Caries Removal by First-Year Dental Students: A Multisource Competency Assessment Strategy for Reflective Practice.

Multisource assessment (MSA) uses multiple assessors to provide feedback. Little is known about the validity of using MSA feedback for improving students' ability to self-assess in a preclinical environment. Therefore, the aim of this study was to measure the validity of using a defined reflective process involving an MSA tool for building skill in dental students' self-evaluation of caries excavation on extracted teeth. As part of this process, 104 first-year students at one U.S. dental school used a self-generated study plan (SGSP) for structured reflection on MSA feedback during the 2013-14 academic year. Interrater agreement, determined through calculation of percentage-agreements in scoring, was measured among three assessor groups (self-, peer, and expert assessors) in formative assessment and between two assessor groups (self- and expert assessors) in summative assessment two weeks apart, allowing for reflective practice and completion of an SGSP between assessments. Validity for improving self-assessment was determined by measuring significance in positive shifts of agreement between self- and expert assessors. The results showed that interrater agreement between the self- and expert assessors increased significantly: from a 28% agreement in formative assessment to a 60% agreement in summative assessment. Significance in percentage shifts between assessments was demonstrated with a McNemar score of 0.26 (p<0.001). These results suggest that the described MSA tool and reflective process in an SGSP may be valid methods for improving skill in student self-evaluation of competence in caries excavation on extracted teeth.

Complications after use of elastomeric pressure-indicating media at 24-hour follow-up visit for immediate maxillary complete removable dental prosthesis: A clinical report.

Various pressure-indicating media are available to assess the adaptation of the intaglio surface of a removable dental prosthesis at the insertion and follow-up appointments. This clinical report describes the use of an elastomer that entered the maxillary sinus through an undetected oroantral communication at the 24-hour follow-up for an immediate maxillary complete removable dental prosthesis. A Caldwell-Luc sinusotomy procedure was required to remove the material, and the patient required over 1 year of healing time before his reported symptoms resolved.

Galanin modulates the neural niche to favour perineural invasion in head and neck cancer.

Perineural invasion (PNI) is an indicator of poor survival in multiple cancers. Unfortunately, there is no targeted treatment for PNI since the molecular mechanisms are largely unknown. PNI is an active process, suggesting that cancer cells communicate with nerves. However, nerve-tumour crosstalk is understudied due to the lack of in vivo models to investigate the mechanisms. Here we developed an in vivo model of PNI to characterize this interaction. We show that the neuropeptide galanin (GAL) initiates nerve-tumour crosstalk via activation of its G protein-coupled receptor, GALR2. Our data reveal a novel mechanism by which GAL from nerves stimulates GALR2 on cancer cells to induce NFATC2-mediated transcription of cyclooxygenase-2 and GAL. Prostaglandin E2 promotes cancer invasion, and in a feedback mechanism, GAL released by cancer induces neuritogenesis, facilitating PNI. This study describes a novel in vivo model for PNI and reveals the dynamic interaction between nerve and cancer.

TRIP13 promotes error-prone nonhomologous end joining and induces chemoresistance in head and neck cancer.

Squamous cell carcinoma of the head and neck (SCCHN) is a common, aggressive, treatment-resistant cancer with a high recurrence rate and mortality, but the mechanism of treatment resistance remains unclear. Here we describe a mechanism where the AAA-ATPase TRIP13 promotes treatment resistance. Overexpression of TRIP13 in non-malignant cells results in malignant transformation. High expression of TRIP13 in SCCHN leads to aggressive, treatment-resistant tumors and enhanced repair of DNA damage. Using mass spectrometry, we identify DNA-PKcs complex proteins that mediate nonhomologous end joining (NHEJ), as TRIP13-binding partners. Using repair-deficient reporter systems, we show that TRIP13 promotes NHEJ, even when homologous recombination is intact. Importantly, overexpression of TRIP13 sensitizes SCCHN to an inhibitor of DNA-PKcs. Thus, this study defines a new mechanism of treatment resistance in SCCHN and underscores the importance of targeting NHEJ to overcome treatment failure in SCCHN and potentially in other cancers that overexpress TRIP13.

The G protein-coupled receptor GALR2 promotes angiogenesis in head and neck cancer.

Squamous cell carcinoma of the head and neck (SCCHN) is an aggressive disease with poor patient survival. Galanin receptor 2 (GALR2) is a G protein-coupled receptor that induces aggressive tumor growth in SCCHN. The objective of this study was to investigate the mechanism by which GALR2 promotes angiogenesis, a critical oncogenic phenotype required for tumor growth. The impact of GALR2 expression on secretion of proangiogenic cytokines in multiple SCCHN cell lines was investigated by ELISA and in vitro angiogenesis assays. Chemical inhibitor and genetic knockdown strategies were used to understand the key regulators. The in vivo impact of GALR2 on angiogenesis was investigated in mouse xenograft, chick chorioallantoic membrane, and the clinically relevant mouse orthotopic floor-of-mouth models. GALR2 induced angiogenesis via p38-MAPK-mediated secretion of proangiogenic cytokines, VEGF, and interleukin-6 (IL-6). Moreover, GALR2 activated small-GTP-protein, RAP1B, thereby inducing p38-mediated inactivation of tristetraprolin (TTP), which functions to destabilize cytokine transcripts. This resulted in enhanced secretion of proangiogenic cytokines and angiogenesis in vitro and in vivo. In SCCHN cells overexpressing GALR2, inactivation of TTP increased secretion of IL-6 and VEGF, whereas inhibition of p38 activated TTP and decreased cytokine secretion. Here, we report that GALR2 stimulates tumor angiogenesis in SCCHN via p38-mediated inhibition of TTP with resultant enhanced cytokine secretion. Given that p38 inhibitors are in clinical use for inflammatory disorders, GALR2/p38-mediated cytokine secretion may be an excellent target for new adjuvant therapy in SCCHN.

Characterization of squamous cell carcinoma in an organotypic culture via subsurface non-linear optical molecular imaging.

Tristetraprolin (TTP) is an RNA-binding protein which downregulates multiple cytokines that mediate progression of head and neck squamous cell carcinoma (HNSCC). We previously showed that HNSCC cells with shRNA-mediated knockdown of TTP are more invasive than controls. In this study, we use control and TTP-deficient cells to present a novel subsurface non-linear optical molecular imaging method using a three-dimensional (3D) organotypic construct, and compare the live cell imaging data to histology of fixed tissue specimens. This manuscript describes how to prepare and image the novel organotypic system that closely mimics HNSCC in a clinical setting. The oral cancer equivalent (OCE) system allows HNSCC cells to stratify and invade beyond the basement membrane into underlying connective tissue prepared from decellularized human dermal tissue. The OCE model was inspired by tissue engineering strategies to prepare autologous transplants from human keratinocytes. Advantages of this method over previously used in vitro cancer models include the simulation of the basement membrane and complex connective tissue in the construct, in addition to the ability to track the 3D movement of live invading cells and quantify matrix destruction over time. The OCE model and novel live cell imaging strategy may be applied to study other types of 3D tissue constructs.

Inactivation or loss of TTP promotes invasion in head and neck cancer via transcript stabilization and secretion of MMP9, MMP2, and IL-6.

PURPOSE: Invasion is the critical step in progression of a precancerous lesion to squamous cell carcinoma of the head and neck (HNSCC). Invasion is regulated by multiple proinflammatory mediators. Tristetraprolin (TTP) is an mRNA-degrading protein that regulates multiple proinflammatory mediators. TTP may serve as an excellent treatment target. Rap1 is a ras-like oncoprotein that induces critical signaling pathways. In this study, the role of rap1 in TTP-mediated invasion was investigated. EXPERIMENTAL DESIGN: Using complementary approaches, we modulated TTP and altered expression of interleukin (IL)-6 and matrix metalloproteinase (MMP) 2/9, which were quantified by ELISA and zymogram. Invasion was evaluated in vitro using the oral-cancer-equivalent (OCE) three-dimensional model and in vivo in the chick chorioallantoic membrane (CAM). The role of rap1 and p38 were established using knockdown strategies. RESULTS: Downregulation of TTP significantly increased invasion via secretion of MMP9/2 and IL-6. In the novel OCE and CAM invasion models of HNSCC, cells with downregulated TTP destroyed the basement membrane to invade the underlying connective tissue. Rap1 induces p38 mitogen-activated protein kinase (p38)-mediated inactivation of TTP. Inactive TTP enhances transcript stability via binding to the 3'-untranslated region (UTR). High IL-6 and MMP9 are prognostic for poor clinical outcomes in patients with HNSCC. CONCLUSIONS: Targeting the rap1-p38-TTP cascade is an attractive novel treatment strategy in HNSCC to concurrently suppress multiple mediators of invasion.

Rap1 and its regulatory proteins: the tumor suppressor, oncogene, tumor suppressor gene axis in head and neck cancer.

Squamous cell carcinoma of the head and neck (SCCHN) is the sixth most common cancer, globally. Previously, we showed that Rap1GAP is a tumor suppressor gene that inhibits tumor growth, but promotes invasion in SCCHN. In this work, we discuss the role of Rap1 and Rap1GAP in SCCHN progression in the context of a microRNA-oncogene-tumor suppressor gene axis, and investigate the role of Rap1GAP in EZH2-mediated invasion. Loss of expression of microRNA-101 in SCCHN leads to upregulation of EZH2, a histone methyltransferase. Overexpression of EZH2 silences Rap1GAP via methylation, thereby promoting activation of its target, Rap1. This microRNA-controlled activation of Rap1, via EZH2-mediated silencing of Rap1GAP, is a novel mechanism of Rap1 regulation. In two independent SCCHN cell lines, downregulation of EZH2 inhibits proliferation and invasion. In both cell lines, stable knockdown of EZH2 (shEZH2) recovers Rap1GAP expression and inhibits proliferation. However, siRNA-mediated knockdown of Rap1GAP in these cells rescues proliferation but not invasion. Thus, EZH2 promotes proliferation and invasion via Rap1GAP-dependent and -independent mechanisms, respectively. Although the studies presented here are in the context of SCCHN, our results may have broader implications, given that Rap1GAP acts as a tumor suppressor in pancreatic cancer, thyroid cancer, and melanoma.

Tristetraprolin regulates interleukin-6, which is correlated with tumor progression in patients with head and neck squamous cell carcinoma.

BACKGROUND: Tumor-derived cytokines play a significant role in the progression of head and neck squamous cell carcinoma (HNSCC). Targeting proteins, such as tristetraprolin (TTP), that regulate multiple inflammatory cytokines may inhibit the progression of HNSCC. However, TTP's role in cancer is poorly understood. The goal of the current study was to determine whether TTP regulates inflammatory cytokines in patients with HNSCC. METHODS: TTP messenger RNA (mRNA) and protein expression were determined by quantitative real-time-polymerase chain reaction (Q-RT-PCR) and Western blot analysis, respectively. mRNA stability and cytokine secretion were evaluated by quantitative RT-PCR and enzyme-linked immunoadsorbent assay, respectively, after overexpression or knockdown of TTP in HNSCC. HNSCC tissue microarrays were immunostained for interleukin-6 (IL-6) and TTP. RESULTS: TTP expression in HNSCC cell lines was found to be inversely correlated with the secretion of IL-6, vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE(2) )(.) Knockdown of TTP increased mRNA stability and the secretion of cytokines. Conversely, overexpression of TTP in HNSCC cells led to decreased secretion of IL-6, VEGF, and PGE(2) . Immunohistochemical staining of tissue microarrays for IL-6 demonstrated that staining intensity is prognostic for poor disease-specific survival (P = .023), tumor recurrence and development of second primary tumors (P = .014), and poor overall survival (P = .019). CONCLUSIONS: The results of the current study demonstrated that down-regulation of TTP in HNSCC enhances mRNA stability and promotes secretion of IL-6, VEGF, and PGE(2) . Furthermore, high IL-6 secretion in HNSCC tissue is a biomarker for poor prognosis. In as much as enhanced cytokine secretion is associated with poor prognosis, TTP may be a therapeutic target to reduce multiple cytokines concurrently in patients with HNSCC.

Periodontal pathogen levels in adolescents before, during, and after fixed orthodontic appliance therapy.

INTRODUCTION: This purpose of this study was to document and investigate changes in periodontal pathogen levels before, during, and after orthodontic treatment in adolescents. METHODS: DNA gene probe analysis was used to quantify the levels of 8 periodontal pathogens before, during, and after treatment with fixed orthodontic appliances in 190 concurrently treated adolescent orthodontic patients. The 8 pathogens examined were Actinobacillus actinomycetemcomitans (AA), Porphyromonas gingivalis (PG), Prevotella intermedia (PI), Tannerella forsythia (TF), Eikenella corrodens (EC), Fusobacterium nucleatum (FN), Treponema denticola (TD), and Campylobacter rectus (CR). Chi-square tests were used to determine whether the percentages of subjects with high counts significantly changed over time. Logistic regression analyses were also performed to derive the relative risk of higher counts of pathogenic bacteria with fixed appliances at the various time intervals studied. RESULTS: For 6 (PI, TF, EC, FN, TD, CR) of the 8 pathogens, the percentages of subjects with high pathogen counts increased significantly after 6 months of fixed appliance treatment, but these returned to pretreatment levels by 12 months of orthodontic treatment. No pathogen level was significantly higher after 12 months of orthodontic treatment, and orthodontic treatment was found to be significantly protective for half of the pathogens (EC, FN, TD, CR) posttreatment. CONCLUSIONS: Orthodontic treatment with fixed appliances does not increase the risk of high levels of these periodontal pathogens.