Abstract 15P
Background
Sialoglycan with α-2,3-linked/α-2,6-linked sialic acid (Sia) on the cancer cell surface protects cancer cell from immunologic recognition. Binding of α-galactose/α-N-acetylgalactosamine (Gal/GalNAc) epitope to macrophage galactose type C-lectin receptor (MGL) improves dendritic cell (DC) performance. We identified if modified sialoglycan by neuraminidase (NA) stimulates cellular immune response to EOC.
Methods
Sialoglycan on human EOC OVCAR3, A2780 and mouse ID8 cells was hydrolyzed with α2,6NA. NA-treated and NA-untreated OVCAR3 and A2780 cells were incubated with immature DC (imDC) to achieve NA-DC and nonNA-DC. Human peripheral blood lymphocytes (PBL) were stimulated with NA-DC and nonNA-DC. Gal/GalNAc and α-2,6Sia epitope of EOC cells, phenotypes of DCs and PBL were measured with flow cytometry (FCM); IFN-γ expression by PBL was determined by RT-qPCR; cytotoxicity of PBL to OVCAR3 and A2780 cells were detected by using LDH release assay. NA-treated and NA-untreated ID8 cells were vaccinated subcutaneously in the right axilla of C57 mice once per week for 3 consecutive weeks, then parental ID8 cells were inoculated in the opposite axilla. The tumor growth was observed; IFN-γ of plasm was tested by ELISA.
Results
α-2,6Sia (Sambucus Nigra Lectin, SNA) decreased and Gal/GalNAc (Peanut Agglutinin, PNA) increased in the NA-treated OVCAR3, A2780 and ID8 cells. MGL, CD83 and CD86 on NA-DCs increased significantly; Siglec-9 on NA-DCs and nonNA-DCs for A2780 not OVCAR3 cells decreased markedly compared to imDCs. PBL stimulated with NA-DCs had a higher expression of IFN-γ and CD69 than PBL stimulated with nonNA-DCs did. PBL stimulated with NA-DCs for A2780 but not for OVCAR3 cells showed an enhanced cytotoxicity; the cytotoxicity of PBL stimulated with NA-DCs was slightly higher than that of PBL stimulated with nonNA-DCs for OVCAR3 cells. Tumorigenesis was reduced significantly in the vaccinated mice with NA-treated ID8 cells; the plasm level of IFN-γ was significantly increased in the vaccinated mice.
Conclusions
NA modified sialoglycan structure could promote immune response to EOC.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.