P90: Dynamic changes of circulating microRNA expression in response to the lung cancer combined therapy

Abstract

Background The analysis of circulating tumor nucleic acids (DNAs and RNAs) in the blood seems to be a promising approach for the development of the low-invasive methods of tumor detection, valuable for clinical practice. Detection of oncogenic and tumor suppressor miRNAs in the blood plasma/serum is evidence of their participation in pathogenesis and suggest the possibility of their use as tumor markers and targets for therapy. Thus, the determination of expression level of tumor-associated miRNAs in plasma can lead to significant progress in understanding the tumor development and treatment. Aim Estimation the changes in expression level of miRNAs (miR-19b, miR-25, miR-125b, miR-126, miR-205) in blood plasma from lung cancer patients during combined therapy and to estimate their value as disease monitoring markers. Materials and methods Blood samples were taken from patients (n = 23) with non-small cell lung cancer treated at the Tomsk Cancer Research Institute. These samples were stabilized and fractionated into plasma and blood cells. MicroRNA was isolated from blood plasma using single-phase phenol-free extraction protocol and purified on silica-based spin columns (BioSilica Ltd, Novosibirsk, Russia). Concentration of five above mentioned miRNAs was measured by quantitative RT-PCR and normalized to miR-16 using dCt method. Results In this study we analyzed the dynamic expression changes of circulating DNA in blood plasma from lung cancer patients during the combined therapy. Circulating miRNAs were isolated from plasma samples of non-small cell lung cancer patients before treatment, within 30 days after completing chemotherapy and 15 days after surgery, by using developed methodological approach. In case of miR-19b and miR-125b analysis was found that the miRNA expression level correlates with clinical response to chemotherapy and surgery. Increasing level of miR-19b and decreasing level of miR-125b were associated with therapeutic response. Using Repeated measures ANOVA analysis we demonstrated that the miR-19b and miR-125b expression levels changes throughout three check-up points during the combined treatment are characterized by the significant cubic trend (P = 0.00284 and P = 0.029, respectively). Changes of miRNA-126 expression level during post-treatment follow-up were not characterized by the definite trend and not correlated with changes of other miRNAs expression level. It was shown the significant correlation between miRNA-25 and miRNA-205 expression levels, but was not found the trend of these miRNAs level changes. Conclusion The clinical utility of the circulating miR-19b and miR-125b expression analysis from this study remains to be validated in large cohorts of patients with different histological types of tumors, at the different stage of disease and outcomes. One of the criteria for inclusion in the group must be susceptibility and/or resistance to therapy. The research has been carried out with support of the grant from the Russian Science Support Foundation 14-04-01881 , Post-doctorate program in TPU.