Conclusive Evidence for OCT4 Transcription in Human Cancer Cell Lines: Possible Role of a Small OCT4-Positive Cancer Cell Population

Abstract

The role of octamer-binding transcription factor 4 (OCT4) in human cancer is still debated. Although many studies have been published on human OCT4, determining which of the findings are accurate or which are false-positives is currently challenging. We thus developed the most reliable method to date for highly specific and comprehensive detection of genuine OCT4-transcript variants without false-positive results. Our results provided clear evidence that the transcripts of OCT4A, OCT4B, OCT4B1, and other novel splicing variants are indeed present in many cancer cell lines, but are rarely detected in normal tissue-derived differentiated cells. Using the tagged genomic transgene, we then verified endogenous OCT4A translation in cancer cell subpopulations. Moreover, analysis of possible other protein isoforms by enforced expression of OCT4B variants showed that the B164 isoform, designated human OCT4C, is preferentially produced in a cap-dependent manner. We confirmed that the OCT4C isoform, similar to OCT4A, can transform non-tumorigenic fibroblasts in vitro. Finally, ablation of OCT4-positive cells using promoter-driven diphtheria toxin A in high malignant cancer cells caused a significant decrease in migration and Matrigel invasion. These findings strongly suggest a significant contribution of OCT4 to the phenotype of human cancer cells. Stem Cells 2018.

Systematic expression alteration analysis of master reprogramming factor OCT4 and its three pseudogenes in human cancer and their prognostic outcomes

“…Among its three transcript variants, OCT4A has been shown to maintain the pluripotency and self-renewal of iPSCs and ESCs 9 . OCT4A is not only expressed in normal stem cells, but is also undoubtedly expressed at various levels in a variety of human cancer cell lines 46 . Zhou et al .…”

“…However, available qPCR or RT-PCR primers are generally not able to distinguish between OCT4 isoforms; thus, our bioinformatics analyses with the current literature and databases may have limitations and certain flaws. With the recent development of true OCT4 isoform-specific primers 46 , 47 , it will now be possible to overcome this limitation in future studies.…”

Prognostic value of OCT4A and SPP1C transcript variant co-expression in early-stage lung adenocarcinoma

“…Reverse transcriptase negative controls were used to assess genomic DNA contamination. The primers used for PCR are described in Table S3 [16]. We used two PCR enzymes [EmeraldAmp PCR Master Mix, RR300A; Takara) or PrimeSTAR HS DNA polymerase (R010A; Takara)] in a total volume of 20 μL.…”

“…Although these studies suggest that OCT4 plays an role in human somatic cancers, its somatic function is controversial. Since its proposed role is based on the results derived from multiple transcript variants and related, active pseudogenes, this may have introduced false positives and led to an erroneous or questionable interpretation of the data [14][15][16]. In addition, previous studies also indicated that OCT4A does not play a functional role in adult somatic murine tissues [17,18], therefore, many researchers have been reticent to accept a role for OCT4A in human adult somatic tissues or related cancers [14,[18][19][20][21][22].…”

“…In our previous study, we developed a highly specific reverse transcription polymerase chain reaction (RT-PCR) assay to analyse the human OCT4 gene, which eliminated false positives and identified multiple transcripts in human carcinoma cell lines [16]. Additionally, we reported that OCT4 was translated in a subpopulation of human endometrial cancer cells characterised by enhanced cell migration and invasion [16]. Consistent with our findings, another group reported that endogenous OCT4A functions as a transcription factor in somatic cancer cells [23].…”