Clinical Significance Of VEGF-C And Flt-4 In Non-small Cell Lung Cancer

As the number one overall cause of the cancer-related death, lung cancer, whose most common type is non-small cell lung cancer(NSCLC) , is the leading public health concern worldwide. Of the estimated 174,470 people in the United State who were diagnosed with lung cancer in 2006.Non–small cell lung cancer (NSCLC) accounts for 70% to 80% of primary lung cancer. So treatment of NSCLC will be a challenge for medical stuff to deal with. The metastatic spread of tumor cells is responsible of the majority of cancer-related deaths. Lymph nodes are the most common sites of metastasis.Non–small cell lung cancer (NSCLC) is well-known for its ability to involve regional lymph nodes even at the early stages of tumor growth. Therefore,'N status'is a major determinant for the staging and clinical management of lung cancer.Once tumor cells are established in the sentinel lymph node (SLN), they can further metastasize to distant lymph nodes and beyond. Tumor-node-metastasis (TNM) system, generally used in the evaluation of tumor progression, and nodal involvement as well as distant metastasis,is the critical factor to determine the prognosis of NSCLC. Several clinical studies have shown that lymphatic invasion is a significant prognostic factor in NSCLC. Thus, it should be a new target in the diagnosis and therapy of NSCLC.It is widely accepted that angiogenesis is essential for both tumor growth and metastasis. In the absence of local angiogenesis, tumors cannot grow beyond 2 mm3 . In addition, tumor angiogenesis has been reported to be associated with metastasis of primary tumors. Clinical studies in human cancer patients have also demonstrated that angiogenesis is associated with tumor metastasis and a poor prognosis. Furthermore, current studies have indicated that lymphangiogenesis is also associated with tumor metastasis. Thus, understanding and controlling angiogenesis and lymphangiogenesis could lead to effective strategies for cancer treatment.However, the mechanisms of lymphatic metastasis have remained unclear for decades, mainly due to the lack of reliable markers for lymphatic vessels and identified lymphangiogenic growth factors in human cancers, and it makes our knowledge of the lymphatic system of lung cancer lags far behind that of the vascular system.Recent advances in molecular biology have revealed mechanism of lymphatic spread in malignant tumors. The vascular endothelial growth factor (VEGF) gene family, which encodes five polypeptide growth factors, VEGF-A, -B, -C, -D,and -E, and their receptor family are particularly important a group of growth factors and receptors because of their angiogenic and lymphangiogenic properties that promote the growth and metastasis of neoplasma.Vascular endothelial growth factor-C has been characterised as a lymphangiogenic and angiogenic growth factor and has been shown to signal through the receptors VEGFR-3 (also called Flt-4) and VEGFR-2. Among the vascular endothelial growth factor receptor (VEGFR) family members, Flt (fms-like tyrosine kinase)-4 is a receptor for VEGF-C and VEGF-D. Flt-4 is expressed on all of the embryonic endothelia, but its expression is largely restricted to the lymphatic endothelium in adult tissues. Recent studies have indicated that VEGFR-3, which has been proposed as a marker for lymphatic endothelial cells, is also expressed in a variety of human malignancies.Experimental studies have revealed that tumors can actively induce the formation of lymphatic vessels (lymphangiogenesis)– via release of VEGF-C or VEGF-D, which activating of Flt-4, and thereby promote metastasis to draining lymph nodes. Moreover, inhibition of Flt-4 signaling can suppress tumor lymphangiogenesis and lymph node metastasis. Thus, Flt-4 can also be an important diagnostic and therapeutic target for treating a variety of malignant tumors.In NSCLC, however, only a few clinical studies on VEGF-C (or VEGF-D), and Flt-4 expression have been reported, and clinical significance of VEGF-C (or VEGF-D), and Flt-4 expression on tumor cells and/or on endothelial cells remains controversial. Particularly, no study has documented a prognostic value of VEGF-C (or VEGF-D), and Flt-4 expression in endothelial cells. Therefore, we assessed the expression of VEGF-C and VEGFR-3 mRNA and protein in NSCLC by RT-PCR and Western Blot to demonstrate how they correlated with clinicopathological factors, including lymph node metastasis.A total of 78 consecutive patients with pathological stage I-IIIA NSCLC who underwent complete tumor resection without any preoperative therapy at Beijing Chest Hospital between December 2006 to June 2007, and whose 234 histologic specimens are available for PCR and 171 histologic specimens for Western blot were prospectively studied.Pathological stage was reevaluated and determined with the present TNM classification as revised in 1997. For analyses according to the different pathological type, different stage and different differentiation of cancer cells as well as other clinical features.PCR detection result:The relative contents of VEGF-C mRNA in cancer tissue and in paracancer were higher than those in normal tissues(VEGF-C mRNA 0.302±0.177, 0.209±0.131, 0.152±0.89) P<0.05,and the relative content of Flt-4 mRNA in cancer tissue was higher than that in normal tissue,(0.278±0.182 vs 0.181±0.128,P<0.05); the content in paracancer tissue was also higher than that in normal tissue,(0.199±0.128 vs 0.181±0.128, P> 0.05).The relationship between VEGF-C or Flt-4 mRNA expression and clinicopathological features are shown that the expression level of VEGF-C mRNA and Flt-4 both in cancer tissue and paracancer tissue have significantly different in lymph node groups and stage groups. In paracancer group, the expression level of VEGF-C mRNA and Flt-4 has significantly different in histological grade group. There were no significant different in different age, different tumor position, different tumor size and different pathological types.Westem blot detection:171 histologic specimens in 57 patients were detected by Westem blot among 78 NSCLC, the protein level of VEGF-C in cancer tissue, paracancer tissue and normal tissue were 0.631±0.300,0.502±0.246, 0.531±0.286, respectively, there was significant different between cancer tissue and normal tissue, P=0.000. but for all the clinicopathological features, there were no significant different between age, gender, pathological types, stages, lymph node status and differentiation.In conclusion, the present study gives evidence that VEGF-C and Flt-4 might play an important role in lymph node metastasis in NSCLC, Targeting the VEGF-C/Flt-4 may be therapeutically significant for certain types of tumours. Thus, the continued discovery and characterization of factors that regulate VEGF-C or Flt-4 will be essential for developing new therapies that limit the spread of cancer.