Jeffrey Thompson - US grants

The development of amalgam-substitute materials is a high research priority due to environmental concerns associated with mercury management. Dental composites are likely to be the substitute material of choice for the foreseeable future. Other alternative materials (e.g., ceramics) are excessively complex and expensive. Current use of directly placed dental composites is somewhat limited, however, due to excessive polymerization shrinkage and inferior fracture and wear resistance. These characteristics can potentially lead to microleakage and the development of secondary caries, and reduce the life expectancy of composite restorations in load bearing applications. Because of these factors, current dental composites are recommended only for conservative applications. The use of novel fillers is one approach to expand the range of applications for currently available dental composite technology. Three-dimensional "scaffold-like" filler has been investigated in a variety of dental materials in limited studies with mixed results. The overall objective of the proposed research is to test the hypothesis that incorporation of a "scaffold-like" fused-fiber filler will decrease dental composite shrinkage, increase composite fracture resistance, and produce no adverse effects on composite wear resistance of standard dental composite compositions. The specific aims of the proposed research are to: (1) determine the effect of additions of prepolymerized fused-fiber filler particles on the overall volumetric shrinkage of standard dental composite compositions, (2) determine the effect of additions of prepolymerized fused-fiber filler particles on the flexural strength and fracture toughness of standard dental composite compositions, (3) determine the effect of additions of prepolymerized fused-fiber filler particles on the in vitro wear behavior of standard dental composite compositions, and (4) determine if there is any correlation between the fracture toughness and wear rate of modified and unmodified dental composite compositions. Volumetric shrinkage will be measured using specific gravity techniques. Fracture toughness will be determined by a controlled flaw fracture strength technique and through fractographic evaluation of fracture-initiating flaws. Wear will be simulated using a modified Leinfelder wear testing apparatus and measured using standard profilometric techniques. In addition, SEM and AFM will be used to characterize the prepolymerized fused-fiber filler particles and the modified composite microstructures.

DESCRIPTION: Development of non-metallic (e.g., amalgam-substitute) restorative materials is a high research priority due to environmental concerns associated with metals waste and disposal. Ceramics are an ideal candidate for replacing metal-based restorative materials. Ceramics provide excellent chemical durability; wear resistance, biocompatibility, environmental friendliness, and esthetics. Nevertheless, widespread all-ceramic restoration use has been hindered by concerns related to marginal fracture resistance and clinical longevity. Previous studies found that clinical fracture of all-ceramic restorations initiated along internal surfaces (e.g., bonded surfaces) almost exclusively. It is therefore critical to overcome fracture problems if these materials are to gain widespread acceptance. The overall goal of this continued research is to develop tougher, more fatigue-resistant all-ceramic dental restorations by minimizing or eliminating catastrophic effects of surface flaws through the implementation of RF-plasma sputter deposited thin-film ceramic surface coatings. Research conducted to date within the initial funded NIH grant has focused on microstructural control of deposited films and assessing their affect on the mechanical behavior of modified ceramic substrates. ZrO2 has been identified as the most appropriate thin film coating material. In addition, it has been found that ZrO2 thin-films produce no deleterious effect on bonding to a modified dental ceramic surface, or on the esthetic appearance of a translucent ceramic. The Specific Aims of this continued research are to: (1) test the hypothesis that the residual stress state and distribution within sputter deposited ZrO2 thin-films can be reproducibly controlled through manipulation of deposition parameters to produce constructs with predictable fracture resistance, (2) test the hypothesis that deposition of multi-layered thin-films with alternating high and low modulus layers can be used to produce substrate/thin-film laminate constructs with significantly greater facture toughness than is achieved with single-layer thin films, and (3) test the hypothesis that incorporation of sputter deposited ZrO2 thin-films will significantly enhance the fatigue resistance of specimens fabricated from traditional commercially available Dental ceramic materials. This technology needs further study to establish a more detailed understanding of the relationships between deposition parameters, thin-film microstructures, and short and long-term mechanical behavior of modified ceramics if a clinically efficacious process is to be developed.

DESCRIPTION (provided by applicant): Ultraviolet (UV) radiation poses a serious threat to human health through its damaging effects on DNA. Such damage interferes with fundamental cellular processes, and can cause permanent changes to the DNA, leading to abnormal cell activity and clinical problems such as cancer. To counter the deleterious effects of UV radiation and other mutagenic agents, cells possess an array of DNA damage response and repair systems. Dysfunction of these systems is the root cause of a variety of DNA damage sensitivity disorders in humans. DNA repair in eukaryotic organisms is influenced by a family of highly conserved proteins called histones, which serve to structurally organize and functionally regulate DNA in the nucleus. This regulation is achieved in part by numerous histone post-translational modifications, which can influence the association of chromatin binding proteins, such as those involved in transcription, replication, and DNA repair. As suggested by their broad functionality, disruption of these modifications is associated with various mammalian developmental anomalies and cancer. We and others have previously found that a specific histone modification, methylation of lysine-79 in histone H3 (H3K79), is important for the response to DNA damage caused by UV radiation. Using the yeast Saccharomyces cerevisiae as a model system, we have shown that loss of this modification renders cells hypersensitive to UV radiation, with genetic evidence indicating that this modification acts through a variety of DNA damage response and repair pathways. Furthermore, we have evidence suggesting that specific H3K79 methylation states (i.e. the number of methyl groups attached to H3K79) play distinct roles in the response to UV damage. Based on our collective observations and those of others, we propose that UV radiation, in conjunction with several other histone modifications, induces changes to the distribution of H3K79 methylation states in the cell, representing a novel DNA damage-induced trans-histone "crosstalk" pathway. In turn, these induced changes in H3K79 methylation states serve to regulate and coordinate specific DNA damage response and repair pathways. We plan to conduct a series of experiments to test this model, evaluating the proposed UV-induced trans-histone modification pathway, and examining several specific DNA repair pathways to determine the manner by which specific H3K79 methylation states influence these processes. These experiments will provide important insights into the relationship between histone modifications and DNA repair, and will invaluable for directing future work in this field. Given the conservation of histone modifications and DNA repair processes between yeast and humans, the results from this work will likely have implications for human health and cancer research, fitting the missions of the National Institute of General Medical Sciences and the National Cancer Institute. The proposed experiments will be conducted at a small undergraduate liberal arts institution, making this proposal highly appropriate for the Academic Research Enhancement Award (R15) program. Funding of this proposal will be used in part to provide research opportunities for undergraduate students, serving to encourage the pursuit of careers in biomedical research. PUBLIC HEALTH RELEVANCE: Damage to genetic information by environmental agents, such as ultraviolet radiation from sunlight, poses a serious risk to the survival of living organisms. While repair systems exist to rectify DNA damage, dysfunction of these systems can give rise to a wide range of clinical problems, including DNA damage sensitivity disorders and cancer. The proposal outlined in this application examines the role by which DNA packaging proteins, known as histones, participate in DNA repair. Histone proteins influence a broad array of cellular functions, and misregulation of these proteins is associated with diverse clinical issues, including cancer. From these studies, we will gain a greater understanding of how histones participate in the response to DNA damage, potentially revealing new therapeutic targets to treat related human health problems. Relevance to Undergraduate Education: In addition to the potential clinical benefits from this research project, this proposal has been designed to provide a variety of research opportunities for undergraduate students. Funds from this grant will be used to support two students to work in the Thompson laboratory during each of the three summers covered by this award, as well as one additional student per summer to work in the laboratories of Dr. Karolin Luger and Dr. Jessica Prenni at Colorado State University, where select experiments pertaining to this project will be executed. Funds will also enable students to attend and present their work at professional research conferences. Such experiences will inspire students to pursue graduate/professional studies in biomedical research, in addition to the contributions that these students will make towards the scientific goals of this project.

PROJECT SUMMARY/ABSTRACT This project describes a 5 year training program for a career as a physician-scientist with the long term goal of establishing a research program within the field of translational thoracic oncology. The applicant is currently an Instructor of Medicine in the Section of Interventional Pulmonology and Thoracic oncology conducting research in developing biomarkers for the treatment selection and monitoring of patients with lung cancer. The research focus of this proposal is to develop molecular markers to better identify the subgroup of patients that will respond to PD1/PDL1 therapies in order to avoid unnecessary toxicities, reduce costs, and enable more appropriate therapies to be delivered. This goal will be accomplished in three complementary specific aims. In Specific Aim 1, mRNA expression analyses will be performed on tumor tissue from advanced lung cancer patients treated with anti-PD1 therapy to determine the association of specific gene signatures with treatment response. In Specific Aim 2, a novel approach to acquire fresh tissue samples for immunophenotyping will be utilized to prospectively determine the ability of deep T cell phenotyping and functional assays to predict response to anti-PD1/PDL1 therapy using multi-parametric flow cytometry. In Specific Aim 3, a newly developed technique that enables the quantitative measurement of circulating PDL1 exosomes will be utilized to determine the association of pretreatment and on-treatment exosomal PDL1 expression levels to predict clinical outcomes in non-small cell lung cancer patients receiving checkpoint blockade. The training component of this proposal includes formal coursework, participation in a rich environment of post-doctoral lectures in thoracic oncology/tumor immunology, acquisition of advanced laboratory techniques (with a focus on bioinformatics and advanced flow cytometry), and individual mentoring. This project will take place under the supervision of Dr. Steven Albelda who is the Director of the Thoracic Oncology Laboratory at the University of Pennsylvania and Co-Director of the Abramson Cancer Center?s Translational Center of Excellence for Lung Cancer Immunobiology, and Dr. Anil Vachani who is the Director of Clinical Research for the Section of Interventional Pulmonology and Thoracic Oncology at Penn. Dr. Albelda and Dr. Vachani have mentored over 100 trainees. In addition, an advisory committee of distinguished scientists will provide experimental assistance, intellectual guidance, and career advice throughout the duration of this award.