Figure 3 Cetuximab significantly enhances cytolytic activity and ADCC is negatively affected by inhibition of activating receptor-ligand interactions. Ex-vivo expanded cells PRN1371 clinical trial from Stattic cancer patient 1 were evaluated for their ability to mediate ADCC against autologous (patient 1) and allogeneic (TU-167 and H-358) EGFR expressing lung cancer cells. (A) Cytolytic activity of ex-vivo expanded cells was enhanced in the presence of Cetuximab (10 μg/ml, black bar) but not in the presence of control human IgG1 (10 μg/ml; dotted
bar) or media alone (white bar). The mean percentage cytotoxicity is shown from triplicate wells from one representative experiment. Error bars represent the SD. Experiment shown represents one of two individual experiments. (B) The addition of blocking antibodies (10 μg/ml) against DNAM-1, NKp46, NKp44 and NKp30 (= all) significantly reduced (P = 0.0176) Cetuximab-mediated ADCC. Statistical analysis is based on three experiments performed. Error bars represent the SD. * P < 0.05. HuIgG1 indicates human IgG1, Ctx; Cetuximab and moIgG1; mouse IgG1. Importantly, the expression of activating receptors on the ex-vivo expanded NK cells positively affected overall cytotoxic
activity (Figure 3B) since blocking all four activating receptors on the NK cell surface decreased autologous AZD1390 cytotoxicity if compared with control mAb (P = 0.0176 and P = 0.1019, old respectively). These data suggest that the combined strategy of adoptively transferred ex-vivo expanded autologous NK cells with infusion of an mAb that is used for cancer immunotherapy may provide clinical benefit for the treatment of select human solid tumors. To extend these observations, we are attempting to establish cell lines from other solid tumors where PBMC would be available to test NK expansion and direct cytotoxicity and ADCC capability. NK cells are efficiently expanded from lymphocyte-enriched cell fractions obtained from PBMC by counter current elutriation A GMP compliant system has successfully been established for the enrichment of monocytes
from PBMC using an Elutra cell separator. In this closed system, PBMC are fractionated by centrifugal elutriation and five cell fractions are obtained. In general, these fractions consist of platelets (fraction 1), erythrocytes mixed with lymphocytes (fraction 2), lymphocytes (fraction 3), lymphocytes mixed with monocytes (fraction 4) and mainly monocytes (fraction 5) as demonstrated in Figure 4 (n = 11). Current clinical cellular therapy protocols use monocytes obtained from elutriated fraction 5 to generate dendritic cells for cancer immunotherapy while the cells from fractions 2, 3 and 4 are usually “”archived”" in liquid nitrogen. As a means to facilitate clinical translation, we explored the possibility of these GMP compliant cell fractions to serve in future NK cell-based immunotherapy studies.