Search

The chromatin remodeling complex SWI/SNF is an important epigenetic regulator that includes one Brm or BRG1 molecule as catalytic subunit. Brm and BRG1 do not function identically, so this complex can regulate gene expression either positively or negatively, depending on the promoter to which it is recruited. Notably, Brm attenuation due to posttranscription suppression occurs often in human tumor cells, in which this event contributes to their oncogenic potential. Here, we report that the 3'-untranslated region of Brm mRNA has two sites that are efficiently targeted by the microRNAs miR-199a-5p and -3p, revealing a novel mechanism for modulation of Brm-type SWI/SNF activity. Computational mapping of the putative promoter region of miR-199a-2 (miPPR-199a-2) has defined it as the major contributing genetic locus for miR-199a-5p and-3p production in these tumor cell lines. We validated this predicted region by direct promoter analysis to confirm that Egr1 is a strong positive regulator of the miR-199a-2 gene. Importantly, we also showed that Egr1, miR-199a-5p, and miR-199a-3p are expressed at high levels in Brm-deficient tumor cell lines but only marginally in Brm-expressing tumor cells. Finally, we also obtained evidence that Brm negatively regulates Egr1. Together, our results reveal that miR-199a and Brm form a double-negative feedback loop through Egr1, leading to the generation of these two distinct cell types during carcinogenesis. This mechanism may offer a partial explanation for why miR-199a-5p and -3p have been reported to be either upregulated or downregulated in a variety of tumors., (©2010 AACR.)

Using a genome-wide cDNA microarray to search for genes that were specifically up-regulated in non-small cell lung cancers (NSCLC), we identified an abundant expression of neuromedin U (NMU) in the great majority of lung cancers. Immunohistochemical analysis showed a significant association of NMU expression with poorer prognosis of patients with NSCLC. Treatment of NSCLC cells with short interfering RNA against NMU suppressed its expression and inhibited the growth of the cells; on the other hand, the induction of exogenous expression of NMU conferred growth-promoting activity and enhanced cell mobility in vitro. We found that two G protein-coupled receptors, growth hormone secretagogue receptor 1b and neurotensin receptor 1, were also overexpressed in NSCLC cells, and that a heterodimer complex of these receptors functioned as an NMU receptor. The NMU-receptor interaction subsequently induced the generation of a second messenger, cyclic AMP, to activate its downstream genes including transcription factors and cell cycle regulators. Treatment of NSCLC cells with short interfering RNAs for growth hormone secretagogue receptor or neurotensin receptor 1 suppressed the expression of those genes and the growth of NSCLC cells. These data strongly implied that targeting the NMU signaling pathway would be a promising therapeutic strategy for the treatment of lung cancers.

We investigated gene expression profiles of non-small cell lung carcinomas (NSCLC) to screen candidate molecules that might be useful as diagnostic markers or for development of novel molecular-targeting therapies. Here we report evidence that a member of the armadillo protein family, plakophilin 3 (PKP3), is a potential molecular target for treatment of lung cancers and might also serve as a prognostic indicator. We documented elevated expression of PKP3 in the great majority of NSCLC samples examined. Treatment of NSCLC cells with small interfering RNAs of PKP3 suppressed growth of the cancer cells; on the other hand, induction of exogenous expression of PKP3 conferred growth-promoting activity on COS-7 cells and enhanced their mobility in vitro. To investigate its function, we searched for PKP3-interacting proteins and identified dynamin 1-like, which was also activated in NSCLC. In addition, a high level of PKP3 expression was associated with poor survival as well as disease stage and node status for patients with lung adenocarcinoma, suggesting an important role of the protein in development and progression of this disease. As our data imply that up-regulation of PKP3 is a frequent and important feature of lung carcinogenesis, we suggest that targeting the PKP3 molecule might hold promise for development of a new therapeutic and diagnostic strategy for clinical management of lung cancers.