When tested in organotypic cultures, we observed that all the control cells bearing an empty lentiviral vector (referred to as “pLKO” cells) form in all cases unstructured tumor masses composed of highly proliferative (Ki67+) and undifferentiated (keratin 14+, involucrin–) cell layers according to immunohistochemical staining (Fig. 9a). Here, IVL is linked to neoplasm.