We performed a preclinical validation using a model of CD33<sup>+</sup> AML, and generated iC9 CAR T-cells co-expressing a CAR targeting the AML-associated antigen CD33 and a selectable marker (ΔCD19).ΔCD19 selected (sel.) iC9-CAR.CD33 T-cells were effective in controlling leukemia growth in vitro, and could be partially eliminated (76%) using a chemical inducer of dimerization that activates iC9.
Using a human AML cell line (HL-60), we modeled a postremission marrow with minimal residual disease and showed that the transplantation of CD33-ablated HSPCs with CD33-targeted immunotherapy leads to leukemia clearance, without myelosuppression, as demonstrated by the engraftment and recovery of multilineage descendants of CD33-ablated HSPCs.
CD33 (siglec-3), a well-known target in leukemia therapy, is an inhibitory sialoadhesin expressed in human leukocytes of the myeloid lineage and some lymphoid subsets, including NK cells.
BACKGROUND Leukemia stem cells (LSC) are involved in the incidence, drug resistance, and relapse of leukemia while LSC-related antigen CD33, CD96, and DAPK expression in AML and its prognosis is still unclear.
Dual-specific targeting and elimination were investigated against the B-cell precursor leukemia cell line BV-173 and patient blasts, which were positive for myeloid marker CD33 and B lymphoid marker CD19 exclusively presented on biphenotypic B/myeloid leukemia's.
Challenging ΔCD19 selected inducible Caspase9-CAR.CD33 T-cells with programmed-death-ligand-1 enriched leukemia blasts resulted in significant killing like observed for the programmed-death-ligand-1 negative leukemic blasts fraction.
Furthermore, the CD33-redirected T cells were effective in vivo, preventing the development of leukemia after prophylactic administration and delaying the progression of established disease in mice.
Ectopic expression of SOX7 in K562 and THP-1 cells, as well as primary CD33(+)CD34(+) AML cells, abrogated leukemia engraftment in xenogeneic transplantation.
In addition, immunophenotypic analysis revealed the coexpression of the CD33 and CD7 antigens on common ALL blasts, in accordance with other reported cases that displayed a predominant biphenotypic leukemia profile.
The patient was an adult male diagnosed with ALL(L2), Cell marker studies showed positivity for CD3, CD7, CD13 and CD33, so the phenotypic diagnosis was determined to be biphenotypic leukemia.
NALM-29 cells display biphenotypic characteristics: expression of the intracellular enzyme myeloperoxidase at the mRNA and protein level and cell surface positivity for CD19, CD10, CD13, CD33 and HLA-DR. NALM-29 fulfills EGIL criteria as B-cell precursor (BCP) leukemia B-II type.
Our results suggest that the leukemia with inv(3)(q21q26) represents a new cytogenetic-clinicopathologic subtype, characterized by 1) abnormal megakaryopoiesis and multiple hematopoietic lineage involvement; 2) an antecedent MDS; 3) poor response to conventional chemotherapy; and 4) expression of CD7, CD34, CD38, HLA-DR, CD13, and CD33 antigens.