Tobacco exposure results in specific oncogene and tumor suppressor gene alterations in lung epithelial cells that often lead to lung cancer development. Activating point mutation of the K‐ras proto‐oncogene is one of the most frequently occurring genetic changes found in lung cancer both in active and former smokers. Understanding how K‐ras mutations mediate the malignant phenotype may yield more effective prevention and diagnosis strategies to be applied to individuals at elevated risk for lung cancer. Micro RNAs are a class of short (19–24 nucleotides) noncoding RNAs that play a critical role in posttranscriptional gene regulation. A rapidly developing literature supports an important role for micro RNAs in the regulation of lung carcinogenesis and tumor progression. In order to better understand the role of micro RNAs in the K‐ras‐mutated bronchial epithelium, we utilized hTERT‐ and Cdk4‐immortalized human bronchial epithelial cells (HBEC) expressing mutant KrasV12. We next generated the micro RNA profile (TaqMan miRNA array v.2, Applied Biosystems, Foster City, CA), gene expression profile (Affymetrix U133 plus 2 array), and protein expression profile (50‐plex inflammatory marker panel) of the K‐ras mutated and vector control HBECs. We found that the micro RNA miR‐125a‐3p was significantly suppressed in K‐ras‐mutated HBECs compared to the vector control cells. We then evaluated basal expression of miR‐125a‐3p in both HBECs and NSCLC cell lines containing mutated K‐ras by real time RT‐PCR. Both K‐ras‐mutated HBECs and NSCLC cell lines expressed low levels of miR125a‐3P. In order to further evaluate the role of miR‐125a‐3p, we stably expressed this micro RNA in K‐ras‐mutated HBECs. Our results indicate that miR‐125a‐3p expression down‐regulates several tumor‐promoting factors, including Gro‐α, HGF, VEGF, GM‐CSF, and G‐CSF. Further studies revealed that suppression of Gro‐α and HGF, but not VEGF, is regulated at the level of mRNA expression. Overexpression of miR‐125a‐3p suppressed proliferation of the K‐ras‐mutated HBECs but did not alter the proliferation of the vector control HBECs. Based on these findings, we anticipate that loss of miR‐125a‐3p may have a broad impact in the bronchial epithelium that harbors K‐ras mutations, potentially regulating cellular proliferation, angiogenesis and inflammation. Further exploration is required to evaluate the role of this micro RNA and its downstream effects as potential screening tools and targets of prevention and therapy in the setting of K‐ras‐mutated lung cancers.

Citation Information: Cancer Prev Res 2010;3(1 Suppl):A31.

Copyright © January 7, 2010, American Association for Cancer Research
2010