<p>This thesis describes the use of a new technology, the Cytosensor^® microphysiometer, in the in vitro evaluation of cytotoxic drugs, using the lymphoma cell line U-937 GTB and primary cultures of tumour cells from patients as model systems. The method was specifically applied to study the metabolic effects of the novel cyanoguanidine N-(6-(4-chlorophenoxy)hexyl)-N’-cyano-N’’-4-pyridylguanidine, CHS 828, currently in phase I/II clinical trials. </p><p>The Cytosensor^® measures metabolic effects as changes in the rate of extracellular acidification of cells exposed to a drug by perfusion. A number of standard cytotoxic drugs were found to produce typical and reproducible acidification response patterns during observation times up to 20 h. There seemed to be a relationship between a decrease in acidification and cytotoxicity, measured in the fluorometric microculture cytotoxicity assay (FMCA), after 20-24 h of continuous drug exposure.</p><p>In U-937 cells, CHS 828 induced a cytotoxic effect characterised by a steep concentration-response relationship followed by a plateau. After 24 h of incubation the DNA and protein synthesis were turned off. CHS 828 was found to produce a rapid and prolonged increase in extracellular acidification and lactate production similar to that of the structurally related mitochondrial inhibitor m-iodobenzylguanidine (MIBG). The CHS 828 induced acidification was observed in cell lines as well as in cells from various tumour types from patients and probably originates from increased glycolytic flux. The effects may be secondary to block of oxidative phosphorylation in the mitochondria, but the relevance of the early acidification is not clear. CHS 828 seemed to induce a late, at approximately 15 h, inhibition of the glycolysis followed by loss of ATP and subsequent cell death. After exposure to MIBG the loss of ATP and cell death occurred earlier and in parallel. The effects of CHS 828 were not found to resemble those of the structurally related polyamine biosynthesis inhibitor methylglyoxal-bis(guanyl-hydrazone) (MGBG). Thus, CHS 828 may represent a new and, thus, interesting mode of cytotoxic action worthwhile for further development.</p><p>In combinatory studies, a synergistic interaction was demonstrated between CHS 828 and the non-toxic drug amiloride. Additive-to-synergistic effects were also seen between CHS 828 and the bioreductive cytotoxic drug mitomycin C. In U-937 cells as well as in tumour cells from patients, CHS 828 demonstrated synergistic interactions in combination with melphalan and etoposide. </p><p>It is concluded that measurement in the Cytosensor^® microphysiometer of early cellular metabolic changes is a feasible and potentially valuable complement to more conventional methods used in the evaluation of anticancer agents. </p>

This thesis describes the use of a new technology, the Cytosensor® microphysiometer, in the in vitro evaluation of cytotoxic drugs, using the lymphoma cell line U-937 GTB and primary cultures of tumour cells from patients as model systems. The method was specifically applied to study the metabolic effects of the novel cyanoguanidine N-(6-(4-chlorophenoxy)hexyl)-N’-cyano-N’’-4-pyridylguanidine, CHS 828, currently in phase I/II clinical trials. The Cytosensor® measures metabolic effects as changes in the rate of extracellular acidification of cells exposed to a drug by perfusion. A number of standard cytotoxic drugs were found to produce typical and reproducible acidification response patterns during observation times up to 20 h. There seemed to be a relationship between a decrease in acidification and cytotoxicity, measured in the fluorometric microculture cytotoxicity assay (FMCA), after 20-24 h of continuous drug exposure. In U-937 cells, CHS 828 induced a cytotoxic effect characterised by a steep concentration-response relationship followed by a plateau. After 24 h of incubation the DNA and protein synthesis were turned off. CHS 828 was found to produce a rapid and prolonged increase in extracellular acidification and lactate production similar to that of the structurally related mitochondrial inhibitor m-iodobenzylguanidine (MIBG). The CHS 828 induced acidification was observed in cell lines as well as in cells from various tumour types from patients and probably originates from increased glycolytic flux. The effects may be secondary to block of oxidative phosphorylation in the mitochondria, but the relevance of the early acidification is not clear. CHS 828 seemed to induce a late, at approximately 15 h, inhibition of the glycolysis followed by loss of ATP and subsequent cell death. After exposure to MIBG the loss of ATP and cell death occurred earlier and in parallel. The effects of CHS 828 were not found to resemble those of the structurally related polyamine biosynthesis inhibitor methylglyoxal-bis(guanyl-hydrazone) (MGBG). Thus, CHS 828 may represent a new and, thus, interesting mode of cytotoxic action worthwhile for further development. In combinatory studies, a synergistic interaction was demonstrated between CHS 828 and the non-toxic drug amiloride. Additive-to-synergistic effects were also seen between CHS 828 and the bioreductive cytotoxic drug mitomycin C. In U-937 cells as well as in tumour cells from patients, CHS 828 demonstrated synergistic interactions in combination with melphalan and etoposide. It is concluded that measurement in the Cytosensor® microphysiometer of early cellular metabolic changes is a feasible and potentially valuable complement to more conventional methods used in the evaluation of anticancer agents.

<p>Despite major advances in the understanding of the biology of chronic lymphocytic leukaemia (CLL), progress in improving its treatment has been limited and it still remains an incurable disorder. In the present research, we have performed <i>in vitro</i> drug sensitivity testing of primary CLL cells for preclinical evaluation of cytotoxic drugs, using the fluorometric microculture cytotoxicity assay (FMCA).</p><p>The tumour type-specific activities of 14 standard drugs, evaluated <i>in vitro</i> on tumour cells from patients with CLL and acute leukaemias, were in good agreement with their known clinical activities. A correlation between drug treatment and development of cellular drug resistance was demonstrated in CLL, but not in the acute leukaemias. Moreover, the nucleoside analogues fludarabine, cladribine, cytarabine and gemcitabine, as well as the anthracycline idarubicin, were highly active in CLL cells.</p><p>A new cytotoxic drug candidate, CHS 828, was evaluated in primary cell cultures from a broad spectrum of tumours. CHS 828 was highly active against haematological malignancies <i>in vitro</i>, especially CLL, but also against some solid tumours. The drug appeared to be non cross-resistant with standard drugs.</p><p>In addition, the relationship between drug sensitivity <i>in vitro</i> and a recently described prognostic factor in CLL, the mutational status of the immunoglobulin variable heavy chain (IgV_H) gene, was evaluated. Interestingly, cells with unmutated IgV_H genes were more chemosensitive than the mutated cells. </p><p>In summary, our results indicate that <i>in vitro</i> studies on tumour cellsfrom leukaemia patients may yield considerable information regarding the activity, mechanisms of action and cross-resistance of cytotoxic drugs, as well as concerning the relationship between drug sensitivity and prognostic factors, which can be useful in the preclinical evaluation of new cytotoxic drugs. Furthermore, the results suggest that the pyrimidine analogues cytarabine and gemcitabine, as well as the anthracycline idarubicin, may have a role in the treatment of CLL. The new cyanoguanidine CHS 828 is highly active in CLL cells and appears to be non cross-resistant with standard drugs. The poorer prognosis in patients with CLL cells with unmutated IgV_H genes can not be explained by increased chemoresistance.</p>

Despite major advances in the understanding of the biology of chronic lymphocytic leukaemia (CLL), progress in improving its treatment has been limited and it still remains an incurable disorder. In the present research, we have performed in vitro drug sensitivity testing of primary CLL cells for preclinical evaluation of cytotoxic drugs, using the fluorometric microculture cytotoxicity assay (FMCA). The tumour type-specific activities of 14 standard drugs, evaluated in vitro on tumour cells from patients with CLL and acute leukaemias, were in good agreement with their known clinical activities. A correlation between drug treatment and development of cellular drug resistance was demonstrated in CLL, but not in the acute leukaemias. Moreover, the nucleoside analogues fludarabine, cladribine, cytarabine and gemcitabine, as well as the anthracycline idarubicin, were highly active in CLL cells. A new cytotoxic drug candidate, CHS 828, was evaluated in primary cell cultures from a broad spectrum of tumours. CHS 828 was highly active against haematological malignancies in vitro, especially CLL, but also against some solid tumours. The drug appeared to be non cross-resistant with standard drugs. In addition, the relationship between drug sensitivity in vitro and a recently described prognostic factor in CLL, the mutational status of the immunoglobulin variable heavy chain (IgVH) gene, was evaluated. Interestingly, cells with unmutated IgVH genes were more chemosensitive than the mutated cells. In summary, our results indicate that in vitro studies on tumour cellsfrom leukaemia patients may yield considerable information regarding the activity, mechanisms of action and cross-resistance of cytotoxic drugs, as well as concerning the relationship between drug sensitivity and prognostic factors, which can be useful in the preclinical evaluation of new cytotoxic drugs. Furthermore, the results suggest that the pyrimidine analogues cytarabine and gemcitabine, as well as the anthracycline idarubicin, may have a role in the treatment of CLL. The new cyanoguanidine CHS 828 is highly active in CLL cells and appears to be non cross-resistant with standard drugs. The poorer prognosis in patients with CLL cells with unmutated IgVH genes can not be explained by increased chemoresistance.