Targeting cancer metabolism by simultaneously disrupting parallel nutrient access pathways
Seong M. Kim, … , Stephen Hanessian, Aimee L. Edinger
Seong M. Kim, … , Stephen Hanessian, Aimee L. Edinger
Published September 26, 2016
Citation Information: J Clin Invest. 2016;126(11):4088-4102. https://doi.org/10.1172/JCI87148.
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Research Article Cell biology Metabolism

Targeting cancer metabolism by simultaneously disrupting parallel nutrient access pathways

Abstract

Oncogenic mutations drive anabolic metabolism, creating a dependency on nutrient influx through transporters, receptors, and macropinocytosis. While sphingolipids suppress tumor growth by downregulating nutrient transporters, macropinocytosis and autophagy still provide cancer cells with fuel. Therapeutics that simultaneously disrupt these parallel nutrient access pathways have potential as powerful starvation agents. Here, we describe a water-soluble, orally bioavailable synthetic sphingolipid, SH-BC-893, that triggers nutrient transporter internalization and also blocks lysosome-dependent nutrient generation pathways. SH-BC-893 activated protein phosphatase 2A (PP2A), leading to mislocalization of the lipid kinase PIKfyve. The concomitant mislocalization of the PIKfyve product PI(3,5)P2 triggered cytosolic vacuolation and blocked lysosomal fusion reactions essential for LDL, autophagosome, and macropinosome degradation. By simultaneously limiting access to both extracellular and intracellular nutrients, SH-BC-893 selectively killed cells expressing an activated form of the anabolic oncogene Ras in vitro and in vivo. However, slower-growing, autochthonous PTEN-deficient prostate tumors that did not exhibit a classic Warburg phenotype were equally sensitive. Remarkably, normal proliferative tissues were unaffected by doses of SH-BC-893 that profoundly inhibited tumor growth. These studies demonstrate that simultaneously blocking parallel nutrient access pathways with sphingolipid-based drugs is broadly effective and cancer selective, suggesting a potential strategy for overcoming the resistance conferred by tumor heterogeneity.

Authors

Seong M. Kim, Saurabh G. Roy, Bin Chen, Tiffany M. Nguyen, Ryan J. McMonigle, Alison N. McCracken, Yanling Zhang, Satoshi Kofuji, Jue Hou, Elizabeth Selwan, Brendan T. Finicle, Tricia T. Nguyen, Archna Ravi, Manuel U. Ramirez, Tim Wiher, Garret G. Guenther, Mari Kono, Atsuo T. Sasaki, Lois S. Weisman, Eric O. Potma, Bruce J. Tromberg, Robert A. Edwards, Stephen Hanessian, Aimee L. Edinger

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Figure 6

SH-BC-893 reduces autophagic flux and macropinosome degradation.

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SH-BC-893 reduces autophagic flux and macropinosome degradation. (A) Con...
(A) Control or VAC14-overexpressing HeLa cells treated with 25 μM chloroquine (CQ), with or without 5 μM FTY720, were stained for LC3 and LAMP1 and evaluated by confocal microscopy. (B and C) Quantification of LC3-LAMP1 colocalization (B) and total LC3 puncta (C) in cells treated with chloroquine, with or without FTY720, SH-BC-893, or 800 nM YM201636 for 6 hours. Error bars indicate the mean ± SEM. n ≥35 cells evaluated per condition. (D) Vector or VAC14-overexpressing HeLa cells were nutrient stressed in DMEM lacking amino acids and glucose in the presence or absence of 5 μM FTY720 or SH-BC-893 and stained for WIPI2. (E) Quantification of WIPI2 puncta. Error bars indicate the mean ± SEM. n ≥50 cells evaluated per condition. Statistical significance was compared with the respective low-nutrient control unless otherwise indicated. (F) HeLa cells overexpressing VAC14 were treated with 5 μM FTY720 for 6 hours. (G and H) Dextran uptake in p53–/– LSL-KrasG12D MEFs before (LSL) or after (KrasG12D) introduction of Cre, with or without the macropinocytosis inhibitor EIPA, SH-BC-893, or YM201636 (G). Colocalization of dextran and LysoTracker Red (H) was determined using ImageJ. Error bars indicate the mean ± SEM shown. n ≥15 cells evaluated per condition. *P < 0.05, **P < 0.01, and ***P < 0.001, by unpaired, 2-tailed Student’s t test. P values were determined using Tukey’s method when correcting for multiple comparisons. Scale bars: 20 μm; magnification in (A) ×1.8. nutr, nutrient; YM, YM201636.