Altered expression of apoptotic genes in response to OCT4B1 suppression in human tumor cell lines.

OCT4B1 is a newly discovered spliced variant of OCT4 which is primarily expressed in pluripotent and tumor cells. Based on our previous studies, OCT4B1 is significantly overexpressed in tumors, where it endows an anti-apoptotic property to tumor cells. However, the mechanism by which OCT4B1 regulates the apoptotic pathway is not yet elucidated. Here, we investigated the effects of OCT4B1 suppression on the expression alteration of 84 genes involved in apoptotic pathway. The AGS (gastric adenocarcinoma), 5637 (bladder tumor), and U-87MG (brain tumor) cell lines were transfected with OCT4B1 or irrelevant siRNAs. The expression level of apoptotic genes was then quantified using a human apoptosis panel-PCR kit. Our data revealed an almost similar pattern of alteration in the expression profile of apoptotic genes in all three studied cell lines, following OCT4B1 suppression. In general, the expression of more than 54 apoptotic genes (64 % of arrayed genes) showed significant changes. Among these, some up-regulated (CIDEA, CIDEB, TNFRSF1A, TNFRSF21, TNFRSF11B, TNFRSF10B, and CASP7) and down-regulated (BCL2, BCL2L11, TP73, TP53, BAD, TRAF3, TRAF2, BRAF, BNIP3L, BFAR, and BAX) genes had on average more than tenfold gene expression alteration in all three examined cell lines. With some minor exceptions, suppression of OCT4B1 caused upregulation of pro-apoptotic and down-regulation of anti-apoptotic genes in transfected tumor cells. Uncovering OCT4B1 down-stream targets could further elucidate its part in tumorigenesis, and could lead to finding a new approach to combat cancer, based on targeting OCT4B1.