Radiosensitivity and effect of hypoxia in HPV positive head and neck cancer cells

Similar cisplatin sensitivity of HPV-positive and -negative HNSCC cell lines

Patients with HPV-positive head and neck squamous cell carcinoma (HNSCC) show better survival rates than those with HPV-negative HNSCC. While an enhanced radiosensitivity of HPV-positive tumors is clearly evident from single modality treatment, cisplatin is never administered as monotherapy and therefore its contribution to the enhanced cure rates of HPV-positive HNSCC is not known. Both cisplatin and radiotherapy can cause severe irreversible side effects and therefore various clinical studies are currently testing deintensified regimes for patients with HPV-positive HNSCC. One strategy is to omit cisplatin-based chemotherapy or replace it by less toxic treatments but the risk assessment of these approaches remains difficult. In this study we have compared the cytotoxic effects of cisplatin in a panel of HPV-positive and -negative HNSCC cell lines alone and when combined with radiation.

While cisplatin-treated HPV-positive strains showed a slightly stronger inhibition of proliferation, there was no difference regarding colony formation. Cellular responses to the drug, namely cell cycle distribution, apoptosis and γH2AX-induction did not differ between the two entities but assessment of cisplatin-DNA-adducts suggests differences regarding the mechanisms that determine cisplatin sensitivity. Combining cisplatin with radiation, we generally observed an additive but only in a minority of strains from both entities a clear synergistic effect on colony formation. In summary, HPV-positive and -negative HNSCC cells were equally sensitive to cisplatin. Therefore replacing cisplatin may be feasible but the substituting agent should be of similar efficacy in order not to jeopardize the high cure rates for HPV-positive HNSCC.

Induction of dormancy in hypoxic human papillomavirus-positive cancer cells

Oncogenic human papillomaviruses (HPVs) are closely linked to major human malignancies, including cervical and head and neck cancers. It is widely assumed that HPV-positive cancer cells are under selection pressure to continuously express the viral E6/E7 oncogenes, that their intracellular p53 levels are reconstituted on E6/E7 repression, and that E6/E7 inhibition phenotypically results in cellular senescence. Here we show that hypoxic conditions, as are often found in subregions of cervical and head and neck cancers, enable HPV-positive cancer cells to escape from these regulatory principles: E6/E7 is efficiently repressed, yet, p53 levels do not increase. Moreover, E6/E7 repression under hypoxia does not result in cellular senescence, owing to hypoxia-associated impaired mechanistic target of rapamycin (mTOR) signaling via the inhibitory REDD1/TSC2 axis. Instead, a reversible growth arrest is induced that can be overcome by reoxygenation. Impairment of mTOR signaling also interfered with the senescence response of hypoxic HPV-positive cancer cells toward prosenescent chemotherapy in vitro. Collectively, these findings indicate that hypoxic HPV-positive cancer cells can induce a reversible state of dormancy, with decreased viral antigen synthesis and increased therapeutic resistance, and may serve as reservoirs for tumor recurrence on reoxygenation.

Validation of a 15-gene hypoxia classifier in head and neck cancer for prospective use in clinical trials

BACKGROUND

In head and neck squamous cell carcinomas (HNSCC) hypoxic radioresistance can be reduced by use of the hypoxic modifier nimorazole, as shown in the DAHANCA 5 trial. Recently, a 15-gene hypoxia classifier has shown predictive impact for the effect of nimorazole by identifying 'more' and 'less' hypoxic tumors in the DAHANCA 5 cohort. A prospective multicentre EORTC-1219 study is initiated, where nimorazole and prospective use of the classifier as a predictor is tested in relation to the most recent accelerated chemoradiotherapy treatment. Validation of the gene expression classification procedures is described here.

MATERIAL AND METHODS

Formalin-fixed paraffin-embedded (FFPE) tumor material from three recent HNSCC cohorts [DAHANCA 18 (n = 96), 24 (n = 40), and IAEA Hypo (n = 55)] was used to establish and validate procedures for prospective classification of patients. Repeatability was tested for the different steps in the gene expression analysis, and reproducibility was tested with xenograft tumors (FaDu_DD, UTSCC33), where gene expression in complementary sections was compared after fixation and embedding locally and at international institutions, respectively. Intra-tumor heterogeneity was addressed by classifying biopsy samples from HNSCC tumors, where 2-4 biopsies from each tumor was accessible.

RESULTS

Procedures were successfully established for individual classification of HNSCC patients in retrospective and prospective cohorts. Measurements of gene expression levels were reproducible between different international institutions.

CONCLUSION

Technical validation of the 15-gene hypoxia classifier demonstrated that it is suitable for implementation in prospective clinical trials.

Strategy of Using Intratreatment Hypoxia Imaging to Selectively and Safely Guide Radiation Dose De-escalation Concurrent With Chemotherapy for Locoregionally Advanced Human Papillomavirus-Related Oropharyngeal Carcinoma

PURPOSE

To report a small substudy of an ongoing large, multi-arm study using functional imaging to assess pre-/intratreatment hypoxia for all head and neck cancer, in which we hypothesized that pre- and early-treatment hypoxia assessment using functional positron emission tomography (PET) imaging may help select which human papillomavirus (HPV)-positive (HPV(+)) oropharyngeal cancer (OPC) patients can safely receive radiation de-escalation without jeopardizing treatment outcomes.

METHODS AND MATERIALS

Patients with HPV(+) oropharyngeal carcinoma were enrolled on an institutional review board-approved prospective study of which de-escalation based on imaging response was done for node(s) only. Pretreatment (18)F-fluorodeoxyglucose and dynamic (18)F-FMISO (fluoromisonidazole) positron emission tomography (PET) scans were performed. For patients with pretreatment hypoxia on(18)F-FMISO PET (defined as a >1.2 tumor to muscle standard uptake value ratio), a repeat scan was done 1 week after chemoradiation. Patients without pretreatment hypoxia or with resolution of hypoxia on repeat scan received a 10-Gy dose reduction to metastatic lymph node(s). The 2-year local, regional, distant metastasis-free, and overall survival rates were estimated using the Kaplan-Meier product-limit method. A subset of patients had biopsy of a hypoxic node done under image guidance.

RESULTS

Thirty-three HPV(+) OPC patients were enrolled in this pilot study. One hundred percent showed pretreatment hypoxia (at primary site and/or node[s]), and among these, 48% resolved (at primary site and/or node[s]); 30% met criteria and received 10-Gy reduction to the lymph node(s). At the median follow-up of 32 months (range, 21-61 months), the 2-year locoregional control rate was 100%. One patient failed distantly with persistence of hypoxia on (18)F-FMISO PET. The 2-year distant metastasis-free rate was 97%. The 2-year OS rate was 100%. Hypoxia on imaging was confirmed pathologically.

CONCLUSIONS

Hypoxia is present in HPV(+) tumors but resolves within 1 week of treatment in 48% of cases either at the primary site and/or lymph node(s). Our 100% locoregional control rate suggests that intratreatment functional imaging used to selectively de-escalate node(s) to 60 Gy was confirmed safe using our stringent imaging criteria. Intratreatment functional imaging warrants further study to determine its ultimate role in de-escalation treatment strategies.

HPV Associated Head and Neck Cancer

Head and neck cancers (HNCs) are a highly heterogeneous group of tumours that are associated with diverse clinical outcomes. Recent evidence has demonstrated that human papillomavirus (HPV) is involved in up to 25% of HNCs; particularly in the oropharyngeal carcinoma (OPC) subtype where it can account for up to 60% of such cases. HPVs are double-stranded DNA viruses that infect epithelial cells; numerous HPV subtypes, including 16, 18, 31, 33, and 35, drive epithelial cell transformation and tumourigenesis. HPV positive (HPV+) HNC represents a distinct molecular and clinical entity from HPV negative (HPV-) disease; the biological basis for which remains to be fully elucidated. HPV positivity is strongly correlated with a significantly superior outcome; indicating that such tumours should have a distinct management approach. This review focuses on the recent scientific and clinical investigation of HPV+ HNC. In particular, we discuss the importance of molecular and clinical evidence for defining the role of HPV in HNC, and the clinical impact of HPV status as a biomarker for HNC.

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.

Diffuse optical measurements of head and neck tumor hemodynamics for early prediction of chemoradiation therapy outcomes

This study used a hybrid near-infrared diffuse optical instrument to monitor tumor hemodynamic responses to chemoradiation therapy for early prediction of treatment outcomes in patients with head and neck cancer. Forty-seven patients were measured once per week to evaluate the hemodynamic status of clinically involved cervical lymph nodes as surrogates for the primary tumor response. Patients were classified into two groups: complete response (CR) (n=29) and incomplete response (IR) (n=18). Tumor hemodynamic responses were found to be associated with clinical outcomes (CR/IR), wherein the associations differed depending on human papillomavirus (HPV-16) status. In HPV-16 positive patients, significantly lower levels in tumor oxygenated hemoglobin concentration ([HbO2]) at weeks 1 to 3, total hemoglobin concentration at week 3, and blood oxygen saturation (StO2) at week 3 were found in the IR group. In HPV-16 negative patients, significantly higher levels in tumor blood flow index and reduced scattering coefficient (μs′) at week 3 were observed in the IR group. These hemodynamic parameters exhibited significantly high accuracy for early prediction of clinical outcomes, within the first three weeks of therapy, with the areas under the receiver operating characteristic curves (AUCs) ranging from 0.83 to 0.96.

Adverse effect of smoking on prognosis in human papillomavirus-associated oropharyngeal carcinoma

BACKGROUND

The purpose of this retrospective study was to identify prognostic factors in a cohort of patients with oropharyngeal carcinoma treated with intensity-modulated radiotherapy (IMRT).

METHODS

Medical records of 142 patients treated with (chemo)radiotherapy between September 2005 and September 2011 were reviewed and the human papillomavirus (HPV) status was determined by polymerase chain reaction (PCR) analysis. Potential prognostic factors for 3-year locoregional control and overall survival (OS) were evaluated.

RESULTS

HPV-positive patients (n = 82) had locoregional control and OS of 78% and 79%, respectively. Significant prognostic factors on multivariate analysis were smoking (p = .03) for locoregional control and OS, and comorbidity (p = .04) for OS. Further stratification was done according to smoking behavior in HPV-positive patients. Locoregional control in current smokers was 67% compared to 86% in never smokers and former smokers, respectively (p = .02).

CONCLUSION

Smoking was the only modifiable prognostic factor in HPV-positive patients. Therefore, active stop-smoking programs must be integrated in the routine management of patients to maximize treatment results. © 2016 Wiley Periodicals, Inc. Head Neck 38: 1780-1787, 2016.

Radiation-Induced Dedifferentiation of Head and Neck Cancer Cells Into Cancer Stem Cells Depends on Human Papillomavirus Status

PURPOSE

To test the hypothesis that the radiation response of cancer stem cells (CSCs) in human papillomavirus (HPV)-positive and HPV-negative head and neck squamous cell carcinoma (HNSCC) differs and is not reflected in the radiation response of the bulk tumor populations, that radiation therapy (RT) can dedifferentiate non-stem HNSCC cells into CSCs, and that radiation-induced dedifferentiation depends on the HPV status.

METHODS AND MATERIALS

Records of a cohort of 162 HNSCC patients were reviewed, and their outcomes were correlated with their HPV status. Using a panel of HPV-positive and HPV-negative HNSCC cell lines expressing a reporter for CSCs, we characterized HPV-positive and HPV-negative lines via flow cytometry, sphere-forming capacity assays in vitro, and limiting dilution assays in vivo. Non-CSCs were treated with different doses of radiation, and the dedifferentiation of non-CSCs into CSCs was investigated via flow cytometry and quantitative reverse transcription-polymerase chain reaction for re-expression of reprogramming factors.

RESULTS

Patients with HPV-positive tumors have superior overall survival and local-regional control. Human papillomavirus-positive HNSCC cell lines have lower numbers of CSCs, which inversely correlates with radiosensitivity. Human papillomavirus-negative HNSCC cell lines lack hierarchy owing to enhanced spontaneous dedifferentiation. Non-CSCs from HPV-negative lines show enhanced radiation-induced dedifferentiation compared with HPV-positive lines, and RT induced re-expression of Yamanaka reprogramming factors.

CONCLUSIONS

Supporting the favorable prognosis of HPV-positive HNSCCs, we show that (1) HPV-positive HNSCCs have a lower frequency of CSCs; (2) RT can dedifferentiate HNSCC cells into CSCs; and (3) radiation-induced dedifferentiation depends on the HPV status of the tumor.

Human Papilloma Virus as a Biomarker for Personalized Head and Neck Cancer Radiotherapy

A dramatic increase in the incidence of HPV-related oropharyngeal cancer has been reported in some parts of the western world over the past 30 years. They constitute a clinically distinct subgroup of cancers in terms of molecular biology, patient characteristics, and treatment outcome. This chapter describes the molecular characteristics, epidemiology, and demographics of the HPV-related head and neck cancers and discuss available methods to detect HPV-related tumours. The impact of HPV-related biomarkers in clinical studies on radiotherapy only, altered fractionation, modulation of hypoxia, and concurrent chemo- or bio-radiotherapy are reviewed as well as the perspectives of de-escalation and immune-modulation are discussed.

[Radiosensitivity and/or radioresistance of head and neck cancers: Biological angle]

Radiation therapy is a cornerstone of head and neck cancer management. Technological improvements in recent years in radiation therapy, with intensity-modulated techniques, reinforce even more its role. However, both local and locoregional relapses are still observed. Understanding biological mechanisms of treatment resistance is a topic of major interest. From the cancer cell itself, its ability to repair and proliferate, its microenvironment and oxygenation conditions, migratory and invasive capacity, to biological parameters related to the patient, there are many mechanisms involving radiosensitivity and/or radioresistance of head and neck cancer. The present study explores the main biological mechanisms involved in radiation resistance of head and neck cancer, and describes promising therapeutic approaches.

De-escalation of radiation dose for human papillomavirus-positive oropharyngeal head and neck squamous cell carcinoma: A case report and preclinical and clinical literature review

Traditionally, head and neck squamous cell carcinoma (HNSCC) has been considered to be a relatively homogeneous disease. However, recent data have demonstrated that human papillomavirus (HPV)-positive and HPV-negative disease are two different clinical entities associated with different outcomes. Preclinical and clinical studies have reported a divergence in treatment strategies as well as prognostic outcomes for HNSCCs that are HPV-positive versus HPV-negative. The present study describes the case of a 52-year-old man who presented with stage IVB cT2N3M0 right tonsillar HPV-positive squamous cell carcinoma. Induction chemotherapy with docetaxel, cisplatin and 5-fluorouracil (TPF), followed by chemoradiation therapy with carboplatin and 70 Gray (Gy) radiation in daily fractions was recommended. The patient completed the TPF and carboplatin treatment; however, he was unable to tolerate the radiation course, receiving a final dose of 46 Gy. A 60-day follow-up right neck salvage dissection was subsequently performed. Despite having received a partial radiation treatment of 46 Gy, the patient had no pathological evidence of disease at 60 days post radiation treatment. Repeat positron emission tomography-computed tomography at 32 months after the right neck dissection revealed no evidence of disease. The present study also discusses the current preclinical in vitro and in vivo targets for HPV-positive HNSCC and the obstacles presented in advancing clinical treatment modalities. Previous preclinical models investigating radiation sensitivity have yielded mixed results. Thus, it is important to understand and establish representative preclinical models for studying HPV and HNSCC to improve clinical research and therapeutic development. This review may guide future understanding of the role of HPV in HNSCC.

Human Papillomavirus-Negative Pharyngeal Cancer

Human papillomavirus-negative head and neck squamous cell carcinoma (HNSCC) carries a poor prognosis, and despite optimal treatment with chemoradiotherapy to the limit of tolerance, many patients will relapse. A number of methods for intensifying treatment of HNSCC have been investigated, leading to the current standards of care. Novel agents targeting tumor cell and stromal signaling, DNA damage response, and immune system are now reaching clinical trials in combination with chemoradiotherapy. In this review, we discuss the evidence for the current treatment of locally advanced human papillomavirus-negative HNSCC, as well as investigational therapies, such as hypoxia modification, molecular targeting of epidermal growth factor receptor family, vascular endothelial growth factor receptor or DNA damage response proteins in combination with radiation therapy.

The rationale for HPV-related oropharyngeal cancer de-escalation treatment strategies

The treatment paradigms for head and neck squamous cell cancer (HNSCC) are changing due to the emergence of human papillomavirus-associated tumors (HPV-related), possessing distinct molecular profiles and responses to therapy. Retrospective studies have suggested that HPV-related HNSCCs are more frequently cured than those caused by tobacco. Current clinical trials focus on the reduction of treatment-related toxicity and the development of HPV-targeted therapies. New treatment strategies include: 1) dose reduction of radiotherapy, 2) the use of cetuximab instead of cisplatin for chemo-radiation 3) less invasive surgical options, i.e. trans-oral robotic surgery and trans-oral laser microlaryngoscopy, and 4) more specific treatment attempts, including immunotherapeutic strategies, thanks to increasing comprehension of the molecular background of HPV-related HNSCC. Whereas recently published data shed light on immune mechanisms, other studies have focused on specific vaccination against HPV-related HNSCC. A crucial problem is patient selection to the chosen bias. Truly HPV-related cancers (p16-positive and HPV DNA-positive) with biomarkers for good response to therapy could be included in randomized trials aiming for less severe and better tailored therapy.

Modulation of therapeutic sensitivity by human papillomavirus

Human papillomaviruses (HPVs) are small double-stranded DNA viruses that pose significant public health concerns as the causative agent of approximately 5% of worldwide cancers. The HPV oncogenes E6 and E7 play key roles in carcinogenesis. In the last 15years there has been a significant increase in the incidence of HPV-related head and neck cancers arising primarily in the oropharynx. Patients with HPV-positive head and neck cancers (HNCs) have a significantly improved prognosis compared to those with HPV-negative disease. In this review we will discuss data suggesting how HPV oncogenes modulate both the intrinsic radiation sensitivity of HNCs and also have important effects upon the tumor microenvironment. Together, these findings contribute to the improved outcomes seen in patients with HPV-positive HNC.

Heterogeneity of (18)F-FDG PET combined with expression of EGFR may improve the prognostic stratification of advanced oropharyngeal carcinoma

The Ang's risk profile (based on p16, smoking and cancer stage) is a well-known prognostic factor in oropharyngeal squamous cell carcinoma (OPSCC). Whether heterogeneity in (18)F-fluorodeoxyglucose (FDG) positron emission tomographic (PET) images and epidermal growth factor receptor (EGFR) expression could provide additional information on clinical outcomes in advanced-stage OPSCC was investigated. Patients with stage III-IV OPSCC who completed primary therapy were eligible. Zone-size nonuniformity (ZSNU) extracted from pretreatment FDG PET scans was used as an index of image heterogeneity. EGFR and p16 expression were examined by immunohistochemistry. Disease-specific survival (DSS) and overall survival (OS) served as outcome measures. Kaplan-Meier estimates and Cox proportional hazards regression models were used for survival analysis. A bootstrap resampling technique was applied to investigate the stability of outcomes. Finally, a recursive partitioning analysis (RPA)-based model was constructed. A total of 113 patients were included, of which 28 were p16-positive. Multivariate analysis identified the Ang's profile, EGFR and ZSNU as independent predictors of both DSS and OS. Using RPA, the three risk factors were used to devise a prognostic scoring system that successfully predicted DSS in both p16-positive and -negative cases. The c-statistic of the prognostic index for DSS was 0.81, a value which was significantly superior to both AJCC stage (0.60) and the Ang's risk profile (0.68). In patients showing an Ang's high-risk profile (N = 77), the use of our scoring system clearly identified three distinct prognostic subgroups. It was concluded that a novel index may improve the prognostic stratification of patients with advanced-stage OPSCC.

Effective Biomarkers and Radiation Treatment in Head and Neck Cancer

CONTEXT

Radiation is a key arm in the multidisciplinary treatment of patients with head and neck squamous cell carcinoma. During the past 2 decades, significant changes in the way radiation therapy is planned and delivered have improved efficacy and decreased toxicity. Refined approaches in the application of radiation and chemoradiation have led to organ-sparing treatment regimens for laryngeal and pharyngeal cancers and have improved local and regional control rates in the postoperative, adjuvant setting. The molecular and genetic determinants of tumor cell response to radiation have been studied, and several potential biomarkers are emerging that could further improve application and efficacy of radiation treatment in head and neck squamous cell carcinoma.

OBJECTIVE

To discuss the current understanding of potential biomarkers related to radiation response in head and neck squamous cell carcinoma.

DATA SOURCES

Existing published literature.

CONCLUSIONS

Several potential biomarkers are actively being studied as predictors and targets to improve the use and efficacy of radiation therapy to treat head and neck squamous cell carcinoma. Several promising candidates have been defined, and new markers are on the horizon.

A rapid and sensitive determination of hypoxic radiosensitizer agent nimorazole in rat plasma by LC-MS/MS and its application to a pharmacokinetic study

A highly sensitive, accurate and robust LC-MS/MS method was developed and validated for determination of nimorazole (NMZ) in rat plasma using metronidazole (MNZ) as internal standard (IS). The analyte and IS were extracted from plasma by precipitating protein with acetonitrile and were chromatographed using an Agilent Poroshell 120, EC-C18 column. The mobile phase was composed of a mixture of acetonitrile and 0.1 % formic acid (85:15 v/v). The total run time was 1.5 min and injection volume was 5 μL. Multiple reaction monitoring mode using the transitions of m/z 227.1 → m/z 114.0 for MNZ and m/z 172.10 → m/z 128.1 for IS were monitored on a triple quadrupole mass spectrometer, operating in positive ion mode. The calibration curve was linear in the range of 0.25-200 ng/mL (r(2)  > 0.9996) and the lower limit of quantification was 0.25 ng/mL in the rat plasma samples. Recoveries of NMZ ranged between 88.05 and 95.25%. The precision (intra-day and inter-day) and accuracy of the quality control samples were 1.25-8.20% and -2.50-3.10, respectively. The analyte and IS were found to be stable during all sample storage and analysis procedures. The LC-MS/MS method described here was validated and successfully applied to pharmacokinetic study in rats.

Establishment of a novel human papillomavirus-negative and radiosensitive head and neck squamous cell carcinoma cell line

BACKGROUND

The purpose of this study was to develop a CMCSCC-1 cell line for head and neck cancer research into new therapies for head and neck squamous cell carcinoma (HNSCC).

METHODS

The CMCSCC-1 cell line was isolated from a primary oral tongue tumor specimen of a female patient. Tumor cells were evaluated for biomarkers expression by Western blots, reverse transcriptase-polymerase chain reaction (RT-PCR), fluorescence activated cell sorter, and immunostaining. Cell proliferation in response to radiation was measured by the WST-8 assay.

RESULTS

The characterization analyses revealed a typical epithelial morphology; a doubling time of approximately 24 hours, high tumorigenicity in immunodeficient mice, and upregulated biomarkers. CMCSCC-1 cells were negative for human papillomavirus (HPV) infection, but more sensitive to radiation compared with those FaDu cell lines.

CONCLUSION

CMCSCC-1, a novel oral tongue SCC cell line, was established. It will help in the elucidation of the molecular pathogenesis of HPV-negative radiosensitive tumors. © 2015 Wiley Periodicals, Inc. Head Neck 38: E542-E551, 2015.

Human papillomavirus type 16 E7 oncoprotein causes a delay in repair of DNA damage

BACKGROUND AND PURPOSE

Patients with human papillomavirus related (HPV+) head and neck cancers (HNCs) demonstrate improved clinical outcomes compared to traditional HPV negative (HPV-) HNC patients. We have recently shown that HPV+ HNC cells are more sensitive to radiation than HPV- HNC cells. However, roles of HPV oncogenes in regulating the response of DNA damage repair remain unknown.

MATERIAL AND METHODS

Using immortalized normal oral epithelial cell lines, HPV+ HNC derived cell lines, and HPV16 E7-transgenic mice we assessed the repair of DNA damage using γ-H2AX foci, single and split dose clonogenic survival assays, and immunoblot. The ability of E7 to modulate expression of proteins associated with DNA repair pathways was assessed by immunoblot.

RESULTS

HPV16 E7 increased retention of γ-H2AX nuclear foci and significantly decreased sublethal DNA damage repair. While phospho-ATM, phospho-ATR, Ku70, and Ku80 expressions were not altered by E7, Rad51 was induced by E7. Correspondingly, HPV+ HNC cell lines showed retention of Rad51 after γ-radiation.

CONCLUSIONS

Our findings provide further understanding as to how HPV16 E7 manipulates cellular DNA damage responses that may underlie its oncogenic potential and influence the altered sensitivity to radiation seen in HPV+ HNC as compared to HPV- HNC.

The inhibition of PARP but not EGFR results in the radiosensitization of HPV/p16-positive HNSCC cell lines

BACKGROUND AND PURPOSE

HPV-negative and HPV-positive HNSCC comprise distinct tumor entities with different biological characteristics. Specific regimens for the comparably well curable HPV-positive entity that reduce side effects without compromising outcome have yet to be established. Therefore, we tested here whether the inhibition of EGFR or PARP may be used to specifically enhance the radiosensitivity of HPV-positive HNSCC cells.

MATERIALS AND METHODS

Experiments were performed with five HPV/p16-positive HNSCC cell lines. Inhibitors used were cetuximab, olaparib and PF-00477736. The respective inhibition of EGFR, PARP and Chk1 was evaluated by Western blot, immunofluorescence analysis and assessment of cell cycle distribution. Cell survival was assessed by colony formation assay.

RESULTS

Inhibition of EGFR by cetuximab failed to radiosensitize any of the HPV-positive HNSCC cell lines tested. In contrast, PARP-inhibition resulted in a substantial radiosensitization of all strains, with the sensitization being further enhanced by the additional inhibition of Chk1.

CONCLUSIONS

PARP-inhibition effectively radiosensitizes HPV-positive HNSCC cells and may therefore represent a viable alternative to chemotherapy possibly even allowing for a reduction in radiation dose. For the latter, PARP-inhibition may be combined with the inhibition of Chk1. In contrast, the inhibition of EGFR cannot be expected to radiosensitize HPV-positive HNSCC through the modulation of cellular radiosensitivity.

Targeting tumour hypoxia to prevent cancer metastasis. From biology, biosensing and technology to drug development: the METOXIA consortium

The hypoxic areas of solid cancers represent a negative prognostic factor irrespective of which treatment modality is chosen for the patient. Still, after almost 80 years of focus on the problems created by hypoxia in solid tumours, we still largely lack methods to deal efficiently with these treatment-resistant cells. The consequences of this lack may be serious for many patients: Not only is there a negative correlation between the hypoxic fraction in tumours and the outcome of radiotherapy as well as many types of chemotherapy, a correlation has been shown between the hypoxic fraction in tumours and cancer metastasis. Thus, on a fundamental basis the great variety of problems related to hypoxia in cancer treatment has to do with the broad range of functions oxygen (and lack of oxygen) have in cells and tissues. Therefore, activation-deactivation of oxygen-regulated cascades related to metabolism or external signalling are important areas for the identification of mechanisms as potential targets for hypoxia-specific treatment. Also the chemistry related to reactive oxygen radicals (ROS) and the biological handling of ROS are part of the problem complex. The problem is further complicated by the great variety in oxygen concentrations found in tissues. For tumour hypoxia to be used as a marker for individualisation of treatment there is a need for non-invasive methods to measure oxygen routinely in patient tumours. A large-scale collaborative EU-financed project 2009-2014 denoted METOXIA has studied all the mentioned aspects of hypoxia with the aim of selecting potential targets for new hypoxia-specific therapy and develop the first stage of tests for this therapy. A new non-invasive PET-imaging method based on the 2-nitroimidazole [(18)F]-HX4 was found to be promising in a clinical trial on NSCLC patients. New preclinical models for testing of the metastatic potential of cells were developed, both in vitro (2D as well as 3D models) and in mice (orthotopic grafting). Low density quantitative real-time polymerase chain reaction (qPCR)-based assays were developed measuring multiple hypoxia-responsive markers in parallel to identify tumour hypoxia-related patterns of gene expression. As possible targets for new therapy two main regulatory cascades were prioritised: The hypoxia-inducible-factor (HIF)-regulated cascades operating at moderate to weak hypoxia (<1% O(2)), and the unfolded protein response (UPR) activated by endoplasmatic reticulum (ER) stress and operating at more severe hypoxia (<0.2%). The prioritised targets were the HIF-regulated proteins carbonic anhydrase IX (CAIX), the lactate transporter MCT4 and the PERK/eIF2α/ATF4-arm of the UPR. The METOXIA project has developed patented compounds targeting CAIX with a preclinical documented effect. Since hypoxia-specific treatments alone are not curative they will have to be combined with traditional anti-cancer therapy to eradicate the aerobic cancer cell population as well.

Estimate of the impact of FDG-avidity on the dose required for head and neck radiotherapy local control

Background and purpose

Although FDG-avid tumors are recognized as a potential target for dose escalation, there is no clear basis for selecting a boost dose to counter this apparent radioresistance. Using a novel analysis method, based on the new concept of an outcome-equivalent dose, we estimate the extra dose required to equalize local control between FDG-avid and non-avid head and neck tumors.

Materials and methods

Based on a literature review, five reports of head and neck cancer (423 patients in total), along with an internal validation dataset from our institution (135 oropharynx patients), were used in this analysis. To compensate for the heterogeneity among multi-institutional patient cohorts and corresponding treatment techniques, local control data of the cohorts were fit to a single dose–response curve with a clinically representative steepness (γ₅₀ = 2), thereby defining an ‘outcome-equivalent dose’ (OED) for each institutional cohort. Separate dose–response curves were then determined for the FDG-avid and FDG-non-avid patient cohorts, and the ratio of TD₅₀ (tumor dose required for 50% of control) values between the high- and low-FDG-uptake groups (TD_50,high/TD_50,low) was estimated, resulting in an estimated metabolic dose-modifying factor (mDMF) due to FDG-avidity.

Results

For individual datasets, the estimated mDMFs were found to be in the range of 1.07–1.62, decreasing if the assumed slope (γ₅₀) increased. Weighted logistic regression for the six datasets resulted in a mDMF of 1.19 [95% CI: 1.04–1.34] for a γ₅₀ value of 2, which translates to a needed dose increase of about 1.5 Gy per unit increase in the maximum standardized uptake value (SUV_m) of FDG-PET [95% CI: 0.3–2.7]. Assumptions of lower or higher γ₅₀ values (1.5 or 2.5) resulted in slightly different mDMFs: 1.26 or 1.15, respectively. A validation analysis with seven additional datasets, based on relaxed criteria, was consistent with the estimated mDMF.

Conclusions

We introduced a novel outcome-equivalent dose analysis method to estimate the dose– response modifying effect of FDG uptake variation. To reach equal response rates, FDG-avid tumors are likely to require 10% to 30% more dose than FDG-non-avid tumors. These estimates provide a rational starting point for selecting IMRT boosts for FDG-avid tumors. However, independent tests and refinements of the estimated dose-modifying effect, using high-quality prospective clinical trial data, are needed.

Biological basis for increased sensitivity to radiation therapy in HPV-positive head and neck cancers

Although development of head and neck squamous cell carcinomas (HNSCCs) is commonly linked to the consumption of tobacco and alcohol, a link between human papillomavirus (HPV) infection and a subgroup of head and neck cancers has been established. These HPV-positive tumors represent a distinct biological entity with overexpression of viral oncoproteins E6 and E7. It has been shown in several clinical studies that HPV-positive HNSCCs have a more favorable outcome and greater response to radiotherapy. The reason for improved prognosis of HPV-related HNSCC remains speculative, but it could be owned to multiple factors. One hypothesis is that HPV-positive cells are intrinsically more sensitive to standard therapies and thus respond better to treatment. Another possibility is that HPV-positive tumors uniquely express viral proteins that induce an immune response during therapy that helps clear tumors and prevents recurrence. Here, we will review current evidence for the biological basis of increased radiosensitivity in HPV-positive HNSCC.

Expression of EGFR and HPV-associated p16 in oropharyngeal carcinoma: correlation and influence on prognosis after radiotherapy in the randomized DAHANCA 5 and 7 trials

AIM

EGFR and HPV-associated p16 are among the most investigated biomarkers in head and neck cancer. The aim was to investigate the correlation and interaction between these two markers and to evaluate their potential prognostic significance when combined.

MATERIALS AND METHODS

336 Oropharyngeal carcinomas treated with primary radiotherapy (66-68 Gy, 2fx/day, 10-12 Gy/week) and with known EGFR/p16-status estimated semiquantitatively by immunohistochemistry were included in the study. Data were evaluated by EGFR-expression (high/low) and p16-status (positive/negative) consequently dividing tumours into four groups by combination of the biomarkers. Patient/tumour characteristics and complete 5-year follow-up were available.

RESULTS

Low EGFR-expression was significantly more common in p16-positive tumours compared to p16-negative, p < 0.0001. p16 positivity showed a strong prognostic impact (p < 0.0001, HR = 0.22 [0.13-0.38]), whereas EGFR was a weak prognostic marker when local control was used as endpoint (p = 0.03, HR = 0.53 [0.29-0.94]). Combination of EGFR/p16 did not add significant information to p16 alone and by multivariable analysis only p16 showed significant prognostic information for all evaluated endpoints.

CONCLUSIONS

Both EGFR and p16 bear prognostic information in oropharyngeal cancer, although p16 is, by far, the strongest prognostic factor. The markers seem to be correlated and this might have influence when evaluating the effect of EGFR inhibition in oropharyngeal tumours.