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Tumor cells are changing their genetic expression pattern as they progress to states of increasing malignancy. Investigations at the DNA and RNA level alone do not provide all the information resulting after the translation and processing of the corresponding proteins, which explains reports on a poor correlation between mRNA and the respective protein abundance. Unfortunately, peptides produced by cancer cells are secreted only in very low amounts, making mass spectrometric determination very difficult. In this work, methods have been evaluated for the effective enrichment and cleanup of substances secreted by cancer cells. To avoid peptides from fetal calf serum, a serum surrogate was developed, which do not alter the growth rate of the cancer cells. After binding of substances from cell culture supernatants with own manufactured magnetic reversed phase particles, the substances were eluted and separated by capillary HPLC. Fractions were spotted directly on a MALDI-target and MALDI-TOF mass spectrometric data acquisition was performed in automatic mode.
During the investigation of two mamma carcinoma cell lines (MCF-7, non invasive, and MDA-MB231, invasive), unequivocal differences in the peptide secretion patterns were observed. In conclusion, this system allows the sensitive investigation of peptides secreted by cancer cell lines and will be used in the future for the investigation of cancer cell lines in different states of malignancy.