SCIENTIFIC REPORT 2004 - Sylvester Comprehensive Cancer Center

T U M O R C E L L B I O L O G Y P R O G R A M
Dr. Werner’s laboratory also is pursuing the
investigation of Ini, a novel transcription factor
that is involved in connexin43 gene regulation at
the transcriptional level. Knockout experiments
in Saccharomyces pombe indicated that the yeast
homolog of Ini is an essential protein. It appears
to be involved in the mRNA splicing process.
SELECTED PUBLICATIONS
2003
Oltra, E, Pfeifer, I, and Werner, R. Ini, a small
nuclear protein that enhances the response of the
connexin43 gene to estrogen. Endocrinology
144:3148-58, 2003.
HIGHLIGHTS/DISCOVERIES
• Demonstrated that, in humans, connexin43 is
expressed in the heart and the uterus, as well as
in many other tissues. Because it is an essential
protein (as determined in mice) that affects
early development, it is important to understand
the mechanisms of its regulation of expression.
In the uterus, connexin43 expression
is inducible by estrogen. This regulation is clinically
important because women who suffer
from premature labor also express connexins
prematurely.
JAMES WYCHE, PH.D.
Professor of Biology
DESCRIPTION OF RESEARCH
One of Dr. Wyche’s interests has been to understand
how anti-cancer drugs induce
apoptosis (cell deaths) of cancer cells. Recently,
he and his colleagues studied how the natural
product camptothecin (CPT) and its semi-synthetic
derivatives such as CPT-11, 9-amino-CPT
(9AC), and 9-nitro-CPT (9NC) induce apoptosis
of human colon cancer cells. Many aspects of the
mechanism by which these drugs exert their
death effect on cancer cells, however, remain
largely unknown. In recent years, Dr. Wyche and
his colleagues have used a cell model of human
colon cancer to demonstrate that treatment with
low doses of CPT induces senescence in the presence
of a protein call p21. Apoptosis, however,
occurs in the absence of p21. Therefore, p21 is a
key determinant of the outcome of colon cancer
cells treated with CPT drugs at doses that are relevant
to clinical application. Thus, CPT treatment
of colon cancer cells with p21 should result
in disease stabilization, whereas CPT treatment
of p21-deficient colon cancer cells should result
in rapid apoptosis and disease regression.
It is well established that p21 inhibits cyclindependent
kinases (Cdks) and several other factors,
including proliferating cell nuclear antigens.
They hypothesize that inhibition of Cdks by p21
is essential to inhibit apoptosis and induce senescence.
In this context, Dr. Wyche and his colleagues
propose that a protein named E2F1 is
essential for apoptosis of colon cancer cells
treated with CPT. According to this hypothesis,
inhibition of Cdks should result in activation of
another protein, named retinoblastoma (Rb),
which in turn, inhibits E2F1 and consequentially
E2F1-dependant apoptosis. They also hypothesize
that the ability of p21 to induce senescence
requires a protein called STAT1. To test their
hypothesis, Dr. Wyche’s laboratory currently is
using techniques to selectively alter the status of
Cdk, E2F1, Rb, and STAT1 genes in human
colon cancer cells. They will then investigate the
role of each protein in the process of apoptosis
and senescence in the colon cancer cells after
CPT treatment.
The information obtained from these investigations
will provide a better insight into the
molecular pathways activated in colon cancer
cells after CPT treatment and eventually will lead
to specific experimental designs to completely
understand how CPTs affect colon cancer.
UM/Sylvester Comprehensive Cancer Center Scientific Report 2004 99