Hypoxia in head and neck cancer

Is there a role for [18F]-FMISO PET to guide dose adaptive radiotherapy in head and neck cancer? A review of the literature

Purpose

Hypoxia is a major cause of radioresistance in head and neck cancer (HNC), resulting in treatment failure and disease recurrence. 18F-fluoromisonidazole [18F]FMISO PET has been proposed as a means of localising intratumoural hypoxia in HNC so that radiotherapy can be specifically escalated in hypoxic regions. This concept may not be deliverable in routine clinical practice, however, given that [18F]FMISO PET is costly, time consuming and difficult to access. The aim of this review was to summarise clinical studies involving [18F]FMISO PET to ascertain whether it can be used to guide radiotherapy treatment in HNC.

Methods

A comprehensive literature search was conducted on PubMed and Web of Science databases. Studies investigating [18F]FMISO PET in newly diagnosed HNC patients were considered eligible for review.

Results

We found the following important results from our literature review: 1)Studies have focussed on comparing [18F]FMISO PET to other hypoxia biomarkers, but currently there is no evidence of a strong correlation between [18F]FMISO and these biomarkers.2)The results of [18F]FMISO PET imaging are not necessarily repeatable, and the location of uptake may vary during treatment.3)Tumour recurrences do not always occur within the pretreatment hypoxic volume on [18F]FMISO PET.4)Dose modification studies using [18F]FMISO PET are in a pilot phase and so far, none have demonstrated the efficacy of radiotherapy dose painting according to [18F]FMISO uptake on PET.

Conclusions

Our results suggest it is unlikely [18F]FMISO PET will be suitable for radiotherapy dose adaptation in HNC in a routine clinical setting. Part of the problem is that hypoxia is a dynamic phenomenon, and thus difficult to delineate on a single scan. Currently, it is anticipated that [18F]FMISO PET will remain useful within the research setting only.

The Effect of GLUT1 and HIF-1α Expressions on Glucose Uptake and Patient Survival in Non-Small-Cell Lung Carcinoma

Lung cancer is the second-most-common cancer while being the leading cause of cancer deaths worldwide. It has been found that glucose transporter 1 (GLUT1) and hypoxia-inducible factor 1α (HIF-1α) are overexpressed in various malignancies and that they correlate with the maximum standard uptake values (SUVmax) on 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG PET/CT) and poor prognosis. In this study, we aim to evaluate the relationship between the SUVmax, GLUT1, and HIF-1α expression with primary tumor size, histological type, lymph node metastases, and patient survival. Of the 48 patients with non-small-cell lung cancer, those with squamous cell carcinomas (SCCs) had significantly higher GLUT1 and HIF-1α immunohistochemical expressions in comparison to adenocarcinomas (ACs), while there was no statistically significant difference in FDG accumulation between them. No significant correlation was noted between either GLUT1 or HIF-1α protein expression and FDG uptake and overall survival. However, an analysis of tumor transcriptomics showed a significant difference in overall survival depending on mRNA expression; patients with SCC and high HIF-1α levels survived longer compared to those with low HIF-1α levels, while patients with AC and low GLUT1 levels had a higher average survival time than those with high GLUT1 levels. Further studies are needed to determine the prognostic value of the expression of these factors depending on the histologic type.

Overcoming the Impact of Hypoxia in Driving Radiotherapy Resistance in Head and Neck Squamous Cell Carcinoma

Hypoxia is very common in most solid tumours and is a driving force for malignant progression as well as radiotherapy and chemotherapy resistance. Incidences of head and neck squamous cell carcinoma (HNSCC) have increased in the last decade and radiotherapy is a major therapeutic technique utilised in the treatment of the tumours. However, effectiveness of radiotherapy is hindered by resistance mechanisms and most notably by hypoxia, leading to poor patient prognosis of HNSCC patients. The phenomenon of hypoxia-induced radioresistance was identified nearly half a century ago, yet despite this, little progress has been made in overcoming the physical lack of oxygen. Therefore, a more detailed understanding of the molecular mechanisms of hypoxia and the underpinning radiobiological response of tumours to this phenotype is much needed. In this review, we will provide an up-to-date overview of how hypoxia alters molecular and cellular processes contributing to radioresistance, particularly in the context of HNSCC, and what strategies have and could be explored to overcome hypoxia-induced radioresistance.

Hypoxia induces radioresistance, epithelial‑mesenchymal transition, cancer stem cell‑like phenotype and changes in genes possessing multiple biological functions in head and neck squamous cell carcinoma

Hypoxia has been linked with increased resistance to treatment in various solid tumors, including head and neck squamous cell carcinoma (HNSCC). The aim of the present study was to identify genes involved in hypoxia‑mediated responses to radiotherapy in HNSCC. A total of three HNSCC cell lines with an epithelial phenotype were selected for this study and cultured under normoxic (21% O₂) or hypoxic (1% O₂) conditions. The sensitivity of the HNSCC cells to radiotherapy was assessed by a crystal violet assay. Western blotting (for protein expression), cDNA microarrays and reverse transcription‑quantitative PCR (for gene expression) were also applied. Small interfering RNA silencing was used to knock down target genes. The results revealed that hypoxia negatively affected the response of HNSCC cells to radiotherapy. Of note, increased levels of N‑cadherin, vimentin and fibronectin, as well as stem cell‑associated transcription factors, were observed under hypoxia. The microarray analysis revealed a number of hypoxia‑regulated genes that were involved in multiple biological functions. However, downregulation of hypoxia‑regulated genes did not affect sensitivity to radiotherapy of the investigated cell lines. Taken together, the present findings indicated several important pathways and genes that were involved in hypoxia and radiotherapy resistance. It is hypothesized that panels of reported hypoxia‑regulated genes may be useful for the prediction of radiotherapy responses in patients with HNSCC.

First-In-Human Study in Cancer Patients Establishing the Feasibility of Oxygen Measurements in Tumors Using Electron Paramagnetic Resonance With the OxyChip

OBJECTIVE

The overall objective of this clinical study was to validate an implantable oxygen sensor, called the 'OxyChip', as a clinically feasible technology that would allow individualized tumor-oxygen assessments in cancer patients prior to and during hypoxia-modification interventions such as hyperoxygen breathing.

METHODS

Patients with any solid tumor at ≤3-cm depth from the skin-surface scheduled to undergo surgical resection (with or without neoadjuvant therapy) were considered eligible for the study. The OxyChip was implanted in the tumor and subsequently removed during standard-of-care surgery. Partial pressure of oxygen (pO2) at the implant location was assessed using electron paramagnetic resonance (EPR) oximetry.

RESULTS

Twenty-three cancer patients underwent OxyChip implantation in their tumors. Six patients received neoadjuvant therapy while the OxyChip was implanted. Median implant duration was 30 days (range 4-128 days). Forty-five successful oxygen measurements were made in 15 patients. Baseline pO2 values were variable with overall median 15.7 mmHg (range 0.6-73.1 mmHg); 33% of the values were below 10 mmHg. After hyperoxygenation, the overall median pO2 was 31.8 mmHg (range 1.5-144.6 mmHg). In 83% of the measurements, there was a statistically significant (p ≤ 0.05) response to hyperoxygenation.

CONCLUSIONS

Measurement of baseline pO2 and response to hyperoxygenation using EPR oximetry with the OxyChip is clinically feasible in a variety of tumor types. Tumor oxygen at baseline differed significantly among patients. Although most tumors responded to a hyperoxygenation intervention, some were non-responders. These data demonstrated the need for individualized assessment of tumor oxygenation in the context of planned hyperoxygenation interventions to optimize clinical outcomes.

From Anemia to Erythropoietin Resistance in Head and Neck Squamous Cell Carcinoma Treatment: A Carousel Driven by Hypoxia

Anemia has been identified as a significant negative prognosticator in head and neck squamous cell carcinoma (HNSCC) concurrent chemoradiotherapy (CCRT). Irrespective of the causes, anemia in HNSCC is believed to contribute to intratumoral hypoxia, which reduces the effectiveness of radiotherapy and oxygen-dependent chemotherapy. Correction of anemia with recombinant human erythropoietin (rHu-EPO) has been performed as a surrogate for hypoxia compensation to improve tumor control and survival outcomes. However, the results of the most important EPO clinical trials have been disappointing. Following the recent finding that EPO and its receptor (EPOR) are both expressed in HNSCC specimens, a new hypothesis has been advanced. This postulates that hypoxic signaling might activate EPOR through the hypoxia-inducible factor (HIF) signaling pathway and its downstream effectors, including carbonic anhydrase 9 (CA-9), glucose transporter 1 (GLUT-1), and vascular endothelial growth factor (VEGF), leading to the failure of rHu-EPO treatment, as assessed from the results of the best-known EPO trials. This review addresses the relationship among anemia, hypoxia, and tumoral EPO/EPOR expression in HNSCC treatment in an attempt to elucidate the main mechanisms involved in the resistance to rHu-EPO therapy, as in a carousel.

REDD1 overexpression in oral squamous cell carcinoma may predict poor prognosis and correlates with high microvessel density

The association between the hypoxia-inducible gene termed regulated in development and DNA damage responses 1 (REDD1) and microvessel density (MVD) in human oral cancer has rarely been reported. The present study aimed to explore REDD1 expression in oral squamous cell carcinoma (OSCC), its clinical prognostic significance and its correlation with angiogenesis. REDD1 expression in 23 pairs of fresh-frozen OSCC and matched peritumoral mucosal tissues was quantified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. Furthermore, 74 formalin-fixed paraffin-embedded OSCC tissues were collected to detect REDD1 expression and CD34-positive MVD by immunohistochemistry (IHC). The association between REDD1 expression and MVD, patients' clinicopathological characteristics and cancer-associated survival rate was also evaluated using the log-rank (Mantel-Cox) test. The results from RT-qPCR and western blotting demonstrated that REDD1 expression was significantly higher in OSCC tissues compared with peritumoral mucosal tissues (P<0.05). In addition, the results from IHC revealed that REDD1 expression was higher in OSCC tissues compared with peritumoral tissues. Furthermore, REDD1 expression was associated with advanced clinical stage, poorer tumor differentiation, lymphatic metastasis and tumor recurrence (P=0.000, P=0.003, P=0.006 and P<0.001, respectively). Additionally, REDD1 overexpression was positively correlated with MVD (r=0.7316; P<0.001). The results from Kaplan-Meier survival analysis demonstrated a significantly reduced disease-free survival and overall survival in patients with OSCC and high REDD1 expression (P<0.001). REDD1 may therefore serve as a novel prognostic biomarker, a key regulatory checkpoint that could coordinate angiogenesis and a new therapeutic target for patients with OSCC.

A Genomic-Clinicopathologic Nomogram Predicts Survival for Patients with Laryngeal Squamous Cell Carcinoma

Background

Long noncoding RNAs (lncRNAs), which have little or no ability to encode proteins, have attracted special attention due to their potential role in cancer disease. We aimed to establish a lncRNA signature and a nomogram incorporating the genomic and clinicopathologic factors to improve the accuracy of survival prediction for laryngeal squamous cell carcinoma (LSCC).

Methods

A LSCC RNA-sequencing (RNA-seq) dataset and the matched clinicopathologic information were downloaded from The Cancer Genome Atlas (TCGA). Using univariable Cox regression and least absolute shrinkage and selection operator (LASSO) analysis, we developed a thirteen-lncRNA signature related to prognosis. On the basis of multivariable Cox regression analysis results, a nomogram integrating the genomic and clinicopathologic predictors was built. The predictive accuracy and discriminative ability of the inclusive nomogram were confirmed by calibration curve and a concordance index (C-index), and compared with the TNM staging system by C-index and receiver operating characteristic (ROC) analysis. Decision curve analysis (DCA) was conducted to evaluate the clinical value of our nomogram.

Results

Thirteen overall survival- (OS-) related lncRNAs were identified, and the signature consisting of the selected thirteen lncRNAs could effectively divide patients into high-risk and low-risk subgroups, with area under curves (AUC) of 0.89 (3-year OS) and 0.885 (5-year OS). Independent factors derived from multivariable analysis to predict survival were margin status, tumor status, and lncRNA signature, which were all assembled into the nomogram. The calibration curve for the survival probability showed that the predictions based on the nomogram coincided well with actual observations. The C-index of the nomogram was 0.82 (0.77-0.87), and the area under curve (AUC) of the nomogram in predicting overall survival (OS) was 0.938, both of which were significantly higher than the traditional TNM stage. Decision curve analysis further demonstrated that our nomogram had larger net benefit than TNM stage.

Conclusion

An inclusive nomogram for patients with LSCC, comprising genomic and clinicopathologic variables, generates more accurate estimations of the survival probability when compared with TNM stage alone, but more data are needed before the nomogram is used in clinical practice.

Challenges facing antiangiogenesis therapy: The significant role of hypoxia-inducible factor and MET in development of resistance to anti-vascular endothelial growth factor-targeted therapies

It is now fully recognized that along with multiple physiological functions, angiogenesis is also involved in the fundamental process and pathobiology of several disorders including cancer. Recent studies have fully established the role of angiogenesis in cancer progression as well as invasion and metastasis. Consequently, many therapeutic agents such as monoclonal antibodies targeting angiogenesis pathway have been introduced in clinic with the hope for improving the outcomes of cancer therapy. Bevacizumab (Avastin®) was the first anti-vascular endothelial growth factor (VEGF) targeting monoclonal antibody developed with this purpose and soon received its accelerated US Food and Drug Administration (FDA) approval for treatment of patients with metastatic breast cancer in 2008. However, the failure to meet expecting results in different follow-up studies, forced FDA to remove bevacizumab approval for metastatic breast cancer. Investigations have now revealed that while suppressing VEGF pathway initially decreases tumor progression rate and vasculature density, activation of several interrelated pathways and signaling molecules following VEGF blockade compensate the insufficiency of VEGF and initially blocked angiogenesis, explaining in part the failure observed with bevacizumab single therapy. In present review, we introduce some of the main pathways and signaling molecules involved in angiogenesis and then propose how their interconnection may result in development of resistance to bevacizumab.

Expressional analysis of disease-relevant signalling-pathways in primary tumours and metastasis of head and neck cancers

Head and neck squamous cell carcinoma (HNSCC) often metastasize to lymph nodes resulting in poor prognosis for patients. Unfortunately, the underlying molecular mechanisms contributing to tumour aggressiveness, recurrences, and metastasis are still not fully understood. However, such knowledge is key to identify biomarkers and drug targets to improve prognosis and treatments. Consequently, we performed genome-wide expression profiling of 15 primary HNSSCs compared to corresponding lymph node metastases and non-malignant tissue of the same patient. Differentially expressed genes were bioinformatically exploited applying stringent filter criteria, allowing the discrimination between normal mucosa, primary tumours, and metastases. Signalling networks involved in invasion contain remodelling of the extracellular matrix, hypoxia-induced transcriptional modulation, and the recruitment of cancer associated fibroblasts, ultimately converging into a broad activation of PI3K/AKT-signalling pathway in lymph node metastasis. Notably, when we compared the diagnostic and prognostic value of sequencing data with our expression analysis significant differences were uncovered concerning the expression of the receptor tyrosine kinases EGFR and ERBB2, as well as other oncogenic regulators. Particularly, upregulated receptor tyrosine kinase combinations for individual patients varied, implying potential compensatory and resistance mechanisms against specific targeted therapies. Collectively, we here provide unique transcriptional profiles for disease predictions and comprehensively analyse involved signalling pathways in advanced HNSCC.

Predicting hypoxia status using a combination of contrast-enhanced computed tomography and [18F]-Fluorodeoxyglucose positron emission tomography radiomics features

BACKGROUND AND PURPOSE

Hypoxia is a known prognostic factor in head and neck cancer. Hypoxia imaging PET radiotracers such as 18F-FMISO are promising but not widely available. The aim of this study was therefore to design a surrogate for 18F-FMISO TBRmax based on 18F-FDG PET and contrast-enhanced CT radiomics features, and to study its performance in the context of hypoxia-based patient stratification.

METHODS

121 lesions from 75 head and neck cancer patients were used in the analysis. Patients received pre-treatment 18F-FDG and 18F-FMISO PET/CT scans. 79 lesions were used to train a cross-validated LASSO regression model based on radiomics features, while the remaining 42 were held out as an internal test subset.

RESULTS

In the training subset, the highest AUC (0.873±0.008) was obtained from a signature combining CT and 18F-FDG PET features. The best performance on the unseen test subset was also obtained from the combined signature, with an AUC of 0.833, while the model based on the 90th percentile of 18F-FDG uptake had a test AUC of 0.756.

CONCLUSION

A radiomics signature built from 18F-FDG PET and contrast-enhanced CT features correlates with 18F-FMISO TBRmax in head and neck cancer patients, providing significantly better performance with respect to models based on 18F-FDG PET only. Such a biomarker could potentially be useful to personalize head and neck cancer treatment at centers for which dedicated hypoxia imaging PET radiotracers are unavailable.

In vivo evaluation of the effects of simultaneous inhibition of GLUT-1 and HIF-1α by antisense oligodeoxynucleotides on the radiosensitivity of laryngeal carcinoma using micro 18F-FDG PET/CT

Purpose

Hypoxia-inducible factor 1α (HIF-1α) and glucose transporter-1 (GLUT-1) are two important hypoxic markers associated with the radioresistance of cancers including laryngeal carcinoma. We evaluated whether the simultaneous inhibition of GLUT-1 and HIF-1α expression improved the radiosensitivity of laryngeal carcinoma. We explored whether the expression of HIF-1α and GLUT-1 was correlated with 2′-deoxy-2’-[18F]fluoro-D-glucose (¹⁸F-FDG) uptake and whether ¹⁸F-FDG positron emission tomography-computed tomography (PET/CT) was appropriate for early evaluation of the response of laryngeal carcinoma to targeted treatment in vivo.

Materials and Methods

To verify the above hypotheses, an in vivo model was applied by subcutaneously injecting Hep-2 (2 × 107/mL × 0.2 mL) and Tu212 cells (2 × 107/mL × 0.2 mL) into nude mice. The effects of HIF-1α antisense oligodeoxynucleotides (AS-ODNs) (100 μg) and GLUT-1 AS-ODNs (100 μg) on the radiosensitivity of laryngeal carcinoma were assessed by tumor volume and weight, microvessel density (MVD), apoptosis index (AI) and necrosis in vivo based on a full factorial (2³) design. ¹⁸F-FDG-PET/CT was taken before and after the treatment of xenografts. The relationships between HIF-1α and GLUT-1 expression and ¹⁸F-FDG uptake in xenografts were estimated and the value of ¹⁸F-FDG-PET/CT was assessed after treating the xenografts.

Results

10 Gy X-ray irradiation decreased the weight of Hep-2 xenografts 8 and 12 days after treatment, and the weights of Tu212 xenografts 8 days after treatment. GLUT-1 AS-ODNs decreased the weight of Tu212 xenografts 12 days after treatment. There was a synergistic interaction among the three treatments (GLUT-1 AS-ODNs, HIF-1α AS-ODNs and 10Gy X-ray irradiation) in increasing apoptosis, decreasing MVD, and increasing necrosis in Hep-2 xenografts 8 days after treatment (p < 0.05) and in Tu212 xenografts 12 days after treatment (p < 0.001). Standardized uptake value (tumor/normal tissue)( SUVmaxT/N) did not show a statistically significant correlation with GLUT1 and HIF-1α expression and therapeutic effect (necrosis, apoptosis).

Conclusions

Simultaneous inhibition of HIF-1α and GLUT-1 expression might increase the radiosensitivity of laryngeal carcinoma, decreasing MVD, and promoting apoptosis and necrosis. ¹⁸F-FDG-PET/CT wasn't useful in evaluating the therapeutic effect on laryngeal cancer in this animal study.

Correlation of ADC With Pathological Treatment Response for Radiation Therapy of Pancreatic Cancer

PURPOSE: To investigate the feasibility of using apparent diffusion coefficient (ADC) to assesspathological treatment response in pancreatic ductal adenocarcinoma (PDAC) following neoadjuvant chemoradiation (nCR). MATERIALS/METHODS: MRI and pathological data collected for 25patients with resectable and borderline resectable PDAC following nCR were retrospectively analyzed. Pre- and post-nCR mean ADC values in the tumors were compared using Wilcoxon matched pairs test. Correlation of pathological treatment response and ADC values was assessed using Pearson’s correlation coefficient test and receiver-operating-curve (ROC) analysis. RESULTS: The average mean and standard deviation (SD) of the ADC values for all the patients analyzed were significantly higher in post-nCR (1.667±0.161×10^-3) compared with those prior to nCR (1.395±0.136×10^-3 mm²/sec), (P<0.05). The mean ADC values after nCR were significantly correlated with the pathological responses (r=-0.5172); P=0.02. The area under the curve (AUC) of the ADC values for differentiating G1, G2 and G3 pathological responses, using ROC analysis, was found to be 0.6310 and P=0.03. CONCLUSION: Changes of pre- and post-treatment ADC values significantly correlated with pathological treatment response for PDAC patients treated with chemoradiation therapy, indicating that the ADC could be used to assesstreatment response for PDAC.

Tricyclic Antidepressants Modulate Stressed Mitochondria in Glioblastoma Multiforme Cells

A common feature of solid tumors, including glioblastoma multiforme (GBM), is mitochondrial dysfunction. However, it is reported that the current standard of anti-GBM therapies may potentiate mitochondrial damage and, in effect, support the aggressive character of cancer. As mitochondria are implicated in the modulation of cellular drug sensitivity and chemoresistance mechanisms, activation-stressed mitochondria in GBM cells may represent a new target for anti-GBM therapy that is nontoxic for normal cells.

METHODS

As mitochondria are possible targets for antidepressant drugs used as adjuvant therapy in patients with GBM, we examined their influence on mitochondrial volume and activity, reactive oxygen species level, extracellular lactate concentration, and p65 NF-κB gene expression in GBM cells.

RESULTS

Our investigation showed, for the first time, that tricyclic antidepressants, imipramine and amitriptyline, partially reverse GBM abnormalities.

CONCLUSION

In the light of reported studies, the mitochondrial disturbance observed in glioma cells is a dynamic process that can be reversed or silenced. Moreover, imipramine and amitriptyline are attractive cellular metabolic modulators and can potentially be used to restoring a proper function of mitochondria in GBM cells.

Current relevance of hypoxia in head and neck cancer

Head and Neck cancer (HNC) is a complex mix of cancers and one of the more common cancers with a relatively poor prognosis. One of the factors that may assist us in predicting survival and allow us to adjust our treatment strategies is the presence of tumor hypoxia. In this overview we aim to evaluate the current evidence and potential clinical relevance of tumor hypoxia in head and neck cancer according to an extensive search of current literature.An abundance of evidence and often contradictory evidence is found in the literature. Even the contradictory evidence and comparisons are difficult to judge as criteria and methodologies differ greatly, furthermore few prospective observational studies exist for verification of the pre-clinical studies. Despite these discrepancies there is clear evidence of associations between prognosis and poor tumor oxygenation biomarkers such as HIF-1α, GLUT-1 and lactate, though these associations are not exclusive. The use of genetic markers is expanding and will probably lead to significantly more and complex evidence. The lack of oxygenation in head and neck tumors is of paramount importance for the prediction of treatment outcomes and prognosis. Despite the wide array of conflicting evidence, the drive towards non-invasive prediction of tumor hypoxia should continue.

Antidepressant drugs can modify cytotoxic action of temozolomide

Cancer patients often require antidepressant treatment due to comorbid depressive disorder. However, recent studies have demonstrated that antidepressant drugs affect the efficacy of chemotherapy and promote progression of cancer. Apart from the main mood-improving effect, antidepressant drugs also produce analgesic, anxiolytic, hypnotic and pro-cognitive actions. Patients suffering from brain cancer constitute the greatest percentage of depressive cancer patients. However, vital safety and efficacy issues related to combined therapy with temozolomide, the first-line cytostatic in patients diagnosed with glioblastoma multiforme, and antidepressant drugs have yet to be addressed. The aim of the present studies was to evaluate the effect of three antidepressant drugs (imipramine, fluoxetine and tranylcypromine) on the cytotoxic efficacy of temozolomide on T98G cells, a human glioblastoma cell line. In our experiments, we used a complex experimental in vitro system to mimic the instability of a tumour's oxygen supply, thereby reproducing conditions that occur inside the tumour. The effect of the interaction between temozolomide and antidepressant drugs on viability, apoptosis and intensity of divisions of glioblastoma cells was evaluated under different oxygen conditions. The results of our studies demonstrated that imipramine and tranylcypromine reduced the cytotoxic efficacy of temozolomide under some oxygen conditions while fluoxetine did not demonstrate such effects.

Fluorine-18 radiolabeling of a nitrophenyl sulfoxide and its evaluation in an SK-RC-52 model of tumor hypoxia

The significance of imaging hypoxia with the positron emission tomography ligand [(18) F]FMISO has been demonstrated in a variety of cancers. However, the slow kinetics of [(18) F]FMISO require a 2-h delay between tracer administration and patient scanning. Labeled chloroethyl sulfoxides have shown faster kinetics and higher contrast than [(18) F]FMISO in a rat model of ischemic stroke. However, these nitrogen mustard analogues are unsuitable for routine production and use in humans. Here, we report on the synthesis and in vitro and in vivo evaluation of a novel sulfoxide, which contains an ester moiety for hydrolysis and subsequent trapping in hypoxic cells. Non-decay corrected yields of radioactivity were 1.18 ± 0.24% (n = 27, 2.5 ± 0.5% decay corrected radiochemical yield) based on K[(18) F]F. The radiotracer did not show any defluorination and did not undergo metabolism in an in vitro assay using S9 liver fractions. Imaging studies using an SK-RC-52 tumor model in BALB/c nude mice have revealed that [(18) F]1 is retained in hypoxic tumors and has similar hypoxia selectivity to [(18) F]FMISO. Because of a three times faster clearance rate than [(18) F]FMISO from normoxic tissue, [(18) F]1 has emerged as a promising new radiotracer for hypoxia imaging.

Assessment of hypoxic subvolumes in laryngeal cancer with (18)F-fluoroazomycinarabinoside ((18)F-FAZA)-PET/CT scanning and immunohistochemistry

BACKGROUND AND PURPOSE

(18)F-fluoroazomycinarabinoside ((18)F-FAZA) is a promising hypoxia radiopharmaceutical agent with outstanding biokinetic parameters. We aimed to determine the accuracy of (18)F-FAZA-PET/CT scan in detecting hypoxic regions within the tumor using immunohistochemical markers in a pilot study.

PATIENTS AND METHODS

Eleven patients with primary or recurrent laryngeal squamous cell carcinoma were indicated for total laryngectomy (TLE). Patients underwent (18)F-FAZA-PET/CT scan before TLE. Hypoxic regions inside the laryngeal tumor were determined. After TLE, regions with high uptake on (18)F-FAZA-PET scan were selected for immunohistochemical examination for exogenous (pimonidazole) and endogenous (HIF1α, CA-IX and GLUT-1) hypoxia markers. To assess the accuracy of (18)F-FAZA-PET scanning, radiopharmacon accumulation was related with immunohistochemical expression of hypoxia markers.

RESULTS

Inter- and intratumoral heterogeneity of tumor hypoxia was observed on (18)F-FAZA-PET scan. Nine of the eleven tumors were hypoxic with (18)F-FAZA-PET. Hypoxia could also be detected with pimonidazole, HIF1α, CA-IX and GLUT-1 expression in some tumors. No clear association was observed between (18)F-FAZA uptake and hypoxia markers.

CONCLUSIONS

This pilot study could not prove the accuracy of (18)F-FAZA-PET in determining hypoxic subvolumes in laryngeal cancer. Further study is required to investigate the benefit of (18)F-FAZA-PET imaging in radiotherapy planning.

The clinical importance of assessing tumor hypoxia: relationship of tumor hypoxia to prognosis and therapeutic opportunities

Tumor hypoxia is a well-established biological phenomenon that affects the curability of solid tumors, regardless of treatment modality. Especially for head and neck cancer patients, tumor hypoxia is linked to poor patient outcomes. Given the biological problems associated with tumor hypoxia, the goal for clinicians has been to identify moderately to severely hypoxic tumors for differential treatment strategies. The "gold standard" for detecting and characterizing of tumor hypoxia are the invasive polarographic electrodes. Several less invasive hypoxia assessment techniques have also shown promise for hypoxia assessment. The widespread incorporation of hypoxia information in clinical tumor assessment is severely impeded by several factors, including regulatory hurdles and unclear correlation with potential treatment decisions. There is now an acute need for approved diagnostic technologies for determining the hypoxia status of cancer lesions, as it would enable clinical development of personalized, hypoxia-based therapies, which will ultimately improve outcomes. A number of different techniques for assessing tumor hypoxia have evolved to replace polarographic pO2 measurements for assessing tumor hypoxia. Several of these modalities, either individually or in combination with other imaging techniques, provide functional and physiological information of tumor hypoxia that can significantly improve the course of treatment. The assessment of tumor hypoxia will be valuable to radiation oncologists, surgeons, and biotechnology and pharmaceutical companies who are engaged in developing hypoxia-based therapies or treatment strategies.

Dual tracer evaluation of dynamic changes in intratumoral hypoxic and proliferative states after radiotherapy of human head and neck cancer xenografts using radiolabeled FMISO and FLT

BACKGROUND

Radiotherapy is an important treatment strategy for head and neck cancers. Tumor hypoxia and repopulation adversely affect the radiotherapy outcome. Accordingly, fractionated radiotherapy with dose escalation or altered fractionation schedule is used to prevent hypoxia and repopulation. 18F-fluoromisonidazole (FMISO) and 18F-fluorothymidine (FLT) are noninvasive markers for assessing tumor hypoxia and proliferation, respectively. Thus, we evaluated the dynamic changes in intratumoral hypoxic and proliferative states following radiotherapy using the dual tracers of 18F-FMISO and 3H-FLT, and further verified the results by immunohistochemical staining of pimonidazole (a hypoxia marker) and Ki-67 (a proliferation marker) in human head and neck cancer xenografts (FaDu).

METHODS

FaDu xenografts were established in nude mice and assigned to the non-radiation-treated control and two radiation-treated groups (10- and 20-Gy). Tumor volume was measured daily. Mice were sacrificed 6, 24, and 48 hrs and 7 days after radiotherapy. 18F-FMISO, and 3H-FLT and pimonidazole were injected intravenously 4 and 2 hrs before sacrifice, respectively. Intratumoral 18F-FMISO and 3H-FLT levels were assessed by autoradiography. Pimonidazole and Ki-67 immunohistochemistries were performed.

RESULTS

In radiation-treated mice, tumor growth was significantly suppressed compared with the control group, but the tumor volume in these mice gradually increased with time. Visual inspection showed that intratumoral 18F-FMISO and 3H-FLT distribution patterns were markedly different. Intratumoral 18F-FMISO level did not show significant changes after radiotherapy among the non-radiation-treated control and radiation-treated groups, whereas 3H-FLT level markedly decreased to 59 and 45% of the non-radiation-treated control at 6 hrs (p<0.0001) and then gradually increased with time in the 10- and 20-Gy-radiation-treated groups. The pimonidazole-positive hypoxic areas were visually similar in both the non-radiation-treated control and radiation-treated groups. No significant differences were observed in the percentage of pimonidazole-positive cells and Ki-67 index.

CONCLUSION

Intratumoral 18F-FMISO level did not change until 7 days, whereas 3H-FLT level markedly decreased at 6 hrs and then gradually increased with time after a single dose of radiotherapy. The concomitant monitoring of dynamic changes in tumor hypoxia and proliferation may provide important information for a better understanding of tumor biology after radiotherapy and for radiotherapy planning, including dose escalation and altered fractionation schedules.

Hypoxia in head and neck cancer in theory and practice: a PET-based imaging approach

Hypoxia plays an important role in tumour recurrence among head and neck cancer patients. The identification and quantification of hypoxic regions are therefore an essential aspect of disease management. Several predictive assays for tumour oxygenation status have been developed in the past with varying degrees of success. To date, functional imaging techniques employing positron emission tomography (PET) have been shown to be an important tool for both pretreatment assessment and tumour response evaluation during therapy. Hypoxia-specific PET markers have been implemented in several clinics to quantify hypoxic tumour subvolumes for dose painting and personalized treatment planning and delivery. Several new radiotracers are under investigation. PET-derived functional parameters and tracer pharmacokinetics serve as valuable input data for computational models aiming at simulating or interpreting PET acquired data, for the purposes of input into treatment planning or radio/chemotherapy response prediction programs. The present paper aims to cover the current status of hypoxia imaging in head and neck cancer together with the justification for the need and the role of computer models based on PET parameters in understanding patient-specific tumour behaviour.

Head and neck tumor hypoxia imaging by 18F-fluoroazomycin-arabinoside (18F-FAZA)-PET: a review

Tumor hypoxia is known to be associated with poor clinical outcome; therefore, patients with hypoxic tumors might benefit from more intensive treatment approaches. This is particularly true for patients with head and neck cancer. Pretreatment assessment of hypoxia in tumors would be desirable, not only to predict prognosis but also to select patients for more aggressive treatment.As an alternative to the invasive polarographic needle electrode method, there is the possibility of using PET with radiopharmaceuticals visualizing hypoxia. Most hypoxia imaging studies on head and cancer have been performed using F-labeled fluoromisonidazole (F-FMISO). A chemically related molecule, F-fluoroazomycin-arabinoside (F-FAZA), seems to have superior kinetic properties and may therefore be the radiopharmaceutical of choice.This minireview summarizes the published literature on animal and human F-FAZA PET studies. Furthermore, future perspectives on how individualized treatment could be applied in patients with hypoxic head and neck tumors are discussed, for instance, the use of hypoxia sensitizers or special intensity-modulated radiation therapy techniques achieving tumor subvolume dose escalation.

Expression of hypoxic signaling markers in head and neck squamous cell carcinoma and its clinical significance

Hypoxia is a consistent finding in fast-growing tumors; it contributes to tumor progression and therapeutic responses. We explored the expression of hypoxia-associated biomarkers in head and neck squamous cell carcinoma (HNSCC) to assess their relationship with clinical factors in HNSCC. In total, 90 patients with HNSCC were enrolled. Expression of HIF-1α, HSP70, HSP90, VEGF, IGF-1R, and P16 was investigated by immunohistochemistry. Their correlations with clinical factors, including location of primary sites, T stage, N stage, M stage, HPV status, primary treatment success/failure, recurrences, disease-free survival (DFS), and overall survival, were analyzed. HIF-1α, HPS70, HPS90, VEGF, and IGF-1R were positive in 33 of 89 (37.1 %), 62 of 87 (71.3 %), 83 of 89 (93.3 %), 41 of 87 (47.1 %), and 50 of 56 (89.3 %) cases, respectively. Expression levels of some of these markers were correlated. High HIF-1α or HSP 70 correlated with poor DFS, and expression of HSP70 correlated with LN metastasis. HPV-related carcinomas showed high HSP 70 and IGF-1R expression. Hypoxia-associated proteins were highly expressed and associated with aggressive clinical features in HNSCC. Expression of HIF-1α or HSP70 can be considered poor prognostic indicator in HNSCC. Our results suggest that hypoxic signaling is activated in HNSCC, especially in HPV-related tumors.

Head and neck cancer: from anatomy to biology

The 20th century saw great advances in anatomy-based (surgery and radiotherapy) and chemotherapy approaches for treating head and neck squamous cell carcinoma (HNSCC) and improving quality of life (QoL). However, despite these advances, the survival rate in HNSCC remains at ∼50%. Front-line treatments often cause severe toxicity and debilitating long-term impacts on QoL. In recent decades, dramatic advances have been made in our knowledge of fundamental tumor biology and signaling pathways that contribute to oncogenesis and cancer progression. These insights are presenting unprecedented opportunities to develop more effective and less toxic treatments that are specific to particular molecular targets. This review discusses some of the major, potentially targetable, molecular pathways associated with head and neck carcinogenesis. We present the general mechanism underlying the functional components for each signaling pathway, discuss how these components are aberrantly regulated in HNSCC and describe their potential as therapeutic targets. We have restricted our discussion to "drug-able targets" such as oncogenes including those associated with HPV, tumor hypoxia and microRNAs and present these changes in the context of HNSCC patient care. The specific targeting of these pathways to achieve cancer control/remission and reduce toxicity is now challenging conventional treatment paradigms in HNSCC. This new "biologic era" is transforming our ability to target causal pathways and improve survival outcomes in HNSCC.

Molecular-targeted therapy hypoxia in head and neck squamous cell carcinoma patients

Despite advances in surgical techniques, radiotherapy, and chemotherapy, 5-year survival in patients with late-stage head and neck squamous cell carcinoma (HNSCC) have not improved significantly over the past decades. HNSCC tumors are commonly associated with hypoxia, which is characterized by an acute and/or chronic decline in oxygen tension. Hypoxia is an important cancer-aggravating microenvironmental factor that contributes to malignant behaviors such as acquisition of antiapoptotic ability by cancer cells and tumor progression, invasion, metastasis, and resistance to chemotherapy and radiotherapy. Numerous studies have assessed tumor hypoxia and identified molecular markers that are promising therapeutic targets in HNSCC cases. Moreover, investigators have suggested a number of molecular strategies to target cell processes critical to hypoxia development in HNSCC patients via the direct or indirect regulation of hypoxia-inducible factor-1α expression in cancer cells. In this review, we described recent advances in the identification and development of molecular-targeted therapy targeting hypoxia in HNSCC patients.

Hypoxia in head and neck squamous cell carcinoma

Hypoxia is a common feature in most of the solid tumors including head and neck squamous cell carcinoma (HNSCC). Hypoxia reflects the imbalance between oxygen consumption by the rapidly proliferating cancer cells and the insufficient oxygen delivery due to poor vascularization and blood supply. The hypoxic microenvironment in the HNSCC contributes to the development of aggressive carcinoma phenotype with high metastatic rate, resistance to therapeutic agents, and higher tumor recurrence rates, leading to low therapeutic efficiency and poor outcome. To overcome the therapeutic resistance due to hypoxia and improving the prognosis of the HNSCC patients, many approaches have been examined in laboratory studies and clinical trials. In this short paper, we discuss the mechanisms involved in the resistance of radiotherapy and chemotherapy in hypoxic condition. We also exploit the molecular mechanisms employed by the HNSCC cells to adapt the hypoxic condition and their tumorigenic role in head and neck, as well as the strategies to overcome hypoxia-induced therapeutic resistance.

From tumor hypoxia to cancer progression: the implications of hypoxia-inducible factor-1 expression in cancers

Hypoxia, defined as a decrease of tissue oxygen levels, represents a fundamental pathophysiological condition in the microenvironment of solid tumors. Tumor hypoxia is known to be associated with radio/chemo-resistance and metastasis that eventually lead to cancer progression contributing to poor prognosis in cancer patients. Among transcription factors that accumulated under hypoxic conditions, hypoxia-inducible factor-1 (HIF-1) is a master transcription factor that has received the most intense attention in this field of research due to its capacity to modulate several hundred genes. With a clearer understanding of the HIF-1 pathway, efforts are directed at manipulation of this complex genetic process in order to ultimately decrease cellular HIF-1 levels. Some novel agents have been shown to have HIF-1 inhibition activity through a variety of molecular mechanisms and have provided promising results in the preclinical setting.

Value of three-dimensional power Doppler to predict clinical and histological response to neoadjuvant chemotherapy in locally advanced cervical carcinoma

OBJECTIVE

Platinum-based neoadjuvant chemotherapy followed by radical hysterectomy is an alternative therapeutic strategy for locally advanced cervical carcinoma but variables used to predict chemotherapy response are not well defined. We investigated the potential of three-dimensional (3D) power Doppler in predicting response to neoadjuvant chemotherapy.

METHODS

We enrolled 61 eligible patients with locally advanced cervical carcinoma who underwent neoadjuvant chemotherapy followed by surgery or radiation. Before the initial chemotherapy, we measured 3D power Doppler vascular indices, including vascularization index (VI), flow index (FI) and vascularization flow index (VFI), of the whole cervical carcinoma. We also measured two-dimensional (2D) hemodynamic parameters, such as resistance index and pulsatility index, at three random spots inside the tumor. The associations of all parameters with clinical and histological responses to chemotherapy were evaluated through univariable and multiple logistic regression analysis.

RESULTS

The clinical and histological response rates to chemotherapy were 70.5% and 70.7%, respectively. Univariable logistic regression analysis showed that VI, FI and VFI were significantly higher in clinical responders than in non-responders (P < 0.05), and that FI was significantly higher in histological responders (P = 0.012). Multiple logistic regression analysis showed that FI was the only significant factor associated with both clinical and histological responses. The best FI cut-off values were 35.3 and 37.3 for clinical response and histological response, respectively (with sensitivity 86.0% and 73.2%, and specificity 72.2% and 64.7%). Interestingly, none of the 2D hemodynamic parameters was significantly correlated with either response.

CONCLUSION

FI is a potential marker for predicting both clinical and histological responses to chemotherapy in patients with locally advanced cervical carcinoma.

Tumor-associated carbonic anhydrase XII is linked to the growth of primary oral squamous cell carcinoma and its poor prognosis

The pattern of protein expression in tumors is under the influence of nutrient stress, hypoxia, and low pH, which determines the survival of neoplastic cells and the development of tumors. Carbonic anhydrase (CA) XII is a transmembrane enzyme that catalyzes the reversible hydration of cell-generated carbon dioxide into protons and bicarbonate. Hypoxic conditions activate its transcription and translation, and enhanced expression is often present in several types of tumors. However, CA XII expression in oral squamous cell carcinoma (OSCC) and its correlation with patients' prognosis have not been investigated so far. In this study, we detected the expression of CA XII in 264 patients with OSCC using tissue microarrays (TMAs), and evaluated its correlation with clinicopathologic factors and disease prognosis. CA XII expression was present in 185/264 (70%) cases and was associated with more-advanced clinical stages (p=0.003), a larger tumor size (p<0.001), and postoperative recurrence (p=0.047), but was not associated with positive lymph node metastasis or distal metastasis. Importantly, CA XII expression was correlated with a poorer patient prognosis in a univariate (p=0.034, log-rank test) survival analysis. According to our results, the expression of CA XII in OSCC samples can predict the progression of OSCC and survival of OSCC patients.

The role of PET imaging in overcoming radiobiological challenges in the treatment of advanced head and neck cancer

PURPOSE

Despite the large variety of treatment methods available for the management of advanced head and neck carcinomas, these tumours remain highly challenging due to their aggressiveness and complex anatomical location. Among the treatment challenges associated with head and neck cancers, hypoxia and tumour repopulation during treatment are, most likely, the main reason for locoregional treatment failure. Whilst the number of techniques and predictive assays designed to assess the oxygenation status or the proliferative ability of tumours is rather large, they all come with drawbacks which limit their implementation as routine clinical procedures. Latest developments in the field of nuclear medicine have opened the road to new possibilities in functional imaging, thus overcoming some of the confines imposed by the more conventional techniques.

MATERIALS AND METHODS

The current paper presents the role of PET imaging as a quantitative evaluation tool for hypoxia status and proliferative ability of advanced head and neck tumours. Traditional as well as novel radioisotopes with high affinity towards hypoxia and proliferative tumour activity are presented and their pre-clinical/clinical results analysed.

RESULTS

While the number of clinical studies which aimed to validate novel radiotracers for head and neck cancer is limited, a number of results show promising correlation between uptake/marker activity and treatment outcome.

CONCLUSION

There is need for further studies and well designed clinical trials to obtain more conclusive results.

Increased glucose metabolism by FDG-PET correlates with reduced tumor angiogenesis in oral squamous cell carcinoma

Hypoxia is known to have been related with angiogenesis and glycolysis, and may have an influence on tumor treatment effect. Because glucose utilization is higher in malignant cells than that in normal cells, dynamic glucose metabolism of tumor has been evaluated by means of [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET). To investigate the significance of tumor vascularization in oral squamous cell carcinoma, we compared tumor angiogenesis with the FDG-PET findings. Twenty patients underwent FDG-PET. For the quantitative evaluation of FDG uptake in each tumor, the mean standardized uptake value (SUV) was calculated. Microvessel structures labeled with CD34 antigen were investigated in pretreatment biopsy specimens. Using an image analyzer, we calculated the following microvessel parameters: the ratio of the total number of microvessels (TN) to tumor area (TA), the ratio of the total microvessel perimeter (TP) to the TA, and the ratio of the tumor tissue area more than 150 μm distant from each microvessel (hypoxic ratio, %). The SUV was compared with the above parameters. Simple regression analysis revealed a statistical significance between the SUV and the TN:TA ratio (p = 0.046), as well as between the SUV and the TP:TA ratio (p = 0.0206). The SUV was found to be inversely related to the TN:TA and TP:TA ratios. Elevated glucose metabolism assessed by FDG-PET correlated with reduced vascularization. Higher glucose metabolism might therefore reflect a state of hypoxia.

Generation and characterization of the first inhibitory antibody targeting tumour-associated carbonic anhydrase XII

The carbonic anhydrases (CAs) constitute a family of almost ubiquitous enzymes of significant importance for many physiological and pathological processes. CAs reversely catalyse the conversion of CO(2) + H(2)O to HCO(3) (-) and H(+), thereby contributing to the regulation of intracellular pH. Above all, CAs are of key importance for cells that perform glycolysis that inevitably leads to the intracellular accumulation of lactate. CA XII is a plasma membrane-associated isoform of the enzyme, which is induced by hypoxia and oestrogen and, consequently, expressed at high levels on various types of cancer and, intriguingly, on cancer stem cells. The enzyme is directly involved in tumour progression, and its inhibition has an anti-tumour effect. Apart from its role in carcinogenesis, the enzyme contributes to various other diseases like glaucoma and arteriosclerotic plaques, among others. CA XII is therefore regarded as promising target for specific therapies. We have now generated the first monoclonal antibody (6A10) that binds to the catalytic domain of CA XII on vital tumour cells and inhibits CA XII enzyme activity at nanomolar concentrations and thus much more effective than acetazolamide. In vitro results demonstrate that inhibition of CA XII by 6A10 inhibits the growth of tumour cells in 3-dimensional structures. In conclusion, we generated the first specific and efficient biological inhibitor of tumour-associated CA XII. This antibody may serve as a valuable tool for in vivo diagnosis and adjuvant treatment of different types of cancer.

Hypoxia-induced autophagic response is associated with aggressive phenotype and elevated incidence of metastasis in orthotopic immunocompetent murine models of head and neck squamous cell carcinomas (HNSCC)

Hypoxia confers resistance to chemoradiation therapy and promotes metastasis in head and neck squamous cell carcinomas (HNSCC). We investigated the effects of hypoxia in tumor phenotype using immunocompetent murine HNSCC models. Balb/c mice were injected intraorally with murine squamous cell carcinoma cells LY-2 and B4B8. Intratumoral hypoxia fraction was evaluated by the immunohistochemical detection of hypoxic probe pimonidazole and carbonic anhydrase IX (CAIX). Tumor cell apoptosis and autophagy in hypoxic areas of these tumors were examined immunohistochemically. Hypoxia-induced apoptotic and autophagic responses in vitro were examined by treating LY2 cells with CoCl(2). B4B8 tumors exhibited a non-aggressive phenotype characterized by its slow growth rate and the lack of metastatic spread. LY2 tumors demonstrated an aggressive phenotype characterized by rapid growth rate with regional and distant metastasis. Intratumoral hypoxia fraction in B4B8 tumors was significantly lower than in LY2 tumors. The hypoxic areas in B4B8 tumors exhibited increased apoptosis rate than that of LY2 tumors. In contrast, the hypoxic areas in LY2 tumors revealed autophagy. The induction of hypoxia in vitro elicited autophagy and not apoptosis in LY2 cells. The induction of autophagy coupled with blockage of apoptosis in hypoxic areas promotes tumor cell survival and confers aggressive phenotype in immunocompetent murine HNSCC models.

Irradiation-dependent effects on tumor perfusion and endogenous and exogenous hypoxia markers in an A549 xenograft model

PURPOSE

Hypoxia is a major determinant of tumor radiosensitivity, and microenvironmental changes in response to ionizing radiation (IR) are often heterogenous. We analyzed IR-dependent changes in hypoxia and perfusion in A549 human lung adenocarcinoma xenografts.

MATERIALS AND METHODS

Immunohistological analysis of two exogenously added chemical hypoxic markers, pimonidazole and CCI-103F, and of the endogenous marker Glut-1 was performed time dependently after IR. Tumor vessels and apoptosis were analyzed using CD31 and caspase-3 antibodies. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and fluorescent beads (Hoechst 33342) were used to monitor vascular perfusion.

RESULTS

CCI-103F signals measuring the fraction of hypoxic areas after IR were significantly decreased by approximately 50% when compared with pimonidazole signals, representing the fraction of hypoxic areas from the same tumors before IR. Interestingly, Glut-1 signals were significantly decreased at early time point (6.5 h) after IR returning to the initial levels at 30.5 h. Vascular density showed no difference between irradiated and control groups, whereas apoptosis was significantly induced at 10.5 h post-IR. DCE-MRI indicated increased perfusion 1 h post-IR.

CONCLUSIONS

The discrepancy between the hypoxic fractions of CCI-103F and Glut-1 forces us to consider the possibility that both markers reflect different metabolic alterations of tumor microenvironment. The reliability of endogenous markers such as Glut-1 to measure reoxygenation in irradiated tumors needs further consideration. Monitoring tumor microvascular response to IR by DCE-MRI and measuring tumor volume alterations should be encouraged.

HIF-2alpha-mediated activation of the epidermal growth factor receptor potentiates head and neck cancer cell migration in response to hypoxia

Despite their individual key roles in promoting head and neck squamous cell carcinoma (HNSCC) progression and treatment resistance, little is known about the impact of intratumoral hypoxia on the activity of the epidermal growth factor receptor (EGFR) signaling pathway in this cancer type. Here, we show that in highly EGFR-expressing HNSCC cells, hypoxic stress triggers the activation of the EGFR and downstream targets, including Akt and phospholipase C (PLC) gamma1. In support of these findings, we also demonstrate that EGFR activation takes place within hypoxic foci in a subset of human HNSCC tissues. Whereas hypoxia had no major effect on HNSCC cell proliferation, it markedly altered tumor cell shape by inducing morphological changes consistent with a more spindle-shaped, fibroblast-like morphology together with an enhanced migratory capacity. We found that hypoxia-induced EGFR activation and cell migration could be prevented by targeting EGFR signaling with the tyrosine kinase inhibitor tyrphostin, the phospholipase C inhibitor U73122, or by inhibiting the expression of the alpha subunit of hypoxia-inducible factor 2 via RNA interference or the topoisomerase II inhibitor etoposide. Our results position hypoxia-inducible factor-2alpha as a novel regulator of EGFR activation under low oxygen conditions, and suggest that hypoxia-induced EGFR signaling may promote a more aggressive phenotype in a fraction of HNSCC tumors. Because EGFR continues in the forefront as a highly attractive target in clinical oncology, further studies are warranted to define the mechanistic and therapeutic implications of the hypoxic response relative to the EGFR signaling pathway in head and neck cancer.

Hypoxic tumors and their effect on immune cells and cancer therapy

The abnormal decrease or the lack of oxygen supply to cells and tissues is called hypoxia. This condition is commonly seen in various diseases such as rheumatoid arthritis and atherosclerosis, also in solid cancers. Pre-clinical and clinical studies have shown that hypoxic cancers are extremely aggressive, resistant to standard therapies (chemotherapy and radiotherapy), and thus very difficult to eradicate. Hypoxia affects both the tumor and the immune cells via various pathways. This review summarizes the most common effects of hypoxia on immune cells that play a key role in the anti-tumor response, the limitation of current therapies, and the potential solutions that were developed for hypoxic malignancies.

Potential use of cetrimonium bromide as an apoptosis-promoting anticancer agent for head and neck cancer

A potential therapeutic agent for human head and neck cancer (HNC), cetrimonium bromide (CTAB), was identified through a cell-based phenotype-driven high-throughput screen (HTS) of 2000 biologically active or clinically used compounds, followed by in vitro and in vivo characterization of its antitumor efficacy. The preliminary and secondary screens were performed on FaDu (hypopharyngeal squamous cancer) and GM05757 (primary normal fibroblasts), respectively. Potential hit compounds were further evaluated for their anticancer specificity and efficacy in combination with standard therapeutics on a panel of normal and cancer cell lines. Mechanism of action, in vivo antitumor efficacy, and potential lead compound optimizations were also investigated. In vitro, CTAB interacted additively with gamma radiation and cisplatin, two standard HNC therapeutic agents. CTAB exhibited anticancer cytotoxicity against several HNC cell lines, with minimal effects on normal fibroblasts; a selectivity that exploits cancer-specific metabolic aberrations. The central mode of cytotoxicity was mitochondria-mediated apoptosis via inhibition of H(+)-ATP synthase activity and mitochondrial membrane potential depolarization, which in turn was associated with reduced intracellular ATP levels, caspase activation, elevated sub-G(1) cell population, and chromatin condensation. In vivo, CTAB ablated tumor-forming capacity of FaDu cells and delayed growth of established tumors. Thus, using an HTS approach, CTAB was identified as a potential apoptogenic quaternary ammonium compound possessing in vitro and in vivo efficacy against HNC models.

Nitroimidazole conjugates of bis(thiosemicarbazonato)64Cu(II) - Potential combination agents for the PET imaging of hypoxia

Combination agents comprising two different pharmacophores with the same biological target have the potential to show additive or synergistic activity. Bis(thiosemicarbazonato)copper(II) complexes (e.g. (64)Cu-ATSM) and nitroimidazoles (e.g. (18)F-MISO) are classes of tracer used for the delineation of tumor hypoxia by positron emission tomography (PET). Three nitroimidazole-bis(thiosemicarbazonato)copper(II) conjugates were produced in order to investigate their potential as combination hypoxia imaging agents. Two were derived from the known bifunctional bis(thiosemicarbazone) H(2)ATSM/A and the third from the new precursor diacetyl-2-(4-N-methyl-3-thiosemicarbazone)-3-(4-N-ethylamino-3-thiosemicarbazone) - H(2)ATSM/en. Oxygen-dependent uptake studies were performed using the (64)Cu radiolabelled complexes in EMT6 carcinoma cells. All the complexes displayed appreciable hypoxia selectivity, with the nitroimidazole conjugates displaying greater selectivity than a simple propyl derivative used as a control. Participation of the nitroimidazole group in the trapping mechanism is indicated by the increased hypoxic uptake of the 2- vs. the 4-substituted (64)Cu-ATSM/A derivatives. The 2-nitroimidazole derivative of (64)Cu-ATSM/en demonstrated superior hypoxia selectivity to (64)Cu-ATSM over the range of oxygen concentrations tested. Biodistribution of the radiolabelled 2-nitroimidazole conjugates was carried out in EMT6 tumor-bearing mice. The complexes showed significantly different uptake trends in comparison to each other and previously studied Cu-ATSM derivatives. Uptake of the Cu-ATSM/en conjugate in non-target organs was considerably lower than for derivatives based on Cu-ATSM/A.

Prospective trial incorporating pre-/mid-treatment [18F]-misonidazole positron emission tomography for head-and-neck cancer patients undergoing concurrent chemoradiotherapy

PURPOSE

To report the results from a prospective study of a series of locoregionally advanced head-and-neck cancer patients treated with platinum-based chemotherapy and intensity-modulated radiotherapy and to discuss the findings of their pre-/mid-treatment [(18)F]-misonidazole ((18)F-FMISO) positron emission tomography (PET) scans.

METHODS AND MATERIALS

A total of 28 patients agreed to participate in this study. Of these 28 patients, 20 (90% with an oropharyngeal primary cancer) were able to undergo the requirements of the protocol. Each patient underwent four PET scans: one pretreatment fluorodeoxyglucose PET/computed tomography scan, two pretreatment (18)F-FMISO PET/computed tomography scans, and a third (18)F-FMISO PET (mid-treatment) scan performed 4 weeks after the start of chemoradiotherapy. The (18)F-FMISO PET scans were acquired 2-3 h after tracer administration. Patients were treated with 2-3 cycles of platinum-based chemotherapy concurrent with definitive intensity-modulated radiotherapy.

RESULTS

A heterogeneous distribution of (18)F-FMISO was noted in the primary and/or nodal disease in 90% of the patients. Two patients had persistent detectable hypoxia on their third mid-treatment (18)F-FMISO PET scan. One patient experienced regional/distant failure but had no detectable residual hypoxia on the mid-treatment (18)F-FMISO PET scan.

CONCLUSION

Excellent locoregional control was observed in this series of head-and-neck cancer patients treated with concurrent platinum-based chemotherapy and intensity-modulated radiotherapy despite evidence of detectable hypoxia on the pretreatment (18)F-FMISO PET/computed tomography scans of 18 of 20 patients. In this prospective study, neither the presence nor the absence of hypoxia, as defined by positive (18)F-FMISO findings on the mid-treatment PET scan, correlated with patient outcome. The results of this study have confirmed similar results reported previously.