Abstract 1185: Altered choline metabolism in pancreatic cancer cells and tumor xenografts

Abstract

Abstract Early-stage pancreatic cancer is usually clinically silent, and most patients presenting symptoms attributable to pancreatic cancer have advanced disease. Better understanding of the disease, effective detection methods, and new therapeutic targets are urgently needed to improve its outcome. Magnetic resonance spectroscopy (MRS) is being evaluated in the diagnosis of several solid malignancies (1). A hallmark of most solid tumors is the detection of elevated levels of phosphocholine (PC) and total choline (tCho) (1). The increase in PC levels in solid tumors has been attributed to high level of choline kinase (Chk)-alpha (2). Here, we characterized the metabolism of multiple pancreatic ductal adenocarcinoma cell lines and tumors with in vitro high resolution MRS and in vivo 1H magnetic resonance spectroscopic imaging (MRSI). We also characterized the expression of Chk-alpha in the cells and tumor extracts. Eight pancreatic adenocarcinoma cell lines (Panc1, BxPC3, Pa04C, Pa02C, Pa20C, Pa28C, Pa03C, and Pa09C) and one immortalized pancreatic cell line (human pancreatic nestin expressing (HPNE)) were investigated. For the in vivo experiments, cells were inoculated subcutaneously in male SCID mice. Once tumors reached 500 mm3, the mice were scanned on a 4.7T spectrometer for 1H MRSI, after which the tumors excised for immunoblot analysis, and high-resolution 1H MRS. Cells and tumor extracts were carried out as previously described (3). Fully relaxed 1H MR spectra of the extracts were acquired on a Bruker Avance 500 spectrometer at 11.7 T. Integrals of the metabolites of interest were determined and normalized to the number of cells and to the tumor weight respectively. Significant differences in tCho were identified in pancreatic cell lines and the tumor xenografts. In the panel of cell lines, the differences in tCho levels were associated with differences in Chk-alpha expression. PC and tCho levels were significantly elevated in the pancreatic cancer cell lines compared to the immortalized pancreatic cell line, and Chk-alpha was overexpressed in the cancer cell lines. In vivo studies revealed that elevated tCho was detected in tumors derived from the 4 cell lines tested, with higher levels of tCho in Panc1 tumors. These in vivo results were confirmed by ex vivo MRS analysis of the tumor extracts. The high level of tCho observed in Panc1 tumors was mainly due to increased PC, and correlated with high Chk-alpha expression observed in the immunoblots. These data support the use of 1H MRS to noninvasively detect pancreatic cancer. Moreover, the aberrant choline metabolism may provide novel targets in the treatment of pancreatic cancer. Acknowledgement: This work was supported by NIH P50CA103175. *Equal contribution.