SMAD4 and neoplasm: In heterotopic tumors generated by subcutaneous injection of tumor organoids driven by APC, Kras, Trp53, and Smad4 mutations and carrying the Lgr5-eGFP-DTR allele, addition of diphtheria toxin (DT) efficiently eliminated Lgr5+ cells and resulted in restriction of tumor growth, although not in tumor regression.