tumor cell biology program - Sylvester Comprehensive Cancer Center

fined at the molecular level by interfering
with upstream components of the IL-
6 receptor pathway, namely the ras and
Stat pathways.
PUBLICATIONS
Zang ,J, Scordi, I, Smyth, MJ and
Lichtenheld, MG. Interleukin 2 receptor
signaling regulates the perforin gene
through signal transducer and activator
of transcription Stat5 activation of two
enhancers. Journal of Experimental
Medicine 190:1297, 1999.
Lichtenheld, MG. Control of
perforin gene expression: A paradigm for
understanding cytotoxic lymphocytes?
Cytotoxic Cells: Basic Mechanisms and
Medical Applications, ed. M.V. Sitkovsky
and P.A. Henkart. (Philadelphia:
Lippincott Williams & Wilkins) pp.123-
145, 1999.
Malek, TR, Yu, A, Scibelli, P,
Lichtenheld, MG and Codias, EK.
Broad programming by IL-2 receptor signaling
for extended growth to multiple
cytokines and functional maturation of
antigen-activated T cells. Journal of Immunology
166:1675, 2001.
HIGHLIGHTS/DISCOVERIES
• Dr. Lichtenheld’s laboratory has identified
two essential enhancers of the
perforin gene, demonstrating that they
are under the control of Stat5 molecules.
This work, which has shed molecular
light on fundamental principles
of effector gene activation in cytotoxic
lymphocytes, was published in a prestigious
journal.
Diana M. Lopez, Ph.D.
Professor of Microbiology
and Immunology
DESCRIPTION OF RESEARCH
During mammary tumorigenesis,
a profound dysregulation of cytokine
production by various lymphoreticular
cells has been documented.
B lymphocytes from tumor bearers are
cytotoxic against tumor targets and have
an increased production of tumor necrosis
factor (TNF-α). A greater stability of
TNFα- RNA and a decreased rate of this
cytokine RNA degradation was observed
in tumor bearers’ B cells compared to
those of normal mice. The TNF-α promoter
contains regions that bind NF-B,
which regulate the rate of transcription.
Supershift assays for the NF-B region
showed that there are p50-p65
heterodimers and p50 homodimers in
the nuclear extracts of the two types of B
cells, while those from tumor bearers lack
the c-Rel component that is present in
normal B cells. These results indicate that
abnormalities in binding and composition
of the NF-B complexes may be
involved in the increased TNF-α production
by tumor bearers’ B cells.
Recently, it has been found that lymphocytes
from tumor-bearing mice have
elevated levels of interleukin 6 (IL-6) at
the transcriptional and translational levels,
that are reflected systemically. The
mammary tumor used in these studies
constitutively produces several factors
including granulocyte-macrophage
colony stimulating factor (GM-CSF),
prostaglandin E 2
(PGE 2
) and phosphatidyl
serine (PS), which directly or indirectly
can affect the cells of the immune
system. In vitro addition of GM-CSF
resulted in a dramatic increase in IL-6
levels from B cells from normal mice.
This effect does not appear to be due to
elevated levels of TNF-α, known to
upregulate IL-6. Rather, GM-CSF activates
IL-6 production independently of
TNF-α as demonstrated by neutralization
studies using anti-TNF-α antibodies.
Furthermore, the effect exerted by
GM-CSF on IL-6 production by B lymphocytes
appears to be direct, since pretreatment
of cultures with anti-GM-CSF
completely abrogated the elevated production
of IL-6. The elevated levels of
IL-6 and TNF-α in tumor bearers may
contribute to the cachectic state observed
in tumor bearing mice.
Dr. Lopez’s laboratory has previously
reported that mice implanted with mammary
tumors show a progressive thymic
involution which parallels the growth of
the tumor. The involution is associated
with a severe depletion of CD4 + 8 + thymocytes.
In collaboration with Dr.
Rebecca Adkins, three possible mechanisms
leading to this thymic atrophy have
been investigated: 1) increased apoptosis,
2) decreased proliferation, or 3) disruption
of normal thymic maturation. The
levels of thymic apoptosis were determined
by propidium iodide and Annexin
V staining. A statistically significant, but
minor, increase in thymic apoptosis of
tumor-bearing mice was detected with
propidium iodide and Annexin V staining.
The levels of proliferation were assessed
by in vivo labeling with BudR. The
percentages of total thymocytes labeled
one day following BudR injection were
similar in control and tumor-bearing
mice. Moreover, the percentages of CD4 -
8 - thymocytes that incorporated BudR
during a short-term pulse (five hour) of
BudR were similar. Lastly, thymic maturation
was evaluated by examining CD44
and CD25 expression among CD4 - 8 -
thymocytes. The percentage of CD44 +
cells increased while the percentage of
CD25 + cells decreased among CD4 - 8 -
thymocytes from tumor-bearing versus
control animals. Together, these findings
suggest that the thymic hypocellularity
seen in mammary tumor bearers is not
due to a decreased level of proliferation,
but to an arrest at an early stage of thymic
differentiation along with a moderate
increase in apoptosis.
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UM/Sylvester Comprehensive Cancer Center Scientific Report 2002