5'-Ectonucleotidase CD73/NT5E supports EGFR-mediated invasion of HPV-negative head and neck carcinoma cells.

BACKGROUND: Epithelial-to-mesenchymal transition (EMT) of malignant cells is a driving force of disease progression in human papillomavirus-negative (HPV-negative) head and neck squamous cell carcinomas (HNSCC). Sustained hyper-activation of epidermal growth factor receptor (EGFR) induces an invasion-promoting subtype of EMT (EGFR-EMT) characterized by a gene signature ("'EGFR-EMT_Signature'") comprising 5´-ectonucleotidase CD73. Generally, CD73 promotes immune evasion via adenosine (ADO) formation and associates with EMT and metastases. However, CD73 regulation through EGFR signaling remains under-explored and targeting options are amiss. METHODS: CD73 functions in EGFR-mediated tumor cell dissemination were addressed in 2D and 3D cellular models of migration and invasion. The novel antagonizing antibody 22E6 and therapeutic antibody Cetuximab served as inhibitors of CD73 and EGFR, respectively, in combinatorial treatment. Specificity for CD73 and its role as effector or regulator of EGFR-EMT were assessed upon CD73 knock-down and over-expression. CD73 correlation to tumor budding was studied in an in-house primary HNSCC cohort. Expression correlations, and prognostic and predictive values were analyzed using machine learning-based algorithms and Kaplan-Meier survival curves in single cell and bulk RNA sequencing datasets. RESULTS: CD73/NT5E is induced by the EGF/EGFR-EMT-axis and blocked by Cetuximab and MEK inhibitor. Inhibition of CD73 with the novel antagonizing antibody 22E6 specifically repressed EGFR-dependent migration and invasion of HNSCC cells in 2D. Cetuximab and 22E6 alone reduced local invasion in a 3D-model. Interestingly, combining inefficient low-dose concentrations of Cetuximab and 22E6 revealed highly potent in invasion inhibition, substantially reducing the functional IC50 of Cetuximab regarding local invasion. A role for CD73 as an effector of EGFR-EMT in local invasion was further supported by knock-down and over-expression experiments in vitro and by high expression in malignant cells budding from primary tumors. CD73 expression correlated with EGFR pathway activity, EMT, and partial EMT (p-EMT) in malignant single HNSCC cells and in large patient cohorts. Contrary to published data, CD73 was not a prognostic marker of overall survival (OS) in the TCGA-HNSCC cohort when patients were stratified for HPV-status. However, CD73 prognosticated OS of oral cavity carcinomas. Furthermore, CD73 expression levels correlated with response to Cetuximab in HPV-negative advanced, metastasized HNSCC patients. CONCLUSIONS: In sum, CD73 is an effector of EGF/EGFR-mediated local invasion and a potential therapeutic target and candidate predictive marker for advanced HPV-negative HNSCC.

Isolation and characterization of head and neck cancer-derived peritumoral and cancer-associated fibroblasts.

Introduction: Head and neck squamous cell carcinomas (HNSCC) are characterized by strong cellular and molecular heterogeneity and treatment resistance entailing poor survival. Besides cell-intrinsic properties, carcinoma cells receive important cues from non-malignant cells within the tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs) are a major component of the TME that impact on the molecular make-up of malignant cells and have a decisive function in tumor progression. However, the potential functionality of fibroblasts within tumor-adjacent, macroscopically normal tissue remains poorly explored. Methods: Here, we isolated primary peritumoral fibroblasts (PtFs) from macroscopically normal tissue in vicinity of primary human papillomavirus-negative and -positive oropharyngeal HNSCC and compared their phenotype and functionality with matched CAFs (n = 5 pairs) and with human oral fibroblasts (hOFs). Results: Expression patterns of CD90, CD73, CD105, smooth muscle actin, Vimentin, and S100A4 were comparable in PtFs, CAFs, and hOFs. Cell proliferation and doubling times of CAFs and PtFs were heterogeneous across patients (n =2 PtF>CAF; n = 1 CAF>PtF; n = 2 CAF=PtF) and reflected inferior growth than hOFs. Furthermore, PtFs displayed an reduced heterogeneity in cell size compared to matched CAFs, which were characterized by the presence of single large cells. Overall, conditioned supernatants from CAFs had more frequently growth-promoting effects on a panel of carcinoma cell lines of the upper aerodigestive tract carcinoma cell lines (Cal27, Cal33, FaDu, and Kyse30), whereas significant differences in migration-inducing effects demonstrated a higher potential of PtFs. Except for Kyse30, CAFs were significantly superior to hOFs in promoting proliferation, while PtFs induced stronger migration than hOFs in all carcinoma lines tested. Analysis of soluble factors demonstrated significantly increased VEGF-A production in CAFs (except in pat.8), and significantly increased PDGF-BB production in PtFs of two patients. Tube formation assays confirmed a significantly enhanced angiogenic potential of conditioned supernatants from CAFs compared to hOFs on human umbilical vascular endothelial cells (HUVECs) in vitro. Discussion: Hence, matched CAFs and PtFs present in HNSCC patients are heterogeneous in their proliferation-, migration-, and angiogenesis-promoting capacity. Despite this heterogeneity, CAFs induced stronger carcinoma cell proliferation and HUVEC tube formation overall, whereas PtFs promoted migration of tumor cells more strongly.

Primary cold atmospheric plasma combined with low dose cisplatin as a possible adjuvant combination therapy for HNSCC cells-an in-vitro study.

BACKGROUND: The aim of the present study was to examine the cytostatic effects of cold atmospheric plasma (CAP) on different head and neck squamous carcinoma (HNSCC) cell lines either in isolation or in combination with low dose cisplatin. The effect of CAP treatment was investigated by using three different HNSCC cell lines (chemo-resistant Cal 27, chemo-sensitive FaDu and OSC 19). MATERIALS AND METHOD: Cell lines were exposed to CAP treatment for 30, 60, 90, 120 and 180 s (s). Cisplatin was added concurrently (cc) or 24 h after CAP application (cs). Cell viability, DNA damage and apoptosis was evaluated by dye exclusion, MTT, alkaline microgel electrophoresis assay and Annexin V-Fit-C/PI respectively. RESULTS: In all cell lines, 120 s of CAP exposure resulted in a significant reduction of cell viability. DNA damage significantly increased after 60 s. Combined treatment of cells with CAP and low dose cisplatin showed additive effects. A possible sensitivity to cisplatin could be restored in Cal 27 cells by CAP application. CONCLUSION: CAP shows strong cytostatic effects in HNSCC cell lines that can be increased by concurrent cisplatin treatment, suggesting that CAP may enhance the therapeutic efficacy of low dose cisplatin.

Human Adipose-Derived Stem/Stromal Cells Promote Proliferation and Migration in Head and Neck Cancer Cells.

Human adipose-derived stem/stromal cells (ASCs) are increasingly used as auto-transplants in regenerative medicine to restore tissue defects or induce wound healing, especially in cancer patients. The impact of ASCs on squamous cell carcinoma of the upper aerodigestive tract (UAT) including head and neck and esophageal squamous cell carcinoma (HNSCC and ESCC) is not yet fully understood. ASCs were cultured from subcutaneous, abdominal lipoaspirates of five patients, who received auto-transplants to the head and neck. Supernatants were tested for paracrine effects in functional in vitro assays of proliferation of HNSCC tumor cell line FaDu and ESCC cell line Kyse30, and their cell migration/invasion capacities in Boyden chambers, in addition to endothelial tube formation assay using human umbilical vein endothelial cells (HUVECs). All ASC-derived supernatants enhanced proliferation of FaDu cells, invasive migration, and tube formation by HUVECs, compared to controls. Of five patients' lipoaspirates, ASC-derived supernatants of four patients increased proliferation and invasive migration in Kyse30 cells. The data suggests that ASCs can promote tumor cell proliferation, invasiveness, and neo-angiogenesis in these tumor cell lines of the UAT and HUVEC in a paracrine manner. Although clinical studies on the subject of oncological safety are still needed, these findings emphasize the importance of complete tumor removal before ASCs are used in the head and neck.

High-resolution spatiotemporal pHe and pO2 imaging in head and neck and oesophageal carcinoma cells.

BACKGROUND: pO2 and pH are physiological parameters relevant for different processes in health and disease, including wound healing and cancer progression. Head and neck squamous cell carcinomas (HNSCC) and oesophageal squamous cell carcinomas (ESCC) have a high rate of local recurrence that is partly related to treatment-resistant residual tumour cells. Hence, novel diagnostic tools are required to visualise potential residual tumour cells and thereby improve treatment outcome for HNSCC and ESCC patients. We developed a device to spatiotemporally measure oxygen consumption rates (OCR) and extracellular acidification rates (ECAR) to distinguish HNSCC and ESCC cells from healthy cells in vitro, exploiting general metabolic differences between cancer cells and healthy cells. METHODS: OCR and ECAR were measured via a newly developed device named STO2p-Q (SpatioTemporal O2 and pH Quantification) using the VisiSens technology based on ratiometric fluorescence imaging, facilitating spatiotemporal resolution. Results were confirmed using extracellular flux analyses (Seahorse technology). RESULTS: STO2p-Q is described and used to measure OCR and ECAR in HNSCC and ESCC cell lines and normal fibroblast and epithelial cells as components of the tumour microenvironment. OCR measurements showed differences amongst HNSCC and ESCC cell lines and between HNSCC/ESCC and normal cells, which on average had lower OCR than HNSCC/ESCC cells. Both OCR and ECAR measurements were independently verified using the Seahorse technology. Additionally, using STO2p-Q, HNSCC/ESCC, and normal cells could be spatially resolved with a resolution in the low millimetre range. CONCLUSIONS: We developed a method to spatiotemporally measure OCR and ECAR of cells, which has many potential in vitro applications and lays the foundation for the development of novel diagnostic tools for the detection of cancerous tissue in HNSCC and ESCC patients in vivo.

Cigarette Smoke Reduces the Efficacy of Cisplatin in Head and Neck Cancer Cells - Role of ABCG2.

BACKGROUND/AIM: We evaluated the influence of smoking on head and neck squamous cell carcinomas (HNSCC), which are in their majority tobacco-driven. Tobacco smoke is expected to influence the expression of ABCG2-transporters involved in multidrug resistance. The aim of the study was to evaluate the effect of cigarette smoke condensate (CSC) on ABCG2 expression on HNSCC cells, to demonstrate the adverse effects of cigarette smoke during anticancer treatment in vitro and to assess the prevalence of ABCG2 expression in HNSCC. MATERIALS AND METHODS: HNSCC cell lines were treated with CSC and basal and induced ABCG2 expression was examined. The impact of CSC on cellular viability/proliferation during cytotoxic drug treatment was also evaluated. ABCG2 expression levels in HNSCC were correlated with the smoking history of patients. RESULTS: HNSCC cells showed low basal ABCG2 expression. CSC treatment resulted in a threefold increase in the expression of ABCG2 and in resistance to cisplatin. Tumor samples of never smokers showed significantly higher ABCG2 expression compared to ever smokers. ABCG2 expression correlated with pack years of cigarette consumption. CONCLUSION: Tobacco consumption is linked to an inducible and increased ABCG2 protein expression and has an impact on drug resistance.

Molecular Characterization of Lipoaspirates Used in Regenerative Head and Neck Surgery.

IMPORTANCE: Adipose-derived mesenchymal stem cells (ASCs) have been used commonly in regenerative medicine and increasingly for head and neck surgical procedures. Lipoaspiration with centrifugation is purported to be a mild method for the extraction of ASCs used for autologous transplants to restore tissue defects or induce wound healing. The content of ASCs, their paracrine potential, and cellular potential in wound healing have not been explored for this method to our knowledge. OBJECTIVE: To evaluate the characteristics of lipoaspirates used in reconstructive head and neck surgical procedures with respect to wound healing. DESIGN, SETTING, AND PARTICIPANTS: This case series study included 15 patients who received autologous fat injections in the head and neck during surgical procedures at a tertiary referral center. The study was performed from October 2017 to November 2018, and data were analyzed from October 2017 to February 2019. MAIN OUTCOMES AND MEASURES: Excessive material of lipoaspirates from subcutaneous abdominal fatty tissue was examined. Cellular composition was analyzed using immunohistochemistry (IHC) and flow cytometry, and functionality was assessed through adipose, osteous, and chondral differentiation in vitro. Supernatants were tested for paracrine ASC functions in fibroblast wound-healing assays. Enzyme-linked immunosorbent assay measurement of tumor necrosis factor (TNF), vascular endothelial growth factor (VEGF), stromal-derived factor 1α (SDF-1α), and transforming growth factor ß3 (TGF-ß3) was performed. RESULTS: Among the 15 study patients (8 [53.3%] male; mean [SD] age at the time of surgery, 63.0 [2.8] years), the stromal vascular fraction (mean [SE], 53.3% [4.2%]) represented the largest fraction within the native lipoaspirates. The cultivated cells were positive for CD73 (mean [SE], 99.90% [0.07%]), CD90 (99.40% [0.32%]), and CD105 (88.54% [2.74%]); negative for CD34 (2.70% [0.45%]) and CD45 (1.74% [0.28%]) in flow cytometry; and negative for CD14 (10.56 [2.81] per 300 IHC score) and HLA-DR (6.89 [2.97] per 300 IHC score) in IHC staining; they differentiated into osteoblasts, adipocytes, and chondrocytes. The cultivated cells showed high expression of CD44 (mean [SE], 99.78% [0.08%]) and CD273 (82.56% [5.83%]). The supernatants were negative for TNF (not detectable) and SDF-1α (not detectable) and were positive for VEGF (mean [SE], 526.74 [149.84] pg/mL for explant supernatants; 528.26 [131.79] pg/106 per day for cell culture supernatants) and TGF-ß3 (mean [SE], 22.79 [3.49] pg/mL for explant supernatants; 7.97 [3.15] pg/106 per day for cell culture supernatants). Compared with control (25% or 50% mesenchymal stem cell medium), fibroblasts treated with ASC supernatant healed the scratch-induced wound faster (mean [SE]: control, 1.000 [0.160]; explant supernatant, 1.369 [0.070]; and passage 6 supernatant, 1.492 [0.094]). CONCLUSIONS AND RELEVANCE: The cells fulfilled the international accepted criteria for mesenchymal stem cells. The lipoaspirates contained ASCs that had the potential to multidifferentiate with proliferative and immune-modulating properties. The cytokine profile of the isolated ASCs had wound healing-promoting features. Lipoaspirates may have a regenerative potential and an application in head and neck surgery. LEVEL OF EVIDENCE: NA.

EpCAM ectodomain EpEX is a ligand of EGFR that counteracts EGF-mediated epithelial-mesenchymal transition through modulation of phospho-ERK1/2 in head and neck cancers.

Head and neck squamous cell carcinomas (HNSCCs) are characterized by outstanding molecular heterogeneity that results in severe therapy resistance and poor clinical outcome. Inter- and intratumoral heterogeneity in epithelial-mesenchymal transition (EMT) was recently revealed as a major parameter of poor clinical outcome. Here, we addressed the expression and function of the therapeutic target epidermal growth factor receptor (EGFR) and of the major determinant of epithelial differentiation epithelial cell adhesion molecule (EpCAM) in clinical samples and in vitro models of HNSCCs. We describe improved survival of EGFRlow/EpCAMhigh HNSCC patients (n = 180) and provide a molecular basis for the observed disparities in clinical outcome. EGF/EGFR have concentration-dependent dual capacities as inducers of proliferation and EMT through differential activation of the central molecular switch phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) and EMT transcription factors (EMT-TFs) Snail, zinc finger E-box-binding homeobox 1 (Zeb1), and Slug. Furthermore, soluble ectodomain of EpCAM (EpEX) was identified as a ligand of EGFR that activates pERK1/2 and phosphorylated AKT (pAKT) and induces EGFR-dependent proliferation but represses EGF-mediated EMT, Snail, Zeb1, and Slug activation and cell migration. EMT repression by EpEX is realized through competitive modulation of pERK1/2 activation strength and inhibition of EMT-TFs, which is reflected in levels of pERK1/2 and its target Slug in clinical samples. Accordingly, high expression of pERK1/2 and/or Slug predicted poor outcome of HNSCCs. Hence, EpEX is a ligand of EGFR that induces proliferation but counteracts EMT mediated by the EGF/EGFR/pERK1/2 axis. Therefore, the emerging EGFR/EpCAM molecular cross talk represents a promising target to improve patient-tailored adjuvant treatment of HNSCCs.

Therapy Testing in a Spheroid-based 3D Cell Culture Model for Head and Neck Squamous Cell Carcinoma.

Current treatment options for advanced and recurrent head and neck squamous cell carcinoma (HNSCC) enclose radiation and chemo-radiation approaches with or without surgery. While platinum-based chemotherapy regimens currently represent the gold standard in terms of efficacy and are given in the vast majority of cases, new chemotherapy regimens, namely immunotherapy are emerging. However, the response rates and therapy resistance mechanisms for either chemo regimen are hard to predict and remain insufficiently understood. Broad variations of chemo and radiation resistance mechanisms are known to date. This study describes the development of a standardized, high-throughput in vitro assay to assess HNSCC cell line's response to various therapy regimens, and hopefully on primary cells from individual patients as a future tool for personalized tumor therapy. The assay is designed to being integrated into the quality-controlled standard algorithm for HNSCC patients at our tertiary care center; however, this will be subject of future studies. Technical feasibility looks promising for primary cells from tumor biopsies from actual patients. Specimens are then transferred into the laboratory. Biopsies are mechanically separated followed by enzymatic digestion. Cells are then cultured in ultra-low adhesion cell culture vials that promote the reproducible, standardized and spontaneous formation of three-dimensional, spheroid-shaped cell conglomerates. Spheroids are then ready to be exposed to chemo-radiation protocols and immunotherapy protocols as needed. The final cell viability and spheroid size are indicators of therapy susceptibility and therefore could be drawn into consideration in future to assess the patients' likely therapy response. This model could be a valuable, cost-efficient tool towards personalized therapy for head and neck cancer.

Spheroid-based 3D Cell Cultures Enable Personalized Therapy Testing and Drug Discovery in Head and Neck Cancer.

BACKGROUND/AIM: Chemo-radiation currently serves as first-line therapy of advanced and recurrent head and neck cancer, while new chemotherapy regimens are emerging. However, response rates to any treatment are difficult to predict and underlie broad variation. This study shows the development of a standardized, high-throughput in vitro assay to assess patients' individual response to therapy regimens as a future tool for personalized tumor therapy. MATERIALS AND METHODS: Viability and proliferation analyses after chemo +/- radiation treatment of single spheroids (low adhesion plates/Hanging Drop (HD)) were generated from head and neck squamous cell carcinoma (HNSCC) cell lines and primary human cells from fresh tumor specimens. RESULTS: All cell lines showed reliable growth in all cell culture methods. The spheroids showed significant delay of growth and/or necrosis compared to control groups when exposed to current standard chemotherapeutic regimens. Single 3D spheroids ready for therapy susceptibility testing could be generated from actual tumor specimens after enzymatic and mechanical separation. CONCLUSION: In its current form, this single spheroid-based in vitro assay was able to test individual therapy susceptibility to current standard therapy regimens or, potentially, for testing new targeted drugs in HNSCC treatment. With recent discoveries regarding tumor heterogeneity and individual mutation status, a reliable assay is a prerequisite for personalized therapy in head and neck cancer.

Oral Cancer Reconstruction Using the Supraclavicular Artery Island Flap: Comparison to Free Radial Forearm Flap.

PURPOSE: To evaluate whether the pedicled supraclavicular artery island flap (SCAIF) is a sufficient alternative to the fasciocutaneous radial forearm free flap (RFFF) for oral reconstruction in cancer surgery. PATIENTS AND METHODS: The authors designed and implemented a retrospective cohort study composed of all consecutive patients who underwent head and neck reconstruction after cancer surgery at their tertiary university hospital from 2013 to 2016. Demographics and peri- and postoperative information were recorded and statistically analyzed. RESULTS: Of 83 patients who underwent head and neck reconstruction after cancer, 50 were identified as having stage III or IV squamous cell carcinoma of the oral cavity and oropharynx and underwent surgery and reconstruction with the SCAIF (n = 25) or the RFFF (n = 25). Total surgery time (411.0 vs 576.4 minutes; P < .001), flap elevation time (39.00 vs 93.78 minutes; P < .001), need for intensive care observation (32 vs 96%; P < .05), and rate of tracheotomy (64 vs 88%; P < .05) were significantly lower in the SCAIF group. There was no statistical difference in the postoperative complication rate or postoperative functional swallowing ability between the 2 groups. Total perioperative costs were significantly lower in patients who underwent reconstruction with the SCAIF (2,621.15 vs 4,453.77€; P < .01). CONCLUSION: The results of this study suggest that the SCAIF is a straightforward and reliable flap with shorter operative times and comparable outcomes compared with the RFFF.

Cytotoxic and Genotoxic Effects of Electronic Cigarette Liquids on Human Mucosal Tissue Cultures of the Oropharynx.

The popularity of electronic cigarettes (ECs) is rapidly growing and ECs are claimed to be an uncritically regarded alternative to conventional cigarettes. The mucosal tissue of the upper aerodigestive tract (UADT) is the first contact organ for xenobiotics such as liquids of ECs. The aim of this study is to investigate the bimolecular effects of e-liquids on human pharyngeal tissue cultures to evaluate whether e-liquids and their components present a risk factor for head and neck squamous cell carcinoma. Fresh tissue samples of healthy oropharyngeal mucosa were assembled into mucosal tissue cultures. Two fruit-flavored liquids (FLs), one tobacco-flavored liquid (TL) (all containing nicotine), and the corresponding base mixtures (free of nicotine and flavor) were used in three different dilutions. Cytotoxicity was assessed using the water-soluble tetrazolium-8 assay. DNA fragmentation was quantified using alkaline microgel electrophoresis. All liquids caused a significant reduction in cell viability. FLs especially showed a higher toxicity than TL. DNA fragmentation significantly increased by incubation with FL, whereas treatment with TL did not show serious DNA damage. E-liquids are cytotoxic to oropharyngeal tissue, and some liquids can induce relevant DNA damage. Thus, mutagenicity for mucosa of the UADT and e-liquids as risk factors for head and neck cancer cannot entirely be ruled out. Only the implementation of standards and regulations for liquid production and distribution can ensure a valid scientific investigation and assessment of carcinogenic potential of long-term EC use.

Chemoprevention by celecoxib and mutagen sensitivity of cyclin d1 in patients with oropharyngeal carcinoma.

UNLABELLED: The head and neck region is one of the most important locations predisposed for tobacco-associated cancer. Chemoprevention might offer a chance to decrease the risk for this type of disease. MATERIALS AND METHODS: Mini-organ cultures (MOC) of macroscopically-healthy pharyngeal tissues from 20 patients with oropharyngeal squamous cell carcinoma (SCC) and from 20 controls were employed in the study. MOC were firstly incubated with Celecoxib, and DNA damage was induced by incubation with Benz[a]pyren-7,8-diol-9,10-epoxid (BPDE), a major representative of tobacco-associated carcinogens. DNA damage was evaluated with the alkaline single-cell microgel electrophoresis (Comet assay). Furthermore, fragmentation of the cyclin D1 gene, a gene of special importance in head and neck carcinogenesis was examined by the Comet-FISH assay. Finally, the chemoprotective potential of Celecoxib was analyzed after incubation with MOC. RESULTS: As expected, BPDE caused significant DNA fragmentation in tumor compared to negative control tissues. No enhanced damage was observed in the cyclin D1 gene. DNA fragmentation was significantly reduced when MOC were incubated with Celecoxib in the tumor group. Surprisingly, these effects were also observed in the group without cancer of the oropharynx, although COX-2 is not expressed in macroscopically-healthy mucosa. CONCLUSION: Celecoxib showed considerable chemoprotective effeciency against BPDE in both groups and this effect seems to be independent of COX-2 expression. No evidence for higher mutagen sensitivity in the Cyclin D1 gene was observed.

Restoration of sensitivity in chemo-resistant glioma cells by cold atmospheric plasma.

Glioblastoma (GBM) is the most common and aggressive brain tumor in adults. Despite multimodal treatments including surgery, chemotherapy and radiotherapy the prognosis remains poor and relapse occurs regularly. The alkylating agent temozolomide (TMZ) has been shown to improve the overall survival in patients with malignant gliomas, especially in tumors with methylated promoter of the O6-methylguanine-DNA-methyltransferase (MGMT) gene. However, intrinsic and acquired resistance towards TMZ makes it crucial to find new therapeutic strategies aimed at improving the prognosis of patients suffering from malignant gliomas. Cold atmospheric plasma is a new auspicious candidate in cancer treatment. In the present study we demonstrate the anti-cancer properties of different dosages of cold atmospheric plasma (CAP) both in TMZ-sensitive and TMZ-resistant cells by proliferation assay, immunoblotting, cell cycle analysis, and clonogenicity assay. Importantly, CAP treatment restored the responsiveness of resistant glioma cells towards TMZ therapy. Concomitant treatment with CAP and TMZ led to inhibition of cell growth and cell cycle arrest, thus CAP might be a promising candidate for combination therapy especially for patients suffering from GBMs showing an unfavorable MGMT status and TMZ resistance.

Reduction of DNA damage by curcumin and celecoxib in epithelial cell cultures of the oropharynx after incubation with tobacco smoke condensate.

BACKGROUND: Tobacco smoke, as the major risk factor for the development of squamous cell cancer of the head and neck (HNSCC), contains various xenobiotics, such as polycyclic aromatic hydrocarbons, nitrosamines, aromatic amines and phenols. Chemoprevention either by artificial agents such as celecoxib, or natural compounds such as curcumin, might offer a chance to reduce the risk of developing malignant transformation. MATERIALS AND METHODS: In order to evaluate the DNA-damaging effects of smoke condensate towards human mucosa cells of the oropharynx, mini organ cultures (MOC) of macroscopically healthy pharyngeal tissue of 40 patients with oropharyngeal SCC were used. After incubation with smoke condensate DNA damage was evaluated with the alkaline single-cell microgel electrophoresis (comet assay). The chemoprotective potential of curcumin and celecoxib was analyzed after their incubation with the condensate-treated MOCs. As DNA-damaging and chemopreventive effects might not be equally distributed over the whole DNA, fragmentation of the epithelial growth factor receptor (EGFR) gene was additionally examined by Comet fluorescence in situ hybridization (FISH). RESULTS: As expected, tobacco smoke condensate caused significant DNA fragmentation compared to the negative control. No enhanced damage was observed on the EGFR gene. DNA fragmentation was significantly reduced when MOCs were incubated with celecoxib (p ≤ 0.001) and with curcumin (p ≤ 0.001). CONCLUSION: Both celecoxib and curcumin showed considerable chemoprotective effects towards the impact of smoke condensate. No evidence was found for higher susceptibility to damage in the EGFR gene.

DNA repair and mutagen sensitivity of epithelial cells and lymphocytes in oropharyngeal cancer.

Tobacco-associated nitrosamines are known carcinogens causing DNA damage in epithelial cells of the head and neck. A matched case-control study was performed to evaluate the sensitivity of patients with squamous cell cancer (SCC) of the oropharynx, and controls to tobacco-associated nitrosamines. Quantitative DNA repair was evaluated following a period of 15 and 30 min. Fresh biopsies from 100 male donors of macroscopically healthy oropharyngeal cells and lymphocytes (50 SCC patients and 50 controls) were incubated with N-nitrosodiethylamine (NDEA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) or N-nitrosonornicotine (NNN). DNA damage in epithelial cells and lymphocytes was assessed using the comet assay. Following incubation with NDEA, cells underwent a period of DNA repair. All of the nitrosamines caused equivalent genotoxic damage in mucosal cells and lymphocytes of the two groups. Lymphocyte DNA repair capacity in the control group (26.8 and 37.1% after 15 and 30 min) was comparable to the tumor group (23.6 and 40.6%). However, epithelial cell DNA repair capacity of carcinoma patients was significantly reduced to 17.1% (15 min) and 23% (30 min) compared to the DNA repair of the control group (36.2%, 15 min and 46.0%, 30 min). Mutagen sensitivity was comparable in patients and controls. Thus, reduced epithelial cell DNA repair capacity of tumor patients is a possible endogenous risk factor for the development of head and neck squamous cell cancer.

EGFR and P-GP expression in oropharyngeal mucosa in relation to smoking.

BACKGROUND: About two thirds of head and neck squamous cell carcinoma (HNSCC) cases are attributable to heavy tobacco and alcohol consumption. Tobacco carcinogens cause cellular damage in large areas of the upper aerodigestive tract mucosa and contribute to distinct molecular changes, such as increasing levels of epidermal growth factor receptor (EGFR), during carcinogenesis. P-Glycoprotein (P-GP) is a multidrug-resistance transporter protein capable of extruding not only cytotoxic drugs, but also certain tobacco-related carcinogens. EGFR plays a major role in the transcriptional and functional regulation of P-GP and previous studies in our laboratory showed that stimulation of EGFR protection protected oropharyngeal cells from a carcinogen that is substrate of P-GP. Therefore, we evaluated expression levels of EGFR and P-GP and looked for a possible association with the smoking status of patients. MATERIALS AND METHODS: Tissue cultures of healthy oropharyngeal mucosa were produced from 30 patients undergoing surgery at our Department. Expression levels of EGFR on P-GP were determined by immunohistochemical staining. To evaluate possible influences of EGFR on P-GP expression, we stimulated the receptor using transforming growth factor alpha (TGF-α) for 24, 48 and 72 h. RESULTS: Current and former smokers had significantly higher EGFR/P-GP levels than never smokers. While EGFR expression was detected in almost all samples, P-GP expression was largely restricted to former and current smokers. TGF-α had no detectable effect on EGFR/P-GP levels. CONCLUSION: These results show an association between tobacco use and levels of both proteins. Since both these proteins are involved in drug resistance of head and neck cancer, this study might help to further understand the differences in response to therapy and prognosis of tobacco-related and -unrelated cancer.

The impact of EGFR stimulation and inhibition on BPDE induced DNA fragmentation in oral/oropharyngeal mucosa in vitro.

Still, the vast majority of head and neck squamous cell carcinoma (HNSCC) can be linked to the "traditional" risk factors tobacco smoke and alcohol consumption. These tumors are believed to be the results of multiple years of carcinogenic impact on upper aerodigestive tract mucosa. The frequent observation, that one patient suffers from several synchronous cancers, multiple local recurrences, and second primary tumors led to the concept of field cancerization, first introduced by Slaughter and colleagues in 1953. As underlying molecular events, genetic instability, loss of heterozygosity, amplification, deletion, up- and down-regulation of oncogenes and/or tumor suppressor genes were revealed. One of the best studied oncogenic features of head and neck carcinogenesis are high expression levels of epidermal growth factor receptor (EGFR). Enhanced expression of the receptor was detected in histologically normal mucosa from HNSCC patients and increasing levels during the progress from hyperplasia to dysplastic lesion and invasive carcinoma were demonstrated. Whereas nearly all of our knowledge about EGFR biology in HNSCC is based on preclinical and clinical studies investigating receptor inhibitors, little is known about cause and function of EGFR in premalignant mucosa. In this study we show, that EGFR stimulation significantly decreases carcinogen induced DNA damage in normal mucosa from HNSCC patients and that this effect is completely abrogated adding an anti-EGFR antibody before stimulation, while there was no effect in non-tumor controls. The effect of EGFR inhibition was contrary. In non-tumor controls, blocking the receptor with an antibody significantly decreased DNA damage, whereas in cases no effect was seen. Our results indicate an important role of the receptor during chemical carcinogenesis. On the basis of this study we suppose, that increasing EGFR levels during head and neck carcinogenesis can be interpreted as a physiological response to permanent carcinogen impact on the mucosa.

Transforming growth factor alpha stimulation of mucosal tissue cultures from head and neck squamous cell carcinoma patients increases chemoresistance to cisplatin.

The monoclonal epidermal growth factor receptor (EGFR) antibody cetuximab (Erbitux) was recently approved by the European Medicines Agency for the treatment of recurrent and/or metastatic head and neck squamous cell carcinoma (HNSCC) in combination with a platinum-based chemotherapy. Since the antibody has only a limited effect as a monotherapy, possible explanations for the synergistic effect with cisplatin are enhanced antibody-dependent cytoxicity and increased sensitivity to the drug. Most of our knowledge of EGFR biology in HNSCC is based on studies using EGFR inhibitors and/or antibodies. Our study was designed to evaluate the impact of EGFR stimulation on cisplatin-induced DNA damage. Therefore, tissue cultures were produced of tumor-free oropharyngeal mucosa biopsies of HNSCC patients and controls. In a previous study, overexpression of EGFR in tissue cultures from tumor patients compared to controls was confirmed by immunohistochemical staining. Twenty-four-hour stimulation of tissue cultures with transforming growth factor alpha (TGF-alpha), a specific EGFR ligand, resulted in a reduction of cisplatin-induced DNA damage by 35% in cases, whereas in controls TGF-alpha had no effect. This reflects a statistically significant increase in cellular chemoresistance to cisplatin following TGF-alpha stimulation and helps to further understand effects of EGFR antisense therapy in combination with chemotherapy.