Figure 1.

c-Myc downregulation differently affects apoptosis according to the drug mechanism of action. (A) Cytofluorimetric dot plot analysis of the annexin V-FITC versus PI staining assay performed on adherent cells of MN2 control clone and MAS69 c-Myc low-expressing transfectants from 0 to 96 hours following the end of the treatments with the IC₅₀ doses of CDDP, l-PAM, ADR, or CPT. (B) Percentage of annexin V⁺/PI^- and annexin V⁺/PI⁺ adherent cells evaluated in the drug-treated M14 and MN2 control cells (white bars) and in the drug-treated MAS51, MAS53, and MAS69 c-Myc transfectants (gray bars) from 0 to 96 hours after the end of the treatments with the IC₅₀ doses of CDDP, l-PAM, ADR, or CPT. Values of the untreated control cells and c-Myc transfectants are always below 10%; thus, they have not been included in the histograms. Statistical analysis: P values for the PI^- cells are < .05 at 0 to 24 hours, < .01 at 48 to 72 hours, and < .001 at 96 hours after exposure to CDDP and l-PAM for all the three c-Myc antisense transfectants when compared to both control cells, whereas P values are always < .05 for PI⁺ cells at all the reported times following treatment with both alkylating agents.