Read on Twitter
At long last, I get to share publication of a project (out today in @Nature) on which I started my lab at @UPMCHillmanCC and @PittTweet in 2014. In it, we describe the funky metabolism of regulatory T cells and how it is exploited in cancer. A thread: 1/ https://www.nature.com/articles/s41586-020-03045-2
Regulatory T cells are a critical component of healthy immunity but major barrier in many cancers. I spent my postdoc with @Vignali_Lab studying how these cells can be targeted for therapeutic benefit, and blockade of the neuropilin-1 receptor is in the clinic @AstellasUS. 2/
Due to my background with @J_Powell_Lab, I figured Tregs had a metabolism conducive to tumor residence. Great work from the likes of @JeffRathmell, @HolabUnil, and Ulf Beier and others suggested Treg cells have distinct metabolic needs. What does that mean in cancer? 3/
With a fledgling lab, I (and ultimately, first author Mac Watson #noTwitterMac) started pulsing tumor-infiltrating T cells with metabolic probes. The data were very striking, right off the bat: Treg cells do not like to take up glucose tracers. This did not change in cancer. 4/
What were the implications? While @scharpingne and the rest of the crew have shown conventional T cells are more dysfunctional in more metabolic tumors, using miniaturized suppression assays, Mac showed the more metabolically active the tumor, the MORE suppressive a Treg cell. 5/
As glucose tracers stain live cells, we sorted Treg cells based on their ability to take up the tracer, showing glucose avid Treg cells are poorer suppressors. RNAseq analysis (thanks @poholeklab) showed these cells were STILL Tregs but harbored a less suppressive signature. 6/
With @thehandiestlab and @aeoveracre, we transferred glucose avid Treg cells into RAG KO mice, showing they eventually are unable to control colitis. Glucose uptake defines unstable, less suppressive Tregs. Even culture of in high glucose conditions made them less suppressive. 7/
So what does all this mean? If Treg cells didn’t take up glucose, what were they eating? The RNAseq told us some clues: we didn’t really see an upregulation of lipid metabolism, and glycolysis genes were unchanged (surprising for cells that weren’t doing glycolysis). 8/
Turns out, Treg cells upregulate the expression of Slc16a1 (MCT1), Ldha, and Ldhb, genes that are involved in the uptake and metabolism of lactic acid, a byproduct of glucose metabolism at extremely high concentrations in tumor microenvironments. 9/
Lactate has long been known as immunosuppressive, and indeed conventional T cells are hindered by lactate. However, Treg cells are unphased by culture in lactate rich conditions. Further, lactate culture could prevent the destabilizing effects of high glucose! 10/
What does lactate do? Time for real metabolomics! We fed Tconv and Treg cells 13C-lactate, and found out that it doesn’t just enter the mitochondria to generate fuel, but actually LEAVES the mitochondria (as OAA) and forms higher order glycolytic intermediates like PEP. 11/
This was seemed like real gluconeogenesis: PEPCK inhibition reduced accumulation of glycolytic intermediates from lactate. It also dramatically slowed down Treg proliferation. This suggested lactate was being used as a fuel source and a source of carbon for biosynthesis. 12/
What does this mean in vivo? Is lactate a required fuel source for Treg cells, and what does it mean in the tumor? We generated a Treg-conditional knockout of the lactate transporter, in collaboration with Jeff Rothstein at @JohnsHopkins, who made the Slc16a1 floxed line. 13/
This mouse is completely healthy: no autoimmunity, lives a long happy mouse life. And when you take Treg cells from the periphery of these mice, they suppress just fine in culture. So lactic acid uptake was not required for Treg cell function in general. 14/
But when these Treg conditional MCT1 KO mice are inoculated with tumors, they grow significantly more slowly, and Treg cells sorted from the tumors fail to suppress. What’s more, deleting MCT1 in Treg cells synergized beautifully with anti-PD1 based immunotherapy. 15/
Our data suggest a metabolic symbiosis between cancer and tolerogenic cells like Treg cells. Cancer evades immunity both by starving infiltrating anti-tumor immunity and feeding pro-tumor cells like Treg cells (and, as @RMedzhitov showed in 2014, pro-tumor macrophages). 16/
For more about how tumor glycolysis, immunotherapy, and Treg cell activity are linked, check out a fantastic companion article also published today from @RZappasodi, @wolchokj, @merghout which we played a small role in as well. https://www.nature.com/articles/s41586-021-03326-4 17/
This project was truly a team effort stretching over several years. Mac took the reins back in 2016, but received much help from @pdaVignali, Steven, Ronal, and Ashley. Collaborations from @Vignali_Lab for T1D, @thehandiestlab for colitis, and @poholeklab for transcriptomics. 18/
Finally, this project was initially supported by @UPMCHillmanCC start-up funds and the Sidney Kimmel Foundation, and later by an @NIH_CommonFund New Innovator Award, @TheMarkFdn, the @CancerResearch Institute, and RNAseq via an award from @IOYIForum. 19/
We hope that understanding how tumor microenvironment metabolism inhibits some cells while promoting others, we may design #immunometabolism targeting strategies to improve #immunotherapy for cancer! 20/20
