Most anti-cancer drugs target mitosis and induce apoptosis in cancerous cells. In the immune system, proliferation and apoptosis of lymphocytes are indeed essential modulating elements.
In this study, we have investigated the effect of vincristine on normal resting and normal proliferating lymphocytes comparing with cancerous cells.
Resting and proliferating splenocytes from mice and BCL1 (mouse lymphoma cell line) were cultured with different concentrations of vincristine for 48 hours, and cell lysates were prepared. The activity of caspases 3, 8, and 9 in cell lysates was measured using specific chromogenic substrates DEVD-pNA for caspase 3, IETD-pNA for caspase 8, and LEHD-pNA for caspase 9, the activity calculated as µmol/min/mg protein.
In the BCL1 cell line, the activity of both caspases 8 and 9 and caspase 3 increased at the presence of vincristine (5 µg/mL). In resting splenocytes, however, only a mild increase in caspase 9 activity was observed without any change in the activity of caspases 8 or 3. In the same situation, the activity of caspase 3 and 9 (but not caspase 8) elevated in proliferating cells exposed to vincristine. Nearly similar results were obtained with higher concentrations of vincristine (up 20 µg/mL).
The results suggesting that vincristine may induce internal pathways of apoptosis in normal and cancerous cells while extrinsic pathway was induced in cancerous cells. On the other hand, the effects are highly dependent on the activation status of normal cells, and affirms that responding immune cells should be more seriously noticed when side effects of anticancer drugs are estimated