Zic2 synergistically enhances Hedgehog signaling pathway in cervical cancer

Abstract

The Hedgehog (Hh) signaling pathway plays an important role in human development. Aberrant activation of this pathway has been documented in many human cancers. However, activation of Hh signaling pathway is rarely reported in cervical tumors. In this study, we examined the activity of Hh pathway in cervical cancer cells by a specific inhibitor, cyclopamine. Of three cervical cancer cell lines (Hela, SiHa and C33A) treated by cyclopamine (30 μM), a decrease of cell viability (45% to 67%) was observed in all cell lines in a time-dependent manner. This suggests that the Hh pathway is activated in regulating the growth of cervical cancer cells. By cDNA microarray analysis, we found that one of Hh related gene, Zic2, was significantly higher in cervical cancer cell lines. Further investigation by semi-quantitative RT-PCR demonstrated that Zic2, was remarkably upregulated in cervical cancer cell lines as compared with normal immortalized cervical cell lines, and was consistent with the expression of Gli1, a key Hh pathway effector. To investigate the role of Zic2 in Hh pathway, transient expression of Zic2 and Gli1 into HEK293 cells increased Gli-promoter luciferase activity dose dependently. Moreover, by clonogenic assay, enforced expression of Zic2 increased colony number and size by 31% as compared with empty vector control in Hela and C33A cervical cancer cells. Our preliminary data suggest that Hh pathway is crucial in cervical cancer cells, and the overexpression of Zic2 may enhance the activity of this pathway in cervical cancer cells. Further investigations of the molecular mechanism and functions of Zic2 in this pathway and the tumorigenicity of cervical cancer are warranted.