Targeting CD137 enhances the efficacy of cetuximab
Holbrook E. Kohrt, … , John Sunwoo, Ronald Levy
Holbrook E. Kohrt, … , John Sunwoo, Ronald Levy
Published May 16, 2014
Citation Information: J Clin Invest. 2014;124(6):2668-2682. https://doi.org/10.1172/JCI73014.
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Research Article

Targeting CD137 enhances the efficacy of cetuximab

Abstract

Treatment with cetuximab, an EGFR-targeting IgG1 mAb, results in beneficial, yet limited, clinical improvement for patients with head and neck (HN) cancer as well as colorectal cancer (CRC) patients with WT KRAS tumors. Antibody-dependent cell-mediated cytotoxicity (ADCC) by NK cells contributes to the efficacy of cetuximab. The costimulatory molecule CD137 (4-1BB) is expressed following NK and memory T cell activation. We found that isolated human NK cells substantially increased expression of CD137 when exposed to cetuximab-coated, EGFR-expressing HN and CRC cell lines. Furthermore, activation of CD137 with an agonistic mAb enhanced NK cell degranulation and cytotoxicity. In multiple murine xenograft models, including EGFR-expressing cancer cells, HN cells, and KRAS-WT and KRAS-mutant CRC, combined cetuximab and anti-CD137 mAb administration was synergistic and led to complete tumor resolution and prolonged survival, which was dependent on the presence of NK cells. In patients receiving cetuximab, the level of CD137 on circulating and intratumoral NK cells was dependent on postcetuximab time and host FcyRIIIa polymorphism. Interestingly, the increase in CD137-expressing NK cells directly correlated to an increase in EGFR-specific CD8+ T cells. These results support development of a sequential antibody approach against EGFR-expressing malignancies that first targets the tumor and then the host immune system.

Authors

Holbrook E. Kohrt, A. Dimitrios Colevas, Roch Houot, Kipp Weiskopf, Matthew J. Goldstein, Peder Lund, Antonia Mueller, Idit Sagiv-Barfi, Aurelien Marabelle, Ruth Lira, Emily Troutner, Lori Richards, Amanda Rajapaska, Jonathan Hebb, Cariad Chester, Erin Waller, Anton Ostashko, Wen-Kai Weng, Lieping Chen, Debra Czerwinski, Yang-Xin Fu, John Sunwoo, Ronald Levy

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Figure 2

Anti-CD137 agonistic mAb increases cetuximab-mediated NK cell cytotoxicity on tumor cells.

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Anti-CD137 agonistic mAb increases cetuximab-mediated NK cell cytotoxici...
To evaluate NK cell function, purified NK cells were isolated from 3 independent, healthy donor PBMCs and cultured for 24 hours together with cetuximab (10 μg/ml) and irradiated (50 Gy) EGFR-expressing cancer cells (PC1) at a ratio of 1:1. After 24 hours, NK cells were isolated by negative selection and assessed for purity (>90% purity as defined by CD3–CD56+ flow cytometry) and activation (>50% expression of CD137). EGFR-expressing cancer cell lines including SCC6 (A and D), PC1 (B and E), and SCC4 (C and F) were cultured for 18 hours with preactivated, purified NK cells in medium alone or with anti-CD137 mAb (BMS-663513, 10 μg/ml) alone, cetuximab (10 μg/ml) alone, or cetuximab plus anti-CD137 mAbs (both at 10 μg/ml). Cells were washed and incubated with annexin V and 7-AAD to determine percentage of apoptotic tumor cells by annexin V and 7-AAD staining. Chromium-labeled EGFR-expressing cancer cell lines were cultured for 4 hours with preactivated, purified NK cells in medium alone or with anti-CD137 mAb (BMS-663513, 10 μg/ml) alone, cetuximab (10 μg/ml) alone, or cetuximab plus anti-CD137 mAbs. Shown is percentage lysis of target cells by chromium release at varying effector (activated NK cells)/target cell ratios cultured with medium alone (circles), anti-CD137 (upside-down triangle), cetuximab (triangle), or cetuximab and anti-CD137 (square) antibodies. *P = 0.002, SCC6 (A); *P = 0.007, PC1 (B); *P = 0.00 7, SCC4 (C); *P = 0.021, SCC6 (D); *P = 0.011, PC1 (E); *P = 0.049, SCC4 (F).