Inactivation of RASSF2A by promoter methylation correlates with lymph node metastasis in nasopharyngeal carcinoma

Abstract

RASSF2 can bind directly to K-Ras and function as a negative effector of Ras protein. RASSF2A is the only isoform of RASSF2 that contains CpG islands in its promoter and it has been reported to be inactivated by its promoter methylation in several human cancers. In the present study, we investigated the correlation of RASSF2A expression with its promoter methylation in nasopharyngeal carcinoma (NPC). Expression of RASSF2A was downregulated in 80% (4/5) of NPC cell lines. Decreased RASSF2A expression was also observed in NPC primary tumors compared with normal nasopharyngeal epithelia. Promoter methylation of RASSF2A could be detected in all the RASSF2A-silenced cell lines (4/5) of the NPC cell lines and 50.9% (27/53) of primary tumors, but not in any of the normal epithelia. RASSF2A-methylated cases showed a significantly lower level of RASSF2A expression than unmethylated cases. Loss of RASSF2A expression can be greatly restored by the methyltransferase inhibitor 5-aza-dC in NPC cell lines. In addition, patients with methylated RASSF2A presented a higher frequency of lymph node metastasis (p < 0.05). Ectopic expression of RASSF2A in RASSF2A-silenced and -methylated NPC cell line CNE2 shows that RASSF2A could inhibit cell cycle progression, colony formation and cell migration, which provided further evidence that RASSF2A is a candidate tumor suppressor gene. In conclusion, RASSF2A, a candidate tumor suppressor gene (TSG), is frequently inactivated by its promoter methylation and this aberrant methylation correlates with lymph node metastasis in NPC. ' 2006 Wiley-Liss, Inc.

Evaluation of the 3p21.3 tumour-suppressor gene cluster

“…The feasibility of using RASSF2A methylation as a biomarker for CRCs, perhaps in combination with other genes, is an area of current research in our laboratory. RASSF2A methylation has also been found in gastric cancer at frequencies ranging from 29 to 79% and in 51% of NPC primary tumours (Endoh et al, 2005;Zhang et al, 2007). In NPC tumours RASSF2A methylation correlates with increased metastatic potential (Zhang et al, 2007).…”

“…RASSF2A methylation has also been found in gastric cancer at frequencies ranging from 29 to 79% and in 51% of NPC primary tumours (Endoh et al, 2005;Zhang et al, 2007). In NPC tumours RASSF2A methylation correlates with increased metastatic potential (Zhang et al, 2007). While RASSF4/AD037 is expressed in a variety of normal tissues, it is lost or downregulated in a variety of tumour-cell lines and primary tumours.…”

“…It is also important to note that in some cell backgrounds (prostate and renal cancer cell lines LNCaP and KRC/Y, respectively) RASSF1C re-expression potently suppressed tumour growth in vitro and in vivo in SCID mice suggesting it too could act as a TSG (Li et al, 2004b). Re-expression of RASSF2A, AD037A and NORE1A also results in suppression of tumour growth in a variety of different tumour types Chen et al, 2003;Vos et al, 2003a, b;Aoyama et al, 2004;Eckfeld et al, 2004;Akino et al, 2005;Zhang et al, 2007). For several RASSF members growth suppression is enhanced by co-transfection of constitutively active Ras proteins (Vos et al, 2000(Vos et al, , 2003a or by artificially forcing membrane localization thereby facilitating interaction with Ras (Eckfeld et al, 2004).…”

An Update on Epstein-Barr Virus and Nasopharyngeal Carcinogenesis

“…4) ( Table 3). Inactivation of the RASSF1A and p16 tumor suppressor genes on 3p21 and 9p21 by homozygous deletions and promoter methylation are the most common alterations described in NPC [30][31][32]. 3p and 9p abnormalities have been identified in low-grade dysplastic lesions and normal nasopharyngeal mucosa of individuals at high risk indicating that these genetic changes are early events in the pathogenesis of NPC [10,17,20,33].…”

The methylation status of RASSF1A promoter predicts responsiveness to chemotherapy and eventual cure in hepatoblastoma patients

“…[10][11][12] Thus, we thought that epigenetic silencing of tumor suppressor genes might be involved in the tumorigenesis of hepatoblastoma and examined the methylation status of 13 candidate tumor suppressor genes, whose aberrant methylation has previously been shown in various cancers. [13][14][15][16][17][18][19][20][21][22] Conventional methylation-specific PCR (MSP) analysis showed hypermethylation in only 3 of the 13 genes, RASSF1A, SOCS1 (suppressor of cytokine signaling 1) and CASP8 (caspase-8) genes, but not in the remaining 10 genes. We examined the correlation of the methylation status of the 3 genes with various clinical characteristics in a substantial number of hepatoblastoma tumors.…”