The patterns of amyloid beta (Abeta) peptides in human cerebrospinal fluid (CSF) and brain homogenates were studied by surface-enhanced laser desorption/ionization (SELDI) time-of-flight (TOF) mass spectrometry, and the results were compared with those obtained by Abeta-SDS-PAGE/immunoblot. Apart from the peptides known in the literature to occur in the CSF, we postulate the existence of a novel, previously not described peptide, either Abeta1-45 or Abeta2-46. This peptide was observed exclusively in a pool of samples originating from patients with AD, i.e. CSF and postmortem brain homogenates, but not in either the pooled CSF samples nor the pooled brain homogenates of the non-demented controls. Similarly to our previous results, Abeta1-42 was decreased in the CSF in AD. Expectedly, brain homogenates of the control subjects did not show the presence of Abeta peptides. Compared with Abeta-SDS-PAGE/immunoblot, SELDI-TOF enabled more precise analysis of Abeta peptides in the human material. We conclude that SELDI-TOF offers a promising tool for dementia expression pattern profiling using a minute amount of a biological sample.

DNA chip technologies are the most exiting genomic tools, which were developed within the last few years. It is, however, evident that knowledge of the gene sequence or the quantity of gene expression is not sufficient to predict the biological nature and function of a protein. This can be particularly important in cancer research where post-translational modifications of a protein can specifically contribute to the disease. To address this problem, several proteomic tools have been developed. Currently the most widely used proteomic tool is two-dimensional protein gel electrophoresis (2-DE), which can display protein expression patterns to a high degree of resolution. As an alternative to 2-DE, a preliminary study using a new technique was employed to generate protein expression patterns from whole tissue extracts. Surface-enhanced laser desorption/ionization (SELDI) allows the retention of proteins on a solid-phase chromatographic surface (ProteinChip Array) with direct detection of retained proteins by time of flight-mass spectrometry (TOF-MS). Using this system, we analyzed eight cases of renal cell carcinoma (RCC) including normal, peripheral and central tumor tissue as well as four microdissected cases of cervical intraepithelial neoplasia (CIN) and three microdissected cases of cervix uteri carcinoma. Differentially expressed proteins were found by comparing the protein expression patterns generated using SELDI-based TOF-MS of tumor tissue with normal and neoplastic tissue, respectively. By applying this fast and powerful ProteinChip array technology it becomes possible to investigate complex changes at the protein level in cancer associated with tumor development and progression.

A large number of genes are known to be differentially expressed at distinct steps of carcinogenesis. By using a cell culture model system for cervical cancer, we had previously identified several genes that were more strongly expressed when comparing normal cervical epithelium with cervical intraepithelial neoplasia (CIN) and cervical cancer. In our study, we show that one of these genes, C4.8, is identical to NET-1, which is a new member of the tetraspanin family of proteins. By generating a mouse polyclonal antiserum against the major extracellular domain of the protein, we could detect NET-1/C4.8 expression both after ectopic expression of the gene in cell cultures and in cryostat sections of cervical biopsies. Moreover, immunohistochemic analyses of normal cervical epithelium, metaplasia, condyloma and CIN of different severity suggest that NET-1/C4.8 expression is associated with neoplastic cell proliferation. Notably, expression of the protein throughout the entire epithelium is only evident for a subset of CIN3. The potential importance for this gene in cervical carcinogenesis is underlined by an invariably strong expression in all undifferentiated squamous cell cancers examined. This indicates that this gene may be of prognostic value.