Regulation Of STAT3 Translocation And Cytochrome C Activity By OCT4

Background and objectiveOctamer-binding transcription factor-4(OCT4)is one of the key transcription factors in POU family in nucleus,mainly expressed in embryonic stem cells and germline stem cells,which plays a significant role in maintaining multipotency and self-upgrading of embryonic stem cells.The latest research shows that OCT4 is also highly expressed in embryonal carcinoma,seminoma and certain malignancies outside the reproductive system.Recent studies have demonstrated that OCT is highly expressed in embryonic carcinoma,seminoma,and some other malignancies beyond the reproductive system,suggesting a role of OCT4 in maintaining differentiation potential of cancer stem cells-when OCT4 is maintained at high concentration,cells maintain sternness;and when OCT4 is downregulated,cells differentiate into various terminal cells with specific functions and lost their sternness.Signal transducer and activator of transcription(STAT)-3,an important member of the STAT family,is closely related to cell proliferation,differentiation and apoptosis,and sustained activation of STAT3 signaling pathways can lead to cell proliferation and malignant transformation.However,the mechanisms how OCT4 and STAT3 affects stem cell differentiation and cancer cell EMT have not been fully clarified.In this study,we investigated the mechanism how OCT4 affect stem cell differentiation and cancer cell EMT from the perspective of energy metabolism.MethodPlasmids for STAT3,OCT4,as well as truncatingand point mutations of OCT4 were constructed by PCR and transformation.The vectors were transfected into human umbilical epithelium 293T cells,and human cervical cancer HeLa cells to investigate interactions between OCT4 and STAT3 and to determine the key sites for their interaction.Then,changes in translocation of STAT3 into mitochondrion,cytochrome C activity,and ATP productionafter OCT4 overexpression were measured by mitochondrial isolation and immunocytofluorescence,and immunoblotting.ConclusionAfter OCT4 overexpression,translocation of STAT3 into mitochondrion significantly decreased in the 293T cells,and ATP production significantly decreased.After transfecting full-length,truncated,or point-mutated OCT4 into the 293T and Hela cells,immunocytofluorescence and immunoblotting suggested that the 144th amino acid of OCT4 plays a key role in interaction between OCT4 and STAT3,and cells transfected with OCT4 showed decreased cytochrome C activity and ATP production.It was speculated that OCT4 regulates cytochrome C activity via STAT3 during both transformation of normal cells into IPS cells and transformation of normal cancer cells into cancer stem cells via EMT,thus lowering activity of cell's respiratory chain and modulating cell sternness and differentiation.