The Expression Of Lunx MRNA In Peripheral Blood Of Patients With NSCLC By RT-PCR And Its Clinical Significance

Lung cancer is the leading cause of cancer death in developing countries. It is one of the most frequent neoplasias in human and the prognosis is closely related to the metastatses of tumor cells. Approximately 40% patients of lung cancer already have distant metastases on hospital admission. Lung cancer cells usually spread via the bloodstream and/or lymphatic system to form a micrometastatic deposit in distant organs. Therefore, the entrance of cancer cells into bloodstream is the earlier period of distant metastasis. The presence of cancer cells in circulation demonstrates that the primary cancer has higher tendency to metastasize.Non-small cell lung cancer (NSCLC) is the most common cause of cancer-related death among men and women . Each year there are 170000 new cases and approximately 160000 deaths due to NSCLC . Standard therapies for patients with NSCLC include surgery, chemotherapy, and radiation therapy. The stage of disease dictates the choice of therapy. Its current staging system for lung cancer uses the International Union Against Cancer (UICC) TNM system, and its goal is to classify patients into groups based on the extent of disease. Thus, surgery is considered primary therapy for patients with early stage of the disease, while non-surgical therapy is recommended for patients with advanced stage of disease. Reliable detection of metastatses disease is therefore critical for appropriate staging and treatment of patients with NSCLC. Indeed, recent studies of sensitive assays for detection of rare disseminated lung cancer cells have shown that detection of occult metastases by immunocytology or immunohistochemistry in lymph nodes or bone marrow aspirates is a reliable predictor of poor prognosis .The poor prognosis is due largely to lack of sufficient screening and early diagnostic tools to physicians. Currently in clinic the screening and early diagnosis of lung cancer relies mainly on chest X-ray, low-dose computed tomography, bronchoscopy, sputum cytology, and tumor markers including carcinoembryonic antigen (CEA), cytokeratin-19 fragments (Cyfra21-1), carbohydrate antigen 19-9 (CA19-9), squamous cell carcinoma antigen (SCCAg) and neuron-specific enolase (NSE), etc.All these methods, however, lack adequate sensitivity and/or specificity.Due to the lack of diagnostic tools for early detection and efficient treatment for advanceed disease, the prognosis of lung cancer is still poor, with less than 15% surviving in 5 years after diagnosis.Iwao et al. have isolated a novel human lung-specific gene, Lunx (lung specific X protein), by differential-display mRNA analysis. They showed that Lunx was specifically expressed in normal lung tissues and non-small cell lung cancer (NSCLC) tissues but not in other normal or tumor tissues. Lunx couldn't be detected in normal mesenchymal tissues (lymph nodes, bone marrow, blood). The full-length cDNA of Lunx mRNA contains 1015 nucleotides including an open reading frame of 768 nucleotidesencoding 256 amino acids of m.w. 26.7 kDa. Lunx gene locate at chromosomal region 20 p11.1-q12. Lunx was expected to become a specific molecular marker for detecting lung cancer micrometastasis.Reverse transcription polymerase chain reaction (RT-PCR) has been recognized as the method with the highest sensitivity for detection of micrometastatic disease, allowing identification of one cancer cell in 106 to 107 normal cells. Detection of metastatic cancer cells by RT-PCR is based on the fact that cancer cells continue to express genes (or markers) that are specific to the tissue from which they originate, but are not expressed in tissue compartments that frequently harbor metastatic foci, such as lymph nodes and bone marrow. RT-PCR-based tumor cell detection assays often yield higher sensitivity than conventional immunohistochemistry.We detected lung cancer micrometastases in peripheral blood by using specific of Lunx mRNA reverse transcription-polymerase chain reaction (RT-PCR). We investigated the relationship between clinical characteristics and micrometastasis expression of patients with NSCLC, to evaluate clinical significance for diagnosis of lung cancer micrometastases. We detected Lunx mRNA expression of in peripheral blood of 54 patients with lung cancer between August 2005 and March 2007. Blood samples were taken from an antecubital vein to detect circulating tumor cells in the peripheral blood of NSCLC patients. Tumor cells were first enriched from peripheral blood. in patients with lung cancer prior to surgery. As a control, blood samples were taken from an antecubital vein in 50 patients with pulmonary benign diseases and 25 health people and organization samples were taken from tumor of NSCLC.The result of our investigation indicates that Lunx mRNA is a sensitive and specific molecular marker for micrometastases detection of lung cancer. RT-PCR amplification of Lunx mRNA is an sensitive and specific means to detect early micrometastases for patients with lung cancer. The positive rate of Lunx mRNA in peripheral blood of NSCLC had a relationship with histopathology types , cell type or TNM system. No significant correlation was found between different sex,age,history of smoking and position of tumor. This may partly help clinicians to comprehend the fact that some patients with earliy lung cancer suffered relapse and distant metastasis shortly.