Single-cell profiling of tumor infiltrating T cells

Immune checkpoint blockade has shown tremendous anti-tumor potential in the clinic. However, these therapies are only effective in a subset of patients, so identification of additional immunomodulatory molecules that enhance the anti-tumor activity of these treatments may expand their clinical utility. In particular, identifying small molecules that complement existing immunotherapies has been relatively unexplored, so we performed a small molecule screen to identify compounds that can enhance co-inhibitory molecule blockade, to improve the anti-tumor adaptive immune response. Our unbiased screen identified inhibitors of cyclin-dependent kinase 4 and 6 (CDK4/6), including the FDA-approved palbociclib, as a class of small molecule compounds that exhibited significant immunostimulatory activity in vitro. In accordance with our in vitro finding of enhanced NFAT signaling, single-cell RNA-sequencing confirmed that in vivo exposure to CDK4/6 inhibitors enhanced NFAT signaling in tumor infiltrating T cells. Moreover, our results revealed that CDK4/6 inhibition up-regulated activation molecules and down-regulated suppressive molecules in these cells. CDK4/6 inhibition also increased the number of T cells with activated TCR (T cell receptor) signaling, as well as factors that are important for signal transduction downstream of TCR signaling. In summary, the impact of CDK4/6i on cell cycle progression and T cell proliferation are balanced favorably towards increased T cell recruitment and enhanced effector cell function, mediated in part by activation of the NFAT family of transcription factors. Further, our results demonstrate that CDK4/6i enhances PD-1 blockade through increased T-cell effector function and inhibition of immune suppressive cytokine production. While prolonged CDK4/6i treatment could be immunosuppressive due to adverse effects on lymphocyte proliferation, properly timed/sequenced CDK4/6i may potentiate the clinical impact of anti-PD-1/PD-L1 antibodies. As palbociclib is FDA-approved and multiple other CDK4/6 inhibitors are in clinical trials, we expect that this hypothesis will undergo rapid testing in humans. Overall design: Single-cell comparison of control and CDK4/6 inhibitor treated tumor infiltrating T cells

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Deng J, Wang ES, Jenkins RW, Li S, Dries R, Yates K, Chhabra S, Huang W, Liu H, Aref AR, Ivanova E, Paweletz CP, Bowden M, Zhou CW, Herter-Sprie GS, Sorrentino JA, Bisi JE, Lizotte PH, Merlino AA, Quinn MM, Bufe LE, Yang A, Zhang Y, Zhang H, Gao P, Chen T, Cavanaugh ME, Rode AJ, Haines E, Roberts PJ, Strum JC, Richards WG, Lorch JH, Parangi S, Gunda V, Boland GM, Bueno R, Palakurthi S, Freeman GJ, Ritz J, Haining WN, Sharpless NE, Arthanari H, Shapiro GI, Barbie DA, Gray NS, Wong KK