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Different sensitivity of CD30+ cell lines to Ber-H2/saporin-S6 immunotoxin
M G Battelli1, A Bolognesi, F Olivieri
1Department of Experimental Pathology, University of Bologna, Italy. mgbatt@alma.unibo.it
Abstract:
The in vitro sensitivity of cells to a Ber-H2(anti-CD30)/saporin-S6 immunotoxin has been investigated. The CD30+ cell lines, K562, L428 and L540, were used to study cell binding, uptake and degradation of the immunotoxin. K562 cells were less sensitive than L428 and L540 cells to the immunotoxin by approximately one order of magnitude. The difference in cytotoxicity correlated with the intracellular accumulation and with the ratio of degraded over total internalized Ber-H2/saporin-S6, regardless of the immunotoxin binding to the cells. After 6 h incubation, the less sensitive K562 cells (i) accumulated only one third and one tenth of the immunotoxin accumulated by the more sensitive L428 and L540 cells, respectively, and (ii) degraded two thirds of the internalized protein versus one third degraded by either L428 or L540 cells. Ammonium chloride and chloroquine reduced the cytotoxicity of the immunotoxin towards K562 but not to L540 cells. This effect correlated with the increment of immunotoxin catabolism by K562 cells in the presence of chloroquine. In conclusion, uptake alone of an immunotoxin by target cells is not sufficient to assure its efficacy which might also depend on intracellular routing. Only a cytotoxicity test may be really predictive.
Insights
Cellular sensitivity to Ber-H2(anti-CD30)/saporin-S6 immunotoxin depends on intracellular accumulation and degradation, not just binding. Cytotoxicity testing is crucial for predicting immunotoxin efficacy in cancer therapy.
Area of Science:
- Immunology
- Cell Biology
- Pharmacology
Background:
- Immunotoxins are targeted therapies designed to kill specific cells.
- Ber-H2(anti-CD30)/saporin-S6 is an immunotoxin targeting CD30+ cells.
Purpose of the Study:
- To investigate the in vitro sensitivity of CD30+ cell lines to Ber-H2(anti-CD30)/saporin-S6 immunotoxin.
- To determine factors influencing immunotoxin efficacy, including binding, uptake, and degradation.
Main Methods:
- Utilized CD30+ cell lines (K562, L428, L540) for in vitro studies.
- Assessed cell binding, intracellular accumulation, and degradation of the immunotoxin.
- Investigated the effects of ammonium chloride and chloroquine on immunotoxin cytotoxicity.
Main Results:
- K562 cells showed significantly lower sensitivity (one order of magnitude) compared to L428 and L540 cells.
- Cytotoxicity correlated with intracellular accumulation and the ratio of degraded to internalized immunotoxin.
- Ammonium chloride and chloroquine reduced cytotoxicity in K562 cells, indicating altered intracellular processing.
Conclusions:
- Immunotoxin efficacy is influenced by intracellular routing and degradation, not solely by cellular uptake.
- Cytotoxicity assays are essential for predicting the effectiveness of immunotoxins.
- Understanding intracellular processing is key to optimizing immunotoxin-based therapies.