Lymphangiogenesis and Kaposi's Sarcoma VEGF-C
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Angiogenesis (blood vessel growth), lymphangiogenesis (lymph system growth) are all intrinsically connected with lymphedema and share many of the same genes. We have several pages on both processes.
May 23, 2008
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Journal
of Investigative Dermatology 113,
1047-1053 (1999)
© 1999 The
Society for
Investigative Dermatology
Cutaneous
Biology Research Center, Department of Dermatology,
Massachusetts General Hospital and Harvard Medical School, Charlestown,
Massachusetts, U.S.A.; * Department of
Pathology and
Division of Experimental Medicine and Hematology/Oncology, Beth Israel
Deaconess
Medical Center, Boston, Massachusetts, U.S.A.;
Haartman Institute, University of Helsinki, Finland
Reprint requests to: Dr. Michael Detmar, CBRC/Department of Dermatology, Massachusetts General Hospital, Building 149, 13th Street, Charlestown, MA 02129, U.S.A. Email: michael.detmar@cbrc2.mgh. harvard.edu
Kaposi’s sarcoma is characterized by clusters of spindle-shaped cells that are considered to be tumor cells and by prominent vasculature. Whereas spindle cells are most likely endothelial in origin, it remains controversial whether they are of lymphatic or blood vascular derivation. To test the hypothesis that the lymphangiogenesis factor vascular endothelial growth factor-C and its receptors, KDR and flt-4, are involved in the pathogenesis of Kaposi’s sarcoma, we performed in situ hybridizations and immunofluorescent stainings on human immunodeficiency virus-associated Kaposi’s sarcoma. Spindle-shaped tumor cells strongly expressed KDR and flt-4 mRNA. Immunofluorescent staining confirmed expression of the flt-4 receptor in Kaposi’s sarcoma cells, and double labeling revealed its colocalization with the endothelial cell marker CD31. Vascular endothelial growth factor-C was strongly expressed in blood vessels associated with Kaposi’s sarcoma. In vitro, human dermal microvascular endothelial cells also expressed vascular endothelial growth factor-C mRNA that was further upregulated by vascular permeability factor/vascular endothelial growth factor. Vascular endothelial growth factor-C potently stimulated the proliferation of Kaposi’s sarcoma tumor cells in vitro. These results demonstrate important paracrine functions of vascular endothelial growth factor-C, produced by blood vessels, in the pathogenesis of cutaneous Kaposi’s sarcoma, and suggest a lymphatic origin and/or differentiation of Kaposi’s sarcoma tumor cells.
Key Words: angiogenesis • HIV • lymphatics • VEGF.
Abbreviations: HDMEC, human dermal microvascular endothelial cells ISH, in situ hybridization KS, Kaposi’s sarcoma VEGF-C, vascular endothelial growth factor-C
Introduction
Kaposi’s sarcoma (KS) is the most common tumor associated with AIDS,
frequently arising in the skin and mucosal surfaces (Enzinger &
Weiss 1995;
Regezi et al. 1993). Histologically, KS lesions are composed of
clusters of
spindle-shaped tumor cells, blood vessels, fibroblasts, dendrocytes,
and
inflammatory cells (Enzinger & Weiss 1995; Naidu et al. 1994).
The principal
features of AIDS-KS include hyperproliferation of spindle cells,
prominent
angiogenesis, increased vascular permeability, edema, and extravasation
of
erythrocytes (Roth et al. 1992; Sturzl et al. 1992).
The etiology of KS is still a subject of dispute. Whereas spindle cells
are most
likely endothelial in origin, it remains controversial whether they are
of
lymphatic or blood vascular derivation. Already in 1902 it was proposed
that the
vascular slits comprising the lesions are morphologically consistent
with
lymphatics, based on the spindle shape of their lining cells, their
tenuous
basement membrane, and the scarcity of red blood cells in their
vascular lumen (Philippson
1902; Pelagatti 1905). Subsequent ultrastructural and
immunohistochemical
evidence largely supported the view that the KS tumor cells more
closely
resemble lymphatic than blood vascular endothelium (Beckstead et al.
1985;
Dorfman 1962; Dictor 1986; Witte et al. 1990). Further patterns
suggestive of a
lymphatic derivation of KS are the unique distribution of cutaneous
lesions
along the lines of lymphatics, their arrangement around blood vessels,
and the
absence of lesions in organs that are devoid of lymphatics (Dorfman
1988).
It has been recently proposed that angiogenesis and vascular
permeability play a
central part in the development of KS, strongly suggesting a role for
vascular
permeability factor/vascular endothelial growth factor (VPF/VEGF) in
its
pathogenesis. VPF/VEGF stimulates endothelial cell growth in vitro
(Detmar et
al. 1995) and induces angiogenesis in vivo (Oh et al. 1997), acting
through two
tyrosine kinase receptors that are predominantly found on vascular
endothelial
cells: flt-1 (VEGFR-1) and KDR (VEGFR-2) (Neufeld et al. 1999).
Previously, we
reported strong expression of KDR mRNA in KS tumor cells as well as in
endothelial cells of small vessels within and surrounding the tumor;
however, we
did not detect significant expression of the VEGF receptor flt-1 in
spindle-shaped tumor cells (Brown et al. 1996). These findings have
been
confirmed by others, suggesting an important function for KDR in the
development
of KS (Cornali et al. 1996; Masood et al. 1997). It has remained
controversial,
however, whether VPF/VEGF itself is expressed in KS tumor cells.
Expression of
VPF/VEGF has been reported in KS cell lines in vitro and in vivo
(Weindel et al.
1992; Cornali et al. 1996; Masood et al. 1997; Nakamura et al. 1997).
Anti-sense
oligonucleotides to VPF/VEGF inhibited the growth of KS cells in vitro;
however,
addition of VPF/VEGF did not result in increased proliferation of KS
cells (Cornali
et al. 1996; Masood et al. 1997). Moreover, we previously found
VPF/VEGF
predominantly expressed by epidermal keratinocytes overlying KS tumors
and, at
lower levels, by infiltrating inflammatory cells, but only weakly by KS
cells
(Brown et al. 1996). The strong expression of KDR, but only weak
expression of
VPF/VEGF suggested that some other ligand(s) of KDR might be involved
in the
pathogenesis of KS.
Recently, VEGF-C has been identified as a new member of the VEGF family
of
growth factors (Joukov et al. 1996; Lee et al. 1996). Like VPF/VEGF,
VEGF-C
binds to KDR; however, it does not bind to the VPF/VEGF receptor flt-1
(Joukov
et al. 1996). VEGF-C also activates the receptor tyrosine kinase flt-4
(VEGFR-3), that has been regarded as a specific marker for lymphatic
endothelium
(Kaipainen et al. 1995; Joukov et al. 1996). Expression of flt-4 was
very
recently reported in KS cells (Liu et al. 1997; Jussila et al. 1998).
VEGF-C
elicits a lymphangiogenic response in the chicken embryo
chorioallantoic
membrane (CAM), and transgenic mice overexpressing VEGF-C in the skin
are
characterized by specific hyperplasia of the lymphatic network,
revealing VEGF-C
as the first known growth factor for lymphatic endothelium (Jeltsch et
al. 1997;
Oh et al. 1997).
In this study we examined the expression of VEGF-C, VPF/VEGF and their
receptors
in AIDS-associated KS, and characterized the effects of VEGF-C on KS
tumor
cells, in order to test the hypothesis that the lymphangiogenesis
factor VEGF-C
and its receptors are involved in the pathogenesis of KS.
MATERIALS and METHODS
In situ hybridization (ISH)
A VEGF-C cDNA fragment comprising nt 827–1634 of the full length human
VEGF-C
cDNA (Joukov et al. 1996; Lee et al. 1996) (GenBank accession no.
X94216) was
subcloned into the pGEM-3Z vector (Promega, Madison, WI). Following
restriction
digestion with AccI and ClaI, a 808 bp fragment was gel purified and
ligated
into the AccI site of the pGEM-3Z vector. The sequence was verified by
restriction mapping and by direct sequencing using the Sanger dideoxy
method.
For generation of anti-sense and sense probes, the construct was
linearized with
BamHI or HindIII and transcribed from the SP6or T7promoter,
respectively. The
human flt-4 cDNA used for generation of ISH probes comprised nt 55–207
of the
full length flt-4 cDNA, and has been published previously (Aprelikova
et al.
1992; Pajusola et al. 1992). 35S-labeled single-stranded anti-sense and
sense
RNA probes for the VPF/VEGF receptors KDR and flt-1 have been described
previously (Detmar et al. 1994). The probe for human VPF/VEGF
hybridizes with a
region of VPF/VEGF mRNA common to all known VPF/VEGF splice variants
(Brown et
al. 1992).
ISH was performed on 4 µm-thick sections of paraffin-embedded tissue as
described in detail previously (Brown et al. 1996). Six cases of
AIDS-associated
cutaneous KS were studied. Four millimeter punch biopsies of cutaneous
KS
lesions were obtained with informed consent from HIV-positive KS
patients
following human experimental guidelines of the US Department of Health
and Human
Services and the Beth Israel Deaconess Medical Center. For
autoradiography,
slides were coated with NTB2 film emulsion and exposed for 2 wk. The
slides were
developed and counterstained with hematoxylin. Specimens were viewed
using a
Nikon E-600 microscope (Nikon, Melville, NY).
Indirect immunofluorescence
Human tissues obtained after surgical removal were immediately frozen
in liquid
nitrogen, sectioned (6 µm), stored at - 70°C, and used for
immunofluorescence.
Cryosections were fixed and stained as previously described (Skobe et
al. 1997),
using antibodies against human CD31 (dilution 1/30; Pharmingen, San
Diego, CA),
human flt-4 (1.1 µg per ml) (Jussila et al. 1998) or anti-serum against
human
VEGF-C (cl.882/5; dilution 1/100) (Joukov et al. 1997). The secondary
antibodies, labeled with either Texas Red or fluorescein isothiocyanate
(Jackson
ImmunoResearch Lab., West Grove, PA) were used at 30 µg per ml.
Specimens were
mounted in Mowiol (Calbiochem, La Jolla, CA) and examined by confocal
imaging
using a Leica DM IRBE microscope and a Leica TCS 4D confocal system.
Kaposi’s sarcoma cell growth assays
The human KS cell line KS59, derived from a cutaneous biopsy of an AIDS
patient,
has been previously shown to express the flt-4 receptor that was
phosphorylated
after treatment with VEGF-C (Liu et al. 1997). Cells were plated in
triplicate
in collagen-coated 24 well plates at a density of 2 x 103 cells per
well in
complete medium containing 15% fetal bovine serum (FBS) (Liu et al.
1997). Cells
were allowed to attach overnight, washed 3 x with serum-free medium,
and were
cultured in medium containing 0.5% FBS and 1–100 ng per ml recombinant
human
VEGF-C (Joukov et al. 1997). Medium and VEGF-C were replaced after 2 d.
After 4
d of treatment, cells were trypsinized and counted using a Coulter
Counter. The
experiment was repeated twice with comparable results. The unpaired t
test was
used for statistical analysis of the results.
Growth factor stimulation of endothelial cells and northern
blot analysisHuman
dermal microvascular endothelial cells (HDMEC) were isolated from
neonatal
foreskins as described (Richard et al. 1998) and were used between
passage 4 and
6. HDMEC were cultured in endothelial cell basal medium (Clonetics, San
Diego,
CA), supplemented with 1 µg per ml hydrocortisone acetate, 5 x 10- 5 M
N-6,2'-O-dibutyryl-adenosine 3',5'-cyclic monophosphate (Sigma, St.
Louis, MO),
20% heat-inactivated FBS, 100 U per ml penicillin, and 100 µg per ml
streptomycin, on collagen-coated tissue culture dishes (Richard et al.
1998)
until the cells reached 80% confluency. Cultures were then switched to
2% FBS
for 2 h and were treated with growth factors (0.1–100 ng per ml) for 48
h.
Recombinant human VPF/VEGF165, platelet-derived growth factor
(PDGF)-AA, PDGF-BB,
basic fibroblast growth factor, placenta growth factor (PCGF) and tumor
necrosis
factor (TNF)- were all purchased from R&D (Minneapolis, MN).
Total cellular
RNA was isolated using the RNeasy kit (Qiagen, Valencia, CA) according
to the
manufacturer’s instructions. The isolated RNA was subjected to
electrophoresis
and transferred to Hybond-N + nylon supported membranes (Amersham,
Arlington
Heights, IL). 32P-radiolabeled DNA probes were labeled by the random
priming
method (Multiprime Labeling Kit, Amersham). We used a fragment
containing nt
581–1634 of human VEGF-C cDNA (Joukov et al. 1996; Lee et al. 1996)
(GenBank
accession no. X94216). A human ß-actin cDNA probe (Clontech, Palo Alto,
CA) was
used as the control for equal RNA loading. Blots were hybridized at
65°C for 24
h, washed at high stringency and exposed to X-OMAT MR film (Kodak,
Rochester,
NY). All experiments were repeated twice.
Endothelial cell proliferation assays
Proliferation assays were performed as described (Detmar et al. 1995).
Briefly,
HDMEC were seeded at 1 x 104 cells per well into collagen-coated
24-well tissue
culture clusters in complete endothelial cell basal medium supplemented
with 20%
FBS. The following day, at approximately 30–40% confluency, cultures
were
switched to 2% FBS for 24 h. HDMEC were then incubated with various
concentrations of VEGF-C (0.3–30 ng per ml) and/or VPF/VEGF (0.4 ng per
ml)
for 96 h. Medium and growth factors were replaced after 48 h.
[3H]thymidine was
added to the cultures 6 h before harvesting (1 µCi per ml) (DuPont NEN,
Boston,
MA) and incorporated radioactivity was determined as described (Detmar
et al.
1989). All experiments were performed in triplicate, and were repeated
twice.
The unpaired t test was used for statistical analysis of the results.
Results
Expression of VEGF-C, VPF/VEGF, and their receptors in AIDS-associated
KS
To investigate whether VEGF-C and its receptors might be involved in
the
development of AIDS-associated KS, we performed ISH on six cases of
cutaneous
KS. The specificity of all ISH reactions was demonstrated by
hybridization with
the radio-labeled sense RNA probes, which did not reveal any signal.
High
amounts of KDR mRNA (receptor for both, VEGF-C and VPF/VEGF) were
detected in
numerous spindle-shaped cells in all AIDS-KS lesions examined (Fig.
1A,B).
Endothelial cells of small blood vessels within and immediately
adjacent to the
lesions labeled strongly for both, KDR and flt-1 mRNA (Fig. 1A-D,
respectively),
as previously reported (Brown et al. 1996). Tumor cells, however,
expressed
little or no flt-1 mRNA (Fig. 1C,D). Importantly, hybridization
analysis showed
that flt-4 mRNA was abundantly expressed in spindle cells of AIDS-KS
(Fig.
1E,F). In contrast, endothelial cells lining small blood vessels
expressing KDR
and flt-1 mRNA did not express any flt-4 mRNA (Fig. 1E,F).
Immunofluorescent
staining confirmed expression of flt-4 protein in spindle-shaped KS
cells, and
double immuno- fluorescence labeling revealed its colocalization with
the
endothelial cell marker CD31 (Fig. 2). Whereas KS tumor cells did not
express
any significant amounts of VPF/VEGF (Fig. 1I, J) or VEGF-C mRNA, VEGF-C
mRNA was
expressed at high levels in endothelial cells of arteries as well as of
small
blood vessels associated with KS lesions (Fig. 1G,H). The expression of
VEGF-C
protein in blood vessels associated with KS lesions was confirmed by
immunofluorescent stainings (Fig. 3). Occasionally, cells closely
apposed to
endothelial cells, most likely smooth muscle cells, also labeled
strongly for
VEGF-C protein (Fig. 3).
In summary,
whereas endothelial cells of small blood vessels labeled strongly
for KDR and flt-1, but not for flt-4 mRNA, the KS tumor cells expressed
KDR and
flt-4, but not flt-1 mRNA. Furthermore, VEGF-C, the ligand for KDR and
flt-4,
was found to be expressed in KS lesions, suggesting a role of VEGF-C
and its
receptors in the pathogenesis of AIDS-associated KS.
VEGF-C stimulates proliferation of KS cells in vitro
The expression of the flt-4 receptor in KS tumor cells and of its
ligand VEGF-C
in endothelial cells of KS lesions suggested a paracrine role of VEGF-C
in KS
tumor growth. Therefore, we tested the capability of VEGF-C to promote
the
proliferation of cultured KS cells which are known to express the flt-4
receptor
(Liu et al. 1997). VEGF-C induced a potent, concentration-dependent
increase in
cell numbers after 4 d of treatment with 1–100 ng of human recombinant
VEGF-C
(Fig. 4), revealing VEGF-C as a growth factor for KS tumor cells.
VPF/VEGF upregulates expression of VEGF-C in vascular
endothelial cells
As we observed increased levels of VEGF-C mRNA in endothelial cells of
blood
vessels surrounding cutaneous KS lesions, we next studied the
regulation of VEGF-C
gene expression in HDMEC (Richard et al. 1998) by angiogenic growth
factors.
HDMEC at 80% confluency were treated with endothelial growth factors
for 4–24
h, after which total RNA was isolated, electrophoresed, and subjected
to
northern blot hybridization using a human VEGF-C probe. Moderate
amounts of
steady-state VEGF-C mRNA were detectable in HDMEC under basal
conditions (Fig.
5A). Northern hybridization revealed a single VEGF-C band in HDMEC;
however, a
faint, slower migrating second band was observed after longer exposure
times.
Following treatment with VPF/VEGF, a concentration-dependent increase
in VEGF-C
mRNA expression was seen after 4 h, continuing throughout the
experiment (24 h).
Maximal stimulation was obtained with 20 ng per ml VPF/VEGF (Fig. 5A).
In
contrast, induction of VEGF-C expression in HDMEC was not observed
following
treatment with basic fibroblast growth factor, PDGF-AA, PDGF-BB, PlGF,
or TNF-
(data not shown).
VEGF-C stimulates proliferation of HDMEC
To test the hypothesis that VEGF-C could be an autocrine growth factor
for
vascular endothelial cells, we next examined the ability of VEGF-C to
stimulate
the proliferation of microvascular endothelial cells derived from the
skin.
HDMEC were treated with VEGF-C (0.3–30 ng per ml) alone or in
combination with
VPF/VEGF (0.4 ng per ml). Stimulation of [3H]thymidine incorporation
was
measured after 48 h of treatment. VEGF-C induced a
concentration-dependent
increase in [3H]thymidine incorporation by HDMEC (Fig. 5B), with a
minimal
effective concentration of 0.3 ng per ml. The extent of stimulation by
VEGF-C
was comparable with that of VPF/VEGF in all concentrations tested (data
not
shown). When administered together with VPF/VEGF, the effect of VEGF-C
was
markedly increased as compared with the effect observed with each
factor alone.
In fact, in a concentration range where each of the factors had little
effect
(0.3 ng per ml), co-addition of both factors induced synergistic
effects. With a
moderate increase in VEGF-C concentration (3 ng per ml), the response
was
greater than additive. These results identify VEGF-C as a potent
mitogenic
factor for skin microvascular endothelial cells.
Discussion
VEGF-C is a novel member of the VEGF family of angiogenic growth
factors,
distinguished by its capacity to stimulate growth of lymphatic vascular
endothelium in vivo (Joukov et al. 1996; Lee et al. 1996; Jeltsch et
al. 1997;
Oh et al. 1997). In adult human tissues, the VEGF-C receptor flt-4 has
been
found exclusively expressed by lymphatic endothelium, and thus has been
considered a marker of lymphatic vessels (Jussila et al. 1998;
Kaipainen et al.
1995). The second VEGF-C receptor, KDR, is prevalently expressed by
activated
endothelium of blood vessels, and is also utilized by VPF/VEGF (Joukov
et al.
1996; Neufeld et al. 1999). Previously, we found strong expression of
KDR in KS
tumor cells (Brown et al. 1996). Surprisingly however, we were unable
to detect
high levels of its ligand VPF/VEGF in most cases (Brown et al. 1996),
prompting
us to examine the hypothesis that a different KDR ligand, VEGF-C, may
partake in
the development of KS.
In this study we show that VEGF-C mRNA and protein were strongly
expressed by
endothelial cells of large blood vessels surrounding the KS lesions and
that
high levels of flt-4 receptor mRNA and protein were expressed in
spindle-shaped
KS tumor cells. In agreement with our findings, the expression of flt-4
protein
has very recently been reported in KS spindle cells in vivo (Jussila et
al.
1998; Weninger et al. 1999). VEGF-C has also been shown to activate the
flt-4
receptor present on cultured KS cells (Liu et al. 1997). We demonstrate
here
that VEGF-C is a potent mitogen for KS tumor cells in vitro. Taken
together, our
results strongly suggest that VEGF-C expressed by endothelial cells
stimulates
proliferation of KS tumor cells in vivo. It remains to be established
whether
another flt-4 ligand, VEGF-D (Achen et al. 1998) or some yet
unidentified
ligands may also be implicated.
VEGF-C may further play a part in KS through interaction with the KDR
receptor,
which was strongly expressed by KS tumor cells, in accordance with
previous
studies (Brown et al. 1996; Masood et al. 1997). Based on the
expression of VPF/VEGF
by cultured KS cells (Weindel et al. 1992; Cornali et al. 1996; Masood
et al.
1997; Nakamura et al. 1997), VPF/VEGF has been suggested as a factor of
paramount importance in KS. The data regarding the expression of
VPF/VEGF in KS
cells in vivo, however, remained inconclusive. Here we confirm our
earlier
findings that VPF/VEGF was not consistently expressed by KS tumor
cells. Whereas
we identified inflammatory cells infiltrating KS lesions and
hyperplastic
keratinocytes as alternate sources of VPF/VEGF (Brown et al. 1996), the
question
remains whether the levels produced by these cells are sufficient to
bring about
effects such as proliferation of KS tumor cells, prominent angiogenesis
and
vascular permeability. It appears that VEGF-C present in KS may
function either
in cooperation or in competition with VPF/VEGF for the KDR receptor. To
test
these possibilities, we examined the effects of VEGF-C alone or in
combination
with VPF/VEGF on human skin microvascular endothelial cells in culture.
VEGF-C
promoted proliferation of HDMEC with a similar potency as VPF/VEGF. In
contrast,
it has been reported that VEGF-C was 50–100-fold less potent than
VPF/VEGF in
inducing the proliferation of bovine capillary endothelial cells
(Joukov et al.
1996; Joukov et al. 1997), human umbilical vein endothelial cells
(HUVEC), or
lung microvascular endothelial cells (Lee et al. 1996; Witzenbichler et
al.
1998). When injected s.c. into the skin however, VEGF-C was only
4–5-fold less
potent in inducing microvascular permeability (Joukov et al. 1997),
suggesting
that endothelial cells derived from the skin may be more responsive to
VEGF-C
than endothelial cells derived from other body sites. When administered
together
with VPF/VEGF, the effect of VEGF-C on endothelial cell proliferation
was
clearly enhanced. In a concentration range where each of the factors
had very
little effect, the co-addition induced synergistic effects. With a
moderate
increase in VEGF-C concentration, the response became additive. These
data
indicate that, if the same synergy exists in vivo, even very low
concentrations
of both growth factors might have pronounced effects, possibly
sufficient to
induce neovascularization and vascular permeability. Thus, VEGF-C, in
cooperation with VPF/VEGF, may play a part in KS tumor cell
proliferation,
angiogenesis, and edema typically seen in these tumors. In accordance
with our
findings, a recent report demonstrated synergism between VEGF-C and
basic
fibroblast growth factor or VPF/VEGF on in vitro angiogenesis (Pepper
et al.
1998). The mitogenic effect of VEGF-C on cultured endothelial cells is
probably
mediated through KDR, as HDMEC did not express significant amounts of
the flt-4
receptor. Indeed, a recombinant point mutant of VEGF-C that binds and
activates
selectively flt-4 did not induce endothelial cell migration and
vascular
permeability (Joukov et al. 1998). Expression of flt-4 mRNA in cultured
human
endothelial cells has been observed by others (Hewett & Murray
1996),
possibly reflecting a small number of lymphatic endothelial cells
contained
within cultured blood vascular endothelial cells. Alternatively, the
flt-4
expression pattern may be modulated in culture and may not reflect the
expression pattern observed in vivo.
Thus far,
expression of VEGF-C by endothelial cells in vivo had not been
reported. We observed significant amounts of VEGF-C mRNA and protein
expressed
by blood vascular endothelium adjacent to KS lesions in vivo and have
verified
this finding using HDMEC in vitro. Cultured HUVEC were recently found
to express
VEGF-C mRNA, and its levels were increased by treatment with
interleukin-1ß and
TNF- (Ristimaki et al. 1998). As outlined above, VEGF-C greatly
stimulated
proliferation of HDMEC in vitro, raising the intriguing possibility
that VEGF-C,
upregulated in vascular endothelium under certain conditions, may
regulate
endothelial cell responses in an autocrine manner.
There are significant differences in the regulation of VPF/VEGF and
VEGF-C gene
transcription. Cytokines and growth factors induce VEGF-C mRNA
expression in
cultured cells yet hypoxia and oncogenes, important regulators of
VPF/VEGF
expression, have no effect (Enholm et al. 1997). In human fibroblasts,
VEGF-C
transcription is stimulated by serum and its components, and by the
inflammatory
cytokines interleukin-1, interleukin-1ß, and TNF- (Enholm et al. 1997;
Ristimaki et al. 1998). We studied the regulation of the VEGF-C gene
expression
by growth factors in endothelial cells. Importantly, VPF/VEGF induced
strong,
concentration-dependent stimulation of VEGF-C transcription, whereas no
effects
were observed upon stimulation with the other growth factors tested,
i.e., PDGF,
basic fibroblast growth factor, PlGF, and TNF-. Thus, VPF/VEGF may
induce
endothelial cell responses in part by inducing a VEGF-C autocrine loop.
Furthermore, the regulation of the expression of the lymphangiogenic
factor VEGF-C
by the major angiogenic factor VPF/VEGF is an interesting concept, as
it is
conceivable that tissues with increased demands for angiogenesis would
also
increase their demands for lymphangiogenesis.
In conclusion, our results suggest that VEGF-C and its receptors flt-4
and KDR
play a major part in the pathogenesis of AIDS-associated KS. In
cooperation,
VEGF-C and VPF/VEGF are likely to be involved in KS tumor formation by
stimulating tumor cell proliferation, angiogenesis, and microvascular
permeability. The strong expression of the flt-4 receptor in KS tumor
cells, its
coexpression with the endothelial cell marker CD31, and the presence of
the
lymphangiogenic factor VEGF-C within the lesions are in support of a
lymphatic
origin and/or differentiation of KS tumor cells.
Acknowledgements
This work was supported by the Human Frontier Science Program (MS), by
NIH/NCI
grant CA69184 (MD), by American Cancer Society Research Project grant
99-23901
(MD), and by the Cutaneous Biology Research Center through the
Massachusetts
General Hospital/Shiseido Co. Ltd. Agreement (MD).
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Manuscript received 24 March 1999; revised 26 August 1999; accepted for
publication 6 September 1999
ILLUSTRATED ARTICLE WITH
LINKS FOR FURTHER STUDY
http://www.jidonline.org/cgi/content/full/113/6/1047?ijkey=7117a76bdfe214f6e8f999932d7aea06f1b9527c
==============
Kaposi Sarcoma, KSHV and lymphangiogensis
http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0625.2007.00607_5.x/pdf
=============
Lymphedema People Angiogenesis Related Pages:
Angiogenesis
http://www.lymphedemapeople.com/thesite/angiogenesis.htm
Angiogenesis and Cancer
http://www.lymphedemapeople.com/thesite/angiogenesis_and_cancer.htm
Angiogenesis and Cancer
Control
http://www.lymphedemapeople.com/thesite/angiogenesis_and_cancer_control.htm
Angiogenesis Inhibitors
and Cancer
http://www.lymphedemapeople.com/thesite/angiogenesis_inhibitors_and_cancer.htm
===========================
Lymphedema People Lymphangiogenesis Related Pages:
The Formation of
Lymphatic Vessels and Its Importance in the Setting of Malignancy
http://www.lymphedemapeople.com/thesite/lymphangiogenesis_formation_of_lymphatic_vessels_and_malignancy.htm
Lymphangiogenesis
Lymphedema and Cancer
http://www.lymphedemapeople.com/thesite/lymphangiogenesis_lymphedema_and_cancer.htm
Lymphangiogenesis and
Gastric Cancer
http://www.lymphedemapeople.com/thesite/lymphangiogenesis_and_gastric_cancer.htm
Lymphangiogenesis in Head
and Neck Cancer
http://www.lymphedemapeople.com/thesite/lymphangiogenesis_in_head_and_neck_cancer.htm
Lymphangiogenesis and
Kaposi's Sarcoma VEGF-C
http://www.lymphedemapeople.com/thesite/lymphangiogenesis_and_kaposis_sarcoma_vegfc.htm
Lymphangiogenesis in
Wound Healing
http://www.lymphedemapeople.com/thesite/lymphangiogenesis_in_wound_healing.htm
A model for gene therapy
of human hereditary
lymphedema
http://www.lymphedemapeople.com/thesite/a_model_for_gene_therapy_of_human_lymphedema.htm
VEGFR-3 Ligands and
Lymphangiogenesis (1)
http://www.lymphedemapeople.com/thesite/vegfr3_ligands_lymphangiogenesis_1.htm
VEGFR-3 Ligands and
Lymphangiogenesis (2)
http://www.lymphedemapeople.com/thesite/vegfr3_ligands_lymphangiogenesis_2.htm
VEGFR-3 Ligands and
Lymphangiogenesis (3)
http://www.lymphedemapeople.com/thesite/vegfr3_ligands_lymphangiogenesis_3.htm
Vascular Endothelial
Growth Factor; VEGF
http://www.lymphedemapeople/thesite/vascular_endothelial_growth_factor_VEGF.htm
VEGF-D is the strongest
angiogenic and
lymphangiogenic effector
http://www.lymphedemapeople.com/thesite/VEGFD_Angiogenic_Lymphangiogenic_Effector.htm
Inhibition of Lymphatic
Regeneration by VEGFR3
http://www.lymphedemapeople.com/thesite/Inhibition_of_Lymphatic_Regeneration_by_VEGFR3.htm
VEGFR3 and Metastasis in
Prostate Cancer
http://www.lymphedemapeople.com/thesite/VEGFR3_and_Metastasis_in_Prostate_Cancer.htm
===========================
Lymphedema People Genetics, Research, Lymphangiogenesis, Angiogenesis Forum
http://www.lymphedemapeople.com/phpBB2/viewforum.php?f=16
===========================
Join us as we work for lymphedema patients everywehere:
Advocates for Lymphedema
Dedicated to be an advocacy group for lymphedema patients. Working towards education, legal reform, changing insurance practices, promoting research, reaching for a cure.
http://health.groups.yahoo.com/group/AdvocatesforLymphedema/
Subscribe: | AdvocatesforLymphedema-subscribe@yahoogroups.com |
Pat O'Connor
Lymphedema People / Advocates for Lymphedema
===========================
For information about Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema\
For Information about Lymphedema Complications
http://www.lymphedemapeople.com/wiki/doku.php?id=complications_of_lymphedema
For Lymphedema Personal Stories
http://www.lymphedemapeople.com/phpBB2/viewforum.php?f=3
For information about How to Treat a Lymphedema Wound
http://www.lymphedemapeople.com/wiki/doku.php?id=how_to_treat_a_lymphedema_wound
For information about Lymphedema Treatment
http://www.lymphedemapeople.com/wiki/doku.php?id=treatment
For information about Exercises for Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=exercises_for_lymphedema
For information on Infections Associated with Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=infections_associated_with_lymphedema
For information on Lymphedema in Children
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema_in_children
Lymphedema Glossary
http://www.lymphedemapeople.com/wiki/doku.php?id=glossary:listing
===========================
Lymphedema People - Support Groups
-----------------------------------------------
Children
with Lymphedema
The time has come for families, parents, caregivers to have a support
group of
their own. Support group for parents, families and caregivers of
chilren with
lymphedema. Sharing information on coping, diagnosis, treatment and
prognosis.
Sponsored by Lymphedema People.
http://health.groups.yahoo.com/group/childrenwithlymphedema/
Subscribe: childrenwithlymphedema-subscribe@yahoogroups.com
......................
Lipedema
Lipodema Lipoedema
No matter how you spell it, this is another very little understood and
totally
frustrating conditions out there. This will be a support group for
those
suffering with lipedema/lipodema. A place for information, sharing
experiences,
exploring treatment options and coping.
Come join, be a part of the family!
http://health.groups.yahoo.com/group/lipedema_lipodema_lipoedema/?yguid=209645515
Subscribe: lipedema_lipodema_lipoedema-subscribe@yahoogroups.com
......................
MEN WITH LYMPHEDEMA
If you are a
man with lymphedema; a man with a loved one with lymphedema who you are
trying
to help and understand come join us and discover what it is to be the
master
instead of the sufferer of lymphedema.
http://health.groups.yahoo.com/group/menwithlymphedema/
Subscribe: menwithlymphedema-subscribe@yahoogroups.com
......................
All
About Lymphangiectasia
Support group for parents, patients, children who suffer from all forms
of
lymphangiectasia. This condition is caused by dilation of the
lymphatics. It can
affect the intestinal tract, lungs and other critical body areas.
http://health.groups.yahoo.com/group/allaboutlymphangiectasia/
Subscribe: allaboutlymphangiectasia-subscribe@yahoogroups.com
......................
Lymphatic
Disorders Support Group @ Yahoo Groups
While we have a number
of support groups for lymphedema... there is nothing out there for
other
lymphatic disorders. Because we have one of the most comprehensive
information
sites on all lymphatic disorders, I thought perhaps, it is time that
one be
offered.
DISCRIPTION
Information and support for rare and unusual disorders affecting the
lymph
system. Includes lymphangiomas, lymphatic malformations,
telangiectasia,
hennekam's syndrome, distichiasis, Figueroa
syndrome, ptosis syndrome, plus many more. Extensive database of
information
available through sister site Lymphedema People.
http://health.groups.yahoo.com/group/lymphaticdisorders/
Subscribe: lymphaticdisorders-subscribe@yahoogroups.com
Lymphedema People New Wiki Pages
Have
you seen our new “Wiki”
pages yet? Listed
below are just a
sample of the more than 140 pages now listed in our Wiki section. We
are also
working on hundred more. Come
and
take a stroll!
Lymphedema
Glossary
http://www.lymphedemapeople.com/wiki/doku.php?id=glossary:listing
Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema
Arm
Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=arm_lymphedema
Leg
Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=leg_lymphedema
Acute
Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=acute_lymphedema
The
Lymphedema Diet
http://www.lymphedemapeople.com/wiki/doku.php?id=the_lymphedema_diet
Exercises
for Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=exercises_for_lymphedema
Diuretics
are not for Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=diuretics_are_not_for_lymphedema
Lymphedema
People Online Support
Groups
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema_people_online_support_groups
Lipedema
http://www.lymphedemapeople.com/wiki/doku.php?id=lipedema
Treatment
http://www.lymphedemapeople.com/wiki/doku.php?id=treatment
Lymphedema
and Pain Management
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema_and_pain_management
Manual
Lymphatic Drainage (MLD) and Complex Decongestive Therapy (CDT)
Infections
Associated with Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=infections_associated_with_lymphedema
How
to Treat a Lymphedema Wound
http://www.lymphedemapeople.com/wiki/doku.php?id=how_to_treat_a_lymphedema_wound
Fungal
Infections Associated with
Lymphedema
http://www.lymphedemapeople.com/wiki/doku.php?id=fungal_infections_associated_with_lymphedema
Lymphedema
in Children
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema_in_children
Lymphoscintigraphy
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphoscintigraphy
Magnetic
Resonance Imaging
http://www.lymphedemapeople.com/wiki/doku.php?id=magnetic_resonance_imaging
Extraperitoneal
para-aortic lymph node dissection (EPLND)
Axillary
node biopsy
http://www.lymphedemapeople.com/wiki/doku.php?id=axillary_node_biopsy
Sentinel
Node Biopsy
http://www.lymphedemapeople.com/wiki/doku.php?id=sentinel_node_biopsy
Small
Needle Biopsy - Fine Needle Aspiration
http://www.lymphedemapeople.com/wiki/doku.php?id=small_needle_biopsy
Magnetic
Resonance Imaging
http://www.lymphedemapeople.com/wiki/doku.php?id=magnetic_resonance_imaging
Lymphedema
Gene FOXC2
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema_gene_foxc2
Lymphedema Gene VEGFC
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema_gene_vegfc
Lymphedema Gene SOX18
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema_gene_sox18
Lymphedema
and Pregnancy
http://www.lymphedemapeople.com/wiki/doku.php?id=lymphedema_and_pregnancy
Home page: Lymphedema People
http://www.lymphedemapeople.com
Page Updated: Dec. 24, 2011