Haematologica 2003 - Supplements

P6.3
ENDOTHELIAL CELL-TUMOR CELL INTERACTIONS IN
MULTIPLE MYELOMA.
Ivan Van Riet 1 , Isabelle Vande Broek 1 , Kewal Asosingh 1 ,
Els Van Valckenborgh 1 , Liesbeth Hellebaut 1 , Xavier Leleu 2 ,
Thierry Facon 2 , Ben Van Camp 1 and Karin Vanderkerken 1
1
Department of Hematology and Immunology, Vrije Universiteit
Brussel (VUB), Brussels, Belgium; 2 Department of Hematology,
Hopital Huriez, Lille, France.
Endothelial cells (EC) represent, within the tumormicroenvironment,
important interactive partners for multiple
myeloma (MM) cells, since they are involved in different aspects
of the paracrine network that underlies the pathogenesis of MM.
Myeloma cells interact with bone marrow EC (BM-EC) during
extravasation/homing and can directly activate EC resulting in
neovascularization. Using the in vivo 5T2MM-mouse model our
group previously demonstrated that the specific localization of
myeloma cells in the bone marrow (BM) is a result of the
combination of both a selective entry/adhesion and a selective
survival/growth of the tumor cells in the BM (1). In the same
murine model the selective entry in BM could be associated with
a selective adhesion to BM-EC, involving CD44v10 (1, 2). After
adhesion to BM-EC, myeloma cells will receive chemotactic
signals that will stimulate their migration to the extravascular
(medullar) compartment. We could demonstrate that the
migration of both human and murine MM cells could be triggered
by laminin-1 and MCP-1 (both produced by BM stromal cells,
including EC). These migratory responses are mediated by the
67kD laminin-receptor (LR) and the CCR-2 chemokine-receptor,
respectively (3, 4, 5). It was also found that 67kD LR can be upregulated
in MM cells after contact with BM-EC and that this
receptor is also involved in the bone marrow homing of 5T2MM
cells in vivo (3). In order to cross bone marrow endothelium, MM
cells also need to degrade the basement membrane. Using
Matrigel ® invasion assays, we could demonstrate that human
isolated (CD138 positive) MM cells are indeed invasive and that
this invasive capacity could be enhanced by the presence of BM-
EC. Moreover we found that the transendothelial invasion of MM
cells involves MMP-9. In the 5T33MM model we could
demonstrate an in vivo, bone marrow microenvironmentdependent,
transcriptional upregulation of MMP-9 in the MM
cells (6). In vitro experiments demonstrated that the production of
this protease could be up-regulated in both murine (5T33MM)
and human (CD138 positive) MM cells by interaction with BM-
EC (6, 7). In human MM cells, this BM-EC-mediated upregulation
of MMP-9 seems to involve hepatocyte growth factor
(7).
After extravasation, MM cells continue to interact with BM-EC,
directly contributing to the formation of new blood vessels. We
could demonstrate/confirm that murine (5T33MM) and human
MM cells have angiogeneic-inducing potential and express
different pro-angiogenic factors including VEGF-A, b-FGF
and/or angiopoietin-1(8, 9). Moreover we found that the
expression of some of these factors (VEGF and bFGF) in human
MM cells is regulated by the BM-stroma. Comparing the
functional activity of human MM-cell derived VEGF-A and
bFGF in the in vitro proliferation and migration of EC, we found
that VEGF plays a major but not exclusive role (9). Most recently
we 3found that both human and murine MM cells also express
transcripts for platelet-derived growth factor PDGF (A, B, C and
D). This factor induces angiogeneic responses similar to VEGF,
through interaction with receptor tyrosine kinases (RTK). We are
currently investigating in the in vivo 5T33MM-mouse model the
effect of a new potent RTK inhibitor, i.e. SU11657, that blocks
the receptors for VEGF and PDGF.
In conclusion, EC are involved in different aspects of tumor-host
communication in MM and may therefore also represent, as
important component of the stromal cell population, an
interesting target for new therapeutical approaches. Future
efforts, including the use of microarray analysis, should further
clarify the molecular background of these MM cell-EC
interactions
K. Vanderkerken et al., Brit. J. Cancer, 82, 953-959, 2000.
K. Asosingh et al., Cancer Research, 61, 2862-2865, 2001.
I. Vande Broek et al., Brit. J. Cancer, 85, 1387-1395, 2001.
K. Vanderkerken et al., Clin Exp Metastasis.;19, 87-90, 2002.
I. Vande Broek et al., Brit. J. Cancer, in press, 2003.
E. Van Valckenborgh et al., Int J Cancer. 101:512-8, 2002.
I. Vande Broek et al., Blood, 100, 209a, 2002.
E. Van Valckenborgh et al.,. Brit J Cancer, 86, 796-802, 2002.
L. Hellebaut et al., submitted, 2003.
P6.4
ANGIOGENIC ENDOTHELIAL CELLS WITHIN THE
BONE MARROW OF MULTIPLE MYELOMA. A
PHENOTYPIC AND FUNCTIONAL ASSESSMENT
Angelo Vacca, Roberto Ria, Domenico Ribatti, Fabrizio
Semeraro,Francesca Merchionne, Franco Dammacco
Department of Biomedical Sciences and Human Oncology, Section
of Internal Medicine and Clinical Oncology, and Department of
Human Anatomy and Histology, University of Bari Medical School,
I-70124 Bari, Italy
Endothelial cells of tumor vessels greatly differ from those of
quiescent normal vessels due to their rapid proliferation which
reflects enhanced angiogenesis associated with tumor progression
(growth, invasion, metastasis) (1). They also differ in the profile
and level of cell adhesion molecules because attachment to one
another and to extracellular matrix during sprouting (that implies
cell proliferation and migration) is remarkably reduced. Their
survival is largely dependent on growth factors secreted by the
tumor and its microenvironment (cells and matrix), and on their
expression of specific receptors for these factors. Moreover, they
are abnormal in shape and highly permeable due to fenestrae,
vesicles, transcellular holes, widened intercellular junctions, a
discontinuous basement membrane and scarce accessory
stabilizing cells such as pericytes. They share the lining of new
vessels with tumor cells able to mimic vessels. The fast growth of
endothelial and tumor cells coupled with structural and functional
abnormalities of endothelial cells make tumor vessels tortuous
and dilated, with uneven diameter, excessive branching and
shunts. Thus, tumor blood flow is chaotic and variable, and leads
to hypoxic and acidic regions in the tumor that stimulate further
angiogenesis.
Bone marrow angiogenesis is mandatory for progression of
multiple myeloma (MM) (2, 3), and is characterized by thin,
tortuous and arborised vessels, and single or clustered endothelial
cells (2). This process is sustained by vascular endothelial growth
factor (VEGF) (4), basic fibroblast growth factor (bFGF), and
matrix metalloproteinases (MMPs) (2) secreted by plasma cells.
Besides their morphological picture, information on phenotype,
function and structure of endothelial cells is circumstantial (2). In
this presentation bone marrow endothelial cells of active MM are
compared to normal quiescent endothelial cells in an attempt to
add further information to the issue.
Endothelial cells were extracted from bone marrow of 57
patients, and compared for the antigenic and genetic phenotype,
functions and ultrastructural morphology with their normal
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