Abstract
Glycans found on the ErbB family of receptors (HER1, HER2, and HER3) represent promising targets for cancer treatment. Characterization and full quantification of the bivalent kinetic interactions of therapeutic antibodies against the ErbB family of receptors directly in their native cancer cellular environment represent a unique strategy to help overcome cancer drug resistance and to the development of more effective therapeutic drugs. In this study, surface plasmon resonance microscopy (SPRM) was implemented in a unique and innovative manner to quantify the bivalent kinetic interactions of monoclonal antibodies targeting HER1 (EFGR), HER2 and HER3 directly on whole BXPC3 pancreatic cancer cells under a glycosylated (native) and deglycosylated cellular environment. Results revealed in unprecedented detail that both the single-arm affinity and double-arm stronger avidity modes of binding interaction could be observed. For bivalent Cetuximab (anti-HER1) KDs of 151 nM and 4.6 nM were observed, for bivalent Herceptin (anti-HER2) KDs of 2 nM and 0.1 nM were observed, and for bivalent anti-HER3 KDs of 13 nM and 1.3 nM were observed. However, upon enzymatic N-deglycosylation of BXPC3 cells, HER1 and HER3 demonstrated significant increase in affinity of 1000-fold and 21-fold, respectively. In contrast, HER2 kinetic interactions were negligibly influenced by cellular N-deglycosylation of BXPC3 cells. This study highlights for the first time SPRM's unique ability to characterize the bivalent heterogeneous kinetic interactions of monoclonal antibodies with ErbB receptors on whole cancer cells, and to quantify the shielding influence of pancreatic cancer cell surface N-glycosylation on these interactions.