The gene POU5F1 (also known as an OCT4) belonging to POU protein family is composed of 5 exons that can create many isoforms by alternative splicing. Most known isoform is OCT4A that is expressed in many types of stem cells. Its nuclear localization and presence of the DNA-binding domain enable it to regulate the expression of genes that are responsible for pluripotency and blocking of the differentiation of the cells. Other splicing products are numerous OCT4B isoforms (OCT4B-OCT4B5) that differ from OCT4A in the cell localization and in absence of the DNA-binding domain. Majority of OCT4 isoforms were discovered only recently and there have not been clear evidences about their role in the cells yet. The role of OCT4A, OCT4B and OCT4B1 in tumorigenesis have already been explored but without definite results. The aim of our research is the analysis of alternative splicing variants of the gene POU5F1 in association with the patient´s prognosis and their occurrence in the metastasis.
For this analysis we used fresh surgical specimens of the patients with colorectal cancer that were isolated from primary tumours (n=47) and from the metastasis (n=31). Subsequently, the total RNA was isolated and transcribed to cDNA. Through the quantitative PCR method using particular TaqMan assays for specific variants and with ΔΔ Ct method, we separately analyzed the relative gene expression of isoform A, isoforms B, but also all isoforms together.
We found out that in tumour specimens isolated from primary tumours was the expression of all POU5F1 isoforms significantly lower than in adjacent non-tumour tissue. On the other hand, the significantly increased expression in metastatic tumor compared to primary tumours was observed only in experiment with probe specific for all POU5F1 isoforms whereas isoform A, neither isoform B were not reason of increased expression of POU5F1 in metastasis.
Our analysis indicate that alternative splicing play a pivotal role in metastatic colorectal cancer and whereas we exclude isoform A and isoforms B as a cause of increased expression of POU5F1 in metastasis, we consider as an important to identify responsible alternative transcript.
The authors.
VEGA 1/0269/22.
All authors have declared no conflicts of interest.