Orthotopic Tumour Models

At the Department of Pharmaceutical Chemistry II a broad spectrum of human cancer cell lines is routinely used for a variety of preclinical in vitro investigations prior to in vivo studies. The used panel of cell lines is characteristic of the tumour type under consideration with respect to growth, histopathology and chemoresistence. The in vitro investigations are necessary to obtain data on chemosensitivity of a certain tumour type, e. g. breast cancer, ovarian cancer, to study the concentration cytotoxicity relationships and to get information on times of exposure and inactivation (e. g. binding to plasma proteins). In the next step the activity of a compound which has passed the criteria of the in vitro investigations is determined in a subcutaneous tumour model which was established from the same cancer cell lines. This ‘in vitro/in vivo strategy’ is refined by testing of the most promising drugs or new therapeutic approaches in a corresponding orthotopic tumour model which is as close as possible to the clinical situation.

Such models were, for instance, established for mamma and ovarial carcinoma, the main targets of previous investigations. At present our research is focussed on malignant brain tumours and melanoma, in particular with respect to local treatment of these malignancies.

All these investigations are performed in close cooperation with Dr. T. Spruss (Laboratory Animal Facilities, University of Regensburg).

In spite of recent advances in neurosurgery and radiotherapy, the prognosis for astrocytomas, especially the glioblastoma multiforme is very poor. For the development of new anticancer drugs and novel therapeutic regimens realistic preclinical models are invaluable. Such models should take into account the specific microenvironment of brain tissue (e.g. blood brain barrier, interaction with glia cells) affecting tumor growth as well as delivery and uptake of anticancer drugs.

Therefore, in addition to subcutaneous glioblastoma and astrocytoma models, we established the corresponding intracerebral tumours in nude mice as a prerequisite for pharmacological investigations.

• Development of biodegradable implants for interstitial therapy of malignant brain tumours
Cooperation with Prof. Dr. A. Göpferich (Pharmaceutical Technology, University of Regensburg)

• Non-invasive methods for the control of intracerebral tumour growth in mice

• Preclinical investigations on the adjuvant use of MDR modulators in the chemotherapy of primary brain tumours and brain metastases.

• Enhancement of the antitumour activity of cytostatics by local application of hyaluronidase

Extensive clinical studies on the chemotherapy of malignant melanoma indicate that cures are only achievable at high dosage of the available drugs. The use of such ultrahigh concentration requires techniques for the reduction of non-tolerable toxic side effects. Isolated limb perfusion (ILP) is an experimental therapeutic approach for the treatment of locoregionally metastasized malignant melanoma of the extremities. In contrast to systemic chemotherapy, regional chemotherapy of malignant melanoma, which allows a markedly higher dosage of the drugs, leads to long persisting remissions or even to cures.

As this procedure is still under discussion, animal models could be useful to optimize this treatment. Although a few reports on the perfusion of rats were published, with a single exception (Nagel, K. et al., Res Exp Med (1987) 187: 1-8), in our opinion the described models are very distinct from the clinical situation and are inadequate to simulate the meticulous perfusion technique with the various interdependent parameters. Therefore, we adopted the reliable and efficient miniaturized extracorporal circulation system worked out by Nagel et al. and improved it further. This animal model reflects the clinical situation, allows a detailed investigation of optimal perfusion conditions and enables us to carry out preclinical tumourpharmacological and pharmacokinetic studies to optimize the performance and efficacy of ILP for the clinical setting.

U. Gürtler, P. Fuchs, A. Stangelmayer, G. Bernhardt, A. Buschauer, T. Spruss, Construction and validation of a microprocessor controlled extracorporal circuit in rats for the optimization of isolated limb perfusion. Arch. Pharm. (Weinheim) 337, 672-681 (2004).

S. Fellner, B. Bauer, D. S. Miller, M. Schaffrik, M. Fankhänel, T. Spruß, G. Bernhardt, C. Graeff, L. Färber, H. Gschaidmeier, A. Buschauer and G. Fricker, Transport of paclitaxel (Taxol) across the blood-brain barrier in vitro and in vivo, J. Clin. Invest. 110, 1309 - 1318 (2002).

U. Gürtler, T. Spruss, A. Stangelmayer, G. Bernhardt, A. Buschauer, An Optimized Experimental Model for the Isolated Limb Perfusion of Tumour - Bearing Rats. Arch. Pharm. Pharm. Med. Chem. 333, 43 (2000)

P. Altenschöpfer, T. Spruss, G. Bernhardt, A. Buschauer. Comparison of subcutaneously and orthotopically implanted glioblastomas. International Symposium: Relevance of Tumor Models for Anticancer Drug Development, 15.-17. Oktober 1997, Freiburg, Abstracts, P 1.

I. Muckenschnabel, G. Bernhardt, T. Spruss, A. Buschauer, HPLC-Untersuchungen von Melphalan zur Optimierung der isolierten Extremitätenperfusion. Pharm. u. Z. 25, 143 (1996).

Th. Meyer, C. Christl, I. Muckenschnabel, G. Bernhardt, J. Göhl, W. Hohenberger, A. Buschauer, Essential factors in hyperthermic isolated limb perfusion (HILP) - in vitro studies. J. Cancer Res. Clin. Oncol. 121 (Suppl 2) A 59 (1995).

G. Bernhardt, T. Spruss, M. Rustler, Comparison of MCF-7 and ZR-75-1 cell lines as models for studying hormone dependent human breast cancer in nude mice. In: Fiebig HH, Berger DP (eds), Immunodeficient Mice in Oncology. Contrib. Oncol., Karger, Basel 1992, vol. 42, pp128-130.

T. Spruss, G. Bernhardt, M. Rustler, Characterization of ovarian carcinomas NIH-OVCAR-3 and SK-OV-3 growing in the ovary of nude mice. In: H. H. Fiebig, D. P. Berger (eds), Immunodeficient Mice in Oncology. Contrib. Oncol., Karger, Basel 1992, pp 135-137.