mkt-077 and Disease-Models--Animal

As Jessani et al.,(1) point out development of cell and animal models that accurately depict human tumorigenesis remains a major goal of cancer research. Clam cancer offers significant advantages over traditional models for genotoxic and non-genotoxic preclinical analysis of treatments for human cancers with a similar molecular basis. The naturally occurring clam model closely resembles an outbreeding, human clinical population and provides both in vitro and in vivo alternatives to those generated from inbred mouse strains or by intentional exposure to known tumor viruses. Fly and worm in vivo models for adult human somatic cell cancers do not exist because their adult somatic cells do not divide. Clam cancer is the best characterized, naturally occurring malignancy with a known molecular basis remarkably similar to those observed in several unrelated human cancers where both genotoxic and non-genotoxic strategies can restore the function of wild-type p53. To further emphasize this point of view, we here demonstrate a p53-induced, mitochondrial-directed mechanism for promoting apoptosis in the clam cancer model that is similar to one recently identified in mammals. Discerning the molecular basis for naturally occurring diseases in non-traditional models and correlating these with related molecular mechanisms responsible for human diseases is a virtually unexplored aspect of toxico-proteomics and genomics and related drug discovery.

Topics: Animal Diseases; Animals; Antineoplastic Agents; Apoptosis; Brachyura; Disease; Disease Models, Animal; DNA Damage; Drug Evaluation, Preclinical; HSP70 Heat-Shock Proteins; Humans; Molecular Sequence Data; Neoplasms; Pyridines; Signal Transduction; Thiazoles; Tumor Suppressor Protein p53

Among heat shock proteins, mortalin has been linked to the pathogenesis of Parkinson's disease. In the present work a rat model of Parkinson's disease was used to analyze the expression of striatal proteins and, more specifically, mortalin expression. The possible involvement of mortalin in Parkinson's disease pathogenesis was further investigated by utilizing an electrophysiological approach and pharmacological inhibition of mortalin in both the physiological and the parkinsonian states. Proteomic analysis was used to investigate changes in striatal protein expression in the 6-hydroxydopamine rat model of Parkinson's disease. The electrophysiological effects of MKT-077, a rhodamine-123 analogue acting as an inhibitor of mortalin, were measured by field potential recordings from corticostriatal brain slices obtained from control, sham-operated, and 6-hydroxydopamine-denervated animals. Slices in the presence of rotenone, an inhibitor of mitochondrial complex I, were also analyzed. Proteomic analysis revealed downregulation of mortalin in the striata of 6-hydroxydopamine-treated rats in comparison with sham-operated animals. MKT-077 reduced corticostriatal field potential amplitude in physiological conditions, inducing membrane depolarization and inward current in striatal medium spiny neurons. In addition, we observed that concentrations of MKT-077 not inducing any electrophysiological effect in physiological conditions caused significant changes in striatal slices from parkinsonian animals as well as in slices treated with a submaximal concentration of rotenone. These findings suggest a critical link between mortalin function and mitochondrial activity in both physiological and pathological conditions mimicking Parkinson's disease.

Topics: Action Potentials; Animals; Antiparasitic Agents; Cerebral Cortex; Corpus Striatum; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Electron Transport Complex I; Gene Expression Regulation; HSP70 Heat-Shock Proteins; In Vitro Techniques; Male; Neurons; Oxidopamine; Parkinson Disease; Proteomics; Pyridines; Rats; Rats, Wistar; Thiazoles

In nature the soft shell clam Mya arenaria develops a fatal neoplasm that shares molecular similarity with an unrelated group of human cancers. In leukemic clam hemocytes, wild-type p53 and mortalin proteins co-localize in the cytoplasm. A similar phenotype, characterized by cytoplasmic sequestration of wild-type p53 protein, has been observed in several human cancers (undifferentiated neuroblastoma, retinoblastoma, colorectal and hepatocellular carcinomas, and glioblastoma). In some of these cancers p53 is tethered in the cytoplasm by mortalin when the latter protein is overexpressed. Using co-immunoprecipitation we have demonstrated that mortalin and p53 proteins are complexed in the cytoplasm of leukemic clam hemocytes (and not in normal hemocytes). In addition, treatment of leukemic clam hemocytes with MKT-077, a cationic inhibitor of mortalin, disrupts the interaction of mortalin and p53 proteins, resulting in translocation of some p53 to the nucleus. Based on these data, we introduce leukemic clam hemocytes as novel and easily accessible, in vivo and in vitro models for human cancers displaying a similar mortalin-based phenotype. Treatment of these models with novel chemotherapeutics may help reveal the molecular mechanism(s) involved in inactivating p53 by this form of cytoplasmic sequestration.

Topics: Animals; Cytosol; Disease Models, Animal; Hemocytes; HSP70 Heat-Shock Proteins; Immunohistochemistry; Immunoprecipitation; Leukemia; Molecular Sequence Data; Mya; Neoplasms; Pyridines; Subcellular Fractions; Thiazoles; Tumor Suppressor Protein p53