Several research projects are ongoing in our laboratory. These can be divided into three general categories as outlined below.
Mechanistic understanding and toxicological significance of CYP1 and CYP19
Cytochrome P450s are drug metabolizing enzymes with broad substrate specificities that are responsible for biological oxidation and reduction reactions. The CYP1 family including CYP1C1 and CYP1B1 are induced by environmental contaminants such as polycyclic aromatic hydrocarbons (PAHs) and the halogenated aromatic hydrocarbons (PCBs and dioxins). CYP19 (aromatase) is responsible for conversion of testosterone to estrogen. Research in our laboratory is studying various aspects of how these genes are regulated to better understand their potential roles in carcinogenesis, developmental toxicity and endocrine disruption. Fundulus heteroclitus, an estuarine fish, and catfish are being used as model organisms in these studies.
Potential for flavonoids found in natural products to be cancer chemotherapeutics
The hypothesis guiding our research is that certain flavonoids interact with drug metabolizing enzymes in a way that is anticarcinogenic. Thus, some flavonoids could provide cancer chemoprotection. Because CYP1B1 is induced in cancer cells and is involved in activation of estrogen and polycyclic aromatic hydrocarbons (PAHs) to genotoxic metabolites, our goal is to find specific CYP1B1 inhibitors. In the United States, prostate cancer is the second leading cause of cancer death in men, while endometrial cancer is the most common gynecological malignancy in women. Therefore, we are using RL95-2 endometrial and 22Rv1 prostate cancer cells to investigate these hypotheses.
Use of in vitro bioassay to assess sediment and water samples for
estrogenic and CYP1A-mediated activities
In vitro tests are being increasingly used as screening tools
in risk assessments. In vitro bioassays have several advantages over in vivo approaches for environmental monitoring. Typically they offer a cheaper and more
rapid way to screen large numbers of samples with high statistical power for
ability to cause a biological response indicative of a particular mechanism of
action. We use the H4IIE rat
hepatoma bioassay to screen for CYP1A-mediated EROD induction by sediment
extracts, and the yeast estrogen screen (YES assay) to assess potential of
environmental samples to activate the human estrogen receptor. We have used these methods to screen
samples collected along the Mississippi Gulf Coast following Hurricane Katrina.
Funded Research Projects:
"Roles of CYP1 & CYP19 in Fundulus Steroid and PAH metabolism" NIH R01 7/1/04-4/30/09 PI
"Biosensors" NOAA 10/04-10/08 CoPI with M. Slattery
"Screening of
Environmental Contaminants Detected in Mississippi Sediments as Inducers and/or
Inhibitors of CYP1B1 Expression in Channel Catfish." Mississippi Water
Resources Research Institute.
3/1/01-2/29/04 PI
ÒModulation of CYP1B1 gene
expression in human cancer cell lines.Ó AACP New Investigators Program. 12/1/02
Ð 11/30/03. PI.
ÒFlavonoid-mediated gene
expression in human cancer cells.Ó Mississippi Functional Genomics Network SGO.
11/01/03 Ð 10/31/04. PI.
ÒChemical-induced changes in promoter methylation in Japanese medaka -
Environmental Toxicology Congressional Initiative Environmental Signals and SensorsÓ 09/00 Ð 09/02 Co-investigator with M. Slattery, C. Foran, M. Haasch.
ÒCharacterization of
bioassays and chemical contaminants in croaker, oyster and sediments collected
at two sites in the Mobile Bay National EstuaryÓ Mobile Bay National Estuary
Program, 08/01 Ð 08/02 Co-PI with C. Foran.
"Characterization of CYP1B1 gene activation in fish for use as a possible marker of cancer resistance." North Carolina Biotechnology Center. 07/00 Ð 07/02. Co-PI with R. Di Giulio.
Kristine L. Willett
Department of Pharmacology
The University of Mississippi