A Metabolic Gene Survey Pinpoints Fucosylation as a Key Pathway Underlying the Suppressive Function of Regulatory T Cells in Cancer.

Forkhead box P3 (Foxp3)-expressing regulatory T cells (Treg) are the guardians of controlled immune reactions and prevent the development of autoimmune diseases. However, in the tumor context, their increased number suppresses antitumor immune responses, indicating the importance of understanding the mechanisms behind their function and stability. Metabolic reprogramming can affect Foxp3 regulation and, therefore, Treg suppressive function and fitness. Here, we performed a metabolic CRISPR/Cas9 screen and pinpointed novel candidate positive and negative metabolic regulators of Foxp3. Among the positive regulators, we revealed that targeting the GDP-fucose transporter Slc35c1, and more broadly fucosylation (Fuco), in Tregs compromises their proliferation and suppressive function both in vitro and in vivo, leading to alteration of the tumor microenvironment and impaired tumor progression and protumoral immune responses. Pharmacologic inhibition of Fuco dampened tumor immunosuppression mostly by targeting Tregs, thus resulting in reduced tumor growth. In order to substantiate these findings in humans, tumoral Tregs from patients with colorectal cancer were clustered on the basis of the expression of Fuco-related genes. FucoLOW Tregs were found to exhibit a more immunogenic profile compared with FucoHIGH Tregs. Furthermore, an enrichment of a FucoLOW signature, mainly derived from Tregs, correlated with better prognosis and response to immune checkpoint blockade in melanoma patients. In conclusion, Slc35c1-dependent Fuco is able to regulate the suppressive function of Tregs, and measuring its expression in Tregs might pave the way towards a useful biomarker model for patients with cancer. See related Spotlight by Silveria and DuPage, p. 1570.

Recent Advancements in Regenerative Approaches for Thymus Rejuvenation.

The thymus plays a key role in adaptive immunity by generating a diverse population of T cells that defend the body against pathogens. Various factors from disease and toxic insults contribute to the degeneration of the thymus resulting in a fewer output of T cells. Consequently, the body is prone to a wide host of diseases and infections. In this review, first, the relevance of the thymus is discussed, followed by thymic embryological organogenesis and anatomy as well as the development and functionality of T cells. Attempts to regenerate the thymus include in vitro methods, such as forming thymic organoids aided by biofabrication techniques that are transplantable. Ex vivo methods that have shown promise in enhancing thymic regeneration are also discussed. Current regenerative technologies have not yet matched the complexity and functionality of the thymus. Therefore, emerging techniques that have shown promise and the challenges that lie ahead are explored.