CD44 ligation with A3D8 antibody induces apoptosis in acute myeloid leukemia cells through binding to CD44s and clustering lipid rafts

Abstract

CD44 is a cell surface antigen expressed on acute myeloid leukemia cells and is used as a marker to isolate leukemia stem cells. CD44 ligation with the antibody A3D8 has been found to induce apoptosis in human acute promyelocytic leukemia (APL) cells via activation of caspase-8. The mechanism of A3D8-induced caspase-8 activation was studied in APL NB4 cells. A3D8 induces lipid raft clustering which causes Fas aggregation as determined with a confocal microscope. A3D8-induced apoptosis is abrogated by the lipid raft disrupting agent methyl-β-cyclodextrin and the caspase-8 inhibitor Z-IETD-fmk. Western blot analysis reveals that A3D8 binds to the standard form of CD44 (CD44s). HL-60 cells without detectable CD44s protein are not responsive to A3D8-induced apoptosis. SKNO-1 cells containing higher level of CD44s protein are more sensitive to A3D8-induced apoptosis than NB4 cells. These results indicate that A3D8 induces apoptosis in leukemia cells through caspase-8 activation by binding to CD44s protein and inducing lipid raft clustering.

Keywords: :

• antibody
• apoptosis
• CD44
• lipid rafts
• myeloid leukemia

Disclosure of Potential Conflicts of Interest

The authors declare that there is no conflict of interest to disclose.

Acknowledgments

This work was supported by The Samuel Waxman Cancer Research Foundation. Critical reading of the manuscript by William Scher is appreciated.

Contributors: H.Q. designed and performed the research, analyzed data and wrote the paper; Y.J. designed the research, analyzed the data and wrote the paper; P.L. provided the agents and analyzed data; S.W. analyzed the data and wrote the paper; L.X. performed research.