Abstract
Primary and acquired resistance to anticancer antibody immunotherapies presents significant clinical challenges. Here, we demonstrate that proteolytic inactivation of cancer-targeting antibodies is an unappreciated contributor to cancer immune evasion, and the finding presents novel opportunities for therapeutic intervention. A single peptide bond cleavage in the IgG1 hinge impairs cancer cell killing due to structural derangement of the Fc region. Hinge-cleaved trastuzumab gradually accumulated on the surfaces of HER2-expressing cancer cell lines in vitro, and was greatly accelerated when the cells were engineered to express the potent bacterial IgG-degrading proteinase (IdeS). Similar to cancer-related matrix metalloproteinases (MMP), IdeS exposes a hinge neoepitope that we have developed an antibody, mAb2095-2, to specifically target the epitope. In in vitro studies, mAb2095-2 restored the lost antibody-dependent cell-mediated cytotoxicity functionality of cell-bound single-cleaved trastuzumab (scIgG-T). In vivo, mAb2095-2 rescued the impaired Fc-dependent tumor-suppressive activity of scIgG-T in a xenograft tumor model and restored the recruitment of immune effector cells into the tumor microenvironment. More importantly, an Fc-engineered proteinase-resistant version of mAb2095-2 rescued trastuzumab antitumor efficacy in a mouse tumor model with human cancer cells secreting IdeS, whereas trastuzumab alone showed significantly reduced antitumor activity in the same model. Consistently, an Fc-engineered proteinase-resistant version of trastuzumab also greatly improved antitumor efficacy in the xenograft tumor model. Taken together, these findings point to a novel cancer therapeutic strategy to rescue proteolytic damage of antibody effector function by an Fc-engineered mAb against the hinge neoepitope and to overcome cancer evasion of antibody immunity.
Highlights
Antibodies are becoming a major drug modality for the treatment of many human diseases, including cancer [1,2,3]
To test whether matrix metalloproteinases (MMP) expressed by cancer cells can mediate antibody single hinge cleavage, we examined the cleavage of the trastuzumab hinge using a panel of cancer cell lines with low or high HER2 expression
Cancer cells were cultured in the presence of trastuzumab for 24 hours; trastuzumab was enriched by Protein A bead adsorption from the culture media and cell lysate, respectively; and single hinge cleavage of trastuzumab was measured by Western blotting
Summary
Antibodies are becoming a major drug modality for the treatment of many human diseases, including cancer [1,2,3]. Development of resistance to antibody therapies is widespread, and an understanding of the resistance mechanisms is a topic of great interest and clinical urgency [4,5,6,7]. In the case of breast cancer, it is well established that the humanized IgG1 antibody trastuzumab can inhibit tumor growth by binding via its variable. Note: Supplementary data for this article are available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/). Current address for R.J. Brezski: Antibody Engineering, Genentech, One DNA Way, South San Francisco, CA.
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