VEGF Expression as Prognostic Factor in Early Clinical Stages of Chronic Lymphocytic Leukemia Patients

Abstract

Introduction: Chronic Lymphocytic Leukemia (CLL) is the most frequent leukemia in adults of western countries. Its clinical course is variable with some patients presenting an indolent disease while others have an aggressive disease requiring prompt treatment. Biomarkers to identify patients with poor prognosis, especially in early clinical stages, are being studied. Increase of angiogenesis, as an apoptosis deregulator, has been associated to poor prognosis in some malignant diseases such as Multiple Myeloma and Non-Hodgkin Lymphoma. Expression of Vascular Endothelial Growth Factor (VEGF) in CLL cells seems to have an unfavorable impact on prognosis, even though only a few studies have addressed this issue. AIMS: to analyze the expression of VEGF and its relation to Binet clinical stage, mutation status of IgVH and event free survival. Patients and Methods: 52 CLL patients diagnosed at UNIFESP and HSPE were studied. VEGF expression was evaluated on blood samples stained with Biotinylated Human VEGF (R&D Systems) monoclonal antibody and acquired with FACScalibur® and analyzed CellQuest® software. The expression of VEGF was considered positive when its mean fluorescence intensity was >200. IgVH mutation of 25 cases status was also studied by sequencing of the amplified samples by RT-PCR using VH family specific primers. The sequences were analysed with lg Blast® software and considered mutated (M) when there was a germline homology of 98% or greater and those displaying homology <98% were classified as unmutated (UM). Fisher’s exact test was used to compare results and Kaplan Meyer analysis to evaluate progression free survival (PFS). Differences were considered significant if p<0.05. Results: Of the 52 CLL patients (28M/24F, median age of 67 years varying between 38–78 years) 29 (56%) were Binet A, 17 (33%) Binet B and 6 (11%) Binet C. Twenty nine were VEGF+ and 23 VEGF−. Binet A patients were more frequently VEGF− than Binet B+C ones (p=0,002). In the whole population, VEGF+ patients presented shorter PFS when compared to VEGF− (p=0.004). Additionally, even early clinical stage patients (A+B), VEGF+ patients had an adverse prognosis with shorter PFS than those who were VEGF− (p=0.023). As for IgVH mutation status, of the 25 analyzed patients VEGF− were predominantly M while VEGF+ NM (p=0.043), and this difference was also seen when A+B patients were analysed (p=0.031). Conclusion: Our study shows that VEGF expression is associated with an adverse prognosis in CLL patients, even in those in early clinical stages (A+B). FC analysis of VEGF showed to be feasible and easily executable and could be evaluated as surrogate of IgVH mutation status in additional studies with a greater series of patients. (support: FAPESP proc.no.05/57792-0).