PTCH1 and neoplasm: To verify that tamoxifen had sufficiently induced Ptc deletion in the NSC74859‐treated group, such that MB should have formed, we performed RT‐PCR of the cerebellar tissue to detect loss of Ptc relative to that of tumor tissue derived from control treated mice and normal cerebellum from control Math1‐Cre‐ER‐Ptcflox/flox mice not administered tamoxifen (noninduced).