OCT4B modulates OCT4A expression as ceRNA in tumor cells.

OCT4 is an essential transcription factor for maintaining the self-renewal and the pluripotency of embryonic stem cells (ESCs). The human OCT4 gene can generate three mRNA isoforms (OCT4A, OCT4B and OCT4B1) by alternative splicing. OCT4A protein is a transcription factor for the stemness of ESCs, while the function of OCT4B isoforms remains unclear. Most types of cancer express a relatively low level of OCT4 protein, particularly the OCT4B isoforms. In the present study, we found that OCT4A and OCT4B mRNA were co-expressed in several types of tumor cell lines and tumor samples, and we demonstrated that OCT4B functioned as a non-coding RNA, modulating OCT4A expression in an miRNA-dependent manner [competing endogenous RNA (ceRNA) regulation] at the post-transcription level in the tumor cell lines. This is the first time that ceRNA regulation was observed among spliced isoforms of one gene, and may pave the way for identification of new targets for cancer treatment.