Combination of NK Cells and Cetuximab to Enhance Anti-Tumor Responses in RAS Mutant Metastatic Colorectal Cancer.

John Pradeep Veluchamy,Tanja D De Gruijl,Hans J Van Der Vliet,Jan Spanholtz,Marleen Tordoir,Victor L Thijssen,Henk M W Verheul,Daniëlle A M Heideman,Fabrizio Mattei

doi:10.1371/journal.pone.0157830

Abstract

The ability of Natural Killer (NK) cells to kill tumor targets has been extensively studied in various hematological malignancies. However, NK cell therapy directed against solid tumors is still in early development. Epidermal Growth Factor Receptor (EGFR) targeted therapies using monoclonal antibodies (mAbs) such as cetuximab and panitumumab are widely used for the treatment of metastatic colorectal cancer (mCRC). Still, the clinical efficacy of this treatment is hampered by mutations in RAS gene, allowing tumors to escape from anti-EGFR mAb therapy. It is well established that NK cells kill tumor cells by natural cytotoxicity and can in addition be activated upon binding of IgG1 mAbs through Fc receptors (CD16/FcγRIIIa) on their surface, thereby mediating antibody dependent cellular cytotoxicity (ADCC). In the current study, activated Peripheral Blood NK cells (PBNK) were combined with anti-EGFR mAbs to study their effect on the killing of EGFR+/- cancer cell lines, including those with RAS mutations. In vitro cytotoxicity experiments using colon cancer primary tumors and cell lines COLO320, Caco-2, SW620, SW480 and HT-29, demonstrated that PBNK cells are cytotoxic for a range of tumor cells, regardless of EGFR, RAS or BRAF status and at low E:T ratios. Cetuximab enhanced the cytotoxic activity of NK cells on EGFR+ tumor cells (either RASwt, RASmut or BRAFmut) in a CD16 dependent manner, whereas it could not increase the killing of EGFR- COLO320. Our study provides a rationale to strengthen NK cell immunotherapy through a combination with cetuximab for RAS and BRAF mutant mCRC patients.

Highlights

Epidermal Growth Factor Receptor (EGFR) is expressed on cell surfaces in normal tissues and binding to its ligands activates two important pathways, the RAS-RAF-MAPK and PI3K-PTEN-AKT pathway, which both control cell proliferation, survival and motility [1]
More potent Natural Killer (NK) effector cell activation and antibody dependent cellular cytotoxicity (ADCC) effected by cetuximab than by panitumumab To establish which of the anti-EGFR monoclonal antibodies (mAbs), cetuximab or panitumumab, exerted higher functionality with respect to EGFR recognition and cytotoxicity, both were tested on strongly EGFR positive (EGFR+++) A431 cells
The concentrations required to induce 50% of maximal cytotoxicity (EC50 value) of EGFR+++targets were found to be 5μg/ml for cetuximab (31 ± 2%) and 100μg/ ml for panitumumab (36 ± 1%) respectively (Fig 1C). Based on these findings concentrations of 5μg/ml of cetuximab and 100μg/ml of panitumumab were used in all subsequent experiments to assess their ADCC efficacy when combined with NK cells

Summary

Introduction

Epidermal Growth Factor Receptor (EGFR) is expressed on cell surfaces in normal tissues and binding to its ligands activates two important pathways, the RAS-RAF-MAPK and PI3K-PTEN-AKT pathway, which both control cell proliferation, survival and motility [1]. The specific roles of these authors are articulated in the 'author contribution' section

Objectives

Methods

Results

Conclusion