Monitoring of Interaction Prodcuts of cis-Diamminedichloroplatinum(II) and cis-Diammine(1,1-cyclobutanedicarboxylato)platinum(II) with DNA in Cells from Platinum-treated Cancer Patients¹

The formation and stability of interaction products between the anticancer drug cis-diamminedichloroplatinum(II) (cis-DDP) and DNA were studied in buccal epithelial and urinary cells from ten cancer patients who received cis-DDP-based therapy. Buccal cells were collected 1 h before and 1–2 h after i.v. infusions with cis-DDP. The interaction products were visualized in an immunocytochemical peroxidase assay, using an antiserum against cis-DDP-modified calf thymus DNA. The nuclear staining density was measured by microdensitometry. Nuclear staining densities in buccal cells after infusions of ≥20 mg/m² cis-DDP were always higher than pretreatment values. Repeated sampling from individual patients treated for 2–5 consecutive days with daily doses of 20–70 mg/m² cis-DDP indicated that cis-DDP-DNA binding in buccal cells increased in proportion to the cumulative total dose of cis-DDP. The variation in dose-density response between patients was 17%. Apparent adduct loss in buccal cells from four patients, as measured 8–17 days after the last infusion, amounted to 67–86%. Platinum-induced DNA modifications could also be detected in buccal cells from two cis-diammine(1,1-cyclobutanedicarboxylato)platinum(II)-treated patients. In vitro experiments with human buccal cells and lymphocytes indicated linear relationships between DNA modification and either cis-DDP concentration or incubation time. Nuclear staining densities in pretreatment buccal cells from ten cancer patients treated in vitro with 33 µm cis-DDP for 1 h revealed that interpatient variation in in vitro DNA modification by cis-DDP was low. No quantitative correlation was found between in situ and in vitro DNA modification.