RASSF1A Site-Specific Methylation Hotspots in Cancer and Correlation with RASSF1C and MOAP-1

Abstract

Epigenetic silencing of RASSF1A is frequently observed in numerous cancers and has been previously reported. The promoter region of RASSF1A is predicted to have 75 CpG sites, and very few studies demonstrate how the methylation of these sites affects expression. In addition, the expression relationship between RASSF1A and its downstream target, modulator of apoptosis 1 (MOAP-1), is poorly understood. In this study, we have explored the mRNA expression of RASSF1A, MOAP-1 and the well-characterized splice variant of RASSF1, RASSF1C, in cancer cell lines and primary tumors. We confirmed that the RASSF1A promoter is robustly methylated within a 32-CpG region in solid tumors and results in lower mRNA expression. The MOAP-1 promoter contains ~110 CpG sites, but was not found to be methylated in cancer cell lines when 19 predicted CpG sites were explored. Interestingly, MOAP-1 mRNA expression positively correlated with RASSF1A expression in numerous cancers, whereas RASSF1C expression remained the same or was increased in cell lines or tissues with epigenetic loss of RASSF1A. We speculate that MOAP-1 and RASSF1A may be more intimately connected than originally thought, and the expression of both are warranted in experimental designs exploring the biology of the RASSF1A/MOAP-1 molecular pathway.

RIPK2: New Elements in Modulating Inflammatory Breast Cancer Pathogenesis

“…Our research group has demonstrated that RASSF1A can restrict NOD2-RIPK2 association in intestinal cells to subsequently interfere with the ability of RIPK2 to drive NF-κB-directed molecular inflammation [ 43 ]. Epigenetic analysis via pyromark sequencing of 32 CpGs of the RASSF1A promoter region revealed that IBC patients have a higher percentage of CpG methylation in comparison to breast reduction surgery (BRS) patients (normal control) [ 67 ]. Similar to most solid cancers, high methylation of RASSF1A in IBC patients correlates with loss of expression [ 67 ].…”

PNMA family: Protein interaction network and cell signalling pathways implicated in cancer and apoptosis

“…In addition, MOAP-1 may be regulated by phosphorylation as several phosphorylation sites have been identified in MOAP-1 protein sequence [29]. Analysis of MOAP-1 gene led to the identification of CpG island located near the gene promoter of MOAP-1, pointing to the possibility that MOAP-1 might be regulated through hyper-methylation of its gene promoter [106]. Other than gene expression regulation, pro-apoptotic activity of MOAP-1 was reported to be regulated by members of PNMA family.…”

The role of the NORE1A tumor suppressor in Oncogene-Induced Senescence

“…RASSF1A, arguably the most frequently silenced tumor suppressor in human cancer (31,32,34), is another member of the RASSF family that plays an important role in β-Catenin signaling (32). Studies by Ram and colleagues showed that RASSF1A interacts with β-TrCP, and that the down-regulation of RASSF1A led to the stability of β-catenin (94), as is the case with NORE1A (83).…”

“…Notably, most RASSF family members are down-regulated in human cancers, in part by epigenetic mechanisms (32). The best characterized member, RASSF1A, is now thought to be the most frequently silenced tumor suppressor in human cancers, highlighting the significance of this family in tumor suppression (31,33,34). …”