Frequent epigenetic inactivation of RASSF2 in thyroid cancer and functional consequences

Abstract

BackgroundThe Ras association domain family (RASSF) encodes for distinct tumor suppressors and several members are frequently silenced in human cancer. In our study, we analyzed the role of RASSF2, RASSF3, RASSF4, RASSF5A, RASSF5C and RASSF6 and the effectors MST1, MST2 and WW45 in thyroid carcinogenesis.ResultsFrequent methylation of the RASSF2 and RASSF5A CpG island promoters in thyroid tumors was observed. RASSF2 was methylated in 88% of thyroid cancer cell lines and in 63% of primary thyroid carcinomas. RASSF2 methylation was significantly increased in primary thyroid carcinoma compared to normal thyroid, goiter and follicular adenoma (0%, 17% and 0%, respectively; p < 0.05). Patients which were older than 60 years were significantly hypermethylated for RASSF2 in their primary thyroid tumors compared to those younger than 40 years (90% vs. 38%; p < 0.05). RASSF2 promoter hypermethylation correlated with its reduced expression and treatment with a DNA methylation inhibitor reactivated RASSF2 transcription. Over-expression of RASSF2 reduced colony formation of thyroid cancer cells. Functionally our data show that RASSF2 interacts with the proapoptotic kinases MST1 and MST2 and induces apoptosis in thyroid cancer cell lines. Deletion of the MST interaction domain of RASSF2 reduced apoptosis significantly (p < 0.05).ConclusionThese results suggest that RASSF2 encodes a novel epigenetically inactivated candidate tumor suppressor gene in thyroid carcinogenesis.

Ectopic expression of RASSF2 and its prognostic role for gastric adenocarcinoma patients

“…They also observed that gastric cancers with methylation at U1 and D1 exhibited significantly less frequent lymphatic permeation than unmethylated gastric cancers. Afterwards, epigenetic inactivation of RASSF2 was found in oral squamous cell carcinoma (16), head and neck squamous cell carcinoma (26), hepatocellular (27) and thyroid cancers (28). Although a previous study demonstrated that expression of the RASSF2 gene is silenced by methylation in human gastric cancer (29), the authors did not clarify the clinical impact of RASSF2 expression or the prognostic value for patients with gastric cancer since the number of cases was too small.…”

RASSF2methylation is a strong prognostic marker in younger age patients with Ewing sarcoma

“…RASSF2 has previously been shown to be methylated in various cancers including breast, colorectal, gastric, lung, oral and thyroid cancer. [8][9][10][11][12] Expression of RASSF2 was found to be an independent prognostic factor in gastric cancer patients 10 and RASSF2 methylation could be detected in fecal DNA from patients with gastrointestinal tumors. 13 In functional terms RASSF2 is a novel pro-apoptotic effector of K-Ras and acts as a tumor suppressor gene.…”

“…Expression primers used in RT-PCR were previously described by reference 19. The real time RT-PCR primers for RASSF2 were described in Schagdarsurengin U et al 11 and human β actin primers were described in. 21 Power SYBR Green mix (Applied Biosystems) was used and the plates were read using BIO-RAD IQ5 machine.…”

RASSF tumor suppressor gene family: Biological functions and regulation

“…Inhibits cell growth, arrests cell cycle [58,62] Involved in actin cytoskeleton organization [148] Induces apoptosis [58,62,145] Suppresses transcriptional activity of NFjB [181] Inhibits MST2 activity [93] K-Ras [62] PAR4 [64] MST1 [66,177] MST2 [177] Yes [67] growth retardation, systematic haematopoietic anomalies, defects in osteoclast and osteoblast differentiation 3 12q14. 1 …”