Tumor Hypoxia And Angiogenesis In Lung Cancer

Background: Lung cancer is one of the highest incidence and mortality in all kinds of caner in the world,and it is the most common cause of death due to cancer. Recently,the incidence of lung cancer is rising step by step,especially in China. Non-small cell lung cancer (NSCLC) accounts for more than 75% of pulmonary carcinomas. Treatment of patients with NSCLC is a particular challenge in oncology, because more than one third of patients have distant metastases at diagnosis, allowing only palliative treatment. Tumor growth, invasion and metastasis are infuenced by a variety of factors, and most important of these factors are tumor hypoxia and angiogenesis. Carbonic anhydrases IX(CAIX) is considered as an reliable marker of tumor hypoxia. Considerable interest has been focused on angiogenic factors in the field of lung cancer. Angiogenesis represents the formation of new blood vessels from existing vasculature. Neovascularisation is a requirement for growth of solid tumours beyond 1~2 mm in diameter. The angiogenic process is a balance between stimulatory and inhibitory factors. The pro-angiogenic stimuli may be released by the tumour, stromal and inflammatory cells, by the extracellular matrix, or by the endothelial cells themselves. Tumour cells secrete or induce the release of growth factors which stimulate migration and proliferation of endothelial cells. Furthermore, these factors may be involved in capillary morphogenesis or release of proteolytic enzymes.Vascular endothelial growth factor (VEGF) and endostatin are two of the most potent factors involved in angiogenesis. Clinical and experimental studies demonstrated significantly elevated serum and tissue levels of VEGF in patients with lung cancer, implicating VEGF in the pathogenesis of this disease.Pleural effusion often remains a diagnostic problem after the biochemical and cytological analysis of the pleural fluid. In most series, malignancy is the most common cause of pleural exudates. Pleural effusions are common and important complications that may be produced by a wide variety of diseases especially malignancies. It is important to elucidate the precise etiology of the pleural effusion especially to discriminate benignfrom malignant effusions. Pleural effusion can present a challenging diagnostic problem which remains unsolved even after clinical and laboratory evaluation. The differential diagnosis is diverse, but most common causes include malignancy, tuberculous, congestive heart failure and empyema-related effusion.VEGF is the most potent and endothelial specific angiogenic growth factor and it plays a pivotal role in formulation of PE, which has proved to be a useful marker to differentiate malignancy from a benign origin in exudative pleural effusions. Differing VEGF levels were found in malignant and tuberculous pleural effusions, implying a varying degree of influence on the process of fluid accumulation in the pleural space in different disease states. Tumor spreading has been associated with angiogenesis, a process tightly controlled by balance between angiogenesis factor and angiogenesis inhibitor. Pleural angiogenesis, increased vascular permeability, and leakage play a key role in the development of exudative pleural effusions. Although many known angiogenesis-inducing factors including VEGF are present within pleural fluid and these high levels are thought to induce vascular permeability, the relative levels of antiangiogenic factors such as endostatin in PE have been reported only by few studies. Endostatin induces endothelial cell apoptosis and inhibits the proliferation and migration of some types of endothelial cells, and in vivo it has potent anti-angiogenic activity. Although serum levels of endostatin have extensively been studied in patients with malignant diseases, endostatin in pleural effusion has not been fully evaluated. The respective determination of the concentrations of VEGF and endostatin has been proved helpful in differentiating between pleural effusion of malignant and tuberculous or benign origin.The relationship between smoking and lung cancer is well understood, but the mechanism of the close association is not definitely known. However, heavy smoking has been demonstrated to affect serum VEGF levels. Therefore, we intend to implore whether there is an imblance of angiogenesis in sera of heavy smoking subjects.The present study is divided into three parts as follows. Part I Expression and significance of carbonic anhydrases IX and vascular endothelial growth factor in non-small cell lung cancerObjective: To explore the expression and role of carbonic anhydrases IX (CAIX) and vascular endothelial growth factor (VEGF) in non-small cell lung cancer. Methods: The expression of CAIX and VEGF in 86 pathologically diagnosed non-small cell lung cancer and normal lung tissue was detected using immunohistochemical technique. The immunostaining data was compared with clinical pathological parameters. Results: Among the 84 specimen of malignant cases, expression of CAIX was detected in 60(71.4%) and VEGF in 56(66.7%). Both CAIX and VEGF were expressed maximally on the luminal surface of tumors and around regions of necrosis in tumors. No positive staining of CAIX and VEGF were found in normal lung tissue. The expressions of CAIX and VEGF were related to tumor size, clinical stage and status of lymphatic node. There was an association between CAIX and VEGF(r=0.405, P<0.01). Conclusion: The hypoxia and angiogenesis are important markers of carcinoma. CAIX and VEGF were involved in the tumorgenesis and progression of non-small cell lung cancer. CAIX and VEGF might play synergetic roles in invasion and metastasis of the disease.Part II The detection of vascular endothelial growth factor and endostatin in malignant and tuberculosis pleural effusionsObjective: To explore changes and clinical significance of VEGF and endostatin in malignant and tuberculosis pleural effusions. Methods: Eighty-two effusion samples, 42 from patients with lung cancer and 40 from patients with tuberculosis, were analyzed. VEGF and endostatin concentrations were determined by enzyme linked immunoabsent assay (ELISA) or competitive enzyme immunoassay. And sensitivity, specificity and accuracy for diagnosing the malignant pleural effusion were compared. Results: The concentrations of VEGF and endostatin were significantly higher in malignant than those in nonmalignant effusions(P both <0.01). For VEGF, sensitivity, specificity and accuracy to diagnose the malignant pleural effusion were 57.5%, 81.0%, and 69.5%, respectively. Similarly, for endostatin, the sensitivity, specificity and accuracy to diagnose the malignant pleural effusion were 50.0%, 90.5%, and 70.7%, respectively. Unexpectedly, when VEGF/endostatin ratio was analysed, sensitivity, specificity and accuracy were significantly rising up to 97.5%, 90.5%, 93.9%. Conclusion: These findings suggest that elevated levels of VEGF and endostatin in pleural effusions are helpful to make the diagnosing of malignant pleural effusions and differentiate malignant from tuberculosis pleural effusions, especially VEGF/endostatin ratio can increase sensitivity, specificity and accuracy.Part III Changes of levels of sera vascular endothelial growth factor and endostatin in smokersObjective: To explore the changes and clinical significance of levels of serum VEGF and endostatin in smokers. Methods: In a case-control study, levels of serum VEGF and endostatin were determined in 82 smokers with lung cancer, 82 pair-matched smokers without lung cancer and 20 healthy non-smokers by enzyme linked immunoabsent assay (ELISA) or competitive enzyme immunoassay. Results: The levelss of serum VEGF in smokers with lung cancer (16.1±7.9ng/L) were markedly higher than those in the other two groups (both P <0.01). And the levels of serum VEGF in smokers without lung cancer were significantly higher than those in healthy nonsmokers (P <0.05). The levels of serum endostatin in smokers with lung cancer were significantly higher than those in healthy nonsmokers (P <0.01), but were not significantly different from those in smokers without lung cancer (P >0.05). Notably, the ratio of endostatin to VEGF in smokers with lung cancer (1.3±0.5) was significantly lower than that in other two groups (both P <0.01). However, there was no significant difference in it between smokers without lung cancer and healthy nonsmokers (P >0.05). Conclusion: These findings suggest that smoking may result in imbalance of levels of serum endostatin and VEGF leading to tumorigenesis. The ratio of endostatin to VEGF can be considered as an early diagnostic markers of lung cancer in smokers. Periodic determination of levels of serum VEGF and endostatin as well as the ratio of endostatin to VEGF is of clinical importance.