A 2026 D peptide as the putative pancreatic cancer-associated diabetogenic factor

Aims of this study ware to: 1) Verify whether culture media conditioned (CM) by different pancreatic cancer (PC) cell lines (CL) are able to alter glucose metabolism of isolated and perfused rat hepetocytes (IPRH); 2) Separate PC CM into fractions with different molecular weights (mw) and assess their metabolic effects on I PRH; 3) Analyze the molecular composition of control (NCM) and CM by mass spectrometry analysis (MALDI); 4) Verify whether any of these components is also detectable in the sere of control subjects (CS, n=lO), pts with chronic pancreatitis (CP, n=9), or with pancreatic cancer (PC, n =14). The association with diabetes mallitus was also considered. Methods: the following PC CL were used: MIA PaCe2, PSI(, PANC-1, and CAPAN-I. The calls (about 100,000/75 cm 2 flask) were cultured in appropriate low glucose cell culture media additioned with 10% FCS for 6 days; the culture media were then centrifuged and the supematants collected (CM) for the experiments with IPRH; NCM was used as control. Two fractions for CM and NCM, one with a mw <30,000 D and another <10,000 D, were obtained after two steps filtration. IPRH, isolated from fasting male Wistar rats (130-250 g b.w.), were incubated with NCM or CM and glucose 20 raM. The IPRH suspension was sampled at time intervals for 2 hours. In the supematants glucose and lactate ware measured. Results: In all experimental conditions, glucose concentration declined similarly over time, while lactate production was inhibited when the IPRH were incubated with the CM from all the PC call lines. This inhibitory effect was reproduced also by CM with a mw <10,000 D. After MALDI analysis of this fraction, the following common peptides (pep)wara identified in CM and NCM: 1667, 1795,1952, 2065, 2144, 2193, 2272 and 2399D. A pep of 1874 D was expressed by all CM, another of 2026 D was expressed by 3/4 PC CL, and a 2726 D pep was expressed by 2/4 PC CL. Other low molecular weight pep were occasionally expressed by single PC cell lines. The pep with a mw of 2026, 2397 and 2726 D were found in patient's sere as follows: the 2026 D pep was identified in 1/10 CS, 7/14 PC, and 3/9 CP; the 2397 D pep in 5/10 CS, in 12/14 PC, and in 6/9 CP, the 2726 D pep in 0/10 CD, 11/14 PC, and 3/9 CP. Only the 2026 D pep was found to be associated with the presence of diabetes (Rsher's exact test:p<O.O5). Conclusions: The production of a diabetogenic factor is common to several PC cell lines. A component of 2026 D is significantly correlated with PC and diabetes, while another of 2726 D is tumor, but not diabetes associated