Supplemental Figures S1-S6. Comparison of HN11 and TU167 by RNA-Seq Expression (S1); Suppression of Radiation-induced GLI1 using shRNA Model (S2); Cyst Formation Following Radiation Treatment in Orthotopic TU167-implanted Tumors (S3); Radiation-induced Gli1 Expression and the Effect of Rapamycin Inhibition in HN11 Cells (S4); Effect of siRNA inhibition on Head Neck Cancer Cells and Gli1 Nuclear Translocation (S5); Schema and Histology Detailing Radiation-induced Tumor Repopulation (S6).
ARTICLE ABSTRACTLocal control and overall survival in patients with advanced head and neck squamous cell cancer (HNSCC) remains dismal. Signaling through the Hedgehog (Hh) pathway is associated with epithelial-to-mesenchymal transition, and activation of the Hh effector transcription factor Gli1 is a poor prognostic factor in this disease setting. Here, we report that increased GLI1 expression in the leading edge of HNSCC tumors is further increased by irradiation, where it contributes to therapeutic inhibition. Hh pathway blockade with cyclopamine suppressed GLI1 activation and enhanced tumor sensitivity to radiotherapy. Furthermore, radiotherapy-induced GLI1 expression was mediated in part by the mTOR/S6K1 pathway. Stroma exposed to radiotherapy promoted rapid tumor repopulation, and this effect was suppressed by Hh inhibition. Our results demonstrate that Gli1 that is upregulated at the tumor–stroma intersection in HNSCC is elevated by radiotherapy, where it contributes to stromal-mediated resistance, and that Hh inhibitors offer a rational strategy to reverse this process to sensitize HNSCC to radiotherapy. Cancer Res; 74(23); 7024–36. ©2014 AACR.