Hedgehog-Gli Signaling Pathway Glioma Cell Proliferation, Apoptosis And Invasion Capacity

Objectives Recent studies have shown aberrant activation of Hedgehog(HH)-Gli signaling pathway exists in a fraction of human gliomas. Blocking the pathway leads to the decrease of tumor cell proliferation and tumorigenicity. However, little is known about the HH-Gli pathway's impact on glioma cell behavior regarding cell cycle, apoptosis and invasiveness. The relationship between the HH-Gli pathway and the clinicopathological features also remains to be elucidated.Methods 110 primary glioma samples were obtained from those patients who underwent surgical rection in our department from 2007 to 2009. Immunohistochemical staining was performed to analyze the relationship between Glil nuclear staining and pathological grades, and the relationship between Glil nuclear staining and the tumor proliferative index. In in vitro experiments, immunofluorescence staining and real-time PCR were used to detect the HH-Gli 1 activity in glioma cell lines U87, SHG-44, U251 and A172. Then cyclopamine and small RNA interference technique were used to inhibit the pathway activity in these glioma cell lines, and their phenotype changes were recorded. Furthermore, we measured the relative gene expressions by real-time PCR to clarify the molecular mechanisms behind the phenotype changes.Results Aberrant activation of the HH-Gli 1 pathway existed in all four grades of human glioma samples. The nuclear staining of Glil protein was associated with the pathological grades and proliferative index. The four glioma cell lines cultured in vitro harbored different activity of the HH-Gli1 pathway. As for glioma cells with an active pathway like U87, SHG-44 and U251, cyclopamine and siGlil significantly reduced the glioma cell growth and invasion. Cell cycle Go/Gi arrest and enhanced apoptosis were detected after blocking the HH-Gli1 pathway. Further analysis showed that a set of genes related to those phenotype changes saw a remarkable change in their mRNA levels. For A172 cells which have a silent HH-Gli1 pathway, neither cyclopamine nor siGlil produced marked cell behavior changes.Conclusions HH-Gli 1 pathway can serve as a new therapeutic target for human gliomas. Inhibition of the pathway takes its effect through multiple mechanisms.