Current Research Interests
Defining early events in breast cancer
A bench to bedside program of breast cancer risk and prevention.
Identifying novel molecular targets for prevention
As described above we are currently investigating signal transduction pathways that target the elimination of damaged mammary epithelial cells in order to define
1) novel targets of breast cancer risk and
2) biologic markers of response to targeted-prevention agents.
In our in vitro models we identified a critical role for the CREB-binding protein, CBP in regulating both rECM- and tamoxifen-induced apoptosis in damaged mammary epithelial cells. CBP is a tightly regulated transcription factor that is 1) critical for normal growth regulation and apoptosis, 2) serves to integrate diverse signaling pathways including retinoids, estrogen, prostaglandins, and p53, and 3) is thought to participate in BRCA1-mediated DNA repair. Recently we demonstrated that all-trans-retinoic acid and RARb2 induce expression of CBP through a consensus RARE in the 5’ upstream promoter region of CBP. This is an important finding because it suggests that RARb2 and CBP can function in a positive-feedback loop that promotes mammary gland homeostasis.
In our in vitro models of mammary carcinogenesis, we observe that CBP 1) regulates mammary epithelial cell proliferation and polarity in three-dimensional rECM culture and 2) is critical for tamoxifen-sensitivity. Suppression of CBP in HMECs results blocks both rECM- and tamoxifen-mediated apoptosis in acutely damaged mammary epithelial cells. Chromatin immunoprecipitation (ChIP) and differential gene expression studies demonstrate that tamoxifen and rECM exhibit cross-talk through recruitment of CBP to the promoter of specific target genes that are known to regulate both mammary involution and apoptosis. Suppression of RARb2 P2 function promotes loss of CBP expression and resistance to both rECM- and tamoxifen-induced apoptosis. These observations provide a rational for utilizing loss of RARb2 function as a global marker of breast cancer risk.
Developing a translational breast cancer prevention cohort: We developed a multi-institutional breast cancer prevention cohort to insure that observations made in our laboratory are directly translated to benefit women at high-risk for breast cancer. Subjects were drawn from three well-established high-risk chemoprevention cohorts
1) Duke University: 456 patients (Director, Victoria Seewaldt) and 2) University of Kansas: 680 patients (Director, Carol Fabian), and 3) Ohio State University: 370 patients (Director, Lisa Yee).
Women must had have at least one of the following major risk factors to be eligible:
1) 5 year Gail risk calculation > 1.7%,
2) prior biopsy exhibiting atypical hyperplasia, LCIS, DCIS, or
3) known BRCA1/2 mutation.
Our goal is to use the clinic to generate multi-disciplinary research collaborations to
1) investigate genetic modifiers of breast cancer risk and
2) develop interventions ranging from pharmacologic agents to stress reduction. Participating faculty span multiple disciplines including genetics, immune modulation, basic mammary biology, nutrition, complementary and alternative medicine, and medicinal chemistry. Research activity in this clinic directly intersects with several major research initiatives including the Breast SPORE and the Cancer Genetics Network.
Developing Markers of Short-Term Breast Cancer Risk:
Loss of RARb2 function in mammary epithelial cells is hypothesized to be the result of both genetic and epigenetic events. Two mechanisms have been proposed: 1) loss of heterozygosity (LOH) and 2) promoter methylation. LOH at the RARb2 loci (3p24) is thought to be a late mechanism for loss of RARb2 expression. In contrast, we and others have observed that methylation of the RARb2 P2 promoter methylation is an early mechanism for RARb2 loss.
Periareolar Random Breast Fine-Needle Aspiration (RPFNA) is a research technique developed to repeatedly sample mammary cells from the whole breast of asymptomatic high-risk women in order to assess
1) short-term breast cancer risk and
2) response to chemoprevention1,2.
RPFNA is distinct from diagnostic FNA as
1) diagnostic FNA is a standard clinical technique used to evaluate a symptomatic breast mass and
2) breast rpFNA is analogous to a cervical pap-smear in its ability to obtain a representative sampling of cells from the entire breast. We tested an initial 55 women from our breast cancer prevention cohort and 20 women with known breast cancer for the presence of RARb2 P2 methylation by rpFNA. The Masood Cytology Index was used to stratify rpFNA specimens for the degree cytologic abnormalities. We observed RARb2 P2 methylation in 0% normal cells and cells with mild mammary hyperplasia (Masood scores of 10 and 11-12, respectively), 20% of cells with severe mammary hyperplasia (Masood score of 13), 60% of cells with atypia (Masood score of 14-16) and in 80% of cells with severe abnormalities or breast cancer (Masood score 17-19). Currently we are testing whether the presence of RARb2 P2 methylation in RPFNA is a short-term predictor of breast cancer risk.
