Abrogation of IL-6-mediated JAK signalling by the cyclopentenone prostaglandin 15d-PGJ(2) in oral squamous carcinoma cells

Trinity of inflammation, innate immune cells and cross-talk of signalling pathways in tumour microenvironment

Unresolved inflammation is a pathological consequence of persistent inflammatory stimulus and perturbation in regulatory mechanisms. It increases the risk of tumour development and orchestrates all stages of tumorigenesis in selected organs. In certain cancers, inflammatory processes create the appropriate conditions for neoplastic transformation. While in other types, oncogenic changes pave the way for an inflammatory microenvironment that leads to tumour development. Of interest, hallmarks of tumour-promoting and cancer-associated inflammation are striking similar, sharing a complex network of stromal (fibroblasts and vascular cells) and inflammatory immune cells that collectively form the tumour microenvironment (TME). The cross-talks of signalling pathways initially developed to support homeostasis, change their role, and promote atypical proliferation, survival, angiogenesis, and subversion of adaptive immunity in TME. These transcriptional and regulatory pathways invariably contribute to cancer-promoting inflammation in chronic inflammatory disorders and foster "smouldering" inflammation in the microenvironment of various tumour types. Besides identifying common target sites of numerous cancer types, signalling programs and their cross-talks governing immune cells' plasticity and functional diversity can be used to develop new fate-mapping and lineage-tracing mechanisms. Here, we review the vital molecular mechanisms and pathways that establish the connection between inflammation and tumour development, progression, and metastasis. We also discussed the cross-talks between signalling pathways and devised strategies focusing on these interaction mechanisms to harness synthetic lethal drug combinations for targeted cancer therapy.

PPAR-γ Partial Agonists in Disease-Fate Decision with Special Reference to Cancer

Peroxisome proliferator-activated receptor-γ (PPAR-γ) has emerged as one of the most extensively studied transcription factors since its discovery in 1990, highlighting its importance in the etiology and treatment of numerous diseases involving various types of cancer, type 2 diabetes mellitus, autoimmune, dermatological and cardiovascular disorders. Ligands are regarded as the key determinant for the tissue-specific activation of PPAR-γ. However, the mechanism governing this process is merely a contradictory debate which is yet to be systematically researched. Either these receptors get weakly activated by endogenous or natural ligands or leads to a direct over-activation process by synthetic ligands, serving as complete full agonists. Therefore, fine-tuning on the action of PPAR-γ and more subtle modulation can be a rewarding approach which might open new avenues for the treatment of several diseases. In the recent era, researchers have sought to develop safer partial PPAR-γ agonists in order to dodge the toxicity induced by full agonists, akin to a balanced activation. With a particular reference to cancer, this review concentrates on the therapeutic role of partial agonists, especially in cancer treatment. Additionally, a timely examination of their efficacy on various other disease-fate decisions has been also discussed.

IL-6 in the Ecosystem of Head and Neck Cancer: Possible Therapeutic Perspectives

Interleukin-6 (IL-6) is a highly potent cytokine involved in multiple biological processes. It was previously reported to play a distinct role in inflammation, autoimmune and psychiatric disorders, ageing and various types of cancer. Furthermore, it is understood that IL-6 and its signaling pathways are substantial players in orchestrating the cancer microenvironment. Thus, they appear to be potential targets in anti-tumor therapy. The aim of this article is to elucidate the role of IL-6 in the tumor ecosystem and to review the possible therapeutic approaches in head and neck cancer.

Identification of a 14-Gene Prognostic Signature for Diffuse Large B Cell Lymphoma (DLBCL)

Although immunotherapy is a potential strategy to resist cancers, due to the inadequate acknowledge, this treatment is not always effective for diffuse large B cell lymphoma (DLBCL) patients. Based on the current situation, it is critical to systematically investigate the immune pattern. According to the result of univariate and multivariate cox proportional hazards, LASSO regression and Kaplan-Meier survival analysis on immune-related genes (IRGs), a prognostic signature, containing 14 IRGs (AQP9, LMBR1L, FGF20, TANK, CRP, ORM1, JAK1, BACH2, MTCP1, IFITM1, TNFSF10, FGF12, RFX5, and LAP3), was built. This model was validated by external data, and performed well. DLBCL patients were divided into low- and high-risk groups, according to risk scores from risk formula. The results of CIBERSORT showed that different immune status and infiltration pattern were observed in these two groups. Gene set enrichment analysis (GSEA) indicated 12 signaling pathways were significantly enriched in the high-risk group, such as natural killer cell-mediated cytotoxicity, toll-like receptor signaling pathway, and so on. In summary, 14 clinically significant IRGs were screened to build a risk score formula. This formula was an accurate tool to provide a certain basis for the treatment of DLBCL patients.

15-Deoxy-Δ12,14 -prostaglandin J2 binds and inactivates STAT3 via covalent modification of cysteine 259 in H-Ras-transformed human breast epithelial cells

Signal transducer and activator of transcription 3 (STAT3) has been considered as a potential target for development of anticancer therapeutics. Here, we report a novel mechanism by which the cyclopentenone prostaglandin, 15-deoxy-Δ^12,14 -prostaglandin J₂ (15d-PGJ₂ ) functions as an allosteric inhibitor of STAT3. 15d-PGJ₂ inhibits phosphorylation, dimerization, nuclear translocation, and transcriptional activity of STAT3 in H-Ras-transformed human mammary epithelial cells (MCF10A-Ras) through the Michael addition reaction at cysteine 259 of STAT3. Comparative studies with 15d-PGJ₂ analogues reveal that both C12-C13 and C9-C10 double bonds conjugated to the carbonyl group in the cyclopentenone ring of 15d-PGJ₂ are essential for STAT3 binding. Antiproliferative and pro-apoptotic activities of 15d-PGJ₂ in MCF10A-Ras cells are attributable to covalent modification of STAT3 on Cys259, and mimic the effects induced by mutation of this amino acid.

Association Between Interleukin-6 and Head and Neck Squamous Cell Carcinoma: A Systematic Review

Interleukin-6 (IL-6) is a proinflammatory cytokine which plays an important role in several regulatory mechanisms of cancer. Moreover, experimental and clinical studies have reported that IL-6 targeted therapies might provide significant benefits for cancer treatment. The purpose of this systematic review is to evaluate IL-6 activity in patients with head and neck squamous cell carcinoma (HNSCC). A systematic review of the association between serum, saliva and tumor IL-6 and HNSCC was developed on PubMed/Medline in the publication range from January 1995 to January 2019. Our literature analysis demonstrated that overexpression and elevated serum and/or saliva IL-6 concentrations in patients with HNSCC are related to poor survival and oncological outcomes. Although there is a correlation between IL-6 concentrations and tumorigenicity, it is noteworthy that IL-6 targeted therapies are generally performed in vitro and in experimental studies. Therefore, prospective, randomized clinical trials are required that focus on IL-6 targeted therapies for the treatment of HNSCC.

Akt1 and Jak1 siRNA based silencing effects on the proliferation and apoptosis in head and neck squamous cell carcinoma

Based on Akt1 and Jak1 key roles in apoptosis and proliferation of many cancers, the aim of this study was to find a new gene therapy strategy by silencing of these main anti-apoptotic genes for HNSCC treatment. Cancerous HN5 and normal HUVEC cell lines were treated with Akt1 and Jak1 siRNAs alone or with each other combined with/without cisplatin. The MTS, flow cytometry, 4',6-diamidino-2-phenylindole staining, real-time PCR and ELISA methods were utilized in this study. The highest percentage of apoptosis was observed in the treatment of Jak1 siRNA/cisplatin group in cancerous HN5 cells (96.5%) where this treatment showed 12.84% apoptosis in normal HUVEC cell line. Cell viability reduced significantly to 64.57% after treatment with Akt1 siRNA in HN5 treated group. Knocking down Akt1 and Jak1 genes using siRNAs could increase levels of apoptosis and reduce proliferation rate in HNSCC indicating the powerful effects of these genes siRNAs with or without chemotherapeutic agents in HNSCC treatment. In conclusion, the combination of siRNA-mediated gene-silencing strategy can be considered as a valuable and safe approach for sensitizing cancer cells to chemotherapeutic agents thus proposed further studies regarding this issue to approve some siRNA based therapeutics for using in clinic.

15-Deoxy-Δ12,14-Prostaglandin J2 Modifies Components of the Proteasome and Inhibits Inflammatory Responses in Human Endothelial Cells

15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) is an electrophilic lipid mediator derived from PGD₂ with potent anti-inflammatory effects. These are likely to be due to the covalent modification of cellular proteins, via a reactive α,β-unsaturated carbonyl group in its cyclopentenone ring. This study was carried out to identify novel cellular target(s) for covalent modification by 15d-PGJ₂ and to investigate the anti-inflammatory effects of the prostaglandin on endothelial cells (EC). The data presented here show that 15d-PGJ₂ modifies and inhibits components of the proteasome and consequently inhibits the activation of the NF-κB pathway in response to TNF-α. This, in turn, inhibits the adhesion and migration of monocytes toward activated EC, by reducing the expression of adhesion molecules and chemokines in the EC. The effects are consistent with the covalent modification of 13 proteins in the 19S particle of the proteasome identified by mass spectrometry and the suppression of proteasome function, and were similar to the effects seen with a known proteasome inhibitor (MG132). The ubiquitin-proteasome system has been implicated in the regulation of several inflammatory processes and the observation that 15d-PGJ₂ profoundly affects the proteasome functions in human EC suggests that 15d-PGJ₂ may regulate the progression of inflammatory disorders such as atherosclerosis.

Induction of BCL2-Interacting Killer, BIK, is Mediated for Anti-Cancer Activity of Curcumin in Human Head and Neck Squamous Cell Carcinoma Cells

Naturally occurring diarylheptanoid curcumin (CUR), a principal component of the Asian spice turmeric, has been shown to have anti-cancer effects in many tumor types. However, a detailed mechanism regarding CUR induced tumor cell killing remain to be comprehensively explored. Using two head neck squamous cell carcinoma (HNSCC) cell lines FaDu (hypopharyngeal) and Cal27 (tongue), we demonstrated a novel mechanism by which CUR levies the cytotoxic effect. We found that CUR induced upregulation of pro-apoptotic Bik, down-regulation of survival signaling by AKT and NF-κB prior to the induction of the caspase-cascade reduction of cell proliferation, are primary mechanisms of CUR-induced cell death, thus providing insights into the anti-tumor activity of CUR in HNSCC cells.

Interleukin-6 as a therapy target in oral squamous carcinoma

INTRODUCTION

Interleukin-6 (IL-6) is a multifunctional cytokine which is implicated in the regulation of immune responses and cellular events. It may activate signaling pathways of Janus kinase/signal transducer and activator of transcription (JAK/STAT) factors, mitogen-activated protein kinases, and Akt. IL-6 could exert pleiotropic effects in a variety of cancers.

AREAS COVERED

Oral squamous cell carcinoma epidemiology, pathology, regulation by IL-6, and experimental therapy.

EXPERT OPINION

Oral squamous cell carcinoma development is in part facilitated by chronic epithelial irritations and this tumor is more frequent in smokers or individuals who consume excessive amounts of alcohol. IL-6 levels are elevated in this neoplasm and IL-6 is considered a bad prognostic factor in oral cancer. IL-6 secretion in oral squamous cancer is facilitated by the microenvironment, in particular by stromal derived factor-1. IL-6 function in non-malignant and malignant diseases is controlled by endogenous inhibitors of cytokine signaling. IL-6 action in oral squamous cancer is largely mediated by the JAK/STAT3 pathway and may lead to epithelial to mesenchymal transition, thus contributing to tumor progression. IL-6 also enhances angiogenesis and lymphangiogenesis through regulation of vascular endothelial growth factor. In addition, experimental anti-IL-6/anti-IL-6 receptor-targeted therapies in oral cancer have been proposed.

15-Deoxy-Δ¹²,¹⁴-prostaglandin J₂, an electrophilic lipid mediator of anti-inflammatory and pro-resolving signaling

15-deoxy-Δ(12,14)-prostagandin J(2) (15d-PGJ2) is produced in the inflamed cells and tissues as a consequence of upregulation of cyclooxygenase-2 (COX-2). 15d-PGJ2 is known to be the endogenous ligand of peroxisome proliferator-activated receptor gamma (PPARγ) with multiple physiological properties. Though one of the terminal products of the COX-2-catalyzed reactions, this cyclopentenone prostaglandin exerts potent anti-inflammatory actions, in part, by antagonizing the activities of pro-inflammatory transcription factors, such as NF-κB, STAT3, and AP-1, while stimulating the anti-inflammatory transcription factor Nrf2. These effects are not necessarily dependent on its activation of PPARγ, but often involves direct interaction with the above signaling molecules and their regulators. The locally produced 15d-PGJ2 is also involved in the resolution of inflammatory responses. Thus, 15d-PGJ2, especially formed during the late phase of inflammation, might inhibit cytokine secretion and other events by antigen-presenting cells like dendritic cells or macrophages. 15d-PGJ2 can also affect the priming and effector functions of T lymphocytes and induce their apoptotic cell death. These represent a negative feedback explaining how once-initiated immunologic and inflammatory responses are switched off and terminated. In this context, 15d-PGJ2 and its synthetic derivatives have therapeutic potential for the treatment of inflammatory disorders.

Omega-3 Fatty Acids and PPARgamma in Cancer

Omega-3 (or n-3) polyunsaturated fatty acids (PUFAs) and their metabolites are natural ligands for peroxisome proliferator receptor activator (PPAR)gamma and, due to the effects of PPARgamma on cell proliferation, survival, and differentiation, are potential anticancer agents. Dietary intake of omega-3 PUFAs has been associated with a reduced risk of certain cancers in human populations and in animal models. In vitro studies have shown that omega-3 PUFAs inhibit cell proliferation and induce apoptosis in cancer cells through various pathways but one of which involves PPARgamma activation. The differential activation of PPARgamma and PPARgamma-regulated genes by specific dietary fatty acids may be central to their distinct roles in cancer. This review summarizes studies relating PUFAs to PPARgamma and cancer and offers a new paradigm relating an n-3 PUFA through PPARgamma to the expression of the cell surface proteoglycan, syndecan-1, and to the death of cancer cells.

Sustained Src inhibition results in signal transducer and activator of transcription 3 (STAT3) activation and cancer cell survival via altered Janus-activated kinase-STAT3 binding

Locoregional and distant recurrence remains common and usually fatal for patients with advanced head and neck squamous cell carcinoma (HNSCC). One promising molecular target in HNSCC is the Src family kinases (SFK). SFKs can affect cellular proliferation and survival by activating the signal transducer and activator of transcription (STAT) family of transcription factors, especially STAT3. Surprisingly, sustained SFK inhibition resulted in only transient inhibition of STAT3. We investigated the mechanism underlying STAT3 activation and its biological importance. Specific c-Src knockdown with small interfering RNA (siRNA) resulted in STAT3 activation showing specificity, which was inhibited by Janus-activated kinase (JAK; TYK2 and JAK2) depletion with siRNA. Sustained SFK inhibition also resulted in recovered JAK-STAT3 binding and JAK kinase activity after an initial reduction, although JAK phosphorylation paradoxically decreased. To determine the biological significance of STAT3 activation, we combined specific STAT3 depletion with a pharmacologic SFK inhibitor and observed increased cell cycle arrest and apoptosis. Likewise, the addition of STAT3- or JAK-specific siRNA to c-Src-depleted cells enhanced cytotoxicity relative to cells incubated with c-Src siRNA alone. These results show that reactivation of STAT3 after sustained, specific c-Src inhibition is mediated through altered JAK-STAT3 binding and JAK kinase activity and that this compensatory pathway allows for cancer cell survival and proliferation despite durable c-Src inhibition. To our knowledge, this novel feedback pathway has never been described previously. Given that pharmacologic SFK inhibitors are currently being evaluated in clinical trials, these results have potential clinical implications for cancer therapy.

Abrogation of signal transducer and activator of transcription 3 reactivation after Src kinase inhibition results in synergistic antitumor effects

PURPOSE

The Src family of kinases (SFKs) regulate multiple signal transduction cascades and influence proliferation, motility, survival, and angiogenesis. Dasatinib inhibits SFKs, which leads to cytotoxicity, cell cycle arrest, apoptosis, and decreased invasion of cancer cells. Signal transducer and activator of transcription 3 (STAT3) is a latent transcription factor that regulates survival and proliferation. Dasatinib results in rapid and durable inhibition of c-Src, whereas STAT3 undergoes only transient inactivation. We hypothesized that the reactivation of STAT3 after dasatinib treatment represents the engagement of a compensatory signal for cell survival that blocks the antitumor effects of SFK inhibition.

EXPERIMENTAL DESIGN

The effects of upstream inhibitors on STAT3 activation were assessed with western blotting and a quantitative bioplex phosphoprotein assay. We used the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to determine the cytotoxicity and propidium iodine/annexin V staining with fluorescence-activated cell sorting (FACS) analysis to evaluate cell cycle change and apoptosis. The combination index was calculated by the Chou-Talalay equation. Cytokines were quantitated using a multiplexed, particle-based FACS analysis.

RESULTS

C-Src and several downstream molecules were rapidly and durably inhibited by dasatinib. However, STAT3 was reactivated by 24 h. The addition of JAK inhibitors during dasatinib incubation resulted in sustained inhibition of STAT3, although JAK activation by dasatinib was not shown. Combined SFK and JAK inhibition resulted in synergistic cytotoxicity due to increased apoptosis.

CONCLUSIONS

The reactivation of STAT3 during dasatinib treatment is caused by the engagement of a compensatory pathway that suppresses the antitumor effects of SFK inhibition and allows cancer cell survival. Abrogation of this pathway resulted in synergistic cytotoxicity. Given that STAT3 reactivation occurred in 14 of 15 solid tumor cell lines, dasatinib combined with Janus-activated kinase inhibitors may have widespread application in cancer treatment.

Survivin is a downstream target and effector of sulindac-sensitive oncogenic Stat3 signalling in head and neck cancer

Sulindac exerts its antitumorigenic effects in oral squamous cell carcinoma (SCC) cells by modulating survivin in a Stat3-dependent manner. Immunohistochemistry was used to detect the protein levels of phosphorylated-tyrosine Stat3 (p-tyr Stat3) and survivin in SCC tissues. Western blot, reverse transcriptase polymerase chain reaction, Annexin-V and cell proliferation assays were used to determine p-tyr Stat3 and survivin protein and mRNA expression, and cell viability following treatment with cyclooxygenase (COX) inhibitors, Stat3 siRNA, or the forced expression of Stat3 or survivin. Immunohistochemical analysis revealed an overexpression of p-tyr Stat3 in T1 SCCs. The importance of constitutive Stat3 activation in tumourigenesis was confirmed by siRNA inhibition of Stat3, resulting in cell growth inhibition and apoptosis, via a downregulation of survivin mRNA and protein expression. The forced expression of survivin partially reversed these effects of Stat3 inhibition. Sulindac, but not other COX inhibitors, downregulated Stat3, which correlated to an inhibition of cell proliferation, survival and survivin expression. Transfection of constitutively active Stat3 restored survivin expression and partially rescued SCC cells from sulindac-induced antitumorigenic effects. These data indicate that survivin is a downstream target and effector of oncogenic Stat3 signalling in SCC, which is targeted by sulindac in a COX-2-independent manner.

Molecular cross-talk between the NFkappaB and STAT3 signaling pathways in head and neck squamous cell carcinoma

The development of head and neck squamous cell carcinoma (HNSCC) involves the accumulation of genetic and epigenetic alterations in tumor-suppressor proteins, together with the persistent activation of growth-promoting signaling pathways. The activation of epidermal growth factor receptor (EGFR) is a frequent event in HNSCC. However, EGFR-independent mechanisms also contribute to the activation of key intracellular signaling routes, including signal transducer and activator of transcription-3 (STAT3), nuclear factor kappaB (NFkappaB), and Akt. Indeed, the autocrine activation of the gp130 cytokine receptor in HNSCC cells by tumor-released cytokines, such as IL-6, can result in the EGFR-independent activation of STAT3. In this study, we explored the nature of the molecular mechanism underlying enhanced IL-6 secretion in HNSCC cells. We found that HNSCC cells display an increased activity of the IL-6 promoter, which is dependent on the presence of an intact NFkappaB site. Furthermore, NFkappaB inhibition downregulated IL-6 gene and protein expression, and decreased the release of multiple cytokines. Interestingly, interfering with NFkappaB function also prevented the autocrine/paracrine activation of STAT3 in HNSCC cells. These findings demonstrate a cross-talk between the NFkappaB and the STAT3 signaling systems, and support the emerging notion that HNSCC results from the aberrant activity of a signaling network.

Nrf2-mediated induction of cytoprotective enzymes by 15-deoxy-Delta12,14-prostaglandin J2 is attenuated by alkenal/one oxidoreductase

NADPH-dependent alkenal/one oxidoreductase (Aor) was discovered to be highly inducible in rat liver following treatment with the cancer chemopreventive agent 3H-1, 2-dithiole-3-thione. Aor was further characterized as an Nrf2-regulated antioxidative enzyme that reduces carbon-carbon double bonds in a variety of alpha, beta-unsaturated aldehydes and ketones. 15-Deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) is a reactive membrane lipid metabolite that activates multiple pathways, including Nrf2-mediated induction of cytoprotective enzymes. Physiologically, it is postulated that 15d-PGJ2 alkylates key regulatory proteins via the electrophilic carbon centers found in two alpha, beta-unsaturated ketone moieties. This current study addresses the metabolism of 15d-PGJ2 by rat Aor (rAor) and subsequent deactivation of the Nrf2 signaling pathway by both rat and human AOR. We demonstrate that induction of NADPH-dependent quinone oxidoreductase activity by 15d-PGJ2 is markedly attenuated in mouse embryonic fibroblasts that overexpress rAor. Luciferase reporter assay and quantitative real-time PCR confirmed these findings. Concentrations required for doubling the NADPH-dependent quinone oxidoreductase response are increased from 1.8 microm in wild-type to >10 microm in rat Aor transgenic fibroblasts. 15d-PGJ2 is metabolized by recombinant rAor with a Km of 9.6 microm and k(cat) of 18.5 min(-1). The major product is 12,13-dihydro-15-deoxy-Delta12,14-prostaglandin J2 (dihydro-15d-PGJ2). The reduction of C=C by Aor yielding dihydro-15d-PGJ2 abolishes the inducibility in an antioxidant response element-driven luciferase assay. Collectively, these results demonstrate that 15d-PGJ2 can be catabolized by Aor, thereby attenuating subsequent Nrf2 signaling and possibly inflammatory and apoptotic processes also influenced by 15d-PGJ2.