Expression Pattern and Prognostic Impact of Vascular Endothelial Growth Factors VEGF and VEGF-C and Their Receptors Flt-1, KDR and Flt-4 in Peripheral T-Cell Lymphomas.

The vascular endothelial growth factor family (VEGF, VEGF-B, -C and -D) is the main regulator of angiogenesis and lymphangiogenesis via their receptors, Flt-1, KDR and Flt-4. The aim of the present study was to estimate the microvascular density and investigate the expression of VEGF, VEGF-C and its receptors Flt-1, KDR and Flt-4 in peripheral T-cell lymphomas (PTCL).

Material and methods: Microvessel density (MVD) was determined after CD34 immunohistochemical (IH) staining of endothelial cells in pre-therapeutic lymph-node biopsies from 107 cases of PTCL (64 unspecified, 1 angiocentric, 10 angioimmunoblastic and 32 anaplastic large cell T/0). 44 of these cases (28 unspecified, 1 angiocentric, 4 angioimmunoblatic and 11 anaplastic large cell T/0) were investigated for expression of angiogenic molecules, VEGF, VEGF-C and their receptors by IH at protein level. Furthermore, VEGF and VEGF-C mRNA expression was detected by non-isotopic ′in situ′ hybridization. The angiogenic scores were correlated to pre-therapeutic clinical parameters, treatment response and survival.

Results: Tumoral expression of VEGF, VEGF-C and of their receptors was detected in the majority of the PTCL biopsies investigated (VEGF mRNA: 73%, VEGF protein: 95%; VEGF-C mRNA: 79%; VEGF-C protein: 79%; Flt-1 and KDR: 100%; Flt-4: 26%). All biopsies contained VEGF, Flt-1 and KDR positive vessels and VEGF-C was also widely expressed by the endothelial cells (3 negative cases), while endothelial Flt-4 expression was detected only in 43% of cases. High MVD scores correlated with an advanced clinical stadium (Ann Arbor) (p=0.047). A strong diffuse VEGF mRNA expression significantly correlated with a poorer overall survival (p=0.0015) as compared to focal or negative ISH signal. The predictive value of this parameter persisted at multivariate level independently of the International Prognostic Index (HR: 3.95, p=0.012, Cox regression).

Conclusion: VEGF, VEGF-C and their receptors are expressed by both lymphoma and endothelial cells in the majority of PTCL cases. VEGF expression seems to have an adverse impact on survival. Larger studies of angiogenesis/lymphangiogenesis in PTCL are needed to clarify the biological role of these molecules and identify possible therapeutic targets.