Figure 7 RASSF1A promotes apoptosis that is enhanced by K-RasG12V. (a) CNE-2 cells were transiently transfected with empty vector and RASSF1A-expression vectors in the presence or absence of activated K-Ras, 48 h post transfection, empty vector cells showed 4.1% of apoptosis rate, RASSF1A expression #QNZ solubility dmso randurls[1|1|,|CHEM1|]# cells was 22.7%, and RASSF1A + activated K-Ras expression CNE-2 cells showed 36.0% of apoptosis rate. (b) The statistical analysis of the apoptotic cells in each group. *: vs Vector group, p < 0.001; (Black triangle): vs RASSF1A group, p < 0.001. Discussion Recent studies concerned with epigenetic

research are mostly focus on the RASSF1 family, which has three major transcripts, A, B and C. The transcript A and C were expressed in all normal tissues, but RASSF1A expression was impaired in a number of lung tumor cell lines and in several other cancer

Compound C molecular weight cell lines [10, 11]. Loss of expression was correlated with methylation of the CpG-island promoter sequence of RASSF1A. Reintroduction of RASSF1A in SCLC lines reduces colony formation, suppressed anchorage-independent growth and inhibited tumor formation in nude mice[18]. Moreover, it was reported that Rassf1a-knockout mice are apt to suffer from various cancers[23]. These characteristics lead to a proposal that the RASSF1A isoform is the major tumor suppressor gene inactivated PRKACG in many kinds of tumors by promoter methylation, which is the major mechanism for inactivation of RASSF1A since an observation of point mutation in RASSF1A gene was found to be a rare event in a majority of human cancers[24]. Chow et al. and Steinmann et al. demonstrated that RASSF1A is a critical tumor suppressor gene harboring with high frequency of promoter

methylation, which is located on 3p21.3 in NPC[13, 25]. In our study, we detected that RASSF1A mRNA expression was down-regulated in NPC cell lines and primary tumors. Methylation specific PCR and RT-PCR analysis also revealed a correlation between RASSF1A expression level and methylation status in NPC cell lines, primary tumors and normal epithelial. 5-aza-2′-deoxycytidine treatment further confirmed that promoter hypermethylation contributes to the lack of expression of RASSF1A in the NPC cell lines. Base on these findings, hypermethylated DNA could be served as a potential molecular tumor marker that distinguishes cancers from normal tissues. Our MSP analysis showed that RASSF1A methylation was frequent in NPC, as the RASSF1A promoter region was subjected to methylation in 71.05% of the primary tumors, the two NPC cell lines that we examined were also both partial methylation. In addition, our findings of a lack of RASSF1A methylation in the normal nasopharyngeal epithelia support the fact that epigenetic silencing of RASSF1A is a tumor specific process.