Despite some advances in the use of chemotherapy for treatment of women with ovarian cancer, the majority of women succumb to their disease. In the present project we propose to test a new approach to the modulation of tumor progression and drug resistance in these patients by targeting extrachromosomal DNA. It has long been recognized that double minutes found in metaphase spreads made from human tumors can harbor amplified copies of oncogenes and amplified copies of drug resistance genes. Double minutes are extrachromosomally located DNA which is susceptible to elimination from the cell. We have documented that the antitumor agent hydroxyurea, at clinically achievable concentrations, can eliminate extrachromosomally located double minutes containing amplified oncogenes or amplified drug resistance genes from human tumor cell lines. The first specific aim of the present study is to determine if hydroxyurea given to patients can cause elimination of extrachromosomal DNA from women's ovarian cancer cells. To accomplish this specific aim, women with advanced refractory ovarian cancer with refractory malignant ascites requiring frequent paracentesis for comfort, will be treated with hydroxyurea. The effect of hydroxyurea on the amount of extrachromosomal DNA will be assessed by directly counting the number of double minutes in metaphase spreads as well as by utilizing molecular techniques to measure the amount of circular extrachromosomal DNA both before and after the treatment of the patients with hydroxyurea. Our second specific aim is to determine the effect of hydroxyurea on other ovarian cancer cell parameters including the number and percentage of tumor cells in the ascites, the ability of the cells to clone in soft agar, and, the number of micronuclei per 1000 tumor cells. These parameters will give some indication as to whether or not hydroxyurea is causing a change in cell population phenotype. If hydroxyurea causes a substantial decrease in extrachromosomal DNA in an in vivo situation it is likely that those findings can be used to develop a new therapeutic strategy. Elimination of oncogene containing extrachromosomal DNA by hydroxyurea (or other agents) could modulate tumor progression. Elimination of drug resistance gene containing extrachromosomal DNA could modulate drug resistance.
|Langevin, Anne-Marie; Weitman, Steven D; Kuhn, John G et al. (2003) Phase I trial of rebeccamycin analog (NSC #655649) in children with refractory solid tumors: a pediatric oncology group study. J Pediatr Hematol Oncol 25:526-33|