Tumoricidal activity of antiseptics with assessment of cell viability in mice with severe combined immunodeficiency

Previously, we have assessed the efficacy of different cytotoxic agents on the viability of SW620 human colonic carcinoma cells in vitro. In this study, we have investigated the tumoricidal efficacy of some antiseptic agents on SW620 human colonic carcinoma cells which were subsequently inoculated into severe combined immunodeficient (SCID) mice. An inoculum of 5 x 10(6) cells suspended in 200 mu l buffer solution was found to be the minimum number of cells needed to result in tumour growth within 8 weeks after subcutaneous injection into SCID mice. The integrity of the cells was assessed in vitro with the trypan blue exclusion test after 30 min incubation in distilled water (DW), chloramine 0.5 % in DW and polyvinyl pyrrolidone iodine (PVP-I) 0.01, 0.05, 0.1 and 5 % in DW. DW and PVP-I 0.01 % were not tumoricidal, neither in vitro nor in vivo. In contrast, PVP-I 5 % and chloramine 0.5 % 'killed' all or almost all tumour cells in vitro and prevented their growth in vivo. PVP-I 0.05 and 0.1 % were less effective in vitro than 5 %, but could prevent in vivo proliferation unless an adjustment of the residual number of viable tumour cells was performed. These data indicate the importance of the amount of the tumour inoculum and hence the need to use a maximally effective 'killing' agent.