The Migratory Activity of Anti-CD19 cTCR-Redirected CIK Cells as a Useful Property for In Vivo Targeting of B-ALL Cells.

Cytokine induced killer (CIK) cells are a population of ex-vivo expanded cells enriched in CD3⁺CD56⁺ natural killer T (NKT) cells with MHC-unrestricted cytotoxicity against several leukemia targets, except B-lineage acute lymphoblastic leukemia (B-ALL) cells. The trafficking machinery of NKT cells reflects their preferential localization in bone marrow, liver and spleen, which are also sites of B-ALL infiltration. In the present study we determined whether CIK cells maintain the original trafficking properties of NKT cells, by analyzing their pattern of expression of adhesion molecules, chemokine receptors and chemotactic activity. Moreover, we investigated the possibility to redirect the cytotoxic activity of CIK cells towards our selected target (B-ALL cells) by transduction with a retroviral vector encoding a chimeric T-cell receptor (cTCR) specific for the CD19 antigen. Similarly to freshly-isolated NKT cells, CIK cells expressed CXCR4, CCR6 and CCR7 (average expression 72%, 60% and 32% respectively), presenting chemotactic activity towards their respective ligands. The adhesion molecules CD49d and CD11a were highly expressed on >99% of CIK cells, potentially reflecting their capacity to adhere to the endothelium in bone marrow and non-lymphoid organs. To induce cytotoxicity against B-ALL cells, we transduced CIK cells with a retroviral vector containing the anti-CD19-ζ chimeric receptor and the GFP as marker gene, and analyzed their phenotypic characteristics (CD3/CD56 and chimeric receptor expression) and cytotoxic activity against REH B-ALL cell line and B-ALL cells in a ⁵¹Cr-release assay. Percentage of CD3⁺/CD56⁺ was not altered by transduction. CIK cells were efficiently transduced with the retroviral vector (average expression of GFP/chimeric receptor = 15%; n=8). Furthermore, CIK cells expressing the anti-CD19-ζ receptor showed a strong cytotoxic activity against the REH B-ALL cell line (average lysis, 59.9% at an effector:target ratio=30:1, range, 45.7%–69.5%; n=3) and against primary B-ALL blasts (average lysis, 60.2% at an effector:target ratio=30:1, range=39.7%–72.8%; n=3), that was not observed in CIK cells expressing the truncated-nonsignaling form of the receptor. In addition, the migratory capacities of the transduced CIK cells remain unchanged when compared to unmanipulated CIK cells. These findings suggest that CIK cells show a natural capacity to reach sites of B-ALL infiltration and proliferation, and can be redirected with a specific anti-CD19 cTCR, to becoming able to kill leukemic cells without affecting their migratory properties. Based on these preliminary findings we suggest that anti-CD19-modified CIK cells may be an attractive strategy for B-ALL immunotherapy.