The Expression And Clinical Significance Of MicroRNA-31 In Lung Cancer

Background and ObjectivesLung cancer is a malignant tumor of the highest morbidity and mortality. According to the statistics, there were about 1 100 000 patients died in 2000. The number of incidence is showing an increasing tendency yearly. Because the symptoms of early stage lung cancer is not obviously and lacking of specific biomarkers and tools for screening and early diagnosis, so most patients are diagnosed in advanced stages. And missing the opportunity of best therapy, just received the palliative cares. The 5 years survival rates remains as low as about 15%, making it the highest mortality disease of human.miRNAs are approximately 21-25 nucleotide(nt) RNAs that could recognize the specified targeted mRNAs, and could regulate gene expression negatively by promoting the degradation of mRNA and/or inhibiting the translation processes, involved various biological processes, such as cellular differentiation, proliferation, metabolism, resistance and cell death. Different miRNAs also functioned as pro- or anti-oncogenes. The abnormal expression of miRNAs have reported to correlate with the tumorigenesis. The reseaches have identified that miR-31 plays an important role in the development of lung cancer. So detected the expression profiles of miR-31 in lung cancer tissues and the adjacent normal tissues, the serum in lung cnacer patients and the normal control people, to reveal the relations between the expression profiles and the diagnosis, the size of tumor, the metastasis of lymph nodes, smoking and stages. It is helpful to understand the mechanisms of lung cancer, and offer the guidelines of the early screening, the early diagnosis.Materials and Methods1 Specimen collectionThe sixty-four specimens of lung cancer tissues and the adjacent normal tissues, 74 cases serum of surgey lung cancr,73 cases serum of IV stages lung cancr were collected from Henan cancer hospital between 2008.12- 2010.9. The serum of 114 cases normal control group were collected from Henan cancer hospital, the people hospital of henan province, the affiliated Huaihe hospital of Henan university. The human lung cancer cell line 95D with high metastatic potential are cultured by State Key Laboratory of Molecular Oncology of Chinese Academy of Medical Science. The non-small cell lung cancer cell line A549 and the drug-resistant A549 cell line were provided by Clinical Pharmacology Institude of Basic medical college of zhengzhou university.The histological classification was according to the standard of WHO (2004,4th version), and the TNM stages was according to International Union Against Cancer (UICC,2009, the 7th version).2 MethodsFirstly to homogenate the tissues, then the steps are same with the extraction of serum. Use Trizol to extract the total RNA. Next adding the PolyA tails, Reverse-Transcription PCR. Detected the expression of miR-31 by real time RT-PCR.3 Statistics analysisStatistical analysis was executed by SPSS17.0 software, a value less than 0.05 was considered as significance. Results1 The expression of miR-31 in tissuesIn 64 cases lung cancer tissues, the expression of miR-31 is higher than the adjacent normal tissues, the relative expression is 5.89 folds compared to normal tissues, P< 0.001. In the early stage of I and II, contrast to the normal tissue, the significance were 0.002 and 0.005 respectively. Comparaed to the diameter> 3cm, the relative expression of miR-31 is 3.17 folds to the group of diameter≤3cm, P=0.045. There are no signifecant differences of miR-31 expression between the lymph nodes metastasis positive group and negative group that identified by pathology, P=0.703. The miR-31 relative expression exist difference inⅠ,Ⅱ,Ⅲstages, but no statistics significance,P=0.413.2 The expression of miR-31 in serumIn the stages ofⅠ-Ⅳlung cancer patients, the relative expression is 7.66 folds comparaed to the control group. P<0.001. In the early stage ofⅠandⅡ, contrast to the control group, the significance were 0.03 and< 0.001 respectively. In the serum of surgery patients, the relative expression of diameter>3cm is higher than the group of diameter≤3cm significantly, P=0.027; The lymph nodes metastasis positive group is 1.17 folds comparaed to the negative group, P=0.245. There is no significance betweenⅠ-ⅢandⅣstages, P=0.268.3 The expression of miR-31 in NSCLC cell linesIn human lung cancer cell line 95D with high metastatic potential, the non-small cell lung cancer cell line A549 and the drug-resistant A549 cell line, the expression of miR-31 are 0.043.0.072,0.131 respectively.4 SmokingIn tissue specimens of 45 cases of smokers and 19 cases of nonsmokers, the miR-31 expression is higher in smokers than non-smokers, with 3.06 folds,P=0.033.5 The relationship of miR-31 with surgey In 74 cases patients that accepted surgeries, the miR-31 expression after the surgery was 1.45 folds comparaed before surgery, P=0.772. In adenocarcinoma, squamous cell carcinoma, SCLC, the significance were 0.18,0.488,0.776 respectively.Conclusions1. In serum, miR-31 may be a lung cancer biomarker, and is valuable in the early screening and early diagnisis of lung cancer.2. miR-31 maybe participated in the development of lung cancer, and may be correlated with the tumor size.3. miR-31 may be not promoted the metastasis of lung cancer.4. miR-31 maybe as a intermediary molecular and involved in the process of the tumorigenesis of lung cancer caused by smoking.