Main content area

Smoothened Mutation Confers Resistance to a Hedgehog Pathway Inhibitor in Medulloblastoma

Yauch, Robert L., Dijkgraaf, Gerrit J.P., Alicke, Bruno, Januario, Thomas, Ahn, Christina P., Holcomb, Thomas, Pujara, Kanan, Stinson, Jeremy, Callahan, Christopher A., Tang, Tracy, Bazan, J. Fernando, Kan, Zhengyan, Seshagiri, Somasekar, Hann, Christine L., Gould, Stephen E., Low, Jennifer A., Rudin, Charles M., de Sauvage, Frederic J.
Science 2009 v.326 no.5952 pp. 572-574
G-protein coupled receptors, amino acid substitution, animal models, aspartic acid, brain, clinical trials, disease course, drug resistance, drugs, genes, humans, neoplasms, patients, serpentine, signal transduction
The Hedgehog (Hh) signaling pathway is inappropriately activated in certain human cancers, including medulloblastoma, an aggressive brain tumor. GDC-0449, a drug that inhibits Hh signaling by targeting the serpentine receptor Smoothened (SMO), has produced promising anti-tumor responses in early clinical studies of cancers driven by mutations in this pathway. To evaluate the mechanism of resistance in a medulloblastoma patient who had relapsed after an initial response to GDC-0449, we determined the mutational status of Hh signaling genes in the tumor after disease progression. We identified an amino acid substitution at a conserved aspartic acid residue of SMO that had no effect on Hh signaling but disrupted the ability of GDC-0449 to bind SMO and suppress this pathway. A mutation altering the same amino acid also arose in a GDC-0449-resistant mouse model of medulloblastoma. These findings show that acquired mutations in a serpentine receptor with features of a G protein-coupled receptor can serve as a mechanism of drug resistance in human cancer.