Aggregation of Mutant p53 Alters Sialylated and Sulfated Glycan Profiles and Enhances Siglec-9 Ligand Availability in Ovarian Cancer.

PURPOSE: Mutant p53 proteins form aggregates, and the presence of such cytoplasmic p53 aggregates has predicted poor prognosis in several cancers including high-grade serous ovarian cancer (HGSOC). The existence of aberrant expressions of sialylated and sulfated glycans is a major feature of various cancers. At present, the correlation between the presence of cytoplasmic p53 aggregates and the existence of aberrant glycosylation in cancers is unclear. Here, we investigated whether the presence of p53 aggregates may affect sialylated and sulfated glycan profiles in HGSOC.

MATERIALS AND

METHODS

We used the CL40 monoclonal antibody that recognizes sialyl 6-sulfo Lewis X and sialyl 6-sulfo N-acetyllactosamine and a cell-permeable p53 aggregation inhibitor ReACp53. HGSOC tissues were examined by immunohistochemistry with CL40. Expressions of GlcNAc-6-O-sulfotransferases (GlcNAc6STs) in HGSOC-derived OVCAR-3 cells were analyzed by means of semi-quantitative PCR. Binding of sialic acid-binding immunoglobulin-like lectin Siglec-9 to OVCAR-3 cells were analyzed by using His-tagged Siglec-9.

RESULTS

OVCAR-3 cells expressed CL40-reactive glycans, but CL40 reactivity was reduced by p53 disaggregation. Immunohistochemical analyses revealed expression of CL40-reactive glycans in p53 aggregate-positive HGSOC cases. Recognition of glycans by CL40 requires 6-O-sulfation of the N-acetylglucosamine (GlcNAc) residues, which are catalyzed by GlcNAc6STs. mRNA expressions of GlcNAc6ST2/CHST4, GlcNAc6ST3/CHST5, and GlcNAc6ST5/CHST6 were down-regulated in the presence of ReACp53. Pretreatment of OVCAR-3 cells with CL40 prevented the binding of Siglec-9 and OVCAR-3 cells, which suggested that CL40 epitopes could be recognized by the Siglec-9 lectin.

CONCLUSIONS

Our results together suggest a novel mechanism of aberrant glycosylation in HGSOC associated with p53 aggregation.