Doxorubicin's intercalant and topoisomerase inhibition in leukemia?
Doxorubicin is part of chemotherapy drugs. Most of them are targeting proliferation of cells, e.g. by blocking cell division or DNA replication.

Intercalants and topoisomerase inhibitors are powerful in interfering with DNA replication (not DNA activity). Other chemo drugs might inhibit proper operation of cell division machinery, such as through interfering with cytoskeleton functions.