PTCH1 and cancer: Interestingly, the depletion of Ptch1 using specific silencing RNA in the MeWo melanoma cell line induced cell retention of doxorubicin (dxr), a fluorescent chemotherapeutic drug commonly used to treat many types of cancers, while control cells showed a strong decrease of intracellular dxr fluorescence 30 min after the removal of this drug from the medium (Figure 1C).