Resistant Head And Neck Cancer Research Articles

IP3R1 dysregulation via mir-200c-3p/SSFA2 axis contributes to taxol resistance in head and neck cancer

Head and neck cancer (HNC) is the sixth most common malignancy worldwide. Although current modalities offer a wide variety of therapy choices, head and neck carcinoma has poor prognosis due to its diagnosis at later stages and development of resistance to current therapeutic tools. In the current study, we aimed at exploring the roles of miR-200c-3p during head and neck carcinogenesis and acquisition of taxol resistance. We analyzed miR-200c-3p levels in HNC clinical samples and cell lines using quantitative real-time polymerase chain reaction and evaluated the effects of differential miR-200c-3p expression on cancer-related cellular phenotypes using in-vitro tools. We identified and characterized a direct target of miR-200c-3p using in-silico tools, luciferase and various in-vitro assays. We investigated potential involvement of miR-200c-3p/SSFA2 axis in taxol resistance in-vitro. We found miR-200c-3p expression as significantly downregulated in both HNC tissues and cells compared to corresponding controls. Ectopic miR-200c-3p expression in HNC cells significantly inhibited cancer-related phenotypes such as viability, clonogenicity, migration, and invasion. We, then, identified SSFA2 as a direct target of miR-200c-3p and demonstrated that overexpression of SSFA2 induced malignant phenotypes in HNC cells. Furthermore, we found reduced miR-200c-3p expression in parallel with overexpression of SSFA2 in taxol resistant HNC cells compared to parental sensitive cells. Both involved in intracellular cytoskeleton remodeling, we found that SSFA2 works collaboratively with IP3R1 to modulate resistance to taxol in HNC cells. When considered collectively, our results showed that miR-200c-3p acts as a tumor suppressor microRNA and targets SSFA2/IP3R1 axis to sensitize HNC cells to taxol.

SOD2 Enhancement by Long-Term Inhibition of the PI3K Pathway Confers Multi-Drug Resistance and Enhanced Tumor-Initiating Features in Head and Neck Cancer.

The phosphoinositide-3-kinase (PI3K) pathway has widely been considered as a potential therapeutic target for head and neck cancer (HNC); however, the application of PI3K inhibitors is often overshadowed by the induction of drug resistance with unknown mechanisms. In this study, PII3K inhibitor resistant cancer cells were developed by prolonged culturing of cell lines with BEZ235, a dual PI3K and mammalian target of rapamycin (mTOR) inhibitor. The drug resistant HNC cells showed higher IC50 of the proliferation to inhibitors specifically targeting PI3K and/or mTOR, as compared to their parental cells. These cells also showed profound resistance to drugs of other classes. Molecular analysis revealed persistent activation of phosphorylated AKT at threonine 308 in the drug resistant cells and increased expression of markers for tumor-initiating cells. Interestingly, increased intra-cellular ROS levels were observed in the drug resistant cells. Among anti-oxidant molecules, the expression of SOD2 was increased and was associated with the ALDH-positive tumor-initiating cell features. Co-incubation of SOD inhibitors and BEZ235 decreased the stemness feature of the cells in vitro, as shown by results of the spheroid formation assay. In conclusion, dysregulation of SOD2 might contribute to the profound resistance to PI3K inhibitors and the other drugs in HNC cells.

CISD2 inhibition overcomes resistance to sulfasalazine-induced ferroptotic cell death in head and neck cancer

Sulfasalazine has been repurposed to induce ferroptotic cancer cell death via inhibition of xc−-cystine/glutamate antiporter (xCT). However, cancer cells are capable of developing mechanisms to evade cell death. Therefore, we sought to determine the molecular mechanisms underlying resistance to sulfasalazine-induced ferroptosis in head and neck cancer (HNC). The effects of sulfasalazine and pioglitazone were tested in various HNC cell lines. The effects of these drugs and inhibition and overexpression of CISD2 gene were determined by evaluating viability, cell death, lipid ROS production, mitochondrial iron, and mouse tumor xenograft models. SAS induced ferroptotic cell death in HNC at different levels. CISD2 expression showed an association between its expression and ferroptosis resistance. CISD2 overexpression conferred resistance to ferroptosis by sulfasalazine. Silencing CISD2 gene rendered resistant HNC cells susceptible to sulfasalazine-induced ferroptosis, with increased levels of lipid ROS and mitochondrial ferrous iron. Pioglitazone induced over-accumulation of mitochondrial iron and ROS and sensitized resistant HNC cells to sulfasalazine treatment in vitro and in a mouse tumor-xenograft model. CISD2 inhibition overcomes HNC resistance to ferroptotic cell death induced by sulfasalazine via increased accumulation of mitochondrial ferrous iron and lipid ROS.

Abstract 1210: Hederagenin overcomes the cisplatin resistance of head and neck cancer by targeting the antioxidant defense mechanisms

Abstract Background: Cisplatin is a first-line chemotherapeutic agent for head and neck cancer (HNC). Acquired resistance to cisplatin is the most common reason for the failure of cisplatin chemotherapy. Hederagenin is extracted from the leaves of Cyclocarya paliurus, also known as sweet tea, which is one of the most popular teas utilized in traditional Chinese medicine. There is accumulating evidence it exhibited significant cytotoxicity against several types of cancers, however, which has been rarely tested in HNC cells. Herein, we examined the potential utility of hederagenin for overcoming cisplatin resistance in HNC cells and further clarified its molecular mechanisms of action. Methods: Parental and cisplatin-resistant HNC cells, and Nrf2 or SLC7A11 gene overexpressed HNC cell lines and other human HNC cells were used. The cells were used to examine the effects of hederagenin treatment in HNC cell lines by measuring cell viability, cell cycle, cell death, reactive oxygen species (ROS) production, glutathione level, mitochondrial membrane potential (ΔΨm), and protein expression. The anti-tumor effect of hederagenin in mouse tumor xenograft models was also tested. Results: Hederagenin induced cell death in both cisplatin-sensitive and -resistant HNC cells. Hederagenin treatment resulted in effective death of cisplatin-resistant HNC cells in a form of apoptotic cell death with the ΔΨm change. Hederagenin inhibited Nrf2 and SLC7A11 resulting in an increased ROS accumulation in HNC cells, of which effects were reversed by the pretreatment of antioxidant trolox. In addition, hederagenin caused the apoptosis effectively induced by targeting the antioxidant defense mechanisms in HNC cells. Subsequently, hederagenin activated signaling pathways of cell death involving caspase-3, PUMA, and PARP in the cells. The growth inhibitory effects of hedragenin were also confirmed in the tumor xenograft model implanted with cisplatin-resistant HNC cells. Conclusions: Our data suggests that hederagenin can overcome the resistance of cisplatin in resistant HNC cells via targeting antioxidant systems. Citation Format: Daiha Shin, Eun Hye Kim, Hyejin Jang, Jaewang Lee, Ji Won Kim, Jae Ryung Lee, Minsu Kwon, Seungho Baek, Jong-Lyel Roh. Hederagenin overcomes the cisplatin resistance of head and neck cancer by targeting the antioxidant defense mechanisms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1210. doi:10.1158/1538-7445.AM2017-1210

RITA plus 3-MA overcomes chemoresistance of head and neck cancer cells via dual inhibition of autophagy and antioxidant systems

Reactivation of p53 and induction of tumor cell apoptosis (RITA) is a small molecule that blocks p53–MDM2 interaction, thereby reactivating p53 in tumors. RITA can induce exclusive apoptosis in cancer cells independently of the p53 pathway; however, the resistance of cancer cells remains a major drawback. Here, we found a novel resistance mechanism of RITA treatment and an effective combined treatment to overcome RITA resistance in head and neck cancer (HNC) cells. The effects of RITA and 3-methyladenine (3-MA) were tested in different HNC cell lines, including cisplatin-resistant and acquired RITA-resistant HNC cells. The effects of each drug alone and in combination were assessed by measuring cell viability, apoptosis, cell cycle, glutathione, reactive oxygen species, protein expression, genetic inhibition of p62 and Nrf2, and a mouse xenograft model of cisplatin-resistant HNC. RITA induced apoptosis of HNC cells at different levels without significantly inhibiting normal cell viability. Following RITA treatment, RITA-resistant HNC cells exhibited a sustained expression of other autophagy-related proteins, overexpressed p62, and displayed activation of the Keap1-Nrf2 antioxidant pathway. The autophagy inhibitor 3-MA sensitized resistant HNC cells to RITA treatment via the dual inhibition of molecules related to the autophagy and antioxidant systems. Silencing of the p62 gene augmented the combined effects. The effective antitumor activity of RITA plus 3-MA was also confirmed in vivo in mouse xenograft models transplanted with resistant HNC cells, showing increased oxidative stress and DNA damage. The results indicate that RITA plus 3-MA can help overcome RITA resistance in HNC cells. Condensed abstractThis study revealed a novel RITA resistant mechanism associated with the sustained induction of autophagy, p62 overexpression, and Keap1-Nrf2 antioxidant system activation. The combined treatment of RITA with the autophagy inhibitor 3-methyladenine overcomes RITA resistance via dual inhibition of autophagy and antioxidant systems in vitro and in vivo.

Aspirin plus sorafenib potentiates cisplatin cytotoxicity in resistant head and neck cancer cells through xCT inhibition

The nonsteroidal anti-inflammatory drug aspirin and the multikinase inhibitor sorafenib have both shown experimental and clinical anticancer activities. The present study investigated whether aspirin and sorafenib synergize to potentiate cisplatin treatment in resistant head and neck cancer (HNC) cells. The effects of aspirin, sorafenib and cisplatin, and combinations thereof were assessed by measuring cell viability, death, glutathione (GSH) and reactive oxygen species (ROS) levels, protein and mRNA expression, genetic inhibition and overexpression of cystine–glutamate antiporter (xCT) and tumor xenograft mouse models. Even at low concentrations, aspirin plus sorafenib synergized to induce cell death of cisplatin-resistant HNC cells. The combination of aspirin and sorafenib induced xCT inhibition, GSH depletion, and ROS accumulation in cancer cells. Genetic and pharmacological inhibition of xCT potentiated the cytotoxic effects of aspirin plus sorafenib; this effect was diminished by xCT overexpression. Low-dose aspirin plus sorafenib enhanced the cytotoxicity of cisplatin in resistant HNC cells through xCT inhibition and oxidant and DNA damage. The in vivo effects of aspirin plus sorafenib on cisplatin therapy were also confirmed in resistant HNC xenograft models, in terms of growth inhibition, GSH depletion, and increased γH2AX formation and apoptosis in tumors. Aspirin and sorafenib synergize to potentiate the cytotoxicity of cisplatin in resistant HNC cells. This therapeutic strategy may help to eliminate resistant HNC.

Hederagenin Induces Apoptosis in Cisplatin-Resistant Head and Neck Cancer Cells by Inhibiting the Nrf2-ARE Antioxidant Pathway.

Acquired resistance to cisplatin is the most common reason for the failure of cisplatin chemotherapy. Hederagenin, triterpenoids extracted from ivy leaves, exhibits antitumor activity in various types of cancer. However, the therapeutic potential of hederagenin in head and neck cancer (HNC) has remained unclear. Therefore, we examined the effects of hederagenin in cisplatin-resistant HNC cells and characterized its molecular mechanisms of action in this context. We evaluated the effects of hederagenin treatment on cell viability, apoptosis, reactive oxygen species (ROS) production, glutathione levels, mitochondrial membrane potential (ΔΨm), and protein and mRNA expression in HNC cells. The antitumor effect of hederagenin in mouse tumor xenograft models was also analyzed. Hederagenin selectively induced cell death in both cisplatin-sensitive and cisplatin-resistant HNC cells by promoting changes in ΔΨm and inducing apoptosis. Hederagenin inhibited the Nrf2-antioxidant response element (ARE) pathway and activated p53 in HNC cells, thereby enhancing ROS production and promoting glutathione depletion. These effects were reversed by the antioxidant trolox. Hederagenin activated intrinsic apoptotic pathways via cleaved PARP, cleaved caspase-3, and Bax. The selective inhibitory effects of hederagenin were confirmed in cisplatin-resistant HNC xenograft models. These data suggest that hederagenin induces cell death in resistant HNC cells via the Nrf2-ARE antioxidant pathway.

Nrf2 inhibition reverses the resistance of cisplatin-resistant head and neck cancer cells to artesunate-induced ferroptosis

Artesunate, an anti-malarial drug, has been repurposed as an anticancer drug due to its induction of cell death via reactive oxygen species (ROS) production. However, the molecular mechanisms regulating cancer cell death and the resistance of cells to artesunate remain unclear. We investigated the molecular mechanisms behind the antitumor effects of artesunate and an approach to overcome artesunate resistance in head and neck cancer (HNC). The effects of artesunate and trigonelline were tested in different HNC cell lines, including three cisplatin-resistant HNC cell lines. The effects of these drugs as well as the inhibition of Keap1, Nrf2, and HO-1 were assessed by cell viability, cell death, glutathione (GSH) and ROS production, protein expression, and mouse tumor xenograft models. Artesunate selectively killed HNC cells but not normal cells. The artesunate sensitivity was relatively low in cisplatin-resistant HNC cells. Artesunate induced ferroptosis in HNC cells by decreasing cellular GSH levels and increasing lipid ROS levels. This effect was blocked by co-incubation with ferrostatin-1 and a trolox pretreatment. Artesunate activated the Nrf2–antioxidant response element (ARE) pathway in HNC cells, which contributed to ferroptosis resistance. The silencing of Keap1, a negative regulator of Nrf2, decreased artesunate sensitivity in HNC cells. Nrf2 genetic silencing or trigonelline reversed the ferroptosis resistance of Keap1-silenced and cisplatin-resistant HNC cells to artesunate in vitro and in vivo. Nrf2–ARE pathway activation contributes to the artesunate resistance of HNC cells, and inhibition of this pathway abolishes ferroptosis-resistant HNC. Condensed abstractOur results show the effectiveness and molecular mechanism of artesunate treatment on head and neck cancer (HNC). Artesunate selectively killed HNC cells but not normal cells by inducing an iron-dependent, ROS-accumulated ferroptosis. However, this effect may be suboptimal in some cisplatin-resistant HNCs because of Nrf2–antioxidant response element (ARE) pathway activation. Inhibition of the Nrf2–ARE pathway increased artesunate sensitivity and reversed the ferroptosis resistance in resistant HNC cells.

Targeting of the Glutathione, Thioredoxin, and Nrf2 Antioxidant Systems in Head and Neck Cancer

The glutathione (GSH), thioredoxin (Trx), and Nrf2 systems represent a major defense against reactive oxygen species (ROS), the cellular imbalance of which in cancer promotes growth and therapeutic resistance. This study investigated whether targeting the GSH, Trx, and Nrf2 antioxidant systems effectively eliminated head and neck cancer (HNC). At high concentrations, auranofin, but not buthionine sulfoximine (BSO) alone, decreased the viability of HNC, whereas even at low concentrations, auranofin plus BSO synergized to kill HNC cells. Dual silencing of the genes for GCLM and TrxR1 induced GSH depletion, Trx activity inhibition, and ROS accumulation, synergistically killing HNC cells. Inhibition of the GSH and Trx systems resulted in activation of the Nrf2-antioxidant response element (ARE) pathway, which may result in suboptimal GSH and Trx inhibition where HNC is resistant. Genetic inhibition of Nrf2 and/or HO-1 or trigonelline enhanced growth suppression, ROS accumulation, and cell death from GSH and Trx inhibition. The in vivo effects of GSH, Trx, and Nrf2 system inhibition were confirmed in a mouse HNC xenograft model by achieving growth inhibition >60% compared with those of control. Innovations: This study is the first to show that triple inhibition of GSH, Trx, and Nrf2 pathways could be an effective method to overcome the resistance of HNC. Inhibition of the Nrf2-ARE pathway in addition to dual inhibition of the GSH and Trx antioxidant systems can effectively eliminate resistant HNC. Antioxid. Redox Signal. 27, 106-114.

Targeting Nrf2 with wogonin overcomes cisplatin resistance in head and neck cancer.

A principal limitation to the clinical use of cisplatin is the high incidence of chemoresistance to this drug. Combination treatments with other drugs may help to circumvent this problem. Wogonin, one of the major natural flavonoids, is known to reverse multidrug resistance in several types of cancers. We investigated the ability of wogonin to overcome cisplatin resistance in head and neck cancer (HNC) cells and further clarified its molecular mechanisms of action. Two cisplatin-resistant HNC cell lines (AMC-HN4R and -HN9R) and their parental and other human HNC cell lines were used. The effects of wogonin, either alone or in combination with cisplatin, were assessed in HNC cells and normal cells using cell cycle and death assays and by measuring cell viability, reactive oxygen species (ROS) production, and protein expression, and in tumor xenograft mouse models. Wogonin selectively killed HNC cells but spared normal cells. It inhibited nuclear factor erythroid 2-related factor 2 and glutathione S-transferase P in cisplatin-resistant HNC cells, resulting in increased ROS accumulation in HNC cells, an effect that could be blocked by the antioxidant N-acetyl-L-cysteine. Wogonin also induced selective cell death by targeting the antioxidant defense mechanisms enhanced in the resistant HNC cells and activating cell death pathways involving PUMA and PARP. Hence, wogonin significantly sensitized resistant HNC cells to cisplatin both in vitro and in vivo. Wogonin is a promising anticancer candidate that induces ROS accumulation and selective cytotoxicity in HNC cells and can help to overcome cisplatin-resistance in this cancer.

Induction of ferroptotic cell death for overcoming cisplatin resistance of head and neck cancer

Inhibition of key molecules related to ferroptosis, cystine/glutamate antiporter and glutathione peroxidase, may induce eradication of chemotherapy/radiotherapy-resistant cancer cells. The present study investigated whether ferroptosis could overcome head and neck cancer (HNC) resistance to cisplatin treatment. Three cisplatin-resistant HNC cell lines (AMC-HN3R, -HN4R, and -HN9R) and their parental lines were used. The effects of cystine and glutamate alteration and pharmacological and genetic inhibition of cystine/glutamate antiporter were assessed by measuring viability, death, reactive oxygen species production, protein expression, and preclinical mouse tumor xenograft models. Conditioned media with no cystine or glutamine excess induced ferroptosis of both cisplatin-sensitive and -resistant HNC cells without any apparent changes to necrosis and apoptosis markers. The cystine/glutamate antiporter inhibitors erastin and sulfasalazine inhibited HNC cell growth and accumulated lipid reactive oxygen species, thereby inducing ferroptosis. Genetic silencing of cystine/glutamate antiporter with siRNA or shRNA treatment also induced effective ferroptotic cell death of resistant HNC cells and enhanced the cisplatin cytotoxicity of resistant HNC cells. Pharmacological and genetic inhibition of cystine/glutamate antiporter significantly sensitized resistant HNC cells to cisplatin in vitro and in vivo. Pharmacological and genetic inhibition of cystine/glutamate antiporter overcomes the cisplatin resistance of HNC cells by inducing ferroptosis.

Abstract 3575: Ferroptosis: A novel nonapoptotic cell death overcomes head and neck cancer resistance to cisplatin

Abstract Ferroptosis was recently identified as a novel form of iron-dependent cell death different from apoptosis or necrosis. Inhibition of key molecules related to ferroptosis, cystine-glutamate antiporter (xCT) and glutathione peroxidase (GPX4), may induce the eradication of cancer cells resistant to conventional chemotherapy or radiotherapy. The present study investigated whether ferroptosis overcome head and neck cancer (HNC) resistant to cisplatin treatment. Three cisplatin-resistant HNC cell lines (AMC-HN3R, -HN4R and -HN9R), their parental lines, and other human HNC lines were used. The effects of cysteine and glutamate alteration and pharmacological and genetic inhibition of xCT were assess by measuring viability, death, total and cytoplasmic lipid reactive oxygen species (ROS) production, mitochondrial membrane potential (ΔΨm), protein expression, and preclinical mouse tumor xenograft models. Conditioned media with no cysteine or high glutamate supplement induced ferroptosis of both cisplatin-sensitive and -resistant HNC cells without apparent change of necrosis and apoptosis markers, RIP1 and RIP3 and casplase-3 expression, and ΔΨm. This was blocked by antioxidants trolox or N-acetyl cysteine pretreatment. Sulfasalazine, artensunate, and erastin inhibited the growth of HNC cells and accumulated cytoplasmic lipid ROS via induction of ferroptosis and inhibition of xCT protein expression. Genetic silencing of xCT with siRNA or shRNA treatment also induced the effective cell death (ferroptosis) of resistant HNC cells. These effects were blocked with trolox or ferrostatin-1 pretreatment. Pharmacological and genetic inhibition of xCT significantly sensitized resistant HNC cells to cisplatin in vitro and in vivo. Cystine deficiency or glutamate excess induces ferroptosis in HNC cells. Further, pharmacological and genetic inhibition of xCT overcomes the cisplatin resistance of HNC cells by inducing ferroptosis. Citation Format: Hye Jin Jang, Jin Young Park, Eun Hye Kim, Ji Won Kim, Minsu Kwon, Jong-Lyel Roh. Ferroptosis: A novel nonapoptotic cell death overcomes head and neck cancer resistance to cisplatin. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3575.

Activation of mitochondrial oxidation by PDK2 inhibition reverses cisplatin resistance in head and neck cancer

Dichloroacetate (DCA), an orphan drug that promotes a shift from glycolysis to oxidative phosphorylation, has been repurposed for cancer therapy. The present study investigated whether DCA may overcome cisplatin resistance in head and neck cancer (HNC). Two cisplatin-resistant HNC cell lines (AMC-HN4R and -HN9R), their parental lines, and other human HNC lines were used. The effect of DCA, alone and in combination with cisplatin, was assessed by measuring cell cycle, viability, death, reactive oxygen species (ROS) production, mitochondrial membrane potential (ΔΨm), and protein expression in preclinical mouse tumor xenograft models. Increased glycolysis correlated with decreased sensitivity to cisplatin and was reduced by DCA. Cisplatin-resistant cells overexpressed pyruvate dehydrogenase kinase 2 (PDK2). DCA induced HNC cell death by decreasing ΔΨm and promoting mitochondrial ROS production. This effect was decreased by the antioxidant N-acetyl-l-cysteine or by inhibition of caspase-mediated apoptosis. Activation of mitochondrial glucose oxidation by DCA eventually activated downstream mitochondrial apoptotic signaling, leading to the death of chemoresistant cancer cells. Therefore, DCA significantly sensitized resistant HNC cells to cisplatin in vitro and in vivo. High glycolysis and PDK2 overexpression are closely linked to cisplatin resistance in HNC cells; the latter can be overcome by DCA.

Inhibition of Glucosylceramide Synthase Sensitizes Head and Neck Cancer to Cisplatin.

Glucosylceramide synthase (GCS) overexpression is associated with multidrug resistance in several human cancers. GCS blockade, which overcomes multidrug resistance by downregulating P-glycoprotein (P-gp), has not been tested in head and neck cancer (HNC). This study investigates whether GCS is targetable in HNC by assessing whether GCS inhibition sensitizes HNC to cisplatin. The effect of genetic or pharmacologic GCS inhibition (using GCS siRNA/shRNA or d,l-threo-PPMP, respectively) on cisplatin sensitivity was assessed in several human HNC cells and acquired cisplatin-resistant HNC cells by measuring cell viability, cell cycle, death, mRNA and protein expression, ceramide production, and in preclinical tumor xenograft mouse models. GCS and P-gp expression were significantly associated with cisplatin resistance in several HNC cell lines (P = 0.007). Both were significantly increased in HN9-cisR cells, which display acquired cisplatin resistance (P < 0.001). Genetic or pharmacologic inhibition of GCS induced accumulation of increased ceramide levels. GCS inhibition increased cisplatin-induced cell death in HNC cells via P-gp downregulation and proapoptotic protein activation, which were abrogated by siPUMA transfection. Genetic and pharmacologic GCS inhibition sensitized resistant HNC cells to cisplatin in vitro and in vivo. GCS and P-gp overexpression is associated with acquired cisplatin resistance, suggesting a role for these molecules as therapeutic targets for HNC. Genetic or pharmacologic GCS blockade may have therapeutic benefit in cisplatin-resistant HNC.

Abstract 5454: Wogonin overcomes cisplatin resistance of head and neck cancer by targeting antioxidant defense mechanisms

Abstract Background: Cisplatin is a first-line chemotherapeutic agent for head and neck cancer (HNC). However, the main limitation to clinical usefulness of cisplatin is the high incidence of chemoresistance causing one of major failures in cancer management. This may suggests the necessity of combination therapies of cisplatin with other drugs to circumvent chemoresistance. Wogonin, one of major natural flavonoids, is known to reverse multidrug resistance in several types of cancers, however, which has been rarely tested in HNC cells. Therefore, the present study investigated the ability and molecular mechanisms of wogonin overcoming cisplatin resistance in HNC cells. Methods: Two cisplatin-resistance HNC cell lines (AMC-HN4R and -HN9R) and their parental and other human HNC cell lines were used. The effect of wogonin, alone and in combination with cisplatin, was assessed in HNC cells and normal cells by measuring cell viability, cell cycle and death assays, reactive oxygen species (ROS) production, and protein expression, and in preclinical tumor xenograft mouse models. Results: Wogonin selectively killed HNC cells but spared normal cells. It inhibited NF-E2-related factor 2 (NRF2), P-glycoprotein, and glutathione S-transferase P (GSTP), overexpressed in cisplatin-resistant HNC cells, resulting in the increased ROS accumulation in HNC cells, an effect that can be blocked by the antioxidant N-acetyl-L-cysteine. Wogonin also induced selective cell death by targeting the antioxidant defense mechanisms enhanced in the resistant HNC cells and subsequently, effectively activating cell death pathways involving PUMA and PARP. Therefore, wogonin significantly sensitized the resistant HNC cells to cisplatin in vitro and in vivo. Conclusions: Wogonin might be the promising anticancer candidate by inducing ROS accumulation and selective killing HNC cells, thus contributing to overcome the cisplatin-resistance of HNC cells. Citation Format: Ji Won Kim, Eun Hye Kim, Jin Young Park, Minsu Kwon, Jong-Lyel Roh. Wogonin overcomes cisplatin resistance of head and neck cancer by targeting antioxidant defense mechanisms. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5454. doi:10.1158/1538-7445.AM2015-5454

A redox‐centered view of radiation resistance in head and neck squamous cancer (768.1)

The central issue of resistance to radiation remains a significant challenge in the treatment of cancer despite improvements in treatment modality and emergence of new therapies. To facilitate the identification of molecular factors that elicit protection against radiation, we developed a matched model of radiation resistance for head and neck cancer (HNC) and characterized its properties using selective chemical probes for protein oxidation, omics technologies and complementary assays. Functional network analysis of proteomics data identified DNA replication and base excision repair, ECM‐receptor interaction, and regulation of actin cytoskeleton as significantly up‐ or down‐regulated networks in resistant (rSCC‐61) HNC cells. Up‐regulated proteins in rSCC‐61 included enzymes involved in lipid metabolism and antioxidant system. Redox proteomics analysis using biotin‐tagged chemical probes and mass spectrometry identified decreased oxidative damage of the antioxidant system in rSCC‐61 consistent with the cells increased ability to withstand a radiation insult. Further metabolomics and epigenetics studies of this system show that multiple pathways converge to produce the rSCC‐61 phenotype and point to the function of the antioxidant system as major regulator of resistance to ionizing radiation in rSCC‐61, a phenomenon confirmed by analysis of HNC tumor samples.