Fig. 1.

Targeted detection of secreted kallikrein proteins in cell-conditioned medium of pancreatic cancer cell lines by selected reaction monitoring. Serum-free, cell-conditioned medium of five pancreatic cancer cell lines (MiaPaCa-2, AsPC-1, PaCaDD-165, PaCaDD-159, MaPaC-107) were analyzed in a randomized sample order using selected reaction monitoring (SRM) to enable targeted detection and comparison of secreted kallikreins. The assay allowed for the detection of (a) KLK6 with three peptides and (b) KLK10 with two peptides, each of them with several fragments, exemplarily depicted below as co-eluting chromatographic peaks in different colors. Furthermore, (c) KLK3, (d) KLK5 and (e) KLK7 was detected with one or two peptides. Detected peak areas were successively normalized to avidin as internal standard and to the total cell number the CCM derived from. Bar plots show normalized peak area ratios after 2-step normalization for each peptide in each of the investigated cell lines. Error bars correspond to standard deviation.