Promoter methylation study of the H37/RBM5 tumor suppressor gene from the 3p21.3 human lung cancer tumor suppressor locus

Abstract

Loss of heterozygosity (LOH) at chromosome 3p21.3 is one of the most prevalent genetic disturbances occurring at the earliest stage of tumor development for a wide variety of human cancers, culminated in lung cancer. The 19 genes residing at 3p21.3 have been vigorously characterized for tumor suppressor activity and gene inactivation mechanism because of their potentially significant merits of clinical applications. Many of these 19 genes have been shown to manifest various growth inhibitory properties, however none of them are inactivated by coding mutations in their remaining allele as in the Knudson's two- hits hypothesis. Thus far the most prevailing, alternative gene inactivation mechanism known for the 3p21.3 TSGs is epigenetic silencing by promoter hypermethylation. Previously, we have focused our investigation on one of the 19 genes at 3p21.3, H37/RBM5, and demonstrated its tumor suppressor activity both in vitro and in vivo as well as its mRNA/protein expression loss from the remaining allele in a majority of the primary lung tumors examined. The current study tested our hypothesis that the H37 inactivation in primary lung tumors may, as seen in most of the other 3p21.3 TSGs, be due to hypermethylation in its promoter CpG islands. Contrary to this most plausible postulation, however, we found no evidence of epigenetic gene silencing for the H37 TSG. Here we suggest some of the possible, further- alternative means of the H37 gene expression loss in tumor, including defects in transcription and post-transcriptional/translational modifications as well as mechanisms related to haploinsufficiency.

The two single nucleotide polymorphisms in the H37/RBM5 tumour suppressor gene at 3p21.3 correlated with different subtypes of non-small cell lung cancers

“…Consistently, H37 triggers mitochondrial apoptotic pathways downstream of Bax, in a p53-independent manner, which include breakdown in the mitochondrial membrane potential, cytochrome c release into cytosol, and enhanced caspase-9 and caspase-3 activities [11]. Further, as compared with adjacent normal tissue, our findings show reduced expression in primary lung cancers of H37 transcript and protein in 9 of 11 (82%) and 46 of 62 (73%) samples, respectively [12], although the H37/3p21.3 LOH genomic status for these samples was unknown. The involvement of H37 in malignancy has been also reported by other investigators for a variety of cancer types.…”

“…Briefly, 5 μg of total RNA was primed with 500 ng of oligo(dT) [12][13][14][15][16][17][18] in a total of 12 μl reaction volume for 10 min. at 70°C followed by quick chill on ice.…”

RNA-binding motif protein 5 negatively regulates the activity of Wnt/β-catenin signaling in cigarette smoke-induced alveolar epithelial injury

“…Previous studies suggest that frequently reduced RBM5 levels exist in different types of tumors including breast cancer (25), schwannoma (26), and ~75% of primary lung cancers (27). We previously reported that the protein levels of RBM5 are lower in NSCLC compared with non-tumorous tissues (13).…”

Alternative pre-mRNA splicing regulation in cancer: pathways and programs unhinged

“…Loss of heterozygosity at this locus occurs in 95% of small-cell lung cancer (SCLC), as well as 70% of non-SCLC (Sutherland et al 2010). Consistent with a role as a tumor suppressor, RBM5 (also known as LUCA-15 and H37) was later shown to be down-regulated in a high proportion of lung cancers (Oh et al 2002). RBM5 was also one of nine genes down-regulated as part of a ''metastatic signature'' identified by microarray (Ramaswamy et al 2003).…”