Botulinum Toxin Confers Radioprotection in Murine Salivary Glands

Discovery of Glutamate Carboxypeptidase III Ligands to Compete the Uptake of [177Lu]Lu-PSMA-617 in Healthy Organs

Prostate-specific membrane antigen (PSMA)-targeted radio ligand therapeutics (RLTs), such as [177Lu]Lu-PSMA-617 (Pluvicto), have been shown to accumulate in salivary glands and kidneys, potentially leading to undesired side effects. As unwanted accumulation in normal organs may derive from the cross-reactivity of PSMA ligands to glutamate carboxypeptidase III (GCPIII), it may be convenient to block this interaction with GCPIII-selective ligands. Parallel screening of a DNA-encoded chemical library (DEL) against GCPIII and PSMA allowed the identification of GCPIII binders. Structure-activity relationship (SAR) studies resulted in the identification of nanomolar GCPIII ligands with up to 1000-fold selectivity over PSMA. We studied the ability of GCPIII ligands to counteract the binding of [177Lu]Lu-PSMA-617 to human salivary glands by autoradiography and could demonstrate a partial radioprotection.

Metabolomics analysis of pathways underlying radiation-induced salivary gland dysfunction stages

Salivary gland hypofunction is an adverse side effect associated with radiotherapy for head and neck cancer patients. This study delineated metabolic changes at acute, intermediate, and chronic radiation damage response stages in mouse salivary glands following a single 5 Gy dose. Ultra-high performance liquid chromatography-mass spectrometry was performed on parotid salivary gland tissue collected at 3, 14, and 30 days following radiation (IR). Pathway enrichment analysis, network analysis based on metabolite structural similarity, and network analysis based on metabolite abundance correlations were used to incorporate both metabolite levels and structural annotation. The greatest number of enriched pathways are observed at 3 days and the lowest at 30 days following radiation. Amino acid metabolism pathways, glutathione metabolism, and central carbon metabolism in cancer are enriched at all radiation time points across different analytical methods. This study suggests that glutathione and central carbon metabolism in cancer may be important pathways in the unresolved effect of radiation treatment.

Botox for the prevention of radiation-induced Sialadenitis and xerostomia in head and neck cancer patients: A pilot study

BACKGROUND

To determine the safety of Botox and its potential effect on alleviating radiation therapy (RT)-induced sialadenitis in head and neck cancer patients.

METHODS

Twenty patients with stage III/IV head and neck cancer were randomized to receive Botox or saline injections into both submandibular glands (SMG). There were three visits: one before RT (V1); 1 week after RT (V2); and 6 weeks after RT (V3), each of which included saliva collection, a 24-h dietary recall, and a quality-of-life survey.

RESULTS

No adverse events were observed. While the control group was much older, the Botox group more commonly underwent induction chemotherapy compared with controls. From V1 to V2, salivary flow decreased in both groups, but only in the control group from V1 to V3. CXCL-1 (GRO), a neutrophil chemoattractant, was lower in the Botox group compared with the control group at V3.

CONCLUSION

Botox can be safely administered to the salivary glands prior to external beam radiation without observed complications or side-effects. After an initial reduction in salivary flow following RT, the Botox group showed lack of further flow reduction compared with controls. The inflammatory marker CXCL 1, which was reduced in the in Botox group at V3, may be a candidate for further studies of radiation-induced sialadenitis.

Current management of xerostomia in head and neck cancer patients

Radiotherapy (RT) continues to play a key role in the management of head and neck cancer (HNC). Xerostomia remains a principal detriment to the quality of life (QoL) for 80 % of surviving patients receiving head and neck radiation. Radiation-induced injury to the salivary glands is dose-dependent, and thus efforts have been focused on decreasing radiation to the salivary glands. Decreased saliva production reduces both short-term and long-term quality of life in head and neck survivors by impacting on taste and contributing to dysphagia. Several radioprotective agents to the salivary gland have been investigated. Although not widely practiced, surgical transfer of the submandibular gland prior to RT is the mainstay of surgical options in preventing xerostomia. This review focuses on the strategies to improve xerostomia following radiation therapy in head and neck cancers.

Diagnosis, Prevention, and Treatment of Radiotherapy-Induced Xerostomia: A Review

In patients with head and neck cancer, irradiation (IR)-sensitive salivary gland (SG) tissue is highly prone to damage during radiotherapy (RT). This leads to SG hypofunction and xerostomia. Xerostomia is defined as the subjective complaint of dry mouth, which can cause other symptoms and adversely affect the quality of life. In recent years, diagnostic techniques have constantly improved with the emergence of more reliable and valid questionnaires as well as more accurate equipment for saliva flow rate measurement and imaging methods. Preventive measures such as the antioxidant MitoTEMPO, botulinum toxin (BoNT), and growth factors have been successfully applied in animal experiments, resulting in positive outcomes. Interventions, such as the new delivery methods of pilocarpine, edible saliva substitutes, acupuncture and electrical stimulation, gene transfer, and stem cell transplantation, have shown potential to alleviate or restore xerostomia in patients. The review summarizes the existing and new diagnostic methods for xerostomia, along with current and potential strategies for reducing IR-induced damage to SG function. We also aim to provide guidance on the advantages and disadvantages of the diagnostic methods. Additionally, most prevention and treatment methods remain in the stage of animal experiments, suggesting a need for further clinical research, among which we believe that antioxidants, gene transfer, and stem cell transplantation have broad prospects.

Characterization of Transgenic NSG-SGM3 Mouse Model of Precision Radiation-Induced Chronic Hyposalivation

Regenerative medicine holds promise to cure radiation-induced salivary hypofunction, a chronic side effect in patients with head and neck cancers, therefore reliable preclinical models for salivary regenerative outcome will promote progress towards therapies. In this study, our objective was to develop a cone beam computed tomography-guided precision ionizing radiation-induced preclinical model of chronic hyposalivation using immunodeficient NSG-SGM3 mice. Using a Schirmer's test based sialagogue-stimulated saliva flow kinetic measurement method, we demonstrated significant differences in hyposalivation specific to age, sex, precision-radiation dose over a chronic (6 months) timeline. NSG-SMG3 mice tolerated doses from 2.5 Gy up to 7.5 Gy. Interestingly, 5-7.5 Gy had similar effects on stimulated-saliva flow (∼50% reduction in young female at 6 months after precision irradiation over sham-treated controls), however, >5 Gy led to chronic alopecia. Different groups demonstrated characteristic saliva fluctuations early on, but after 5 months all groups nearly stabilized stimulated-saliva flow with low-inter-mouse variation within each group. Further characterization revealed precision-radiation-induced glandular shrinkage, hypocellularization, gland-specific loss of functional acinar and glandular cells in all major salivary glands replicating features of human salivary hypofunction. This model will aid investigation of human cell-based salivary regenerative therapies.

MicroRNA-mRNA expression profiles and functional network after injection of botulinum toxin type A into submandibular glands

Botulinum toxin type A (BTXA) is effective for the treatment of sialorrhea. MicroRNAs (miRNAs) have significant functions in salivary diseases, but the role of miRNAs during BTXA-inhibited salivary secretion is not yet clear. A total of 19 differentially expressed (DE) miRNAs and 1072 DE mRNAs were identified following BTXA injected into submandibular glands of rats (n = 4) through miRNA sequencing and microarray analysis. Bioinformatic analysis identified that several pathways may be associated with the inhibition of salivary secretion, such as the MAPK signalling pathway, tight junctions, and cytokine-cytokine receptor interaction. We predicted the target genes of DE miRNAs and established the miRNA-mRNA interaction network. The intersection of DE mRNAs and target genes of DE miRNAs was performed and seven mRNAs were obtained: Egr2, Paqr9, Zkscan1, Usp6n, Cyb561a3, Zfhx4, and Clic5. These findings explore the mechanism of BTXA in inhibiting salivary secretion and probably will provide new ideas for clinical application.

Effect of ischemic preconditioning on radiation damage to the submandibular gland in rats

To investigate the effects of radiation on rat submandibular glands and the possible protective effects of ischemic preconditioning, the submandibular glands of Wistar rats were subjected to in situ radiation after ischemic preconditioning. The glands were exposed to X-radiation at a single dose of 20 Gy. Ischemic preconditioning was achieved by three min of ischemia and three min of reperfusion, repeated three times before irradiation. Salivary secretion, histological changes, alterations in tight junctions, and the levels of oxidative stress, pro-inflammatory cytokines, and water secretion proteins mediated by the muscarinic acetylcholine M3 subtype receptor were determined at 1 and 12 weeks post-irradiation. In glands subjected to irradiation only, the secretion, superoxide dismutase activity, tight junction width, acinar cell number, and M3 receptor and aquaporin-5 levels were lower at 1 and 12 weeks than seen in the ischemically preconditioned irradiated glands. In contrast, tumor necrosis factor-α, malondialdehyde, myeloperoxidase activity, and the expression of the tight junction protein claudin-4 were significantly higher in the irradiated only glands. Our study revealed that radiation caused a series of injury-stress responses, especially damage to the water secretion pathway mediated by the M3 receptor that ultimately led to hyposecretion, which might play an important role in the dysfunction of the irradiated only glands. Ischemic preconditioning reduced the radiation-induced injury to submandibular glands and ameliorated salivary hyposecretion.

Advances on mechanism and treatment of salivary gland in radiation injury

Oral squamous cell carcinoma (OSCC) is the most frequent tumour in head and neck malignant. The current treatment is mainly based on surgery therapy, radiation therapy and chemical therapy. Meanwhile, there are many a defect in the treatment. For example, there are many defects in radiotherapy. Radioactive salivatitis is the most common. In addition, there are a series of changes such as dry mouth, oral mucositis, rampant dental caries, and radioactive osteomyelitis of jaw, which cause swallowing, chewing problems, and taste dysfunction. Currently, the research on radioactive salivatitis is progressing rapidly, but its mechanism is more complication. This paper review aims to summarize the research progress in this field.

Experimental Animal Model Systems for Understanding Salivary Secretory Disorders

Salivary secretory disorders are life-disrupting pathologic conditions with a high prevalence, especially in the geriatric population. Both patients and clinicians frequently feel helpless and get frustrated by the currently available therapeutic strategies, which consist mainly of palliative managements. Accordingly, to unravel the underlying mechanisms and to develop effective and curative strategies, several animal models have been developed and introduced. Experimental findings from these models have contributed to answer biological and biomedical questions. This review aims to provide various methodological considerations used for the examination of pathological fundamentals in salivary disorders using animal models and to summarize the obtained findings. The information provided in this review could provide plausible solutions for overcoming salivary disorders and also suggest purpose-specific experimental animal systems.

Salivary side effects after radioiodine treatment for differentiated papillary thyroid carcinoma: Long-term study

BACKGROUND

Although many studies focus on short-term side effects of radioiodine therapy, almost none studied long-term side effects. We assessed radioiodine long-term salivary side effects after radioiodine treatment for differentiated papillary thyroid carcinoma and compared it to short-term morbidity within the same population.

METHODS

A standardized self-administrated questionnaire was submitted in 2019 by patients treated with radioiodine between January 2011 and December 2012. These patients had already answered the same questionnaire 6 years before.

RESULTS

Our study showed a significant reduction for salivary side effects: discomfort in submandibular or parotid area, swelling, pain, a bad or salty taste in the mouth, allowing to get back to a "normal" diet.

CONCLUSIONS

Our study suggests that a significant rate of patients will recover from I¹³¹ therapy salivary side effects. As almost 30% of these remissions happened during our late stage follow-up, we highlight the necessity of a long-term follow-up in these patients.

Radiosensitivity: Gender and Order of Administration of G-CSF, An Experimental Study in Mice

To elucidate the potential influence of stimulating bone marrow before cell-cycle-dependent irradiation, we sought to determine overall survival in mice receiving total-body irradiation (TBI) when administered granulocyte stimulating factor (G-CSF) at different time points. Gender differences were also studied. C57/BL/6J mice, aged 9-14 weeks, received 8 Gy TBI in a perspex cage using a linear accelerator. In each of five different experiments, three groups were studied: 1. one control group receiving TBI only; 2. one group treated with filgrastim [500 lg/kg subcutaneously/intraperitoneally (s.c./i.p.)] the day before TBI, followed by daily filgrastim injections postirradiation (1-5 days); and 3. one group treated with daily filgrastim injections only post-TBI (1-5 days). Each experimental group included male and female mice. Survival of the mice was monitored daily, and mice were euthanized when their condition deteriorated. A total of 293 mice were monitored for at least 37 days post-TBI. Control mice that received 8 Gy TBI showed a significant gender difference, with a median survival of 22 days in females and 17 days in males. Addition of G-CSF, irrespective of pre- or postirradiation, significantly improved survival, but in males the improvement was significantly better when G-CSF was not given before TBI. Improved survival in females was independent of the order of administration of GCSF. Multiple filgrastim injections were more effective than a single injection, and s.c. administration was not better than i.p. In conclusion, these findings indicate that male mice are more sensitive to TBI than females. Filgrastim improved survival in both genders irrespective of whether given pre- or postirradiation, but in males the improvement was significantly less if an injection was given before irradiation. These results suggest that, to prevent toxicity most effectively, GCSF should not be given before cytotoxic therapy. While a completely different experimental model was used here, these results may also be extrapolated to indicate that endocrine cell-cycle suppression therapy should not be given before or during cytotoxic therapy of hormone-dependent tumors (e.g., breast and prostate cancer), thus a reduction in the efficacy of cell-cycle-dependent therapy can be prevented.

The Future of Radiobiology

Innovation and progress in radiation oncology depend on discovery and insights realized through research in radiation biology. Radiobiology research has led to fundamental scientific insights, from the discovery of stem/progenitor cells to the definition of signal transduction pathways activated by ionizing radiation that are now recognized as integral to the DNA damage response (DDR). Radiobiological discoveries are guiding clinical trials that test radiation therapy combined with inhibitors of the DDR kinases DNA-dependent protein kinase (DNA-PK), ataxia telangiectasia mutated (ATM), ataxia telangiectasia related (ATR), and immune or cell cycle checkpoint inhibitors. To maintain scientific and clinical relevance, the field of radiation biology must overcome challenges in research workforce, training, and funding. The National Cancer Institute convened a workshop to discuss the role of radiobiology research and radiation biologists in the future scientific enterprise. Here, we review the discussions of current radiation oncology research approaches and areas of scientific focus considered important for rapid progress in radiation sciences and the continued contribution of radiobiology to radiation oncology and the broader biomedical research community.

Inhibition of the Continuum of Radiation-Induced Normal Tissue Injury by a Redox-Active Mn Porphyrin

Normal tissue damage after head and neck radiotherapy involves a continuum of pathologic events to the mucosa, tongue and salivary glands. We examined the radioprotective effects of MnBuOE, a redox-active manganese porphyrin, at three stages of normal tissue damage: immediate (leukocyte endothelial cell [L/E] interactions), early (mucositis) and late (xerostomia and fibrosis) after treatment. In this study, mice received 0 or 9 Gy irradiation to the oral cavity and salivary glands ± MnBuOE treatment. Changes in leukocyte-endothelial cell interactions were measured 24 h postirradiation. At 11 days postirradiation, mucositis was assessed with a cathepsin-sensitive near-infrared optical probe. Stimulated saliva production was quantified at 11 weeks postirradiation. Finally, histological analyses were conducted to assess the extent of long-term effects in salivary glands at 12 weeks postirradiation. MnBuOE reduced oral mucositis, xerostomia and salivary gland fibrosis after irradiation. Additionally, although we have previously shown that MnBuOE does not interfere with tumor control at high doses when administered with radiation alone, most head and neck cancer patients will be treated with the combinations of radiotherapy and cisplatin. Therefore, we also evaluated whether MnBuOE would protect tumors against radiation and cisplatin using tumor growth delay as an endpoint. Using a range of radiation doses, we saw no evidence that MnBuOE protected tumors from radiation and cisplatin. We conclude that MnBuOE radioprotects normal tissue at both early and late time points, without compromising anti-tumor effects of radiation and cisplatin.