Sophia Subat1,2,3, Kaoru Mogushi1,4, Mahmut Yasen1,3,5, Takashi Kohda2, Yuichi Ishikawa6, Hiroshi Tanaka1. 1. Department of Systems Biology, Graduate School of Biomedical Science, Tokyo Medical and Dental University, Tokyo, Japan. 2. Department of Epigenetics, Graduate School of Biomedical Science, Tokyo Medical and Dental University, Tokyo, Japan. 3. Division of Pathology, The Cancer Institute, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ward, Tokyo, 135-8550, Japan. 4. Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan. 5. Department of Surgery, Xinjiang Medical University Affiliated Tumor Hospital, Urumqi, Xinjiang Uyghur Autonomous Region, China. 6. Division of Pathology, The Cancer Institute, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ward, Tokyo, 135-8550, Japan. ishikawa@jfcr.or.jp.
Abstract
PURPOSE: Recent genetic studies have suggested that tumor suppressor genes are often silenced during carcinogenesis via epigenetic modification caused by methylation of promoter CpG islands. Here, we characterized genes inactivated by DNA methylation in human hepatocellular carcinoma (HCC) to identify the genes and pathways involved in DNA methylation in hepatocellular carcinoma. METHODS: Eight HCC-derived cell lines were treated with a DNA demethylating agent, 5-aza-2'-deoxycytidine. Additionally, 100 pairs of primary HCC and adjacent non-cancerous tissues as well as 15 normal liver tissues were analyzed by comprehensive gene expression analysis using microarrays. Moreover, gene set enrichment analysis identified the major molecular pathways associated with DNA methylation. Validation of gene expression and DNA methylation status was performed by real-time PCR after bisulfite modification. RESULTS: We showed that CXCL2, an immune-related chemokine, expression was significantly downregulated in tumor tissues and also significantly upregulated by DAC treatment in cell lines. Furthermore, we observed a statistically significant difference in methylation status between normal liver tissues and tumor tissues (P < 0.05). In addition, tumors with higher CXCL2 expression included significantly more numbers of multiple tumors than the lower expression group. CONCLUSIONS: We identified CXCL2, an immune-related chemokine, decreased in hepatocellular carcinoma and the regulation mechanism may be controlled by methylation. Further studies should be warranted to examine if and to what extent the gene is actually suppressed by methylation and if there is a possibility that the CXCL2 axis plays a role for diagnosis and treatment of hepatocellular carcinoma.
PURPOSE: Recent genetic studies have suggested that tumor suppressor genes are often silenced during carcinogenesis via epigenetic modification caused by methylation of promoter CpG islands. Here, we characterized genes inactivated by DNA methylation in humanhepatocellular carcinoma (HCC) to identify the genes and pathways involved in DNA methylation in hepatocellular carcinoma. METHODS: Eight HCC-derived cell lines were treated with a DNA demethylating agent, 5-aza-2'-deoxycytidine. Additionally, 100 pairs of primary HCC and adjacent non-cancerous tissues as well as 15 normal liver tissues were analyzed by comprehensive gene expression analysis using microarrays. Moreover, gene set enrichment analysis identified the major molecular pathways associated with DNA methylation. Validation of gene expression and DNA methylation status was performed by real-time PCR after bisulfite modification. RESULTS: We showed that CXCL2, an immune-related chemokine, expression was significantly downregulated in tumor tissues and also significantly upregulated by DAC treatment in cell lines. Furthermore, we observed a statistically significant difference in methylation status between normal liver tissues and tumor tissues (P < 0.05). In addition, tumors with higher CXCL2 expression included significantly more numbers of multiple tumors than the lower expression group. CONCLUSIONS: We identified CXCL2, an immune-related chemokine, decreased in hepatocellular carcinoma and the regulation mechanism may be controlled by methylation. Further studies should be warranted to examine if and to what extent the gene is actually suppressed by methylation and if there is a possibility that the CXCL2 axis plays a role for diagnosis and treatment of hepatocellular carcinoma.
Entities:
Keywords:
CXCL2; DNA methylation; Hepatocellular carcinoma; Inflammation; Tumor suppressor genes