Interleukin-2 Receptor Alpha Chain, Also Called CD25, Is a Potential Target in Acute Lymphoblastic Leukemia

Background: Acute lymphoblastic leukemia (ALL) is a molecularly heterogeneous disease originating from clonal proliferation of precursor B-lineage cells. In adults, ALL diagnosis is still associated with a dismal prognosis due to the lack of specific targeted therapies. This study was designed to investigate the expression of interleukin-2 receptor alpha chain CD25 in B-ALL and its biological significance, especially following the availability of specific CD25 targeting compounds.

Methods:The expression of IL2RA (CD25 gene) was detected by flow cytometry (FC), immunohistochemistry and Western blot analysis, in 25 newly diagnosed ALL patients, both Philadelphia positive (12 patients) and Philadelphia negative (13 patients). Similarly, CD25 expression was assessed in four B-ALL commercially available cell lines. Infection with shRNA specifically directed against CD25 was used to evaluate apoptosis induction and cell cycle arrest in primary B-ALL cells established from two patients.

Results:Our data suggest that ALL, and in particular Ph-positive ALL, aberrantly expresses the interleukin-2 receptor alpha chain, CD25. Whereas normal B cells display low amounts of CD25, primary ALL cells and ALL cell lines (over)-express CD25. While the high frequency of CD25 on the surface of many different hematological tumor cells has been established and confirmed in our study, there is little investigation focusing on the significance of CD25 expression. Indeed, CD25 may be present on ALL cells and enable oncogenic signaling pathways. In such respect, we observed that CD25 silencing in primary cells promotes cell cycle arrest and apoptosis induction. While these data support the rational to target CD25, ALL cells did not appear to be in-vitro sensitive to basiliximab, an antibody able to target the Il2RA, but in-vivo investigations are needed to better assess the effects of this therapeutic approach in ALL context.

Conclusions:We concluded that CD25 expression is elevated in patients with B-ALL. Our results also demonstrate that CD25 silencing induces cell cycle arrest and apoptosis. The latter result has important implications from a therapeutic point of view. Targeting CD25 receptor with anti-CD25 antibodies or peptide mimetics could be an effective strategy for targeting leukemic cells. Additionally, high CD25 expression could be exploited for the development of CAR-T therapy