A 2030 D peptide as the putative pancreatic cancer-associated diabetogenic factor

Introduction: Aims were to verify: (1) whether entire and mw fractioned cell culture media conditioned (CM) by pancreatic cancer (PC) cell lines are able to alter glucose metabolism of isolated and perfused rat hepatocytes (IPRH); (2) the molecular composition of control (NCM) and CM by mass spectrometry analysis (MALDI); (3) which component is detectable in sera of control subjects (CS, n10), patients with chronic pancreatitis (CP, n9) or with pancreatic cancer (PC, n14) and whether they are associated with diabetes mellitus. Methods: CM from 6 days cultured MIAPaCa2, PSK1, PANC1 and CAPAN1 lines were used. CM and NCM were fractioned (mw less than 30,000 D and mw less than 10,000 D). IPRH from male Wistar rats were incubated with NCM or CM in the presence of glucose 20mM. Results: Lactate production was inhibited when the IPRH were incubated with the CM from all the PC lines. This inhibitory effect was reproduced also by CM with a mw less than 10,000 D. MALDI analysis revealed two peptides, of 1874 D and of 2030 D, expressed by all CM, and another of 2726 D expressed by 2/4 PC lines. The peptides with a mw of 2030, 2397 and 2726 D were found in some patients’ sera: the first was identified in 1/10 CS, 7/14 PC and in 3/9 CP, the second in 5/10 CS, 12/14 PC and in 6/9 CP, the third in 0/10 CD, 11/14 PC and in 3/9 CP. Only the 2030 D component was found to be associated with the presence of diabetes considering PC patients (Fisher’s exact test: p0.05), even if low amounts were found in three CP patients, one of which was diabetic. Conclusions: The production of a diabetogenic factor is a phenomenon common to several PC lines; this diabetogenic factor has a mw less than 10,000 D; among the large number of molecules identified in cell culture media and in patients’s sera with a mw less than 10,000 D, a component of 2030 D seems to be that more significantly correlated with PC associated diabetes.