Genetic susceptibility to patient-reported xerostomia among long-term oropharyngeal cancer survivors

Genetic susceptibility for xerostomia, a common sequela of radiotherapy and chemoradiotherapy for head and neck cancer, is unknown. Therefore, to identify genetic variants associated with moderate to severe xerostomia, we conducted a GWAS of 359 long-term oropharyngeal cancer (OPC) survivors using 579,956 autosomal SNPs. Patient-reported cancer treatment-related xerostomia was assessed using the MD Anderson Symptom Inventory. Patient response was dichotomized as moderate to severe or none to mild symptoms. In our study, 39.2% of OPC survivors reported moderate to severe xerostomia. Our GWAS identified eight SNPs suggestively associated with higher risk of moderate to severe xerostomia in six genomic regions (2p13.3, rs6546481, Minor Allele (MA) = A, ANTXR1, P = 4.3 × 10-7; 5p13.2-p13.1, rs16903936, MA = G, EGFLAM, P = 5.1 × 10-6; 4q21.1, rs10518156, MA = G, SHROOM3, P = 7.1 × 10-6; 19q13.42, rs11882068, MA = G, NLRP9, P = 1.7 × 10-5; 12q24.33, rs4760542, MA = G, GLT1D1, P = 1.8 × 10-5; and 3q27.3, rs11714564, MA = G, RTP1, P = 2.9 × 10-5. Seven SNPs were associated with lower risk of moderate to severe xerostomia, of which only one mapped to specific genomic region (15q21.3, rs4776140, MA = G, LOC105370826, a ncRNA class RNA gene, P = 1.5 × 10-5). Although our small exploratory study did not reach genome-wide statistical significance, our study provides, for the first time, preliminary evidence of genetic susceptibility to xerostomia. Further studies are needed to elucidate the role of genetic susceptibility to xerostomia.

A two-stage genome-wide association study of radiation-induced acute toxicity in head and neck cancer

BACKGROUND

Most head and neck cancer (HNC) patients receive radiotherapy (RT) and develop toxicities. This genome-wide association study (GWAS) was designed to identify single nucleotide polymorphisms (SNPs) associated with common acute radiation-induced toxicities (RITs) in an HNC cohort.

METHODS

A two-stage GWAS was performed in 1279 HNC patients treated with RT and prospectively scored for mucositis, xerostomia, sticky saliva, and dysphagia. The area under the curve (AUC) was used to estimate the average load of toxicity during RT. At the discovery study, multivariate linear regression was used in 957 patients, and the top-ranking SNPs were tested in 322 independent replication cohort. Next, the discovery and the replication studies were meta-analyzed.

RESULTS

A region on 5q21.3 containing 16 SNPs showed genome-wide (GW) significance association at P-value < 5.0 × 10-8 with patient-rated acute xerostomia in the discovery study. The top signal was rs35542 with an adjusted effect size of 0.17*A (95% CI 0.12 to 0.23; P-value <  = 3.78 × 10-9). The genome wide significant SNPs were located within three genes (EFNA5, FBXL17, and FER). In-silico functional analysis showed these genes may be involved in DNA damage response and co-expressed in minor salivary glands. We found 428 suggestive SNPs (P-value < 1.0 × 10-5) for other toxicities, taken to the replication study. Eleven of them showed a nominal association (P-value < 0.05).

CONCLUSIONS

This GWAS suggested novel SNPs for patient-rated acute xerostomia in HNC patients. If validated, these SNPs and their related functional pathways could lead to a predictive assay to identify sensitive patients to radiation, which may eventually allow a more individualized RT treatment.

Radiation induces submandibular gland damage by affecting Cdkn1a expression and regulating expression of miR-486a-3p in a xerostomia mouse model

BACKGROUND

Radiotherapy has been proven to be an effective treatment strategy for inhibiting head-and-neck cancer. However, side effects are common when using high-dosage irradiation, and the mechanism of action of this therapy has not been fully clarified.

OBJECTIVES

To discover targeting molecules involved in an electron radiation-induced xerostomia murine model.

MATERIAL AND METHODS

The xerostomia model mice were divided into Gy-3 (n = 5), Gy-7 (n = 5), and Gy-21 (n = 5) groups, and were compared to a negative control (NC) group. Drinking water amount, saliva volume, submandibular gland weight, and body weight were recorded. Real-time polymerase chain reaction (RT-PCR) was performed to amplify gene transcription. Hematoxylin and eosin (H&E) staining was used to identify submandibular gland damage. The dual-luciferase assay was used to observe the interaction between the Cdkn1a gene and miR-486a-3p.

RESULTS

Electron radiation significantly increased the drinking water amount, and decreased saliva volume and body weight compared to mice without radiation treatment (p < 0.05). The H&E staining showed that electron radiation damaged the submandibular gland. Electron radiation also triggered significantly higher transcription of the Cdkn1a gene in the submandibular gland of xerostomia mice compared to those without radiation treatment (p < 0.05). The dual-luciferase assay demonstrated that miR-486a-3p interacted with the Cdkn1a gene (miRNA-mRNA).

CONCLUSIONS

Radiation was found to induce damage of the submandibular gland and affect Cdkn1a expression by regulating the expression of miR-486a-3p in a xerostomia murine model. Therefore, modulation of miR-486a-3p and the Cdkn1a gene in a xerostomia murine model might improve damage of the submandibular gland.

A Novel Claudinopathy Based on Claudin-10 Mutations

Claudins are key components of the tight junction, sealing the paracellular cleft or composing size-, charge- and water-selective paracellular channels. Claudin-10 occurs in two major isoforms, claudin-10a and claudin-10b, which constitute paracellular anion or cation channels, respectively. For several years after the discovery of claudin-10, its functional relevance in men has remained elusive. Within the past two years, several studies appeared, describing patients with different pathogenic variants of the CLDN10 gene. Patients presented with dysfunction of kidney, exocrine glands and skin. This review summarizes and compares the recently published studies reporting on a novel autosomal-recessive disorder based on claudin-10 mutations.

Salivary Gland Dysplasia in Fgf10 Heterozygous Mice: A New Mouse Model of Xerostomia

Xerostomia, or chronic dry mouth, is a common syndrome caused by a lack of saliva that can lead to severe eating difficulties, dental caries and oral candida infections. The prevalence of xerostomia increases with age and affects approximately 30% of people aged 65 or older. Given the large numbers of sufferers, and the potential increase in incidence given our aging population, it is important to understand the complex mechanisms that drive hyposalivation and the consequences for the dentition and oral mucosa. From this study we propose the Fgf10 +/- mouse as a model to investigate xerostomia. By following embryonic salivary gland development, in vivo and in vitro, we show that a reduction in Fgf10 causes a delay in branching of salivary glands. This leads to hypoplasia of the glands, a phenotype that is not rescued postnatally or by adulthood in both male and female Fgf10 +/- mice. Histological analysis of the glands showed no obvious defect in cellular differentiation or acini/ductal arrangements, however there was a significant reduction in their size and weight. Analysis of saliva secretion showed that hypoplasia of the glands led to a significant reduction in saliva production in Fgf10 +/- adults, giving rise to a reduced saliva pellicle in the oral cavity of these mice. Mature mice were shown to drink more and in many cases had severe tooth wear. The Fgf10 +/- mouse is therefore a useful model to explore the causes and effects of xerostomia.

Differential gene expression in the salivary gland during development and onset of xerostomia in Sjögren's syndrome-like disease of the C57BL/6.NOD-Aec1Aec2 mouse

INTRODUCTION

Recently, we reported the development of the C57BL/6.NOD-Aec1Aec2 mouse that carries two genetic intervals derived from the non-obese diabetic (NOD) mouse capable of conferring Sjögren's syndrome (SjS)-like disease in SjS-non-susceptible C57BL/6 mice. In an attempt to define the molecular bases underlying the onset of stomatitis sicca (xerostomia) in this C57BL/6.NOD-Aec1Aec2 mouse model, we have carried out a study using genomic microarray technology.

METHODS

By means of oligonucleotide microarrays, gene expression profiles of salivary glands at 4, 8, 12, 16, and 20 weeks of age were generated for C57BL/6.NOD-Aec1Aec2 male mice. Using Linear Models for Microarray Analysis and B-statistics software, 480 genes were identified as being differentially expressed (P < 0.01 and Q < 0.0001) during the development of SjS-like disease in the salivary glands.

RESULTS

The 480 genes could be arranged into four clusters, with each cluster defining a unique pattern of temporal expression, while the individual genes within each cluster could be grouped according to related biological functions. By means of pair-wise analysis, temporal changes in transcript expressions provided profiles indicating that many additional genes are differentially expressed at specific time points during the development of disease. Multiple genes reportedly showing an association with autoimmunity and/or SjS, in either humans or mouse models, were found to exhibit differential expressions, both quantitatively and temporally. Selecting various families of genes associated with specific functions (for example, antibody production, complement, and chemokines), we noted that only a limited number of family members showed differential expressions and these correlated with specific phases of disease.

CONCLUSIONS

Taking advantage of known functions of these genes, investigators can construct interactive gene pathways, leading to modeling of possible underlying events inducing salivary gland dysfunction. Thus, these different approaches to analyzing microarray data permit the identification of multiple sets of genes of interest whose expressions and expression profiles may correlate with molecular mechanisms, signaling pathways, and/or immunological processes involved in the development and onset of SjS.

A case of major salivary gland agenesis

Major salivary gland agenesis is a rare disorder and only a few instances of the condition have been reported. The number of absent salivary glands and the degree of associated xerostomia vary between individuals. Salivary gland agenesis can cause profound xerostomia in children and there may be oral and upper respiratory tract sequelae, such as dental caries, candidiasis, ascending sialadenitis, laryngitis and pharyngitis. Salivary gland aplasia may be associated with other ectodermal defects, particularly abnormalities of the lacrimal apparatus. We report on the first observation of major salivary gland agenesis in South Korea. A child with xerostomia should be appropriately investigated and diagnosed, and careful attention should be paid to the prevention and treatment of sequelae.

Expression of aquaporin-5 in and fluid secretion from immortalized human salivary gland ductal cells by treatment with 5-aza-2'-deoxycytidine: a possibility for improvement of xerostomia in patients with Sjögren's syndrome

The aim of the present study was to investigate the possibility that ductal cells, which preferentially survive and/or proliferate in Sjögren's syndrome (SS) salivary glands of patients with SS, could acquire the functional expression of membrane water channel aquaporin-5 (AQP5). Thus, in this study, we demonstrate that an immortalized normal human salivary gland ductal cell (NS-SV-DC) line, lacking the expression of AQP5, acquires AQP5 gene expression in response to treatment with 5-aza-2'-deoxycytidine (5-Aza-CdR), a DNA demethylating agent. Confocal microscopic analysis revealed the localization of AQP5 expression mainly at the apical and lateral sides of the plasma membrane. The expressed AQP5 protein was functionally active because AQP5 expression resulted in a significant increase in the osmotically directed net fluid rate across monolayers of NS-SV-DC cells. By the analysis of bisulfite sequencing of CpG islands in the AQP5 promoter, hypermethylation within the consensus Sp1-binding sites was commonly observed in parental cell clones, whereas demethylation at the CGs, one in the second consensus Sp1 element and the other outside of the third consensus Sp1 element in the AQP5 promoter, was detected in NS-SV-DC cells after treatment with 5-Aza-CdR. By analyzing the luciferase activity of transfected AQP5 promoter vectors, it became evident that demethylation at the CGs cooperatively functions between these two sites to induce AQP5 expression. Our data, therefore, suggest that treatment of ductal cells with 5-Aza-CdR could result in the expression of the AQP5 gene, thereby leading to increased fluid secretion from ductal cells in SS salivary glands.

[The Levy-Hollister syndrome: a syndrome of dysplasias with ENT-manifestations]

The Levy-Hollister syndrome is characterized by a highly variable expression of dysplasia in different organ systems. Autosomal-dominant inheritance is recognised, but most cases are sporadic. In the field of otorhinolaryngology, xerostomia can be found due to aplasia of the major salivary glands, as well as congenital sensorineural, conductive or combined hearing loss and dysplasia of the auricles, mostly appearing as cup-shaped ears. Here we report on a 2-year-old boy with severe xerostomia. The disease was found to be caused by bilateral aplasia of the parotid and submandibular glands. There were also slight dysplasias of both auricles and a bilateral inner ear malformation as the origin of sensorineural hearing loss. Due to its highly variable expression, Levy-Hollister syndrome is often difficult to distinguish from other diseases and syndromes, so that the cooperation of different departments is necessary for an accurate diagnosis. Because of its dominant inheritance, a genetic consultation should be recommended to the patient. Auricular dysplasia and conductive hearing loss can possibly be treated surgically.

Oral manifestations of triple A syndrome

Triple A (four A; Allgrove syndrome) syndrome is a an autosomal recessive disorder characterized by alacrimia, achalasia, adrenocortical insufficiency, and various neurological abnormalities. We report a case of triple A syndrome in a 14-year-old female patient together with oral manifestations. The importance of this case report is to highlight the necessity of referring the young patients with xerostomia from dental to medical specialists.

Inherited risks for susceptibility to dental caries

Dental caries incidence is affected by host factors that may be related to the structure of dental enamel, immunologic response to cariogenic bacteria, or the composition of saliva. Genetic variation of the host factors may contribute to increased risks for dental caries. This systematic review examined the literature to address the question, "Is the risk for dental decay related to patterns of genetic inheritance?" Numerous reports have described a potential genetic contribution to the risk for dental caries. Studies on twins have provided strong evidence for the role of inheritance. Establishing a basis for a genetic contribution to dental caries will provide a foundation for future studies utilizing the human genome sequence to improve understanding of the disease process. Inherited disorders of tooth development with altered enamel structure increase the incidence of dental caries. Specific genetic linkage has not been determined for all of the syndromes of altered tooth development. Consequently, genetic screens of large populations for genes or mutations associated with increased caries susceptibility have not been done. Altered immune response to the cariogenic bacteria may also increase the incidence of caries. Association between specific patterns of HLA genetic inheritance and dental caries risk is weak and does not provide a predictable basis for predicting future decay rates. The evidence supporting an inherited susceptibility to dental caries is limited. Genetic linkage approaches on well-characterized populations with clearly defined dental caries incidence will be required to further analyze the relationship between inheritance and dental caries.

Major salivary gland flow rates in young and old, generally healthy African Americans and whites

Saliva is essential to maintain and preserve oral health. Previous studies of primarily white populations demonstrated that salivary gland flow rates are age-stable in healthy adults, but there are little data on African Americans of different ages. The purpose of this study was to determine if there is a relationship between age, gender, and race in unstimulated and stimulated parotid and submandibular salivary gland flow rates and to evaluate subjective responses to questions regarding salivary dysfunction. Sixty generally healthy, middle socioeconomic class African Americans and whites between the ages of 20 to 40 and 60 to 80 years were evaluated. The results indicate, in general, that objective and subjective measurements of major salivary gland flow rates are independent of age, gender, and race. Further studies are required using larger populations. These results suggest that signs and symptoms of dry mouth in the elderly regardless of race or gender should not be considered a normal sequela of aging.

Primary Sjögren's syndrome and other autoimmune diseases in families. Prevalence and immunogenetic studies in six kindreds

The relationships of human leukocyte antigen (HLA) and heavy chain immunoglobulin (Gm) haplotypes to disease and autoantibody expression were examined in six large kindreds, each having one or more members with primary Sjögren's syndrome. Various other autoimmune diseases and autoantibodies occurred among the 117 relatives in these families. The HLA and Gm haplotypes did not necessarily segregate persons into those with Sjögren's syndrome, other autoimmune disorders, or serologic abnormalities, but HLA alleles DR3 and DR2 occurred in significant excess in relatives with Sjögren's syndrome, irrespective of HLA haplotype. Segregation analysis suggested a Mendelian dominant genetic defect common to the many autoimmune diseases and serologic reactions that was not linked to HLA or Gm. A significant effect of female sex was also documented. These studies suggest that Sjögren's syndrome results from the interaction of several HLA-linked and non-HLA-linked genes.

[About 2 cases of "dry syndrome" associating xerophthalmy, xerostomy and cutaneous dryness. A new entity or an unrecognized diagnostic? (author's transl)]

Two cases, in children of distinct families, of a particular form of "dry syndrome", are described. This syndrom, which associates xerophthalmy, xerostomy and cutaneous dryness, is congenital and familial. He looks different from previously described diseases or syndroms which include one or several of these three components.