Figure 14.

Bystander effects between CAP-treated and untreated tumor cells: a process controlled by singlet oxygen (¹O₂). (A) MKN-45 tumor cells were treated with CAP for 1 min, followed by 25 min incubation and a washing step (open circle), or histidine (“HIS”, 2 mM) (closed square) or FeTPPS (25 µM) (closed cross) was present during CAP treatment and subsequent incubation. After washing (W), the pretreated cells were mixed with untreated tumor cells at increasing percentages. In parallel, tumor cells pretreated with CAP, subsequent incubation and washing were added to untreated tumor cells and histidine (open square) or FeTPPS (open cross) were added. The assays were cultivated for 4.5 h. (B) MKN-45 cells in the presence of AEBSF (100 µM) (open circles) or AEBSF plus histidine (closed circles) were pretreated with CAP for 1 min, followed by 25 min incubation in the same medium and a subsequent washing step. The cells were then added to untreated tumor cells at increasing concentrations and cultivated for 5 h. Alternatively, tumor cells, pretreated with CAP + 25 min incubation in the presence of AEBSF were washed and then further incubated for 25 min (open triangle, dashed line), before they were washed again and added to untreated cells. In parallel, analogous assays received histidine during the second incubation step (closed triangles, dashed line). Apoptosis induction was determined after 5 h. (C) Tumor cells were treated with CAP for 1 min in the presence of AEBSF and FeTPPS. Immediately after the treatment, the cells were washed, resuspended in fresh medium and added to untreated tumor cells. Apoptosis induction was determined after 6 h (open squares) or 7 h (open squares, dashed line). In parallel, CAP treatment for 1 min was performed in the presence of histidine, in addition to AEBSF and FeTPPS (closed squares) and the assays were proceded as described above. In parallel assays, cells were treated with CAP for 1 min in the presence of AEBSF and FeTPPS, and were then immediately washed and respuspended in fresh medium. They were further incubated for 25 min either in the absence of inhibitors (open triangle, dashed line) or in the presence of histidine (closed triangle, dashed line). The cells were washed and added to untreated cells. Apoptosis induction was determined after 6 h.