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Deuss E, Kürten C, Fehr L, Kahl L, Zimmer S, Künzel J, Stauber RH, Lang S, Hussain T, Brandau S. Standardized Digital Image Analysis of PD-L1 Expression in Head and Neck Squamous Cell Carcinoma Reveals Intra- and Inter-Sample Heterogeneity with Therapeutic Implications. Cancers (Basel) 2024; 16:2103. [PMID: 38893222 PMCID: PMC11171694 DOI: 10.3390/cancers16112103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Revised: 05/23/2024] [Accepted: 05/27/2024] [Indexed: 06/21/2024] Open
Abstract
For practical reasons, in many studies PD-L1 expression is measured by combined positive score (CPS) from a single tumor sample. This does not reflect the heterogeneity of PD-L1 expression in head and neck squamous cell carcinoma (HNSCC). We investigated the extent and relevance of PD-L1 expression heterogeneity in HNSCC analyzing primary tumors and recurrences (LRs), as well as metastases. Tumor tissue from 200 HNSCC patients was immunohistochemically stained for PD-L1 and analyzed using image-analysis software QuPath v3.4 with multiple specimens per patient. CPS was ≥20 in 25.6% of primary tumors. Intra-tumoral heterogeneity led to a therapeutically relevant underestimation of PD-L1 expression in 28.7% of patients, when only one specimen per patient was analyzed. Inter-tumoral differences in PD-L1 expression between primary tumors and lymph node metastasis (LNM) or LR occurred in 44.4% and 61.5% (CPS) and in 40.6% and 50% of cases (TPS). Overall survival was increased in patients with CPS ≥ 1 vs. CPS < 1 in primary tumors and LNM (hazard ratio: 0.46 and 0.35; p < 0.005); CPS in LR was not prognostic. Our analysis shows clinically relevant intra- and inter-sample heterogeneity of PD-L1 expression in HNSCC. To account for heterogeneity and improve patient selection for immunotherapy, multiple sample analyses should be performed, particularly in patients with CPS/TPS < 1.
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Affiliation(s)
- Eric Deuss
- Department of Otorhinolaryngology Head and Neck Surgery, University Hospital Essen, 45147 Essen, Germany (T.H.); (S.B.)
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center Mainz, 55131 Mainz, Germany
| | - Cornelius Kürten
- Department of Otorhinolaryngology Head and Neck Surgery, University Hospital Essen, 45147 Essen, Germany (T.H.); (S.B.)
| | - Lara Fehr
- Department of Otorhinolaryngology Head and Neck Surgery, University Hospital Essen, 45147 Essen, Germany (T.H.); (S.B.)
| | - Laura Kahl
- Department of Otorhinolaryngology Head and Neck Surgery, University Hospital Essen, 45147 Essen, Germany (T.H.); (S.B.)
| | - Stefanie Zimmer
- Institute of Pathology, University Medical Center Mainz, 55131 Mainz, Germany
| | - Julian Künzel
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center Mainz, 55131 Mainz, Germany
- Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Regensburg, 93053 Regensburg, Germany
| | - Roland H. Stauber
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center Mainz, 55131 Mainz, Germany
- Institute for Biotechnology, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China
| | - Stephan Lang
- Department of Otorhinolaryngology Head and Neck Surgery, University Hospital Essen, 45147 Essen, Germany (T.H.); (S.B.)
| | - Timon Hussain
- Department of Otorhinolaryngology Head and Neck Surgery, University Hospital Essen, 45147 Essen, Germany (T.H.); (S.B.)
- Department of Otorhinolaryngology, Klinikum Rechts der Isar, Technical University of Munich, 81675 Munich, Germany
| | - Sven Brandau
- Department of Otorhinolaryngology Head and Neck Surgery, University Hospital Essen, 45147 Essen, Germany (T.H.); (S.B.)
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Lee HP, Lee CC. Prognostic stratification of oropharyngeal cancer patients in a betel nut chewing and low HPV area. J Otolaryngol Head Neck Surg 2023; 52:27. [PMID: 37081578 PMCID: PMC10116661 DOI: 10.1186/s40463-023-00632-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Accepted: 02/23/2023] [Indexed: 04/22/2023] Open
Abstract
BACKGROUND This study aimed to establish a simple predictive model for oropharyngeal cancer (OPC) in an area with a relatively low prevalence of human papillomavirus (HPV) and frequent betel nut chewing. METHODS A total of 116 patients with OPC were recruited from the clinical research database of a referral cancer center between 2013 and 2018. Patient characteristics-including age, gender, tumor stage, differentiation, and treatment modality-were extracted from the database. Patients diagnosed after 2018 were staged using the 7th AJCC staging system to explore the impact of extra-nodal tumor extension (ENE) on survival. Immunohistochemical analysis was performed for p16, epidermal growth factor receptor (EGFR), p53, and programmed cell death ligand 1 (PD-L1). ENE status was evaluated by pathological analysis or radiological features. Primary outcome was disease-specific overall survival (OS). Univariate and multivariate Cox regression were used to establish a predictive model. RESULTS Mean age was 57.3 ± 9.9 years; 103 patients (88.8%) were male. P16 positive OPC was positively associated with higher PD-L1 and a tonsillar sub-site and negatively associated with betel nut chewing and cigarette smoking. In Cox regression, age, p16 status, EGFR, cT4, ENE, and cigarette smoking were significantly associated with OS. In survival tree analysis, cT stage was the most important risk stratification parameter, followed by EGFR expression and p16 status. Patients with cT4 stage or high EGFR were classified as the high-risk group and had poorest OS. CONCLUSIONS Due to the low prevalence of HPV and popularity of betel nut chewing in Asia, the relative importance of prognostic predictors for OPC are not identical to Western countries. Identification of significant prognostic biomarkers may improve treatment. Trial registration This study was registered and approved by the Institutional Review Board (IRB) of Kaohsiung Veterans General Hospital (VGHKS19-CT9-07; date of approval: Aug 9, 2019).
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Affiliation(s)
- Huai-Pao Lee
- Department of Pathology and Laboratory Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
- Department of Nursing, Meiho University, Pingtung, Taiwan
| | - Ching-Chih Lee
- Department of Otolaryngology, Head and Neck Surgery, Kaohsiung Veterans General Hospital, No.386, Dazhong 1St Rd., Zuoying Dist., Kaohsiung City, 81362, Taiwan (R.O.C.).
- School of Medicine, National Defense Medical Center, Taipei, Taiwan.
- Department of Otolaryngology, Head and Neck Surgery, Tri-Service General Hospital, Taipei, Taiwan.
- Institute of Hospital and Health Care Administration, National Yang Ming Chiao Tung University, Taipei, Taiwan.
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Gül D, Schweitzer A, Khamis A, Knauer SK, Ding GB, Freudelsperger L, Karampinis I, Strieth S, Hagemann J, Stauber RH. Impact of Secretion-Active Osteoblast-Specific Factor 2 in Promoting Progression and Metastasis of Head and Neck Cancer. Cancers (Basel) 2022; 14:2337. [PMID: 35565465 PMCID: PMC9106029 DOI: 10.3390/cancers14092337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 04/28/2022] [Accepted: 05/05/2022] [Indexed: 11/16/2022] Open
Abstract
Treatment success of head and neck cancer (HNC) is still hampered by tumor relapse due to metastases. Our study aimed to identify biomarkers by exploiting transcriptomics profiles of patient-matched metastases, primary tumors, and normal tissue mucosa as well as the TCGA HNC cohort data sets. Analyses identified osteoblast-specific factor 2 (OSF-2) as significantly overexpressed in lymph node metastases and primary tumors compared to normal tissue. High OSF-2 levels correlate with metastatic disease and reduced overall survival of predominantly HPV-negative HNC patients. No significant correlation was observed with tumor localization or therapy response. These findings were supported by the fact that OSF-2 expression was not elevated in cisplatin-resistant HNC cell lines. OSF-2 was strongly expressed in tumor-associated fibroblasts, suggesting a tumor microenvironment-promoting function. Molecular cloning and expression studies of OSF-2 variants from patients identified an evolutionary conserved bona fide protein secretion signal (1MIPFLPMFSLLLLLIVNPINA21). OSF-2 enhanced cell migration and cellular survival under stress conditions, which could be mimicked by the extracellular administration of recombinant protein. Here, OSF-2 executes its functions via ß1 integrin, resulting in the phosphorylation of PI3K and activation of the Akt/PKB signaling pathway. Collectively, we suggest OSF-2 as a potential prognostic biomarker and drug target, promoting metastases by supporting the tumor microenvironment and lymph node metastases survival rather than by enhancing primary tumor proliferation or therapy resistance.
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Affiliation(s)
- Désirée Gül
- Department of Otorhinolaryngology, Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (A.S.); (A.K.); (L.F.); (J.H.)
| | - Andrea Schweitzer
- Department of Otorhinolaryngology, Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (A.S.); (A.K.); (L.F.); (J.H.)
| | - Aya Khamis
- Department of Otorhinolaryngology, Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (A.S.); (A.K.); (L.F.); (J.H.)
- Oral Pathology Department, Faculty of Dentistry, Alexandria University, El Azareta, Alexandria, Egypt
| | - Shirley K. Knauer
- Institute for Molecular Biology, Centre for Medical Biotechnology (ZMB), University Duisburg-Essen, Universitätsstraße, 45117 Essen, Germany;
| | - Guo-Bin Ding
- Institute of Biotechnology, The Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Shanxi University, Taiyuan 030006, China;
| | - Laura Freudelsperger
- Department of Otorhinolaryngology, Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (A.S.); (A.K.); (L.F.); (J.H.)
| | - Ioannis Karampinis
- Academic Thoracic Center, University Medical Center Mainz, Johannes Gutenberg University Mainz, 55131 Mainz, Germany;
| | - Sebastian Strieth
- Department of Otorhinolaryngology, University Medical Center Bonn, 53127 Bonn, Germany;
| | - Jan Hagemann
- Department of Otorhinolaryngology, Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (A.S.); (A.K.); (L.F.); (J.H.)
| | - Roland H. Stauber
- Department of Otorhinolaryngology, Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (A.S.); (A.K.); (L.F.); (J.H.)
- Institute of Biotechnology, The Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Shanxi University, Taiyuan 030006, China;
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Gribko A, Stiefel J, Liebetanz L, Nagel SM, Künzel J, Wandrey M, Hagemann J, Stauber RH, Freese C, Gül D. IsoMAG-An Automated System for the Immunomagnetic Isolation of Squamous Cell Carcinoma-Derived Circulating Tumor Cells. Diagnostics (Basel) 2021; 11:2040. [PMID: 34829387 PMCID: PMC8623084 DOI: 10.3390/diagnostics11112040] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 10/29/2021] [Accepted: 11/01/2021] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND detailed information about circulating tumor cells (CTCs) as an indicator of therapy response and cancer metastasis is crucial not only for basic research but also for diagnostics and therapeutic approaches. Here, we showcase a newly developed IsoMAG IMS system with an optimized protocol for fully automated immunomagnetic enrichment of CTCs, also revealing rare CTC subpopulations. METHODS using different squamous cell carcinoma cell lines, we developed an isolation protocol exploiting highly efficient EpCAM-targeting magnetic beads for automated CTC enrichment by the IsoMAG IMS system. By FACS analysis, we analyzed white blood contamination usually preventing further downstream analysis of enriched cells. RESULTS 1 µm magnetic beads with tosyl-activated hydrophobic surface properties were found to be optimal for automated CTC enrichment. More than 86.5% and 95% of spiked cancer cells were recovered from both cell culture media or human blood employing our developed protocol. In addition, contamination with white blood cells was minimized to about 1200 cells starting from 7.5 mL blood. Finally, we showed that the system is applicable for HNSCC patient samples and characterized isolated CTCs by immunostaining using a panel of tumor markers. CONCLUSION Herein, we demonstrate that the IsoMAG system allows the detection and isolation of CTCs from HNSCC patient blood for disease monitoring in a fully-automated process with a significant leukocyte count reduction. Future developments seek to integrate the IsoMAG IMS system into an automated microfluidic-based isolation workflow to further facilitate single CTC detection also in clinical routine.
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Affiliation(s)
- Alena Gribko
- Department of Otorhinolaryngology, University Medical Center Mainz, Langenbeckstr. 1, 55131 Mainz, Germany; (A.G.); (S.M.N.); (M.W.); (J.H.); (R.H.S.)
| | - Janis Stiefel
- Fraunhofer Institute for Microengineering and Microsystems IMM, Carl-Zeiss-Str. 18-20, 55129 Mainz, Germany; (J.S.); (L.L.)
| | - Lana Liebetanz
- Fraunhofer Institute for Microengineering and Microsystems IMM, Carl-Zeiss-Str. 18-20, 55129 Mainz, Germany; (J.S.); (L.L.)
| | - Sophie Madeleine Nagel
- Department of Otorhinolaryngology, University Medical Center Mainz, Langenbeckstr. 1, 55131 Mainz, Germany; (A.G.); (S.M.N.); (M.W.); (J.H.); (R.H.S.)
| | - Julian Künzel
- Department of Otorhinolaryngology, University Hospital Regensburg, Franz-Josef-Strauß-Allee 11, 93053 Regensburg, Germany;
| | - Madita Wandrey
- Department of Otorhinolaryngology, University Medical Center Mainz, Langenbeckstr. 1, 55131 Mainz, Germany; (A.G.); (S.M.N.); (M.W.); (J.H.); (R.H.S.)
| | - Jan Hagemann
- Department of Otorhinolaryngology, University Medical Center Mainz, Langenbeckstr. 1, 55131 Mainz, Germany; (A.G.); (S.M.N.); (M.W.); (J.H.); (R.H.S.)
| | - Roland H. Stauber
- Department of Otorhinolaryngology, University Medical Center Mainz, Langenbeckstr. 1, 55131 Mainz, Germany; (A.G.); (S.M.N.); (M.W.); (J.H.); (R.H.S.)
| | - Christian Freese
- Fraunhofer Institute for Microengineering and Microsystems IMM, Carl-Zeiss-Str. 18-20, 55129 Mainz, Germany; (J.S.); (L.L.)
| | - Désirée Gül
- Department of Otorhinolaryngology, University Medical Center Mainz, Langenbeckstr. 1, 55131 Mainz, Germany; (A.G.); (S.M.N.); (M.W.); (J.H.); (R.H.S.)
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Siemer S, Fauth T, Scholz P, Al-Zamel Y, Khamis A, Gül D, Freudelsperger L, Wollenberg B, Becker S, Stauber RH, Hagemann J. Profiling Cisplatin Resistance in Head and Neck Cancer: A Critical Role of the VRAC Ion Channel for Chemoresistance. Cancers (Basel) 2021; 13:4831. [PMID: 34638315 PMCID: PMC8508519 DOI: 10.3390/cancers13194831] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 09/23/2021] [Accepted: 09/24/2021] [Indexed: 12/11/2022] Open
Abstract
Treatment success of head and neck cancers (HNSCC) is often hindered by tumor relapses due to therapy resistances. This study aimed at profiling cisplatin resistance mechanisms and identifying biomarkers potentially suitable as drug targets and for patient stratification. Bioinformatic analyses of suggested resistance factors in a cohort of 565 HNSCC patients identified the VRAC ion channel as a clinically relevant indicator for recurrent diseases following radiochemotherapy (p = 0.042). Other drug import/export transporters, such as CTR1, OCT1, or MRP1, were found to be less relevant. To experimentally verify VRAC's critical role for cisplatin resistance, we used CRISPR/Cas9 knockout resulting in cisplatin-resistant HNSCC cells, which could be resensitized by VRAC expression. Next-generation sequencing further underlined VRAC's importance and identified VRAC-regulated signaling networks, potentially also contributing to cisplatin resistance. CTR1, OCT1, or MRP1 did not contribute to increased cisplatin resistance. In addition to two-dimensional HNSCC models, three-dimensional tumor spheroid cultures confirmed VRAC's unique role for cisplatin sensitivity. Here, resistance correlated with DNA damage and downstream apoptosis. The cisplatin specificity of the identified VRAC pathway was verified by testing paclitaxel and doxorubicin. Our results were independently confirmed in naturally occurring, cisplatin-resistant HNSCC cancer cell models. Collectively, we here demonstrate VRAC's role for cisplatin resistance in HNSCC and its relevance as a potential drug target and/or prognostic biomarker for chemotherapy resistance.
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Affiliation(s)
- Svenja Siemer
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (S.S.); (Y.A.-Z.); (A.K.); (D.G.); (L.F.); (S.B.); (J.H.)
| | - Torsten Fauth
- BRAIN Biotech AG, 64673 Zwingenberg, Germany; (T.F.); (P.S.)
| | - Paul Scholz
- BRAIN Biotech AG, 64673 Zwingenberg, Germany; (T.F.); (P.S.)
| | - Yara Al-Zamel
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (S.S.); (Y.A.-Z.); (A.K.); (D.G.); (L.F.); (S.B.); (J.H.)
| | - Aya Khamis
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (S.S.); (Y.A.-Z.); (A.K.); (D.G.); (L.F.); (S.B.); (J.H.)
| | - Désirée Gül
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (S.S.); (Y.A.-Z.); (A.K.); (D.G.); (L.F.); (S.B.); (J.H.)
| | - Laura Freudelsperger
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (S.S.); (Y.A.-Z.); (A.K.); (D.G.); (L.F.); (S.B.); (J.H.)
| | - Barbara Wollenberg
- Department of Otorhinolaryngology Head and Neck Surgery, University Hospital Klinikum Rechts der Isar, 81675 Munich, Germany;
| | - Sven Becker
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (S.S.); (Y.A.-Z.); (A.K.); (D.G.); (L.F.); (S.B.); (J.H.)
- Department of Otorhinolaryngology, University Medical Center Tuebingen, 72076 Tuebingen, Germany
| | - Roland H. Stauber
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (S.S.); (Y.A.-Z.); (A.K.); (D.G.); (L.F.); (S.B.); (J.H.)
| | - Jan Hagemann
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, 55131 Mainz, Germany; (S.S.); (Y.A.-Z.); (A.K.); (D.G.); (L.F.); (S.B.); (J.H.)
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Gül D, Habtemichael N, Dietrich D, Dietrich J, Gößwein D, Khamis A, Deuss E, Künzel J, Schneider G, Strieth S, Stauber RH. Identification of cytokeratin24 as a tumor suppressor for the management of head and neck cancer. Biol Chem 2021; 403:869-890. [PMID: 34450690 DOI: 10.1515/hsz-2021-0287] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 07/28/2021] [Indexed: 12/19/2022]
Abstract
To improve management of head and neck squamous cell carcinoma patients, we need to increase our understanding of carcinogenesis, to identify biomarkers, and drug targets. This study aimed to identify novel biomarkers by providing transcriptomics profiles of matched primary tumors, lymph node metastasis, and non-malignant tissue of 20 HNSCC patients as well as by bioinformatic analyses of a TCGA HNSCC cohort, comprising 554 patients. We provide cancer cell signaling networks differentially expressed in tumors versus metastases, such as mesenchymal-epithelial transition, and structural integrity networks. As a proof of principle study, we exploited the data sets and performed functional analyses of a novel cytokeratin, cytokeratin24 (cKRT24), which had not been described as biomarker for tumors before. Survival analysis revealed that low cKRT24 expression correlated with poor overall survival in HNSCC. Experimentally, downregulation of cKRT24 in primary tumors, metastases, and HNSCC cell lines was verified on mRNA and protein level. Cloning and ectopic overexpression of cKRT24 not only affected viability and growth of HNSSC cell lines, but also inhibited tumor growth in murine xenograft studies. We conclude that cKRT24 functions as a tumor suppressor in HNSCC, and may serve as an additional prognostic biomarker and novel target to support current HNSCC treatments.
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Affiliation(s)
- Désirée Gül
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, D-55131Mainz, Germany
| | - Negusse Habtemichael
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, D-55131Mainz, Germany
| | - Dimo Dietrich
- Department of Otorhinolaryngology,University Medical Center Bonn, D-53127Bonn, Germany
| | - Jörn Dietrich
- Department of Otorhinolaryngology,University Medical Center Bonn, D-53127Bonn, Germany
| | - Dorothee Gößwein
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, D-55131Mainz, Germany
| | - Aya Khamis
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, D-55131Mainz, Germany
| | - Eric Deuss
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, D-55131Mainz, Germany.,Department of Otorhinolaryngology Head and Neck Surgery, University Hospital, D-45147Essen, Germany
| | - Julian Künzel
- Ear, Nose and Throat Department, University Hospital, D-93053Regensburg, Germany
| | - Günter Schneider
- Ear, Nose and Throat Department, University Hospital, D-93053Regensburg, Germany
| | - Sebastian Strieth
- Department of Otorhinolaryngology,University Medical Center Bonn, D-53127Bonn, Germany
| | - Roland H Stauber
- Department of Otorhinolaryngology Head and Neck Surgery, Molecular and Cellular Oncology, University Medical Center, D-55131Mainz, Germany
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