(a) Purpose: Gangliosides are molecules composed of glycosphingolipids linked with one or more sialic acids, and are known to be key components of lipid rafts, which act as platforms for signal transduction. Changes in ganglioside levels affect the expression of raft-associated proteins on the cell surface and lead to reduced membrane fluidity, thus, resulting in cellular dysfunction, such as impaired signal transduction. The ganglioside GM2 is one of the major series of gangliosides that has several biological functions, such as in cell adhesion and signal transduction. GM2 is highly expressed in several types of human malignant tumors, such as melanomas, gliomas, and neuroblastomas, but is absent or weakly expressed in normal tissues. However, the association between gangliosides and pancreatic ductal adenocarcinoma (PDAC) has not been elucidated yet. Thus, in this study, we aimed to clarify the expression and role of ganglioside GM2 in PDAC.
(b) Experimental procedures: GM2 expression in eight human PDAC cell lines was examined by fluorescence-activated cell sorter (FACS) analysis. The morphology, growth, and stemness of GM2- and GM2+ sorted-cells were compared by transmission electron microscopy, growth assays, real-time PCR analysis of the markers of stemness, and sphere forming assays. Cell motility was evaluated by invasion assay. For comparing tumorigenicity between the GM2- and GM2+ sorted-cells, heterotopic implantations were performed. The expression levels and clinico-pathological roles of GM2 in patients with PDAC were examined by immunohistochemical analysis of 117 pancreatic tissue samples.
(c) Results: The fraction of GM2+ cells was the highest (21.4%) in MIA PaCa-2 from among the eight cell lines, as revealed by FACS analysis. GM2-expressing MIA PaCa-2 cells had higher growth rates under adherent growth conditions. In 3D-culture, which enriches cancer stem cells (CSCs), most MIA PaCa-2 cells expressed GM2 and the cells responded to TGF-β1 treatment to promote invasion. Transplantation of the GM2-expressing cells into nude mice resulted in development of larger tumors as compared to that for control cells that did not express GM2. In the PDAC cases, GM2 expression was significantly associated with younger age, larger tumor size, advanced stage, and higher histological grade.
(d) Conclusions: We show that a PDAC cell line overexpressing GM2 exhibits high growth rate and high tumor initiation in 2D-culture. Further, pancreatic CSC-like cells expressing GM2 exhibit responsiveness against TGF-β1, resulting in enhanced invasion in 3D-culture. Furthermore, GM2 expression is associated with the growth and advanced stage of human PDAC. Further studies will be required for the development of an early detection method for GM2-overexpressing pancreatic cancers and to develop novel therapeutic strategies targeting GM2.
Citation Format: Norihiko Sasaki, Kenichi Hirabayashi, Masaki Michishita, Kimimasa Takahashi, Fumio Hasegawa, Fujiya Gomi, Yoko Itakura, Naoya Nakamura, Masashi Toyoda, Toshiyuki Ishiwata. Increased expression of ganglioside GM2 correlates with aggressiveness of human pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 135.