Mechanisms of thymidine phosphorylase angiogenesis

Project: Research project

Project Details


DESCRIPTION provided by applicant): There is an increasing appreciation of the
role of angiogenesis in the growth and metastasis of solid tumors, and data
suggest that antiangiogenesis therapy could be a viable approach to treatment
of advanced disease. Thymidine phosphorylase (TP) has been recently found to be
an angiogenic factor, an observation that was based on its identity to a
previously described angiogenic factor, platelet-derived endothelial cell
growth factor (PD-ECGF). TP is expressed at high levels in many human solid
tumors including colorectal cancers, and the level of its expression has been
correlated in numerous clinical studies, including one we conducted, with
neovascularization, tumor aggressiveness, and poor patient prognosis.
Immunohistochemical evaluation of TP by us and others has demonstrated that
elevated TP expression in many, but not all, colon tumors occurs mainly in
tumor-associated macrophages (TAMs), rather than in the tumor cells. We have
found that a human monocytic cell line (THP1) expressed a higher level of TP
than human colon carcinoma cell lines. We also found that TNF-alpha stimulated
TP expression in THP1 cells and in WiDr colon carcinoma cells, and we will use
these two cell lines as well as primary cultures of TAMs to determine the
molecular basis for the regulation of TP expression (i.e. transcriptional,
post-transcriptional). TP's angiogenic activity appears to be dependent on its
catalytic activity, with 2-D-deoxyribose (2dR) serving as the putative mediator
of endothelial cell activation. We have established an in vitro model in which
human cancer cells or monocytes can be co-cultured with normal human
endothelial cells (HUVEC), and can induce their migration in a TP-dependent
manner. We will use this model to begin to determine the mechanisms by which TP
stimulates HUVEC and human microvascular endothelial cell (HMEC) migration,
using analogs of thymidine and 2dR we will synthesize to test the hypothesis
that migration is solely related to 2dR formation, and by using a TP inhibitor
we have made and a neutralizing TP antibody to test the hypothesis that TP's
intracellular actions are sufficient to stimulate HUVEC migration. Little
further is known of the mechanism of action of TP. Our studies showing
differences in the specific integrins which mediate TP vs. VEGF-induced HUVEC
migration are the first to explore the cellular actions of TP on endothelial
cells. We have also found that TP induces tyrosine phosphorylation of FAK
(focal adhesion kinase), a protein that plays a central role in cell
attachment, migration, and signaling. We will continue our studies to define
the integrin-associated signal transduction pathways that are activated by TP
in HUVEC and HMEC, testing the hypothesis that these differ initially from
those occurring in response to angiogenic factors such as VEGF and bFGF, which
have clearly defined cell-surface receptors. In addition to providing a basic
understanding of the mechanisms of angiogenic action of TP colon cancers, these
studies could provide insights to optimize the use of current and future
anti-angiogenic agents which target integrins.
Effective start/end date6/1/014/30/12


  • Cancer Research
  • Genetics
  • Medicine(all)
  • Oncology


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