AIDS-KAPOSI'S SARCOMA CELLS DEMONSTRATE INCREASED SUSCEPTIBILITY TO A REDOX CYCLING DRUG.

Abstract

29 Background: It is well accepted that cytokines contribute to the pathogenesis of AID-related Kaposi's sarcoma (AIDS-KS). Further, because AIDS-KS cells demonstrate high autologous production of growth promoting cytokines, existing AIDS-KS lesions can function not only to promote their own growth, but also to stimulate development of new tumor foci. Our laboratory is currently developing sustained release drug delivery vehicles to be used in the treatment of patients with early mucocutaneous AIDS-KS. Because data from our laboratory have shown that AIDS-KS cells possess significantly lower levels of oxidant stress protective compounds such as glutathione (GSH), we hypothesized that AIDS-KS cells would demonstrate enhanced cytotoxicity in response to chemotherapeutic agents which promote redox cycling e.g. doxorubicin (dox). Methods: Human cell strains isolated from HIV donors (norm), AIDS-KS cells (KS), and nonlesional cells from the AIDS-KS donors (non) were challenged with dox and assessed for: 1) inhibition of proliferation (BrdU incorporation), 2) alterations in cellular GSH and nucleotide levels (spectrophotometric and HPLC assays, respectively). Concurrent viability studies (trypan blue exclusion) showed cell population specific viability differences after dox exposure (4 μg/ml), with both the norm (p<0.018), and the non (p<0.010) strains demonstrating statistically significantly higher viabilities relative to KS cells. (Kruskal Wallis ANOVA, 2 tailed Mann Whitney U). In addition, BrdU labeling studies indicate that dox is more effective at inhibiting DNA synthesis in KS cells relative to either non or norm cell populations. Ongoing studies to assess the contribution of the thiol redox status in cellular response to redox active concentrations of dox (50 μg/ml) show: 1) Thiol augmentation (addition of 30 mM N-acetylcysteine) is cytoprotective and results in preservation of the cellular energy charge, high energy phosphates and GSH levels., 2) In contrast, GSH depletion prior to dox challenge significantly sensitizes the cells as reflected by marked decreases in cellular viabilities, loss of both high energy phosphates and cellular energy charges, and an oxidation of the redox state. Conclusion: Our findings suggest that the cellular thiol redox status modulates cellular responsiveness to redox cycling agents. Further, our data showing that AIDS-KS cells are more susceptible to the redox active concentrations of dox, provide a biochemical basis for the recognized clinical efficacy of this drug. Therefore, we anticipate that our proposed treatment modality, which will provide high local drug concentrations without the systemic side effects, e.g. cardiotoxicity, is a promising route for early intervention in the treatment of AIDS-KS. NIH support: HL RO-1 48547, DE R-O1 12183, CA U-O1 66351.