We hypothesized that further increasing FOXO1 activity by overexpressing a nuclear-restricted version (FOXO1-3A) would result in even better activity. We were dead wrong! This variant seemingly locked CAR T cells into a memory state, which blunted their effector function. 8/
Most CAR T folks will tell you that in vivo activity is the most informative readout of potency. So how do FOXO1-OE CAR T cells stack up? FOXO1-OE dramatically enhanced CAR T expansion, persistence, and tumor control in liquid and solid tumor models. TCF1-OE was a bust. 9/
Mechanistic experiments showed that DNA binding, and therefore target gene expression, is required for FOXO1-OE memory reprogramming and function. Paradoxically, however, the beneficial effects of FOXO1-OE are independent of endogenous TCF7, a highly upregulated FOXO1 target. 10/
Why has FOXO1 flown under the radar for so long? We think it’s because FOXO1 activity is regulated post-translationally rather than transcriptionally, and is therefore veiled in RNA-seq data. Consistent with this notion, FOXO1 mRNA does not predict CAR T clinical responses. 11/
To approximate FOXO1 activity, we identified a FOXO1 “regulon” comprised of 41 genes that were up in FOXO1-OE and down in FOXO1 KO. The aggregate expression of these genes or FOXO1-OE signatures in pre-infusion CAR T cells or TIL correlated with positive clinical outcomes. 12/
In summary, memory programming (but not TOO much memory) is a great thing for CAR T! FOXO1 is critical for mediating CAR T function and FOXO1 overexpression represents a broadly-applicable approach to enhance CAR T antitumor activity. The jury is still out on TCF1/TCF7. 13/
Special shoutout to @paulbeavis4 and Phil Darcy, with whom we co-submitted our manuscript. Their exciting and complimentary findings can be read in their @Nature paper that is also now online. 14/ nature.com/articles/s4158…
This study would not have been possible without the GOAT, Crystal Mackall, and @MackallLab (especially @molecular_elena), who supported this project in its infancy prior to my transition-to-independence, and who were critical collaborators through its completion. 15/
As with all science, this work was driven by motived and supremely talented trainees (especially @alexdoan96 @kpmueller1 @andy_yhchen, and others in my lab). There are too many to individually name, but all of them inspire me to be my very best. I am as lucky as they come. 16/
Of note, this paper is the result of a truly collaborative, multi-lab effort. Special thanks to @Satpathology @JoeFraietta @GruppSteve @cdktmw for enabling this work and helping increase its impact. 17/
Finally, a big THANK YOU to our funders @parkerici @TheVFoundation, who believed in this idea before anyone else would. I am eternally grateful for your support and your forward-thinking vision for advancing cancer immunotherapy in the lab and in patients. 18/
I would be remiss if I didn't thank our anonymous reviewers and our editor @Nature, @mvicaracal. The review process worked as it should, and resulted in a higher-quality and more impactful paper.
@EvanWeberPhD @parkerici Thank you for your work! You are changing the future. ❤️