Scientific Report 2003-2004 - Cleveland Clinic Lerner Research ...

The Department of Cancer BiologyContinued from Page 44William Isaacs of Johns Hopkins University, Dr.Silverman of the Cleveland Clinic, and othercollaborators (Nature Genetics 2002;30:181-4).Subsequently, Drs. Casey and Silverman(Cleveland Clinic) with Dr. John Witte (CaseWestern Reserve University) reported that asingle amino acid change in RNase L is implicatedin as many as 13% of unselected prostatecancer cases (Nature Genetics 2002;32:581-3).These findings suggest the involvement of RNaseL in both hereditary and unselected cases ofprostate cancer. This important development inprostate cancer research could provide anopportunity to screen men for mutations thatcause early-onset disease, thereby allowing earlytreatment, or form the basis for the developmentof a new drug or gene therapy for prostatecancer. A small molecule called 2-5A causesRNase L to become active in cells and leads tothe death of prostate cancer cells. Our hope isthat these studies will lead to a better understandingof how prostate cancer develops.In the NIH-funded George M. O’BrienUrology Research Center, Dr. Warren (Skip)Heston has described prostate-specific membraneantigen (PSMA) as a potential target in prostatecancer patients. PSMA is a type-2 membraneprotein expressed in the prostate and highlyexpressed in metastatic or poorly differentiatedadenocarcinomas. Moreover, PSMA expression isupregulated by androgen deprivation. New radioimmunoconjugateforms of anti-PSMA monoclonalantibody are being used to diagnoseprostate cancer metastasis and recurrence. Therehave also been promising results from Phase Iand II trials using PSMA as a therapeutic target(Urol. Oncol. 2002;7:7-12). Recently, PSMAexpression in endothelial cells of tumorassociatedneovasculature has been described,suggesting a role in tumor angiogenesis anddefining a new target for therapeutic approachesfor all solid tumors.Another important discovery was recentlymade in collaboration with scientists at theNational Institutes of Health. Dr. NicholasRestifo’s group in the National Cancer Institute’sSurgery branch have produced a naked DNAvaccine encoding an alphavirus replicon (selfreplicatingmRNA) and the self/tumor antigentyrosinase-related protein-1. In collaborationwith Drs. Williams and Silverman, his groupshowed that, unlike conventional DNA vaccines,this vaccine can break tolerance and provideimmunity to melanoma. The vaccine mediatesproduction of double-stranded RNA (dsRNA),leading to the activation of the dsRNAdependentprotein kinase R (PKR). This dsRNAproduction was shown to be critical to vaccinefunction because the vaccine’s immunogenicityand anti-tumor activity are blocked in micedeficient for RNase L. This novel study showsthat alphaviral replicon-encoding DNA vaccinesactivate innate immune pathways known to driveantiviral immune responses and suggests strategiesfor improving the efficacy of immunization withnaked DNA by manipulating these pathways.The adenylate uridylate-rich elements(AREs) mediate the rapid turnover of mRNAsencoding proteins that regulate cellular growthand response to exogenous agents such asmicrobes and inflammatory and environmentalstimuli. However, the full repertoire of AREcontainingmRNAs is unknown. Dr. Williams andDr. Khalid Khabar (Adjunct Staff in thisdepartment; King Faisal Hospital ResearchCenter, Riyadh, Saudi Arabia) have explored thedistribution of AREs in human mRNA sequencesand arrived at a computationally derived AREpattern that is the basis of a database containingnonredundant, full-length ARE-mRNAs (NucleicAcids Res. 2001;29:246-54; 2003;31:421-3). TheARE-mRNA database (ARED) reveals that AREmRNAsencode a wide repertoire of functionallydiverse proteins that belong to different biologicalprocesses and are important in several diseasestates. This database has been used to design acustom cDNA array of the entire spectrum ofARE-containing genes checked for p38-dependentregulation of ARE-mediated mRNA turnover. Inaddition, the half-lives of 470 AU-rich mRNAswere determined and a feedback loop identifiedthat regulates macrophage signaling via p38 MAPkinase-dependent transcript stabilization (Mol.Cell. Biol. 2003;23:425-36).Findings from Dr. Clemencia Colmenares’laboratory have suggested that the Skiprotooncogene is involved in neural tubedevelopment and muscle differentiation. Inagreement with this result, the group has foundthat Ski-/- mice display a cranial neural tubedefect that results in exencephaly and a markedreduction in skeletal muscle mass. They haveshown that the penetrance and expressivity of thephenotype changes when the null mutation isbackcrossed into the C57BL6/J background, withthe principal change involving a switch from aneural tube defect to midline facial clefting(Nature Genetics 2002;30:106-9). This phenotypeis found in individuals diagnosed with 1p36deletion syndrome, a disorder caused by monosomyof the short arm of human chromosome 1p.Dept. website:http://www.lerner.ccf.org/cancerbio/Continued on Page 4645