IMPROVING CRYOSURGERY THROUGH UNDERSTANDING APOPTOSIS

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DESCRIPTION: (Adapted from the Applicant's Abstract): This Phase I proposal has the overall goal of developing improved cryosurgical treatment for prostate and other cancers by combining a drug (s) which triggers or promote gene activated cell death, or apoptosis, with traditional cryosurgical technique. Preliminary data are presented to support the hypothesis that cell death that occurs when cells are subjected to mild freezing insults (i.e. - minus oC) is a consequence of apoptosis. Anecdotal cryosurgical data have indicated that cancer cells in the middle of a tissue iceball created during cryosurgical procedures die immediately due to necrosis; whereas cells at the iceball periphery where temperatures approach 0oC die several days subsequent to cryoablation, while other cells in this periphery survive the freezing insult altogether. In vitro data provided show that cells frozen at minus 70oC die by necrosis; whereas at least 25% of the cells that die at minus 15 oC succumb via apoptosis. These observations lead to preliminary studies that showed that the addition of non-toxic levels of 5-fluorouracil (5-FU), a well-known apoptotic-inducing anticancer drug, greatly enhances the efficacy of cryo-induced cell killing. Based on these findings, it is proposed to determine if (1) the 5-FU pre-treatment enhancement of freezing-induced cell death is common to other cancer cell types; (2) the addition of other anticancer agents also enhances 5-FU's effect on freezing-induced cell death; (3) other chemotherapeutic compounds exhibit 5-FU-1 effects; (4) freezing-induced apoptosis is related to an increase in cytochrome c release from the mitochondria and/or upregulation of the tumor suppresser gene, p53 and (5) a novel double-label assay can be developed such that the relative number of apoptotic and necrotic cells can be quantified subsequent to an in vitro freezing protocol. Successful completion of these studies should provide basis for the development in Phase II of novel dual function cryoprobe devices that will also deliver chemotherapeutic agents to the tumor and thereby increase patient survival subsequent to cryosurgical treatments. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE