OCT4 pseudogenes present in human leukemia cells.

The transcription factor OCT4 is expressed in embryonic stem cells (ESCs) and has been considered as a main regulator in maintaining pluripotency of ESCs. Several studies have showed OCT4 expression in human solid tumor and adult stem or progenitor cells. However, whether OCT4 is expressed in normal hematopoietic system including the peripheral blood and bone marrow remains controversial. Furthermore, the functional expression of OCT4 in leukemia cells and its potential significance in leukemia studies have been poorly defined. The aim of this study was to examine and analyze the genuine expression of OCT4 in human leukemia cells by means of RT-PCR, flow cytometry, PCR product sequencing and alignment with NCBI BLAST and DNAMAN software. The full lengths of the putative OCT4 genes were amplified in 2/9 leukemia cell lines and 7/49 leukemia patients' samples. However, many base mutations in putative OCT4 positive samples were found. Sequence alignment analysis showed a higher similarity between the putative OCT4 PCR products and the pseudogenes in chromosomes 1 and 8. The positive rates of OCT4 protein detected with flow cytometry were low, and almost all of them were less than 10% of positivity. A very small fraction of leukemia stem cells with OCT4 protein expression was found. We conclude that OCT4 pseudogenes in chromosomes 1 and 8 present in the panel of leukemia cells tested and the OCT4 protein is rarely detected with flow cytometry in leukemia cells.