IL-21 Enhances Natural Killer Cell Response to Cetuximab-Coated Pancreatic Tumor Cells.

Purpose: Alternative strategies to EGFR blockage by mAbs is necessary in order to improve the efficacy of therapy in patients with locally advanced or metastatic pancreatic cancer. One such strategy includes the use of NK cells to clear cetuximab-coated tumor cells, as need for novel therapeutic approaches to enhance the efficacy of cetuximab is evident. We show that IL-21 enhances NK cell-mediated effector functions against cetuximab-coated pancreatic tumor cells irrespective of KRAS mutation status. Experimental Design: NK cells from normal donors or donors with pancreatic cancer were used to assess ADCC, IFN-γ release, and T cell chemotaxis towards human pancreatic cancer cell lines. The in vivo efficacy of IL-21 in combination with cetuximab was evaluated in a subcutaneous and intraperitoneal model of pancreatic cancer. Results: NK cell lysis of cetuximab-coated wild-type and mutant KRAS pancreatic cancer cell lines was significantly higher following NK cell IL-21 treatment. In response to cetuximab-coated pancreatic tumor cells, IL-21 treated NK cells secreted significantly higher levels of IFN-γ and chemokines, increased chemotaxis of T cells, and enhanced NK cell signal transduction via activation of ERK and STAT1. Treatment of mice bearing subcutaneous or intraperitoneal EGFR-positive pancreatic tumor xenografts with mIL-21 and cetuximab led to significant inhibition of tumor growth, a result further enhanced by the addition of gemcitabine. Conclusions: These results suggest that cetuximab treatment in combination with IL-21 adjuvant therapy in patients with EGFR-positive pancreatic cancer results in significant NK cell activation, irrespective of KRAS mutation status, and may be a potential therapeutic strategy.