NOVEL NUCLEOSIDES FOR IMAGING DURING CANCER THERAPY

DESCRIPTION: Cancer treatment by gene therapy, in which an exogenous gene is introduced into tumor cells, is receiving increasing attention. Metabolism of a specific substrate by the enzyme encoded by the transduced gene produces a substance toxic to the tumor. In the most common approach, the gene for the Herpes Virus Thymidine Kinase has been introduced by retroviral transduction. Although promising, development of treatment protocols is limited by the difficulty of determining the efficiency of transduction and the extent of HSV1-TK expression. Knowledge of the level of expression, the optimal time for application substrate, and the time over which treatment is feasible would be of considerable value in guiding the clinician. A noninvasive, clinical method for imaging cells and tissues would greatly enhance the likelihood of successful therapy. In applicants earlier work a radioiodinated fluorouracil analogue, FIAU, was shown in an animal tumor model to be a promising imaging substrate with acceptable selectivity and specificity. Although these data were encouraging, more active substrates which display greater selectivity and specificity would be of considerable value. Based on the preliminary data applicants propose to synthesize a series of xylo- nucleoside analogues (Figure 1) that show enhanced activity as substrates for HSV1-TK. These compounds will be radioiodinated and tested for enhanced selectivity and specificity in a cell line based assay. Promising candidates will be tested for activity as imaging substrates in an animal tumor model. In Phase II applicants will develop additional compounds based on the leads developed in Phase I. The applicants will expand the preclinical testing of promising candidates so as to define pharmacologic issues of clearance, retention, organ distribution, etc. They will also develop a program to produce variants of the HSV-TK. These will be challenged with the new compounds to find the most active combination of variant enzyme and novel substrate. $ = TOTAL AWARD AMTS & NOT LIMITED TO PORTION OF PROJECT RELATED TO SUBJECT OF SEARCH SUBPROJECT $ = TOTAL AWARD AMOUNT DIVIDED BY NUMBER OF SUBPROJECTS SOURCE: CRISP FORMAT F FY 97 LAST UPDATE 04-07-98 1QUERY 1536 ID SEARCH 06/01/98 PAGE 224 --PROJECT NUMBER......1 R43 CA76990-01 INVESTIGATOR NAME/ADDRESS FY 97 TAN, KUT-NIE H IRG/INTRAMURAL UNIT..ZRG3 NORFOLK DEVELOPMENT GROUP, INC AWARD AMOUNT......... $100,000 PO BOX 470 RANDOLPH, MA 02368 PERFORMING ORGANIZATION: NORFOLK DEVELOPMENT GROUP, INC. TITLE NOVEL THERAPEUTIC TUMOR SPECIFIC APOPTOTIC FACTOR ABSTRACT: NOD-5 is a CD4+ T cell clone that we have isolated from the nonobese diabetic (NOD) mouse. This T cell clone and a hybridoma derived from it produce a novel soluble biological activity which induces apoptosis in a variety of tumor cell lines, including B and T lymphoma and leukemia cell lines, transformed fibroblastic cell lines, pancreatic beta-islet tumor and pituitary tumor cell lines. The activity, TAA (tumor apoptotic activity) is protease sensitive and is estimated to be 10-20 kDa by gel filtration and sucrose gradient sedimentation. This activity is distinct from the TNF-alpha/beta, perforin, and Fas mediated apoptosis pathways. Analysis of its activity against a variety of target cell types reveals striking tumor cell specificity in genetically matched fibroblasts. Of particular interest is the ability of TAA to kill p53-deficient tumor cell line. The p53 gene has been implicated as one of the most commonly mutated genes in human cancer. Nearly all human tumors have been shown to harbor p53 mutations. Cell lines containing either p53 mutations or deletions are resistant to radiation induced apoptosis, implicating p53 in mediating death in this setting. Clinical studies have shown that mutations in p53 are correlated with worsened prognosis in many of the most common human malignancies. The ability of TAA to kill p53-=deficient tumor cells holds great promise as a natural nontoxic immunotherapeutic agent for treatment of tumors harboring p53 mutations, which are often resistant to treatment by common antineoplastic therapies. The phase I objective is to purify TAA to homogeneity and to determine the amino acid sequences of tryptic peptides derived form th purified TAA. This will provide the basis for phase II work, which will be to clone the TAA cDNA, to generate active recombinant TAA protein (rTAA), and to test rTAA for efficacy in treatment of malignancies in animal models.