STAT3 correlates with stem cell-related transcription factors in cervical cancer

Cancer stem cells (CSCs) are considered responsible for the high recurrence rate in cervical carcinoma. It has been demonstrated that the signal transducer and activator of transcription 3 (STAT3) is involved in the oncogenesis and takes part in mediating the effects of maintaining stem cell phenotype and pluripotency by regulating the expression of stem cell-related transcription factors. However, the correlation between STAT3 and stem cell-related transcription factors in cervical cancer has not been elucidated. In this study, we established overexpressing plasmid (GV316-STAT3) and siRNA-STAT3 for transfecting Siha cells. Cells negative or positive for Nanog, Oct4, or Sox2 were selected by flow cytometry. Proliferation and differentiation rate of Siha cells was determined by detecting the efficiency of tumor sphere formation. The expression of Nanog, Oct4 and Sox2 (cancer stem cell markers) and STAT3 was detected by quantitative real-time PCR and immunoblotting for Siha cells and by immunohistochemistry (IHC) for cervical tissues, respectively. The results showed that Nanog+, Oct4+, and Sox2+ Siha-STAT3 over-expressing cells displayed the typical non-adherent spheres. The sphere formation efficiency was significantly different between Siha-STAT3 overexpressing cells and siRNA-STAT3 cells (P<0.05). Meanwhile, the expression levels of Oct4, Nanog and Sox2 mRNA and protein were significantly higher in Siha-STAT3 overexprssing cells than in siRNA-STAT3 cells (P<0.05). In addition, the positive rate of STAT3, Nanog, Oct4 and Sox2 in cervical cancer tissues was higher than that in chronic cervicitis group (P<0.05). There was a significantly positive relationship between STAT3 and Nanog or Oct4 or Sox2 expression (all P<0.001). These results suggested that Oct4+, Sox2+, and Nanog+ cell population possesses stem cell properties in cervical cancer, which may contribute to cervical carcinogenesis and be regulated by STAT3.