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Sensitivity of myeloid leukemia cells to calcium influx blockade: application to bone marrow purging
Jonathan Soboloff1, Yicheng Zhang, Mark Minden
1AIDRC, University Health Network and the Department of Immunology, University of Toronto, Toronto, Ontario, Canada.
Objective:
The aim of this study was to assess the potential of store-operated Ca(2+) channel (SOC) antagonists as purging agents for leukemia cells.
Materials And Methods:
Clonogenic, limiting dilution, and nuclear condensation assays were used to evaluate SOC antagonist efficacy. SOC activity and endoplasmic reticulum Ca(2+) content were measured by flow cytometry. Murine bone marrow transplantation was used to determine purging efficacy and effects on hemopoietic reconstitution.
Results:
Econazole (Ec) and ketotifen (Ke) were variably effective against human and murine leukemia cell lines after 24 hours of incubation. However, a 2-hour serum and bovine serum albumin-free treatment protocol with Ec was found to maximize differential sensitivity between leukemic cells and normal hemopoietic progenitors. Primary acute myelogenous leukemia blast cell viability was reduced 4.2 to 5.1 logs by 2-hour Ec treatment as measured by limiting dilution. An inverse relationship between endoplasmic reticulum Ca(2+) content and Ke sensitivity in leukemia and untransformed cells was observed. Nuclear condensation, an index of apoptosis, which occurred after 24-hour treatments with either Ec or Ke, was not observed after 2-hour serum- and bovine serum albumin-free Ec exposures; however, condensed nuclei were observed after an additional 10-hour incubation in growth medium without drug. Using bone marrow deliberately contaminated with 1% P815 cells, we showed that highly effective in vitro purging can be accomplished using Ec with no adverse effects on bone marrow reconstitution in mice.
Conclusions:
These studies suggest that SOC antagonists have potential as purging agents for residual leukemia cells present in bone marrow in the context of high-dose chemotherapy and autologous transplantation for leukemia.
Insights
Store-operated Ca(2+) channel (SOC) antagonists, like econazole, show promise for purging leukemia cells from bone marrow. A short treatment effectively reduced leukemia cells without harming healthy stem cells, suggesting potential for transplantation therapies.
Area of Science:
- Hematology
- Oncology
- Pharmacology
Background:
- Residual leukemia cells pose a significant challenge in leukemia treatment.
- High-dose chemotherapy and autologous stem cell transplantation are standard leukemia therapies.
- Effective purging of leukemia cells from autologous bone marrow grafts is crucial.
Purpose of the Study:
- To evaluate store-operated calcium channel (SOC) antagonists as potential agents for purging leukemia cells.
- To assess the efficacy and safety of SOC antagonists in eliminating leukemia cells from bone marrow grafts.
Main Methods:
- Clonogenic, limiting dilution, and nuclear condensation assays were employed.
- SOC activity and calcium levels were measured using flow cytometry.
- Murine bone marrow transplantation models were used to assess purging and reconstitution effects.
Main Results:
- Econazole (Ec) and ketotifen (Ke) demonstrated variable efficacy against leukemia cell lines.
- A 2-hour serum- and albumin-free protocol with Ec maximized differential sensitivity, reducing primary AML blast viability by 4.2–5.1 logs.
- Ec purging showed no adverse effects on bone marrow reconstitution in mice.
Conclusions:
- SOC antagonists, particularly econazole, show potential as effective purging agents for residual leukemia cells.
- This approach could be beneficial in the context of high-dose chemotherapy and autologous transplantation for leukemia.
- Further investigation into SOC antagonists for leukemia cell purging is warranted.
