Observations regarding DNA replication sites in human cells in vivo following infusions of iododeoxyuridine and bromodeoxyuridine

In studies using bromodeoxyuridine (BrdUrd) and/or iododeoxyuridine (IdUrd) to label S phase cells in cancer patients, several unique observations were made regarding DNA replication sites and the organization of newly synthesized DNA in post-mitotic cells. While the majority of tumour specimens removed at the end of infusions demonstrated concentration of replication sites around the nuclear membrane, biopsies obtained in leukaemic patients 1 week later demonstrated several distinct patterns of labelling. For example, one, two or all lobes of granulocytes were labelled. Scavenger macrophages bearing labelled leukaemic cells in their cytoplasm were also seen. Sequential IdUrd/BrdUrd labelling of solid tumours showed various patterns of nuclear/nucleolar/membrane labelling, allowing more precise localization of early versus late replication sites.