Purpose The microRNA-34b/c (miR-34b/c) has been considered a tumor suppressor in different tumor types and it is a known transcriptional target of the tumor suppressor gene TP53. The main objectives of this study were to investigate the clinical implications of miR-34b/c methylation in early stage lung adenocarcinoma (AC) patients and to determine the functional role of miR-34b/c re-expression in lung AC cell lines. Experimental Design Aberrant methylation and expression of miR-34b/c were assessed in 15 lung AC cell lines and a cohort of 140 early stage lung AC. Lung AC cell lines were transfected with miR-34b/c and the effects upon cell proliferation, migration, invasion and apoptosis were investigated. Results Aberrant methylation of miR-34b/c was detected in 6 (40%) of 15 lung AC cell lines and 64 out of 140 (46%) primary lung adenocarcinomas. Expression of miR-34b/c was significantly reduced in all methylated cell lines and primary tumors, especially in those harboring a TP53 mutation. Patients with high levels of miR-34b/c methylation had significantly shorter disease-free survival and overall survival as compared to patients with unmethylated miR-34b/c or low level of miR-34b/c methylation. Ectopic expression of miR-34b/c in lung AC cell lines decreased cell proliferation, migration and invasion. Conclusions Epigenetic inactivation of miR-34b/c by DNA methylation has independent prognostic value in early stage lung AC patients with surgically resected tumors. Re-expression of miR-34b/c leads to a less aggressive phenotype in lung AC cell lines.

<p>PDF file 74K, Kaplan-Meier plot of DFS according to miR-34b/c methylation level in 97 stage I lung AC patients</p>

<p>PDF file 167K, Restoration of miR-34b/c expression by treating lung AC cell lines with 5-Aza-2'-Deoxycytidine</p>

<p>PDF file 68K, Frequency of miR-34b/c promoter methylation and correlation of tumors miR-34b/c expression with methylation status</p>