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.