The mRNA degradation factor Xrn1 regulates transcription elongation in parallel to Ccr4.

Co-transcriptional imprinting of mRNA by Rpb4 and Rpb7 subunits of RNA polymerase II (RNAPII) and by the Ccr4-Not complex conditions its post-transcriptional fate. In turn, mRNA degradation factors like Xrn1 are able to influence RNAPII-dependent transcription, making a feedback loop that contributes to mRNA homeostasis. In this work, we have used repressible yeast GAL genes to perform accurate measurements of transcription and mRNA degradation in a set of mutants. This genetic analysis uncovered a link from mRNA decay to transcription elongation. We combined this experimental approach with computational multi-agent modelling and tested different possibilities of Xrn1 and Ccr4 action in gene transcription. This double strategy brought us to conclude that both Xrn1-decaysome and Ccr4-Not regulate RNAPII elongation, and that they do it in parallel. We validated this conclusion measuring TFIIS genome-wide recruitment to elongating RNAPII. We found that xrn1Δ and ccr4Δ exhibited very different patterns of TFIIS versus RNAPII occupancy, which confirmed their distinct role in controlling transcription elongation. We also found that the relative influence of Xrn1 and Ccr4 is different in the genes encoding ribosomal proteins as compared to the rest of the genome.

CD8-Targeted IL2 Unleashes Tumor-Specific Immunity in Human Cancer Tissue by Reviving the Dysfunctional T-cell Pool.

Tumor-specific CD8+ T cells are key effectors of antitumor immunity but are often rendered dysfunctional in the tumor microenvironment. Immune-checkpoint blockade can restore antitumor T-cell function in some patients; however, most do not respond to this therapy, often despite T-cell infiltration in their tumors. We here explored a CD8-targeted IL2 fusion molecule (CD8-IL2) to selectively reactivate intratumoral CD8+ T cells in patient-derived tumor fragments. Treatment with CD8-IL2 broadly armed intratumoral CD8+ T cells with enhanced effector capacity, thereby specifically enabling reinvigoration of the dysfunctional T-cell pool to elicit potent immune activity. Notably, the revival of dysfunctional T cells to mediate effector activity by CD8-IL2 depended on simultaneous antigen recognition and was quantitatively and qualitatively superior to that achieved by PD-1 blockade. Finally, CD8-IL2 was able to functionally reinvigorate T cells in tumors resistant to anti-PD-1, underscoring its potential as a novel treatment strategy for patients with cancer. Significance: Reinvigorating T cells is crucial for response to checkpoint blockade therapy. However, emerging evidence suggests that the PD-1/PD-L1 axis is not the sole impediment for activating T cells within tumors. Selectively targeting cytokines toward specific T-cell subsets might overcome these barriers and stimulate T cells within resistant tumors. See related article by Moynihan et al., p. 1206 (32).

Dual Immune Checkpoint Blockade Induces Analogous Alterations in the Dysfunctional CD8+ T-cell and Activated Treg Compartment.

To dissect the effect of neoadjuvant PD-1 and CTLA4 blockade on intratumoral T cells in treatment-naive head and neck squamous cell carcinoma, we analyzed primary tumor immune infiltrates from responding and nonresponding patients. At baseline, a higher ratio between active (4-1BB/OX40+) and inactive regulatory CD4+ T cells was associated with immunotherapy response. Furthermore, upon therapy, this active regulatory T-cell (Treg) population showed a profound decrease in responding patients. In an analogous process, intratumoral dysfunctional CD8+ T cells displayed decreased expression of activity and dysfunction-related genes in responding patients, whereas in clinical nonresponders, natural killer cells showed an increased cytotoxic profile early upon treatment. These data reveal immunologic changes in response to dual PD-1/CTLA4 blockade, including a parallel remodeling of presumed tumor-reactive Treg and CD8+ T-cell compartments in responding patients, and indicate that the presence of activated Tregs at baseline may be associated with response. SIGNIFICANCE: In head and neck squamous cell carcinoma, neoadjuvant PD-1/CTLA4 blockade has shown substantial response rates (20%-35%). As recognition of tumor antigens by T cells appears to be a critical driver of therapy response, a better understanding of alterations in T-cell state that are associated with response and resistance is of importance. This article is featured in Selected Articles from This Issue, p. 2109.