High Circulating Vascular Endothelial Growth Factor Receptor-1 Correlates with Increased Microvessel Density and Inferior Survival in Newly-Diagnosed Patients with Multiple Myeloma Who Receive Frontline Therapy with Novel Agent-Based Regimens
Authors: Papassotiriou Gerasimos-Petros , Terpos Evangelos , Kastritis Efstathios , Gkotzamanidou Maria , Apostolakou Filia , Eleutherakis-Papaiakovou Evangelos , Dimopoulos Meletios Athanasios 
Published: October 2019

Abstract
Abstract 5082
Vascular Endothelial Growth Factor Receptor-1 (VEGF-R1) is a receptor tyrosine kinase specific for the angiogenic factors VEGF-A, VEGF-B and placenta growth factor (PlGF), which is also a member of the VEGF family. In contrast to VEGF, the role of PlGF and VEGFR-1 in neovascularization is less clear. Angiogenesis is increased in patients with multiple myeloma (MM) and correlated with inferior outcome in several studies. The role of PlGF and VEGFR-1 has not been evaluated in MM. Therefore, we measured the circulating levels of PlGF and VEGFR-1: i) in 64 patients with newly diagnosed myeloma: 16 with asymptomatic disease (7M/9F; median age 59 years, range 37–82 years) and 48 with symptomatic myeloma (30M/18F; median age 70 years, range 45–89 years; ii) in 8 patients with MGUS (4M/4F; median age 72 years, range 39–84 years); and iii) in 20 healthy, gender and age-matched controls. PlGF and sVEGFR-1 were measured in serum samples using an electrochemiluminescence immunoassays (ECLIA) on a cobas e411 immunology analyzer (Roche Diagnostics, Mannheim, Germany). We also explored possible correlations between PlGF and VEGFR-1 circulating levels with clinical and laboratory values of the patients including microvessel density (MVD) of the bone marrow trephine biopsies and survival. Immunohistochemical identification of microvascular endothelial cells was performed in the trephine biopsies of MGUS and MM patients using a human monoclonal antibody against CD34 (DAKO A/S, Glostrup, Denmark). In each biopsy sample, microvessels were counted in at least 3 independent hot spots per section and the MVD of a bone marrow specimen was calculated as the mean value of all independent readings and recorded as the number of microvessels per ×400 field. When the microvessel count was 1–2, angiogenesis was characterized as low grade, while intermediate grade angiogenesis was defined by the presence of a microvessel count of 3–6 and high grade angiogenesis by the presence of microvessel count ≥7.
Compared to controls, patients with symptomatic MM had elevated circulating PlGF (median: 19.5 pg/ml, range: 6.7–91.3 pg/ml vs. 16.1 pg/ml, 10.9–25.0 pg/ml of control group; p<0.01) and elevated VEGFR-1 levels (88.6 pg/ml, 51.5–320 pg/ml vs. 73.3 pg/ml, 62.9–100.8 pg/ml; p<0.001). Patients with MGUS and asymptomatic MM had no differences compared to controls for PlGF and VEGFR-1. In myeloma patients there was a strong correlation between circulating PlGF and VEGFR-1 levels (r=0.62, p=0.009 for asymptomatic patients and r=0.36, p=0.01 for symptomatic MM). PlGF also correlated with IL-6 (r=0.68, p<0.01) and high sensitivity CRP (r=0.5031, p<0.01) in MM patients.
Of 16 patients with asymptomatic myeloma, 11 (68%) had low grade angiogenesis in the trephine biopsies and 5 (31%) intermediate grade angiogenesis; no one had high grade angiogenesis. There was no difference for PlGF levels between patients with low and intermediate grade angiogenesis in asymptomatic myeloma. However, patients with asymptomatic myeloma and intermediate grade angiogenesis had elevated VEGFR-1 (98.3 pg/ml, 87.1–148.9 pg/ml) compared to patients with low grade angiogenesis (72.3 pg/ml, 63.7–95.8 pg/ml). Similar results were obtained for patients with symptomatic myeloma. Of those, 18 (37%) had low grade angiogenesis in the trephine biopsies, while 20 (41%) had intermediate grade and 10 (20%) high grade angiogenesis. The median values and ranges of VEGFR-1 for low, intermediate and high grade angiogenesis were: 75.1 pg/ml (51.5–109.1 pg/ml), 94.2 pg/ml (61.2–143.8 pg/ml) and 151.8 pg/ml (103.7–320.0 pg/ml), respectively (p-ANOVA<0.0001).
All patients with symptomatic myeloma received frontline therapy with novel agent-based regimens: 25 with lenalidomide-based regimens, 16 with thalidomide-based regimens and 7 with bortezomib-based regimens. The median follow-up period was 18.8 months and 8/47 patients have died. The probability of survival was 86% at 1 year and 78% at 2 years. In the univariate analysis the VEGFR-1 as a continuous variable correlated with higher risk of death (HR: 1.011, 95% CI: 1.004–1.018, p=0.003).
In conclusion our study suggests that myeloma patients have increased circulating PlGF and VEGFR-1. High levels of VEGFR-1 correlated with increased angiogenesis and inferior survival, supporting a significant role of VEGFR-1 in the biology of angiogenesis in MM.

Disclosures:
No relevant conflicts of interest to declare.