Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) promotes EGF receptor signaling of oral squamous cell carcinoma metastasis via the complex N-glycosylation

Abstract

Aberrant protein glycosylation could be a distinct surface-marker of cancer cells that influences cancer progression and metastasis because glycosylation can regulate membrane protein folding which alters receptor activation and changes epitope exposure for antibody (Ab) recognition. Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6), a glycophosphoinositol-anchored protein, is a heavily glycosylated tumor antigen. However, the clinical significance and biological effect of CEACAM6 glycosylation has not been addressed in cancers. We recently developed an anti-CEACAM6 Ab (TMU) from an immune llama library which can be engineered to a single-domain (sd)Ab or a heavy-chain (HC)Ab. The TMU HCAb specifically recognized glycosylated CEACAM6 compared to the conventional antibodies. Using the TMU HCAb, we found that glycosylated CEACAM6 was a tumor marker associated with recurrence in early-stage OSCC (oral squamous cell carcinoma) patients. CEACAM6 promoted OSCC cell invasion, migration, cytoskeletal rearrangement, and metastasis via interaction with epidermal growth factor (EGF) receptor (EGFR) and enhancing EGFR activation, clustering and intracellular signaling cascades. These functions were modulated by N-acetylglucosaminyltransferase 5 (MGAT5) which mediated N-glycosylation at Asn (N256) of CEACAM6. Finally, the TMU sdAb and HCAb treatment inhibited the migration, invasion and EGF-induced signaling in CEACAM6-overexpressing cells. In conclusion, the complex N-glycosylation of CEACAM6 is critical for EGFR signaling of OSCC invasion and metastasis. Targeting glycosylated CEACAM6 with the TMU sdAb or TMU HCAb could be a feasible therapy for OSCC.

3D Structure and Function of Glycosyltransferases Involved in N-glycan Maturation

“…The β1-6 branch formation catalyzed by GnT-V regulates the physiological activities of substrate glycoproteins such as TCR, integrins, growth factor receptors, and cadherins [16,107]. The β1-6 branch formation of some substrates such as E-cadherin and CEACAM6 is known to occur in a glycosylation site-specific manner [108,109]. A docking model of GnT-V E-cadherin complex suggests that the narrow catalytic cavity of GnT-V is a strong determinant for modification.…”

Structure and mechanism of cancer-associated N-acetylglucosaminyltransferase-V

“…Furthermore, formation of the β1-6 branch on cadherins and integrins impacts on their adhesive properties and inhibits cell adhesion and enhances cell migration 21 – 23 , aiding cancer invasion and metastasis. Interestingly, GnT-V activity toward several substrate glycoproteins is N -glycosylation site specific 22 , 24 . Accumulating evidence strongly suggests that the β1-6 branch produced by GnT-V promotes both cancer initiation and progression, and that GnT-V inhibitors are feasible drug candidates.…”

High Throughput Multiplex SNP-analysis in Chronic Obstructive Pulmonary Disease and Lung Cancer

“…Elevated levels of β1-6 branched glycans are characteristic hallmarks of various tumors [40,41], and overexpression of MGAT5 is frequently seen in cancer [42,43]. As far as the molecular mechanism is concerned, Chiang et al [44] found that MGAT5 catalyzed the N-glycosylation of CEACAM6 (carcinembryonic antigen-related cell adhesion molecule 6), a cell surface marker and interacting partner of epidermal growth factor receptor (EGFR). Glycosylation of CEACAM6 by MGAT5 is indispensable for EGFR clustering and activation as key signaling events leading to invasion and metastasis of oral squamous cell carcinoma.…”