Modulation of repopulation processes in oral mucosa: experimental results

Gene alterations as predictors of radiation-induced toxicity in head and neck squamous cell carcinoma

Background

Optimizing the therapeutic ratio for radiation therapy (RT) in head and neck squamous cell carcinoma (HNSCC) is uniquely challenging owing to high rates of early and late toxicity involving nearby organs at risk. These toxicities have a profound impact on treatment compliance and quality of life. Emerging evidence suggests that RT dose alone cannot fully account for the variable severity of RT-related adverse events (rtAEs) observed in HNSCC patients. Next-generation sequencing has become an increasingly valuable tool with widespread use in the oncology field and is being robustly explored for predicting rtAEs beyond dosimetric data.

Methods

Patients who had Foundation Medicine sequencing data and received RT for primary or locally recurrent HNSCC were selected for this study. Early and late toxicity data were collected and reported based on Common Terminology Criteria for Adverse Events version 5.0. Dosimetric parameters were collected for pertinent structures.

Results

A total of HNSCC 37 patients were analyzed in this study. Genetic alterations in BRCA2, ERBB3, NOTCH1 and CCND1 were all associated with higher mean grade of toxicity with BRCA2 alteration implicated in all toxicity parameters evaluated including mucositis, early dysphagia, xerostomia and to a lesser extent, late dysphagia. Interestingly, patients who exhibited alterations in both BRCA2 and ERBB3 experienced a twofold or greater increase in early dysphagia, early xerostomia and late dysphagia compared to ERBB3 alteration alone. Furthermore, several gene alterations were associated with improved toxicity outcomes. Within an RT supersensitive patient subset, alterations were found in TNFAIP3, HNF1A, SPTA1 and CASP8. All of these alterations were not found in the RT insensitive patient subset. We found 17 gene alterations in the RT insensitive patient subset that were not found in the RT supersensitive patient subset.

Conclusion

Despite consistent RT dosimetric parameters, patients with HNSCC experience heterogeneous patterns of rtAEs. Identifying factors associated with toxicity outcomes offers a new avenue for personalized precision RT therapy and prophylactic management. Here, next-generation sequencing in a population of HNSCC patients correlates several genetic alterations with severity of rtAEs. Further analysis is urgently needed to identify genetic patterns associated with rtAEs in order to reduce harmful outcomes in this challenging population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02876-5.

The Acute and Early Effects of Whole-Brain Irradiation on Glial Activation, Brain Metabolism, and Behavior: a Positron Emission Tomography Study

Purpose

Radiotherapy is a frequently applied treatment modality for brain tumors. Concomitant irradiation of normal brain tissue can induce various physiological responses. The aim of this study was to investigate whether acute and early-delayed effects of brain irradiation on glial activation and brain metabolism can be detected with positron emission tomography (PET) and whether these effects are correlated with behavioral changes.

Procedures

Rats underwent 0-, 10-, or 25-Gy whole-brain irradiation. At 3 and 31 days post irradiation, 1-(2-chlorophenyl)-N-[¹¹C]methyl-(1-methylpropyl)-3-isoquinoline carboxamide ([¹¹C]PK11195) and 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG) PET scans were acquired to detect changes in glial activation (neuroinflammation) and glucose metabolism, respectively. The open-field test (OFT) was performed on days 6 and 27 to assess behavioral changes.

Results

Twenty-five-gray-irradiated rats showed higher [¹¹C]PK11195 uptake in most brain regions than controls on day 3 (striatum, hypothalamus, accumbens, septum p < 0.05), although some brain regions had lower uptake (cerebellum, parietal association/retrosplenial visual cortex, frontal association/motor cortex, somatosensory cortex, p < 0.05). On day 31, several brain regions in 25-Gy-irradiated rats still showed significantly higher [¹¹C]PK11195 uptake than controls and 10-Gy-irradiated group (p < 0.05). Within-group analysis showed that [¹¹C]PK11195 uptake in individual brain regions of 25-Gy treated rats remained stable or slightly increased between days 3 and 31. In contrast, a significant reduction (p < 0.05) in tracer uptake between days 3 and 31 was found in all brain areas of controls and 10-Gy-irradiated animals. Moreover, 10-Gy treatment led to a significantly higher [¹⁸F]FDG uptake on day 3 (p < 0.05). [¹⁸F]FDG uptake decreased between days 3 and 31 in all groups; no significant differences between groups were observed anymore on day 31, except for increased uptake in the hypothalamus in the 10-Gy group. The OFT did not show any significant differences between groups.

Conclusions

Non-invasive PET imaging indicated that brain irradiation induces neuroinflammation and a metabolic flare, without causing acute or early-delayed behavioral changes.

Electronic supplementary material

The online version of this article (10.1007/s11307-020-01483-y) contains supplementary material, which is available to authorized users.

Cellular mechanisms of cyclophosphamide-induced taste loss in mice

Many commonly prescribed chemotherapy drugs such as cyclophosphamide (CYP) have adverse side effects including disruptions in taste which can result in loss of appetite, malnutrition, poorer recovery and reduced quality of life. Previous studies in mice found evidence that CYP has a two-phase disturbance in taste behavior: a disturbance immediately following drug administration and a second which emerges several days later. In this study, we examined the processes by which CYP disturbs the taste system by examining the effects of the drug on taste buds and cells responsible for taste cell renewal using immunohistochemical assays. Data reported here suggest CYP has direct cytotoxic effects on lingual epithelium immediately following administration, causing an early loss of taste sensory cells. Types II and III cells in fungiform taste buds appear to be more susceptible to this effect than circumvallate cells. In addition, CYP disrupts the population of rapidly dividing cells in the basal layer of taste epithelium responsible for taste cell renewal, manifesting a disturbance days later. The loss of these cells temporarily retards the system’s capacity to replace Type II and Type III taste sensory cells that survived the cytotoxic effects of CYP and died at the end of their natural lifespan. The timing of an immediate, direct loss of taste cells and a delayed, indirect loss without replacement of taste sensory cells are broadly congruent with previously published behavioral data reporting two periods of elevated detection thresholds for umami and sucrose stimuli. These findings suggest that chemotherapeutic disturbances in the peripheral mechanisms of the taste system may cause dietary challenges at a time when the cancer patient has significant need for well balanced, high energy nutritional intake.

Oral Mucositis: Melatonin Gel an Effective New Treatment

The current treatment for cervico-facial cancer involves radio and/or chemotherapy. Unfortunately, cancer therapies can lead to local and systemic complications such as mucositis, which is the most common dose-dependent complication in the oral cavity and gastrointestinal tract. Mucositis can cause a considerably reduced quality of life in cancer patients already suffering from physical and psychological exhaustion. However, the role of melatonin in the treatment of mucositis has recently been investigated, and offers an effective alternative therapy in the prevention and/or management of radio and/or chemotherapy-induced mucositis. This review focuses on the pathobiology and management of mucositis in order to improve the quality of cancer patients' lives.

Radiogenomics: A systems biology approach to understanding genetic risk factors for radiotherapy toxicity?

Adverse reactions in normal tissue after radiotherapy (RT) limit the dose that can be given to tumour cells. Since 80% of individual variation in clinical response is estimated to be caused by patient-related factors, identifying these factors might allow prediction of patients with increased risk of developing severe reactions. While inactivation of cell renewal is considered a major cause of toxicity in early-reacting normal tissues, complex interactions involving multiple cell types, cytokines, and hypoxia seem important for late reactions. Here, we review 'omics' approaches such as screening of genetic polymorphisms or gene expression analysis, and assess the potential of epigenetic factors, posttranslational modification, signal transduction, and metabolism. Furthermore, functional assays have suggested possible associations with clinical risk of adverse reaction. Pathway analysis incorporating different 'omics' approaches may be more efficient in identifying critical pathways than pathway analysis based on single 'omics' data sets. Integrating these pathways with functional assays may be powerful in identifying multiple subgroups of RT patients characterised by different mechanisms. Thus 'omics' and functional approaches may synergise if they are integrated into radiogenomics 'systems biology' to facilitate the goal of individualised radiotherapy.

Modulation of radiation-induced oral mucositis by thalidomide : Preclinical studies

PURPOSE

Oral mucositis is a common, dose-limiting early side effect of radio(chemo)therapy for head-and-neck tumors. The epithelial radiation response is accompanied by changes in the inflammatory signaling cascades mediated by the transcription factor nuclear factor-kappa B (NF-κB). The present study was initiated to determine the effect of the NF-κB inhibitor thalidomide on the clinical manifestation of oral mucositis in the established mouse tongue model.

MATERIALS AND METHODS

Treatment protocols comprised single dose irradiation and daily fractionated irradiation (5  fractions of 3 Gy/week) over 1 (days 0-4) or 2 weeks (days 0-4, 7-11), alone or in combination with daily thalidomide application (100 mg/kg intraperitoneally) over varying time intervals. Fractionation protocols were terminated by graded local radiation doses (day 7/14) to generate full dose-effect curves. Tongue epithelial ulcerations, corresponding to confluent mucositis, served as the clinically relevant endpoint.

RESULTS

Thalidomide application did not show a significant radioprotective potential when administered in combination with single dose irradiation. Thalidomide in combination with one week of fractionated irradiation significantly increased the isoeffective top-up doses. Similar results were observed during two weeks of fractionated irradiation in all but one experiment.

CONCLUSION

Thalidomide treatment demonstrated a significant mucositis-ameliorating effect during fractionated irradiation, which is likely to result from NF-κB inhibition. However, further mechanistic studies are required to define the underlying mechanisms of the observed mucoprotective effect.

Pathophysiology of Radiation-Induced Dysphagia in Head and Neck Cancer

Oncologic treatments, such as curative radiotherapy and chemoradiation, for head and neck cancer can cause long-term swallowing impairments (dysphagia) that negatively impact quality of life. Radiation-induced dysphagia comprised a broad spectrum of structural, mechanical, and neurologic deficits. An understanding of the biomolecular effects of radiation on the time course of wound healing and underlying morphological tissue responses that precede radiation damage will improve options available for dysphagia treatment. The goal of this review is to discuss the pathophysiology of radiation-induced injury and elucidate areas that need further exploration.

Exposure to Carbon Ions Triggers Proinflammatory Signals and Changes in Homeostasis and Epidermal Tissue Organization to a Similar Extent as Photons

The increasing application of charged particles in radiotherapy requires a deeper understanding of early and late side effects occurring in skin, which is exposed in all radiation treatments. We measured cellular and molecular changes related to the early inflammatory response of human skin irradiated with carbon ions, in particular cell death induction and changes in differentiation and proliferation of epidermal cells during the first days after exposure. Model systems for human skin from healthy donors of different complexity, i.e., keratinocytes, coculture of skin cells, 3D skin equivalents, and skin explants, were used to investigate the alterations induced by carbon ions (spread-out Bragg peak, dose-averaged LET 100 keV/μm) in comparison to X-ray and UV-B exposure. After exposure to ionizing radiation, in none of the model systems, apoptosis/necrosis was observed. Carbon ions triggered inflammatory signaling and accelerated differentiation of keratinocytes to a similar extent as X-rays at the same doses. High doses of carbon ions were more effective than X-rays in reducing proliferation and inducing abnormal differentiation. In contrast, changes identified following low-dose exposure (≤0.5 Gy) were induced more effectively after X-ray exposure, i.e., enhanced proliferation and change in the polarity of basal cells.

The effect of low dose ionizing radiation on homeostasis and functional integrity in an organotypic human skin model

Outside the protection of Earth's atmosphere, astronauts are exposed to low doses of high linear energy transfer (LET) radiation. Future NASA plans for deep space missions or a permanent settlement on the moon are limited by the health risks associated with space radiation exposures. There is a paucity of direct epidemiological data for low dose exposures to space radiation-relevant high LET ions. Health risk models are used to estimate the risk for such exposures, though these models are based on high dose experiments. There is increasing evidence, however, that low and high dose exposures result in different signaling events at the molecular level, and may involve different response mechanisms. Further, despite their low abundance, high LET particles have been identified as the major contributor to health risk during manned space flight. The human skin is exposed in every external radiation scenario, making it an ideal epithelial tissue model in which to study radiation induced effects. Here, we exposed an in vitro three dimensional (3-D) human organotypic skin tissue model to low doses of high LET oxygen (O), silicon (Si) and iron (Fe) ions. We measured proliferation and differentiation profiles in the skin tissue and examined the integrity of the skin's barrier function. We discuss the role of secondary particles in changing the proportion of cells receiving a radiation dose, emphasizing the possible impact on radiation-induced health issues in astronauts.

Tumour repopulation and the role of abortive division in squamous cell carcinomas during chemotherapy

OBJECTIVES

In head and neck cancers, tumour cell repopulation during chemotherapy is one reason for treatment failure. Some of the mechanisms responsible for this repopulation are cell recruitment and abortive division. Due to lack of quantitative data in the literature regarding these mechanisms, the aim of this study was to investigate the interplay between recruitment and abortive division during cisplatin chemotherapy and to quantify the impact of these mechanisms on tumour control.

MATERIALS AND METHODS

An in silico Monte Carlo tumour model was developed to simulate tumour behaviour during chemotherapy. The virtual tumour had the composition and kinetic properties of a biological tumour. Effect of cisplatin on cell cycle and repopulation mechanisms were simulated and interpreted.

RESULTS

Abortive division contributed to cell production within the tumour during chemotherapy. There was a strong relationship between recruitment and tumour growth due to abortive division. This observation was supported by the value of proliferative/stem ratio, which increased from 1.3 to 36, even when using small recruitment parameters.

CONCLUSIONS

While abortive division contributed towards tumour repopulation during chemotherapy, this mechanism could be controlled by daily doses of cisplatin. On the other hand, stem cells require an additional cytotoxic agent to overcome repopulation due to cell recruitment. Consequently, repopulation via abortive division during chemotherapy did not entail alterations in treatment schedule, nor dose escalation, to control the tumour.

Application of organ tolerance dose-constraints in clinical studies in radiation oncology

In modern radiation oncology, tolerance dose-constraints for organs at risk (OAR) must be considered for treatment planning, but particularly in order to design clinical studies. Tolerance dose tables, however, only address one aspect of the therapeutic ratio of any clinical study, i.e., the limitation of adverse events, but not the desired potential improvement in the tumor effect of a novel treatment strategy. A sensible application of "tolerance doses" in a clinical situation requires consideration of various critical aspects addressed here: definition of tolerance dose, specification of an endpoint/symptom, consideration of radiation quality and irradiation protocol, exposed volume and dose distribution, and patient-related factors of radiosensitivity. The currently most comprehensive estimates of OAR radiation tolerance are in the QUANTEC compilations (2010). However, these tolerance dose values must only be regarded as a rough orientation and cannot answer the relevant question for the patients, i.e., if the study can achieve a therapeutic advantage; this can obviously be answered only by the final scientific analysis of the study results. Despite all limitations, the design of clinical studies should currently refer to the QUANTEC values for appreciation of the risk of complications, if needed supplemented by one's own data or further information from the literature. The implementation of a consensus on the safety interests of the patients and on an application and approval process committed to progress in medicine, with transparent quality-assuring requirements with regard to the structural safeguarding of the study activities, plays a central role in clinical research in radiation oncology.

The role of re-irradiation of secondary and recurrent head and neck carcinomas. Is it a potentially curative treatment? A practical approach

Despite aggressive efforts to cure head and neck cancer patients, including altered fractionation and the addition of chemotherapy to radiation, locoregional recurrence remains a serious issue to face in clinical practice. Indeed, recurrent and second primary tumors occurring in previously irradiated area are common clinical challenge. Whenever possible, patients are advised to undergo salvage surgery. Nevertheless, few patients are suitable candidates for curative resection. In such cases, chemotherapy alone has traditionally been considered, with a poor response rate. It has been questioned whether re-irradiation toxicity outweighs the potential benefits, considering that the median survival of re-irradiated patients marginally exceeds the benefits observed with chemotherapy alone. However, full-dose re-irradiation is a viable treatment option, offering long-term survival for selected patients. Moreover, several prognostic factors should be considered for patients undergoing re-irradiation, such as basic patient characteristics, performance status, the location and extension of recurrent disease, patient co-morbidities, current speech and swallowing function, the interval from the initial radiation therapy to recurrence, previously received doses by critical structures and prior treatment toxicity. Nevertheless, several questions remain unanswered. The purpose of this review is to evaluate the major issues in the field of re-irradiation regarding the current evidence. Therefore, the major selection criteria and new treatment strategies are discussed to define the ideal candidates to undergo re-irradiation and describe a practical approach to these patients. Given the limited evidence in this field, the optimal treatment of recurrent and second primary cancers remains to be defined. Future prospective study of this approach is warranted.

Mechanisms of taste bud cell loss after head and neck irradiation

Taste loss in human patients following radiotherapy for head and neck cancer is a common and significant problem, but the cellular mechanisms underlying this loss are not understood. Taste stimuli are transduced by receptor cells within taste buds, and like epidermal cells, taste cells are regularly replaced throughout adult life. This renewal relies on progenitor cells adjacent to taste buds, which continually supply new cells to each bud. Here we treated adult mice with a single 8 Gy dose of x-ray irradiation to the head and neck, and analyzed taste epithelium at 1-21 d postirradiation (dpi). We found irradiation targets the taste progenitor cells, which undergo cell cycle arrest (1-3 dpi) and apoptosis (within 1 dpi). Taste progenitors resume proliferation at 5-7 dpi, with the proportion of cells in S and M phase exceeding control levels at 5-6 and 6 dpi, respectively, suggesting that proliferation is accelerated and/or synchronized following radiation damage. Using 5-bromo-2-deoxyuridine birthdating to identify newborn cells, we found that the decreased proliferation following irradiation reduces the influx of cells at 1-2 dpi, while the robust proliferation detected at 6 dpi accelerates entry of new cells into taste buds. In contrast, the number of differentiated taste cells was not significantly reduced until 7 dpi. These data suggest a model where continued natural taste cell death, paired with temporary interruption of cell replacement, underlies taste loss after irradiation.

Effect of tumour-cell-derived or recombinant keratinocyte growth factor (KGF) on proliferation and radioresponse of human epithelial tumour cells (HNSCC) and normal keratinocytes in vitro

Purpose of this work was to test the effect of tumour-cell-derived keratinocyte growth factor (KGF) or recombinant KGF (palifermin) on cell proliferation and radiation response of human HNSCC cells and normal keratinocytes in vitro. Four tumour cell cultures derived from head and neck squamous cell carcinomas, primary keratinocytes, and immortalized keratinocytes were analysed. Fibroblasts, the natural source of KGF protein, served as controls. KGF expression was observed in primary and immortalized keratinocytes, fibroblasts, and in tumour cells, while significant KGF receptor expression was only found in keratinocytes. Recombinant KGF as well as tumour-cell-derived KGF caused a significant growth stimulation and radioprotection in keratinocytes, which was abolished by a neutralizing anti-KGF antibody. This indicates that tumour-cell-derived KGF is biologically active. In the tumour cell lines, no significant growth stimulation was induced by recombinant KGF, and the neutralizing antibody did not influence tumour cell growth or radiation response. Our results indicate that the normal, paracrine KGF regulatory mechanisms, which are based on KGF receptor expression, are lost in malignant cells, with the consequence of irresponsiveness of the tumour cells to exogenous KGF. In face of the amelioration of the radiation response of normal epithelia, demonstrated in various clinical and various preclinical animal studies, recombinant KGF represents a candidate for the selective protection of normal epithelia during radio(chemo) therapy of squamous cell carcinoma.

Reduction of oral mucositis by palifermin (rHuKGF): Dose-effect of rHuKGF

PURPOSE

The aim of the present study was to determine the dose effect of palifermin (recombinant human keratinocyte growth factor, rHuKGF) for reduction of the response of oral mucosa to fractionated radiotherapy in a mouse model.

MATERIAL AND METHODS

Ulceration (confluent mucositis) of mouse tongue epithelium was analysed as the clinically relevant endpoint. Palifermin at doses from 1 - 30 mg/kg was administered before the onset (day -3), at the end of the first (day +4) or the second week of irradiation (day +11) with 5 x 3 Gy/week. Each protocol was terminated by graded radiation test (top-up) doses. In a further experiment, optimally effective doses were given on days -3 and +4, or -3, +4 and +11.

RESULTS

Single dose irradiation of mouse mucosa yielded an ED50 (dose inducing ulcer in 50% of the mice) of 10.7 +/- 1.0 Gy. With fractionated irradiation for 1 week an ED50 for test irradiation (day +7) of 5.1 +/- 1.9 Gy was observed. After 2 weeks (day +14), the ED50 was 7.3 +/- 1.9 Gy. Palifermin significantly increased the ED50 values in all protocols tested. Maximally effective doses for single injections were 15.0 mg/kg (day -3, +11) or 22.5 mg/kg (day +4), which yielded ED50 values of 12.1 +/- 1.3 Gy, 13.7 +/- 1.5 Gy and 14.4 +/- 1.3 Gy, respectively. Higher palifermin doses did not further increase the ED50. Repeated injections on days -3 and +4 did not increase the ED50 beyond the value obtained with injections on day +4 alone. An additional injection on day +11 increased the ED50 further to 15.1 +/- 0.1 Gy.

CONCLUSIONS

A significant palifermin dose-effect was seen at doses below 15 mg/kg. However, a significant increase in oral mucosal radiation tolerance by palifermin over untreated control tissue was observed already with low doses of 1 mg/kg. This indicates that in clinical studies with palifermin, the dose of the growth factor may be of minor relevance over a wide dose range.

Mucocutaneous junction of eyelid and lip: a study of the transition zone using epithelial cell markers

PURPOSE

The expression of epithelial cell markers in the mouse eyelid and lip was investigated in order to understand the nature of the interactions of mucosal and skin epithelium as to how they form the mucocutaneous junction (MCJ).

METHODS

Cryosections of eyelid and lip tissue from normal mice were examined immunohistochemically with cytokeratins (CKs): CK1, CK4, CK5, CK6, CK10, CK13, CK14, and CK19; filaggrin; involucrin; and connexin 43.

RESULTS

The expression pattern varied across the MCJ, with the absence of CK1, CK10, and filaggrin in the mucosal epithelium; and CK4, CK6, and CK13 in the skin epidermis. CK5 and CK14 were consistently expressed in full-thickness skin, MCJ, and mucosa. CK19 was expressed basally, while involucrin-positive cells were found superficially in skin, MCJ, and mucosa. Connexin 43 was present in the MCJ, skin, and labial mucosa; however, little to no expression was seen in the palpebral conjunctiva.

CONCLUSION

The MCJ may be a focal point of mucosal epithelial cell differentiation activities. The similarity of staining patterns in the eyelid and lip suggests that the formation of these sites of shared interaction between the internal and external environment employs similar cellular mechanisms.

Effect of recombinant human keratinocyte growth factor (rHuKGF, Palifermin) on radiation-induced mouse urinary bladder dysfunction

PURPOSE

To determine the effect of Palifermin (rHuKGF) on acute and late radiation effects in mouse urinary bladder.

METHODS AND MATERIALS

Graded radiation doses were applied on day 0. Single subcutaneous injections of Palifermin (15 mg/kg) were given on day -2 or day +2. Changes in bladder function (i.e., a reduction in bladder volume by >or=50% of the individual preirradiation value) were assessed by cystometry.

RESULTS

Early changes in mouse bladder after irradiation occur in two phases. In the first early phase, a single injection of Palifermin on day -2 increased the ED(50) (dose associated with a positive bladder response in 50% of the mice) from 20.0 +/- 3.3 Gy to 27.1 +/- 6.9 Gy (p < .0051). Palifermin given on day +2 was not beneficial. No significant effects of Palifermin were seen in the second early phase. However, Palifermin administration before, but not after, irradiation, also modified late radiation effects, with an ED50 of 22.2 +/- 4.8 Gy compared with 16.2 +/- 4.9 Gy in control animals (p < .0187).

CONCLUSIONS

Initial early functional changes in the mouse urinary bladder after irradiation as well as late effects can be significantly reduced by a single administration of Palifermin before irradiation.

A novel animal model to investigate fractionated radiotherapy-induced alimentary mucositis: the role of apoptosis, p53, nuclear factor-kappaB, COX-1, and COX-2

Radiation-induced mucositis is a common and serious side effect of radiotherapy. Molecular mechanisms of mucosal injury, however, are still poorly understood and extremely difficult to study in humans. A novel Dark Agouti rat model using fractionated radiotherapy to induce mucositis has been developed to investigate the occurrence of alimentary mucosal injury. Twenty-four Dark Agouti rats were randomly assigned to receive either fractionated radiotherapy or no radiotherapy. The irradiated rats received a fractionated course of abdominal radiotherapy at 45 Gy/18 fractions/6 weeks treating thrice weekly (i.e., at a radiation dose of 2.5 Gy per fraction). After each week of radiation, a group of irradiated rats was killed. Histomorphology and mucin distribution in the alimentary tract was investigated. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay was used to examine apoptosis in the colon and jejunum, and intestinal morphometry was used to assess villus length, crypt length, and mitotic crypt count. Immunohistochemistry of p53, nuclear factor-kappaB, cyclooxygenase (COX)-1, and COX-2 was also done. The fractionated radiotherapy course induced alimentary mucositis from week 1, with more severe injury seen in the small intestine. The hallmark appearance of apoptosis was present in the crypts of the small and large intestine. In the jejunum and colon, goblet cell disorganization and degeneration was obvious and crypt mitotic counts were severely depleted throughout the treatment. Expression of p53, nuclear factor-kappaB, COX-1, and COX-2 was increased in the irradiated intestinal sections. Fractionated radiation-induced alimentary mucositis has been effectively documented in the Dark Agouti rat for the first time. Further studies investigating the molecular mechanisms underlying radiation-induced mucositis are planned to ultimately achieve anti-mucotoxic-targeted therapies.

EGFR-targeted anti-cancer drugs in radiotherapy: preclinical evaluation of mechanisms

Preclinical and clinical results indicate that the EGFR can mediate radioresistance in different solid human tumours. Combination of radiotherapy and EGFR inhibitors can improve local tumour control compared to irradiation alone and has been introduced into clinical radiotherapy practice. So far several mechanisms have been identified in preclinical studies to contribute to improved local tumour control after radiation combined with EGFR inhibitors. These include direct kill of cancer stem cells by EGFR inhibitors, cellular radiosensitization through modified signal transduction, inhibition of repair of DNA damage, reduced repopulation and improved reoxygenation during fractionated radiotherapy. Effects and mechanisms may differ for different classes of EGFR inhibitors, for different tumours and for normal tissues. The mechanisms underlying this heterogeneity are currently poorly understood, and predictive assays are not available yet. Importantly, mechanisms and predictors for the combined effects of radiation with EGFR inhibitors appear to be considerably different to those for application of EGFR inhibitors alone or in combination with chemotherapy. Therefore to further evaluate the efficacy and mechanisms of EGFR-inhibition in combined treatments, radiotherapy-specific preclinical research strategies, which include in vivo experiments using local tumour control as an endpoint, as well as animal studies on normal tissue toxicity are needed.

Effect of post-exposure administration of keratinocyte growth factor (Palifermin) on radiation effects in oral mucosa in mice

Oral mucositis is a severe component of the acute radiation syndrome. The present study was initiated to determine the potential of recombinant human keratinocyte growth factor (rHuKGF, Palifermin) to ameliorate oral mucositis in a mouse model after a single radiation exposure. A 3 x 3 mm(2 )area in the center of the lower tongue surface of C3H/Neu mice was irradiated with graded single doses of 25 kV X-rays. Acute mucosal ulceration was used as the quantal end-point for dose-response analyses. Palifermin was applied at a dose of 15 mg/kg on days 0, 1, 2, 3, 4 or 5. For comparison, three injections of 5 or 15 mg/kg on days 1-3 were administered. The ED(50) (dose at which ulceration is expected in 50% of the animals) for irradiation alone was 11.6 +/- 1.2 Gy. Mean latent time was 9.4 +/- 0.2 days; mean ulcer duration was 2.8 +/- 0.2 days. Single injections of rHuKGF did not result in a significant increase in isoeffective radiation doses at any of the administration days. However, the latent time to ulceration was significantly shortened by 1-2 days in all protocols. Repeated administration of rHuKGF (15 mg/kg) resulted a significant increase in ED50 to 16.8 +/- 4.0 Gy (P = 0.0047); the mean latent time was 4.4 +/- 0.9 days. Three injections of 5 mg/kg of Palifermin on days 1-3 yielded an ED50 of 19.4 +/- 1.7 Gy. In this protocol, mean latent time was 6.6 +/- 0.6 days. In conclusion, Palifermin has a potential to reduce the mucositis burden in patients after a single radiation exposure. Repeated injections are required. For three injections, a negative dose-effect of rHuKGF was observed. The optimum dose, number and timing of the administration require further investigation.

In vitro radiation-induced expression ofXPC mRNA as a possible biomarker for developing adverse reactions during radiotherapy

Repair of radiation-induced DNA damage is believed to play a critical role in developing adverse reactions during radiotherapy. Ionizing radiation induces transcription of several DNA repair genes including XPC as a part of the p53-transmitted stress response. XPC gene induction was measured to analyze whether it predicts occurrence of therapy-related acute side effects. Prostate cancer patients (n = 406) receiving radiotherapy were monitored for development of acute adverse effects using common toxicity criteria. For gene induction analysis, lymphocytes from 99 patients were selected according to their observed grade of clinical side effects. Cells were irradiated in vitro with 5 Gy and analyzed after 4 hr for XPC gene induction using reverse transcription and quantitative real-time PCR. Analysis of modulation of XPC induction by personal, clinical or lifestyle factors was included. Inter-individual induction of XPC expression by ionizing radiation varied up to 20-fold (0.29-5.77) and was significantly higher in current or exsmokers than in never-smokers (p value: 0.008). Patients with XPC induction above the 90th percentile compared to those with lower induction levels were at increased risk of suffering from adverse reactions during radiotherapy (odds ratio 5.3, 95% confidence interval 1.2-24.5; adjusted for smoking). In summary, XPC mRNA levels induced by ionizing radiation were shown for the first time to be strongly affected by smoking and to be associated with an approximately 5-fold increased risk for developing acute side effects of radiotherapy. The predictive value of DNA damage-induced XPC levels as a possible biomarker for radiosensitivity has to be further investigated.

Quantitative Analysis of Radiation-Induced DNA Break Repair in a Cultured Oral Mucosal Model

Oral mucositis is a major side effect of radiation therapy. Development of strategies for reduction of this problem calls for quantitative models. The goal of the present study was to test the feasibility of detecting double-strand breaks (DSBs) and DSB repair proteins upon radiation of mucosa in a 3-dimensional culture system using morphology and immunohistochemistry. Human oral keratinocytes and fibroblasts were seeded onto and into an acellular dermal carrier to produce a cultured mucosal substitute (CMS). CMSs were gamma-irradiated with 0, 2, and 12 Gy. One group received 4 Gy through 2 Gy fractions with a 24-h interval. Radiation-induced damage was quantified using hematoxylin and eosin (H&E). DSBs and DSB repair proteins were visualized and quantified using antibodies against P53 binding protein 1 (53BP1), MRE11, and RAD51. As in cell culture, CMSs showed intranuclear loci of damage and repair, mostly in the proliferative basal cell layers. Maximum percentages of damaged basal layer keratinocytes were 54.8% using H&E (12 Gy) up to 78.9% (12 Gy) for 53BP1. This study shows the feasibility of DNA repair markers to quantify radiation damage. This is an important step forward in the study of mucositis and the development of treatment and prevention strategies, proving once more the power and clinical importance of tissue engineering.

Emerging approaches for prophylaxis and management of oropharyngeal mucositis in cancer therapy

Oral mucositis is a common treatment-limiting side effect of cancer therapy that may have a significant impact on quality of life and on the cost of care. Oral mucositis is the most distressing complication of cancer therapy as reported by head and neck cancer patients, in patients receiving dose-dense myelosuppressive chemotherapy and in patients receiving haematopoietic stem cell transplant. Mucositis may increase the risk of local and systemic infection, particularly in myelosuppressed patients. Severe oral mucositis can lead to the need to interrupt or discontinue cancer therapy, and thus may impact cure of the primary disease. Current care of patients with mucositis is essentially palliative, and includes appropriate oral hygiene, nonirritating diet and oral care products, topical palliative mouth rinses, topical anaesthetics and use of systemic opioid analgesics. Emerging approaches for prevention and treatment of oral mucositis are developing based on an increasing understanding of the pathobiology of mucosal damage and repair. New interventions are expected to be administered based on the mechanisms of initiation, progression and resolution of the condition. The approval by the FDA of keratinocyte growth factor (palifermin; Amgen) in 2004 represents a new step in prevention of oral mucositis in stem cell transplant patients based on the increasing understanding of the pathogenesis of mucositis. Progress in the prevention and management of mucositis will improve quality of life, reduce cost of care and facilitate completion of more intensive cancer chemotherapy and radiotherapy protocols. Improved management of mucositis may allow implementation of cancer treatment protocols that are currently excessively mucotoxic, but have potentially higher cure rates of the malignant disease.

Association between TP53 and p21 genetic polymorphisms and acute side effects of radiotherapy in breast cancer patients

p53 and p21 play an important role in G1/S checkpoint control in response to ionizing radiation. Yet the genetic polymorphisms in these genes have not been investigated with respect to radiation toxicity in patients. We therefore assessed the association between TP53 Arg72Pro, p53PIN3 and p21 Ser31Arg polymorphisms and the risk of acute skin toxicity after radiotherapy in a prospective study of 446 female breast cancer patients (average age 60.3+/-9.0 years) receiving radiotherapy after breast conserving surgery. The p53PIN3 polymorphism was determined by standard PCR, and TP53 Arg72Pro and p21 Ser31Arg polymorphisms using melting point analysis of sequence-specific hybridization probes. The development of acute skin toxicity (moist desquamation) was modelled using Cox proportional hazards, accounting for cumulative biologically effective radiation dose. Overall, the development of acute skin toxicity, which presented in 77 patients, was not significantly associated with the polymorphisms studied. Risks were however differential by body mass index. Compared to non-carriers, TP53 72Pro carriers had a non-significantly decreased risk of acute skin toxicity in normal weight women (hazard ratio 0.46, 95% CI, 0.18-1.18) but not in overweight patients (hazard ratio 1.07, 95% CI, 0.61-1.89) (p(interaction) =0.14). Haplotype analysis for the TP53 polymorphisms suggested that effect modification by TP53 72Pro may differ according to the p53PIN3 allele (p(interaction)=0.06). Furthermore, in TP53 72Pro carriers with p21 Ser/Ser genotype, the occurrence of acute toxicity was reduced in normal weight but not overweight patients. In conclusion, the TP53 72Pro variant may be associated with the development of acute skin toxicity after radiotherapy in patients with normal weight. Large clinical studies are needed to clearly confirm this association.

Reduction of radiochemotherapy-induced early oral mucositis by recombinant human keratinocyte growth factor (palifermin): Experimental studies in mice

PURPOSE

To study the effect of recombinant human keratinocyte growth factor (rHuKGF or palifermin) on oral mucositis induced by radiochemotherapy in a mouse model.

METHODS AND MATERIALS

Cis-diamminedichloroplatinum (cisplatin) and/or 5-fluorouracil were given before single dose irradiation, combined with palifermin before or after the treatment, or both. Daily fractionated irradiation for 2 weeks was followed by graded test doses. With additional chemotherapy in Week 1, palifermin was given before radiotherapy and at the end of the first week, or additionally at the end of Week 2. Radiochemotherapy in Week 2 was combined with palifermin at the end of Weeks 1 and 2, Weeks 1, 2, and 3, or additionally before radiotherapy. Ulceration of mouse tongue mucosa was analyzed as the endpoint.

RESULTS

The dose associated with ulcer induction in 50% of the mice (ED(50)) for single-dose irradiation was 11.5 +/- 0.7 Gy. Palifermin increased the ED(50) to about 19 Gy in all protocols tested. Similar values were observed when chemotherapy was added before irradiation. With fractionated irradiation, palifermin increased the ED(50) for test irradiation from 5.7 +/- 1.5 Gy to 12-15 Gy, depending on the administration protocol. With chemotherapy in Week 1, two palifermin injections had no significant effect, but a third injection increased the ED(50) to 13 Gy. With chemotherapy in Week 2, all palifermin protocols resulted in ED(50) values of 13-14 Gy.

CONCLUSION

A marked increase in oral mucosal radiation tolerance by palifermin was found, which was preserved in combinations with chemotherapy using cisplatin and/or 5-fluorouracil.

Effects of keratinocyte growth factor (palifermin) administration protocols on oral mucositis (mouse) induced by fractionated irradiation

BACKGROUND AND PURPOSE

Aim of this study was to assess the impact of the administration protocol of palifermin on amelioration of oral mucositis after fractionated irradiation.

MATERIALS AND METHODS

Mouse tongue ulceration was analysed as the clinically relevant endpoint. Daily fractionated irradiation (5 x 3 Gy/week, days 0 to +4, +7 to +11, with a weekend gap on days +5 and +6) was followed by graded test doses on day +14, i.e. after a second weekend gap. Palifermin (5 mg/kg) was injected subcutaneously. In the first series of experiments, the effect of three daily injections (days -3, -2 and -1) was compared with a single administration either on day -2 or -1; all animals received a further injection on day +4. In the second series, a single or three injections were given in the weekend gap between fractionated irradiation (days +5 to +6), with an additional administration on day +11. In a final protocol, single weekly injections of palifermin were given either on days -3, +4 and +11, days +4, +11 and +18, or on days -3, +4, +11 and +18.

RESULTS

The ED50 (dose after which ulcer induction is expected in 50% of the mice) to single dose irradiation was 11.5+/-0.7 Gy. The ED50 for test irradiation after 10 x 3 Gy was 5.7+/-1.6 Gy. Palifermin administration before the start of fractionated irradiation and on day +4 increased the ED50 to 10-12 Gy, administration over the first weekend and on day +11 to 11-15 Gy. Administration over three consecutive weekends, starting on day -3 or day +4, increased the ED50 to 13.0+/-0.1 and 14.9+/-0.3 Gy. Single weekly KGF administrations over four weekends, including the weekend prior to and after completion of radiotherapy, showed no further increase in ED50.

CONCLUSIONS

A single palifermin injection during the weekend gap before or during fractionated irradiation is as effective as three applications. Onset of the palifermin treatment during the first weekend gap between fractionated irradiation is more effective than during the weekend before radiotherapy. The effect of palifermin on oral mucositis can be increased by three weekly injections, while four injections do not yield a further increase in ED50.

Molecular Marker Profiles Predict Locoregional Control of Head and Neck Squamous Cell Carcinoma in a Randomized Trial of Continuous Hyperfractionated Accelerated Radiotherapy

PURPOSE

Identification of factors that assist prediction of tumor response to radiotherapy may aid in refining treatment strategies and improving outcome. Possible association of molecular marker expression profiles with locoregional control of head and neck squamous cell carcinoma was investigated in a randomized trial of conventional versus continuous hyperfractionated accelerated radiotherapy (CHART).

EXPERIMENTAL DESIGN

Tumor material was obtained from 402 patients. Immunohistochemistry was used to assess Ki-67, CD31, p53, Bcl-2, and cyclin D1 expression. A hierarchical clustering algorithm with a Bayesian information criterion was used to group tumors with similar marker expression; resulting expression profiles were then compared in terms of their difference in outcome after CHART and conventionally fractionated radiotherapy.

RESULTS

Molecular marker profile was an independent prognostic factor for locoregional control. This was confirmed in multivariate analysis, including clinical variables such as tumor and nodal status, primary site, histological grade, age, and gender (P < 0.001 and P = 0.006 for local and nodal relapse, respectively). In particular, Bcl-2-positive tumors responded significantly better than average in both arms of the trial. Tumors negative for p53- and Bcl-2, with high and randomly patterned Ki-67 expression, responded worse than average with no benefit from CHART. Tumors with similarly negative p53 and Bcl-2, but low Ki-67 staining, with an organized pattern, benefit significantly from CHART schedule.

CONCLUSIONS

This study demonstrates the potential of molecular profiles to predict radiotherapy response of head and neck squamous cell carcinoma and for treatment stratification. Distinct expression profiles correlate with three distinct clinical phenotypes, including good locoregional control, poor locoregional control, and an outcome strongly dependent upon fractionation schedule.

Changes in the effect of dose fractionation during daily fractionated irradiation: studies in mouse oral mucosa

PURPOSE

The aim of the present study was to quantify the fractionation effect in mouse oral mucosa during a daily fractionated protocol.

METHODS AND MATERIALS

Irradiation of the snout of C3H mice was performed with 5 x 3 Gy/week. In the first experiment, graded test doses were applied to the lower tongue on Days 4, 7, 11, 14, or 18. Subsequently, a split-dose experiment was performed on the same days with 1, 2, 3, or 5 fractions (graded doses).

RESULTS

The ED50 (dose expected to induce ulcer in 50% of the mice) for untreated mucosa was 10.7 +/- 1.0 Gy. Fractionated irradiation with 5 x 3 Gy/week yielded an ED50 for top-up irradiation of 6.5 +/- 1.8 Gy, 6.8 +/- 0.9 Gy, 5.3 +/- 2.1 Gy, 7.3 +/- 1.9 Gy, and 7.5 +/- 1.3 Gy on Days 4, 7, 11, 14, and 18. The ED50 values for split-dose irradiation on Day 4 increased from 6.24 +/- 1.48 Gy (1 fraction) to 9.96 +/- 1.47 Gy (5 fractions). Similarly, an increase from 4.04 +/- 1.56 Gy to 10.07 +/- 1.9 Gy was found on Day 11, and from 5.84 +/- 2.37 Gy to 9.81 +/- 2.29 Gy on Day 18. After the weekend breaks, values between 6.22 +/- 1.60 Gy (1 fraction) and 4.7 +/- 1.95 Gy (5 fractions) were observed on Day 7, and between 5.62 +/- 1.36 Gy and 5.98 +/- 2.01 Gy on Day 14.

CONCLUSIONS

These results indicate that the fractionation effect in oral mucosa is consistently lost over the weekends and restored during the treatment weeks.