Identification of potential serum biomarkers of pancreatic cancer

The aim of this study was to verify whether discontinuous SDS-PAGE, performed in the conditions that allowed the isolation of S100A8 aminoterminal peptide from pancreatic cancer (PC) tissue, can identify potential serum markers of PC and PC induced diabetes mellitus (DM). We collected sera from 42 PC patients (17 with and 25 without DM) and from 11 healthy controls (C). In the low MW range (1 to 15 kDa), nine protein bands were identified and numbered 1 to 9 from heaviest to lightest. Only band number 2 (similar to 14.2 kDa) was correlated with PC diagnosis, being present in 10 out of 11 C and absent in 37 out of 42 PC cases (P <0.001). Bands 4 and 9 (MW 10 and 1 kDa, respectively) correlated with each other (P <0.05). In PC patients, the absence of both bands correlated with the presence of DM (P <0.01 for band 4 and P <0.05 for band 9) and was significantly associated with higher fasting plasma glucose concentrations (P <0.05 for band 4 and P <0.01 for band 9). The absence of band 9 was also significantly associated with HbA1c (P <0.05) and with glucose/C-peptide ratio (P <0.05). To characterize the protein inversely correlated with PC diagnosis, we performed a matrix-assisted laser desorption ionization time-of-flight/mass spectrometry (MALDI-TOF/MS) analysis of the tryptic in-gel digestion of band 2. The identified peaks were analysed by Mascot peptide mass fingerprint and showed a high homology with human hemoglobin subunit beta (score 76, P < 0.05). SDS-PAGE analysis of the low MW serum proteins allowed the detection of peptides correlated with PC derived DM and the identification of free beta-globin as a potential PC serum marker.