Evaluation of the role of miRNA-155 in Lung Cancer

Abstract

Lung cancer is a public health priority worldwide. The prevalence of lung cancer is second only to that of prostate cancer in men and breast cancer in women. It is the leading cause of cancer-related mortality in both men and women throughout the world. In Egypt, it is the second most common malignancy after bladder cancer in men and breast cancer in women and the second most common cause of death in men. There is an obvious need to diagnose lung cancer using novel non-invasive and sensitive biomarkers in order to accurately identify the high risk population for optimal treatments and minimize unnecessary invasive procedures. miRNAs are a class of short (~22 nt), ncRNA molecules which play a central role in sequence specific post-transcriptional gene attenuation. miRNAs are also capable of providing important information on the aggressiveness of the disease and of predicting response to specific treatment. Alterations in miRNA expression have been observed in various solid tumors, including lung cancer and could potentially be used for cancer diagnosis, prognosis and response to treatment. Some key miRNAs are frequently dysregulated in lung cancer, and contribute to lung cancer development and progression by acting as oncogenes or tumor suppressor genes. Besides that, tumor-specific miRNAs have enormous advantages over conventional cancer detection methods, including high stability, easy accessibility, and noninvasiveness. miRNA-155, one of the best characterized miRNAs, is significantly up-regulated in lung cancer tissues, plasma and sputum, and could serve as a promising marker for the diagnosis and poor prognosis of lung cancer. In this regard, the aim of the present study was to evaluate miRNA-155 in patients of lung cancer and non-cancerous lung lesions using a new valid non invasive technique to find a novel biomarker that could have potential possible role in diagnosis and prognosis of patients with lung cancer. This study was conducted on (30) patients classified into two groups according to their diagnosis. Group (1) included (15) newly diagnosed lung cancer patients (mean age was 71.33). Group (2) included (15) patients with high risk for lung cancer served as control group (mean age was 45.8). This study was conducted on exhaled breath condensate from 30 Egyptian male and female patients attending the Pulmonary Medicine Department at Ain Shams University Hospitals. miRNA-155 expression level (RQ value) was measured in exhaled breath condensate of patients of the study groups using quanitative real time PCR technique. The data were normalized using the SNOR 72 as reference control. Then the results were calculated and statistically analyzed by the SPSS software version 20. The use of quanitative real time PCR technique in exhaled breath condensate samples revealed a highly significant increase in miRNA-155 expression level (RQ value) in malignant group on comparison with control groups. In addition, the present study showed a significant difference in miRNA-155 expression (RQ value) as regards the age and smoking status of lung cancer patients being highest in elder heavily smokers and lowest in younger lightly smokers. Moreover, this study demonstrated significant higher levels of miRNA-155 expression (RQ value) in positive family history patients and metastatic cases than negative family history patients and non-metastatic cases.