Expansion of allogeneic NK cells with efficient antibody-dependent cell cytotoxicity against multiple tumors

Abstract

Monoclonal antibodies (mAbs) have significantly improved the treatment of certain cancers. However, in general mAbs alone have limited therapeutic activity. One of their main mechanisms of action is to induce antibody-dependent cell-mediated cytotoxicity (ADCC), which is mediated by natural killer (NK) cells. Unfortunately, most cancer patients have severe immune dysfunctions affecting NK activity. This can be circumvented by the injection of allogeneic, expanded NK cells, which is safe. Nevertheless, despite their strong cytolytic potential against different tumors, clinical results have been poor.Methods: We combined allogeneic NK cells and mAbs to improve cancer treatment. We generated expanded NK cells (e-NK) with strong in vitro and in vivo ADCC responses against different tumors and using different therapeutic mAbs, namely rituximab, obinutuzumab, daratumumab, cetuximab and trastuzumab.Results: Remarkably, e-NK cells can be stored frozen and, after thawing, armed with mAbs. They mediate ADCC through degranulation-dependent and -independent mechanisms. Furthermore, they overcome certain anti-apoptotic mechanisms found in leukemic cells.Conclusion: We have established a new protocol for activation/expansion of NK cells with high ADCC activity. The use of mAbs in combination with e-NK cells could potentially improve cancer treatment.

Non-Genetically Improving the Natural Cytotoxicity of Natural Killer (NK) Cells

“…This is significantly longer than T cell doubling time during the initial expansion phase, which are 8 and 11 h for CD8 + and CD4 + T cells, respectively (9). Moreover, after allogeneic engraftment most clinical results failed to show significant expansion of donor NK cells (6,7,(10)(11)(12)(13). Perhaps the high renew and short lifespan account for these poor in vivo expansions because NK cells have already strongly expanded during their maturation and they are prone to "effector-like" phenotype, at least in the blood population.…”

“…But, studies in blood are valid considering that allogeneic NK cells for engraftment are obtained from peripheral blood. Moreover, in vitro stimulated NK cells normally gain a mature phenotype despite high CD56 expression (6). Therefore, the previous estimates are a reasonable proxy for the amount of time NK cells will be active after allogenic engraftment.…”

“…Fourth, naïve NK cells possess a relatively low activity compare to activated cells (6,14). This could be responsible of the low efficacy of NK cell-mediated therapies (11)(12)(13).…”

“…There are many protocols to expand and activate in vitro NK cells (6,11,13,(28)(29)(30)(31). For many clinical uses, the manufactured cells should express the FcγRIIIa, also called CD16.…”

“…Expansion was driven by Epstein-Barr virus (EBV)-transformed lymphoblastoid B cell lines as accessory cells, which induce a unique NK cell genetic reprogramming (14), generating effectors that overcome the anti-apoptotic mechanism of leukemic cells (41) and that are able to eliminate tumor cells from patients with poor prognosis (42). NK cells obtained with this protocol perform antibody-dependent cell cytotoxicity (ADCC) in vitro and in vivo with different therapeutic antibodies and against diverse target cells (6).…”