Researchers at the Institute for Systems Biology (ISB) and the University of California, Riverside say they have developed a novel technique that provides new insights into cancer biology by allowing researchers to show how fatty acids are absorbed by single cells.

The team published its study (“Single-Cell Profiling of Fatty Acid Uptake Using Surface-Immobilized Dendrimers”) in the Journal of the American Chemical Society.

Fatty acids, along with glucose and amino acids, are a major energy source for cellular growth and proliferation, and abnormal fatty acid metabolism is often seen in cancer. The labs of Wei Wei, PhD,  assistant professor at ISB, and Min Xue, PhD, assistant professor at UC Riverside, have been collaborating to develop a series of chemical probes and analytical approaches for quantifying cellular glucose uptake, lactate production, amino acid uptake, and other cancer-related metabolites.

Unlike glucose and amino acids, however, the mechanisms underlying the uptake of fatty acids into cells have been lesser known and difficult to discern. The technical tools for measuring fatty acid uptake at the single-cell level are extremely limited.

“We present a chemical approach to profile fatty acid uptake in single cells. We use azide-modified analogues to probe the fatty acid influx and surface-immobilized dendrimers with dibenzocyclooctyne (DBCO) groups for detection. A competition between the fatty acid probes and BHQ2-azide quencher molecules generates fluorescence signals in a concentration-dependent manner,” write the investigators.

“By integrating this method onto a microfluidics-based multiplex protein analysis platform, we resolved the relationships between fatty acid influx, oncogenic signaling activities, and cell proliferation in single glioblastoma cells. We found that p70S6K and 4EBP1 differentially correlated with fatty acid uptake. We validated that cotargeting p70S6K and fatty acid metabolism synergistically inhibited cell proliferation.

“Our work provided the first example of studying fatty acid metabolism in the context of protein signaling at single-cell resolution and generated new insights into cancer biology.”

“This work is the first example of profiling fatty acid uptake in conjunction with aberrant protein signaling in cancer cells at single-cell resolution and represents an important advance in the single-cell metabolic assay,” said  Wei Wei, co-corresponding author.

To profile the fatty acid uptake, the researchers chose a surrogate molecule that was structurally similar to natural fatty acids. This similarity tricked the cells into taking up these surrogates like the native ones. Then, using a unique dendrimer molecule, the scientists report that they achieved precise quantitation of those surrogates from single cells.

Applying this new single-cell tool to a brain cancer model, the researchers identified that fatty acid uptake was differentially regulated by two downstream effectors of the Mammalian Target of Rapamycin (mTOR), a critical regulator of cell proliferation and protein synthesis. The results revealed a compensatory activation of fatty acid metabolism upon oncogene inhibition or attenuation of glucose metabolism in these brain cancer cells and uncovered a novel combination therapy that targets this bioenergetic flexibility to synergistically block the tumor growth.

“This novel tool opens new avenues for studying how fatty acid metabolism affects biological systems. It has also inspired us to develop more metabolic probes for single-cell analysis,” noted Min Xue, co-corresponding author on the paper.

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