The role of transcriptional repression in the tumor response to TOP2 inhibitors
Final Report Abstract
The DNA topology enzyme and anticancer drug target TOP2A has been implicated in the regulation of gene expression. We investigated if TOP2A poisoning by the widely used anticancer drugs doxorubicin (DOX) and etoposide (VP16) alters gene expression and if these alterations affect the survival of cancer cells. In untreated cells, TOP2A was enriched within promoters of highly expressed genes. VP16 and DOX attenuated these enrichments by increasing TOP2A binding to non-promoter gene regions. This was accompanied by the depletion of Pol II from promoters, formation of double-stranded DNA breaks (DSB), gene expression changes, and apoptosis. The formation of DSB and apoptosis were contingent upon the presence of TOP2A. In contrast, the depletion of TOP2A prevented drug-conferred gene repressions, but not inductions. Five out of 23 investigated, highly expressed genes repressed by these drugs in a TOP2A- dependent manner decreased cell survival when knocked down with siRNA. In conclusion, similarly to what has been observed in embryonic stem cells, in cancer cells TOP2A binds to promoters of highly expressed genes. These genes undergo repression upon treatment with TOP2A poisons which appears to be mediated by DNA damage resulting from cleavable complexes of drug, TOP2A, and DNA. The repression of some of these genes contributes to the cytotoxicity of TOP2A poisons. Our work identifies first specific transcriptional effectors of TOP2 poisoning relevant to cancer cell survival.
