Description

Author: Dr. med. Ralf Herold, Last modification: 2007/09/27

Subject and Importance

The chemotherapy protocols presently established are based on the clinical experience with the combined use of drugs inhibiting the growth of tumor cells in models. Up to now this effect essentially has been explained with interference in DNA synthesis, an induction of chain breaks, or an inhibition of the mitotic spindle apparatus of the cell. In the last years it turned out that cytostatic drugs actually activate the cells signaling pathways for apoptosis, causing it to 'commit suicide'. Blocking these signaling pathways leads to an ineffectiveness of the therapy. The molecules and signaling pathways crucial for apoptosis have been have been identified to a large degree. Today a systematic examination of apoptotic processes in leukemia cells promises to deliver direct clinical implications for a risk adapted therapy.

Problem

One third of all patients with acute lymphatic leukaemia can not be cured by use of the therapy regimes developed on the basis of clinical empiricism because their drugs do not lead to the final elimination of leukaemia cells. In addition, every relapse leads to the selection those cells much more resistant to the cytostatic drugs of a renewed therapy. Up to now sensitivity or resistance of leukaemia cells toward cytostatics was poorly understood. An important concept for the explanantion of cytostatic drug resistance was that of some detoxification mechanisms: carriers in the membrane where belived to remove certain cytostatics from the cell, thus keeping them from finding their intracellular target. The discovery of an activation of cellular apoptosis through cytostatic drugs now shows that sensitivity or resistance are more likely to depend on wether or not drugs are able to cause apoptosis in a direct way. Apoptosis is the cells uniforme response to certain damages which also can be induced by cytostatic drugs. Signaling pathways for apoptosis involve ligand/receptor iteractions, imbalances between proapoptotic and antiapoptotic molecules of the Bcl2 family, disturbances of the mitochindria leeding to liberation of proapoptotic factors, and the activation of caspases. A cells ability to go into apoptosis is likely to be determinded by its ability to activate caspases. Except for some single studys, no systematic reasearch has been done about the expression or induction of molecules relevant for apoptosis during chemotherapeutic treatment of leukemia patients. Doing this research is one of our projects tasks.

Material and Methods

A standardized collection of specimen before and during chemotherapy is essential for the examination. Before beginning a therapy, specimens collected from a apatient underwent centralized typification and analysis for constitutive expression of apoptosis molecules in Professor Ludwig's reference laboratory in Berlin-Buch. This was done in cooperation with the laboratory of the pediatric hospital of the university in Ulm, led by Prof. Dr. Klaus-Michael Debatin und Dr. Karsten Stahnke, where methods and agents for the analysis of proapoptotic systems are being researched. The results are correlated with those of the MTT-test, a simple screening test for resistance towards cytostatics cooperatively established by the lab of Prof. Janka-Schaub (Hamburg) and the pediatric university hospital in Amsterdam. It was found, that the activation of apoptotic signaling pathways is independent from the consecutive expression of molecules during chemotherapy and takes places only in vivo. On the basis of this finding, Prof. Debatin and Dr. Stahnke are working to optimize the available methods for apoptosis activation by cytostatic drugs. Their results are directly used for monitoring the patients undergoing chemotherapy. In addition to this, mutation analysis of molecules crucial for apoptosis is done with centrally collected DNA and RNA. For the in-vivo analysis during chemotherapy a few hospitals collect patient material by use of standardized procedures. These procedures provided by Prof. Debatin und Dr. Stahnke are also used in the cooperation between the research groups in Hamburg and Amsterdam.