Role of Capsaicin in Oxidative Stress and Cancer

Cancer chemoprevention is employed to block or reverse the progressionof malignancies. To date, several thousand agents have been found to possesschemopreventive activity. One such compound is capsaicin, a component of chilipeppers that exhibits anti-growth activity against various cancer cell lines. Capsaicinexerts its cytotoxic action by activating an array of signaling mechanisms, includinggeneration of reactive oxygen species (ROS) as messengers to initiate apoptosis, atype I programmed cell death. However, numerous in vitro and in vivo studies havesuggested that capsaicin also possesses tumor-promoting activity; possibly in part,refl ecting activation of autophagy, an alternative (type II) programmed deathprocess. This article reviews the recent literature on the paradoxical effects ofcapsaicin on cancer growth and the diverse capsaicin-induced signaling pathwaysthat lead to cell death or tumorigenesis . Some of the most common cellular targetsof capsaicin are also discussed

Characterization, isolation and expression cloning of a tumor-associated protein ( tNOX) that exhibits NADH:protein disulfide reductase activity with capsaicin -inhibition

The purpose of this dissertation was to characterize, isolate and expression clone a tumor-associated protein (tNOX) that exhibits protein:disulfide reductase activity at the expense of NADH. tNOX activity in cancer cells is distinct from NOX activity in non-transformed cells in several manners. First of all, tNOX activity is no longer under regulation and is constitutively active. Second, tNOX activity in cancer cells is responsive to thiol reagents and is inhibited by antitumor drugs including sulfonylurea and capsaicin. Capsaicin preferentially inhibits both the tNOX activity in plasma membranes and the growth of transformed cells. This cancer-specific capsaicin inhibition in tNOX activity served as a criteria for isolation of tNOX protein from pooled sera of cancer patients. A 33.5 kD protein with capsaicin-inhibited tNOX activity was isolated and used for generation of a monoclonal antibody. Furthermore, a gene was cloned by screening a HeLa cDNA library using the monoclonal antibody. The open reading frame of the derived amino acid sequence encoded a protein with several functional motifs which suggested a possible candidate of tNOX including NADH and quinone binding sites. A possible protein disulfide isomerase motif also was found in the deduced amino acid sequence that might be involved in thiol-disulfide interchange activity of tNOX. The cloned gene has been reported by another group previously, two mistakes result in a shift in the open reading frame and the original report is not a full-length of cDNA. The findings in this dissertation suggest that tNOX is a unique protein and appears to better cancer-specific. The cDNA obtained in this study may be used as a potential marker for detection of cancer in patients by Northern blot analysis or PCR. The discovery of tNOX has opened a new era for cancer research and the exploration of tNOX may lead us to understand tumorgenesis at the molecular level. Ultimately, the studies of tNOX may result in improved preventative measures and treatments for cancer

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

Role of ribophorin II in the response to anticancer drugs in gastric cancer cell lines

The identification of prognostic markers and establishing their value as therapeutic targets improves therapeutic efficacy against human cancers. Ribophorin II (RPN2) has been demonstrated to be a prognostic marker of human cancer, including breast and pancreatic cancers. The present study aimed to evaluate RPN2 expression in gastric cancer and to examine the possible correlation between RPN2 expression and the response of cells to clinical anticancer drugs, which has received little research attention at present. The gastric cancer AGS, TMC-1, SNU-1, TMK-1, SCM-1, MKN-45 and KATO III cell lines were used as a model to elucidate the role of RPN2 in the response of cells to six common chemotherapeutic agents, comprising oxaliplatin, irinotecan, doxorubicin, docetaxel, cisplatin and 5-fluorouricil. The functional role of RPN2 was assessed by silencing RPN2 using small interfering RNA (siRNA), and the cytotoxicity was determined by an MTS assay and analysis of apoptosis. Molecular events were evaluated by western blotting. All the anticancer drugs were found to exert a concentration-dependent decrease on the cell survival rate of each of the cell lines tested, although the RPN2 levels in the various cell lines were not directly correlated with responsiveness to clinical anticancer drugs, based on the calculated IC50 values. siRNA-mediated RPN2 downregulation enhanced cisplatin-induced apoptosis in AGS cells, but did not markedly decrease the cell survival rates of these cells in response to the tested drugs. Furthermore, RPN2 silencing in MKN-45 cells resulted in no additional increase in the cisplatin-induced apoptosis and survival rates. It was also found that RPN2 depletion increased anticancer drug-mediated cytotoxicity in gastric cancer cell lines. However, the predictive value of RPN2 expression in cancer therapy is questionable in gastric cancer models

Capsaicin attenuates cell migration via SIRT1 targeting and inhibition to enhance cortactin and beta-catenin acetylation in bladder cancer cells

We have studied the chemopreventive property of capsaicin, a major active component in chili pepper, and found that it exhibited apoptotic activity against various lines of cancer cells. Interestingly, accumulating data has revealed that, in addition to cytotoxicity, capsaicin also plays regulatory role on cell migration and invasion. However, its effect on cell migration is paradoxical and not completely understood. Here, we set out to elucidate the molecular events underlying capsaicin-inhibited cell migration in bladder cancer cells. Our results show that the capsaicin-reduced cell migration was associated with down-regulation of sirtuin 1 (SIRT1) deacetylase, possibly through proteasome-mediated protein degradation. More importantly, we employed a cellular thermal shift assay (CETSA) to demonstrate that there was a direct binding between capsaicin and SIRT1. The engagement with capsaicin and protein degradation diminished the deacetylase of SIRT1, which in turn, enhanced acetylation of cortactin and β-catenin to decrease MMP-2 and MMP-9 activation, resulting in cell migration impairment in bladder cancer cells

Capsaicin Targets tNOX (ENOX2) to Inhibit G1 Cyclin/CDK Complex, as Assessed by the Cellular Thermal Shift Assay (CETSA)

Capsaicin (8-methyl-N-vanillyl-6-noneamide), which is an active component in red chili peppers, is used as a chemopreventive agent that shows favorable cytotoxicity against cancer cells. Accumulating evidence indicates that capsaicin preferentially inhibits a tumor-associated NADH oxidase (tNOX, ENOX2) that is ubiquitously expressed in cancer but not in non-transformed cells. This attenuates cancer cell growth by inducing apoptosis. The capsaicin-mediated inhibition of tNOX was recently shown to prolong the cell cycle. However, the molecular events underlying this regulation have not yet been investigated. In the present study, we used a cellular thermal shift assay (CETSA) to detect "target engagement" of capsaicin and its consequent impact on cell cycle progression. Our results indicated that capsaicin engaged with tNOX and triggered the proteasomal degradation of tNOX, which leads to the inhibition of NAD+-dependent SIRT1 deacetylase. Ultimately, the acetylation levels of c-Myc and p53 were enhanced, which suppressed the activation of G1 cyclin/Cyclin-dependent kinase complexes and triggered cell cycle arrest in cancer cells. The results obtained when tNOX was overexpressed in non-cancer cells validated its importance in cell cycle progression. These findings provide the first molecular insights into the regulatory role of tNOX and the anti-proliferative property of capsaicin in regulating the cell cycle of bladder cancer cells

The Use of Immune Regulation in Treating Head and Neck Squamous Cell Carcinoma (HNSCC)

Immunotherapy has emerged as a promising new treatment modality for head and neck cancer, offering the potential for targeted and effective cancer management. Squamous cell carcinomas pose significant challenges due to their aggressive nature and limited treatment options. Conventional therapies such as surgery, radiation, and chemotherapy often have limited success rates and can have significant side effects. Immunotherapy harnesses the power of the immune system to recognize and eliminate cancer cells, and thus represents a novel approach with the potential to improve patient outcomes. In the management of head and neck squamous cell carcinoma (HNSCC), important contributions are made by immunotherapies, including adaptive cell therapy (ACT) and immune checkpoint inhibitor therapy. In this review, we are focusing on the latter. Immune checkpoint inhibitors target proteins such as programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) to enhance the immune response against cancer cells. The CTLA-4 inhibitors, such as ipilimumab and tremelimumab, have been approved for early-stage clinical trials and have shown promising outcomes in terms of tumor regression and durable responses in patients with advanced HNSCC. Thus, immune checkpoint inhibitor therapy holds promise in overcoming the limitations of conventional therapies. However, further research is needed to optimize treatment regimens, identify predictive biomarkers, and overcome potential resistance mechanisms. With ongoing advancements in immunotherapy, the future holds great potential for transforming the landscape of oral tumor treatment and providing new hope for patients

Capsaicin Targets tNOX (ENOX2) to Inhibit G1 Cyclin/CDK Complex, as Assessed by the Cellular Thermal Shift Assay (CETSA)

Capsaicin (8-methyl-N-vanillyl-6-noneamide), which is an active component in red chili peppers, is used as a chemopreventive agent that shows favorable cytotoxicity against cancer cells. Accumulating evidence indicates that capsaicin preferentially inhibits a tumor-associated NADH oxidase (tNOX, ENOX2) that is ubiquitously expressed in cancer but not in non-transformed cells. This attenuates cancer cell growth by inducing apoptosis. The capsaicin-mediated inhibition of tNOX was recently shown to prolong the cell cycle. However, the molecular events underlying this regulation have not yet been investigated. In the present study, we used a cellular thermal shift assay (CETSA) to detect “target engagement” of capsaicin and its consequent impact on cell cycle progression. Our results indicated that capsaicin engaged with tNOX and triggered the proteasomal degradation of tNOX, which leads to the inhibition of NAD+-dependent SIRT1 deacetylase. Ultimately, the acetylation levels of c-Myc and p53 were enhanced, which suppressed the activation of G1 cyclin/Cyclin-dependent kinase complexes and triggered cell cycle arrest in cancer cells. The results obtained when tNOX was overexpressed in non-cancer cells validated its importance in cell cycle progression. These findings provide the first molecular insights into the regulatory role of tNOX and the anti-proliferative property of capsaicin in regulating the cell cycle of bladder cancer cells

Capsaicin acts through tNOX (ENOX2) to induce autophagic apoptosis in p53-mutated HSC-3 cells but autophagy in p53-functional SAS oral cancer cells

Despite the progress that has been made in diagnosing and treating oral cancers, they continue to have a poor prognosis, with a 5-year overall survival rate of approximately 50%. We have intensively studied the anticancer properties of capsaicin (a burning constituent of chili pepper), mainly focusing on its apoptotic properties. Here, we investigated the interplay between apoptosis and autophagy in capsaicin-treated oral cancer cells with either functional or mutant p53. Cytotoxicity was determined by cell impedance measurements and WST-1 assays, and cell death was analyzed by flow cytometry. The interaction between capsaicin and tumor-associated NADH oxidase (tNOX, ENOX2) was studied by cellular thermal shift assay (CETSA) and isothermal dose-response fingerprint curves (ITDRFCETSA). Our CETSA data suggested that capsaicin directly engaged with tNOX, resulting in its degradation through the ubiquitin-proteasome and the autophagy-lysosome systems. In p53-functional SAS cells, capsaicin induced significant cytotoxicity via autophagy but not apoptosis. Given that tNOX catalyzes the oxidation of NADH, the direct binding of capsaicin to tNOX also inhibited the NAD+-dependent activity of sirtuin 1 (SIRT1) deacetylase, we found that capsaicin-induced autophagy involved enhanced acetylation of ULK1, which is a key player in autophagy activation, possibly through SIRT1 inhibition. In p53-mutated HSC-3 cells, capsaicin triggered both autophagy and apoptosis. In this case, autophagy occurred before apoptosis: during this early stage, autophagy seemed to inhibit apoptosis; at a later stage, in contrast, autophagy appeared to be essential for the induction of apoptosis. Western blot analysis revealed that the reduction in tNOX and SIRT1 associated with enhanced ULK1 acetylation and c-Myc acetylation, which in turn, reactivated the TRAIL pathway, ultimately leading to apoptosis. Taken together, our data highlight the potential value of leveraging capsaicin and tNOX in therapeutic strategies against oral cancer