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Prof. Paul D. Roepe
Department of Chemistry,
Department of Biochemistry and Molecular Biology, 
and Program in Tumor Biology, Lombardi Cancer Center
Georgetown University 
(Offices: Basic Science 353, Reiss 624A)
(202)687-7300 Office; (202)687-5768 Lab;  roepep@georgetown.edu​)
 
The focus of our laboratory is to elucidate the molecular details of drug resistance mechanisms.  Two examples that we currently study in depth are "multidrug resistant" tumor cells and malarial parasites.  Although at first glance these two topics might seem unrelated, we and others have discovered interesting parallels between these two types of drug resistance.  Thus, we are optimistic that in the long term we may define biochemical principles that are applicable to these and other drug resistance phenomena as well (i.e. various forms of bacterial drug resistance).
 
In this work we use a variety of interdisciplinary techniques including recombinant DNA methods and novel cell imaging techniques, along with the more traditional tools of chemistry and biochemistry.  For example, shown below is a fluorescent image of a living human red blood cell infected with a single malarial parasite and stained with a probe for membrane potential.  These data are collected in less than 40 msec while the infected cell is under constant perfusion with physiologically relevant buffer.  The picture represents one "slice" that is about 0.25 microns thick.  Adding 25 - 30  of these slices together as we image through the infected red blood cell allows us to reconstruct a 3D "movie" of the living parasite inside an infected red blood cell.  Importantly, all the data can be collected in about 1 second. 
 
Click on this image for a 3D movie of a living P. falciparum parasite inside a human red blood cell! Importantly, the red cell is under continuous perfusion with physiologic buffer. To our knowledge, this movie is the first spinning disk confocal imaging of a living malarial parasite growing within a human red blood cell
Click on this image for a movie showing individual nuclei of a dividing intraerythrocytic parasite.  Each green sphere is a merozoite nucleus. Merozoites will invade new red blood cells when the host cell lyses.  (Imaged using SYBR Green I [Bennett et. al. 2004. AAC 48(5):1807-1810.]
 
 
With novel techniques such as this, we are able to examine the intracellular physiology and biochemistry of malarial parasites in great detail. 
 
Worldwide, 2 - 3 million people die of malaria each year, and about half that number die of various cancers.  A substantial and rapidly growing fraction of these deaths are attributable to parasites or tumors that have become resistant to various drugs due to sub-lethal exposure to these chemicals.  In one well -studied example, exposure of tumor cells to anthracyclines, vinca alkaloids, or other natural product chemotherapeutic drugs induces overexpression of a fascinating polytopic integral membrane protein called hu MDR 1 or P-glycoprotein (Pgp). Overexpression of hu MDR 1 can be caused by exposure to only one drug, yet cells overexpressing the protein exhibit resistance to many different drugs (that is, they are multidrug resistant). In laboratory experiments, overexpression upon drug exposure occurs in many different types of tumor cells, and in the cancer clinic it can be associated with drug resistance in some tumors, particularly tumors of hematopoietic lineage (






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