AbstractsOther

x, 93 leaves : ill. ; 29 cm Most cancer treatments are genotoxic agents that target and damage DNA as part of their mechanism of action. Recently, it was discovered that cancer cells with damaged DNA can escape the DNA damage checkpoint and enter into mitosis, a process known as checkpoint adaptation. I used the human colon carcinoma cell line (HT-29) as a model to examine checkpoint adaptation in cells treated with camptothecin (CPT), a topoisomerase I inhibitor that damages DNA. Survival and clonogenic assays revealed that approximately between 1-3% of the cells that undergo checkpoint adaptation are able to survive CPT treatment. Immunofluorescence microscopy disclosed that approximately 90% of the surviving cells were negative for histone -H2AX, whereas, in parallel, the alkaline comet assay revealed that 73% of the cells displayed comets. Karyotype analysis showed survival cells had 35 chromosomes on average, whereas non-treated cells contained 65. FISH analysis revealed that survival cells appear to have major changes in chromosome structure because 45% of the chromosomes were missing telomeres and 28% of the telomeres were located in positions other than the tips of chromosomes. These findings provide valuable information about the integrity of the genome of cancer cells that survive checkpoint adaptation.