Faculty Bibliography

The hypothesis that sustained G protein-coupled receptor (GPCR) signaling from endosomes mediates pain is based on studies with endocytosis inhibitors and lipid-conjugated or nanoparticle-encapsulated antagonists targeted to endosomes. GPCR antagonists that reverse sustained endosomal signaling and nociception are needed. However, the criteria for rational design of such compounds are ill-defined. Moreover, the role of natural GPCR variants, which exhibit aberrant signaling and endosomal trafficking, in maintaining pain is unknown. Herein, substance P (SP) was found to evoke clathrin-mediated assembly of endosomal signaling complexes comprising neurokinin 1 receptor (NK₁R), Gα_q/i, and βarrestin-2. Whereas the FDA-approved NK₁R antagonist aprepitant induced a transient disruption of endosomal signals, analogs of netupitant designed to penetrate membranes and persist in acidic endosomes through altered lipophilicity and pKa caused sustained inhibition of endosomal signals. When injected intrathecally to target spinal NK₁R+ve neurons in knockin mice expressing human NK₁R, aprepitant transiently inhibited nociceptive responses to intraplantar injection of capsaicin. Conversely, netupitant analogs had more potent, efficacious, and sustained antinociceptive effects. Mice expressing C-terminally truncated human NK₁R, corresponding to a natural variant with aberrant signaling and trafficking, displayed attenuated SP-evoked excitation of spinal neurons and blunted nociceptive responses to SP. Thus, sustained antagonism of the NK₁R in endosomes correlates with long-lasting antinociception, and domains within the C-terminus of the NK₁R are necessary for the full pronociceptive actions of SP. The results support the hypothesis that endosomal signaling of GPCRs mediates nociception and provides insight into strategies for antagonizing GPCRs in intracellular locations for the treatment of diverse diseases.

PURPOSE/OBJECTIVE:Head and neck cancer (HNC) treatment results in morbidity impacting quality of life (QOL) in survivorship. This analysis evaluated changes in oral health-related QOL (OH-QOL) up to 2 years after curative intent radiation therapy (RT) for HNC patients and factors associated with these changes. METHODS:572 HNC patients participated in a multicenter, prospective observational study (OraRad). Data collected included sociodemographic, tumor, and treatment variables. Ten single-item questions and 2 composite scales of swallowing problems and senses problems (taste and smell) from a standard QOL instrument were assessed before RT and at 6-month intervals after RT. RESULTS:The most persistently impacted OH-QOL variables at 24 months included: dry mouth; sticky saliva, and senses problems. These measures were most elevated at the 6-month visit. Aspects of swallowing were most impacted by oropharyngeal tumor site, chemotherapy, and non-Hispanic ethnicity. Problems with senses and dry mouth were worse with older age. Dry mouth and sticky saliva increased more among men and those with oropharyngeal cancer, nodal involvement, and use of chemotherapy. Problems with mouth opening were increased by chemotherapy and were more common among non-White and Hispanic individuals. A 1000 cGy increase in RT dose was associated with a clinically meaningful change in difficulty swallowing solid food, dry mouth, sticky saliva, sense of taste, and senses problems. CONCLUSIONS:Demographic, tumor, and treatment variables impacted OH-QOL for HNC patients up to 2 years after RT. Dry mouth is the most intense and sustained toxicity of RT that negatively impacts OH-QOL of HNC survivors. GOV IDENTIFIER/UNASSIGNED:NCT02057510; first posted February 7, 2014.

Although generally regarded as degradatory enzymes, certain proteases are also signaling molecules that specifically control cellular functions by cleaving protease-activated receptors (PARs). The four known PARs are members of the large family of G protein-coupled receptors. These transmembrane receptors control most physiological and pathological processes and are the target of a large proportion of therapeutic drugs. Signaling proteases include enzymes from the circulation, from immune, inflammatory epithelial and cancer cells, as well as from commensal and pathogenic bacteria. Advances in our understanding of the structure and function of PARs provide insights into how diverse proteases activate these receptors to regulate physiological and pathological processes in most tissues and organ systems. The realization that proteases and PARs are key mediators of disease, coupled with advances in understanding the atomic level structure of PARs and their mechanisms of signaling in subcellular microdomains, has spurred the development of antagonists, some of which have advanced to the clinic. Herein we review the discovery, structure and function of this receptor system, highlight the contribution of PARs to homeostatic control, and discuss the potential of PAR antagonists for the treatment of major diseases.

Head and neck squamous cell carcinoma (HNSCC) causes more severe pain and psychological stress than other types of cancer. Despite clinical evidence linking pain, stress, and cancer progression, the underlying relationship between pain and sympathetic neurotransmission in oral cancer is unknown. We found that human HNSCC tumors and mouse tumor tissue are innervated by peripheral sympathetic and sensory nerves. Moreover, [beta]-adrenergic 1 and 2 receptors ([beta]-AR) are overexpressed in human oral cancer cell lines, and norepinephrine treatment increased [beta]-AR2 protein expression as well as cancer cell proliferation in vitro. We have recently demonstrated that inhibition of tumor necrosis factor alpha (TNF[alpha]) signaling reduces oral cancer-induced nociceptive behavior. Norepinephrine-treated cancer cell lines secrete more TNF[alpha] which, when applied to tongue-innervating trigeminal neurons, evoked a larger Ca2+ transient; TNF-TNFR inhibitor blocked the increase in the evoked Ca2+ transient. Using an orthotopic xenograft oral cancer model, we found that mice demonstrated significantly less orofacial cancer-induced nociceptive behavior during systemic [beta]-adrenergic inhibitory treatment with propranolol. Furthermore, chemical sympathectomy via guanethidine led to a significant reduction in tumor size and nociceptive behavior. We infer from these results that sympathetic signaling modulates oral cancer pain via TNF[alpha] secretion and tumorigenesis. Further investigation of the role of neuro-cancer communication in cancer progression and pain is warranted.

INTRODUCTION/BACKGROUND:Oral cancer patients suffer severe chronic and mechanically-induced pain at the site of the cancer. Our clinical experience is that oral cancer patients report new sensitivity to spicy foods. We hypothesized that in cancer patients, mechanical and chemical sensitivity would be greater when measured at the cancer site compared to a contralateral matched normal site. METHODS:We determined mechanical pain thresholds (MPT) on the right and left sides of the tongue of 11 healthy subjects, and at the cancer and contralateral matched normal site in 11 oral cancer patients in response to von Frey filaments in the range of 0.008 to 300 g (normally not reported as painful). We evaluated chemical sensitivity in 13 healthy subjects and seven cancer patients, who rated spiciness/pain on a visual analog scale in response to exposure to six paper strips impregnated with capsaicin (0-10 mM). RESULTS:Mechanical detection thresholds (MDT) were recorded for healthy subjects, but not MPTs. By contrast, MPTs were measured at the site of the cancer in oral cancer patients (7/11 patients). No MPTs were measured at the cancer patients' contralateral matched normal sites. Measured MPTs were correlated with patients' responses to the University of California Oral Cancer Pain Questionnaire. Capsaicin sensitivity at the site of the cancer was evident in cancer patients by a leftward shift of the cancer site capsaicin dose-response curve compared to that of the patient's contralateral matched normal site. We detected no difference in capsaicin sensitivity on the right and left sides of tongues of healthy subjects. CONCLUSIONS:Mechanical and chemical sensitivity testing was well tolerated by the majority of oral cancer patients. Sensitivity is greater at the site of the cancer than at a contralateral matched normal site.

Oral cancer pain is attributed to the release from cancers of mediators that sensitize and activate sensory neurons. Intraplantar injection of conditioned media (CM) from human tongue cancer cell line HSC-3 or OSC-20 evokes nociceptive behavior. By contrast, CM from noncancer cell lines, DOK, and HaCaT are non-nociceptive. Pain mediators are carried by extracellular vesicles (EVs) released from cancer cells. Depletion of EVs from cancer cell line CM reverses mechanical allodynia and thermal hyperalgesia. CM from non-nociceptive cell lines become nociceptive when reconstituted with HSC-3 EVs. Two miRNAs (hsa-miR-21-5p and hsa-miR-221-3p) are identified that are present in increased abundance in EVs from HSC-3 and OSC-20 CM compared to HaCaT CM. The miRNA target genes suggest potential involvement in oral cancer pain of the toll like receptor 7 (TLR7) and 8 (TLR8) pathways, as well as signaling through interleukin 6 cytokine family signal transducer receptor (gp130, encoded by IL6ST) and colony stimulating factor receptor (G-CSFR, encoded by CSF3R), Janus kinase and signal transducer and activator of transcription 3 (JAK/STAT3). These studies confirm the recent discovery of the role of cancer EVs in pain and add to the repertoire of algesic and analgesic cancer pain mediators and pathways that contribute to oral cancer pain.

PURPOSE/OBJECTIVE:To elucidate long-term sequelae of radiation therapy (RT) in head and neck cancer (HNC) patients, a multi-center prospective study, Clinical Registry of Dental Outcomes in Head and Neck Cancer Patients (OraRad), was established with tooth failure as its primary outcome. We report tooth failure and associated risk factors. METHODS:Demographics, cancer and dental disease characteristics were documented in 572 HNC patients at baseline and 6, 12, 18, and 24 months after RT. Eligible patients were age 18 or older, diagnosed with HNC, and receiving RT to treat HNC. Tooth failure during follow-up was defined as losing a tooth or having a tooth deemed hopeless. Analyses of time to first tooth-failure event and number of teeth that failed used Kaplan-Meier estimators, Cox regression, and generalized linear models. RESULTS:At 2 years, the estimated fraction of tooth failure was 17.8% (95% confidence interval [CI]: 14.3%-21.3%). Number of teeth that failed was higher for those with fewer teeth at baseline (p<0.0001), greater reduction in salivary flow rate (p=0.013), and non-compliance with daily oral hygiene (p=0.03). Patients with dental caries at baseline had higher risk of tooth failure with decreased salivary flow. Patients who were oral hygiene non-compliant at baseline but compliant at all follow-up visits had the fewest teeth that failed; greatest tooth failure occurred in participants who were non-compliant at baseline and follow-up. CONCLUSION/CONCLUSIONS:Despite pre-RT dental management, substantial tooth failure occurs within 2 years after RT for HNC. Identified factors may help to predict or reduce risk of post-RT tooth failure.

OBJECTIVE:The aim of this study was to examine effects of radiation therapy (RT) for head and neck cancer (HNC) on periodontal disease and relationships to caries. STUDY DESIGN/METHODS:A multicenter prospective observational cohort study (OraRad) was conducted in patients undergoing RT for HNC. Assessments were conducted by calibrated examiners at the pre-RT (baseline) visit (n = 533), the 12-month visit (n = 414), and the 24-month visit (n = 365). RESULTS:The average whole mouth mean (standard error (SE)) distance from the cementoenamel junction to the gingival margin (CEJ-GM) decreased significantly from 0.43 (0.04) mm at baseline to 0.24 (0.04) mm at 12 months and 0.11 (0.04) mm at 24 months (P ≤ .001). Whole mouth mean (SE) percentage of sites with CEJ-GM distance of <0 mm increased significantly from 23.3% (1.0%) at baseline to 28.5% (1.0%) at 12 months and 30.5% (1.1%) at 24 months (P ≤ .02). Higher mean radiation dose to the mandible was associated with a greater increase in the percentage of mandibular sites with CEJ-GM distance of <0 mm (P = .003). Both mean CEJ-GM distance and the percentage of sites with a CEJ-GM distance <0 mm were strongly associated with whole mouth mean proportion of decayed, missing, and filled surfaces, as well as proportion of decayed or filled facial/buccal surfaces specifically, (P < .001), with greater gingival recession associated with increased caries. CONCLUSIONS:RT for HNC leads to mandibular gingival recession in a dose-dependent manner. This gingival recession may contribute to increased risk for cervical caries seen in these patients.

Soft polymer nanoparticles designed to disassemble and release an antagonist of the neurokinin 1 receptor (NK₁R) in endosomes provide efficacious yet transient relief from chronic pain. These micellar nanoparticles are unstable and rapidly release cargo, which may limit the duration of analgesia. We examined the efficacy of stable star polymer nanostars containing the NK₁R antagonist aprepitant-amine for the treatment of chronic pain in mice. Nanostars continually released cargo for 24 h, trafficked through the endosomal system, and disrupted NK₁R endosomal signaling. After intrathecal injection, nanostars accumulated in endosomes of spinal neurons. Nanostar-aprepitant reversed mechanical, thermal and cold allodynia and normalized nociceptive behavior more efficaciously than free aprepitant in preclinical models of neuropathic and inflammatory pain. Analgesia was maintained for >10 h. The sustained endosomal delivery of antagonists from slow-release nanostars provides effective and long-lasting reversal of chronic pain.

BACKGROUND/UNASSIGNED:Treatment for head and neck cancer (HNC) such as radiotherapy (RT) can lead to numerous acute and chronic head and neck sequelae, including dental caries. The goal of the present study was to measure 2-y changes in dental caries after radiotherapy in patients with HNC and test risk factors for caries increment. METHODS/UNASSIGNED:Cancer and dental disease characteristics, demographics, and oral health practices were documented before and 6, 12, 18, and 24 mo after the start of RT for 572 adult patients with HNC. Patients were eligible if they were age 18 y or older, diagnosed with HNC, and planned to receive RT for treatment of HNC. Caries prevalence was measured as decayed, missing, and filled surfaces (DMFS). The association between change in DMFS and risk factors was evaluated using linear mixed models. RESULTS/UNASSIGNED:= 164), lower salivary flow at follow-up visits was associated with increased DMFS. CONCLUSION/UNASSIGNED:Increased caries is a complication soon after RT in HNC. Fluoride, oral hygiene, dental insurance, and education level had the strongest association with caries increment after radiotherapy to the head and neck region. Thus, intensive oral hygiene measures, including fluoride and greater accessibility of dental care, may contribute to reducing the caries burden after RT in HNC. KNOWLEDGE TRANSFER STATEMENT/UNASSIGNED:The results of this study can be used by clinicians when deciding how to minimize oral complications related to cancer therapy for patients with head and neck cancer. Identification of modifiable factors (e.g., oral hygiene and prescription fluoride compliance) associated with increased caries risk can minimize radiation caries burden.