cell lines through the activation of caspase-3, resulting in the cleavage of PARP. TQ treatment also inhibited chemotaxis and invasion induced by CXCL12 in MM cells. Furthermore, in a xenograft mouse model, TQ potentiated the antitumor effects of bortezomib (p < 0.05, vehicle versus bortezomib + TQ; p < 0.05, bortezomib versus bortezomib + TQ), and this correlated with modulation of various markers for survival and angiogenesis, such as Ki-67, vascular endothelial growth factor (VEGF), Bcl-2 and p65 expression. Overall, our results demonstrate that TQ can enhance the anticancer activity of bortezomib in vitro and in vivo and may have a substantial potential in the treatment of MM.

Metabolic and functional diversity of saponins, biosynthetic intermediates and semi-synthetic derivatives

Saponins are widely distributed plant natural products with vast structural and functional diversity. They are typically composed of a hydrophobic aglycone, which is extensively decorated with functional groups prior to the addition of hydrophilic sugar moieties, to result in surface-active amphipathic compounds. The saponins are broadly classified as triterpenoids, steroids or steroidal glycoalkaloids, based on the aglycone structure from which they are derived. The saponins and their biosynthetic intermediates display a variety of biological activities of interest to the pharmaceutical, cosmetic and food sectors. Although their relevance in industrial applications has long been recognized, their role in plants is underexplored. Recent research on modulating native pathway flux in saponin biosynthesis has demonstrated the roles of saponins and their biosynthetic intermediates in plant growth and development. Here, we review the literature on the effects of these molecules on plant physiology, which collectively implicate them in plant primary processes. The industrial uses and potential of saponins are discussed with respect to structure and activity, highlighting the undoubted value of these molecules as therapeutics.

Knockdown of DNA methyltransferase-1 inhibits proliferation and derepresses tumor suppressor genes in myeloma cells

DNA methyltransferases (including DNMT1, DNMT3A and DNMT3B), catalyze the transfer of methyl groups from S-adenosyl-l-methionine to cytosine position 5; this methylation in promoter regions silences gene expression. In addition, DNMT1 plays a critical role in the maintenance of genomic DNA methylation during DNA replication. In the present study, silencing of DNMT1 with siRNA was performed in RPMI-8226 human multiple myeloma (MM) cells, and the impact on gene methylation status and proliferation of the cells was analyzed. Upon DNMT1 downregulation, proliferation decreased significantly compared with that in the control, non-transfected cells. The expression of B-cell lymphoma 2 and nuclear factor κB proteins was also significantly reduced. Furthermore, nested methylation-specific polymerase chain reaction revealed that methylation of the tumor suppressor genes, suppressor of cytokine signaling 1 and p16, was significantly reduced upon DNMT1 knockdown. Our results suggest that DNMT1 silencing may be a promising strategy to consider during development of novel MM treatment strategies.

Bergamottin, a natural furanocoumarin obtained from grapefruit juice induces chemosensitization and apoptosis through the inhibition of STAT3 signaling pathway in tumor cells

Persistent activation of signal transducers and activator of transcription 3 (STAT3) has been closely related to growth, survival, proliferation, metastasis, and angiogenesis of various cancer cells, and thus its inhibition can be considered a potential therapeutic strategy. In this study, we investigated the role of bergamottin (BGM) obtained from grapefruit juice in abrogating the constitutive STAT3 activation in multiple myeloma (MM) cells. This suppression was mediated through the inhibition of phosphorylation of Janus-activated kinase (JAK) 1/2 and c-Src. Pervanadate reversed the BGM induced down-regulation of STAT3 activation, suggesting the involvement of a protein tyrosine phosphatase (PTP). Furthermore, BGM induced the expression of the tyrosine phosphatase SHP-1, and gene silencing of the SHP-1 by small interfering RNA abolished the ability of BGM to inhibit STAT3 activation, suggesting a critical role for SHP-1 in the action of BGM. BGM also downregulated the expression of STAT3-regulated gene products such as COX-2, VEGF, cyclin D1, survivin, IAP-1, Bcl-2, and Bcl-xl in MM cells. This correlated with induction of substantial apoptosis as indicated by an increase in the sub-G1 cell population and caspase-3 induced PARP cleavage. Also, this agent significantly potentiated the apoptotic effects of bortezomib and thalidomide in MM cells. Overall, these results suggest that BGM is a novel blocker of STAT3 activation pathway thus may have a potential in therapy of MM and other cancers.

Negative regulation of signal transducer and activator of transcription-3 signalling cascade by lupeol inhibits growth and induces apoptosis in hepatocellular carcinoma cells

Background:

Constitutive activation of signal transducer and activator of transcription signalling 3 (STAT3) has been linked with survival, proliferation and angiogenesis in a wide variety of malignancies including hepatocellular carcinoma (HCC).

Methods:

We evaluated the effect of lupeol on STAT3 signalling cascade and its regulated functional responses in HCC cells.

Results:

Lupeol suppressed constitutive activation of STAT3 phosphorylation at tyrosine 705 residue effectively in a dose- and time-dependent manner. The phosphorylation of Janus-activated kinases (JAKs) 1 and 2 and Src was also suppressed by lupeol. Pervanadate treatment reversed the downregulation of phospho-STAT3 induced by lupeol, thereby indicating the involvement of a phosphatase. Indeed, we observed that treatment with lupeol increased the protein and mRNA levels of SHP-2, and silencing of SHP-2 abolished the inhibitory effects of lupeol on STAT3 activation. Treatment with lupeol also downregulated the expression of diverse STAT3-regulated genes and decreased the binding of STAT3 to VEGF promoter. Moreover, the proliferation of various HCC cells was significantly suppressed by lupeol, being associated with substantial induction of apoptosis. Depletion of SHP-2 reversed the observed antiproliferative and pro-apoptotic effects of lupeol.

Conclusions:

Lupeol exhibited its potential anticancer effects in HCC through the downregulation of STAT3-induced pro-survival signalling cascade.

Kaempferol, a potential cytostatic and cure for inflammatory disorders

Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is a flavonoid found in many edible plants (e.g., tea, broccoli, cabbage, kale, beans, endive, leek, tomato, strawberries, and grapes) and in plants or botanical products commonly used in traditional medicine (e.g., Ginkgo biloba, Tilia spp, Equisetum spp, Moringa oleifera, Sophora japonica and propolis). Its anti-oxidant/anti-inflammatory effects have been demonstrated in various disease models, including those for encephalomyelitis, diabetes, asthma, and carcinogenesis. Moreover, kaempferol act as a scavenger of free radicals and superoxide radicals as well as preserve the activity of various anti-oxidant enzymes such as catalase, glutathione peroxidase, and glutathione-S-transferase. The anticancer effect of this flavonoid is mediated through different modes of action, including anti-proliferation, apoptosis induction, cell-cycle arrest, generation of reactive oxygen species (ROS), and anti-metastasis/anti-angiogenesis activities. In addition, kaempferol was found to exhibit its anticancer activity through the modulation of multiple molecular targets including p53 and STAT3, through the activation of caspases, and through the generation of ROS. The anti-tumor effects of kaempferol have also been investigated in tumor-bearing mice. The combination of kaempferol and conventional chemotherapeutic drugs produces a greater therapeutic effect than the latter, as well as reduces the toxicity of the latter. In this review, we summarize the anti-oxidant/anti-inflammatory and anticancer effects of kaempferol with a focus on its molecular targets and the possible use of this flavonoid for the treatment of inflammatory diseases and cancer.

In silico modeling predicts drug sensitivity of patient-derived cancer cells

BACKGROUND

Glioblastoma (GBM) is an aggressive disease associated with poor survival. It is essential to account for the complexity of GBM biology to improve diagnostic and therapeutic strategies. This complexity is best represented by the increasing amounts of profiling ("omics") data available due to advances in biotechnology. The challenge of integrating these vast genomic and proteomic data can be addressed by a comprehensive systems modeling approach.

METHODS

Here, we present an in silico model, where we simulate GBM tumor cells using genomic profiling data. We use this in silico tumor model to predict responses of cancer cells to targeted drugs. Initially, we probed the results from a recent hypothesis-independent, empirical study by Garnett and co-workers that analyzed the sensitivity of hundreds of profiled cancer cell lines to 130 different anticancer agents. We then used the tumor model to predict sensitivity of patient-derived GBM cell lines to different targeted therapeutic agents.

RESULTS

Among the drug-mutation associations reported in the Garnett study, our in silico model accurately predicted ~85% of the associations. While testing the model in a prospective manner using simulations of patient-derived GBM cell lines, we compared our simulation predictions with experimental data using the same cells in vitro. This analysis yielded a ~75% agreement of in silico drug sensitivity with in vitro experimental findings.

CONCLUSIONS

These results demonstrate a strong predictability of our simulation approach using the in silico tumor model presented here. Our ultimate goal is to use this model to stratify patients for clinical trials. By accurately predicting responses of cancer cells to targeted agents a priori, this in silico tumor model provides an innovative approach to personalizing therapy and promises to improve clinical management of cancer.

Predictive simulation approach for designing cancer therapeutic regimens with novel biological mechanisms

Introduction Ursolic acid (UA) is a pentacyclic triterpene acid present in many plants, including apples, basil, cranberries, and rosemary. UA suppresses proliferation and induces apoptosis in a variety of tumor cells via inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB). Given that single agent therapy is a major clinical obstacle to overcome in the treatment of cancer, we sought to enhance the anti-cancer efficacy of UA through rational design of combinatorial therapeutic regimens that target multiple signaling pathways critical to carcinogenesis.

Methodology Using a predictive simulation-based approach that models cancer disease physiology by integrating signaling and metabolic networks, we tested the effect of UA alone and in combination with 100 other agents across cell lines from colorectal cancer, non-small cell lung cancer and multiple myeloma. Our predictive results were validated in vitro using standard molecular assays. The MTT assay and flow cytometry were used to assess cellular proliferation. Western blotting was used to monitor the combinatorial effects on apoptotic and cellular signaling pathways. Synergy was analyzed using isobologram plots.

Results We predictively identified c-Jun N-terminal kinase (JNK) as a pathway that may synergistically inhibit cancer growth when targeted in combination with NFκB. UA in combination with the pan-JNK inhibitor SP600125 showed maximal reduction in viability across a panel of cancer cell lines, thereby corroborating our predictive simulation assays. In HCT116 colon carcinoma cells, the combination caused a 52% reduction in viability compared with 18% and 27% for UA and SP600125 alone, respectively. In addition, isobologram plot analysis reveals synergy with lowered doses of the drugs in combination. The combination synergistically inhibited proliferation and induced apoptosis as evidenced by an increase in the percentage sub-G1 phase cells and cleavage of caspase 3 and poly ADP ribose polymerase (PARP). Combination treatment resulted in a significant reduction in the expression of cyclin D1 and c-Myc as compared with single agent treatment.

Conclusions Our findings underscore the importance of targeting NFκB and JNK signaling in combination in cancer cells. These results also highlight and validate the use of predictive simulation technology to design therapeutics for targeting novel biological mechanisms using existing or novel chemistry.

Gö6976, a FLT3 kinase inhibitor, exerts potent cytotoxic activity against acute leukemia via inhibition of survivin and MCL-1

Mutations of the FMS-like tyrosine kinase 3 (FLT3) have been reported in about a third of patients with acute myeloid leukemia (AML). The presence of FLT3 mutations confers a poor prognosis. Thus, pharmacological inhibitors of FLT3 are of therapeutic interest for AML. Gö6976 is an indolocarbazole with a similar structural backbone to staurosporine. In the present study, we demonstrated that Gö6976 displays a potent inhibitory activity against recombinant FLT3 using an in vitro kinase assay, with an IC50 value of 0.7nM. Gö6976 markedly inhibited the proliferation of human leukemia cells having FLT3-ITD such as MV4-11 and MOLM13. We also observed that Gö6976 showed minimal toxicity for human normal CD34(+) cells. Gö6976 suppressed the phosphorylation of FLT3 and downstream signaling molecules such as STAT3/5, Erk1/2, and Akt in MV4-11 and MOLM13 cells. Interestingly, induction of apoptosis by Gö6976 was associated with rapid and pronounced down-regulation of the anti-apoptotic protein survivin and MCL-1. Suppression of survivin protein expression by Gö6976 was due to the inhibition of transcription via the suppression of STAT3/5. On the other hand, Gö6976 induced proteasome-mediated degradation of MCL-1. Previously described FLT3 inhibitors such as PKC412 are bound by the human plasma protein, α1-acid glycoprotein, resulting in diminished inhibitory activity against FLT3. In contrast, we found that Gö6976 potently inhibited phosphorylation of FLT3 and exerted cytotoxicity in the presence of human serum. In conclusion, Gö6976 is a potent FLT3 inhibitor that displays a significant antiproliferative activity against leukemia cells with FLT3-ITD through the profound down-regulation of survivin and MCL-1.

Evaluation of traditional medicines for neurodegenerative diseases using Drosophila models

Drosophila is one of the oldest and most powerful genetic models and has led to novel insights into a variety of biological processes. Recently, Drosophila has emerged as a model system to study human diseases, including several important neurodegenerative diseases. Because of the genomic similarity between Drosophila and humans, Drosophila neurodegenerative disease models exhibit a variety of human-disease-like phenotypes, facilitating fast and cost-effective in vivo genetic modifier screening and drug evaluation. Using these models, many disease-associated genetic factors have been identified, leading to the identification of compelling drug candidates. Recently, the safety and efficacy of traditional medicines for human diseases have been evaluated in various animal disease models. Despite the advantages of the Drosophila model, its usage in the evaluation of traditional medicines is only nascent. Here, we introduce the Drosophila model for neurodegenerative diseases and some examples demonstrating the successful application of Drosophila models in the evaluation of traditional medicines.

Sensitization of U937 leukemia cells to doxorubicin by the MG132 proteasome inhibitor induces an increase in apoptosis by suppressing NF-kappa B and mitochondrial membrane potential loss

Background

The resistance of cancerous cells to chemotherapy remains the main limitation for cancer treatment at present. Doxorubicin (DOX) is a potent antitumor drug that activates the ubiquitin-proteasome system, but unfortunately it also activates the Nuclear factor kappa B (NF-кB) pathway leading to the promotion of tumor cell survival. MG132 is a drug that inhibits I kappa B degradation by the proteasome-avoiding activation of NF-кB. In this work, we studied the sensitizing effect of the MG132 proteasome inhibitor on the antitumor activity of DOX.

Methods

U937 human leukemia cells were treated with MG132, DOX, or both drugs. We evaluated proliferation, viability, apoptosis, caspase-3, -8, and −9 activity and cleavage, cytochrome c release, mitochondrial membrane potential, the Bcl-2 and Bcl-XL antiapoptotic proteins, senescence, p65 phosphorylation, and pro- and antiapoptotic genes.

Results

The greatest apoptosis percentage in U937 cells was obtained with a combination of MG132 + DOX. Likewise, employing both drugs, we observed a decrease in tumor cell proliferation and important caspase-3 activation, as well as mitochondrial membrane potential loss. Therefore, MG132 decreases senescence, p65 phosphorylation, and the DOX-induced Bcl-2 antiapoptotic protein. The MG132 + DOX treatment induced upregulation of proapoptotic genes BAX, DIABLO, NOXA, DR4, and FAS. It also induced downregulation of the antiapoptotic genes BCL-XL and SURVIVIN.

Conclusion

MG132 sensitizes U937 leukemia cells to DOX-induced apoptosis, increasing its anti-leukemic effectiveness.

Targeting the STAT3 signaling pathway in cancer: role of synthetic and natural inhibitors

Signal transducers and activators of transcription (STATs) comprise a family of cytoplasmic transcription factors that mediate intracellular signaling that is usually generated at cell surface receptors and thereby transmit it to the nucleus. Numerous studies have demonstrated constitutive activation of STAT3 in a wide variety of human tumors, including hematological malignancies (leukemias, lymphomas, and multiple myeloma) as well as diverse solid tumors (such as head and neck, breast, lung, gastric, hepatocellular, colorectal and prostate cancers). There is strong evidence to suggest that aberrant STAT3 signaling promotes initiation and progression of human cancers by either inhibiting apoptosis or inducing cell proliferation, angiogenesis, invasion, and metastasis. Suppression of STAT3 activation results in the induction of apoptosis in tumor cells, and accordingly its pharmacological modulation by tyrosine kinase inhibitors, antisense oligonucleotides, decoy nucleotides, dominant negative proteins, RNA interference and chemopreventive agents have been employed to suppress the proliferation of various human cancer cells in culture and tumorigenicity in vivo. However, the identification and development of novel drugs that can target deregulated STAT3 activation effectively remains an important scientific and clinical challenge. This review presents the evidence for critical roles of STAT3 in oncogenesis and discusses the potential for development of novel cancer therapies based on mechanistic understanding of STAT3 signaling cascade.

Therapeutic modulators of STAT signalling for human diseases

The signal transducer and activator of transcription (STAT) proteins have important roles in biological processes. The abnormal activation of STAT signalling pathways is also implicated in many human diseases, including cancer, autoimmune diseases, rheumatoid arthritis, asthma and diabetes. Over a decade has passed since the first inhibitor of a STAT protein was reported and efforts to discover modulators of STAT signalling as therapeutics continue. This Review discusses the outcomes of the ongoing drug discovery research endeavours against STAT proteins, provides perspectives on new directions for accelerating the discovery of drug candidates, and highlights the noteworthy candidate therapeutics that have progressed to clinical trials.

Celastrol inhibits lipopolysaccharide-induced angiogenesis by suppressing TLR4-triggered nuclear factor-kappa B activation

Celastrol is an active compound extracted from the root bark of the traditional Chinese medicine Tripterygium wilfordii Hook F. In this study, we investigated the effect of celastrol on lipopolysaccharide (LPS)-activated LP-1 human multiple myeloma cell-induced angiogenesis, and identified its molecular mechanism of action. Migration of human umbilical vein endothelial cells (HUVECs) was tested using a wound-healing assay. HUVEC invasion was assayed using a Transwell chamber. Cell surface expression of Toll-like receptor 4 (TLR4) was analyzed by flow cytometry. Angiogenic factor vascular endothelial growth factor (VEGF) level was quantified by LUMINEX and protein expression was analyzed by Western blot. Translocation of nuclear factor-kappa B (NF-κB) was observed by fluorescence microscopy. Celastrol inhibited LPS-stimulated LP-1 human multiple myeloma-induced HUVEC migration and invasion in a concentration-dependent manner. Wound diameters increased by 72.9, 165.4 and 246.2% at 0.025, 0.05 and 0.1 μM, respectively, compared to LPS alone. A 45-74% inhibition of LPS-dependent cell invasion was achieved in the presence of 0.025-0.1 μM celastrol. Celastrol significantly downregulated LPS-induced TLR4 expression and inhibited LPS-induced VEGF secretion in LP-1 cells. VEGF levels decreased by 64.8, 84.4 and 92.9% after coexposure to celastrol at 0.025, 0.05 and 0.1 μM, respectively, compared to LPS alone. Celastrol also inhibited the IκB kinase (IKK)/NF-κB pathway induced by LPS. Protein levels of NF-κB p65, IKKα and IκB-α decreased in a dose-dependent manner after coexposure to celastrol. Celastrol also blocked nuclear translocation of the p65 subunit. These results suggest that celastrol inhibits LPS-induced angiogenesis by suppressing TLR4-triggered NF-κB activation.

Garcinol, a polyisoprenylated benzophenone modulates multiple proinflammatory signaling cascades leading to the suppression of growth and survival of head and neck carcinoma

Constitutive activation of proinflammatory transcription factors such as STAT3 and NF-κB plays a pivotal role in the proliferation and survival of squamous cell carcinoma of the head and neck (HNSCC). Thus, the agents that can modulate deregulated STAT3 and NF-κB activation have a great potential both for the prevention and treatment of HNSCC. In the present report, we investigated the potential effects of garcinol, an active component of Garcinia indica on various inflammatory mediators involved in HNSCC progression using cell lines and xenograft mouse model. We found that garcinol inhibited constitutively activated STAT3 in HNSCC cells in a time- and dose-dependent manner, which correlated with the suppression of the upstream kinases (c-Src, JAK1, and JAK2) in HNSCC cells. Also, we noticed that the generation of reactive oxygen species is involved in STAT3 inhibitory effect of garcinol. Furthermore, garcinol exhibited an inhibitory effect on the constitutive NF-κB activation, mediated through the suppression of TGF-β-activated kinase 1 (TAK1) and inhibitor of IκB kinase (IKK) activation in HNSCC cells. Garcinol also downregulated the expression of various gene products involved in proliferation, survival, and angiogenesis that led to the reduction of cell viability and induction of apoptosis in HNSCC cells. When administered intraperitoneally, garcinol inhibited the growth of human HNSCC xenograft tumors in male athymic nu/nu mice. Overall, our results suggest for the first time that garcinol mediates its antitumor effects in HNSCC cells and mouse model through the suppression of multiple proinflammatory cascades.