A murine model of lip epidermal/mucosal reactions to X-irradiation

Characterization of a novel dual murine model of chemotherapy-induced oral and intestinal mucositis

Oral and intestinal mucositis are debilitating inflammatory diseases observed in cancer patients undergoing chemo-radiotherapy. These are devastating clinical conditions which often lead to treatment disruption affecting underlying malignancy management. Although alimentary tract mucositis involves the entire gastrointestinal tract, oral and intestinal mucositis are often studied independently utilizing distinct organ-specific pre-clinical models. This approach has however hindered the development of potentially effective whole-patient treatment strategies. We now characterize a murine model of alimentary tract mucositis using 5-Fluorouracil (5-FU). Mice were given 5-FU intravenously (50 mg/kg) or saline every 48 h for 2 weeks. Post initial injection, mice were monitored clinically for weight loss and diarrhea. The incidence and extent of oral mucositis was assessed macroscopically. Microscopical and histomorphometric analyses of the tongue and intestinal tissues were conducted at 3 interim time points during the experimental period. Repeated 5-FU treatment caused severe oral and intestinal atrophy, including morphological damage, accompanied by body weight loss and mild to moderate diarrhea in up to 77.8% of mice. Oral mucositis was clinically evident throughout the observation period in 88.98% of mice. Toluidine blue staining of the tongue revealed that the ulcer size peaked at day-14. In summary, we have developed a model reproducing the clinical and histologic features of both oral and intestinal mucositis, which may represent a useful in vivo pre-clinical model for the study of chemotherapy-induced alimentary tract mucositis and the development of preventative therapies.

Antibiotic-Induced Gut Microbiota Depletion Accelerates the Recovery of Radiation-Induced Oral Mucositis in Rats

PURPOSE

Due to its pivotal role in the modulation of immune and inflammatory responses, the gut microbiota has emerged as a key modulator of cancer treatment-induced gastrointestinal mucositis. However, it is not clear yet how it affects radiation therapy-induced oral mucositis (OM). As such, this study aimed to explore the gut microbiota's role in the pathogenesis of radiation-induced OM in rats.

METHODS AND MATERIALS

Male Sprague Dawley rats were treated with 20 Gy x-ray radiation (Rx) delivered to the snout, with or without antibiotic-induced microbiota depletion (AIMD). OM severity was assessed, and tongue tissues were collected on day 9 and 15 postradiation for tissue injury and inflammatory markers assessment.

RESULTS

AIMD+Rx had a significantly shorter duration of severe OM compared with Rx alone group. Macroscopically, the tongue ulcer-like area was smaller in AIMD+Rx compared with the Rx group. Microscopically, a smaller percentage of the mucosal ulcer was observed in the dorsal tongue of AIMD+Rx compared with the Rx group. AIMD+Rx also had significantly lower levels of interleukin 6, interleukin 1 beta, and toll like receptor 4 in the tongue tissues than the Rx group.

CONCLUSIONS

The gut microbiota plays a role in OM pathogenesis, mainly in the recovery phase, through the modulation of proinflammatory pathways. Future microbiota-targeted interventions may improve OM in clinical settings.

Investigation of the protective effect of gel incorporating Eugenia jambolana leaf extract on 5-fluorouracil-induced oral mucositis: an animal study

PURPOSE

The study aimed to evaluate the possible preventive effect of two concentrations (3 and 5% w/w) of Eugenia jambolana (EJ) extract against 5-FU-induced mucositis.

METHOD

Sixteen adult rats were separated into four groups: two control and two preventive groups. Animals in Groups 1, 2, and 3 were injected intraperitoneally with 60 mg/kg/day of 5-FU on Day 1 followed by 150 mg/kg/day on Day 5. The rats in Group 4 (negative control) were given physiological saline at the same times and doses. Furthermore, on the fifth day of the study, the cheek and sublingual mucosa were irritated by external superficial scratches using the tip of an 18-G needle, followed by the application 15 µL of 20% acetic acid, after which 3 and 5% EJ w/w gels were applied topically for animals in Groups 2 and 3, respectively.

RESULTS

The weight and the mucositis scores were recorded. Antioxidant and anti-inflammatory markers and biochemical tests were analyzed. Significant differences were found between the study groups in weight loss, clinical mucositis scores, mortality rates, and antioxidant and anti-inflammatory parameters.

CONCLUSION

The preventive effect of 3% gel was significant, with no mortality rate, making it an option for preventive strategies.

The effect of systemic application of propolis on tongue damage and oral mucositis in rats exposed to radiation

PURPOSE

In this experimental study, the effect of dose-dense systemic application of propolis on oral mucosity, histological changes in papilla, and inflammatory and hypoxic markers in rats exposed to radiation was investigated.

METHODS

Seven rats were in the control and 30 rats in the experimental group. Three experimental groups were formed. In Group 1 RT (15 Gy) was delivered only to the head and neck region. In Group 2, RT (15 Gy) and systemic administration of 100 mg/kg/ml propolis, in Group 3, RT (15 Gy) and systemic administration of 200 mg/kg/ml propolis were applied. Oral mucositis index (OMI) was scored in control and experimental groups. Proinflammatory markers [interleukin-6 (IL-6), myeloperoxidase (MPO), tumor-necrosis factor-α (TNF-α)] hypoxia markers [glucose transporter-1 (GLUT-1), hypoxia-inducible factor 1α (HIF-1α)] were studied histomorphologically.

RESULTS

The significantly highest OMI score was observed in the G1. OMI score was statistically significantly decreased in experimental groups receiving systemic propolis, especially in G3. Proinflammatory markers increased significantly only in the experimental RT group, G1. Serum levels of MPO and TNF-α significantly decreased in the dose-dense systemic propolis arm. The highest levels of hypoxia markers (HIF-1α and GLUT-1) were detected in the RT group, then in G2, G3, and control groups in order of decreasing frequency. However, the difference between the groups did not reach the level of statistical significance.

CONCLUSION

Systemic propolis can be reduced acute mucositis with its anti-inflammatory effect without developing resistance to RT (tumor protection). However, greater number of clinical studies should be designed to arrive at definitive conclusions.

Sumatriptan alleviates radiation-induced oral mucositis in rats by inhibition of NF-kB and ERK activation, prevention of TNF-α and ROS release

OBJECTIVES

Oral mucositis caused by radiation therapy is a common problem in cancer patients, especially those with head and neck cancer. Numerous experimental and clinical studies have attempted to find a drug to alleviate oral mucositis. Sumatriptan, is conventionally used to treat migraine attack and cluster headache. Recently, low doses have been shown to have anti-inflammatory properties. In this study we aimed to measure the effect of sumatriptan on experimental radiotherapy-induced oral mucositis.

MATERIAL AND METHODS

This study evaluates the use of sumatriptan 0.3 and 1 mg/kg in radiation-induced oral mucositis. In order to induce oral mucositis, six rats from each group received 8-Gy of X-ray in a single session. Likewise, three rats from each group received 26-Gy of X-ray. The latter dose of X-ray was used for inducing severe mucositis and apoptosis evaluation by TUNEL assay, while the first dose was used for histopathological and molecular assessments. On 8th day after irradiation, specimens were collected from their tongues for histology, TUNEL and molecular assessments.

RESULTS

Radiation caused mucosal atrophy, derangement of the tissue and vasodilation. Sumatriptan significantly decreased histopathological score and alleviated mucosal atrophy. As well, there was no evidence of vasodilation in the sumatriptan group. Likewise, sumatriptan decreased the increased level of NF-kB and prevented its activation as well as ERK phosphorylation. In addition, Sumatriptan-treated rats had lower tissue level of TNF-α, reactive oxygen species and fewer apoptotic cells in TUNEL assay.

CONCLUSION

Based on study results, sumatriptan mitigate radiation-induced oral mucositis by inhibiting NF-kB, ERK and limiting the release of TNF-α, oxidative stress factor and apoptosis.

Differential therapeutic effects of PARP and ATR inhibition combined with radiotherapy in the treatment of subcutaneous versus orthotopic lung tumour models

Background

Subcutaneous mouse tumour models are widely used for the screening of novel antitumour treatments, although these models are poor surrogate models of human cancers.

Methods

We compared the antitumour efficacy of the combination of ionising radiation (IR) with two DNA damage response inhibitors, the PARP inhibitor olaparib and the ATR inhibitor AZD6738 (ceralasertib), in subcutaneous versus orthotopic cancer models.

Results

Olaparib delayed the growth of irradiated Lewis lung carcinoma (LL2) subcutaneous tumours, in agreement with previous reports in human cell lines. However, the olaparib plus IR combination showed a very narrow therapeutic window against LL2 lung orthotopic tumours, with nearly no additional antitumour effect compared with that of IR alone, and tolerability issues emerged at high doses. The addition of AZD6738 greatly enhanced the efficacy of the olaparib plus IR combination treatment against subcutaneous but not orthotopic LL2 tumours. Moreover, olaparib plus AZD6738 administration concomitant with IR even worsened the response to radiation of head and neck orthotopic tumours and induced mucositis.

Conclusions

These major differences in the responses to treatments between subcutaneous and orthotopic models highlight the importance of using more pathologically relevant models, such as syngeneic orthotopic models, to determine the most appropriate therapeutic approaches for translation to the clinic.

The Japanese herbal medicine Hangeshashinto enhances oral keratinocyte migration to facilitate healing of chemotherapy-induced oral ulcerative mucositis

Chemotherapy often induces oral ulcerative mucositis (OUM) in patients with cancer, characterized by severe painful inflammation. Mouth-washing with the Japanese herbal medicine hangeshashinto (HST) ameliorates chemotherapy-induced OUM in patients with colorectal cancer. Previously, we demonstrated that HST decreased interleukin 1β-induced prostaglandin E2 production in human oral keratinocytes (HOKs) and OUM-induced mechanical or spontaneous pain in rats. However, HST effects on tissue repair functions in HOKs remain unclear. Here, we examined the effects of HST on scratch-induced wound healing in vitro and in vivo. In vitro, HST enhanced wound healing mainly through scratch-induced HOK migration. Screening of the seven constituent medicinal herbs and their major components revealed that Scutellaria root, processed ginger, and Glycyrrhiza components mainly induced the scratch-induced HOK migration. Pharmacokinetic analyses indicated that the active ingredient concentrations in rat plasma following oral HST administration were below the effective doses for HOK migration, suggesting direct effects of HST in OUM. Mitogen-activated protein kinase and C-X-C chemokine receptor 4 inhibitors significantly suppressed HST-induced HOK migration. Moreover, HST enhanced tissue repair in our OUM rat model. Thus, HST likely enhanced OUM tissue repair through oral keratinocyte migration upon MAPK and CXCR4 activation and may be useful in patients with cancer-associated OUM.

Beneficial Biological Activities of Cinnamomum osmophloeum and its Potential Use in the Alleviation of Oral Mucositis: A Systematic Review

The aim of this review was to provide an updated overview of studies on the medical-biological activities of Cinnamomum osmophloeum (C. osmophloeum) in vitro and in vivo and the potential therapeutic use of natural agents prepared from this plant for the alleviation of oral mucositis (OM). Reported articles were collected using web search engine tools. The systematic review was organized according to the preferred reporting items for reviews and meta-analyses (PRISMA) statement. Additional sources were identified through cross-referencing to identify the potential use of C. osmophloeum in the alleviation of OM. The results disclosed that C. osmophloeum is comprised of bioactive ingredients that could act diversely as a reagent in anti-inflammation, antibacterial, antioxidant, anti-hyperglycemic, antidyslipidemia, anti-cancer, renal disease therapy and anti-hyperuricemia capacities. Recent studies revealed that the overall effects on anti-inflammation, wound repair, and the antibacterial and antioxidant activities of its constituents would act as a potential remedy for oral mucositis. Up-to-date in vitro and in vivo studies on the medical-biological activities of C. osmophloeum suggested that C. osmophloeum and its constituents could be promising remedies as adjuvants in OM therapy and warrant further investigation.

Hyposalivation due to chemotherapy exacerbates oral ulcerative mucositis and delays its healing

OBJECTIVES

Cancer therapy including chemotherapy causes gland atrophy, resulting in low salivary secretion in cancer patients. Since saliva plays an important role in oral health, the dysfunction may exacerbate oral ulcerative mucositis (OUM), which is another side effect. Here, we investigated the effect of hyposalivation on OUM using sialoadenectomized rats and examined the effects of anticancer drugs on the salivary glands.

DESIGN

As models for hyposalivation, the bilateral submandibular and sublingual glands except (2EXT) or together with (3EXT) the parotid glands were extracted. At 16 days after the procedure, OUM was experimentally developed by topical acetic acid treatment on the labial fornix region of the inferior incisors, and the severity and bacterial loading level were evaluated. The salivary gland weights and histology were analyzed after administration of the representative anticancer drugs 5-fluorouracil or cisplatin.

RESULTS

The severity of OUM was greater in both the 3EXT and 2EXT rats and delayed the healing process compared with that in sham rats without salivary gland extraction. The healing process in the 3EXT rats was longer than that in the 2EXT rats. The number of colony-forming units in the ulcerative region from the 3EXT rats was 10-fold greater than that in the sham rats. Both 5-fluorouracil and cisplatin reduced glands weights and damaged the salivary glands.

CONCLUSIONS

These results suggest that chemotherapy-induced hyposalivation exacerbates OUM and delays healing, most likely due to loss of salivary clearance and antimicrobial functions. This study illustrates the significance of oral health care for cancer patients undergoing chemotherapy.

TRIM33 deficiency in monocytes and macrophages impairs resolution of colonic inflammation

BACKGROUND

Mature myeloid cells play a crucial role in Crohn's disease (CD) but the molecular players that regulate their functions in CD are not fully characterized. We and others have shown that TRIM33 is involved in the innate immune response and in the inflammatory response but TRIM33 role in intestinal inflammation is not known. In this study, we investigated the role of TRIM33 in myeloid cells during dextran sulfate sodium (DSS)-induced colitis.

METHODS

We study the role of TRIM33 during DSS-induced colitis which mimics intestinal inflammation using mice deleted for Trim33 only in mature myeloid cells (Trim33-/- mice) FINDINGS: We first show that Trim33 mRNA level is decreased in CD patient's blood monocytes suggesting a role of TRIM33 in CD. Using Trim33-/- mice, we show that these mice display an impaired resolution of colonic inflammation with an increased number of blood and colon monocytes and a decreased number of colonic macrophages. Trim33-/- monocytes are less competent for recruitment and macrophage differentiation. Finally, during resolution of inflammation, Trim33-/- colonic macrophages display an impaired M1/M2 switch and express a low level of membrane-bound TNF that is associated with an increased number of colonic neutrophils.

INTERPRETATION

Our study shows an important role of TRIM33 in monocytes/macrophages during DSS-induced colitis and suggests that the decreased expression of TRIM33 in CD patient's blood monocytes might not be a consequence but might be involved in CD progression. FUND: La Ligue contre le Cancer (équipe labelisée), INSERM, CEA, Université Paris-Diderot, Université Paris-Sud.

Is submucosal fat injection effective in atrophic rhinitis? An experimental animal study

Atrophic rhinitis (AR) is a disease characterized by the extensive dilatation of the nasal cavity and atrophy of the mucosa, submucosa and bone tissue. Its etiological factors are unknown. There is not a satisfying treatment yet and the treatment of the functional impairment in the atrophic cells is still subject to investigation. The objective of this study is to determine at the histopathological level the possible effects of the submucosal fat injection in an experimental model of AR. 12 albino Wistar-Hannover male rats were included in the study. AR was induced with the Pasteurella multocida toxin, which was diluted with saline. As one of the rats died during the study, it was excluded from the evaluation. The right nasal cavities of all rats (11 nasal cavities) were defined as the control group (Group 1). Fat tissue obtained from the abdominal area was injected in the seven left nasal cavities (Group 2). All injections, which were done to the abdominal regions were also done in the left nasal cavities of the remaining four rats, which constituted the sham group (Group 3). After 14 days, all rats were decapitated and the squamous metaplasia and keratinization in the superficial epithelium, degeneration, vacuolar changes in the basal layer, congestion, inflammatory infiltration, vascular proliferation and glandular atrophy in the submucosa are histopathologically classified. The results were analyzed with statistical methods. Although glandular atrophy was significantly regressed in the fat injection group (Group 2) compared to other groups (p < 0.05), the remaining parameters did not show any significant difference among these three groups. The histopathological effect of the fat injection was modest. We concluded that fat injection treatment has no or at the most a very limited effect in the treatment of atrophic rhinitis.

Effect of Transplantation of Bone Marrow Derived Mesenchymal Stem Cells and Platelets Rich Plasma on Experimental Model of Radiation Induced Oral Mucosal Injury in Albino Rats

Normal tissue damage following radiotherapy is still a major problem in cancer treatment. Therefore, the current work aimed at exploring the possible role of systemically injected bone marrow derived mesenchymal stem cells (BM-MSCs) and/or locally injected platelet rich plasma (PRP) in ameliorating the side effects of ionizing radiation on the rat's tongue. Twelve rats served as control group (N) and 48 rats received a single radiation dose of 13 Gy to the head and neck region; then, they were equally divided into 4 experimental groups: irradiated only (C), irradiated + MSCs (S), irradiated + (PRP) (P), and combined group (PS). Animal scarification occurred in 3 and 7 days after radiation. Then, tongues were dissected and examined histologically and for expression of bcl-2 by RT-PCR. Histological examination of the treated groups (S), (P), and (PS) revealed an obvious improvement in the histological structure of the tongue, compared to group (C), in addition to upregulated expression of bcl-2, indicating decreased apoptotic activity. Conclusion. BM-MSCs and PRP have shown positive effect in minimizing the epithelial atrophy of normal oral mucosa after regional radiotherapy, which was emphasized by decreasing apoptotic activity in these tissues. Nevertheless, combined use of BM-MSCs and PRP did not reveal the assumed synergetic effect in oral tissue protection.

Distinct TRPV1- and TRPA1-based mechanisms underlying enhancement of oral ulcerative mucositis-induced pain by 5-fluorouracil

In many patients with cancer, chemotherapy-induced severe oral ulcerative mucositis causes intractable pain, leading to delays and interruptions in therapy. However, the pain mechanism in oral ulcerative mucositis after chemotherapy has not been extensively studied. In this study, we investigated spontaneous pain and mechanical allodynia in a preclinical model of oral ulcerative mucositis after systemic administration of the chemotherapy drug 5-fluorouracil, using our proprietary pain assay system for conscious rats. 5-Fluorouracil caused leukopenia but did not induce pain-related behaviors. After 5-fluorouracil administration, oral ulcers were developed with topical acetic acid treatment. Compared with saline-treated rats, 5-fluorouracil-exposed rats showed more severe mucositis with excessive bacterial loading due to a lack of leukocyte infiltration, as well as enhancements of spontaneous pain and mechanical allodynia. Antibacterial drugs, the lipid A inhibitor polymyxin B and the TRPV1/TRPA1 channel pore-passing anesthetic QX-314, suppressed both the spontaneous pain and the mechanical allodynia. The cyclooxygenase inhibitor indomethacin and the TRPV1 antagonist SB-366791 inhibited the spontaneous pain, but not the mechanical allodynia. In contrast, the TRPA1 antagonist HC-030031 and the N-formylmethionine receptor FPR1 antagonist Boc MLF primarily suppressed the mechanical allodynia. These results suggest that 5-fluorouracil-associated leukopenia allows excessive oral bacterial infection in the oral ulcerative region, resulting in the enhancement of spontaneous pain through continuous TRPV1 activation and cyclooxygenase pathway, and mechanical allodynia through mechanical sensitization of TRPA1 caused by neuronal effects of bacterial toxins. These distinct pain mechanisms explain the difficulties encountered with general treatments for oral ulcerative mucositis-induced pain in patients with cancer and suggest more effective approaches.

A PPAR gamma agonist protects against oral mucositis induced by irradiation in a murine model

BACKGROUND

Due to its anti-inflammatory, antifibrotic and antineoplastic properties, the PPAR gamma agonist rosiglitazone is of interest in prevention and therapy of radiation-induced toxicities. We aimed to evaluate the radioprotective effect of rosiglitazone in a mouse model of radiation-induced oral mucositis.

MATERIAL AND METHODS

Oral mucositis was obtained by irradiation of the oral region of C57BL/6J mice, pretreated or not with rosiglitazone. Mucositis was assessed by macroscopic scoring, histology and molecular analysis. Tumor xenograft was obtained by s.c. injection of Hep-2 cells in CD1 mice. Tumor volume was measured twice a week to evaluate effect of rosiglitazone alone and combined with radiotherapy.

RESULTS

Irradiated mice showed typical features of oral mucositis, such as oedema and reddening, reaching the peak of damage after 12-15days. Rosiglitazone markedly reduced visible signs of mucositis and significantly reduced the peak. Histological analysis showed the presence of an inflammatory cell infiltrate after irradiation; the association with rosiglitazone noticeably reduced infiltration. Rosiglitazone significantly inhibited radiation-induced tnfα, Il-6 and Il-1β gene expression. Rosiglitazone controlled the increase of TGF-β and NF-kB p65 subunit proteins induced by irradiation, and enhanced the expression of catalase. Irradiation and rosiglitazone significantly reduced tumor volume as compared to control. Rosiglitazone did not protect tumor from the therapeutic effect of radiation.

CONCLUSION

Rosiglitazone exerted a protective action on normal tissues in radiation-induced mucositis. Moreover, it showed antineoplastic properties on head-neck carcinoma xenograft model and selective protection of normal tissues. Thus, PPAR gamma agonists should be further investigated as radioprotective agents in head and neck cancer.

Dark Agouti rat model of chemotherapy-induced mucositis: establishment and current state of the art

Mucositis is a major oncological problem. The entire gastrointestinal and genitourinary tract and also other mucosal surfaces can be affected in recipients of radiotherapy, and/or chemotherapy. Major progress has been made in recent years in understanding the mechanisms of oral and small intestinal mucositis, which appears to be more prominent than colonic damage. This progress is largely due to the development of representative laboratory animal models of mucositis. This review focuses on the development and establishment of the Dark Agouti rat mammary adenocarcinoma model by the Mucositis Research Group of the University of Adelaide over the past 20 years to characterize the mechanisms underlying methotrexate-, 5-fluorouracil-, and irinotecan-induced mucositis. It also aims to summarize the results from studies using different animal model systems to identify new molecular and cellular markers of mucositis.

The relationship between the severity of radiation-induced oral mucositis and the myeloperoxidase levels in rats

OBJECTIVE

Oral mucositis is a common adverse reaction to radiotherapy for head and neck cancer, and there are concerns regarding a decreased quality of life in patients receiving radiotherapy. The purpose of this study was to investigate the relationship between the severity of radiation-induced oral mucositis and the myeloperoxidase (MPO) levels in irradiated tissues.

STUDY DESIGN

Ninety-six F344 rats were divided into the following 4 groups: 10-Gy, 18-Gy, and 30-Gy irradiation groups, and a nonirradiation group. Oral mucositis was induced by the administration of single doses of radiation via exposure. After irradiation, the rats were evaluated on the basis of weight measurements, macroscopic findings according to a grading scale (Oral Mucositis Index [OMI]), and the results of tissue MPO assays.

RESULTS

Weights decreased whereas the OMI scores and MPO levels increased, depending on the dose of exposure. The Spearman rank correlation test showed a significant correlation between the OMI scores and the MPO levels in the tissues with a correlation coefficient of 0.824 (P < .01).

CONCLUSIONS

In this study, the MPO levels in the irradiated tissue were increased in the cases involving severe radiation-induced oral mucositis evaluated in rats using a grading scale.

Effect of Iranian Propolis on Salivary Total Antioxidant Capacity in Gamma-irradiated Rats

Background and aims. The antioxidant and anti-inflammatory properties of propolis were studied. Since saliva containsantioxidants and radiotherapy of the head and neck mainly affects the saliva, salivary antioxidant defensive mechanism iscompromised with oxidative stress produced by radiation therapy. Therefore, the aim of the present study was to investigatethe effect of propolis on salivary total antioxidant capacity in irradiated rats. Materials and methods. The study was conducted on 28 rats, 7-11 weeks of age (160±20 g), divided into four groups:saline with no radiation (S), saline and radiation (SR), propolis with no radiation (P) [400 mg/kg IP], propolis and radiation(PR) [400 mg/kg IP]. SP and PR were exposed to 15 Gy of gamma irradiation for 7 minutes and 39 seconds. The rats received intraperitoneal injections each day for 10 days, and their tongues and lips were daily examined for mucositis; salivasample were also taken three times on days 0, 6, and 10. Results. Mucositis incidence appeared to be delayed in the PR compared to the SR, and the severity was significantlyhigher in the SR compared to the PR. No significant alterations were observed in salivary antioxidant levels during the ex-periment, except the SR group in which a significant reduction was found. Conclusion. Propolis might reduce and delay radiation-induced mucositis in animal models; it might be able to prevent thereduction in salivary antioxidant levels in irradiated rats as well.

Protective effects of aqueous extract of Solanum nigrum Linn. leaves in rat models of oral mucositis

Oral mucositis is one of the most debilitating side effects in patient undergoing chemotherapy or chemoradiotherapy. Leaves of the plant Solanum nigrum are used in folklore medicine to treat oral ulcers in India. However, no pharmacological investigation has been carried out till date. Aqueous extract of Solanum nigrum leaves (AESN) was prepared and subjected to various phytochemical screening. HPLC analysis of the ethyl acetate fraction was carried out. The aqueous extract (100 and 200 mg/kg) was further evaluated for its protective effect on two rat models: (a) busulfan plus infrared radiation (chemoradiotherapy) induced oral mucositis and (b) methotrexate (chemotherapy) induced oral mucositis. Various parameters including body weight change, food intake, and mortality were measured. AESN showed protective effect in both models of oral mucositis; however, the higher dose was more effective in chemotherapy induced oral mucositis. A reduction in oral mucositis score (P < 0.05) was observed in the treatment groups. Significant (P < 0.05) improvement in food intake was also observed in AESN treated groups. Aqueous extract of Solanum nigrum leaves has protective effect on chemotherapy and chemoradiotherapy induced oral mucositis in rats.

Assessment of the effect of local application of amifostine on acute radiation-induced oral mucositis in guinea pigs

The aim of present study was to assess the radioprotective effects of the local application of amifostine to treat acute buccal mucositis in guinea pigs. A total of 32 guinea pigs were randomized into four groups: (Group A) topically administered 50 mg of amifostine plus radiotherapy (RT); (Group B) 100 mg amifostine plus RT; (Group C) normal saline plus RT; and (Group D) normal saline plus sham RT. The opportunity for administration was 15 min before irradiation. When administered, the cotton pieces that had been soaked with 0.5 ml amifostine solution or saline were applied gently on the buccal mucosa of each guinea pig for 30 min. The animals in Groups A, B and C were irradiated individually with a single dose of 30 Gy to the bilateral buccal mucosa. Eight days after irradiation, the animals were scored macroscopically; they were then euthanized, and the buccal mucosal tissues were processed for hematoxylin-eosin staining and ICAM-1 immunohistochemical analysis. In Groups A and B, the mean macroscopic scores were 2.9 ± 0.6 and 2.4 ± 1.1, respectively. There was no significant difference between the two groups (P > 0.05). However, when they were separately compared with Group C (4.4 ± 0.7), a noticeable difference was obtained (P < 0.05). No mucositis was observed in Group D. Comparisons of the expression of ICAM-1 were in agreement with the macroscopic data. Histologically, superficial erosion, exudate and ulcer formation were all observed in the RT groups; only the severity and extent were different. The microscopic observations in the amifostine-treated groups were better than in Group C. The results demonstrated that topical administration of amifostine to the oral mucosa is effective treatment of acute radiation-induced mucositis.

A rat model against chemotherapy plus radiation-induced oral mucositis

OBJECTIVES

Present study was aimed at developing an experimental model of oral mucositis in rats using a combination of chemotherapeutic agent and radiation.

STUDY DESIGN

Female Wistar rats (150-200 g) were divided into 3 groups (n = 6). Rats in group 1 (normal control) and group 2 (mucositis control) were treated with vehicle. Rats in group 3 were treated with l-glutamine (1 g/kg, p.o.; 15 days) before and after mucositis induction. Oral mucositis was induced by busulfan (6 mg/kg, p.o.; 4 days) and the tongue exposed to infrared (IR) radiation of intensity 40 mV/cm(2) for 5 s on the 1st, 4th and 10th days of challenge using a tail flick apparatus. Parameters monitored were body weight, food intake, blood count and survival. Oral mucositis score (OMS) was recorded daily. Histological changes of the irradiated tongue were assessed by hematoxylin and eosin staining.

RESULTS

Busulfan and IR radiation significantly reduced body weight and food intake of the mucositis control group as compared to normal control. Clear ulceration of the tongue reflected in the OMS. Histopathology of the tongue revealed intense lymphocytic infiltration, decreased thickness of squamous epithelial cell layer, decrease in number of blood vessels, and necrosis of cells along with pseudo-membrane formation in the mucositis control group. These findings suggested that oral mucositis was successfully induced and treatment with l-glutamine partially reversed these conditions.

CONCLUSION

Oral mucositis was established successfully in rats by the combination of chemotherapeutic agent and IR radiation. This may be a useful model for screening drugs in the treatment of oral mucositis.

The effect of Cinnamaldehyde on mucositis and salivary antioxidant capacity in gamma-irradiated rats (a preliminary study)

Background and purpose of the study

The aim of this study was to investigate the effect of cinnamaldehyde on mucositis and salivary total antioxidant capacity in gamma-irradiated rats.

Methods

The study was conducted on 28 male Wistar rats, 7–11 weeks of age and 160 ± 20 g body weight, divided into four groups of seven rats each. The first group receiving normal saline (S), the second group receiving saline and gamma radiation (SR), the third group receiving 50 mg/kg cinnamaldehyde 98% (C), and the fourth group receiving 50 mg/kg cinnamaldehyde 98% and gamma radiation (CR). SR and CR groups were exposed to 15 Gy gamma irradiation for 7 min and 39 s. Rats were intraperitoneally injected each day during the 10-day period of the experiment, and their tongues and lips were examined to assess the incidence and severity of mucositis. The saliva samples were taken from the animals three times on day zero, six, and ten.

Results

The mean mucositis incidence appeared to be delayed in the CR than the SR group (P = 0.024), and the severity was significantly higher in the SR compared to the CR group;the difference was statistically significant on the second day (P = 0.027). In the evaluation of salivary antioxidant capacity, salivary antioxidant concentration was significantly higher in the C than the S, SR, and CR groups on the tenth day of the experiment (p <0.05).

Conclusion

The clinical effects in the CR group seem to be due to antioxidant, anti-bacterial and anti-inflammatory effects of cinnamaldehyde; this conclusion, however, requires further investigations. Delayed antioxidant effect in the CR group was evident in ip cinnamaldehyde injection, the exact mechanism is not clear.

Normal tissues toxicities triggered by combined anti-angiogenic and radiation therapies: hurdles might be ahead

BACKGROUND

Combined-modality therapy is a promising approach to improve the therapeutic index of radiotherapy. However, these improvements could come at the cost of increased toxicities. Clinical trials evaluating anti-tumour efficacy of bevacizumab combined with radiotherapy have encountered unexpected side effects. This study is the first systematic evaluation of normal tissue toxicity triggered by anti-angiogenic agents combined with radiation therapy in mice.

METHODS

Effect of a mouse anti-VEGF antibody was monitored on acute toxicity studying radiation-induced intestinal ulceration (12 Gy TBI); on subacute toxicity using a model of oral mucositis (16.5 Gy); on late radiation injuries by monitoring lung fibrosis (bleomycin and 19 Gy).

RESULTS

Combination of irradiation with anti-VEGF antibody enhanced intestinal damages with severe epithelial ulcerations, had no adverse impact on oral mucositis and dramatically worsened the fibrotic picture induced by bleomycin and irradiation to the lung.

INTERPRETATION

These reports bring to light the important questions about safety and underscore the need for appropriate preclinical modelling of the impact on normal tissues of novel drug-radiation regimens. Our findings also highlight the complexity of anti-VEGF action, which could in defined conditions exert tissue-specific protection. The findings indicate that the combination of targeted drugs with radiotherapy should be approached with caution.

Differential effect triggered by a heparan mimetic of the RGTA family preventing oral mucositis without tumor protection

PURPOSE

Oral mucositis is a common side effect induced by radio/chemotherapy in patients with head and neck cancer. Although it dramatically impairs patient quality of life, no efficient and safe therapeutic solution is available today. Therefore, we investigated the protective efficacy of a new heparan mimetic biopolymer, RGTA-OTR4131, used alone or in combination with amifostine, for oral mucositis and simultaneously evaluated its effect on tumor growth in vitro and in vivo.

METHODS AND MATERIALS

A single dose of 16.5 Gy was selectively delivered to the snout of mice, and the effects of OTR4131 or amifostine-OTR4131 were analyzed by macroscopic scoring and histology. The effect of OTR4131 administration on tumor growth was then investigated in vitro and in xenograft models using two cell lines (HEP-2 and HT-29).

RESULTS

Amifostine and OTR4131 significantly decreased the severity and duration of lip mucosal reactions. However, amifostine has to be administered before irradiation, whereas the most impressive protection was obtained when OTR4131 was injected 24 h after irradiation. In addition, OTR4131 was well tolerated, and the combination of amifostine and OTR4131 further enhanced mucosal protection. At the tumor level, OTR4131 did not modify HEP-2 cell line clonogenic survival in vitro or protect xenografted tumor cells from radiotherapy. Of interest, high doses of OTR4131 significantly decreased clonogenic survival of HT-29 cells.

CONCLUSIONS

RGTAs-OTR4131 is a well-tolerated, natural agent that effectively reduces radio-induced mucositis without affecting tumor sensitivity to irradiation. This suggests a possible transfer into the clinic for patients' benefit.

Allopurinol gel mitigates radiation-induced mucositis and dermatitis

It has not been verified whether allopurinol application is beneficial in decreasing the severity of radiation-induced oral mucositis and dermatitis. Rats were divided into 4 groups and received 15 Gy irradiation on the left whisker pad. Group 1 received only irradiation. Group 2 was maintained by applying allopurinol/carrageenan-mixed gel (allopurinol gel) continuously from 2 days before to 20 days after irradiation. Group 3 had allopurinol gel applied for 20 days after radiation. Group 4 was maintained by applying carrageenan gel continuously from 2 days before to 20 days after irradiation. The intra oral mucosal and acute skin reactions were assessed daily using mucositis and skin score systems. The escape thresholds for mechanical stimulation to the left whisker pad were measured daily. In addition, the irradiated tissues at the endpoint of this study were compared with naïve tissue. Escape threshold in group 2 was significantly higher than that in group 1, and mucositis and skin scores were much improved compared with those of group 1. Concerning escape threshold, mucositis and skin scores in group 3 began to improve 10 days after irradiation. Group 4 showed severe symptoms of mucositis and dermatitis to the same extent as that observed in group 1. In the histophathological study, the tissues of group 1 showed severe inflammatory reactions, compared with those of group 2. These results suggest that allopurinol gel application can mitigate inflammation reactions associated with radiation-induced oral mucositis and dermatitis.

Development of radiobiology for oncology-a personal view

When I came into radiotherapy in 1950, I was puzzled that some patients were treated to 3000 rads (cGy) in 3 weeks but others received 4000 in 5 or 6000 in 6 weeks. When I asked why, there were no convincing answers given, except 'this is what we usually do'. It wasn't until I went to a course on 'Radiobiology for Radiotherapy' in Cambridge that I learnt about the basic theories of Douglas Lea and the very considerable history of research into radiobiology and clinical radiotherapy. And there were still some questions outstanding, such as the relative importance of intracellular repair between 'daily' fractions, whether a 2 day gap each week was a good or a bad idea, and the role of proliferation, if any, during irradiation. I thought that a few simple animal experiments might help to give answers! That led me to a continuing interest in these questions and answers, which has taken me more than 50 years to pursue. This is the very personal story of what I saw happening in the subject, decade by decade. I was happy to experience all this together with scientists in many other countries, and our own, along the way.

Vitamin E and L-carnitine, separately or in combination, in the prevention of radiation-induced oral mucositis and myelosuppression: a controlled study in a rat model

The aim of this study was to determine the effects of vitamin E (VE) and L-carnitine (LC) supplementation, separately or in combination, on radiation-induced oral mucositis and myelosuppression. Group 1 received no treatment (control). Group 2 received 15 Gray of 60Co gamma irradiation as a single dose to total cranium (IR). Group 3, 4, and 5 received irradiation plus 40 mg/kg/day VE (IR+VE) or 200 mg/kg/day LC (IR+LC) or in combination (IR+VE+LC) respectively. Clinically and histopathologically, assessments of mucosal reactions were performed by two independent experts in Radiation Oncology and Pathology, respectively. Hematologic analyses and antioxidant enzyme evaluations were also performed. Irradiation significantly increased oral mucositis, and decreased thrombocyte and White Blood Cell counts. A significant increase in malondialdehyde (MDA) levels and decrease in superoxide dismutase (SOD) and catalase (CAT) activities in plasma were found in the IR group. VE and LC administration, separately, plus irradiation significantly delayed the starting day, and reduced the severity of, oral mucositis. This administration also reduced a fall in the numbers of thrombocyte and WBC caused by irradiation, and decreased the MDA level, and increased the activity of SOD and CAT enzymes in the plasma. VE and LC, in combination, plus irradiation did not provide a superior radioprotection against radiation-induced toxicities.

Amifostine (ETHYOL) protects rats from mucositis resulting from fractionated or hyperfractionated radiation exposure

PURPOSE

The cytoprotective drug amifostine (Ethyol) protects rats from oral mucositis resulting from a single dose of gamma-irradiation. We expanded earlier studies to determine whether multiple doses of amifostine protect against fractionated or hyperfractionated radiation and whether the active metabolite of amifostine (WR-1065) accumulates in tissues upon repeated administration.

METHODS AND MATERIALS

Rats received amifostine daily for 5 days in conjunction with a 1-week fractionated radiation schedule and were evaluated for oral mucositis. Rats also received amifostine before the am or pm exposure or b.i.d. in conjunction with hyperfractionated radiation. To determine the pharmacokinetics of WR-1065 after repeated dosing, amifostine was given 5 days a week for 1 or 3 weeks, and rat tissue and plasma were collected at intervals during and after treatment and analyzed for WR-1065.

RESULTS

Amifostine protected rats from mucositis resulting from fractionated or hyperfractionated radiation. When the number of days of amifostine administration was reduced, protection was diminished. A dose of 100 mg/kg given in the morning or 2 doses at 50 mg/kg provided the best protection against hyperfractionated radiation. WR-1065 did not accumulate in tissues or tumor upon repeated administration.

CONCLUSIONS

Amifostine prevented radiation-induced mucositis in a rat model; protection was dose and schedule dependent.

Porphyrin-Mediated Boron Neutron Capture Therapy: A Preclinical Evaluation of the Response of the Oral Mucosa

Preclinical studies are in progress to determine the potential of boron neutron capture therapy (BNCT) for the treatment of carcinomas of the head and neck. Recently, it has been demonstrated that various boronated porphyrins can target a variety of tumor types. Of the porphyrins evaluated so far, copper tetracarboranylphenyl porphyrin (CuTCPH) is potentially a strong candidate for clinical use. In the present investigation, the response of the oral mucosa to CuTCPH-mediated boron neutron capture (BNC) irradiation was assessed using the ventral surface of the tongue of adult male Fischer 344 rats, a standard rodent model. CuTCPH was administered by intravenous infusion, at a dose of 200 mg/kg body weight, over a 48-h period. Three days after the end of the administration of CuTCPH, biodistribution studies indicated very low levels of boron (<2 microg/g) in the blood. Levels of boron in tongue tissue were 39.0 +/- 3.8 microg/g at this time. This was the time selected for irradiation with single doses of thermal neutrons from the Brookhaven Medical Research Reactor. The estimated level of boron-10 in the oral mucosa was used in the calculation of the physical radiation doses from the 10B(n,alpha)7Li reaction. This differs from the approach using the present generation of clinical boron carriers, where boron levels in blood at the time of irradiation are used for this calculation. Dose-response curves for the incidence of mucosal ulceration were fitted using probit analysis, and the doses required to produce a 50% incidence of the effect (ED50 +/- SE) were calculated. Analysis of the dose-effect data for CuTCPH-mediated BNC irradiation, compared with those for X rays and thermal neutrons alone, gave a compound biological effectiveness (CBE) factor of approximately 0.04. This very low CBE factor would suggest that there was relatively low accumulation of boron in the key target epithelial stem cells of the oral mucosa. As a consequence, with low levels of boron (<2 microg/g) in the blood, the response of the oral mucosa to CuTCPH-mediated BNCT will be governed primarily by the radiation effects of the thermal neutron beam and not from the boron neutron capture reaction [10B(n,alpha)7Li].

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.

Effects of dose and schedule on the efficacy of Ethyol: preclinical studies1 1The authors are employees and shareholders of MedImmune Inc

The chemo- and radioprotectant drug amifostine (Ethyol; MedImmune, Inc, Gaithersburg, MD) is approved for intravenous (IV) administration; however, the subcutaneous (SC) route is being explored as a practical alternative. We have previously reported equivalence between IV and SC administration using a rat model of radioprotection and active metabolite (WR-1065) tissue pharmacokinetics. To examine the more clinically relevant fractionated and hyperfractionated radiation schedules and the effects of variations in the time of amifostine administration, we expanded these studies to include radioprotection and pharmacokinetic studies of WR-1065 using multiple dosing. To measure radioprotection using a fractionated radioprotection model, rats were given amifostine over a 1-week period at various doses (25 mg/kg, 50 mg/kg, 100 mg/kg; or 162.5 mg/m(2), 325 mg/m(2), 650 mg/m(2), respectively) IV or SC daily 30 minutes before exposure to 7.5 Gy/dose. Rats were fully protected from mucositis at the highest amifostine dose, with protection diminishing as the amifostine was decreased. Equivalent protection was observed whether the drug was given IV or SC. When the number of days of amifostine administration was reduced, protection was diminished. Amifostine also protected against radiation delivered using a 1-week hyperfractionated schedule (4.5 Gy/exposure twice daily), with optimal protection occurring when the drug was administered bid 30 minutes before each exposure (50 mg/kg) or every day before the morning exposure (100 mg/kg). The need for daily dosing to achieve optimal radioprotection was consistent with the tissue pharmacokinetics of the active metabolite. We found that WR-1065 did not accumulate in tissues or in SC-implanted tumors when amifostine was administered daily for 3 weeks. In addition, tissue and tumor levels of WR-1065 declined to baseline 24 hours after each amifostine dose. In a monkey pharmacokinetic model, plasma levels of WR-1065 (characterized by a pronounced spike of WR-1065 immediately after IV administration that was absent when the drug was given SC) were similar to those of humans; however, levels of WR-1065 in the tissues were higher 30 minutes following SC administration and were equivalent 60 minutes following IV or SC administration. These results suggest that maximum tissue levels and protection occur when amifostine is given 30 to 60 minutes before radiation exposure, that treatment breaks reduce the radioprotection by amifostine, and that protection from hyperfractionated radiation is dependent on amifostine dose and schedule.

Subcutaneous administration of amifostine (ethyol) is equivalent to intravenous administration in a rat mucositis model

PURPOSE

Amifostine (Ethyol) is currently approved for intravenous (IV) administration to prevent xerostomia in patients receiving radiotherapy for head-and-neck cancer. Recently, subcutaneous (SC) administration has been explored as an alternative route. To determine whether SC administration was equivalent to IV administration, we used models to follow pharmacokinetics and oral mucosal protection in rats.

METHODS

Amifostine was administered to rats at doses of 200, 100, or 50 mg/kg (1300, 650, or 325 mg/m(2)) IV or SC at various times before radiation at 15.3 Gy (protection studies) or harvest of blood and tissues for analysis by HPLC (pharmacokinetic studies).

RESULTS

Amifostine administered IV or SC 1 h before radiation protected rats from mucositis, but the protective effect was more prolonged when amifostine was administered SC. Tissue levels of the active metabolite (WR-1065) were equivalent after SC administration. The correlation between tissue levels of WR-1065 and protection was strong, but that between blood levels of WR-1065 and protection was only weak.

CONCLUSION

These data demonstrate that, in a rat model, SC administration of amifostine was at least as effective as that by IV.

n-3 polyunsaturated fatty acids decrease mucosal/epidermal reactions and enhance antitumour effect of ionising radiation with inhibition of tumour angiogenesis

The purpose of this study was to evaluate the effect of n-3 polyunsaturated fatty acids (n-3 PUFAs) on normal tissue (lip mucosa) and tumour growth when combined with ionising radiation. The oral region (snout) of C57 black mice was irradiated with 16.5 Gy and n-3 PUFAs (100 microl) were injected intravenously for 2 weeks. After exposure to irradiation, the degree and duration of the acute reactions decreased significantly when mice were treated with n-3 PUFAs as compared to the control group. Interestingly, the range of the reactions in the n-3 PUFAs-treated group compared favourably to the group receiving amifostine (27.5 mg/kg i.v.). the effect of n-3 PUFAs was further evaluated in HEP-2 human carcinoma xenograft transplanted in nude mice. An inhibition of tumour growth was observed when mice were treated with n-3 PUFAs alone and this effect was maximal when combined with irradiation. Similar results were obtained using eicosapentaenoic acid. The effect of n-3 PUFAs was associated with inhibition of angiogenesis and tumour proliferation, and significantly decreased expression of cyclooxygenase-2. In conclusion, n-3 PUFAs administration decrease mucosal response, while moderately enhancing the antitumour effect of irradiation. The magnitude of the differential effect suggests that n-3 PUFAs need to be further investigated in the clinic.

Preclinical modeling of improved amifostine (Ethyol) use in radiation therapy

Amifostine (Ethyol) has been evaluated clinically as a radioprotective agent for the prevention of xerostomia and mucositis for patients receiving radiotherapy (RT). Currently, amifostine is approved for the prevention of xerostomia in head and neck cancer patients receiving RT when administered intravenously (IV) before RT. For the clinician, there would be several advantages to administering the drug subcutaneously and to being able to show its protective effects on mucositis. The authors have developed a rat RT model to examine the protective effects of amifostine after IV and subcutaneous (SC) administration in a mucositis model. Rats (5 per group) were given 200 mg/kg (human dose equivalent of approximately 1,300 mg/m(2)) of amifostine either IV or SC, and their head and neck regions were exposed to 15.3 Gy of gamma radiation 0.5, 2, 4, and 8 hours after amifostine administration. For 10 days after treatment, the oral cavities of the rats were examined for signs of mucositis. Mucosal erythema and mucosal edema were scored according to 0 through 5 and 0 through 2 scales, respectively, with the scores added to indicate overall mucositis. The average mucositis score for the untreated animals was 3.5. Rats were protected from mucositis up to 4 hours when given amifostine either IV or SC. Rats that received amifostine SC, but not IV, were protected from mucositis 8 hours after administration. Preliminary pharmacokinetic data have revealed slightly higher active metabolite (WR-1065) levels in the parotid gland and small intestine in the rats given amifostine SC compared with IV and equivalent levels in the plasma and kidney. The data showed that SC administration of amifostine gave radioprotection comparable to IV administration up to 4 hours before RT and may be more effective than IV administration at longer pretreatment intervals.

Boron neutron capture therapy: effects of split dose and overall treatment time

New clinical protocols are being developed that will entail the administration of considerably higher doses of the boron delivery agent boronophenylalanine (BPA) than those in current clinical use. Fractionation (2 or 4 fractions) of BPA mediated boron neutron capture therapy (BNCT) is also under consideration at some clinical centres. Given the considerably higher infusion volumes that will be entailed in the delivery of BPA in the new high dosage protocols, there will be a requirement to extend the gap between fractions to 2 or more days. In order to assess the effects of a 2 fraction protocol on the therapeutic efficacy of BPA mediated BNCT, a series of split dose irradiations (two equal fractions) were undertaken using the rat intracranially implanted 9L gliosarcoma model. A single dose exposure to BPA mediated BNCT of 3.0 Gy resulted in long term survival levels of 50%. Survival levels increased to 71% and 77% with a 3 and 5 day gap between dose fractions (two equal fractions), respectively, using the same total dose. A further increase in the time interval between dose fractions to 7 days resulted in a reduction in survival to 36%. However, there was no significant difference between the single dose and the 3, 5 and 7 day survival data (P > 0.1) The difference between the 5 and 7 day split dose survival data was of border-line significance (P = 0.05). It is anticipated that mucositis, could become a potential problem in future BNCT clinical protocols involving higher doses, larger field sizes or multiple fields. The potential sparing of the oral mucosa, due to repopulation during the interval between the two fractions, was investigated using a series of split dose BPA mediated BNC irradiations. The ventral surface of the rat tongue was utilised as a model for oral mucosa. The ED50 (50% incidence) values for the ulceration end point were 3.0+/-0.1, 3.2+/-0.1, 3.0+/-0.1 and 3.6+/-0.1 Gy, for 3, 5, 7 and 9 day splits between doses, respectively. It is evident from this data that there were no significant changes in the ED50 (p < 0.001) until the 9 day dose split, when the ED50 value was 20% higher than the ED50 value after a 7 day split. It was concluded that the two fraction BNCT protocol, with dose splits of up to 5 days, did not diminish the therapeutic response of the rat 9L gliosarcoma, when compared with a single dose BNCT protocol. Tolerance of the oral mucosa to BNC irradiation was not increased until there was a 9 day gap between fractions. However, the beneficial effects of dose sparing at this time interval between doses, would probably be counteracted by a reduction in the therapeutic effectiveness of the BNCT modality, due to repopulation of tumour clonogens between doses.

Boron microlocalization in oral mucosal tissue: implications for boron neutron capture therapy

Clinical studies of the treatment of glioma and cutaneous melanoma using boron neutron capture therapy (BNCT) are currently taking place in the USA, Europe and Japan. New BNCT clinical facilities are under construction in Finland, Sweden, England and California. The observation of transient acute effects in the oral mucosa of a number of glioma patients involved in the American clinical trials, suggests that radiation damage of the oral mucosa could be a potential complication in future BNCT clinical protocols, involving higher doses and larger irradiation field sizes. The present investigation is the first to use a high resolution surface analytical technique to relate the microdistribution of boron-10 (10B) in the oral mucosa to the biological effectiveness of the 10B(n,alpha)7Li neutron capture reaction in this tissue. The two boron delivery agents used clinically in Europe/Japan and the USA, borocaptate sodium (BSH) and p-boronophenylalanine (BPA), respectively, were evaluated using a rat ventral tongue model. 10B concentrations in various regions of the tongue mucosa were estimated using ion microscopy. In the epithelium, levels of 10B were appreciably lower after the administration of BSH than was the case after BPA. The epithelium:blood 10B partition ratios were 0.2:1 and 1:1 for BSH and BPA respectively. The 10B content of the lamina propria was higher than that measured in the epithelium for both BSH and BPA. The difference was most marked for BSH, where 10B levels were a factor of six higher in the lamina propria than in the epithelium. The concentration of 10B was also measured in blood vessel walls where relatively low levels of accumulation of BSH, as compared with BPA, was demonstrated in blood vessel endothelial cells and muscle. Vessel wall:blood 10B partition ratios were 0.3:1 and 0.9:1 for BSH and BPA respectively. Evaluation of tongue mucosal response (ulceration) to BNC irradiation indicated a considerably reduced radiation sensitivity using BSH as the boron delivery agent relative to BPA. The compound biological effectiveness (CBE) factor for BSH was estimated at 0.29 +/- 0.02. This compares with a previously published CBE factor for BPA of 4.87 +/- 0.16. It was concluded that variations in the microdistribution profile of 10B, using the two boron delivery agents, had a significant effect on the response of oral mucosa to BNC irradiation. From a clinical perspective, based on the findings of the present study, it is probable that potential radiation-induced oral mucositis will be restricted to BNCT protocols involving BPA. However, a thorough high resolution analysis of 10B microdistribution in human oral mucosal tissue, using a technique such as ion microscopy, is a prerequisite for the use of experimentally derived CBE factors in clinical BNCT.

A quantitative histometric murine in vivo model of radiation-induced oral mucositis

Gastrointestinal toxicity is a limiting factor in the effectiveness of cancer therapy. This toxicity is most visible in the mouth. There is considerable interest in developing strategies involving growth-factor manipulation of the epithelial stem cells to afford protection to these cells during treatment and/or to speed up the regenerative process following treatment. In order for this to be achieved, studies have to be undertaken in animal systems to demonstrate the proof of principle and determine optimal protocols. Here, a murine model for oral mucositis based on measurements of tissue cellularity at various times after exposure to radiation was used to investigate cytotoxicity. Several sites in the mouth were analysed and the pronounced circadian rhythm in these various epithelial sites determined. The circadian rhythm is important in that it would determine the timing of administration of growth factors. A microscope with an interactive computer was used to define areas of epithelium and lengths of basal layer, within which, and along which, the total number of cell nuclei was determined over a range of times following exposure to 10, 20 and 30 Gy of X-rays. For various practical reasons, the ventral surface of the tongue was identified as the most appropriate tissue to analyse. Here, measurements of cellularity reached minimum values between 6 and 8 days following 20 Gy. Labelling of S-phase cells demonstrated foci of regeneration and a burst of proliferative regeneration that commenced at about 5 days and reached peak values at 8 days after irradiation. This burst of regenerative proliferation was coincident with the minimum in tissue cellularity on about day 8. The lower dose of radiation (10 Gy) had minimal effects on cellularity: after the higher dose (30 Gy), there was clearly a more severe level of cellular depletion. This quantitative model of oral mucositis could be used to study the effects of other cytotoxics, including combinations of agents, and the potential role of growth factors to reduce the severity of the cellular depletion and to speed up the kinetics of regeneration.

The importance of schedule and drug dose intensity in combinations of modalities

PURPOSE

To review a series of laboratory experiments that have been conducted to investigate the degree to which therapeutic effectiveness is a function of the scheduling of two or more therapeutic agents.

METHODS AND MATERIALS

The therapeutic effectiveness of a few combinations of modalities (fractionated irradiation + cis-DDP alone and with 5FU, cyclophosphamide, or etoposide) has been evaluated systematically for a large number of schedules. For every such schedule, therapeutic gain factors were calculated as the ratio of effectiveness for tumor growth inhibition to each of three normal tissue endpoints in laboratory mice: duodenal crypt cell survival, pneumonitis (breathing rate at 5 months after treatment), and pulmonary fibrosis (breathing rate at 10 months).

RESULTS

For every combination tested, at least one schedule was distinctly therapeutically superior to the others. Most often, the greatest therapeutic gain was achieved with divided doses of cis-DDP administered simultaneously with five daily x-ray dose fractions. Even greater gain was found when cyclophosphamide was administered as a single bolus 1 day before fractionated cis-DDP/irradiation. Still greater therapeutic gain was achieved by protecting against normal tissue toxicity by administering the cytokine, interleukin 1, prior to chemotherapy-radiotherapy.

CONCLUSION

Performing experiments of the type described in this paper can be of great value in the optimization of treatment with combinations of agents or modalities.

Interleukin-1 modulatory effect on the action of chemotherapeutic drugs and localized irradiation of the lip, duodenum, and tumor

PURPOSE

This study was conducted to examine the radioprotective and radiochemoprotective capabilities of interleukin 1 beta (IL-1) on two acute-reacting normal tissues of the C3H mouse, the mucosa of the lip and the duodenum. Also assessed was the modulating effect of IL-1 on tumor growth in the same strain of mice.

METHODS AND MATERIALS

IL-1 was administered to C3H/Km mice in combination with fractionated irradiation, or with cyclophosphamide, cisplatin, or 5-fluorouracil (5FU) followed by irradiation. Normal tissue damage was evaluated in the mouse lip, using a subjective scoring system for tissue reaction, and in the duodenum, using the crypt cell survival assay. RIF-1 fibrosarcoma tumor response was assayed with the regrowth delay method.

RESULTS

IL-1 protected against the acute reaction produced by fractionated irradiation in the lip mucosa, shifting the dose-response curve by 3.8 Gy. IL-1 was protective when injected intraperitoneally 24 hr before CY or c-DDP, which were given immediately before the first of five daily radiation dose fractions. The dose-response curves for cyclophosphamide and cisplatin were shifted 4.0 Gy and 1.6 Gy, respectively. IL-1 did not protect against 5FU toxicity when treatments were administered in that same sequence; however, when 5FU was given 4 or 8 hr before IL-1 and the first radiation dose fraction followed 20 or 16 hr later, there was significant protection and the curves were separated by 1.5 Gy or 3.5 Gy. IL-1 also protected duodenal crypt cells against the cytocidal effect of fractionated irradiation, with a dose difference of 1.5 Gy and an improvement of crypt survival of 11.7%. It was even more protective for these cells against the enhanced drug toxicity when cyclophosphamide or 5FU were administered immediately before the first of five daily radiation doses, with the dose differences of 4.4 and 5.3 Gy, respectively, and improvements of crypt survival of 33.8 and 29.9%, respectively. There was no modification by IL-1 of the effect of irradiation alone on the RIF-1 tumor.

CONCLUSION

This study demonstrates the potential for use of IL-1 as an auxiliary in combinations with chemotherapeutic agents and radiation. It also indicates that for some drugs, such as 5FU, IL-1 effects may be sequence dependent.

Response of mouse tongue epithelium to single doses of bleomycin and radiation

Both bleomycin (BLM) and local X-irradiation (25 kV) induce denudation in the tongue epithelium of the C3H-Neuherberg mouse in a dose-dependent manner. In the present study the effect of BLM alone and of combined single doses of drug and radiation were studied using the incidence of epithelial denudation as the end-point. In 'time-line' experiments, 8 mg/kg BLM were given before or after graded doses of X-rays. BLM treatment required a reduction of the radiation dose (ED50) from 15 Gy to 5-7 Gy, independent of sequence or time interval. In contrast, the time course of the response was clearly dependent on the treatment interval. Latency decreased when the drug was injected less than 2 h before irradiation with minimum latency observed at 30 min. Isobologram analysis of experiments with varying combinations of X-rays and BLM demonstrated that small drug doses were relatively more effective than larger doses, suggesting an upward concavity of the BLM dose-effect curve in vivo, i.e. a 'negative shoulder' of the curve in the low dose region. In contrast to the response to X-rays alone, which has a constant latent time to ulcer of 10 days, the latency in combined treatment was clearly shortened with increasing drug dose and at high doses eventually approximated the epithelial turnover time of 5 days. The data suggest that BLM both as a single agent and in combination with X-rays reduced the probability of abortive divisions and through this effect shortened the latent time to epithelial denudation.

Radiation response of mouse lip mucosal epithelium: a cell kinetic study

Changes in the cell proliferation kinetics of the epithelium of mouse lip mucosa have been assessed after local irradiation with a single dose of 18 Gy of 60Co gamma-rays. By the fifth day after irradiation, two distinct sub-populations of epithelial cells could be discerned. The larger of the two populations consisted of cells exhibiting varying degrees of radiation-induced damage, and the smaller population was composed of cells of normal size and appearance, intermingled between the radiation-damaged cells. There was a progressive decline in the epithelial cell density with time after irradiation, and focal denudation was seen after 11 days. Cell colonies were evident in the remnants of the epithelium by day 7. Degenerate cells could be identified in the basal layer of the mucosal epithelium, both before and after irradiation. The proportion of degenerate cells was increased 5 days after irradiation with the maximum number, approximately 3.6% being counted on days 7 and 8. In the first 2 days after irradiation, there was a reduction in the labelling index (LI) of basal cells in the epithelium. This was followed by recovery to control values on day 3. The LIs of both the radiation-damaged cells and those with a normal appearance remained relatively constant between days 5 and 11, at approximately 10 and approximately 60%, respectively. The LI of basal cells in the cell colonies was very high (approximately 70%). The estimated turnover time (TT) for the basal cell population with a normal appearance and for those in cell colonies (groups of normal cells with a cord length > or = 10 cells), was extremely short < 1 day. There was some fluctuation in TT values for basal cells exhibiting radiation-induced damage, with the shortest value (approximately 3 days) at 7 and 8 days after irradiation. It was concluded from the cell kinetic data that repopulation of the lip mucosal epithelium started between 3 and 5 days after irradiation and the overall response of the mucosa to irradiation was consistent with that predicted by a hierarchical model of cell proliferative organization.

Capacity and kinetics of SLD repair in mouse tongue epithelium

The effect of dose fractionation on the radiation response of mouse tongue epithelium was quantified in fractionation protocols involving 1, 3, 4, 5 and 10 fractions, separated by at least 4 h. Fractionated irradiation was given either to the whole snout by 300 kV X-rays or locally to the tongue using 25 kV X-rays. Each protocol was terminated by a final local top-up dose (25 kV X-rays) of 5 Gy. The frequency of complete local denudation within the test area was used as the quantal end point. The kinetics of repair of sublethal damage was studied by snout irradiation with four equally spaced fractions, delivered at intervals of 35, 60, 90, 480 or 540 min, again followed by a local top-up dose of 5 Gy. The linear-quadratic model gave a satisfactory fit to the data with the exception of the four fraction/30-h data, suggesting cell cycle effects in this schedule. Analysis of the results with different two-step methods and with direct analysis yielded similar results. The alpha/beta ratio was determined to be approximately 11 GY (direct analysis: 11.6 Gy with 95% confidence limits of 8.1 and 16.4 Gy) and T1/2 was found to be 46 min (35-69 min). Both these values are in the range described for other acutely responding rodent tissues.

The tolerance of primate spinal cord to re-irradiation

PURPOSE

This study was designed to assess the tolerance of the cervical spinal cord of rhesus monkeys to re-irradiation. This information is essential for treatment recommendations in previously irradiated patients.

METHODS AND MATERIALS

Control animals received a single course of treatment to total doses of 70.4 Gy, 77.0 Gy, or 83.6 Gy in daily fractions of 2.2 Gy. Twelve asymptomatic animals that received 70.4 Gy were re-irradiated two years later to cumulative doses of 83.6, 92.4, or 101.2 Gy. Another group of 15 animals received 44 Gy and two years later were re-irradiated to cumulative doses of 83.6, 92.4, 101.2, or 110 Gy. The clinical endpoint was myeloparesis. A complete necropsy was performed in all animals when myeloparesis manifested or at the end of observation period.

RESULTS

Only two of the 12 asymptomatic animals of the 70.4 Gy dose-response study group and two of the 15 animals that had received 44 Gy initially developed myelopathy within two years of re-irradiation. The ED50 value of the single-course irradiation was 76.1 +/- 1.9 Gy, while the extrapolated ED50 for retreatment after 44 Gy was > or = 110 Gy. The lesions of the two symptomatic animals that received 70.4 Gy initially were mixtures of white matter and vascular lesions similar to those observed after single course irradiation. However, both symptomatic animals given 44 Gy initially had hemorrhagic infarcts in the white matter.

CONCLUSION

The results of this study indicate that substantial recovery of occult injuries induced by the initial 44 Gy had occurred within two years. The difference between the types of lesions observed after a single course and re-irradiation suggests that vascular injury may recover less efficiently or at slower rate than white matter damage. The dependence of the extent of recovery on the initial dose and the time course of such recovery in primates are being investigated.