Mass spectrometric analysis of glioblastoma cyst fluids has disclosed a protein peak with m/z 6424–6433. Among the proteins, potentially generating this peak are ApoC1 and LuzP6. To further elucidate protein expression of glioblastoma cells, we analyzed MALDI–TOF results of cyst fluid, performed immunohistochemistry and mRNA analysis. MALDI–TOF protein extraction from 24 glioblastoma cyst fluids was performed with a weak cation exchange. 50 glioblastoma samples were stained with two custom-made antibodies against LuzP6 and commercial antibodies against ApoC1, C12orf75 and OCC-1 and analyzed. For mRNA detection, 16 tissue samples were stored in RNAlater, extracted using the miRNeasy kit and reversely transcribed. For 12 patients, synopsis of results from all three examinations was possible. MALDI–TOF confirmed the peak at 6433 Da in 75% of samples. Immunohistochemically, LuzP6 was detected in 92% (LuzP61–29) and 96% (LuzP630–58) of samples and ApoC1 in 66%. Mean mRNA levels were highest for ApoC1, followed by LuzP6. No correlation between mRNA expression, immunohistochemical staining and intensity of the MALDI–TOF peaks was found. An unequivocal identification of one protein as the source for the 6433 peak is not possible, but our results point to ApoC1 and LuzP6 as the underlying proteins.Electronic supplementary materialThe online version of this article (10.1007/s00795-019-00223-8) contains supplementary material, which is available to authorized users.

Objectives: SELDI-TOF and MALDI-TOF mass spectrometry (MS) are laser desorption technologies that allow for proteomic examination of molecular masses in small amounts of samples. In a precedent study, the feasibility of SELDI-TOF MS assessment of proteins in cerebrospinal fluid and tumor cyst fluid had been shown. In the present study, we analyzed whether MALDI-TOF MS examination of these fluids leads to comparable results. Methods: During neurosurgical intervention, cyst fluids from 24 glioblastomas and 15 metastases were collected. As control, cerebrospinal fluid samples from 23 patients were obtained. The samples were prepared using a protocol optimized for MALDI-TOF MS. Mass spectra were recorded and peaks were extracted, characterized by masses and relative intensities. These peaks were analyzed for statistically significant differences between the diagnosis groups and compared to SELDI-TOF MS data. Results: 41 protein peaks known from the SELDI-TOF MS analysis could be confirmed by MALDI-TOF MS, and the cellular expression of the proteins LuzP6 and ApoC1, corresponding to the protein peaks 6433 and 6632, was shown immunohistochemically in glioblastoma tissue. The MALDI-TOF spectrometry extends the range of analysis down to 1.4 kDa, whereas the upper detection limit lies below 23 kDa. Discussion: The presented proteomic approach yields an inventory of protein masses, found in the tumor cyst at the time of puncture. It does not reveal pathophysiologic, metabolic or secretory pathways that lead to the presence of proteins in the cyst. These have to be assessed immunohistochemically or on mRNA level in the surrounding tumor cells. Conclusion: MALDI-TOF MS of How to cite this paper: Groll, M., Frenzel, 252Open Journal of Modern Neurosurgery tumor cyst fluid discloses protein sizes, overexpressed or lost in tumor tissue. A thorough proteomic work-up is needed to identify the underlying proteins and metabolic pathways.

The proposed detection method delivers accurate locations of cervical vertebrae in MR images which can be used in diagnosis and therapy. In order to achieve absolute comparability with the results of future work, the authors are following an open data approach by making the image dataset used in their performance evaluation available to the public.

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