Antigen-specific ganglioside serological profile of pancreatic and gastric cancer patients by multiple TLC overlay assay and IR-MALDI mass spectrometry

Background: Altered glycosphingolipidome in cancerous tissues and cells reflects the circulatory glycosphingolipid (GSL) profiles, which is advantageous for establishing cancer biomarkers and/or unravelling GSL-associated mechanisms of immunity in cancer. Methods: Here, we combined a microscale extraction of GSLs with multiple overlay TLC assays and IR-MALDI-o-TOF MS and implemented it for the first time in serum analysis of CD75s-, CD15s-, and iso-CD75s-containing sialylated GSLs of ganglio- and neolacto-series. Results: This sensitive antigen-specific targeted GSL workflow enabled the identification of 80 sialylated GSLs containing the specific antigens in human sera and was applied for the investigation of clinical serum samples from gastric/stomach cancer patients (n = 40), pancreatic cancer patients (n = 40), and a cancer-free control group (n = 20). The CD75s-, CD15s-, and iso-CD75s-containing GSL series encompassing complex monosialylated and fucosylated GSLs of neolacto-series, with up to pentadecasaccharide chains, were detected in both cancer types, while differential semi-quantitative analysis indicates a tumor type-specific associated GSL profile. Both cancer types share a drop in the complex fucosylated neolacto-gangliosides during tumor progression, implying a decreased synthesis of long-chain neolacto-series. Conclusions: This drop suggesting a role of these highly polar complex ganglioside species in evading humoral tumor immune response in the early tumor stages.