This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kubo, T. Articles by Yoshikawa, H. Search for Related Content PubMed PubMed Citation Articles by Kubo, T. Articles by Yoshikawa, H.

Apoptotic Speck Protein-Like, a Highly Homologous Protein to Apoptotic Speck Protein in the Pyrin Domain, Is Silenced by DNA Methylation and Induces Apoptosis in Human Hepatocellular Carcinoma

Departments of ¹ Epigenetic Carcinogenesis and ² Surgery, The Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan; and ³ DNA Chip Research, Inc., Kanagawa, Japan

We have identified a novel gene encoding a pyrin domain protein of 89 amino acids that is expressed in various tissues including liver, brain, and spleen. The protein is highly homologous to the pyrin domain of apoptosis-associated speck-like protein (ASC). Therefore, we termed it ASC-like (ASCL). We found that ASCL gene was densely and frequently (80%) methylated in hepatocellular carcinoma (HCC) cell lines. In contrast, normal liver samples did not show any significant methylation. This aberrant methylation correlated well with the suppression of RNA expression. Furthermore, a demethylating agent, 5-aza-2'-deoxycytidine, reactivated the ASCL expression in the methylation-silenced cells, indicating that ASCL is silenced by the associated DNA methylation. ASCL methylation was also found in primary HCC (4 of 17 samples), although the frequency was less than that in cell lines. In addition, we found that ASC was also methylated in primary samples (6 of the 17). Interestingly, either ASCL or ASC methylation was observed in 53% (9 of the 17) of primary HCC samples. Significantly, the restoration of ASCL in the methylation-silenced cells demonstrated growth suppression in colony formation assay. This growth suppression effect of ASCL was supported by apoptotic changes observed in ASCL-transfected cells in which annexin-V binding was positive and caspase-3 was activated. Based on the methylation-silencing and the growth suppression activity, we propose that ASCL plays a significant role in the development of HCC.