Clinical significance of ERas oncogene on cancer

Abstract

15083 Background: Embryonic stem (ES) cells are pluripotent cells derived from early mammalian embryos. When ES cells are subcutaneously injected into immunodeficient or isogenic mice, a teratoma is formed within a few weeks. This tumor is composed of all three germ layers in a disorganized fashion. Thus there could be some common molecular mechanisms shared by ES cells and somatic cancer cells. The ERas oncogene is a recently identified gene that supports the tumorigenic growth of ES cells by producing a constitutively active Ras protein. There have been no report about expression of ERas oncogene on cancer cells until now. The aim of this study is to investigate expression and clinical significance of ERas oncogene on cancer cell lines and clinical cancer tissues. Methods: A panel of 35 human cancer cell lines, 5 normal cell lines, and 20 patiants with gastric cancer tissues were used in this study. ERas mRNA expression was examined by reverse transcription-polymerase chain reaction. The effect of the DNA methyl transferase inhibitor, 5-aza-2’- deoxycitydine on the ERas expression was analyzed. Methylation of CpG islands of ERas promoter lesion was investigated using bisulfate-directsequence analysis. Results: Expression of ERas mRNA was not found in any normal cells. In contrast, ERas mRNA was found in 15 of 35 cancer cell lines, including 8 of 15 gastric cancers, 4 of 7 colorectal cancers, 2 of 6 pancreas cancers, 1 of 3 breast cancers and none of esophageal cancers. Eras mRNA was found in all gastric cancer tissues, but not normal tissues. 5-aza-2’-deoxycytidine treatment at 2, 5, and 10μM for 24 h resulted in ERas expression in 10 of 20 cancer cell lines with respect to the silencing of ERas, including 7 of 7 gastric cancers, 1 of 3 colorectal cancers and 2 of 3 breast cancers. Methylation of CpG island were found in the cancer cell lines without ERas expression, but not in these with ERas expression. Conclusions: ERas oncogene is associated with the carcinogenesis pathway in human cancer. Eras might be useful marker for cancer diagnosis. No significant financial relationships to disclose.