Overview of the variety of available xenograft models. Most frequently used are s.c. growing xenografts from cell lines and patient explants. The histology of a large cell lung cancer (LXFL 529) is shown for the original patient tumor (A), the xenograft from this patient specimen after passage 5 in the mouse (B), and for the xenograft derived from a permanent cell line of LXFL 529 after s.c. injection (C). The similarity of (A) to (C) indicates that human tumor xenografts can closely resemble clinical disease. Xenografts derived from patient explants correctly predicted response in 90% (19 of 21 tumors) and resistance in 97% (57 of 59 tumors; ref.