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Activation-induced apoptosis of peripheral lymphocytes treated with 7-hydroxystaurosporine, UCN-01
H Fukumoto1, T Tamura, Y Kamiya
1Pharmacology Division, National Cancer Center Research Institute, Tokyo, Japan.
Abstract:
7-hydroxystaurosporine (UCN-01) is a new anticancer agent which exerts an inhibitory effect on cell cycle check points and is currently under phase I clinical trials in US and Japan. Preliminary clinical data indicated that UCN-01 remained in plasma at high concentrations for long periods of time. This unavoidable high plasma drug exposure is likely to lead to hematological toxicities in patients. In the present study, cultured human peripheral blood lymphocytes (PBLs) were used to evaluate the possible hematological toxicities of UCN-01 treatment. UCN-01 induces apoptosis, and the induction of apoptosis-related surface markers were also examined to investigate the involvement of these molecules in UCN-01-induced apoptosis in PBLs. In vitro viability of PBLs was decreased by high dose of UCN-01 (25 microM, 3-day exposure). This effect of UCN-01 was significantly suppressed by the presence of human serum, suggesting that some specific inhibitory factor(s) in human serum may antagonize the lympholytic effect of UCN-01. The percentage of annexin V-positive PI-negative cells increased with exposure to UCN-01 in a time- and dose-dependent manner; by up to 30.3% after exposure to 25 microM UCN-01 for 3 days. At the same time, the expression of both interleukin-2 receptor (IL-2R, CD25) and Fas (CD95), analyzed by flow cytometry, was induced. Con A-stimulated PBLs were more sensitive to UCN-01-induced apoptosis than non-stimulated lymphocytes and UCN-01 increased the sFas-L released into culture medium from con A-stimulated PBLs. Therefore, lymphocyte depletion mediated by activation-induced apoptosis is likely to occur in patients treated with UCN-01 at high doses.
Insights
7-hydroxystaurosporine (UCN-01), an anticancer drug, can cause lymphocyte depletion by inducing apoptosis. Human serum may protect against UCN-01
Area of Science:
- Pharmacology
- Immunology
- Oncology
Background:
- 7-hydroxystaurosporine (UCN-01) is an investigational anticancer agent targeting cell cycle checkpoints.
- Phase I clinical trials reveal UCN-01's prolonged high plasma concentrations, raising concerns for hematological toxicities.
- Potential lymphocyte toxicity necessitates evaluating UCN-01's effects on human peripheral blood lymphocytes (PBLs).
Purpose of the Study:
- To assess the potential hematological toxicities of UCN-01 on human PBLs.
- To investigate the induction of apoptosis and related surface markers by UCN-01 in PBLs.
- To explore the role of human serum in modulating UCN-01's lympholytic effects.
Main Methods:
- Cultured human PBLs were exposed to varying doses and durations of UCN-01.
- In vitro PBL viability was assessed.
- Apoptosis was evaluated using Annexin V/propidium iodide staining.
- Expression of IL-2R (CD25) and Fas (CD95) was analyzed via flow cytometry.
- Supernatant soluble Fas ligand (sFas-L) was measured in Con A-stimulated PBLs.
Main Results:
- High-dose UCN-01 (25 microM, 3 days) significantly decreased PBL viability.
- The presence of human serum markedly suppressed UCN-01-induced lympholysis.
- UCN-01 exposure dose- and time-dependently increased Annexin V-positive cells, indicating apoptosis.
- UCN-01 induced the expression of IL-2R (CD25) and Fas (CD95) on PBLs.
- Concanavalin A (Con A)-stimulated PBLs were more susceptible to UCN-01-induced apoptosis and released more sFas-L.
Conclusions:
- UCN-01 induces apoptosis in human PBLs, potentially leading to lymphocyte depletion.
- Activation-induced apoptosis, particularly in stimulated lymphocytes, may contribute to UCN-01's hematological toxicity.
- Human serum contains factors that can antagonize the cytotoxic effects of UCN-01 on lymphocytes.