FIG. 1. Structures of Spym (2-mercaptopyrimidine), Pt(III)-Spym, and cis-DDP.

FIG. 2. Time– and dose–response effect of Pt-Spym and cis-DDP on the survival of HeLa and HL-60 cells. Cells were cultured with different drug concentrations for 16, 24, and 48 hr, and cell survival was determined by the MTT method. (A) HL-60 cells and (B) HeLa cells incubated with cis-DDP; (C) HL-60 cells and (D) HeLa cells incubated with Pt-Spym.

FIG. 3. Morphological changes in control untreated HeLa cells after 16 hr (A) or 24 hr (B) or in cells treated with 2 × ₅₀ of Pt-Spym for 16 (C) or 24 hr (D) and photographed under a phase-contrast microscopy at a magnification of ×200.

FIG. 4. Agarose gel electrophoresis (1.5%) of genomic DNA extracted from control and Pt-Spym treated for 24 hr with 2 × ₅₀ of drug. Human fibroblasts (A), control and Pt-Spym-treated (2 × ₅₀) HeLa ovarian tumor cells (B), and control and Pt-Spym-treated (2 × ₅₀) leukemic HL-60 cells (C).

FIG. 5. Morphological changes in nuclei of HeLa cells after 24 hr of incubation with Pt-Spym. Cultures of HeLa cells were treated with 2 × ₅₀ concentrations of Pt-Spym and photographed under a Zeiss microscope with fluorescence attachment at a magnification of ×660. (A) Control cells; (B) Pt-Spym-treated cells.

FIG. 6. Percentage of apoptotic HeLa cells after Pt-Spym treatment (2 × ₅₀) as calculated from the amount of fragmented and integer DNA versus the incubation time. Error bars indicate standard deviations.

FIG. 7. (Upper panel). Levels of expression of p53 protein in CH1, CH1cisR, and HeLa cells after treatment with 2 × ₅₀ of the Pt-Spym complex and cis-DDP. Lane 1, control untreated CH1 cells (1.0 μg of p53); lane 2, CH1 cells treated with Pt-Spym (0.8 μg of p53); lane 3, CH1 cells treated with cis-DDP (0.01 μg of p53); lane 4, control CH1cisR cells (1 μg of p53); lane 5, CH1cisR cells treated with Pt-Spym (0.7 μg of p53); lane 6, CH1cisR cells treated with cis-DDP (0.01 μg of p53); lane 7, control HeLa (0.5 μg of p53); lane 8, HeLa cells treated with Pt-Spym (0.4 μg of p53); and lane 9, HeLa cells treated with cis-DDP (absence of p53). (Bottom panel). Control levels of α-actin in treated and non-treated cells as in (A).

TABLE 1. ₅₀ mean values obtained for cis-DDP, Pt-Spym, and Spym against HeLa, CH1, CH1cisR, and HL-60 tumor cell lines and against human fibroblasts (HF) after 24 hr of incubation at 37° with the drugs^legend