R,S-4-Methoxy-1-naphthylfenoterol, MNF, inhibits the G protein-coupled receptor GPR55. In this study, we determine the effect of MNF on human PANC-1 pancreatic tumor growth in mice and apply multiplatform metabolomics analysis to identify pathways associated with growth arrest.
Methods: Female Balb/c nude mice, 6-8 weeks old, 18-20g, were inoculated subcutaneously with 5 x 106 PANC-1 cells. On Day 8, mice were placed in groups of 10 using random block design based upon tumor volume. Mice received daily ip injections of vehicle or 40mgxkg-1 MNF 5 days/week for 3 treatment cycles. Mice were monitored daily and tumor volumes measured at beginning and end of each dosing cycle. On Day 33, mice were euthanized, and plasma samples and tumors collected. Tumor tissue was homogenized, extracted and analyzed using liquid chromatography-QTOF-MS, capillary electrophoresis-TOF-MS and gas chromatography-EI-Q-MS. Differences between groups were evaluated by unpaired t-test or Mann−Whitney test with post hoc Benjamini-Hochberg correction. Statistical significance was set at P≤0.05. Compound identification was accomplished using online databases and in-house standards
Results Tumor volume increased in vehicle-treated mice by ~700%, 142 ± 8 mm3 to 957 ± 79 mm3 and only ~250% in MNF-treated mice, 143 ± 8 mm3 to 259 ± 27 mm3. On Day 33, MNF was not detected in plasma but accumulated in tumor tissues, 43.9 ± 32.7 ng/g. Plasma L-lactate levels were reduced from 3.29 ± 0.66 mmol/L το 2.81 ± 0.60 mmol/L, P≤0.001. Differences in tumor tissue metabolome were observed with MNF compared to vehicle, which was reflected by significant, P≤0.05, changes in relative metabolite signals. MNF treatment was accompanied by the disruption of pyrimidine nucleotide biosynthesis at uridine 5'-monophosphate, UMP, and increased UMP degradation. Moreover, the +237% increase in ophthalmic acid and +95% increase in its precursor 2-aminobutyrate indicate higher oxidative stress and the +51% increase in 2-hydroxyproline suggest greater HFI-1α proteolysis upon MNF treatment.
Conclusions These results are consistent with our previous observations in PANC-1 cells showing that GPR55 inhibition attenuates activation of the EGFR-MEK-ERK, Wnt-β-catenin and PI3K/AKT pathways resulting in lower cyclin D1 expression and halting the cell cycle in G1. The reduction in HIF-1α expression and glycolytic flux in MNF-treated PANC-1 cells is in line with the decline in L-lactate plasma levels in MNF-treated mice. The data from this study indicate that MNF may be useful in the treatment of pancreatic cancer.
Citation Format: Irving W. Wainer, Danuta Dudzik, Michel Bernier, Coral Barbas. Multiplatform metabolomics analysis of growth arrest in pancreatic tumor xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5055. doi:10.1158/1538-7445.AM2017-5055