Searching For New Therapeutic Targets Of Glioma With MALDI Imaging

Objectives:Glioma is the most common malignant tumor in the central nervous system.Glioma patients are usually found to be in the advanced stage at diagnosis because lack of effective diagnosis methods.The main diagnosis methods for glioma patients include disease history questionnaire,nervous system physical examination and imaging modalities examination.It is very difficult to achieve early discovery for glioma using these traditional diagnosis methods.The principal treatment measure for glioma patients is resection,then radiation therapy and chemotherapy are used as adjuvanticity treatment means.The infiltration property of glioma makes it impossible fol exhaustive removal of glioma tissue.The recrudescence possibility for glioma patients is high.Therefore,it is necessary to search biomarkers and new therapeutic targets for glioma.Proteomics technology employs biological mass spectrometry technology to study the protein expression characteristics of all research samples,and it can be used in many research areas such as tumor biomarkers screening,pathological mechanism and cancer therapeutic targets exploring.Imaging mass spectrometry is a powerful tool for proteomics research.It can collect mass spectrometry information of hundreds of peptides,proteins and lipids from tissue sections.The relative abundance and spatial distribution information of these collected peptides,proteins and lipids will appear as two-dimensional or three-dimensional images.The purpose of this study is to distinguish the differential expression of lipids in glioma tissues and normal brain tissues by MALDI imaging mass spectrometry.Meanwhile,the identification of these differential expression lipids was done to find new therapeutic targets for glioma treatment.Materials and Methods:Six tissues from three cases of patients with brain gliomas and three cases of traumatic brain injury patients were selected as research samples.These glioma tissues and normal brain tissues were treated by freezing microtome with a thickness of 10um.Tissue sections were posted on the conductive glass slides,and then they were covered by DHB.UltrafleXtreme MALDI TOF/TOF was used to detect these samples,and Fleximaging software was used for data processing.The differential expression mass spectrometer peaks were identified to be lipids.Immunofluorescence and western-blot methods were used to study the function of these differential expression lipids through glioma tissue U373-MG.Results:Six tissue samples from three cases of patients with brain gliomas and three cases of traumatic brain injury patients are analyzed using the instrument MALDI-TOF/TOF MS.The result is analyzed using the software of FlexImaging.We found that there are 117 mass peaks differently between in the brain gliomas tissue and the normal control.The abundance of 58 peaks is higher in the normal brain tissue.And the abundance of 59 peaks is higher in the glioma tissue than in the normal brain tissue.After identified with MS/MS,18 peaks were identified as Sphingomyelins.Among the 18 peaks,12 lipids are highly expressed in the glioma tissue and 6 lipids are highly expressed in the normal tissue.Then we found the UV and X ray can make the ceramide shape to be patch on the surface of the glioma cell U373-MG The drugs desipramine and?-mangostin reduce the ceramide on the surface of the cell.The drug desipramine can inhibit the activation of the Insulin like growth-1 factor and the PI3K/AKT signaling pathway.Conclusions:In our research,we found lipids with different expression between the glioma tissue and the normal brain tissue using the MALDI Imaging technology.Sphingoyelin is expressed more highly in the glioma tissue than which in the normal brain tissue.When we inhibit the metabolism of Sphingomyelin on the surface of the glioma cell,we can inhibit the activation of IGF-1R and the PI3K/AKT signaling pathway.So the lipid Sphingomyelin can be a new therapy target for the glioma.