Abnormal expression of CD66a promotes proliferation and inhibits apoptosis of human leukemic B cells in vitro.

The aberrant expression of myeloid antigen CD66 on acute B-lymphoblastic leukemia (B-ALL) cells is a well-documented phenomenon. CD66a is a major subtype of the CD66 family which plays a dual role in different cancers, and the contradictory effect may depend on the isoform ratio of CD66a-4L to CD66a-4S. Although the abnormal expression of CD66a on leukemic B-cells has been reported widely, little is known about the biological function of this aberrant expression. In this study, we showed that inhibition of CD66a in human B-ALL cell lines reduced the cellular proliferative rate and increased the percentage of cellular apoptosis, and the ratio of CD66a-4L to CD66a-4S in leukemic B cells is much higher than that in granulocytes. In addition, alteration of the L:S ratio by silencing and overexpressing the L isoform in B-ALL cell lines confirmed that a high L:S ratio of CD66a in leukemic B cells promotes proliferation and inhibits FasL-induced apoptosis.