BOETTGER, S.A.; KELLEHER, A.L.; JERSZYK, E.C.; WALKER, C.W.; The University of New Hampshire, Durham; The University of New Hampshire, Durham; The University of New Hampshire, Durham; The University of New Hampshire, Durham: Clam Leukemia: A Pre-Clinical Model for Evaluating Topoisomerase II Inhibitors

This study combines the use of traditional and novel topoisomerase II inhibitors promoting p53/73 dependent apoptosis with a naturally occurring cancer model resembling human Burkitt�s and other lymphomas. Analyzing the effects of cytotoxic compounds on malignancy is currently limited to vertebrate models, which are expensive to maintain and highly regulated. The objective of this research is to use the softshell clam, Mya arenaria, to identify novel p53/73 dependent molecular mechanisms. Further information on the roles of p53/73 in blood cancers can be gained by treatment with topoisomerase II inhibitors already utilized or proposed for human cancer chemotherapy. Etoposide was administered in vivo and clam hemocytes were examined for the cellular localization of p53 and MDM2 prior to and following drug exposure. Immunocytochemistry indicated movement of both p53 and MDM2 from the cytoplasm into the nucleus followed by an increase in apoptotic cells and a subsequent decrease in viable cells/ml blood. Mitoxantrone was administered to leukemic clam hemocytes in vitro in increasing concentrations (0-70 mM). Cell proliferation and p53 localization were examined following mitoxantrone exposure. Cell proliferation was not dependent on mitoxantrone concentrations with p53 localization displaying similar results. Occurrence of nuclear p53 and MDM2 as well as decreased cell proliferation, cell numbers and sizes indicate that etoposide may initiate cell death through apoptosis while mitoxantrone alone does not appear to initiate cell death. The clam cancer model may thus provide a useful tool in early testing of anti-cancer drugs.(Supported by NCI to CWW)