Chemotherapeutic agents enhance cell migration and epithelial-to-mesenchymal transition through transient up-regulation of tNOX (ENOX2) protein

Advances in Pathogenesis and Treatment of Skin Cancer

This Special Issue is a collection of papers on skin cancers, focusing on their etiopathogenesis and the most innovative and effective therapies [...].

Ecto-NOX Disulfide-Thiol Exchanger 2 (ENOX2/tNOX) Is a Potential Prognostic Marker in Primary Malignant Melanoma and May Serve as a Therapeutic Target

With an increasing incidence of malignant melanoma, new prognostic biomarkers for clinical decision making have become more important. In this study, we evaluated the role of ecto-NOX disulfide-thiol exchanger 2 (ENOX2/tNOX), a cancer- and growth-associated protein, in the prognosis and therapy of primary malignant melanoma. We conducted a tissue microarray analysis of immunohistochemical ENOX2 protein expression and The Cancer Genome Atlas (TCGA) ENOX2 RNA expression analysis, as well as viability assays and Western blots of melanoma cell lines treated with the ENOX2 inhibitor phenoxodiol (PXD) and BRAF inhibitor (BRAFi) vemurafenib. We discovered that high ENOX2 expression is associated with decreased overall (OS), disease-specific (DSS) and metastasis-free survival (MFS) in primary melanoma (PM) and a reduction in electronic tumor-infiltrating lymphocytes (eTILs). A gradual rise in ENOX2 expression was found with an increase in malignant potential from benign nevi (BNs) via PMs to melanoma metastases (MMs), as well as with an increasing tumor thickness and stage. These results highlight the important role of ENOX2 in cancer growth, progression and metastasis. The ENOX2 expression was not limited to malignant cell lines but could also be found in keratinocytes, fibroblasts and melanocytes. The viability of melanoma cell lines could be inhibited by PXD. A reduced induction of phospho-AKT under PXD could prevent the development of acquired BRAFi resistance. In conclusion, ENOX2 may serve as a potential prognostic marker and therapeutic target in malignant melanoma.

Water-soluble 4-(dimethylaminomethyl)heliomycin exerts greater antitumor effects than parental heliomycin by targeting the tNOX-SIRT1 axis and apoptosis in oral cancer cells

The antibiotic heliomycin (resistomycin), which is generated from Streptomyces resistomycificus, has multiple activities, including anticancer effects. Heliomycin was first described in the 1960s, but its clinical applications have been hindered by extremely low solubility. A series of 4-aminomethyl derivatives of heliomycin were synthesized to increase water solubility; studies showed that they had anti-proliferative effects, but the drug targets remained unknown. In this study, we conducted cellular thermal shift assays (CETSA) and molecular docking simulations to identify and validate that heliomycin and its water-soluble derivative, 4-(dimethylaminomethyl)heliomycin (designated compound 4-dmH) engaged and targeted with sirtuin-1 (SIRT1) in p53-functional SAS and p53-mutated HSC-3 oral cancer cells. We further addressed the cellular outcome of SIRT1 inhibition by these compounds and found that, in addition to SIRT1, the water-soluble 4-dmH preferentially targeted a tumor-associated NADH oxidase (tNOX, ENOX2). The direct binding of 4-dmH to tNOX decreased the oxidation of NADH to NAD+ which diminished NAD+-dependent SIRT1 deacetylase activity, ultimately inducing apoptosis and significant cytotoxicity in both cell types, as opposed to the parental heliomycin-induced autophagy. We also observed that tNOX and SIRT1 were both upregulated in tumor tissues of oral cancer patients compared to adjacent normal tissues, suggesting their clinical relevance. Finally, the better therapeutic efficacy of 4-dmH was confirmed in tumor-bearing mice, which showed greater tNOX and SIRT1 downregulation and tumor volume reduction when treated with 4-dmH compared to heliomycin. Taken together, our in vitro and in vivo findings suggest that the multifaceted properties of water-soluble 4-dmH enable it to offer superior antitumor value compared to parental heliomycin, and indicated that it functions through targeting the tNOX-NAD+-SIRT1 axis to induce apoptosis in oral cancer cells.

Capsaicinoids and Their Effects on Cancer: The "Double-Edged Sword" Postulate from the Molecular Scale

Capsaicinoids are a unique chemical species resulting from a particular biosynthesis pathway of hot chilies (Capsicum spp.) that gives rise to 22 analogous compounds, all of which are TRPV1 agonists and, therefore, responsible for the pungency of Capsicum fruits. In addition to their human consumption, numerous ethnopharmacological uses of chili have emerged throughout history. Today, more than 25 years of basic research accredit a multifaceted bioactivity mainly to capsaicin, highlighting its antitumor properties mediated by cytotoxicity and immunological adjuvancy against at least 74 varieties of cancer, while non-cancer cells tend to have greater tolerance. However, despite the progress regarding the understanding of its mechanisms of action, the benefit and safety of capsaicinoids' pharmacological use remain subjects of discussion, since CAP also promotes epithelial-mesenchymal transition, in an ambivalence that has been referred to as "the double-edge sword". Here, we update the comparative discussion of relevant reports about capsaicinoids' bioactivity in a plethora of experimental models of cancer in terms of selectivity, efficacy, and safety. Through an integration of the underlying mechanisms, as well as inherent aspects of cancer biology, we propose mechanistic models regarding the dichotomy of their effects. Finally, we discuss a selection of in vivo evidence concerning capsaicinoids' immunomodulatory properties against cancer.

Redox-Cycling "Mitocans" as Effective New Developments in Anticancer Therapy

Our study proposes a pharmacological strategy to target cancerous mitochondria via redox-cycling "mitocans" such as quinone/ascorbate (Q/A) redox-pairs, which makes cancer cells fragile and sensitive without adverse effects on normal cells and tissues. Eleven Q/A redox-pairs were tested on cultured cells and cancer-bearing mice. The following parameters were analyzed: cell proliferation/viability, mitochondrial superoxide, steady-state ATP, tissue redox-state, tumor-associated NADH oxidase (tNOX) expression, tumor growth, and survival. Q/A redox-pairs containing unprenylated quinones exhibited strong dose-dependent antiproliferative and cytotoxic effects on cancer cells, accompanied by overproduction of mitochondrial superoxide and accelerated ATP depletion. In normal cells, the same redox-pairs did not significantly affect the viability and energy homeostasis, but induced mild mitochondrial oxidative stress, which is well tolerated. Benzoquinone/ascorbate redox-pairs were more effective than naphthoquinone/ascorbate, with coenzyme Q0/ascorbate exhibiting the most pronounced anticancer effects in vitro and in vivo. Targeted anticancer effects of Q/A redox-pairs and their tolerance to normal cells and tissues are attributed to: (i) downregulation of quinone prenylation in cancer, leading to increased mitochondrial production of semiquinone and, consequently, superoxide; (ii) specific and accelerated redox-cycling of unprenylated quinones and ascorbate mainly in the impaired cancerous mitochondria due to their redox imbalance; and (iii) downregulation of tNOX.

Bis(chloroacetamidino)-Derived Heteroarene-Fused Anthraquinones Bind to and Cause Proteasomal Degradation of tNOX, Leading to c-Flip Downregulation and Apoptosis in Oral Cancer Cells

Simple Summary

New-generation anthraquinone derivatives attached with different heterocycles and bearing chloroacetamidines in the side chains have been synthesized to reduce side effects and drug resistance. In this study, we identified the cellular target of the studied compounds through ligand binding assays and in silico simulations. Our results illustrate that the studied compounds bound to and targeted the tumor-associated NADH oxidase (tNOX) in oral cancer cells. tNOX is a growth-related protein and is found to be expressed in cancer cells but not in non-transformed cells, and its knockdown by RNA interference in tumor cells overturns cancer phenotypes, supporting its role in cellular growth. We also identified that tNOX bound to the studied compounds and underwent degradation, which was correlated with apoptosis induction in oral cancer cells.

Abstract

Anthraquinone-based intercalating compounds, namely doxorubicin and mitoxantrone, have been used clinically based on their capacity to bind DNA and induce DNA damage. However, their applications have been limited by side effects and drug resistance. New-generation anthraquinone derivatives fused with different heterocycles have been chemically synthesized and screened for higher anticancer potency. Among the compounds reported in our previous study, 4,11-bis(2-(2-chloroacetamidine)ethylamino)anthra[2,3-b]thiophene-5,10-dione dihydrochloride (designated 2c) was found to be apoptotic, but the direct cellular target responsible for the cytotoxicity remained unknown. Here, we report the synthesis and anticancer properties of two other derivatives, 4,11-bis(2-(2-chloroacetamidine)ethylamino)naphtho[2,3-f]indole-5,10-dione dihydrochloride (2a) and 4,11-bis(2-(2-chloroacetamidine)ethylamino)-2-methylanthra[2,3-b]furan-5,10-dione dihydrochloride (2b). We sought to identify and validate the protein target(s) of these derivatives in oral cancer cells, using molecular docking simulations and cellular thermal shift assays (CETSA). Our CETSA results illustrate that these derivatives targeted the tumor-associated NADH oxidase (tNOX, ENOX2), and their direct binding downregulated tNOX in p53-functional SAS and p53-mutated HSC-3 cells. Interestingly, the compounds targeted and downregulated tNOX to reduce SIRT1 deacetylase activity and increase Ku70 acetylation, which triggers c-Flip ubiquitination and induces apoptosis in oral cancer cells. Together, our data highlight the potential value of these heteroarene-fused anthraquinones in managing cancer by targeting tNOX and augmenting apoptosis.

Targeting Glioblastoma via Selective Alteration of Mitochondrial Redox State

Simple Summary

Glioblastoma is characterized by a pronounced redox imbalance due to elevated glycolytic and mitochondrial oxidative metabolism. New therapeutic strategies have been developed to modulate glioblastoma redox signaling to effectively suppress growth and prolong survival. However, drug selectivity and therapeutic relapse prove to be the major challenges. We describe a pharmacological strategy for the selective targeting and treatment of glioblastoma using the redox active combination drug menadione/ascorbate, which is characterized by tolerance to normal cells and tissues. Menadione/ascorbate treatment of glioblastoma mice suppressed tumor growth and significantly increased survival without adverse side effects. This is accompanied by increased oxidative stress, decreased reducing capacity and decreased cellular density in the tumor alone, as well as increased brain perfusion and decreased regulation of several oncoproteins and oncometabolites, which implies modulation of the immune response and reduced drug resistance. We believe that this therapeutic strategy is feasible and promising and deserves the attention of clinicians.

Abstract

Glioblastoma is one of the most aggressive brain tumors, characterized by a pronounced redox imbalance, expressed in a high oxidative capacity of cancer cells due to their elevated glycolytic and mitochondrial oxidative metabolism. The assessment and modulation of the redox state of glioblastoma are crucial factors that can provide highly specific targeting and treatment. Our study describes a pharmacological strategy for targeting glioblastoma using a redox-active combination drug. The experiments were conducted in vivo on glioblastoma mice (intracranial model) and in vitro on cell lines (cancer and normal) treated with the redox cycling pair menadione/ascorbate (M/A). The following parameters were analyzed in vivo using MRI or ex vivo on tissue and blood specimens: tumor growth, survival, cerebral perfusion, cellular density, tissue redox state, expression of tumor-associated NADH oxidase (tNOX) and transforming growth factor-beta 1 (TGF-β1). Dose-dependent effects of M/A on cell viability, mitochondrial functionality, and redox homeostasis were evaluated in vitro. M/A treatment suppressed tumor growth and significantly increased survival without adverse side effects. This was accompanied by increased oxidative stress, decreased reducing capacity, and decreased cellular density in the tumor only, as well as increased cerebral perfusion and down-regulation of tNOX and TGF-β1. M/A induced selective cytotoxicity and overproduction of mitochondrial superoxide in isolated glioblastoma cells, but not in normal microglial cells. This was accompanied by a significant decrease in the over-reduced state of cancer cells and impairment of their “pro-oncogenic” functionality, assessed by dose-dependent decreases in: NADH, NAD⁺, succinate, glutathione, cellular reducing capacity, mitochondrial potential, steady-state ATP, and tNOX expression. The safety of M/A on normal cells was compromised by treatment with cerivastatin, a non-specific prenyltransferase inhibitor. In conclusion, M/A differentiates glioblastoma cells and tissues from normal cells and tissues by redox targeting, causing severe oxidative stress only in the tumor. The mechanism is complex and most likely involves prenylation of menadione in normal cells, but not in cancer cells, modulation of the immune response, a decrease in drug resistance, and a potential role in sensitizing glioblastoma to conventional chemotherapy.

Inhibition of the Notch signaling pathway attenuates progression of cell motility, metastasis, and epithelial-to-mesenchymal transition-like phenomena induced by low concentrations of cisplatin in osteosarcoma

Although advances in osteosarcoma treatment have been made in recent decades, the survival rate for patients suffering from metastatic disease, especially lung metastasis, remains disappointing. Previous studies have confirmed that epithelial-to-mesenchymal transition (EMT) is associated with tumor metastasis, and several studies have suggested that osteosarcoma cells also exhibit EMT-like characteristics. In addition, Notch signaling is known to be related to the development and progression of human malignancies, including osteosarcoma. However, whether chemotherapy affects the EMT-like events and whether these events are medicated by Notch signaling remain to be elucidated. To address these issues, in the current work, osteosarcoma 143B cells were exposed to sublethal concentrations of the first-line chemotherapeutic agent cisplatin (DDP), which promoted cell migration, in vitro invasion, and in vivo lung metastasis. Furthermore, low concentrations of DDP upregulated mesenchymal phenotype-related genes and proteins and promoted EMT-like properties in osteosarcoma cells. In addition, low concentrations of DDP could activate the Notch receptor and its target genes. Finally, combined treatment of DDP with the Notch signaling pathway inhibitor DAPT, which can effectively downregulate mesenchymal phenotype-related genes and proteins, inhibited cell migration and invasion in vitro, and it decreased pulmonary metastatic nodules in vivo. The results of the current study supported the idea that low concentrations of DDP could induce EMT-like characteristics in osteosarcoma cells and could promote cell mobility in vitro, as well as pulmonary metastasis in vivo. Importantly, however, these biological processes are mediated by the Notch signaling pathway. Blocking the Notch signaling pathway can effectively attenuate the osteosarcoma EMT-like phenotype and its associated migration, invasion, and metastasis.

Drug-resistant cancer cell-derived exosomal EphA2 promotes breast cancer metastasis via the EphA2-Ephrin A1 reverse signaling

Tumor metastasis induced by drug resistance is a major challenge in successful cancer treatment. Nevertheless, the mechanisms underlying the pro-invasive and metastatic ability of drug resistance remain elusive. Exosome-mediated intercellular communications between cancer cells and stromal cells in tumor microenvironment are required for cancer initiation and progression. Recent reports have shown that communications between cancer cells also promote tumor aggression. However, little attention has been regarded on this aspect. Herein, we demonstrated that drug-resistant cell-derived exosomes promoted the invasion of sensitive breast cancer cells. Quantitative proteomic analysis showed that EphA2 was rich in exosomes from drug-resistant cells. Exosomal EphA2 conferred the invasive/metastatic phenotype transfer from drug-resistant cells to sensitive cells. Moreover, exosomal EphA2 activated ERK1/2 signaling through the ligand Ephrin A1-dependent reverse pathway rather than the forward pathway, thereby promoting breast cancer progression. Our findings indicate the key functional role of exosomal EphA2 in the transmission of aggressive phenotype between cancer cells that do not rely on direct cell-cell contact. Our study also suggests that the increase of EphA2 in drug-resistant cell-derived exosomes may be an important mechanism of chemotherapy/drug resistance-induced breast cancer progression.

PPTS Inhibits the TGF-β1-Induced Epithelial-Mesenchymal Transition in Human Colorectal Cancer SW480 Cells

The current study investigates the inhibitory effects of Pulsatilla pentacyclic triterpenoid saponins extract (PPTS) on epithelial-mesenchymal transition (EMT) triggered by the transforming growth factor-β1 (TGF-β1) in human colorectal cancer SW480 cell line, further illustrates the possible mechanism of PPTS inhibition of growth and invasion from the perspective of EMT, and provides new theoretical support for the treatment of tumor by Chinese medicine. The SW480 cells were treated in groups: blank control, TGF-β1 (10 ng/mL), and varying concentrations of PPTS cotreated with TGF-β1-induced (10 ng/mL) groups. CCK8 was used to detect cell viability; transwell was applied to detect invasion ability, cell migration ability was also determined, ELISA and RT-qPCR were utilized for the determination of CYP3A, CYP2C9, CYP2C19, N-cadherin, and MMP-9 expression. Flow cytometry detection was applied to detect cell cycle and apoptosis. The results obtained have shown that PPTS can significantly inhibit the invasion and migration of tumors in SW480 cells and can also block the S phase in the cell cycle but may produce cytotoxicity in higher doses. The present research work provides substantial evidence that PPTS has a significant inhibitory effect on TGF-β1-induced EMT in SW480 cells and it also promotes apoptosis.

Rack1 mediates tyrosine phosphorylation of Anxa2 by Src and promotes invasion and metastasis in drug-resistant breast cancer cells

Background

Acquirement of resistance is always associated with a highly aggressive phenotype of tumor cells. Recent studies have revealed that Annexin A2 (Anxa2) is a key protein that links drug resistance and cancer metastasis. A high level of Anxa2 in cancer tissues is correlated to a highly aggressive phenotype. Increased Anxa2 expression appears to be specific in many drug-resistant cancer cells. The functional activity of Anxa2 is regulated by tyrosine phosphorylation at the Tyr23 site. Nevertheless, the accurate molecular mechanisms underlying the regulation of Anxa2 tyrosine phosphorylation and whether phosphorylation is necessary for the enhanced invasive phenotype of drug-resistant cells remain unknown.

Methods

Small interfering RNAs, small molecule inhibitors, overexpression, loss of function or gain of function, rescue experiments, Western blot, wound healing assays, transwell assays, and in vivo metastasis mice models were used to investigate the functional effects of Rack1 and Src on the tyrosine phosphorylation of Anxa2 and the invasion and metastatic potential of drug-resistant breast cancer cells. The interaction among Rack1, Src, and Anxa2 in drug-resistant cells was verified by co-immunoprecipitation assay.

Results

We demonstrated that Anxa2 Tyr23 phosphorylation is necessary for multidrug-resistant breast cancer invasion and metastasis. Rack1 is required for the invasive and metastatic potential of drug-resistant breast cancer cells through modulating Anxa2 phosphorylation. We provided evidence that Rack1 acts as a signal hub and mediates the interaction between Src and Anxa2, thereby facilitating Anxa2 phosphorylation by Src kinase.

Conclusions

Our findings suggest a convergence point role of Rack1/Src/Anxa2 complex in the crosstalk between drug resistance and cancer aggressiveness. The interaction between Anxa2 and Rack1/Src is responsible for the association between drug resistance and invasive/metastatic potential in breast cancer cells. Thus, our findings provide novel insights on the mechanism underlying the functional linkage between drug resistance and cancer aggressiveness.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1147-7) contains supplementary material, which is available to authorized users.

Engagement with tNOX (ENOX2) to Inhibit SIRT1 and Activate p53-Dependent and -Independent Apoptotic Pathways by Novel 4,11-Diaminoanthra[2,3-b]furan-5,10-diones in Hepatocellular Carcinoma Cells

Hepatocellular carcinoma (HCC) is the most frequent primary malignancy of the liver and is among the top three causes of cancer-associated death worldwide. However, the clinical use of chemotherapy for HCC has been limited by various challenges, emphasizing the urgent need for novel agents with improved anticancer properties. We recently synthesized and characterized a series of 4,11-diaminoanthra[2,3-b]furan-5,10-dione derivatives that exhibit potent apoptotic activity against an array of cancer cell lines, including variants with multidrug resistance. Their effect on liver cancer cells, however, was unknown. Here, we investigated three selected 4,11-diaminoanthra[2,3-b]furan-5,10-dione derivatives (compounds 1–3) for their cytotoxicity and the underlying molecular mechanisms in wild-type or p53-deficient HCC cells. Cytotoxicity was determined by WST-1 assays and cell impedance measurements and apoptosis was analyzed by flow cytometry. The interaction between compounds and tumor-associated NADH oxidase (tNOX, ENOX2) was studied by cellular thermal shift assay (CETSA). We found that compound 1 and 2 induced significant cytotoxicity in both HepG2 and Hep3B lines. CETSA revealed that compounds 1 and 2 directly engaged with tNOX, leading to a decrease in the cellular NAD⁺/NADH ratio. This decreased the NAD⁺-dependent activity of Sirtuin 1 (SIRT1) deacetylase. In p53-wild-type HepG2 cells, p53 acetylation/activation was enhanced, possibly due to the reduction in SIRT1 activity, and apoptosis was observed. In p53-deficient Hep3B cells, the reduction in SIRT1 activity increased the acetylation of c-Myc, thereby reactivating the TRAIL pathway and, ultimately leading to apoptosis. These compounds thus trigger apoptosis in both cell types, but via different pathways. Taken together, our data show that derivatives 1 and 2 of 4,11-diaminoanthra[2,3-b]furan-5,10-diones engage with tNOX and inhibit its oxidase activity. This results in cytotoxicity via apoptosis through tNOX-SIRT1 axis to enhance the acetylation of p53 or c-Myc in HCC cells, depending on their p53 status.

Effects of saponins of patrinia villosa against invasion and metastasis in colorectal cancer cell through NF-κB signaling pathway and EMT

BACKGROUND

Research has indicated that Herba Patriniae can suppress the growth of Several kinds of tumor cells in vitro and in vivo, thus displaying favorable antitumor activity. However, research regarding the effect of saponins of Patrinia villosa against CRC cell has not been reported. In the current study, We have revealed that the effects of saponins of patrinia villosa on colorectal cancer (CRC) cell invasion and epithelial-mesenchymal transition (EMT) as well as its underlying mechanism.

METHODS

The CRC EMT model was induced through repeated TGF-β1 stimulations on human CRC cell line SW480. Effects of saponins of patrinia villosa at various concentrations on CRC SW480 cell and EMT model cell proliferation were detected using MTT method, so as to select the optimal action concentration. Meanwhile, effects on SW480 cell and EMT model cell invasion were determined through Scratch assay and Transwell assay. Moreover, changes in expression of EMT-related proteins E-cadherin, N-cadherin and NF-ΚBp65 in each group were detected through Western blotting.

RESULTS

Saponins of patrinia villosa at various concentrations could markedly inhibit the proliferation rate of CRC cell in an obvious concentration-dependent manner. Meanwhile, saponins of patrinia villosa at various concentrations could also remarkably suppress migration of cell developing EMT. In addition, the protein expression of E-cadherin and N-cadherin was down-regulated with the increase in saponins of patrinia villosa concentration, while that of NF-KBp65 was notably down-regulated.

CONCLUSION

Saponins of patrinia villosa can act against tumor invasion and metastasis through inhibiting EMT in human CRC cell line, which may be achieved through down-regulating the NF-κB signaling pathway.

Tumor-associated NADH oxidase (tNOX)-NAD+-sirtuin 1 axis contributes to oxaliplatin-induced apoptosis of gastric cancer cells

Oxaliplatin belongs to the platinum-based drug family and has shown promise in cancer treatment. The major mechanism of action of platinum compounds is to form platinum–DNA adducts, leading to DNA damage and apoptosis. Accumulating evidence suggests that they might also target non-DNA molecules for their apoptotic activity. We explored the effects of oxaliplatin on a tumor-associated NADH oxidase (tNOX) in gastric cancer lines. In AGS cells, we found that the oxaliplatin-inhibited tNOX effectively attenuated the NAD⁺/NADH ratio and reduced the deacetylase activity of an NAD⁺-dependent sirtuin 1, thereby enhancing p53 acetylation and apoptosis. Similar results were also observed in tNOX-knockdown AGS cells. In the more aggressive MKN45 and TMK-1 lines, oxaliplatin did not inhibit tNOX, and induced only minimal apoptosis and cytotoxicity. However, the downregulation of either sirtuin 1 or tNOX sensitized TMK-1 cells to oxaliplatin-induced apoptosis. Moreover, tNOX-depletion in these resistant cells enhanced spontaneous apoptosis, reduced cyclin D expression and prolonged the cell cycle, resulting in diminished cancer cell growth. Together, our results demonstrate that oxaliplatin targets tNOX and SIRT1, and that the tNOX-NAD⁺-sirtuin 1 axis is essential for oxaliplatin-induced apoptosis.

Expression of Clonorchis sinensis GIIIsPLA2 protein in baculovirus-infected insect cells and its overexpression facilitating epithelial-mesenchymal transition in Huh7 cells via AKT pathway

Although prior studies confirmed that group III secretory phospholipase A₂ of Clonorchis sinensis (CsGIIIsPLA₂) had stimulating effect on liver fibrosis by binding to LX-2 cells, large-scale expression of recombinant protein and its function in the progression of hepatoma are worth exploring. Because of high productivity and low lipopolysaccharides (LPS) in the Sf9-baculovirus expression system, we firstly used this system to express the coding region of CsGIIIsPLA₂. The molecular weight of recombinant CsGIIIsPLA₂ protein was about 34 kDa. Further investigation showed that most of the recombinant protein presented intracellular expression in Sf9 insect cell nucleus and could be detected only into cell debris, which made the protein purification and further functional study difficult. Therefore, to study the role of CsGIIIsPLA₂ in hepatocellular carcinoma (HCC) progression, CsGIIIsPLA₂ overexpression Huh7 cell model was applied. Cell proliferation, migration, and the expression level of epithelial-mesenchymal transition (EMT)-related molecules (E-cadherin, N-cadherin, α-catenin, Vimentin, p300, Snail, and Slug) along with possible mechanism were measured. The results indicated that CsGIIIsPLA₂ overexpression not only inhibited cell proliferation and promoted migration and EMT but also enhanced the phosphorylation of AKT in HCC cells. In conclusion, this study supported that CsGIIIsPLA₂ overexpression suppressed cell proliferation and induced EMT through the AKT pathway.

Capsaicin Inhibits Multiple Bladder Cancer Cell Phenotypes by Inhibiting Tumor-Associated NADH Oxidase (tNOX) and Sirtuin1 (SIRT1)

Bladder cancer is one of the most frequent cancers among males, and its poor survival rate reflects problems with aggressiveness and chemo-resistance. Recent interest has focused on the use of chemopreventatives (nontoxic natural agents that may suppress cancer progression) to induce targeted apoptosis for cancer therapy. Capsaicin, which has anti-cancer properties, is one such agent. It is known to preferentially inhibit a tumor-associated NADH oxidase (tNOX) that is preferentially expressed in cancer/transformed cells. Here, we set out to elucidate the correlation between tNOX expression and the inhibitory effects of capsaicin in human bladder cancer cells. We showed that capsaicin downregulates tNOX expression and decreases bladder cancer cell growth by enhancing apoptosis. Moreover, capsaicin was found to reduce the expression levels of several proteins involved in cell cycle progression, in association with increases in the cell doubling time and enhanced cell cycle arrest. Capsaicin was also shown to inhibit the activation of ERK, thereby reducing the phosphorylation of paxillin and FAK, which leads to decreased cell migration. Finally, our results indicate that RNA interference-mediated tNOX depletion enhances spontaneous apoptosis, prolongs cell cycle progression, and reduces cell migration and the epithelial-mesenchymal transition. We also observed a downregulation of sirtuin 1 (SIRT1) in these tNOX-knockdown cells, a deacetylase that is important in multiple cellular functions. Taken together, our results indicate that capsaicin inhibits the growth of bladder cancer cells by inhibiting tNOX and SIRT1 and thereby reducing proliferation, attenuating migration, and prolonging cell cycle progression.

Capsaicin Inhibited Aggressive Phenotypes through Downregulation of Tumor-Associated NADH Oxidase (tNOX) by POU Domain Transcription Factor POU3F2

Capsaicin has been reported to preferentially inhibit the activity of tumor-associated NADH oxidase (tNOX), which belongs to a family of growth-related plasma membrane hydroquinone oxidases in cancer/transformed cells. The inhibitory effect of capsaicin on tNOX is associated with cell growth attenuation and apoptosis. However, no previous study has examined the transcriptional regulation of tNOX protein expression. Bioinformatic analysis has indicated that the tNOX promoter sequence harbors a binding motif for POU3F2, which is thought to play important roles in neuronal differentiation, melanocytes growth/differentiation and tumorigenesis. In this study, we found that capsaicin-mediated tNOX downregulation and cell migration inhibition were through POU3F2. The protein expression levels of POU3F2 and tNOX are positively correlated, and that overexpression of POU3F2 (and the corresponding upregulation of tNOX) enhanced the proliferation, migration and invasion in AGS (human gastric carcinoma) cells. In contrast, knockdown of POU3F2 downregulates tNOX, and the cancer phenotypes are affected. These findings not only shed light on the molecular mechanism of the anticancer properties of capsaicin, but also the transcription regulation of tNOX expression that may potentially explain how POU3F2 is associated with tumorigenesis.

Update on a tumor-associated NADH oxidase in gastric cancer cell growth

Gastric cancer is one of the most common human malignancies, and its prevalence has been shown to be well-correlated with cancer-related deaths worldwide. Regrettably, the poor prognosis of this disease is mainly due to its late diagnosis at advanced stages after the cancer has already metastasized. Recent research has emphasized the identification of cancer biomarkers in the hope of diagnosing cancer early and designing targeted therapies to reverse cancer progression. One member of a family of growth-related nicotinamide adenine dinucleotide (NADH or hydroquinone) oxidases is tumor-associated NADH oxidase (tNOX; ENOX2). Unlike its counterpart CNOX (ENOX1), identified in normal rat liver plasma membranes and shown to be stimulated by growth factors and hormones, tNOX activity purified from rat hepatoma cells is constitutively active. Its activity is detectable in the sera of cancer patients but not in those of healthy volunteers, suggesting its clinical relevance. Interestingly, tNOX expression was shown to be present in an array of cancer cell lines. More importantly, inhibition of tNOX was well correlated with reduced cancer cell growth and induction of apoptosis. RNA interference targeting tNOX expression in cancer cells effectively restored non-cancerous phenotypes, further supporting the vital role of tNOX in cancer cells. Here, we review the regulatory role of tNOX in gastric cancer cell growth.

Synthesis and Characterization of 4,11-Diaminoanthra[2,3-b]furan-5,10-diones: Tumor Cell Apoptosis through tNOX-Modulated NAD(+)/NADH Ratio and SIRT1

A series of new 4,11-diaminoanthra[2,3-b]furan-5,10-dione derivatives with different side chains were synthesized. Selected 2-unsubstituted derivatives 11-14 showed high antiproliferative potency on a panel of mammalian tumor cell lines including multidrug resistance variants. Compounds 11-14 utilized multiple mechanisms of cytotoxicity including inhibition of Top1/Top2-mediated DNA relaxation, reduced NAD(+)/NADH ratio through tNOX inhibition, suppression of a NAD(+)-dependent sirtuin 1 (SIRT1) deacetylase activity, and activation of caspase-mediated apoptosis. Here, for the first time, we report that tumor-associated NADH oxidase (tNOX) and SIRT1 are important cellular targets of antitumor anthracene-9,10-diones.

NADH-linked metabolic plasticity of MCF-7 breast cancer cells surviving in a nutrient-deprived microenvironment

Characteristic of the tumor microenvironment are fluctuating gradients of reduced nutrient levels and released lactate. A fundamental issue is how tumor cells modulate their metabolic activity when both glucose and glutamine levels become limiting in the presence of high exogenous lactate. For functional analyses, the activities of pyruvate kinase, lactate dehydrogenase (LDH) and plasma membrane NADH oxidase (NOX) as well as cell growth were measured in breast cancer MCF-7 cells cultured in medium containing various concentrations of these metabolites. After 3 days at glucose concentrations below 2.5 mM, cell number was higher with 0.1 mM than with 1.0 mM glutamine, indicating that the glucose/glutamine balance is important for growth. On the other hand, NOX activity increased with increasing glucose >2.5 mM, but only with low glutamine (0.1 mM). Pyruvate kinase activity also increased, with LDH activity remaining 2-3-fold lower. Here NOX could have a complementary role in reoxidizing NADH for glycolysis. Exogenous lactate supported cell survival at limiting concentrations of glucose and glutamine while increasing NOX and pyruvate kinase activities as well as NADH levels. It is proposed that lactate supports cell survival by fuelling gluconeogenesis and/or the TCA cycle in mitochondria, from where NADH could be shuttled to the cytosol and reoxidized by NOX. Cell survival and the metabolic phenotype are thus interrelated to the dynamics of NADH and plasma membrane NOX activity, which are regulated by the balance of glucose/glutamine levels, in conjunction with lactate in a precarious tumor microenvironment.

Elevated STAT3 Signaling-Mediated Upregulation of MMP-2/9 Confers Enhanced Invasion Ability in Multidrug-Resistant Breast Cancer Cells

The development of multidrug resistance greatly impedes effective cancer therapy. Recent advances in cancer research have demonstrated that acquisition of multidrug resistance by cancer cells is usually accompanied by enhanced cell invasiveness. Several lines of evidence indicated that cross activation of other signaling pathways during development of drug resistance may increase invasive potential of multidrug-resistant (MDR) cancer cells. However, the accurate mechanism of this process is largely undefined. In this study, to better understand the associated molecular pathways responsible for cancer progression induced by drug resistance, a MDR human breast cancer cell line SK-BR-3/EPR with P-glycoprotein overexpression was established using stepwise long-term exposure to increasing concentration of epirubicin. The SK-BR-3/EPR cell line exhibited decreased cell proliferative activity, but enhanced cell invasive capacity. We showed that the expression of metastasis-related matrix metalloproteinase (MMP)-2/9 was elevated in SK-BR-3/EPR cells. Moreover, SK-BR-3/EPR cells showed elevated activation of STAT3. Activation of STAT3 signaling is responsible for enhanced invasiveness of SK-BR-3/EPR cells through upregulation of MMP-2/9. STAT3 is a well-known oncogene and is frequently implicated in tumorigenesis and chemotherapeutic resistance. Our findings augment insight into the mechanism underlying the functional association between MDR and cancer invasiveness.

Epigenetic factor EPC1 is a master regulator of DNA damage response by interacting with E2F1 to silence death and activate metastasis-related gene signatures

Transcription factor E2F1 is a key regulator of cell proliferation and apoptosis. Recently, it has been shown that aberrant E2F1 expression often detectable in advanced cancers contributes essentially to cancer cell propagation and characterizes the aggressive potential of a tumor. Conceptually, this requires a subset of malignant cells capable of evading apoptotic death through anticancer drugs. The molecular mechanism by which the pro-apoptotic activity of E2F1 is antagonized is widely unclear. Here we report a novel function for EPC1 (enhancer of polycomb homolog 1) in DNA damage protection. Depletion of EPC1 potentiates E2F1-mediated apoptosis in response to genotoxic treatment and abolishes tumor cell motility. We found that E2F1 directly binds to the EPC1 promoter and EPC1 vice versa physically interacts with bifunctional E2F1 to modulate its transcriptional activity in a target gene-specific manner. Remarkably, nuclear-colocalized EPC1 activates E2F1 to upregulate the expression of anti-apoptotic survival genes such as BCL-2 or Survivin/BIRC5 and inhibits death-inducing targets. The uncovered cooperativity between EPC1 and E2F1 triggers a metastasis-related gene signature in advanced cancers that predicts poor patient survival. These findings unveil a novel oncogenic function of EPC1 for inducing the switch into tumor progression-relevant gene expression that may help to set novel therapies.

Sirtuin 1 (SIRT1) Deacetylase Activity and NAD⁺/NADH Ratio Are Imperative for Capsaicin-Mediated Programmed Cell Death

Capsaicin is considered a chemopreventive agent by virtue of its selective antigrowth activity, commonly associated with apoptosis, against cancer cells. However, noncancerous cells possess relatively higher tolerance to capsaicin, although the underlying mechanism for this difference remains unclear. Hence, this study aimed to elucidate the differential effects of capsaicin on cell lines from lung tissues by addressing the signal pathway leading to two types of cell death. In MRC-5 human fetal lung cells, capsaicin augmented silent mating type information regulation 1 (SIRT1) deacetylase activity and the intracellular NAD(+)/NADH ratio, decreasing acetylation of p53 and inducing autophagy. In contrast, capsaicin decreased the intracellular NAD(+)/NADH ratio, possibly through inhibition of tumor-associated NADH oxidase (tNOX), and diminished SIRT1 expression leading to enhanced p53 acetylation and apoptosis. Moreover, SIRT1 depletion by RNA interference attenuated capsaicin-induced apoptosis in A549 cancer cells and autophagy in MRC-5 cells, suggesting a vital role for SIRT1 in capsaicin-mediated cell death. Collectively, these data not only explain the differential cytotoxicity of capsaicin but shed light on the distinct cellular responses to capsaicin in cancerous and noncancerous cell lines.

A real time chemotaxis assay unveils unique migratory profiles amongst different primary murine macrophages

Chemotaxis assays are an invaluable tool for studying the biological activity of inflammatory mediators such as CC chemokines, which have been implicated in a wide range of chronic inflammatory diseases. Conventional chemotaxis systems such as the modified Boyden chamber are limited in terms of the data captured given that the assays are analysed at a single time-point. We report the optimisation and validation of a label-free, real-time cell migration assay based on electrical cell impedance to measure chemotaxis of different primary murine macrophage populations in response to a range of CC chemokines and other chemoattractant signalling molecules. We clearly demonstrate key differences in the migratory behavior of different murine macrophage populations and show that this dynamic system measures true macrophage chemotaxis rather than chemokinesis or fugetaxis. We highlight an absolute requirement for Gαi signaling and actin cytoskeletal rearrangement as demonstrated by Pertussis toxin and cytochalasin D inhibition. We also studied the chemotaxis of CD14(+) human monocytes and demonstrate distinct chemotactic profiles amongst different monocyte donors to CCL2. This real-time chemotaxis assay will allow a detailed analysis of factors that regulate macrophage responses to chemoattractant cytokines and inflammatory mediators.