Expression Of VEGF And VEGFRs In Plasma And Tumor Tissues Of Patients With NSCLC And Its Clinical Significance

The treatment modality of lung cancer has been changing from “one fits all” to targeted therapy in the decades. Tumor angiogenesis is essential for cancer growth and metastasis, therefore, therapies targeting VEGF or VEGFRs have been developed to inhibit tumor angiogenesis.Vascular endothelial growth factor(VEGF) is one of the most important factors in angiogenesis, exerting its biologic effect, such as endothelial cells activation, migration and vascular permeability, through binding with VEGFR-1 and VEGFR-2. Generally, VEGFR-1 and VEGFR-2 express on endothelial cells, but they could also express on macrophages, hematopoietic stem cell and tumor cells. In other words, VEGF serves as an autocrine growth factor that enhances the malignant potential of tumor cells. VEGFR-1 has a high affinity for VEGF but low angiogenic activity; in contrast, VEGFR-2 is believed to enhance the angiogenic effects of VEGF. Apart from the VEGFRs expressed on membrane, there are naturally occurring soluble receptors in peripheral blood, namely s VEGFR-1 and s VEGFR-2, which contains the ligand binding domain, but lacks the transmembrane region and intracellular kinase domains of the full-length membrane-bound protein.Soluble VEGFR-1, an endogenous VEGF-trapping molecule, is supposed to be mainly inhibitory, sequestering free VEGF in peripheral blood, thus acting as a regulator of VEGF bioavailability. In addition to sequestering the ligand, s VEGFR-1 can form heterodimers with transmembrane VEGFR-2, prevent its autophosphorylation and thus abolish signaling in a dominant-negative fashion. As a potent and endogenous inhibitor, s VEGFR-1 is studied more frequently in preeclampsia, but not in cancer. Soluble VEGFR-2 is supposed to be inhibitory to angiogenesis, due to its binding ability to free VEGF in theory and proven in some experiments, but most research about s VEGFR-2 is involved in clinical trials of anti-angiogenic drugs. Some documents showed that significant suppression of s VEGFR-2 was achieved after anti-angiogenic treatment and it is related with anti-tumor activity. To the best of my knowledge, there is no report about s VEGFR-1 and s VEGFR-2 with prognosis in NSCLC.Both VEGFR-1 and VEGFR-2 have two isoforms: the full length form and a soluble isoform, moreover the two isoforms act oppositely in theory. How these molecular express in NSCLC and what is the relationship between the expression of them with clinicopathological factors and prognosis? To clarify this question, we designed this clinical study. This study included two parts:Part I: We assessed preoperational plasma VEGF, s VEGFR-1 and s VEGFR-2 levels in 115 patients with NSCLC and 40 healthy control subjects using an enzyme linked immunosorbent assay(ELISA). The correlation between these angiogenic factors and clinicopathologic factors, including staging and overall survival, was analyzed. Plasma levels of VEGF, and s VEGFR-2 were significantly higher in patients with NSCLC compared with those in controls, but plasma s VEGFR-1 was significantly lower in NSCLC. Soluble VEGFR-2 was positively related with T stage and p TNM. Soluble VEGFR-1 concentration was not correlated with any of histopathological factors, but the VEGF/s VEGFR-1 ratio was correlated with tumor diameter significantly. The expression of s VEGFR-1 and s VEGFR-2 were positively correlated with VEGF level, although the correlation was relatively weak(r=0.250, r=0.334, respectively). Survival analysis showed that VEGF/s VEGFR-1 ratio was an independent predictor for NSCLC survival. Higher VEGF/s VEGFR-1 ratio was significantly correlated with poor outcome in NSCLC(HR=2.261, 95%CI: 1.124-4.551).Part II: We examined tumor VEGF, VEGFR-1 and VEGFR-2 expression in 217 patients with NSCLC using immunohistochemical staining method(IHC). The correlation between these angiogenesis-related factors and clinical factors was analyzed. In cancer cells, VEGF and VEGFR1-2 located dominantly at cytoplasm. VEGFR-2’s expression was positively correlated with tumor diameter. The percentage of patients both in high level of VEGF and VEGFR-1 expression in IIIA stage was higher than stage I and II. The percentage of patients both in high level of VEGF and VEGFR-2 expression was higher in T3-4 than T1-2. The expression of VEGF was weakly associated with VEGFR-2(r=0.172). Survival analysis showed that high expression of VEGF/VEGFR-2 was correlated with poor survival(HR=1.581, 95%CI 1.027-2.434). In the subgroup analysis of high expression of VEGF/VEGFR-2, high expression of VEGFR-1 could increase risk of death significantly( HR=2.531, 95%CI 1.305-4.906).The present study showed that the unbalance between pro-angiogenic factor(VEGF) and anti-angiogenic factor(s VEGFR-1) involved in tumorigenesis and proliferation. High VEGF/s VEGFR-1 ratio was a poor predictor of prognosis in NSCLC. High expression in tumor tissue of VEGF and VEGFR-2 at the same time is associated with tumor proliferation and metastasis. In addition, high expression of both VEGF and VEGFR-2 were in high expression level was indicators of shorter survival.In the subgroup analysis of high expression of VEGF&VEGFR-2, high level of VEGFR-1 could increase risk of death significantly(HR=2.531,95%CI 1.305-4.906). In conclusion, the examination of VEGF and VEGFR1-2 in plasma and tumor tissue could not only broaden the knowledge about individual anti-angiogenesis therapy, but also supply information for prognosis evaluation and risk stratification.