David M. Berman,^125* Sunil S. Karhadkar,^125* Andrew R. Hallahan,⁶⁷ Joel I. Pritchard,⁷ Charles G. Eberhart,² D. Neil Watkins,⁴ James K. Chen,¹⁵ Michael K. Cooper,¹³⁵ Jussi Taipale,¹⁵ James M. Olson,⁶⁷ Philip A. Beachy¹⁵

Constitutive Hedgehog (Hh) pathway activity is associated with initiation of neoplasia, but its role in the continued growth of established tumors is unclear. Here, we investigate the therapeutic efficacy of the Hh pathway antagonist cyclopamine in preclinical models of medulloblastoma, the most common malignant brain tumor in children. Cyclopamine treatment of murine medulloblastoma cells blocked proliferation in vitro and induced changes in gene expression consistent with initiation of neuronal differentiation and loss of neuronal stem cell-like character. This compound also caused regression of murine tumor allografts in vivo and induced rapid death of cells from freshly resected human medulloblastomas, but not from other brain tumors, thus establishing a specific role for Hh pathway activity in medulloblastoma growth.

Departments of ¹ Molecular Biology and Genetics, ² Pathology, ³ Neurology, ⁴ Oncology, and ⁵ Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. ⁶ Clinical Research Division, Fred Hutchinson Cancer Research Center, and ⁷ Division of Pediatric Oncology, University of Washington/Children’s Hospital, Seattle WA 98105, USA.
^*   These authors contributed equally to this work.