DICER1 and cholangiocarcinoma: More recently, two studies point toward Dicer-dependent nuclear RNAi in mammals by demonstrating that nuclear, chromatin-associated Dicer impairs expression of the microtubule-binding protein Doublecortin in mouse adult neural stem cells [14] and transactivation of the human secreted frizzled-related protein 1 promoter in cholangiocarcinoma cells [15].