Supplemental Figure 1: Chemical structures of mitochondria-targeted metformin analogs and the synthetic pathway. Supplemental Figure 2: Effects of Met and Mito-Met10 on proliferation of mouse pancreatic cancer cells. Supplemental Figure 3: The effects of Mito-Met10, Met and other mitochondria-targeted agents (MTAs) on intracellular ATP level and cell death in MiaPaCa-2 cells. Supplemental Figure 4: Mito-Met10, but not control long chain compound (Dec-TPP+), exhibits selectivity in inhibition of cancer cell viability. Supplemental Figure 5: Effects of Mito-Met2 and Mito-Met6 on PDAC proliferation. Supplemental Figure 6: Intracellular concentrations of Mito-Met10 in cancer and normal cells. Supplemental Figure 7: Intracellular redox signaling in Mito-Met10-treated PDAC cells. Supplemental Figure 8: Measurement of respiratory activity in permeabilized cells using extracellular flux analysis and effects of Mito-Met10 and Met on mitochondrial complex I activity. Supplemental Figure 9: Mito-Met10 and metformin directly inhibit pyruvate-driven, but not succinate-driven, respiration in permeabilized cells. Supplemental Figure 10: High concentrations of Mito-Met10 induce cellular oxidants in HPNE cells. Supplemental Figure 11: Tissue accumulation of Mito-Met10 in in vivo FC-1242-luc orthotopic mouse model.
Funding
NIH National Cancer Institute
Medical College of Wisconsin Cancer Center
Aix-Marseille Université CNRS
ARTICLE ABSTRACT
Metformin (Met) is an approved antidiabetic drug currently being explored for repurposing in cancer treatment based on recent evidence of its apparent chemopreventive properties. Met is weakly cationic and targets the mitochondria to induce cytotoxic effects in tumor cells, albeit not very effectively. We hypothesized that increasing its mitochondria-targeting potential by attaching a positively charged lipophilic substituent would enhance the antitumor activity of Met. In pursuit of this question, we synthesized a set of mitochondria-targeted Met analogues (Mito-Mets) with varying alkyl chain lengths containing a triphenylphosphonium cation (TPP+). In particular, the analogue Mito-Met10, synthesized by attaching TPP+ to Met via a 10-carbon aliphatic side chain, was nearly 1,000 times more efficacious than Met at inhibiting cell proliferation in pancreatic ductal adenocarcinoma (PDAC). Notably, in PDAC cells, Mito-Met10 potently inhibited mitochondrial complex I, stimulating superoxide and AMPK activation, but had no effect in nontransformed control cells. Moreover, Mito-Met10 potently triggered G1 cell-cycle phase arrest in PDAC cells, enhanced their radiosensitivity, and more potently abrogated PDAC growth in preclinical mouse models, compared with Met. Collectively, our findings show how improving the mitochondrial targeting of Met enhances its anticancer activities, including aggressive cancers like PDAC in great need of more effective therapeutic options. Cancer Res; 76(13); 3904–15. ©2016 AACR.
