Abstract 1388: Non-thermal plasma-activated medium induces ferroptotic cell death by intracellular ferrous iron overload in head and neck cancer

The notoriously high proliferation rate of cancer cells requires them to constantly deal with the balance adjustment between oxidative stress overload and upregulated protective antioxidant pathways. It puts them in a vulnerable state whenever one piece of this puzzle went out of control. Non-thermal plasma (NTP) is partially ionized gas operated at or around body temperature and has emerged as a new potential anti-cancer therapy due to its ability to release and induce ROS, RNS, and other free radicals as well as generate UV- photon and electromagnetic field; but the specific mechanism and its specificity to cancer cell are still controversial. Using transcriptomic analysis, we previously reported the link between NTP-activated media (NTPAM)and apoptosis; but the sequencing data also revealed a strong Ferroptotic response in all the 6Head and Neck cancer cell lines we checked. Ferroptosis is a newly identified oxidative-regulated cell death, characterized by the iron-dependent generation of lipid peroxidation. In this study, we found the prolonged treatment of NTPAM-induced cell death via the non-canonical ferroptosis pathway by directly increasing intracellular toxic ferrous Iron (Fe2+). We found that the excessive overexpression of HMOX1 under prolonged NTPAM-induced oxidative stress was actually responsible for the surge of intracellular Fe2+ due to the increase of heme degradation. Pharmacological inhibition or RNA silencing of HMOX1 was able to rescue 2 HNC cell lines from NTPAM-induced increased Iron concentration as well as ferroptosis cell death, both in vivo and in vitro. These results suggest NTP directly induces ferroptosis via an increase of Fe2+ concentration by triggering the over-responding of the NRF2 - HMOX1 antioxidant system. This finding could be exploited to develop future NTP-based cancer therapy as well as in combination with other Iron sensitive anti-neoplastic agents; and could be a potential method of overcoming conventional cancer treatment resistance.

Citation Format: QuocKhanh Nguyen, Chan Oh, Seung-Nam Jung, Yudan Piao, Mi Ae Lim, Young Il Kim, Yanli Jin, Hae Jong Kim, Bon Seok Koo. Non-thermal plasma-activated medium induces ferroptotic cell death by intracellular ferrous iron overload in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1388.

Mitochondrial ribosomal protein L14 promotes cell growth and invasion through modulating ROS in thyroid cancer

Objectives

The mitochondrial ribosomal protein L14 (MRPL14) is encoded by a nuclear gene and participates in mitochondrial protein translation. In this study, we aimed to investigate the role of MRPL14 in thyroid carcinoma.

Methods

We investigated the association of expression of MRPL14 and clinicopathological features using the The Cancer Genome Atlas (TCGA) and Chungnam National University Hospital (CNUH) databases. Functional studies of MRPL14, including proliferation, migration, invasion, mitochondrial oxidative phosphorylation and reactive oxygen species (ROS) production, were performed in papillary thyroid carcinoma (PTC) cell lines (B-CPAP and KTC-1).

Results

Based on TCGA dataset, PTC tissues lost mitochondrial integrity and showed dysregulated expression of overall mitoribosomal proteins (MRPs) compared with normal thyroid tissues. Of 78 MRPs, MRPL14 was highly expressed in thyroid carcinoma tissues. MRPL14 overexpression was significantly associated with advanced tumor stage, extrathyroidal extension, and lymph node metastasis. MRL14 increased cell proliferation of thyroid cancer and promoted cell migration via epithelial-mesenchymal transition-related proteins. Moreover, MRPL14 knockdown reduced the expression of oxidative phosphorylation complex IV (MTCO1) and increased the accumulation of ROS. Co-treatment with a ROS scavenger restored cell proliferation and migration reduced by MRPL14 knockdown, which imply that ROS functions as a key regulator of the oncogenic effects of MRPL14 in thyroid cancer cells.

Conclusion

Our findings indicate that MRPL14 may promote cell growth, migration, and invasion through modulating ROS in thyroid cancer cells.

Claudin-1 mediates progression by regulating EMT through AMPK/TGF-β signaling in head and neck squamous cell carcinoma

Claudin-1 (CLDN1), a major component of tight junction complexes in the epithelium, maintains cellular polarity, and plays a critical role in cell-to-cell communication as well as epithelial cell homeostasis. Although the role of CLDN1 has been widely studied in cancer, its role in the progression and the exact regulatory mechanisms, remain controversial. Using next-generation sequencing, we first analyzed the expression profiles of tumor/non-tumor paired tissue in patients with head and neck squamous cell carcinoma (HNSC) from public and local cohorts and found out that CLDN1 is upregulated in tumors compared to normal tissues. Next, its correlation with lymph node metastasis and poor prognosis was validated in the retrospective cohort, which collectively suggests CLDN1 as an oncogene in HNSC. As expected, the knockdown of CLDN1 inhibited invasive phenotypes by downregulating epithelial-to-mesenchymal transition (EMT) in vitro. To ascertain the regulatory mechanism of CLDN1 in HNSC analysis of GO term enrichment, KEGG pathways, and curated gene sets were used. As a result, CLDN1 was negatively associated with AMP-activated protein kinase (AMPK) and positively associated with transforming growth factor-β (TGF-β) signaling. In vitro mechanistic assay showed that CLDN1 inhibited AMPK phosphorylation by regulating AMPK upstream phosphatases, which led to inhibition of Smad2 activity. Intriguingly, the invasive phenotype of cancer cells increased by CLDN1 overexpression was rescued by AMPK activation, indicating a role of the CLDN1/AMPK/TGF-β/EMT cascade in HNSC. Consistently in vivo, CLDN1 suppression significantly inhibited the tumor growth, with elevated AMPK expression, suggesting the novel observation of oncogenic CLDN1-AMPK signaling in HNSC.

SHMT2 Induces Stemness and Progression of Head and Neck Cancer

Various enzymes in the one-carbon metabolic pathway are closely related to the development of tumors, and they can all be potential targets for cancer therapy. Serine hydroxymethyltransferase2 (SHMT2), a key metabolic enzyme, is very important for the proliferation and growth of cancer cells. However, the function and mechanism of SHMT2 in head and neck cancer (HNC) are not clear. An analysis of The Cancer Genome Atlas (TCGA) data showed that the expression of SHMT2 was higher in tumor tissue than in normal tissue, and its expression was significantly associated with male sex, aggressive histological grade, lymph node metastasis, distant metastasis, advanced TNM stage, and lymphovascular invasion in HNC. SHMT2 knockdown in FADU and SNU1041 cell lines significantly inhibited cell proliferation, colony formation, migration, and invasion. Additionally, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses using TCGA data revealed that SHMT2 was closely related to cancer stem cell regulation and maintenance. Furthermore, we found that silencing SHMT2 inhibited the expression of stemness markers and tumor spheroid formation compared with a control group. On the contrary, stemness markers were significantly increased after SHMT2 overexpression in HEP-2 cells. Interestingly, we found that knocking down SHMT2 reduced the expression of genes related to the Notch and Wnt pathways. Finally, silencing SHMT2 significantly reduced tumor growth and decreased stemness markers in a xenograft model. Taken together, our study suggests that targeting SHMT2 may play an important role in inhibiting HNC progression.

Transcriptomic analysis of papillary thyroid cancer focused on immune-subtyping, oncogenic fusion, and recurrence

Objectives

Thyroid cancer is the most common endocrine tumor, with rapidly increasing incidence worldwide. However, its transcriptomic characteristics associated with immunological signatures, driver fusions, and recurrence markers remain unclear. We aimed to investigate the transcriptomic characteristics of advanced papillary thyroid cancer.

Methods

This study included 282 papillary thyroid cancer tumor samples and 155 normal samples from Chungnam National University Hospital and Seoul National University Hospital. Transcriptomic quantification was determined by high-throughput RNA sequencing. We investigated the associations of clinical parameters and molecular signatures using RNA sequencing. We validated predictive biomarkers using the Cancer Genome Atlas database.

Results

Through a comparison of differentially expressed genes, gene sets, and pathways in papillary thyroid cancer compared to normal tumor-adjacent tissue, we found increased immune signaling associated with cytokines or T cells and decreased thyroid hormone synthetic pathways. In addition, patients with recurrence presented increased CD8+ T-cell and Th1-cell signatures. Interestingly, we found differentially overexpressed genes related to immune-escape signaling such as CTLA4, IDO1, LAG3, and PDCD1 in advanced papillary thyroid cancer with a low thyroid differentiation score. Fusion analysis showed that the PI3K and mitogen-activated protein kinase (MAPK) signaling pathways were regulated differently according to the RET fusion partner genes (CCDC6 or NCOA4). Finally, we identified HOXD9 as a novel molecular biomarker that predicts the recurrence of thyroid cancer in addition to known risk factors (tumor size, lymph node metastasis, and extrathyroidal extension).

Conclusion

We identified a high association with immune-escape signaling in the immune-hot group with aggressive clinical characteristics among Korean thyroid cancer patients. Moreover, RET fusion differentially regulated PI3K and MAPK signaling depending on the partner gene of RET, and HOXD9 was found to be a recurrence marker for advanced papillary thyroid cancer.

The effect of Curcumin on multi-level immune checkpoint blockade and T cell dysfunction in head and neck cancer

BACKGROUND

Despite recent advances in understanding the complex immunologic dysfunction in the tumor microenvironment (TME), fewer than 20% of patients with head and neck squamous cell carcinoma (HNSCC) respond to immune checkpoint blockade (ICB). Thus, it is important to understand how inhibitory IC receptors maintain the suppressed dysfunctional TME, and to develop more effective combination immunotherapy. This study evaluated the immune-modulating effects of Curcumin, which has well-established anti-cancer and chemopreventive properties, and its long-term safety as a phytochemical drug.

METHODS

We carried out the western blot and small interfering RNA (siRNA) transfection assay to evaluate the effects of Curcumin on IC ligands and IC ligands function in HNSCC. Through T-cell cytotoxicity assay and measurements of cytokine secretion, we assessed the effects of combination of Curcumin with programmed death-ligand 1 (PD-L1) Ab on cancer cell killing. Flow cytometry were used to analyze the effects of Curcumin on the expression of programmed cell death protein 1 (PD-1) and T-cell immunoglobulin and mucin-domain3 (TIM-3) on CD4, CD8 and Treg. Immunofluorescence, immunohistochemistry and western blot were used to detecte the cytokine (IFN-γ, Granzyme B), IC receptors (PD-1 and TIM-3) and its ligands (PD-L1, PD-L2, Galectin-9) in xenograft mouse model and 4-nitroquinoline-1-oxide (4-NQO) oral cancer model.

RESULTS

We found that Curcumin decreased the expression of IC ligands such as PD-L1, PD-L2, and Galectin-9 in HNSCC, leading to regulation of epithelial-to-mesenchymal transition-associated tumor invasion. Curcumin also effectively restored the ability of CD8⁺ cytotoxic T cells to lyse cancer cells. To evaluate the effect of Curcumin on the TME further, the 4-NQO oral cancer model was used. Curcumin increased T-cell proliferation, tumor-infiltrating lymphocytes (TILs), and effector cytokines, and decreased the expression of PD-1, TIM-3, suppressive IC receptors and their ligands (PD-L1, PD-L2, and Galectin-9) in the TME, implying reinvigoration of the exhausted CD8⁺ T cells. In addition, Curcumin inhibited expression of CD4⁺CD25⁺FoxP3⁺ Treg cells as well as PD-1 and TIM-3.

CONCLUSIONS

These results show that Curcumin reinvigorates defective T cells via multiple (PD-1 and TIM-3) and multi-level (IC receptors and its ligands) IC axis suppression, thus providing a rationale to combine Curcumin with conventional targeted therapy or ICB as a multi-faceted approach for treating patients with HNSCC.

Transcriptional Regulation of GDF15 by EGR1 Promotes Head and Neck Cancer Progression through a Positive Feedback Loop

Growth and differentiation factor 15 (GDF15), a divergent member of the transforming growth factor-β (TGF-β) superfamily, has been reported to be overexpressed in different kinds of cancer types. However, the function and mechanism of GDF15 in head and neck cancer (HNC) remains unclear. The Cancer Genome Atlas (TCGA) data show that the expression of GDF15 is significantly associated with tumor AJCC stage, lymph vascular invasion and tumor grade in HNC. In this study, we confirmed that knockdown of GDF15 attenuated: cell proliferation, migration and invasion via regulation of EMT through a canonical pathway; SMAD2/3 and noncanonical pathways; PI3K/AKT and MEK/ERK in HNC cell lines. Furthermore, we found that early growth response 1 (EGR1) was a transcription factor of GDF15. Interestingly, we also demonstrated that GDF15 could regulate the expression of EGR1, which meant a positive feedback loop occurred between these two factors. Moreover, combined inhibition of both GDF15 and EGR1 in a HNC mouse xenograft model showed significantly decreased tumor volume compared to inhibition of EGR1 or GDF15 alone. Our study showed that the GDF15–EGR1 signaling axis may be a good target in HNC patients.

Growth Differentiation Factor 15 is a Cancer Cell-Induced Mitokine That Primes Thyroid Cancer Cells for Invasiveness

Background: Mitochondrial stress is known to activate the mitochondrial unfolded protein response (UPR^mt). The UPR^mt results in the secretion of mitochondrial cytokines (mitokines), which can promote a hormetic response cell nonautonomously, and has been reported to be protumorigenic. Growth differentiation factor 15 (GDF15) is a well-characterized mitokine, which is reported to have a mitohormetic effect. Thus, we investigated whether GDF15 induction could prime a subpopulation of thyroid cancer cells to provide invasive advantages. Methods: The UPR^mt, including mitokine expression, was assessed in the context of thyroid cancer in vitro and in vivo. GDF15 expression in 266 patients with papillary thyroid carcinoma (PTC) was determined by immunohistochemistry. The serum levels of GDF15 were measured in healthy subjects and PTC patients. In addition, our own and The Cancer Genome Atlas data were analyzed to determine the expression level of GDF15 in thyroid cancers. The role of GDF15 in tumor aggressiveness was investigated by observing the effects of GDF15 knockdown in BCPAP, TPC-1, 8505C, and FRO cells. Results: Pharmacological inhibition of mitochondrial oxidative phosphorylation function in thyroid cancer cells robustly increased GDF15 expression. The expression of GDF15 was associated with activation of the mitochondrial integrated stress response pathway in PTC patients. Circulating GDF15 levels were significantly higher in PTC patients than in the controls, and tumor expression of GDF15 was related to tumor aggressiveness. In vitro and in vivo knockdown of GDF15 in a thyroid cancer model showed decreased viability, migration, and invasion compared with the control cells via regulation of STAT3. Conclusions: In this study, we demonstrated that GDF15 is a mitokine induced in thyroid cancer cells upon mitochondrial stress. GDF15-induced STAT3 activation determined tumor progression in thyroid cancer. The GDF15-STAT3 signaling axis may be a target in aggressiveness of thyroid cancer.

Effect of Urban Particulate Matter on Vocal Fold Fibrosis through the MAPK/NF-κB Signaling Pathway

Particulate matter (PM) is an environmental exposure factor that adversely affects human health. PM is a risk factor for various diseases. However, the mechanism by which PM affects the vocal folds (VF) has not yet been evaluated. Thus, we investigated the cytotoxic effects of PM on human vocal fold fibroblasts (hVFF) and the underlying signaling pathways. hVFF were isolated from human VF. The effect of PM on hVFF, and the underlying mechanism, were analyzed using Western blot, quantitative real-time polymerase chain reaction, and flow cytometry. In addition, a histological evaluation was performed in animal experiments. Cell proliferation decreased after the PM treatment. PM increased the expression of interleukin (IL)-6 and IL-1β. The generation of reactive oxygen species (ROS) in PM-treated hVFF and subsequent activation of the mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways were confirmed. Furthermore, PM increased the expression of fibrosis-related markers and induced the accumulation of collagen in the extracellular matrix. As a result, PM exposure significantly enhances the inflammatory response on VF through the ROS-mediated activation of the MAPK and NF-κB signaling pathways. In addition, PM promotes differentiation into myofibroblasts and induces fibrosis. These results suggest that PM triggers an inflammatory reaction through ROS production and causes VF fibrosis.

Brn3a/Pou4f1 Functions as a Tumor Suppressor by Targeting c-MET/STAT3 Signaling in Thyroid Cancer

BACKGROUND

Brn3a/Pou4f1 is a class IV POU domain-containing transcription factor and has been found to be expressed in a variety of cancers. However, the mechanism and action of Brn3a in thyroid cancer has not been investigated.

PURPOSE

To investigate the role of Brn3a in thyroid cancer progression and its clinical implication.

METHODS

We examined Brn3a expression status in patients with thyroid cancer and analyzed relationships between Brn3a expression and clinicopathological findings using The Cancer Genome Atlas (TCGA) database. For functional in vitro analysis, proliferation, migration, invasion assay, and Western blotting were performed after overexpression or suppression of Brn3a.

RESULTS

The promoter hypermethylation of Brn3a was found in patients with aggressive thyroid cancer and Brn3a was downregulated in tissues of patients with thyroid cancer. In TCGA database, the low-Brn3a-expression group revealed a more aggressive phenotype, including T stage and extrathyroid extension when compared with the high-Brn3a-expression group. Overexpression of Brn3a suppressed cell migration and invasion via regulation of epithelial-mesenchymal transition (EMT)-associated proteins in thyroid cancer cell lines. Brn3a overexpression also downregulated signal transducer and activator of transcription 3 (STAT3) signaling through suppression of tyrosine-protein kinase Met (c-MET). In contrast, knockdown of Brn3a by small interfering ribonucleic acid (siRNA) significantly increased cell migration and invasion through upregulation of c-MET/STAT3. These results imply that Brn3a suppresses tumor metastasis via c-MET/STAT3 inhibition and EMT suppression in thyroid cancer.

CONCLUSIONS

Our findings show that Brn3a is a potential tumor suppressor that leads to reduced cancer cell migration and invasion in thyroid cancer. Elucidation of the Brn3a-regulated cancer pathways may therefore provide novel therapeutic strategies to control thyroid cancer metastasis.

Abstract 795: GDF15, the putative mitokine factor, promotes tumor progression in thyroid cancer via STAT3 regulation

Purpose: As mitochondrial dysfunction is an integral component during the initial stages of tumorigenesis, mechanistic insight on the interaction between these two pathways may lead to novel therapeutic approaches. The aim of this study is to investigate the role of GDF15, the putative mitokine factor in thyroid tumorigenesis.

Methods: Expression levels of GDF15 was investigated using The Cancer Genome Atlas database. The role of GDF15 in tumor aggressiveness was investigated by analyzing the effects of knock-down of GDF15 on proliferation, migration, and invasion of thyroid cancer cells. Serum levels of GDF15 were measured in healthy subjects and patients with papillary thyroid cancer (PTC), and expression of GDF15 by IHC was investigated in PTC samples. To investigate the exact mechanism of GDF15 in thyroid cancer, both IPA analysis and GSEA analysis were performed using TCGA database and RNA seq data from Chungnam national university hospital.

Results: TCGA data revealed the higher expression of GDF15 in tumor samples compared to in paired non-tumor samples. Thyroid cancer cells with knock-down of GDF15 revealed the decrease of proliferation, migration, and invasion compared to control cells via regulation of STAT3. Higher serum levels of GDF15 were found in patients with thyroid cancer than in control participants, and were significantly associated with tumor stage, lymphovascular invasion, and recurrence. In addition, patients with high GDF15 expression by IHC revealed the aggressive phenotype compared to patients with low GDF15 expression.

Conclusions: GDF15 is a new biomarker for predicting tumor progression, and therapies targeting GDF15 may be effective for treating thyroid cancer.

Citation Format: Yea Eun Kang, Jae Won Chang, Lihua Liu, Kyoungmin Lee, Mi Ae Lim, Seung-Nam Jung, Chan Oh, Ho-Ryun Won, Minho Shong, Bon Seok Koo. GDF15, the putative mitokine factor, promotes tumor progression in thyroid cancer via STAT3 regulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 795.

LAMB3 is associated with disease progression and cisplatin cytotoxic sensitivity in head and neck squamous cell carcinoma

OBJECTIVES

Laminin subunit beta-3 (LAMB3) is a major component of the basement membrane zone. In our study, we investigated the role of LAMB3 in head and neck squamous cell carcinoma (HNSCC) progression and its clinical implication as a prognostic biomarker.

MATERIALS AND METHODS

A retrospective analysis of 100 patients with HNSCC who had undergone curative surgery from 1999 to 2011 was performed. We evaluated LAMB3 expression by immunohistochemistry and its associations with clinicopathological characteristics and survival. For functional in vitro analyses, cell proliferation, migration, and invasion and western blot assays were performed following LAMB3 suppression. In addition, the role of LAMB3 in cisplatin-induced cytotoxicity was clarified by measuring cell proliferation.

RESULTS

LAMB3 expression was up-regulated in HNSCC cell lines and patient tissues. High LAMB3 expression was significantly associated with positive lymph node metastasis (odds ratio: 6.316; P < 0.001) and poor prognosis in patients with HNSCC. LAMB3 suppression reduced cell migration/invasion via down-regulation of epithelial-to-mesenchymal transition-associated proteins (Vimentin and Slug). Moreover, LAMB3 suppression increased cisplatin cytotoxicity in HNSCC cells.

CONCLUSION

Our findings indicate that LAMB3 may be used as a prognostic biomarker in HNSCC and support that LAMB3 silencing could induce the sensitivity of anti-cancer drugs such as cisplatin.

Relationship Between 18F-fluorodeoxyglucose Accumulation and the BRAF V600E Mutation in Papillary Thyroid Cancer

BACKGROUND

To determine whether ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG)-PET/CT is useful for predicting the BRAF ^V600E mutation status of a primary papillary thyroid carcinoma (PTC).

METHODS

A retrospective analysis was performed in 108 patients who underwent ¹⁸F-FDG positron emission tomography-computed tomography (PET/CT) for staging before thyroidectomy and BRAF analysis in biopsy-confirmed PTC. The maximum standardized uptake value (SUV_max) of the primary tumor was calculated according to FDG accumulation. Univariate and multivariate analyses were performed to assess the association between the SUV_max and clinicopathological variables.

RESULTS

The BRAF ^V600E mutation was detected in 71 of 108 (65.7%) patients. In all subjects, the tumor size and BRAF ^V600E mutation were independently related to the SUV_max according to multivariate analyses (P = 0.002 and 0.007, respectively). The SUV_max was significantly higher in tumors with the BRAF ^V600E mutation than in tumors with wild-type BRAF (10.24 ± 11.89 versus 4.02 ± 3.86; P = 0.007). In the tumor size >1 cm subgroup, the BRAF ^V600E mutation was the only factor significantly associated with the SUV_max (P = 0.016). A SUV_max cutoff level of 4.9 was determined to be significant for predicting the BRAF ^V600E mutation status (sensitivity 77.4%, specificity 100.0%, area under the curve 0.929; P < 0.0001) according to ROC curve analysis.

CONCLUSIONS

The BRAF ^V600E mutation is independently associated with high ¹⁸F-FDG uptake in PTC, especially in those with a tumor size >1 cm.

High Expression of Angiopoietin-1 is Associated with Lymph Node Metastasis and Invasiveness of Papillary Thyroid Carcinoma

BACKGROUND

We investigated the expression of angiopoietins in patients with papillary thyroid carcinoma (PTC) and the role of angiopoietins as biomarkers predicting the aggressiveness of PTC.

METHODS

Expression of angiopoietins was evaluated by immunohistochemistry of tumor specimens from patients with PTC. We demonstrated potential correlations between expression of angiopoietins and clinicopathologic features.

RESULTS

High expression of Ang-1 was positively correlated with a tumor size >1 cm, capsular invasion, extrathyroid extension, lymphovascular invasion, lymph node metastasis, and recurrence (P < 0.05). Moreover, multivariate analysis revealed that high expression of Ang-1 was an independent risk factor for lymph node metastasis (P < 0.001, odds ratio [OR] = 62.113) and lymphovascular invasion (P = 0.027, OR 4.405). However, there was no significant correlation between Ang-2 and clinicopathologic features.

CONCLUSIONS

Our results suggest that Ang-1 can serve as a valuable prognostic biomarker for lymph node metastasis and invasiveness in patients with PTC.

LAMB3 mediates metastatic tumor behavior in papillary thyroid cancer by regulating c-MET/Akt signals

Laminin subunit beta-3 (LAMB3) encodes one of the three subunits of LM-332, a protein of the extracellular matrix secreted by cultured human keratinocytes. While LAMB3 is involved in the invasive and metastatic abilities of several tumor types, including those found in the colon, pancreas, lung, cervix, stomach, and prostate, its mechanism of action in thyroid cancer has not been investigated previously. Our results show that LAMB3 is up-regulated in papillary thyroid cancer, and that its suppression reduces cell migration/invasion via down-regulation of epithelial‒mesenchymal transition-associated proteins (N-cadherin, vimentin, slug) and inhibition of matrix metalloproteinase 9. LAMB3 suppression also significantly decreases Akt phosphorylation and inhibits the transcription of c-MET, reducing its activation. These results suggest that LAMB3 leads to tumor invasion via Akt activation induced by the HGF/c-MET axis in papillary thyroid cancer cells. Our findings reveal a novel mechanism of action for LAMB3 in papillary thyroid cancer cells.

Abstract 843: CLDN1 mediates tumor invasion in HNSCC by regulation of EMT through AMPK-TGF-β signalling

Background: Claudin-1 (CLDN1), a major component of tight junction complexes in epithelium, maintains cellular polarity and plays critical roles in cell-to-cell communication and epithelial cell homeostasis. Although, the role of CLDN1 in cancer has been generally studied in cancers, the exact regulatory mechanisms and downstream pathways in cancer have been controversial and are not completely understood.

Materials and Methods: After, analysed mutational profiling of tumor/non-tumor paired tissue in the patients with head and neck squamous cell carcinoma (HNSCC) by next-generation sequencing (NGS), CLDN1 expression levels were measured in human HNSCC cell lines and tissues from HNSCC patients using next-generation sequencing. For functional in vitro analysis, cell proliferation testing using a WST-1 assay, an invasion assay, and Western blotting was performed after CLDN1 expression regulation. In vivo validations were performed using nude mouse and patient-derived tumor xenograft (PDTX) model.

Results: Mutational profiling of tumor/non-tumor paired HNSCC tissue by NGS revealed that HNSCC tumor tissues and cell lines had relatively high levels of CLDN1 expression. Although, CLDN1 regulation did not affect proliferation of HNSCC cell lines, knock down of CLDN1 inhibited invasive characteristics (migration/invasion) with down-regulation of EMT associated proteins (vimentin and slug). We also found that CLDN1 negatively correlated with AMPK phosphorylation and AMPK activator (AICAR) showed the same effect with CLDN1 suppression on HNSCC cells without change in CLDN1 expression which lead to inhibition of TGF-β-induced Smad phosphorylation and their transcriptional activity, suggesting that CLDN1/AMPK/TGF-β cascade. Then, we confirmed antitumorigenic effects of suppression of CLDN1 in HNSCC in a nude mouse and PDTX model.

Conclusions: Our findings suggest that CLDN1 acts as oncogenic driver in HNSCC via regulating EMT through AMPK/TGF-β signalling and if validated in further studies, a CLDN1-targeting agent partnered with an existing anti-TGF-β modality could be a novel tactic to overcome HNSCC.

Citation Format: Jae Won Chang, Seung-Nam Jung, Lihua Liua, Jin Man Kim, Myung Jin Ban, Yeon Soo Kim, Bok-Soon Lee, Yang Eun Kim, Ho Ryun Won, Chul-Ho Kim, Bon Seok Koo. CLDN1 mediates tumor invasion in HNSCC by regulation of EMT through AMPK-TGF-β signalling [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 843. doi:10.1158/1538-7445.AM2017-843

Carboxyl-Terminal Modulator Protein Positively Acts as an Oncogenic Driver in Head and Neck Squamous Cell Carcinoma via Regulating Akt phosphorylation

The exact regulatory mechanisms of carboxyl-terminal modulator protein (CTMP) and its downstream pathways in cancer have been controversial and are not completely understood. Here, we report a new mechanism of regulation of Akt serine/threonine kinase, one of the most important dysregulated signals in head and neck squamous cell carcinoma (HNSCC) by the CTMP pathway and its clinical implications. We find that HNSCC tumor tissues and cell lines had relatively high levels of CTMP expression. Clinical data indicate that CTMP expression was significantly associated with positive lymph node metastasis (OR = 3.8, P = 0.033) and correlated with poor prognosis in patients with HNSCC. CTMP was also positively correlated with Akt/GSK-3β phosphorylation, Snail up-regulation and E-cadherin down-regulation, which lead to increased proliferation and epithelial-to-mesenchymal transition, suggesting that CTMP expression results in enhanced tumorigenic and metastatic properties of HNSCC cells. Moreover, CTMP suppression restores sensitivity to cisplatin chemotherapy. Intriguingly, all the molecular responses to CTMP regulation are identical regardless of p53 status in HNSCC cells. We conclude that CTMP promotes Akt phosphorylation and functions as an oncogenic driver and prognostic marker in HNSCC irrespective of p53.

Ginkgetin inhibits the growth of DU-145 prostate cancer cells through inhibition of signal transducer and activator of transcription 3 activity

Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in human cancers. Therefore, STAT3 is a therapeutic target of cancer drug discovery. We previously reported that natural products inhibited constitutively activated STAT3 in human prostate tumor cells. We used a dual-luciferase assay to screen 200 natural products isolated from herbal medicines and we identified ginkgetin obtained from the leaves of Ginkgo biloba L. as a STAT3 inhibitor. Ginkgetin inhibited both inducible and constitutively activated STAT3 and blocked the nuclear translocation of p-STAT3 in DU-145 prostate cancer cells. Furthermore, ginkgetin selectively inhibited the growth of prostate tumor cells stimulated with activated STAT3. Ginkgetin induced STAT3 dephosphorylation at Try705 and inhibited its localization to the nucleus, leading to the inhibition of expression of STAT3 target genes such as cell survival-related genes (cyclin D1 and survivin) and anti-apoptotic proteins (Bcl-2 and Bcl-xL). Therefore, ginkgetin inhibited the growth of STAT3-activated tumor cells. We also found that ginkgetin inhibited tumor growth in xenografted nude mice and downregulated p-STAT3(Tyr705) and survivin in tumor tissues. This is the first report that ginkgetin exerts antitumor activity by inhibiting STAT3. Therefore, ginkgetin is a good STAT3 inhibitor and may be a useful lead molecule for development of a therapeutic STAT3 inhibitor.

Cosmomycin C inhibits signal transducer and activator of transcription 3 (STAT3) pathways in MDA-MB-468 breast cancer cell

The signal transducer and activator of transcription 3 (STAT3) is constitutively activated in cancer cells. Therefore, blocking the aberrant activity of STAT3 in tumor cells is a validated therapeutic strategy. To discover novel inhibitors of STAT3 activity, we screened against microbial natural products using a dual-luciferase assay. Using the microbial metabolome library, we identified cosmomycin C (CosC), which was isolated from the mycelium extract of Streptomyces sp. KCTC19769, as a STAT3 pathway inhibitor. CosC inhibited STAT3 (Tyr705) phosphorylation and subsequent nuclear translocation in MDA-MB-468 breast cancer cells. CosC-mediated inhibition of STAT3 signaling pathway was confirmed by suppressed expression of STAT3 downstream target proteins including cyclin D1, Bcl-xL, survivin, Mcl-1, and VEGF in CosC-treated MDA-MB-468 cells. Flow cytometry showed that CosC caused accumulation in the G(0)-G(1) phase of the cell cycle and induced apoptosis via PARP cleavage and caspase-3 activation. Based on these findings, CosC may be a potential candidate for modulation of STAT3 pathway.

Response properties of electrosensory units in the midbrain tectum of the paddlefish (Polyodon spathula Walbaum)

Paddlefish use their peculiar rostrum to detect minute electric fields from their main prey, small water fleas. Electroreceptors over the rostrum and head sense these fields and send the information into a single hindbrain area, the dorsal octavolateral nucleus (DON). From there, information is sent to various midbrain structures, including the tectum. The response properties of primary afferent fibers and DON units has been well investigated, but nothing is known about electrosensory units in the midbrain. Here we recorded the responses of single units in the midbrain tectum and DON to uniform electric fields. Tectal units exhibited little spontaneous activity and responded to sine waves with a few, well phase-locked spikes. Phase locking was still significant at amplitudes one order of magnitude lower than in the DON. If stimulated with sinusoidal electric fields of different frequencies, phase locking in DON units decreased proportionally with frequency whereas the response of tectal units depended little on frequency. This is in agreement with behavioral studies showing that relevant frequencies range from DC to ca 20 Hz.

Reactive oxygen species stabilize hypoxia-inducible factor-1 alpha protein and stimulate transcriptional activity via AMP-activated protein kinase in DU145 human prostate cancer cells

Hypoxia-inducible factor (HIF-1) plays a central role in the cellular adaptive response to hypoxic conditions, which are closely related to pathophysiological conditions, such as cancer. Although reactive oxygen species (ROS) have been implicated in the regulation of hypoxic and non-hypoxic induction of HIF-1 under various conditions, the role of ROS is quite controversial, and the mechanism underlying the HIF-1 regulation by ROS is not completely understood yet. Here, we investigated the biochemical mechanism for the ROS-induced HIF-1 by revealing a novel role of adenosine monophosphate-activated protein kinase (AMPK) and the upstream signal components. AMPK plays an essential role as energy-sensor under adenosine triphosphate-deprived conditions. Here we report that ROS induced by a direct application of H(2)O(2) and menadione to DU145 human prostate carcinoma resulted in accumulation of HIF-1alpha protein by attenuation of its degradation and activation of its transcriptional activity in an AMPK-dependent manner. By way of contrast, AMPK was required only for the transcriptional activity of HIF-1 under hypoxic condition, revealing a differential role of AMPK in these two stimuli. Furthermore, our data show that inhibition of AMPK enhances HIF-1alpha ubiquitination under ROS condition. Finally, we show that the regulation of HIF-1 by AMPK in response to ROS is under the control of c-Jun N-terminal kinase and Janus kinase 2 pathways. Collectively, our findings identify AMPK as a key determinant of HIF-1 functions in response to ROS and its possible role in the sophisticated HIF-1 regulatory mechanisms.

Antidiabetes and antiobesity effect of cryptotanshinone via activation of AMP-activated protein kinase

Metabolic disorders, including type 2 diabetes and obesity, represent major health risks in industrialized countries. AMP-activated protein kinase (AMPK) has become the focus of a great deal of attention as a novel therapeutic target for the treatment of metabolic syndromes, because AMPK has been demonstrated to mediate, at least in part, the effects of a number of physiological and pharmacological factors that exert beneficial effects on these disorders. Thus, the identification of a compound that activates the AMPK pathway would contribute significantly to the treatment and management of such syndromes. In service of this goal, we have screened a variety of naturally occurring compounds and have identified one compound, cryptotanshinone, as a novel AMPK pathway activator. Cryptotanshinone was originally isolated from the dried roots of Salvia militorrhiza, an herb that is used extensively in Asian medicine and that is known to exert beneficial effects on the circulatory system. For the first time, in the present study, we have described the potent antidiabetic and antiobesity effects of cryptotanshinone, both in vitro and in vivo. Our findings suggest that the activation of the AMPK pathway might contribute to the development of novel therapeutic approaches for the treatment of metabolic disorders such as type 2 diabetes and obesity.

AMP-activated protein kinase activity is required for vanadate-induced hypoxia-inducible factor 1alpha expression in DU145 cells

Hypoxia-inducible factor 1 (HIF-1), a pivotal transcription factor composed of HIF-1alpha and HIF-1beta subunits, plays a major role in tumor progression by activating a number of genes critically involved in adaptation to hypoxia. HIF-1 is also induced by several carcinogenic metals. Vanadate, an environmental toxic metal, is considered as a potent inducer of tumors in animals and is reported to activate HIF-1 activity. However, the involved mechanisms are poorly understood. In the present study, we have examined the biochemical mechanisms of the vanadate-induced HIF-1 activation in cancer cells by primarily focusing on the role of AMP-activated protein kinase (AMPK), which plays an essential role as an energy sensor under ATP-deprived conditions. We demonstrate that AMPK was rapidly activated in response to vanadate in DU145 human prostate carcinoma, and that its activation preceded HIF-1alpha expression. Under this condition, inhibition of AMPK by a pharmacological and molecular approach dramatically abolished the vanadate-induced HIF-1alpha expression as well as HIF-1-mediated physiological responses. Phosphatidylinositol-3 kinase/Akt/mammalian target of rapamycin signaling was also involved in vanadate-induced HIF-1alpha expression, but it was independent of AMPK signaling pathway. Moreover, we demonstrate a role of reactive oxygen species as an upstream signal for these two pathways. These results suggest that AMPK is a novel and critical component of HIF-1 regulation, further implying its involvement in vanadate-induced carcinogenesis.

AMP-activated protein kinase activity is critical for hypoxia-inducible factor-1 transcriptional activity and its target gene expression under hypoxic conditions in DU145 cells

AMP-activated protein kinase (AMPK) functions as an energy sensor to provide metabolic adaptations under the ATP-deprived conditions such as hypoxia. In the present study, we considered a role of AMPK in the adaptive response to hypoxia by examining whether AMPK is involved in the regulation of hypoxia-inducible factor-1 (HIF-1), a heterodimeric transcription factor that is critical for hypoxic induction of physiologically important genes. We demonstrate that hypoxia or CoCl2 rapidly activated AMPK in DU145 human prostate cancer cells, and its activation preceded the induction of HIF-1 alpha expression. Under these conditions, blockade of AMPK activity by a pharmacological or molecular approach significantly attenuated hypoxia-induced responses such as HIF-1 target gene expression, secretion of vascular endothelial growth factor, glucose uptake, and HIF-1-dependent reporter gene expression, indicating that AMPK is critical for the HIF-1 transcriptional activity and its target gene expression. Its functional requirement for HIF-1 activity was also demonstrated in several different cancer cell lines, but AMPK activation alone was not sufficient to stimulate the HIF-1 transcriptional activity. We further present data showing that AMPK transmits a positive signal for HIF-1 activity via a signaling pathway that is independent of phosphatidylinositol 3-kinase/AKT and several mitogen-activated protein kinases. Taken together, our results suggest that AMPK is a novel and critical component of HIF-1 regulation, implying its new roles in oxygen-regulated cellular phenomena.