Blood samples are collected periodically for pharmacokinetic studies. Archival tumor tissue samples are collected and analyzed for the expression of genes that activate the SHH (e.g., Gli1, Gli2, SFRP1, ATOH1, and PTCH2) or WNT (e.g., DKK2 and DKK4) cell signal pathways by in situ hybridization and reverse transcriptase real time-PCR.