The Relationship of Mir-21, Mir-126 and Mir-205 to P-Glycoprotein, Mrp1 and Lrp/Mvp in Non-Small Cell Lung Cancer

Protein transporters P-gp, MRP1 and LRP/MVP participate in the emergence of multidrug resistance (MDR) in non-small cell lung cancer (NSCLC). Their expression is post-transcriptionally regulated by microRNAs (miRNAs). Dysregulation of miR-21, miR-126 and miR-205 is often found in NSCLC. The aim of this study was to determine whether the level of miRNAs is associated with expression of the above mentioned proteins involved in MDR and whether they can be used as prognostic and diagnostic markers. We analysed miR-21, miR-126 and miR-205 in various histological subtypes of NSCLC. Their expression was then correlated with clinico-pathological characteristics, such as progression free survival (PFS), overall survival (OS) and different histological subtypes of NSCLC and, with expression of P-gp, MRP1 and LRP/MVP. We found no significant relationship between miR-21 and miR-126 expression and clinico-pathological parameters. However, miR- 205 levels were significantly increased in squamous cell carcinomas (p<10-6) compared with other histological subtypes of NSCLC. Additionally, the level of miR-205 inversely correlated with P-gp expression in NSCLC patients (p=0.03). Results of this study suggest that miR-205 could be used as a diagnostic marker and its downregulation may indicate the emergence of P-gp mediated drug resistance in NSCLC patients.