Environmental cancer pilot projects
- Genotoxicity of epoxides from photochemical oxidation of biogenic volatile organic compounds contributing to SOA
- Formaldehyde-mediated bone barrow toxicity in FancD2 knock-out mice induced by methanol treatment
- Circadian oscillation of XPA expression in human hair follicles and PBMCs
- Role of the circadian clock in UV-induced skin carcinogenesis
- Melanoma: small signal molecules may characterize the disease and guide rational design of therapeutics
- Heterotypic interactions in breast responses to ionizing radiation
- Preclinical evaluation of genistein and soy extract in combination with conventional cytotoxic and hormonal treatment regimens for endometrial cancer
- Gastrointestinal stem cells and risk factors for colorectal adenoma
- Mutations in B-Raf Increase UV Genotoxicity in Melanocytes through Attenuation of DNA-damage Induced Cell-cycle Checkpoints
- Correlating breast cancer and obesity: detection of biomarkers of susceptibility using an obese mouse model
- Identification of polymorphisms in smoking induced genes
- Melanoma expression signatures and heterogeneity
The mechanism by which ultraviolet (UV) light aggravates the symptoms of the autoimmune disorder lupus erythematous (LE) is not clear. This is a problem because it signifies a lack of understanding of LE photosensitivity and represents a barrier to predicting patient disease outcomes. The objective of this interdisciplinary, collaborative pilot project is to examine how the small, excised, damage-containing DNA oligonucleotide (sedDNA) products of UV photoproduct repair impact the aberrant inflammatory and immune response pathways that define LE and to determine whether cutaneous LE patients develop autoantibodies against the proteins and sedDNAs that are involved in these signaling processes. The central hypothesis is that the association of sedDNAs with specific pattern recognition receptor proteins (PRRs) leads to the overstimulation or amplification of the autoimmune response in the skin of LE patients. Ultimately, this research has the potential to improve our understanding of LE patient photosensitivity and lead to the development of new tools for diagnosing, classifying, and treating LE patient subtypes. The preliminary data generated here will be used by Dr. Kemp to apply for R01-level funding.
Genotoxicity of epoxides from photochemical oxidation of biogenic volatile organic compounds contributing to SOA
Principal Investigator: Zhenfa Zhang, Ph.D., Research Assistant Professor, Department of Environmental Science and Engineering
Atmospheric photochemical oxidation of volatile organic compounds (VOC) forms gas phase products that are often more toxic than the parent compound. We recently demonstrated that oxidation of isoprene yields epoxydiol (IEPOX) isomers under low-NOx conditions and methacrylic acid epoxide (MAE) under high NOx conditions. Preliminary work shows that oxidation of 2-methyl-3-butene-2-ol (MBO) by ozone leads to two isomeric epoxides. These epoxides have not been previously identified in air; epoxides in general are genotoxic via alkylation of DNA. The hypothesis of this study is that health effects linked to SOA and VOC exposure may be attributable to genotoxicity induced by gas phase epoxides formed from photo-oxidation of BVOCs. To test the hypothesis, we propose the following specific aims: 1). Examine the capacity of IEPOX isomers, MAE and MBO epoxides to cause DNA damage in the DT40 DNA damage response assay and the Ames assay. In preliminary DT40 analysis REV1-/- and PCNAK164R/K164R cells are much more sensitive to IEPOX-2 and MAE than to MNU. 2) Characterize DNA adducts formed from deoxynucleosides or DNA exposed to authentic epoxides.
Formaldehyde has been classified by the IARC as a known human carcinogen that causes nasopharyngeal cancer and leukemia. However, the limited evidence for inhaled formaldehyde causing hematolymphopoietic cancers and the biological implausibility of the hypothesis that inhaled formaldehyde causes leukemia has raised many questions. While inhaled formaldehyde does not reach the bone marrow cells, methanol treatment (p.o.) significantly elevates the amount of formaldehyde DNA adducts in bone marrow cells in rats through metabolic activation in bone marrow. In this proposal, we will address whether Fanconi anemia group D2 (Fancd2) mutant mice are more susceptible to bone marrow cell toxicity and genotoxicity caused by methanol-derived formaldehyde than wild-type mice. The significance of this project is not only to demonstrate potential bone marrow toxicity caused by methanol-derived formaldehyde, but also to understand the formaldehyde-derived DNA adduct levels sufficient to initiate bone marrow toxicity in Fancd2-/- mice, which appear to be the most sensitive animal model of formaldehyde-mediated toxicity. These results will also be used as positive controls for future grant proposals to understand the potential for inhaled formaldehyde causing bone marrow toxicity.
Circadian oscillation of XPA expression in human hair follicles and PBMCs
Principal Investigator: Shobhan Gaddameedhi, Ph.D., Post-doctoral Fellow, Department of Biochemistry & Biophysics, School of Medicine
Skin cancer is the most common form of cancer in the United States. Recently, we found that the rate of Nucleotide Excision Repair (NER) due to XPA protein oscillates with a circadian rhythm in mouse skin with a minimum in the morning and a maximum in the evening. As a consequence, mice exposed to UV radiation (UVR) in early morning display an earlier onset and increased squamous cell carcinoma than mice exposed to UVR in the evening. The goal of this proposal is to compare the human XPA expression as a function of time of day by analyzing human hair follicles and PBMCs and to translate the basic science findings to potential health ramifications. If XPA oscillates in humans as a time of day, it is likely that the mutagenicity and carcinogenicity of sunlight and tanning beds may be strongly affected by the time of day of light exposure and it might be advisable for humans, to the extent possible, to restrict their occupational, therapeutic, recreational and cosmetic UVR exposure to a given time of day.
Role of the circadian clock in UV-induced skin carcinogenesis
Principal Investigator: Shobhan Gaddameedhi, Ph.D., Post-doctoral Fellow, Department of Biochemistry and Biophysics, School of Medicine.
Skin cancer is the most common form of cancer in the United States. Solar ultraviolet radiation (UVR) is a well-known human skin carcinogen. Exposure to the UVR causes DNA damage by generating photoproducts in DNA. In humans, these photoproducts are solely repaired by the process of nucleotide excision repair, and the loss of this repair system is strongly correlated with the development of skin cancer. We recently discovered that the circadian clock regulates nucleotide excision repair in mouse. Our preliminary results suggest that UV-induced DNA repair capacity varies in mouse skin as a function of time of day reaching its maximum in the evening (4 pm) and its minimum in the morning (4 am).The overall goal of this project is to understand how the circadian clock controls cellular responses to UV-induced DNA damage and to determine whether UV exposure at certain times of the day is more likely to cause skin cancer. These studies establish a rational for chrono-photo biology and suggests at what time of the day would be best for sunlight exposure and use of tanning beds.
Melanoma: small signal molecules may characterize the disease and guide rational design of therapeutics
Principal Investigator: Clark D. Jeffries, Research Professor, Department of Medicinal Chemistry and Natural Products, Eshelman School of Pharmacy.
Several labs have reported (Lu 2005) that TaqMan microRNA (miRNA) assays can reliably discern cancer types and stages. Applied Biosystems technology has enabled exceedingly specific and sensitive, simultaneous RT-qPCR assays of 373 miRNA species in one 384-well plate. After confirming performance reported by others (Chen 2005, Orina 2009), we are now prepared to apply the technology. A notable publication by Jukic et al. (Jukic 2010) described TaqMan results for FFPE samples from melanoma patients, including certain miRNAs dramatically differentiated. Our preliminary tests with RNA isolated from seven cell lines obtained from the UNC Program in Melanoma subsequently indicated that cell lines indeed capture the miRNA biology of melanoma concordantly with FFPE samples. Numerous advantages clearly attend use of cell lines. We must now increase the number of data points substantially, hence our pilot grant application. Funding for confirmation of our preliminary results will promptly enable a scientific paper and applications to major funding sources.
Effort in this pilot project will generate a novel murine “floxed” allele of an essential gene, Timeless. Timeless is a component of the replication fork protection complex that stabilizes DNA replication forks that are stalled at natural fork barriers and sites of UV-induced DNA damage. Reduced expression of Timeless should produce a condition of genomic instability leading to oncogenic events. UNC environmental melanoma investigators will use a conditionally activatable, melanocyte-specific CRE recombinase allele to selectively delete Timeless in melanocytes. Reduction in Timeless should enhance melanoma development and malignant progression. Additional studies will combine Timeless inactivation with other oncogenic events such as Ras activation to facilitate melanoma formation. To determine the contribution of Timeless to suppression of melanomagenesis, we propose the following specific aims: 1) to generate germ-line transmission of the floxed Timeless (TimLOXP) allele in C57Bl/6 mice; and 2) to breed TimLOXP mice with Tyr-Cre-ERT2 mice to generate mice with deletion of Timeless in melanocytes, and characterize the effects of somatic Timeless deletion in melanocytes. This project will determine whether an essential checkpoint mediator suppresses melanomagenesis in a murine model.
Heterotypic interactions between initiated epithelium and surrounding stroma play a critical role in development and progression of cancer. There is strong evidence that the stroma does not just passively respond to initiated cells, but plays a more active role in carcinogenesis. This project will test the hypothesis that stromal-epithelial interactions determine the ionizing radiation (IR) response phenotype of the breast. In Aim 1, the gene expression changes induced by stromal-epithelial interactions will be assessed in coculture. This aim will develop a model culture system for characterizing cell-cell interactions. In Aim 2, we will use this culture system to study IR responses. Using cells in monoculture and coculture, we will identify gene expression changes that occur in coculture and are correlated with phenotypic endpoints such as growth arrest and apoptosis. Responses will also be compared with what is observed in cultures of tissue explants. This project will develop and validate a model coculture system for testing hypotheses about the role of heterotypic interaction in environmental carcinogenesis and will provide important biological insights about breast responses to ionizing radiation.
Preclinical evaluation of genistein and soy extract in combination with conventional cytotoxic and hormonal treatment regimens for endometrial cancer
Principal Investigator: Victoria Bae-Jump, MD, PhD, Assistant Professor of Gynecologic Oncology
Treatment of women with recurrent or advanced endometrial cancer has been met with limited success. This has prompted a search for an additional agent which could be used in combination with more traditional therapies to dramatically increase efficacy while not increasing toxicities. Genistein, the bioactive isoflavone of soybeans, acts as a potential radiosensitizer for prostate cancer and has been shown to enhance the cytotoxicity of chemotherapeutic drugs in a variety of tumor types. Thus, our overall goal is to evaluate cell proliferation, telomerase activity and apoptosis in a novel endometrial cancer co-culture model system after exposure to genistein or soy extract in combination with cytotoxic and hormonal chemotherapeutic agents commonly used in the treatment of this disease. The effects of genistein or soy extract on estrogen and progesterone receptor signaling will also be explored. We hope that this will provide valuable evidence that phytoestrogens may potentiate the effects of other cytotoxic and hormonal agents in endometrial cancer, and that combination therapy may be a more effective treatment option for women with recurrent or advanced stage disease.
Gastrointestinal stem cells and risk factors for colorectal adenoma
Principal Investigator: Professor P. Kay Lund, Ph.D., Departments of Cell and Molecular Physiology, Nutrition and Pediatrics.
Colorectal cancer is thought to be initiated by inappropriate survival or expansion of crypt stem cells. Low apoptosis of crypt cells strongly predicts precancerous adenomas in multiple patient populations supporting this model. Elevated insulin, obesity, and high fat diet increase adenoma risk, and correlate with low apoptosis. However, definitive evidence for a role of stem cells in adenoma, or an effect of environmental factors on stem cells is lacking because no valid stem cell markers were available. Recent findings by others, and here at UNC, define GPR49/Lgr5 and SOX9 as markers of multipotent intestinal stem cells, and SOX4 as a potential biomarker of a subset of stem cells. Our studies in mice demonstrate that insulin signaling promotes survival of SOX9-positive stem cells and colon tumorigenesis. This pilot aims to translate these exciting findings to humans and directly test the hypothesis that adenoma, elevated plasma insulin, obesity, or high fat diet promote expansion of GPR49/Lgr5, SOX9 or SOX4 positive stem cells in normal colon, leading to selective expansion of the same stem-cell sub-type in adenomas.
Mutations in B-Raf Increase UV Genotoxicity in Melanocytes through Attenuation of DNA-damage Induced Cell-cycle Checkpoints
Principal Investigator: Dennis A. Simpson, PhD; Research Instructor, Dept. of Pathology and Laboratory Medicine, School of Medicine
Defects in DNA damage responses may underlie genetic instability and malignant progression in melanoma. Indeed melanomas harboring the most common mutation [B-Raf(V600E)] all exhibit attenuation in their DNA damage induced G2 checkpoint response. The molecular basis and biological result of this correlation between the B-Raf mutation and checkpoint attenuation is not clear. This proposal aims to begin to test the hypothesis that mutations in B-Raf result in attenuation of the DNA damage G2 checkpoint response and that this attenuation results in an increased sensitivity to UV induced mutations in additional genes such as CDKN2A, a gene frequently mutated in melanoma. This hypothesis will be tested by introduction of the B-Raf(V600E) allele into normal human melanocytes followed by precise measurements of the affects on cell cycle, including the DNA damage induced G2 checkpoint response. The majority of time in this proposal will be spent deriving the cell lines with which to test the hypothesis. We anticipate that these cell lines will be useful reagents for further studies of the early stages of melanoma progression regardless of the validity of the hypothesis.
Correlating breast cancer and obesity: detection of biomarkers of susceptibility using an obese mouse model
Principal Investigator: Christoph H. Borchers, Ph.D., Assistant Professor of Biochemistry and Biophysics
Breast cancer is a leading cause of cancer-related deaths among women, second only to lung cancer. Many epidemiological studies have uncovered a correlation between obesity and breast cancer. Not all obese women, however, will get breast cancer. Furthermore, the mitigating effects of exercise have also been postulated.
Our hypothesis is that there is a genetic basis for this difference in susceptibility and that it should be reflected in a difference in the proteome. The specific aim of this proposal is to discover protein biomarkers for breast cancer susceptibility in obese mice, which can be used to uncover the corresponding human biomarker. We will use quantitative proteomic approaches on blood from obese mice which did not develop breast cancer, vs. blood from mice which did develop breast cancer.
The results obtained will be used for a joint R01 between Dr. Borchers and Dr. Threadgill with the goal of using these biomarkers to study the mitigating effects of exercise in susceptible mice. Ultimately, we will develop a protein chip for screening human subjects in order to target prevention strategies to susceptible individuals.
The diversity of clinical behaviors of squamous cell carcinoma of the head and neck (SCCHN; cancer of the oral cavity, pharynx, and larynx) poses a challenge to the prevention and treatment of this disease. Our laboratory has used genome-wide expression profiles to classify SCCHN into four distinct and reproducible subtypes. These subtypes showed statistically significant differences in recurrence-free survival. One subtype showed high expression of antioxidant enzymes that are involved in xenobiotic metabolism including Glutathione S-Transferase M3, Thioredoxin Reductase 1, Glutathione Peroxidase 2, Aldo-Keto Reductase 1, and two genes involved in the pentose phosphate cycle (Transaldolase 1 and Phosphogluconate Dehydrogenase). We propose a unique translational study to: 1) “resequence” these four of these genes from 80 SCHHN tumors to identify Single Nucleotide Polymorphisms (SNP) and determine haplotype structure and 2) to evaluate the population allele frequencies for these SNP using samples from an ongoing UNC SCCHN case-control study. The proposed “resequencing” project will not only provide clues to the importance of genetic variation in these smoking-related genes but will also provide polymorphic markers for evaluation in many other population studies.
Melanoma is an environmentally-induced cancer which has increased in incidence at an alarming rate during the past few decades. A primary cause of melanoma is DNA damage due to ultraviolet radiation (UV) from sunlight. However, the wavelength, intensity, and pattern of UV exposure on the human body that lead to malignant melanoma have not been sufficiently characterized; and, based upon tumor site, histology, and different genetic alterations that occur, it is likely that melanoma is a heterogeneous disease with differing etiologies related to different exposures. Further studies of etiology would be greatly facilitated by a better understanding of melanoma heterogeneity, and we hypothesize that some of this heterogeneity can be elucidated through gene expression profiling. We propose to do gene expression profiling in the context of known mutations in melanoma. This pilot project would begin that process by identifying gene expression patterns associated with BRAF mutation in frozen and formalin-fixed paraffin-embedded melanoma tissues. This pilot study will provide the foundation for future studies of melanomagenesis in the context of environmental exposures.