Pluripotency and self-renewal capacity of human embryonic stem cells (hESCs) are retained by hESCs related genes as OCT4, SOX2 and NANOG. These genes are shown high expression level in diverse cancer cells and have potential role in the carcinogenesis. On the contrary to this, several genes which are up-regulated in the differentiated hESCs are involved to suppress the carcinogenesis or proliferation of cells. We discovered several genes in immortalized lung fibroblast (WI-38 VA13) by suppression subtractive hybridization. Among them, we focused chromosome 6 open reading frame 62 (C6orf62) which is uncharacterized, mapped to 6p22.3 and generated to Hepatitis B virus X-transactivated proteins (HBVx-transactivated proteins, XTP). Aim of this study was to characterize C6orf62 through analyzing of expression pattern in various cell lines. Expression of C6orf62 was significantly up- regulated in diverse normal cell lines than cancer cell lines. And C6orf62 was up-regulated in differentiated hESCs (endothelial cells, neural cells) compared to those of undifferentiated hESCs. Also, C6orf62 in WI-38 cells was highly up-regulated during G1/S transition of the cell cycle. Taken together, C6orf62 is shown expression pattern similar to differentiated hESCs-associated genes which down-regulated in cancer cells. Therefore, we assume that C6orf62 may participate to suppress the proliferation and to induce differentiation through regulating the cell cycle.

The endogenous retrovirus-like elements (HERVs) found on several human chromosomes are somehow involved in gene regulation, especially during the transcription level. HERV-H, located on chromosome Xp22, may regulate gastrin-releasing peptide receptor (GRPR) in connection with diverse diseases. By suppression subtractive hybridization screen on SV40-immortalized lung fibroblast (WI-38 VA-13), we discovered that expression of HERV-HX2, a clustered HERV-H sequence on chromosome X, was upregulated in immortalized lung cells, compared to that of normal cells. Expression of HERV-HX2 was then analyzed in various cell lines, including normal somatic cells, cancer cells, SV40-immortalized cells, and undifferentiated and differentiated human embryonic stem cells. Expression of HERV-HX2 was specifically upregulated in continuously-dividing cells, such as cancer cells and SV40-immortalized cells. Especially, HERV-HX2 in HeLa cells was highly upregulated during the S phase of the cell cycle. Similar results were obtained in hES cells, in which undifferentiated cells expressed more HERV-HX2 mRNA than differentiated hES cells, including neural precursor and endothelial progenitor cells. Taken together, our results suggest that HERV-HX2 is upregulated in cancer cells and undifferentiated hES cells, whereas downregulated as differentiation progress. Therefore, we assume that HERV-HX2 may playa role on proliferation of cancer cells as well as differentiation of hES cells in the transcriptional level.