Biomedical subjects

Thomas K Hoffmann

Publications and source records attributed to Thomas K Hoffmann.

At least 19 recordsLinked to original sources

PubMed2025

Identification of marginal zone B cells in head and neck cancer with immunomodulatory characteristics.

INTRODUCTION: Recently we observed high numbers of marginal zone B cells (MZBs) within murine head and neck squamous cell carcinoma (HNSCC) with immunosuppressive potential. To date, MZBs have not been linked to tumor development or tumor prevention. OBJECTIVES: Based on our previous findings the present study aimed to validate the presence of MZB in HNSCC and to investigate their possible implications in tumorigenesis and prognosis. METHODS: Flow cytometry was used to uncover MZB within tumors and blood of HNSCC patients. A single-cell RNA sequencing cohort of 118 HNSCC patients across different disease stages and 6 healthy donors (HDs) was compiled. Comparative transcriptomic profiling of B lymphocytes between HNSCC and HDs were performed. Downstream analysis, such as pathway enrichment, cell-cell communication, pseudotime trajectory inference, survival correlation, and spatial transcriptomics were applied. RESULTS: Two MZB subsets were revealed in tissues and blood of HNSCC patients and HDs. The tumor-associated MZBs were featured with hypoxia stress and viral-related hallmark genes. MZB-2, characterized by elevated expression of activation markers and immune-regulatory genes, displayed strong interactions with CD4+ T cells and antigen-presenting cells. These interactions were supported by costimulatory signals in HDs but were absent in HNSCC patients. Co-localization of MZB-2, germinal center B cell (GCB), and CD4+ follicular helper T cell (Tfh) was detected in HNSCC, suggesting the presence of an intratumoral MZB-Tfh-GCB axis. Clinically, MZB-2 abundance was associated with favorable prognosis in early-stage HNSCC, but not in advanced disease. Immunosuppressive gene signatures were not exclusive to MZBs, indicating that they do not represent a purely regulatory B cell phenotype. CONCLUSION: Our findings demonstrate an immunomodulatory role of MZBs in tumor immunity, balancing antigen presentation, cytokine signaling, and immune suppression. The association of MZB-2 with improved prognosis in early-stage HNSCC highlights its potential as a beneficial regulator of antitumor immunity during early tumor progression.

Humans↗

PubMed2007

Aberrant cytokine expression in serum of patients with adenoid cystic carcinoma and squamous cell carcinoma of the head and neck.

BACKGROUND: Squamous cell carcinoma (SCC) and adenoid cystic carcinoma (ACC) represent 2 clinically important subtypes of head and neck cancer. Our objective was to characterize and compare cytokine profiles in the systemic circulation of patients with SCC and ACC. METHODS: Multiplex analysis of 10 different cytokines (interleukin [IL]-1beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, granulocyte-macrophage colony-stimulating factor [GM-CSF], interferon [IFN]-gamma, and tumor necrosis factor [TNF]-alpha) in the serum of patients with SCC (n = 20) and ACC (n = 20) and healthy controls (n = 20) was performed using the Luminex fluorescent-bead technology. RESULTS: Patients with SCC as well as patients with ACC showed an altered cytokine profile compared with healthy individuals. In patients with SCC, significantly elevated serum levels of the proinflammatory cytokines, IL-6 and IL-8, were observed. In patients with ACC, IL-8 serum levels were significantly elevated, and IL-6 serum levels were only increased in a subset of patients. CONCLUSIONS: A similar serum cytokine profile, with the predominance of proinflammatory cytokines, was observed in patients with SCC and ACC. The newly defined cytokine profile in ACC patients may form the basis for future investigations to explore the role of cytokines in ACC tumor progression and their potential value as predictive biomarkers.

Adult↗

PubMed2006

The effect of relaxin on the oxytocin receptor in human uterine smooth muscle cells.

EXPERIMENTAL OBJECTIVES: Activation of the oxytocin receptor (OTR) induces phospholipase C induced PIP(2) turnover in the human uterus. Relaxin (RLX), a polypeptide hormone produced in the corpus luteum of pregnancy as well as in the placenta and decidua inhibits PIP(2) turnover and subsequent signaling in human myometrium. The purpose of this study was to evaluate a possible effect of RLX on OTR regulation in human uterine smooth muscle cells. Primary cultures of myometrium from term pregnant women undergoing elective caesarean section were incubated for different time periods (0-96 h) and with different concentrations of RLX [10 pg/ml-20 microg/ml]. The effects on OTR binding, mRNA and protein expression were evaluated by means of (125)I-OVT binding assay, RT-PCR and flow cytometry. RESULTS: Prolonged RLX incubation was able to inhibit 30-40% of OTR binding while binding affinity remained unchanged. Oxytocin receptor mRNA and protein expression were down regulated by RLX about 50% and 35% respectively. CONCLUSION: We report for the first time an effect of RLX on OTR regulation in human uterine myometrial cells. The above results indicate that high local uterine RLX concentrations may be involved in uterine quiescence during human pregnancy by down regulating the OTR.

Cells, Cultured↗

PubMed2006

Chemokine receptors in head and neck cancer: association with metastatic spread and regulation during chemotherapy.

Head and neck carcinomas are histologically and clinically heterogeneous. While squamous cell carcinomas (SCC) are characterized by lymphogenous spread, adenoid cystic carcinomas (ACC) disseminate preferentially hematogenously. To study cellular and molecular mechanisms of organ-specific metastasis, we used SCC and ACC cell lines and tumor tissues, obtained from patients with primary or metastatic disease. Comprehensive analysis at the mRNA and protein level of human chemokine receptors showed that SCC and ACC cells exhibited distinct and nonrandom expression profiles for these receptors. SCC predominantly expressed receptors for chemokines homeostatically expressed in lymph nodes, including CC chemokine receptor (CCR) 7 and CXC chemokine receptor (CXCR)5. No difference in expression of chemokine receptors was seen in primary SCC and corresponding lymph node metastases. In contrast to SCC, ACC cells primarily expressed CXCR4. In chemotaxis assays, ACC cells were responsive to CXCL12, the ligand for CXCR4. Exposure of ACC cells to cisplatin resulted in upregulation of CXCR4 on the cell surface, which was repressed by the transcriptional inhibitor, alpha-amanitin. Treatment of ACC cells with CXCL12 resulted in the activation of Akt and ERK1/2 pathways. Furthermore, CXCL12 suppressed the rate of apoptosis induced by cisplatin in ACC cells, suggesting that signaling via CXCR4 may be part of a tumor cell survival program. Discrimination of the chemokine receptor profile in SCC and ACC in vitro and in tissues provided insights into their distinct biologic and clinical characteristics as well as indications that chemokine receptors might serve as future therapeutic targets in these malignancies.

Antineoplastic Agents↗

PubMed2006

T cells specific for HPV16 E7 epitopes in patients with squamous cell carcinoma of the oropharynx.

Squamous cell carcinomas of the oropharynx (SCCO) are often infected with oncogenic human papilloma virus (HPV) subtype 16. To determine the frequency of T cells specific for human leukocyte antigen (HLA)-A2.1 restricted HPV16 E7 protein-derived epitopes, tetramer analysis was performed using peripheral blood lymphocytes of 20 HLA-A2.1+ patients and 20 HLA-A2.1+ healthy individuals. Tetramers specific for 3 HPV16 peptides (E711-20, E782-90 and E786-93), an influenza matrix peptide (a model recall antigen) or an HIV reverse transcriptase peptide (a model novel antigen) were used in multicolor flow analysis. The HPV-specific T-cell frequencies were correlated with the HPV16 E7 and p16 status in tumor sections. In vitro stimulation (IVS) with autologous dendritic cells (DC) pulsed with HPV16 E7 epitopes was performed to demonstrate proliferation and antitumor activity of the HPV-responsive T cells. Frequencies of CD8+ T cells specific for HPV16 E7 peptides were not significantly different in patients with SCCO relative to normal donors. However, patients with tumors expressing HPV16 E7 (60%) and p16 (50%) had an increased frequency (p<0.05) of T cells specific for the E711-20 epitope compared to those with tumors negative for both markers. HPV16 E711-20 and HPV16 E786-93 specific T cells were expandable upon IVS with cognate peptide-pulsed DC and were reactive against peptide-pulsed targets or, in case of the E711-20 epitope-specific T cells, against HPV16 E7 expressing CaSki cell line. Thus, in patients with HPV16+ SCCO, precursor T cells specific for E711-20 epitope are present (1/3,947) in the circulation, are responsive to stimulation with the cognate viral peptide and recognize in vitro HPV16 E7+ tumor cells. Further studies have to elucidate why those T cells are unable to eliminate the tumor in vivo and this might also allow for finding potential strategies that will increase the chances of developing a future HPV-based vaccine in patients with SCCO.

Antigens, Viral↗

PubMed2006

Gamma-delta T-cells in patients with squamous cell carcinoma of the head and neck.

In our attempt to characterize a general immune-suppression found in patients with squamous cell carcinoma of the head and neck (SCCHN) we now focused on a subset of CD3 lymphocytes described as gamma/delta-T-cells, a cell type with potential relevance in non-MHC restricted anti-tumor immune responses. Peripheral blood of 33 SCCHN patients and 33 age-matched controls (CON) was evaluated for the frequency of gamma/delta-T-cells among CD3+ T-cells and their onset of apoptosis (Annexin V binding) by multicolor flow cytometry. Results were correlated with clinical parameters. Patients with SCCHN had a significantly higher proportion of gamma/delta-T-cells compared to healthy controls (4.4+/-0.4% for SCCHN vs. 3.0+/-0.3% for CON, p=0.01). However, this increase was not paralleled with a difference in the onset of apoptosis if compared to CON. There was also no correlation between the proportion of gamma/delta-T-cells and tumor stage. However, a significantly higher proportion of gamma/delta-T-cells was found in patients with recurrent or metachronous second primary SCCHN (6.0+/-1.0%) if compared to the other SCCHN (3.8+/-0.4%, p=0.02). In a follow up 3-6 months post-treatment patients showed a decrease of gamma/delta-T-cells among CD3+cells (2.7+/-0.4%, n=4) if they were operated only and an increase if primary radio-chemotherapy (6.7+/-1.7%, n=8) or a combination of operation plus radio-chemotherapy (6.8+/-2.3%, n=3) was applied. Furthermore, patients receiving palliative treatment including radio-chemotherapy had highest values of gamma/delta-T-cells (9.1+/-2.7%, n=4) overall implicating that the treatment modality significantly influences the proportion of gamma/delta-T-cells. Since patients with SCCHN, particularly those with recurrent or second primary disease after treatment, had a higher proportion of gamma/delta-T-cells without signs of a reduced onset of apoptosis this could be due to an increased de novo generation. The current study implies that increased frequencies of gamma/delta-T-cells in patients with SCCHN may not only be the result of tumor-host interactions but the consequence of applied treatment modalities.

Aged↗

PubMed2006

IL-31: a new link between T cells and pruritus in atopic skin inflammation.

BACKGROUND: IL-31 is a novel T-cell-derived cytokine that induces severe pruritus and dermatitis in transgenic mice, and signals through a heterodimeric receptor composed of IL-31 receptor A and oncostatin M receptor. OBJECTIVE: To investigate the role of human IL-31 in pruritic and nonpruritic inflammatory skin diseases. METHODS: The expression of IL-31 was analyzed by quantitative real-time PCR in skin samples of healthy individuals and patients with chronic inflammatory skin diseases. Moreover, IL-31 expression was analyzed in nonlesional skin of atopic dermatitis patients after allergen or superantigen exposure, as well as in stimulated leukocytes. The tissue distribution of the IL-31 receptor heterodimer was investigated by DNA microarray analysis. RESULTS: IL-31 was significantly overexpressed in pruritic atopic compared with nonpruritic psoriatic skin inflammation. Highest IL-31 levels were detected in prurigo nodularis, one of the most pruritic forms of chronic skin inflammation. In vivo, staphylococcal superantigen rapidly induced IL-31 expression in atopic individuals. In vitro, staphylococcal enterotoxin B but not viruses or T(H)1 and T(H)2 cytokines induced IL-31 in leukocytes. In patients with atopic dermatitis, activated leukocytes expressed significantly higher IL-31 levels compared with control subjects. IL-31 receptor A showed most abundant expression in dorsal root ganglia representing the site where the cell bodies of cutaneous sensory neurons reside. CONCLUSION: Our findings provide a new link among staphylococcal colonization, subsequent T-cell recruitment/activation, and pruritus induction in patients with atopic dermatitis. Taken together, these findings show that IL-31 may represent a novel target for antipruritic drug development.

Dermatitis, Atopic↗

PubMed2006

Evaluation and management of angioedema of the head and neck.

PURPOSE OF REVIEW: Sudden occurrence of subcutaneous or submucosal swelling, the so-called angioedema, is an established and potentially life-threatening condition. Several forms of angioedema show a great variety of tissue localizations and different underlying mechanisms such as genetic mutations, allergic reactions and nonallergic reactions exist. Unfortunately, angioedema is often unrecognized and/or incorrectly treated. To change this situation, a better understanding of angioedema and possible therapeutic approaches appears necessary. RECENT FINDINGS: Recent investigations have shed new light on the pathomechanism of nonallergic drug-induced angioedema and new therapeutic options targeting the kallikrein-kinin system have become available for patients in clinical trials. Furthermore, extensive clinical evaluations of commonly used inhibitors of the renin-angiotensin system have provided reliable data on the incidence of angioedema induced by these drugs. Accordingly, several thousand patients worldwide experience severe fatal attacks although timely medical care would have saved their lives. SUMMARY: Current data suggest that the nonapetide bradykinin plays a crucial role in the pathogenesis of most forms of nonallergic angioedema, while histamine acts as the main biogenic mediator in allergic angioedema. Thus, correct diagnosis is crucial for effective treatment. Standard antiallergic drugs such as glucocorticoids and antihistamines are most probably ineffective in nonallergic angioedema forms.

Angioedema↗

PubMed2005

Unpulsed dendritic cells induce broadly applicable anti-tumor immunity in mice.

The discovery of dendritic cells (DC) as professional antigen presenting cells has opened up new possibilities for their use in the development of cancer vaccines. Here we show that unpulsed BM-derived CD11c+CD8alpha-DC administered s.c. to mice enhanced their resistance to subsequent lethal tumor challenges. The tumor resistance-inducing activity of unpulsed DC was dependent on their maturation status, involved CD4+ and CD8+ T cell activities, and was abrogated by pulsing with an irrelevant class I MHC-restricted peptide. Although the BALB/c Meth A tumor system was employed extensively to demonstrate the tumor resistance inducing activity of unpulsed DC, the immunogenicity of this vaccine was evident in other inbred strains of mice against a variety of syngeneic tumors. The broad anti-tumor responses induced by unpulsed DC appears to be due to their capacity to present "self" tumor-associated antigens, such as the H2-Kd-restricted, wild type sequence p53(232-240) peptide. These findings highlight the potential broad applicability of unpulsed DC as a tumor vaccine.

Animals↗

PubMed2005

p53 as an immunotherapeutic target in head and neck cancer.

Squamous cell carcinomas of the head and neck (HNSCCs) are characterized by a high frequency of mutations in the p53 gene often leading to p53 protein accumulation. Since accumulation of p53 is associated with enhanced presentation of wild-type sequence (wt) p53 peptides to immune cells, the development of ' pan' vaccines against HNSCC has focused on wt p53 epitopes. We used the HLA-A2.1-restricted wt p53 264-272 epitope pulsed on autologous dendritic cells to generate cytotoxic T lymphocytes (CTLs) ex vivo from circulating precursor T cells of HLA-A2.1+ patients with HNSCC. CTLs specific for the wt p53 264-272 peptide were generated from leukocytes obtained from a cohort of patients with HNSCC (group A). Paradoxically, none of those patients had tumors which adequately presented the epitope, i.e. accumulated p53. In contrast, patients who did not generate CTLs (group B) had tumors which accumulated altered p53 and potentially could present the p53 264-272 epitope. When p53 264-272-specific T cells were directly enumerated in the peripheral circulation of patients with HNSCC using tetrameric p53 264-272/HLA-A2.1 complexes by multicolor flow cytometry, group A had high and group B low percentages of tetramer+ CD3+ CD8+ T cells. These findings suggested that in vivo p53-specific CTLs in group A might play a role in the elimination of tumor cells expressing the p53 264-272 epitope ('immunoselection'), leading to the outgrowth of 'epitope loss' tumor cells. On the other hand, precursor CTLs specific for the wt p53 264-272 peptide in group B are unresponsive to the p53 antigen. Unresponsiveness of CTLs specific for the wt p53264-272 peptide detected in group B could be reversed by using more immunogenic variant peptides of the p53 264-272 epitope. In vivo, immunoselection of tumors which become resistant to anti-p53 immune responses has important implications for future p53-based vaccination strategies. It calls for modified approaches, in which altered peptide variants of the wt sequence p53 264-272 epitope are used in a vaccine in order to overcome unresponsiveness of T lymphocytes to the native epitope.

Cancer Vaccines↗

PubMed2004

Targeting the immune system: novel therapeutic approaches in squamous cell carcinoma of the head and neck.

Despite advances in surgery, radiotherapy, and chemotherapy, the overall survival rates for patients with squamous cell carcinoma of the head and neck (SCCHN) have not changed over the last decades. Clearly, novel therapeutic strategies are needed for this cancer, which is highly immunosuppressive. Therefore, biologic therapies able to induce and/or up-regulate antitumor immune responses could represent a complementary approach to conventional treatments. Because patients with SCCHN are frequently immunocompromised due to the elimination or dysfunction of critical effector cells of the immune system, it might be necessary to restore these immune functions to allow for the generation of more effective antitumor host responses. Simultaneously, to prevent tumor escape, it might be necessary to alter attributes of the malignant cells. The present review summarizes recent advances in the field of immunotherapy of SCCHN, including techniques of nonspecific immune stimulation, the use of monoclonal antibodies, advances in adoptive immunotherapy and genetic engineering, as well as anticancer vaccines. These biologic therapies, alone or in combination with conventional treatment, are likely to develop into useful future treatment options for patients with SCCHN.

Adjuvants, Immunologic↗

PubMed2003

Direct visualization of antigen-specific T cells using peptide-MHC-class I tetrameric complexes.

Peptide-major histocompatibility complexes (MHC) class I tetrameric complexes ("tetramers") are proving invaluable as fluorescent reagents for enumeration, characterization, and isolation of peptide-specific T cells and have afforded many advantages over previous techniques, particularly the ability to directly quantify and phenotype antigen-specific T cells with minimal in vitro manipulation. Recently, various technical peculiarities of tetramers have led to modifications within this important immunoassay. The current manuscript details potential pitfalls and provides guidance for interpretation of results.

Epitopes, T-Lymphocyte↗

PubMed2002

Frequencies of tetramer+ T cells specific for the wild-type sequence p53(264-272) peptide in the circulation of patients with head and neck cancer.

Immunization with wild-type sequence (wt) p53 epitopes represents a novel therapeutic strategy for cancer patients with tumors accumulating mutant p53. To evaluate usefulness of p53-derived peptides as future cancer vaccines, frequencies of wt p53(264-272) peptide-specific CD8+ T cells were determined in the peripheral circulation of patients with squamous cell carcinoma of the head and neck (SCCHN). T cells of 30 HLA-A2.1+ patients and 31 HLA-A2.1+ healthy individuals were evaluated by multicolor flow cytometry analysis using peptide-HLA-A2.1 complexes (tetramers). T cells specific for an influenza matrix peptide (a model recall antigen) or an HIV reverse transcriptase peptide (a model novel antigen) were studied in parallel. Patients with SCCHN had a significantly higher mean frequency of CD8+ T cells specific for wt p53(264-272) than normal donors (P = 0.0041). Surprisingly, the frequency of epitope-specific T cells in the circulation of patients did not correlate with p53 accumulation in the tumor. In patients whose tumors had normal p53 expression or had p53 gene mutations preventing presentation of this epitope, high frequencies of wt p53(264-272)-specific CD8+ T cells were found, of which many were memory T cells. In contrast, patients whose tumors accumulated p53 had low frequencies of wt p53(264-272)-specific CD8+ T cells, which predominantly had a naive phenotype and were unable to proliferate ex vivo in response to the epitope, as reported by us previously (T. K. Hoffmann, J. Immunol., 165: 5938-5944, 2000). This seemingly contradictory relationship between the high frequency of epitope-specific T cells and wt p53 expression in the tumor suggests that other factors may contribute to the observed anti-p53 responses. Human papillomavirus-16 E6/E7 expression is common in SCCHN, and E6 is known to promote presentation of wt p53 epitopes. Although human papillomavirus-16 E6/E7 expression was detected in 46% of the tumors, it did not correlate with the frequency of wt p53(264-272)-specific CD8+ T cells or with p53 expression in the tumor. These findings emphasize the complexity of interactions between the tumor and the host immune system, and, thus, have particularly important implications for future p53-based immunization strategies.

Antibodies, Neoplasm↗

PubMed2002

Diagnostic strategies in cervical carcinoma of an unknown primary (CUP).

In patients with cervical cancer of an unknown primary (CUP), no established concept exists for the necessary diagnostic procedures. In order to find the primary tumor, extensive diagnostic steps are generally recommended; however, they are often not performed consistently. In the current study, we consistently used a diagnostic algorithm and analyzed its consequences on patients' prognoses. We retrospectively studied 57 patients who were found to have a cervical metastasis of the upper- or midneck and an unknown primary tumor after routine examination of the head and neck region. Patients were analyzed for the value of applied diagnostic measures, tumor classification, survival rates and frequencies of subsequent lymph node or distant metastases after the initial treatment. Our results showed that a diagnostic algorithm (lymph node biopsy, rigid panendoscopy with systematic biopsies of suspect regions as well as blind biopsies of endoscopically inconspicuous regions, including the tongue base and nasopharynx and bilateral tonsillectomy) led to the detection of 14 occult oropharyngeal and 5 nasopharyngeal primary tumors in the patients. These tumors were primarily diagnosed as CUP. Oropharyngeal tumors either grew submucosally or were so small that only microscopic evaluation of the entire tonsil uncovered the tumor. Imaging procedures (X-ray, ultrasound, CT, MRT and FDG-PET) as well as gynecological, urological and gastroenterological consultations did not reveal the primary tumors in any of the cases. The 3-year survival rate for the patients with occult oropharyngeal primary tumors was 100% after treatment, while the patients in which our diagnostic schedule did not reveal a primary tumor showed a survival rate of 58%. The prognosis of all of the patients with cervical carcinoma metastasis was dependent on the initial nodal stage. Metachronous metastasis after completion of the initial treatment was prognostically infaust, while secondary detection of the primary tumor was worthwhile during follow-up as long as further treatment options were offered. The prognosis of patients with cervical carcinoma metastases of the upper- and midneck is much more favorable than that of patients with a CUP syndrome of other localizations. Identification of an occult pharyngeal tumor is prognostically relevant, since it opens up the possibility of specific locoregional treatment. In patients with cervical CUP, blind but systematic pharyngeal biopsies, including bilateral tonsillectomy, should be performed.

Adult↗

PubMed2002

The ability of variant peptides to reverse the nonresponsiveness of T lymphocytes to the wild-type sequence p53(264-272) epitope.

Recently, we observed that CTL specific for the wild-type (wt) sequence p53(264-272) peptide could only be expanded ex vivo from PBMC of a subset of the HLA-A2.1(+) normal donors or cancer patients tested. Surprisingly, the tumors of the responsive patients expressed normal levels of wt p53 and could be considered unlikely to present this epitope. In contrast, tumors of nonresponsive patients accumulated mutant p53 and were more likely to present this epitope. We sought to increase the responsive rate to the wt p53(264-272) peptide of PBMC obtained from normal donors and patients by identifying more immunogenic variants of this peptide. Two such variants were generated by amino acid exchanges at positions 6 (6T) and 7 (7W) of the peptide. These variants were capable of inducing T cells from PBMC of nonresponsive donors that recognized the parental peptide either pulsed onto target cells or naturally presented by tumors. TCR Vbeta analysis of two T cell lines isolated from bulk populations of effectors reactive against the wt p53(264-272) peptide, using either the parental or the 7W variant peptide, indicated that these T cells were expressing identical TCR Vbeta13.6/complementarity-determining region 3/J region sequences. This finding confirms the heteroclitic nature of at least one of the variant peptides identified in this study. The use of variant peptides of the wt p53(264-272) epitope represents a promising approach to overcoming the nonresponsiveness of certain cancer patients to this self epitope, thereby enhancing its potential use in tumor vaccines for appropriately selected cancer patients.

Amino Acid Substitution↗

PubMed2002

Antitumor activity of protein kinase C inhibitors and cisplatin in human head and neck squamous cell carcinoma lines.

Protein kinase C (PKC) plays a pivotal role in signal transduction involved in the control of cell proliferation, differentiation and apoptosis. Interference with such signaling pathways may result in altered tumor cell response to antineoplastic drugs. We investigated the effects of two selective PKC inhibitors as single agents and in combination with cisplatin in cell lines derived from squamous cell carcinomas of the head and neck (SCCHN). Safingol (Saf) is directed against the regulatory domain, whereas chelerythrine (Che) interacts with the catalytic domain of PKC. In six SCCHN cell lines (UM-SCC 11B, 14A, 14C and 22B, 8029NA, and a 5-fold cisplatin-resistant subline 8029DDP). PKC activities ranged between 1 and 158 IU/1 x 10(7) cells, and they were inversely proportional to the amount of cellular epidermal growth factor receptor. Using the colorimetric MTT assay, PKC inhibitors Saf and Che showed comparable dose-dependent growth inhibition. The 50% inhibitory concentrations (IC50) were between 3.8-8.6 microM for Saf and 8.5-13.6 microM for Che with no relationship to PKC activity or cisplatin sensitivity of the respective cell lines. Combinations of cisplatin (IC50 = 0.4-5.8 microg/ml) and either PKC inhibitor (5 microM Saf, 10 microM Che) led to a significant decrease of cisplatin IC50 values in most cell lines. However, comparison with theoretical additive dose-response curves showed additive rather than synergistic effects for both PKC inhibitors.

Alkaloids↗

PubMed2002

Effects of tamoxifen on human squamous cell carcinoma lines of the head and neck.

Tamoxifen (TAM) is a well-tolerated compound in the treatment of breast cancer and is primarily considered to act by competition with estrogen receptors (ER). Here we investigated the in vitro efficacy and potentially underlying mechanisms of TAM in established cell lines of squamous cell carcinomas of the head and neck (SCCHN). Using proliferation and apoptosis assays the antitumor activity of TAM in five SCCHN and the breast carcinoma line MCF-7 (positive control) was determined. MCF-7 was more sensitive to low-dose TAM (below 1 microM), whereas SCCHN showed significant growth inhibition at higher TAM concentrations (5-10 microM). Growth curve analysis and apoptosis assays were indicative for a cytostatic effect of low-dose TAM and high-dose TAM led to cell loss by apoptosis in sensitive SCCHN. In order to further characterize the observed antitumor effects we determined the amount of steroid hormone receptors with the dextran-coated charcoal method and immunocytochemistry. In addition, production of transforming growth factor (TGF-)-alpha, -beta1 and -beta2 was measured by ELISA, and protein kinase C (PKC) activity was assessed with a radioligand assay. Except MCF-7, none of the SCCHN lines was positive for ER. TAM caused decreased TGF-alpha and increased TGF-beta levels in MCF-7, but not in SCCHN supernatants. Furthermore, the antiestrogen reduced PKC activity in MCF-7, but not in SCCHN. In the present in vitro system, the observed antitumor activity of high-dose TAM in SCCHN cannot be explained by estrogen antagonism, alterations of TGF-alpha/beta levels or decreased PKC activity.

Antineoplastic Agents, Hormonal↗

PubMed2002

Argon plasma coagulation (APC) in palliative surgery of head and neck malignancies.

OBJECTIVES: Surgical reduction of bulky disease is an important treatment option in patients with incurable head and neck malignancies. In general, conventional tumor ablation is associated with significant hemorrhage, and the resulting tumorous wound surface entails aftercare problems. Argon plasma coagulation (APC) represents a novel technique providing effective hemostasis and wound sealing. Thus, APC features requirements of particular interest in palliative surgery of the head and neck. STUDY DESIGN: Using APC, we performed 18 palliative tumor resections in a series of 8 consecutive patients with recurrent head and neck lesions. Five patients received repeated APC treatment up to five times. METHODS: APC as non-contact, high-frequency electrosurgery under inert argon plasma atmosphere allows dissection, hemostasis, and desiccation of tumor tissue in a one-step procedure. In consideration of the limited and heterogeneous group of patients, results are interpreted descriptively. RESULTS: In every case of palliative surgery, APC caused efficient hemostasis, which helped significantly to reduce both time exposure of the operation and intraoperative loss of blood. Only one APC-unrelated complication occurred (transient rhino-liquorrhea), and none of the patients developed postoperative hemorrhage. Finally, APC produced dry and clean wound surfaces facilitating surgical aftercare. The achieved esthetic and functional improvements strengthened the patient's autonomy and social acceptance. CONCLUSION: APC is highly recommended for palliative surgery of head and neck malignancies.

Adolescent↗