Glioblastoma: Validation and Comparison Between Primary Tumor and Its Murine Model

The presented project will focus on the evaluation of a multimodal approach comparing human GBM to paired samples of orthotopic xenografts using high resolution MRI and MRS and multidimensional molecular profiling.

20 patients with a high probability for newly diagnosed GBM based on MRI-scan ( 3 Tesla (3T) MRI, T1, T2, T1 gadolinium, DWI \& MRI Spectroscopy) will be identified in the CHUV prior to undergoing neurosurgical resection. Patients will undergo extensive experimental radiological examination using specific MRI sequences on the 7 Tesla (7T) MRI to identify specific metabolic pathways (see below, section on imaging). Thereafter patients will undergo maximal safe neurosurgical resection of their tumors. The portion of the tumor that is not used for diagnostic purposes will be collected immediately for further use (see below, section on molecular evaluations). Following resection, patients will undergo standard of care treatment [usually combined radio-chemotherapy, or will be offered participation in a clinical trial. The clinical parameters will be collected, including histopathological features and the evolution and growth pattern of the residual tumor (if present), or the development of recurrences will thereafter be compared to the parameters and evolution of the xenograft models.

At high magnet field strength (7T), high signal-to-noise ratio and increased spectral dispersion allow more reliable measurement of a large number of metabolites using Magnetic Resonance Spectroscopy in comparison to clinical available field strengths (3T and below). In addition, the authors have developed a full sensitivity short-echo-time single voxel spectroscopy (SVS) sequence "semi-adiabatic SPECIAL"(2) which was implemented, validated at 7T and allows the quantification of 15 metabolites with high precision including N-acetylaspartate(NAA), glutamine(Gln), glutamate(Glu), myo-inositol(Ins), phosphorylethanolamine(PE), total choline(tCho), creatine, phosphocreatine, N-acetylaspartylglutamate(NAAG), lactate(Lac), glutathione(GSH), aspartate (Asp), taurine(Tau), scyllo-inositol and γ-aminobutyric acid(GABA). This localization technique was further extended to a MR Spectroscopic Imaging (MRSI) technique at 7T, which allows mapping of the spatial distributions of cerebral metabolites. Furthermore, glycine is a possible marker for tumor malignancy and its detection in vivo has been established in our previous study using TE=30ms with SPECIAL sequence at 7T. Therefore, in this study the aforementioned techniques will be used to obtain the neurochemical information and its spatial distribution in the glioblastoma of the patients. These data will be further compared with the neurochemical information obtained in the orthotopic xenografts in the mouse brain derived from the respective glioblastoma patient.

All MRS measurements of glioblastoma patients will be performed on a 7T MR scanner with a CP Transmit / 32 channel receive array head coil. Based on the high resolution T1-weighted images obtained using the MP2RAGE sequence, Volume of Interest (VOI) for spectroscopy will be placed according to the location of the glioblastoma. Total acquisition time of MRS will be within 30 min. In vivo MRS spectra will be post-processed and metabolite concentrations will be quantified to create metabolite maps.

Molecular and functional investigations of paired samples of primary glioblastoma and respective orthotopic xenografts in the mouse

The aim of the present study is to determine the molecular, histopathological, and functional properties, including growth patterns such as invasiveness, of the original GBM and the respective derived orthotopic xenografts in the mouse, and link them to imaging/ metabolism parameters obtained by high resolution MRI.

GBM samples from patients collected at surgery will be divided into 2 parts, (i) snap frozen for molecular analyses, and (ii) cultivated under stem cell conditions for subsequent stereotactic transplantation into male immune-compromised mice and establishment of sphere lines.