The anti-emetic agent metoclopramide blocked CD93 signaling in cell culture and delayed leukemia development in mice, according to data from a preclinical study published in Cell Reports. The results indicate that CD93 signaling, which is an important regulator of self-renewal and proliferation of murine and human leukemia stem cells (LSCs), could be a potential therapeutic target for the elimination of LSCs in chronic myeloid leukemia (CML).
To characterize the function of CD93 in CML, the researchers first demonstrated that all subsets of LSCs expressed CD93 while more differentiated leukemia granulocytes did not. Though CD93 was shown to encourage self-renewal and proliferation of murine and human LSCs, it notably had no such effect on hematopoietic stem cells.
In an experiment, the investigators injected mice with LSCs that were either proficient or deficient in CD93. Mice with CD93-deficient LSCs were found to incorporate bromodeoxyuridine, which is used to detect proliferating cells, at a lower rate than mice with CD93-proficient LSCs. The finding suggests that proliferation of LSCs is impaired when CD93 is absent.
Next, a drug library was used to screen for compounds that could block CD93 signaling. Among the 240 compounds evaluated in vitro, 10 blocked CD93 signaling; one of the compounds was the anti-emetic agent metoclopramide.
Mice were then treated with either vehicle or metoclopramide. Notably, metoclopramide-treated mice had delayed leukemia development and lived longer than vehicle-treated mice. Among the metoclopramide-receiving mice, most genes were downregulated in the LSCs, particularly genes that promote stem cell maintenance and myeloid differentiation, cell proliferation and survival, response to cytokine signaling, and gene expression.
In vitro exposure to metoclopramide was found to disrupt colony formation in human bone marrow CML stem/progenitor cells. A control experiment showed that metoclopramide had no effect on hematopoietic stem/progenitor cells from humans with healthy bone marrow.
The study authors reasoned that because metoclopramide is a “very well-tolerated” and “cheap” anti-emetic drug, its LSC-eradicating activity in patients with CML can be “directly tested” in clinical drug repurposing studies.
Riether C, Radpour B, Kallen NM, et al. Metoclopramide treatment blocks CD93-signaling-mediated self-renewal of chronic myeloid leukemia stem cells. Cell Rep. 2021;34(4):108663. doi:10.1016/j.celrep.2020.108663