CHARACTERIZATION OF BREAST TISSUE IN EARLY PREGNANCY
TO HELP DEFINE THE EFFECT OF INDUCED ABORTION ON
BREAST CANCER RISK
DeShawn Taylor, M.D.
A Thesis Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
CLINICAL AND BIOMEDICAL INVESTIGATIONS
Copyright 2007 DeShawn Taylor, M.D.
Prospective studies show that pregnancies interrupted by induced abortion may provide as much as 70% of the breast cancer protection provided by a term pregnancy. Estrogen (E) and progesterone (P4), acting through estrogen receptor alpha (ER-A) and progesterone receptor (PR) isoforms A and B, are mitogenic to breast epithelium but their increased levels early in pregnancy may lead to differentiation of the epithelium and hence to a decreased breast cancer risk. We have begun to investigate the actions of E and P4 in early pregnancy by determining PR-A, PR-B, ER-A and MIB1 in the breast epithelium immediately after an induced abortion. PR-A was significantly decreased compared to non-pregnant premenopausal controls and decreased with gestational age. PR-B, ER-A and MIB1 expression were increased compared to controls, but did not correlate with gestational age. Future studies will investigate the consequences of such a profound change in PR expression on the breast.