Discussion
DLCHL is the most common subtype of NHL in adults and constitutes
approximately 40% of cases. It was observed that the prognosis was
worse and the long-term survival was less in patients who did not fully
respond to the first treatment. Therefore, studies have been conducted
to investigate more effective and less toxic chemotherapy drugs and
biological agents for this specific and large patient group. Among the
treatment targets of these studies is angiogenesis, which is
increasingly important and is the main subject of many cancer treatment
researches(8). Our aim in this study is to immunohistochemically study
the relationship between the staining rates of mainly antiangiogenic
factor thrombospondin-1, angiogenic VEGF and PDGFR-in tissue
preparations in patients diagnosed with DLBCL as a result of
lymphadenopathy biopsy and their clinical features at the time of
diagnosis, response to treatment and prognosis.
İn the present study, it was observed that most of the patients were
stained with VEGF, although PDGFR-β was lower in patient group. We found
a statistically significant negative correlation between
thrombospondin-1 and PDGFR-β staining. Over-staining of VEGF and
under-staining of thrombospondin-1 shows us that the balance in lymphoma
favors angiogenetic factors. Also, while the rate of thrombospondin-1
staining is low, the significant PDGFR β staining rate supports this.
Again, in another study conducted by Paydas et al., the TSP-1 expression
rate of pathology preparations of 88 patients with DLBCL was found to be
14.8%, and its relationship with prognostic factors and survival could
not be demonstrated(9).
When the literature is reviewed, there are studies showing the
relationship between serum VEGF level and progression and prognosis of
cancers. VEGF expression in aggressive lymphoma subtypes such as DLBCL,
peripheral T-cell lymphoma, mantle cell lymphoma, and primary effusion
lymphoma have been shown to be highly and slightly increased in chronic
lymphocytic leukemia/small lymphocytic leukemia (CLL/SLL)(10-12).
Especially in acute lymphocytic leukemia and lymphomas, it was found
that some tumor cells expressing VEGFR-1 and VEGFR-2 are involved in the
survival, metastasis and proliferation of tumor cells by autocrine
mechanisms(13, 14). The current study revealed that VEGF was found to be
low in those with low IPI scores, higher staining rates in patient
group. Contrary to this extranodal involvement, hepatomegaly, bulky
disease, splenomaly, bone marrow involvement, refractory and relapse
rates were found to be high in patients with low VEGF staining.
In the study conducted by Riihijarvi et al. in 102 high-risk patients
under 65 years of age, it was found that serum VEGF levels were
statistically high in patients with high IPI score and performance score
and no relationship was found between serum VEGF level and gender, B
symptom, bulky disease(15). Again, in the study conducted by Salven et
al. on 200 patients with NHL, no significant relationship was found
between serum VEGF levels and stage, bulky disease, presence of B
symptoms, extranodal involvement and histological grade, but a
significant relationship was found between performance score (ECOG) and
IPI(16).
In another study, Hazar et al. demonstrated that VEGF negative NHL
patients had better treatment response than VEGF positive NHL
patient(17). Niitsu et al. also found higher VEGF levels in
treatment-resistant NHL patients. 132 In the study of
Salven et al., it was shown that serum VEGF level is an independent
indicator of poor prognosis for NHL patients. In a study conducted on
200 NHL patients, high pre-treatment serum VEGF levels (462 pg ml 7-1)
were found to be associated with high LDH levels, low performance status
and low survival. The 5-year survival rate was found to be 31% in those
with high serum VEGF levels, it was found 61% in those with low serum
VEGF levels (p<0.001). 5-year survival was found as 30% in
patients with high VEGF serum levels and 53% in patients with low VEGF
(p <0.001) in patients with DLBCL (n = 78) (16). In our study,
no significant relationship was found between VEGF expression at the
tissue level and overall survival and progression-free survival.
Although the prognostic value of VEGF expression at the tissue level in
patients with DLBCL is uncertain, it has been associated with poor
prognosis in studies with serum VEGF levels(3, 18). We thought that one
of the reasons for its uncertain expression at the tissue level may be
due to the fact that VEGF interacts with many inflammatory processes,
and there are many factors affecting its expression at the tissue level.
When PDGFR-β staining rates were compared with demographic data, it was
observed that patients with higher IPI score and stage had less
staining. When we looked at the survival analysis, we noticed that the
group with high PDGFR-β staining rate tended to have lower both OS and
PFS values. Studies have also found conflicting results regarding
angiogenic factors related to NHL depending on the heterogeneous
population, tissue sample or serum sample taken. Agreeably it was found
that the rate of PDGFR-β staining was higher in the control group. t can
be considered that this contradictory result may be influenced by the
angiogenetic environment in reactive lymphadenopathy in the control
group There are not many studies on the relationship between PDGFR-β
expression in tissue preparations and prognosis in patients with DLBCL.
As a result of its ligand binding to PDGFR-β, the PDGF receptor, the
tyrosine kinase pathway is activated, which induces cell proliferation,
differentiation and migration. Tyrosine kinase inhibitors such as
imatinib and sunitinib targeting PDGFR – β have been shown to be
effective in some solid tumors by decreasing pericyte density around the
vessel and weakening angiogenesis(19, 20). In neonatal mouse models in
which PDGFR-was functional blockade, it was observed that a number of
vascular smooth muscle cells were inhibited, apoptosis of vascular
endothelial cells was induced and glomerular vascular network formation
was negatively affected (21). In the study of Ruan et al. in which they
conducted with imatinib targeting PDGFR -β in mouse lymphomas, they have
demonstrated antiangiogenic effects in pericytes. It was observed that
in mice with 3 types of DLBCL models, with 2-3 weeks of imatinib
treatment, PDGFR -β + pericytes apoptosis and a significant decrease in
tumor volume were observed. It was thought that the decrease in
pericytes expressing PDGFR-β was due to increased apoptosis of CD 31+
vascular endothelial cells and decreased tumor vascularity (4).
TSP-1 is a multifunctional protein found in many biological processes
such as angiogenesis, apoptosis, TGF-beta activation, and immune
regulation. In some studies, thrombospondin has been shown to be a
negative regulator of tumor progression and angiogenesis. İn the current
study, it was observed that the 5-year OS value in the group with high
level of thrombospondin-1 staining was lower than the patients with low
level of staining, although it was not statistically significant. It was
observed that high level of thrombospondin expression in tumor cell
lines such as breast, skin, colorectal, glioblastome, hemangioblastoma
inhibits tumor cell angiogenesis and progression (5, 6). On the other
hand, thrombospondin is found as an adhesive protein in the
extracellular matrix in many epithelial cancers and has been shown to be
effective in cancer progression. Because thrombospondin-1 has been shown
to activate the plasminogen/plasmin system in many adenocarcinoma models
and increase tumor progression and metastasis (22). In the study of
Paydas et al. on tissue preparations of 177 NHL patients, it was found
that thrombospondin expression was associated with aggressive
morphology. Besides, patients expressing both thrombospondin and
survivin were shown to have both aggressive morphology and shorter OS.
Apart from this, no relation was found between B symptoms, extranodal
involvement, hepatomegaly, splenomegaly, and performance score used in
daily practice(23).
This study has some limitations. The number of cases and controls
examined is low, and it is recommended to examine them in large case
series. The patients who were used as the control group in our study had
lymph node excisional biopsy with suspicion of lymphoma and were
evaluated as reactive lymph node in pathological examination. It should
be kept in mind that factors such as viral infection that may cause
reactive lymph nodes may impair the angiogenetic expression profile.
In conclusion, in the present study it was observed that the rate of
VEGF staining was higher in patients with anemia, leukopenia, and
lymphopenia with prognostic importance. Although it was not
statistically significant 5-year OS and PFS values were low in patients
with high levels of expression PDGFR-β and thrombospondin-1. However,
another conclusion to be derived from our study should be that
angiogenetic factor expression should not be used in the distinction
between reactive/tumoral lymph node enlargement. Special agents specific
to the person and the type of DLBCL can be developed in the future with
studies that target VEGF, PDGFR-β, thrombospondin-1, with genetic
studies and examining multiple immunohistochemical markers, in which
there is a larger patient and control group for treatment in patients
with DBBHL.