| Research Background:Primary lung cancer is one of the most common malignant tumors worldwide, with both morbidity and mortality showing an increasing trend, Non-small-cell lung cancer (NSCLC), which accounts for 75%-80% of primary lung cancer, has been an great threat to human health. At present, treatment methods for NSCLC include traditional surgery, radiotherapy, chemotherapy and recent immunotherapy and gene therapy, etc. But the survival rate, especially for patients who have metastasis, remains very low. Therefore, study of mechanism of infiltration and metastasis in NSCLC is significant to finding molecular prognostic markers used for predicting metastasis or prognosis in molecular lever and confirming effective complex treatment options.Tumour cells, mesenchymal cells and leukocytes can release multiple active signal factors, which can regulate and control tumor growth, induce angiogenesis and lymphangiogenesis. At present, known lymphatic growth factors include VEGF-C, VEGF-D, PDGF-BB, bFGF-2, Ang-2, etc. PDGF is a mitogen and chemo-attractant that exists extensively in human body organs. Via combining with PDGFR and inducing tyrosine kinase phosphorylation, PDGF can promote proliferation of endothelial cells, neovascularization and tumor growth. There is the existence of high expression of PDGFs and its receptor in lots of human malignant tumor such as ovarian cancer, breast cancer and prostatic cancer, which plays an important role in the process of tumor growth and development. In Cao's study, it has been demonstrated that PDGFs plays an important role in promoting lymphangiogenesis. It was also found that this effect is most obvious in PDGF-BB. These studies indicate that PDGF-BB may promote tumor lymphangiogenesis and lymphatic node metastasis. HGF, first obtained from purified plasma and platelets in partial rat resected liver, can stimulate hepatocyte proliferation. Later, it was found that a diffusion factor, secreted by fibroblasts, which could induce scattering in epithelial cells, was the same as HGF and was called scatter factor(SF). Previous study revealed that, mediated by its receptor c-Met, HGF could promote proliferation, migration and angiogenesis in many kind of tumors, which also plays an important role in tumoral invasion and metastasis. HGF is also a angiogenesis factor, it was found in recent study that HGF can promote lymphangiogenesis. However, the roles that PDGF-BB and HGF play in lymphangiogenesis and lymph node metastasis in NSCLC are still not fully understood.Objective:To test the expression of PDGF-BB and its receptor PDGFR-β, HGF and its receptor c-Met, and to evaluate their relationship to lymphangiogenesis and lymphatic metastasis in NSCLC.Method:In this study, we analyze expression of mRNA and protein for PDGF-BB and HGF in human lung cancer cell lines applying RT-PCR and Flow Cytometry method. Using immunohistochemistry method, the expression of PDGF-BB and HGF in lung cancer tissues was tested. And the relationship between their expression and clinicpathologic factors was then analyzed. Applying podoplanin and D2-40 for staining lymphatic vessels, we tested lymphatic vessel density and infiltration, counted lymphatic vessels both in tumor center and periphery in NSCLC. We also analyzed the relationship between PDGF-BB/HGF and LMVD, this provide new theory for clarifying molecular mechanism of tumoral formation and metastasis in NSCLC. Our study has implications for targeting PDGF-BB and HGF for diagnosis, prevention, treatment and new drugs exploitation in lung cancers.Results:1. Applying RT-PCR, the expression of transcription product for PDGF-BB and HGF was found among all the three kinds of lung cancer cell lines. We also detected the expression of PDGF-BB and HGF among all cell lines using FACS analysis.2. PDGF-BB were high expressed mainly in the membrane and cytoplasm of lung tumor cells. The positive expression is 63.7%(72/113). PDGFR-βwere high expressed mainly in the membrane and cytoplasm of the cells of tumor Stroma. The expression of PDGF-BB and PDGFR-βwas significantly higher in NSCLC tissues than in normal lung tissues (both P<0.05, respectively). The expression of PDGF-BB and PDGFR-βin NSCLC tissues had no correlation to age, gender, tumor size, histological type and differentiation grade. However, the expression of PDGF-BB and PDGFR-βwas positively correlated to TNM stage and lymph nodes metastasis.3. The expression of LMVD (15.4325±5.8967) was significantly higher in NSCLC tisuues than in normal tissues (5.9856±2.7336) (u=-3.760,P<0.01). The expression of LMVD had no correlation to gender, age, tumor-size, histological type, differentiation grade. However, the expression of LMVD was positively related to TNM stage and lymph nodes metastasis.4. HGF and its receptor c-Met were expressed mainly in the membrane and cytoplasm of NSCLC. The positive rate of expression for HGF was 67.3%(76/113), while 74.3%% for c-Met(84/113). The expression of HGF and c-Met in NSCLC tissues had no correlation to age, tumor size, histological type and differentiation grade. However, the expression of HGF and c-Met was positively correlated to TNM stage and lymph nodes metastasis.5. LMVD was significantly associated with PDGF-BB, HGF and their receptors. Higher LMVD was found in NSCLC with positive PDGF-BB or PDGFR-P expression than with that corresponding negative expression (PDGF-BB:16.58±5.45vs11.46±5.56, P=0.007; PDGFR-β: 15.79±5.63vs11.69±6.38, P=0.020). Higher LMVD was found in NSCLC with positive HGF or c-Met expression than with that corresponding negative expression(HGF:16.3051±5.3753vs10.9934±4.9668, P<0.05);(c-Met:15.6692±5.5386vsll.3700±5.3875, P<0.05).6. The coexpression of PDGF-BB and HGF in NSCLC tissues and the existence of their significant relationship, suggested that there may be some common mechanism that promotes lymphangiogenesis and lymph node metastasis.Conclusion:The expression of PDGF-BB, HGF and their receptor c-Met was found in NSCLC tissues. PDGFR-βwere high expressed in the cells of tumor Stroma. In addition, the expression was significantly associated to LMVD, TNM stage and lymph nodes metastasis. Our study suggested that PDGF-BB and HGF play an important role in promoting lymphangiogenesis and lymph node metastasis. Therefore, PDGF-BB and HGF might serve as new targets for diagnosis and treatment in NSCLC, and study of those relevant inhibitors may make great good to patients with lymphatic and distal metastasis in NSCLC. |
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