MALDI-TOF Mass Spectrometric Analysis of Brain Tumor Cyst Fluid Reveals a Protein Peak Corresponding to ApoC1 and LuzP6
Tumor cysts occur in a multitude of brain
tumors. Since the cyst often forms a closed
compartment, surrounded by tumor cells, proteomic analysis of the cyst fluid
may help in describing pathophysiologic pathways, leading to cyst formation or
tumor growth.
The
surface enhanced laser desorption ionisation mass spectrometry (SELDI-TOF MS),
a highly sophisticated variant of matrix assisted laser desorption ionisation
(MALDI-TOF MS), allows to assess directly cyst fluid protein content in as few
as 2 microliters of specimen.
In the present study, the authors analyzed
whether MALDI-TOF MS examination of these fluids led to comparable results. 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.
The findings showed that 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 glioblas-toma
tissue. The MALDI-TOF spectrometry extends the range of analysis down to 1.4
kDa, whereas the upper detection limit lies below 23 kDa.
In conclusion, the presented proteomic
approach yielded an inventory of protein masses, found in the tumor cyst at the
time of puncture. However, it did not reveal pathophysiologic, metabolic or
secretory pathways that led to the presence of proteins in the cyst. These have
to be assessed immunohistochemically or on mRNA level in the surrounding tumor
cells. And mass spectrometric analysis by
laser-desorption ionization is a feasible tool to assess brain tumor cyst
protein content in comparison to cerebrospinal fluid. A thorough work-up,
including internet-based data research, immunohistochemistry and mRNA-analysis
is needed to describe the obtained results in detail and to develop hypotheses
concerning biomarkers.
Article
by Mathias Groll, et al, from Germany.
Full
access: http://mrw.so/5nKLSH
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