Abstract 1434: Metformin-induced metabolic changes are k-ras-dependent in animal models of pancreatic cancer
Authors: Cantoria Mary J. , Boros Laszlo G. , Patel Hitendra , Han Haiyong , Ignatenko Natalia , Meuillet Emmanuelle J. 
Published: May 2015

Pancreatic ductal adenocarcinoma (PDA) is an aggressive malignancy, that is very difficult to treat. To date, systemic treatment for PDA, either a single agent or combinations of agents, has shown only modest benefits. Numerous epidemiological studies have reported that metformin (MET), a widely used anti-diabetic drug, provides protective benefits in reducing PDA risk among the diabetic population. Using a stable isotope glucose (GLUC) tracer for dynamic metabolic profiling (SiDMAP), we recently reported that high cholesterol (CHOL) alters the cellular metabolism of MiaPaCa2 (a PDA cell line harboring mutant K-Ras) cells by redirecting glucose-derived acetyl-CoA toward fatty acid (FA) synthesis. This response to MET is depended on the level of intracellular CHOL synthesis. We now performed a SiDMAP study in the LSL-K-RasG12D/+, LSL-Trp53R172H/+, Pdx-1-Cre (KPC) and the LSL-K-RasG12D/+, Pdx-1-Cre (KC) mouse models for PDA, and their wild-type littermates (C57Bl6.129). The mice were treated (or not) with MET (250 mg/kg, i.p. Q5D) and subjected to an Intra Peritoneal GLUC Tolerance Test (IPGTT) pre- and post-MET treatment. The KPC mice with the average tumor volume of 80.83+8.57 mm3 and the KC mice with PanIN lesions (aver. 9 mo old) were put on study. K-Ras mutation, with the presence of the tumor (KPC mice), induced an increase in plasma GLUC production via de novo synthesis by the liver using futile cycling of GLUC derived lactate and pyruvate. MET treatment decreased this flux in mutated (KC) and tumor-bearing animals (KPC), but increased this flux in liver of control mice. MET treatment increased the complete GLUC oxidation into 13CO2 in the pancreas of KC and KPC animals. This indicates that the pancreas in MET-treated animals use less GLUC for RNA, DNA and FA synthesis. For 13CO2 production, we found that tumor growth has to be established; the mutation is not enough to induce changes in this flux. As in plasma, tumor growth increases pancreas lactate production from GLUC. MET treatment dramatically decreased the Warburg effect in the pancreas of mutated (KC) and mutated/tumor-bearing (KPC) mice. Finally, MET decreased GLUC-derived acetyl-CoA delivery to FAS and palmitate in control, mutated and tumor-bearing mice. Immunohistochemical analysis of the tumors from the KPC mice revealed that treatment with MET decreased the staining of phospho-Ser79-ACC by ∼54%, total FAS staining (mainly in the tumor stroma) by ∼43%, and the growth-associated transcription factor HMGA2 by ∼36.7%. These decreases correlated with a decrease in Ki67 staining by almost 80%, indicative of an inhibitory effect of MET on PDA growth. These results suggest that mutant K-Ras is responsible for the metabolic adaptation in both the tumor- (KPC) and non-tumor-bearing animals (KC). Our findings provide a strong rationale for targeting the metabolic changes induced by activated K-RAS in PDA patients which harbor mutations in K-RAS gene in &gt;95% of cases.

Citation Format: Mary Jo Cantoria, Laszlo G. Boros, Hitendra Patel, Haiyong Han, Natalia Ignatenko, Emmanuelle J. Meuillet. Metformin-induced metabolic changes are k-ras-dependent in animal models of pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1434. doi:10.1158/1538-7445.AM2014-1434