Inhibition of the Sonic Hedgehog Pathway by Cyclopamine or GLI1 siRNA Reduces In Vivo Tumorigenesis of Human Medulloblastoma Cells Xenotransplanted to Immunodeficient Nude Mice

Abstract

Medulloblastoma is an aggressive tumor; grade IV of the WHO classification that develops in the cerebellum, mostly linked to infancy and adolescence. It can be classified histologically and molecularly in different subtypes. Morphologically it can be divided into classical, desmoplastic/nodular, anaplastic, and large cell medulloblastoma. Molecularly, there are four groups: Wnt, Shh (sonic hedgehog), group 3 (mainly linked to MYC amplification), and group 4 (for unclassified tumors). Our work tries to prove the inhibition of the Shh pathway in two medulloblastoma cell lines: DAOY, a desmoplastic cerebellar medulloblastoma cell line of the Shh molecular group; and D283 Med, derived from a metastasis to peritoneum, possibly corresponding to an aggressive group 3 medulloblastoma. Cyclopamine, an inhibitor of the SMO oncogenic protein, and GLI1 siRNA were used as inhibitory agents of the Shh pathway in the two cell lines. For the in vivo assay, for each cell line, each experimental group consisted of 6 mice injected subcutaneously with control cells on the right flank, and cells treated with cyclopamine or GLI1 siRNA on the left flank. In the cell lines studied, cyclopamine showed a high inhibitory growth of subcutaneous tumors in the D283 Med and DAOY lines. The siRNA treatment, however, was only effective in the D283 Med cell line.