Efficacy In Head And Neck Squamous Cell Carcinoma Research Articles

Role of mitophagy in head and neck squamous cell carcinoma: Prognosis and immune insights

ObjectiveTo explore the correlation between mitophagy and the tumor microenvironment (TME) in patients with head and neck squamous cell carcinoma (HNSCC), with an aim to enhance therapeutic efficacy for HNSCC. MethodsA machine learning-based multigene prognostic signature was developed based on mitophagy-related differentially expressed genes (MRGs) identified in The Cancer Genome Atlas cohort. This signature was correlated with the TME using gene set enrichment analysis. The association between this prognostic signature and various immunological features of the TME was explored, including status of tumor-infiltrating immune cells, expression of immune checkpoint molecules, and the immunoscore. Immunohistochemistry validated the expression of hub gene CSNK2A2 and assessed its relationship with immunomarker expression. Quantitative PCR validated CSNK2A2 knockdown in HNSCC cell lines. Functional experiments including Transwell assays to determine cell migration and invasion, Cell Counting Kit 8 assay, and 5-ethynyl-2-deoxyuridine assay were performed to confirm the role of CSNK2A2 in HNSCC. Finally, a subcutaneous xenograft model was generated in C3H mice to validate our findings. ResultsThe MRG-based prognostic signature showed excellent predictive performance. High-risk patients had significantly shorter progression-free and overall survival (P ​< ​0.0001) than low-risk patients. CD8+ T cell infiltration was lower in high-risk groups, whereas low-risk groups showed higher immunological marker expression. Thus, the low-risk HNSCC subtype may benefit from immune therapy, while high-risk subtypes may benefit from chemotherapy (P ​< ​0.001). CSNK2A2 was highly expressed and strongly correlated with CD8 and PD-L1 based on immunohistochemistry of the HNSCC tissue microarray. CSNK2A2 knockdown reduced cell migration, invasion, and proliferation, and arrested cells in G1 phase. In vivo, it led to slower tumor growth and smaller tumor volumes. ConclusionWe established a potential prognostic signature that could improve HNSCC management in the future. CSNK2A2 may be a new biomarker to predict immunotherapy efficacy in HNSCC.

Glutamine inhibition combined with CD47 blockade enhances radiotherapy-induced ferroptosis in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a formidable cancer type that poses significant treatment challenges, including radiotherapy (RT) resistance. The metabolic characteristics of tumors present substantial obstacles to cancer therapy, and the relationship between RT and tumor metabolism in HNSCC remains elusive. Ferroptosis is a type of iron-dependent regulated cell death, representing an emerging disease-modulatory mechanism. Here, we report that after RT, glutamine levels rise in HNSCC, and the glutamine transporter protein SLC1A5 is upregulated. Notably, blocking glutamine significantly enhances the therapeutic efficacy of RT in HNSCC. Furthermore, inhibition of glutamine combined with RT triggers immunogenic tumor ferroptosis, a form of nonapoptotic regulated cell death. Mechanistically, RT increases interferon regulatory factor (IRF) 1 expression by activating the interferon signaling pathway, and glutamine blockade augments this efficacy. IRF1 drives transferrin receptor expression, elevating intracellular Fe2+ concentration, disrupting iron homeostasis, and inducing cancer cell ferroptosis. Importantly, the combination treatment-induced ferroptosis is dependent on IRF1 expression. Additionally, blocking glutamine combined with RT boosts CD47 expression and hinders macrophage phagocytosis, attenuating the treatment effect. Dual-blocking glutamine and CD47 promote tumor remission and enhance RT-induced ferroptosis, thereby ameliorating the tumor microenvironment. Our work provides valuable insights into the metabolic and immunological mechanisms underlying RT-induced ferroptosis, highlighting a promising strategy to augment RT efficacy in HNSCC.

Activation of the EGFR/PI3K/AKT pathway limits the efficacy of trametinib treatment in head and neck cancer.

Blocking the mitogen-activated protein kinase (MAPK) pathway with the MEK1/2 inhibitor trametinib has produced promising results in patients with head and neck squamous cell carcinoma (HNSCC). In the current study, we showed that trametinib treatment leads to overexpression and activation of the epidermal growth factor receptor (EGFR) in HNSCC cell lines and patient-derived xenografts. Knockdown of EGFR improved trametinib treatment efficacy both in vitro and in vivo. Mechanistically, we demonstrated that trametinib-induced EGFR overexpression hyperactivates the phosphatidylinositol 3-kinase (PI3K)/AKT pathway. In vitro, blocking the PI3K pathway with GDC-0941 (pictilisib), or BYL719 (alpelisib), prevented AKT pathway hyperactivation and enhanced the efficacy of trametinib in a synergistic manner. In vivo, a combination of trametinib and BYL719 showed superior antitumor efficacy vs. the single agents, leading to tumor growth arrest. We confirmed our findings in a syngeneic murine head and neck cancer cell line in vitro and in vivo. Taken together, our findings show that trametinib treatment induces hyperactivation of EGFR/PI3K/AKT; thus, blocking of the EGFR/PI3K pathway is required to improve trametinib efficacy in HNSCC.

SOX18 meditates the resistance of Bmi1-expressing cells to cetuximab in HNSCC.

Head and neck squamous cell carcinoma (HNSCC) is the most common type of malignancy in the head and neck region worldwide. The therapeutic strategies for HNSCC remain unsatisfying and limited. Here, we found a population of resistant Bmi1-expressing cells in the presence of cetuximab treatment and reported a novel role of SRY-box transcription factor 18 (SOX18), a member of the SOX family, in promoting HNSCC resistance to cetuximab. This study aimed to investigate the regulatory mechanism of Sox18 in Bmi1-positive cells and to search for better therapeutic targets. We successfully obtained Bmi1CreER, RosatdTomato, and RosaDTA mice and identified Bmi1-expressing cells through lineage tracing. SOX18 expression in HNSCC and normal tissues was analyzed by immunohistochemistry, colocalization of Sox18, and Bmi1-expressing cells was analyzed by immunofluorescence, and SOX18 expression in SCC9 cell lines was quantified by western blotting and quantitative real-time PCR. The investigation of the mechanism of SOX18-mediated cetuximab resistance in Bmi1-positive cells was based on the analysis of single-cell RNA-seq data obtained from the Gene Expression Omnibus (GEO) database. Western blotting was performed to verify the results obtained from the single-cell RNA-seq analysis. In our study, we demonstrated that Bmi1-expressing cells were resistant to cetuximab treatment and that depletion of Bmi1-expressing cells improved cetuximab efficacy in HNSCC. We then discovered that Sox18 mediated the stem cell-like properties of Bmi1-expressing cells and promoted cellular cetuximab resistance through an oxidative phosphorylation pathway. There was a significant downregulation of key genes in the oxidative phosphorylation pathway in Sox18 knockout cell lines. Taken together, the findings of our study suggest that Sox18 mediates the resistance of Bmi1-expressing cells to cetuximab in HNSCC via the oxidative phosphorylation pathway.

Construction of a hypoxia-derived gene model to predict the prognosis and therapeutic response of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) ranks as the sixth most common cancer worldwide and has a poor prognosis in the advanced stage. Increasing evidence has shown that hypoxia contributes to genetic alterations that have essential effects on the occurrence and progression of cancers. However, the exact roles hypoxia-related genes play in HNSCC remain unclear. In this study, we downloaded the mRNA expression profiles and clinical data of patients with HNSCC from The Cancer Genome Atlas and Gene Expression Omnibus. Two molecular subtypes were identified based on prognostic hypoxia-related genes using the ConsensusClusterPlus method. ESTIMATE was used to calculate the immune score of each patient. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology were used for functional annotation. A prognostic risk model was generated by Cox regression and least absolute shrinkage and selection operator analysis. We identified two distinct molecular subtypes, cluster 1 and cluster 2, based on 200 hypoxia-related genes. Additionally, we identified three hypoxia-immune subgroups (hypoxia-high/immune-low, hypoxia-low/immune-high, and mixed subgroups). The hypoxia-high/immune-low group had the worst prognosis, while the hypoxia-low/immune-high group had the best prognosis. Patients in the hypoxia-low/immune-high group were more sensitive to anti-PD-L1 treatment and chemotherapy than those in the hypoxia-high/immune-low group. Furthermore, we constructed a prognostic risk model based on the differentially expressed genes between the hypoxia-immune subgroups. The survival analysis and time-dependent ROC analysis results demonstrated the good performance of the established 7-gene signature for predicting HNSCC prognosis. In conclusions, the constructed hypoxia-related model might serve as a promising biomarker for the diagnosis and prognosis of HNSCC, and it could predict immunotherapy and chemotherapy efficacy in HNSCC.

Pathologic response after induction chemo-immunotherapy with single or double immune checkpoint inhibition in locally advanced head and neck squamous cell carcinoma (HNSCC): Expansion cohorts of the CheckRad-CD8 trial.

6064 Background: Targeting the immune checkpoint CTLA-4 in addition to PD-1/PD-L1 alone did not increase efficacy in HNSCC, whereas this has not been studied in combination with chemotherapy. Induction chemo-immunotherapy followed by pathologic response-based patient selection for chemotherapy-free radioimmunotherapy was efficient in locally advanced HNSCC (J Immunother Cancer. 2022 Jan;10(1):e003747). The expansion cohorts of the CheckRad-CD8 trial studied safety and efficacy of induction chemo-immunotherapy with increased dose or without CTLA-4 inhibition. Methods: Patients with previously untreated stage III-IVB (AJCC 8th edition) HNSCC were eligible for this multicenter phase II trial. Induction chemo-immunotherapy of the main cohort (MC) consisted of a single cycle of cisplatin 30mg/m² d1-3, docetaxel 75mg/m² d1, durvalumab 1500mg fix dose d5 and tremelimumab 75mg fix dose d5. Patients in expansion cohort 1 (EC1) received this combination with high dose tremelimumab 300mg fix dose d5 and patients in expansion cohort 2 (EC2) received no tremelimumab. In EC1 and EC2 prophylactic G-CSF was recommended. Patients with at least 20% increase of intratumoral CD8+ immune cell density or pathological complete response (pCR) in the re-biopsy entered chemotherapy-free radioimmunotherapy up to a total dose of 70Gy. The current analysis focuses on toxicity and pathologic response after induction chemo-immunotherapy. Results: Between Sep 2018 and Sep 2021, 80 patients were enrolled in the MC (one excluded), 20 in EC1 and 20 in EC2 (one excluded) subsequently. In the MC, EC1 and EC2 a total of 56%, 50%, 58% were stage IV and 29%, 30%, 26% had p16 positive oropharyngeal tumors. Baseline median intratumoral CD8+ immune cell density was 395/mm², 505/mm² and 763/mm² in MC, EC1 and EC2. After induction chemo-immunotherapy 41 (52%), 12 (60%) and 11 (58%) of the patients had pCR in the re-biopsy in MC, EC1 and EC2. Patients with residual tumor after induction therapy had a median intratumoral CD8+ immune cell density of 670/mm², 781/mm² and 1605/mm², which was a median increase by factor 3.0, 2.1 and 4.8 in the corresponding patients’ tissue samples. In the cohorts MC, EC1 and EC2 the overall rate of grade 3-4 adverse events per patient was 1.38, 1.35 and 0.58. The corresponding rate of non-hematologic adverse events per patient was 0.84, 0.95 and 0.37, respectively. Conclusions: Neither increase of tremelimumab dosage nor its omission did significantly affect pathologic response to induction chemo-immunotherapy with cisplatin/ docetaxel/ durvalumab. Non-hematologic toxicity was slightly increased for high dose tremelimumab and clearly decreased without tremelimumab. The role of concomitant administration of tremelimumab with radiotherapy cannot be assessed until the final study analysis. Clinical trial information: NCT03426657.

Palbociclib-based high-throughput combination drug screening identifies synergistic therapeutic options in HPV-negative head and neck squamous cell carcinoma

BackgroundDeregulation of cell-cycle pathway is ubiquitously observed in human papillomavirus negative (HPVneg) head and neck squamous cell carcinoma (HNSCC). Despite being an attractive target, CDK4/6 inhibition using palbociclib showed modest or conflicting results as monotherapy or in combination with platinum-based chemotherapy or cetuximab in HPVneg HNSCC. Thus, innovative agents to augment the efficacy of palbociclib in HPVneg HNSCC would be welcomed.MethodsA collection of 162 FDA-approved and investigational agents was screened in combinatorial matrix format, and top combinations were validated in a broader panel of HPVneg HNSCC cell lines. Transcriptional profiling was conducted to explore the molecular mechanisms of drug synergy. Finally, the most potent palbociclib-based drug combination was evaluated and compared with palbociclib plus cetuximab or cisplatin in a panel of genetically diverse HPVneg HNSCC cell lines and patient-derived xenograft models.ResultsPalbociclib displayed limited efficacy in HPVneg HNSCC as monotherapy. The high-throughput combination drug screening provided a comprehensive palbociclib-based drug-drug interaction dataset, whereas significant synergistic effects were observed when palbociclib was combined with multiple agents, including inhibitors of the PI3K, EGFR, and MEK pathways. PI3K pathway inhibitors significantly reduced cell proliferation and induced cell-cycle arrest in HPVneg HNSCC cell lines when combined with palbociclib, and alpelisib (a PI3Kα inhibitor) was demonstrated to show the most potent synergy with particularly higher efficacy in HNSCCs bearing PIK3CA alterations. Notably, when compared with cisplatin and cetuximab, alpelisib exerted stronger synergism in a broader panel of cell lines. Mechanistically, RRM2-dependent epithelial mesenchymal transition (EMT) induced by palbociclib, was attenuated by alpelisib and cetuximab rather than cisplatin. Subsequently, PDX models with distinct genetic background further validated that palbociclib plus alpelisib had significant synergistic effects in models harboring PIK3CA amplification.ConclusionsThis study provides insights into the systematic combinatory effect associated with CDK4/6 inhibition and supports further initiation of clinical trials using the palbociclib plus alpelisib combination in HPVneg HNSCC with PIK3CA alterations.

Antitumor Efficacy of EGFR-Targeted Recombinant Immunotoxin in Human Head and Neck Squamous Cell Carcinoma.

Over 90% of head and neck squamous cell carcinoma (HNSCC) overexpresses the epidermal growth factor receptor (EGFR). However, the EGFR-targeted monotherapy response rate only achieves 10-30% in HNSCC. Recombinant immunotoxin (RIT) often consists of an antibody targeting a tumor antigen and a toxin (e.g., diphtheria toxin [DT]) that kills cancer cells. We produced a humanized RIT, designated as hDT806, targeting overexpressed EGFR and investigated its effects in HNSCC. Distinct from the EGFR-targeted tyrosine kinase inhibitor erlotinib or antibody cetuximab, hDT806 effectively suppressed cell proliferation in the four HNSCC lines tested (JHU-011, -013, -022, and -029). In JHU-029 mouse xenograft models, hDT806 substantially reduced tumor growth. hDT806 decreased EGFR protein levels and disrupted the EGFR signaling downstream effectors, including MAPK/ERK1/2 and AKT, while increased proapoptotic proteins, such as p53, caspase-9, caspase-3, and the cleaved PAPR. The hDT806-induced apoptosis of HNSCC cells was corroborated by flow cytometric analysis. Furthermore, hDT806 resulted in a drastic inhibition in RNA polymerase II carboxy-terminal domain phosphorylation critical for transcription and a significant increase in the γH2A.X level, a DNA damage marker. Thus, the direct disruption of EGFR signaling, transcription inhibition, DNA damage, as well as apoptosis induced by hDT806 may contribute to its antitumor efficacy in HNSCC.

Functional RNAi Screens Define Distinct Protein Kinase Vulnerabilities in EGFR-Dependent HNSCC Cell Lines.

The inhibitory epidermal growth factor receptor (EGFR) antibody, cetuximab, is an approved therapy for head and neck squamous cell carcinoma (HNSCC). Despite tumor response observed in some HNSCC patients, cetuximab alone or combined with radio- or chemotherapy fails to yield long-term control or cures. We hypothesize that a flexible receptor tyrosine kinase coactivation signaling network supports HNSCC survival in the setting of EGFR blockade, and that drugs disrupting this network will provide superior tumor control when combined with EGFR inhibitors. In this work, we submitted EGFR-dependent HNSCC cell lines to RNA interference-based functional genomics screens to identify, in an unbiased fashion, essential protein kinases for growth and survival as well as synthetic lethal targets for combined inhibition with EGFR antagonists. Mechanistic target of rapamycin kinase (MTOR) and erythroblastosis oncogene B (ERBB)3 were identified as high-ranking essential kinase hits in the HNSCC cell lines. MTOR dependency was confirmed by distinct short hairpin RNAs (shRNAs) and high sensitivity of the cell lines to AZD8055, whereas ERBB3 dependency was validated by shRNA-mediated silencing. Furthermore, a synthetic lethal kinome shRNA screen with a pan-ERBB inhibitor, AZD8931, identified multiple components of the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase pathway, consistent with ERK reactivation and/or incomplete ERK pathway inhibition in response to EGFR inhibitor monotherapy. As validation, distinct mitogen-activated protein kinase kinase (MEK) inhibitors yielded synergistic growth inhibition when combined with the EGFR inhibitors, gefitinib and AZD8931. The findings identify ERBB3 and MTOR as important pharmacological vulnerabilities in HNSCC and support combining MEK and EGFR inhibitors to enhance clinical efficacy in HNSCC. SIGNIFICANCE STATEMENT: Many cancers are driven by nonmutated receptor tyrosine kinase coactivation networks that defy full inhibition with single targeted drugs. This study identifies erythroblastosis oncogene B (ERBB)3 as an essential protein kinase in epidermal growth factor receptor-dependent head and neck squamous cell cancer (HNSCC) cell lines and a synthetic lethal interaction with the extracellular signal-regulated kinase mitogen-activated protein kinase pathway that provides a rationale for combining pan-ERBB and mitogen-activated protein kinase inhibitors as a therapeutic approach in subsets of HNSCC.

PTEN and cetuximab resistance in head and neck squamous cell carcinoma (HNSCC).

6061 Background: Platinum-based chemotherapy in association to cetuximab is the standart first-line treatment for metastatic HNSCC. There is no established biomarker for cetuximab efficacy in HNSCC. We have previously shown that PTEN loss of expression is a bad prognostic factor for patients treated with platinum-based chemotherapy and cetuximab. The aim of the present study was evaluate the prognostic impact of PTEN loss of expression in patients treated with or without cetuximab and to evaluate its predictive value to cetuximab benefit. Methods: One hundred and nineteen patients with metastatic or locally recurrent HNSCC were included. Clinical data on treatment and outcomes was retroespectively colected from medical charts. Tissue micro-array was constructed to evaluate PTEN protein expression through immunohistochemistry. Citoplasmatic staining was evaluated using H-score. Tumors with H-score &lt; 10 were considered to present PTEN loss of expression. Results: From the 119 patients 72 were treated with chemotherapy plus cetuximab while 47 were treated with chemotherapy alone. Median overall survival (mOS) was 9.2 months and median progression free survival (PFS) was 4.6 months. Patients treated with cetuximab compared to those who were not treated with cetuximab had a mOS of 11.4 vs 7.0 months (p = 0.770) and a median PFS of 6.2 vs 3.0 months (p = 0.249). Patients with PTEN loss of expression had a worse OS and PFS with mOS of 5.8 vs 10.5 months (p = 0.002) months and mPFS of 3.2 vs 5.2 (p = 0.015). On multivariate analysis including PTEN loss of expression and ECOG performance status both remained independently associated to survival with HR 2.25 (CI95% 1.28-3.97, p = 0.005) for PTEN loss of expression and a HR 1.63 (CI95% 1.07-2.50, p = 0.023) for ECOG. Negative prognostic impact of PTEN loss of expression was seen only in the cetuximab treated patients (mOS 7.3 vs 13.0 months; p = 0.002) but not in the chemotherapy only group (mOS 3.2 vs 7.5 months; p = 0.051). Interaction test for treatment group and PTEN loss of expression showed a p = 0.418. Conclusions: The present study confirms PTEN as a prognostic factor for metastatic HNSCC and suggests PTEN expression should be studied in larger cohorts to evaluate its predictive value to cetuximab response.

Targeting VEGFR and FGFR in head and neck squamous cell carcinoma in vitro.

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous disease characterized by a tumor microenvironment (TME) that overexpresses vascular endothelial growth factor receptor (VEGFR) and fibroblast growth factor receptor (FGFR), which can lead to neovascularization, tumor growth and metastasis. Therapeutic strategies inhibiting these signaling pathways might lead to innovative HNSCC treatments. Five HNSCC cell lines were characterized based on VEGFR1-3 and FGFR1-4 expression by sqRT-PCR and treated with three different tyrosine kinase inhibitors (TKIs) (nintedanib, dovitinib and pazopanib), all of which are effective against VEGFR and FGFR family members. Crystal violet assays were performed to analyze the effect of the treatments on cell growth (viability). Additionally, VEGFR1-3 and FGFR1-4 expression data were retrieved from The Cancer Genome Atlas (TCGA), and statistical analyses were performed to investigate the receptor expression level in the different cell lines and the efficacy of the single-agent treatments. A correlation analysis was performed to quantify the degree of relationship between receptor expression and drug efficacy. With the exception of VEGFR2, the targeted receptors were expressed at different levels in all of the cell lines. The cell lines exhibited concentration-dependent responses with cell line-specific differences toward two of the three TKIs (nintedanib and dovitinib). Notably, all of the cell lines were resistant to pazopanib. TKIs have potential as therapeutic agents for HNSCC. Cell line-specific differences were observed in our invitro experiments. The observed pazopanib resistance could be explained by receptor expression. Further investigation is required to determine TKI efficacy in HNSCC.

PET Imaging in Head and Neck Cancer Patients to Monitor Treatment Response: A Future Role for EGFR-Targeted Imaging.

Approximately 50,000 new cases of head and neck squamous cell carcinoma (HNSCC) are diagnosed worldwide each year and subsequently treated with surgery, chemotherapy, radiotherapy, and/or targeted therapy. The heterogeneity of the patient population in terms of treatment response drives the search for tumor-specific biomarkers. Imaging of biomarkers can reveal patient-specific responses to therapies and, if assessed early after the start of treatment, may allow adaptation of treatment regimens. In this review, tracers that have been tested to monitor treatment efficacy in HNSCC by PET scanning prior to and early after the onset of treatment are discussed. An important imaging target for this application in HNSCC patients is the EGFR. It steers the pathways related to proliferation, hypoxia, DNA damage repair, and apoptosis, all treatment-resistance mechanisms. The anti-EGFR antibody cetuximab has been labeled with various radionuclides and has been tested as an imaging biomarker in several HNSCC models. These studies suggest that EGFR-targeting tracers can be used to monitor EGFR receptor expression in HNSCC and have the potential to noninvasively monitor cetuximab treatment and steer individualized treatment regimens. Multiple factors can influence the uptake of EGFR-targeting tracers. Here, we discuss the relevance of gene and protein overexpression, mutations, and amplifications related to EGFR signaling. In addition, monoclonal antibody properties and the effect on the host immune system are reviewed in light of the future role of EGFR-targeted imaging in HNSCC.

Low PTEN expression is associated with worse overall survival in head and neck squamous cell carcinoma patients treated with chemotherapy and cetuximab.

Platinum-based chemotherapy associated with cetuximab is the first-line treatment for inoperable recurrence or metastatic head and neck squamous cell carcinoma (HNSCC). There is no established biomarker for cetuximab efficacy in HNSCC. The PI3K pathway is one of the most frequently altered pathways in HNSCC. Loss of phosphatase and tensin homolog (PTEN) expression occurs in up to 30 % of cases. This was a retrospective analysis of data from 61 patients with inoperable recurrence or metastatic HNSCC treated with cetuximab. PTEN, epidermal growth factor receptor and p16 expression were analyzed by immunohistochemistry and tested for association with clinical outcomes. Median overall survival was 11.4 months and progression-free survival was 6.9 months. Low PTEN expression was present in 26.2 % of patients and identified patients with worse prognosis. p16 was positive in only 8.5 % of tumors. Low PTEN expression in patients treated with cetuximab plus chemotherapy emerged as a prognostic biomarker and should be evaluated for its predictive role for cetuximab efficacy.

Gemcitabine Inhibits Murine Head and Neck Squamous Cell Carcinoma Growth via Proteasome-Dependent Degradation of Chk1 Leading to Cell Cycle Arrest and Apoptosis

Head and neck squamous cell carcinoma (HNSCC) is a common tumor worldwide that often presents at an advanced stage with poor prognosis. Advanced HNSCC frequently exhibits resistance to chemotherapy limiting its efficacy. Gemcitabine is a pyrimidine-based analog that is currently used for the treatment of metastatic pancreatic cancer. In this study, we examined the anti-tumor effects of gemcitabine in a highly aggressive murine model of HNSCC (LY2). In vitro cell viability and in vivo tumor growth inhibitory assays were carried out to determine the sensitivity of LY2 cells to gemcitabine. Immunohistochemical, Western blotting, RT-PCR and RNAi-mediated silencing assays were used to characterize effects of gemcitabine cell proliferation, DNA synthesis, apoptosis, pro-survival and DNA damage response signaling pathways. LY2 cells treated with gemcitabine undergo apoptosis mediated by the activation of both caspase-3 and -9. Gemcitabine on treatment induces rapid phosphorylation of checkpoint kinase 1 (Chk1) in LY2 cells and subsequent degradation in a time and dose dependent manner. Proteasome inhibitor MG132 blocks Chk1 degradation and decreases LY2 cells susceptibility to gemcitabine. Inhibition of Chk1 function, either using inhibitor PD 407824 or small interfering RNA (siRNA), increases the sensitivity of LY2 cells to gemcitabine. Gemcitabine treatment resulted in significant reduction in tumor growth relative to saline-treated control in a syngeneic orthotopic murine model of HNSCC. Gemcitabine-induced DNA replication stress in LY2 cells activates Chk1 by phosphorylation and promotes Chk1 degradation via the ubiquitin-proteasome pathway. Depletion of Chk1 terminates S-phase check point in LY2 cells resulting in apoptotic cell death. Our data provides an important rationale for integrating gemcitabine to optimize chemotherapeutic efficacy in HNSCC.

Molecular pathology of head-and-neck cancer.

Each year approximately 40,000 people in the United States and 500,000 people worldwide are diagnosed with head-and-neck squamous cell carcinoma (HNSC). Although there have been significant improvements in the treatment of this disease, leading to decreased morbidity, over the past few decades the 5-year survival rate has remained largely unchanged at 50%. Genetic and epigenetic alterations as well as viral agents have been implicated in the development of head-and-neck cancer. Advances in our understanding of the molecular biology underlying these processes have spawned numerous, diverse strategies to exploit this understanding in applied pathology. Preliminary investigations have analyzed body fluids and margins for the presence of cancer cells. Specific molecular alterations have been associated with improved treatment response and prognosis. Molecular therapy has been shown to have some clinical efficacy in HNSC. Expression profiles may be generated for specific primary tumors and compared to known markers of disease. Improved molecular characterization of primary tumors, surgical margins and body fluids may allow clinicians to detect and treat earlier lesions, predict a tumor's response to treatment, tailor treatment to specific molecular alterations and ultimately improve clinical outcomes related to HNSC.