The aim of the study was the analysis of genetic alterations in tumor and adjacent tissue to determine the FC size and to reveal associations with clinico-morphological features of patients.
The study group included 135 patients with NSCLC. From each patient 4 FFPE samples were analyzed: tumor, adjacent normal lung tissue at 2, 5, 10 cm. LOH/MSI analysis was evaluated by PCR using 7 microsatellite loci. Promoter hypermethylation in genes RASSF1A FHIT, DAPK1, CDH1, CD44, TIMP3, MGMT was investigated by methyl-sensitive PCR. The expression levels of miRNAs let-7a, miR-155, miR-205 were measured by real-time PCR.
Our results demonstrated that LOH/MSI occurs only in tumor while promoter hypermethylation occurs also in adjacent tissue at 2, 5 cm, but not at 10 cm. The downregulation of let-7a, miR-155 in adjacent tissue is lower than in tumor. The levels of investigated miRNAs in adjacent tissue vary depending on tumor differentiation – in patients with differentiated tumors it is higher than in the group with poorly differentiated tumors.
We postulate that FC size in NSCLC is at least 5 cm from tumor and includes only epigenetic but not structural (LOH/MSI) alterations. The evaluation of epigenetic changes in adjacent tissue (e.g., surgical margins) can potentially be used for postsurgical prognosis.