Dong, Haidong

Abstract Cytotoxic CD8+ T cells (CTL) are a crucial component of the immune system notable for their ability to eliminate rapidly proliferating malignant cells. However, the T-cell intrinsic factors required for human CTLs to accomplish highly efficient antitumor cytotoxicity are not well defined. By evaluating human CD8+ T cells from responders versus nonresponders to treatment with immune checkpoint inhibitors, we sought to identify key factors associated with effective CTL function. Single-cell RNA-sequencing analysis of peripheral CD8+ T cells from patients treated with anti–PD-1 therapy showed that cells from nonresponders exhibited decreased expression of the cytolytic granule-associated molecule natural killer cell granule protein-7 (NKG7). Functional assays revealed that reduced NKG7 expression altered cytolytic granule number, trafficking, and calcium release, resulting in decreased CD8+ T-cell–mediated killing of tumor cells. Transfection of T cells with NKG7 mRNA was sufficient to improve the tumor-cell killing ability of human T cells isolated from nonresponders and increase their response to anti–PD-1 or anti–PD-L1 therapy in vitro. NKG7 mRNA therapy also improved the antitumor activity of murine tumor antigen–specific CD8+ T cells in an in vivo model of adoptive cell therapy. Finally, we showed that the transcription factor ETS1 played a role in regulating NKG7 expression. Together, our results identify NKG7 as a necessary component for the cytotoxic function of CD8+ T cells and establish NKG7 as a T-cell–intrinsic therapeutic target for enhancing cancer immunotherapy. See related article by Li et al., p. 154.

Respiratory tissue resident–like CD8 + T cells are associated with chronic lung sequelae post-acute COVID-19.

Abstract Purpose: Outcomes for resistant metastatic castration-resistant prostate cancer (CRPC) are poor. Stereotactic ablative radiotherapy (SABR) induces antitumor immunity in clinical and preclinical studies, but immunologic biomarkers are lacking. Patients and Methods: Eighty-nine patients with oligometastatic CRPC were identified by 11C-Choline-PET (Choline-PET) from August 2016 to December 2019 and treated with SABR. Prespecified coprimary endpoints were 2-year overall survival (OS) and PSA progression. Secondary endpoints included 2-year SABR-treated local failure and 6-month adverse events. Correlative studies included peripheral blood T-cell subpopulations before and after SABR. Results: 128 lesions in 89 patients were included in this analysis. Median OS was 29.3 months, and 1- and 2-year OS were 96% and 80%, respectively. PSA PFS was 40% at 1 year and 21% at 2 years. Local PFS was 84.4% and 75.3% at 1 and 2 years, respectively, and no grade ≥3 AEs were observed. Baseline high levels of tumor-reactive T cells (TTR; CD8+CD11ahigh) predicted superior local, PSA, and distant PFS. Baseline high levels of effector memory T cells (TEM; CCR7−CD45RA−) were associated with improved PSA PFS. An increase in TTR at day 14 from baseline was associated with superior OS. Conclusions: This is the first comprehensive effector T-cell immunophenotype analysis in a phase II trial before and after SABR in CRPC. Results are favorable and support the incorporation of immune-based markers in the design of future randomized trials in patients with oligometastatic CRPC treated with SABR.

Abstract Many tumors exhibit increased incorporation of sialic acids into cell-surface glycans, which impact the tumor microenvironment. Sialic acid immunoglobulin-like lectins (Siglec) are receptors that recognize sialic acids and modulate immune responses, including responses to tumors. However, the roles of individual sialyltransferases in tumorigenesis and tumor growth are not well understood. Here, we examined the sialyltransferase ST8Sia6, which generated α2,8-linked disialic acids that bind to murine Siglec-E and human Siglec-7 and -9. Increased ST8Sia6 expression was found on many human tumors and associated with decreased survival in several cancers, including colon cancer. Because of this, we engineered MC38 and B16-F10 tumor lines to express ST8Sia6. ST8Sia6-expressing MC38 and B16-F10 tumors exhibited faster growth and led to decreased survival, which required host Siglec-E. ST8Sia6 expression on tumors also altered macrophage polarization toward M2, including upregulation of the immune modulator arginase, which also required Siglec-E. ST8Sia6 also accelerated tumorigenesis in a genetically engineered, spontaneous murine model of colon cancer, decreasing survival from approximately 6 months to 67 days. Thus, ST8Sia6 expression on tumors inhibits antitumor immune responses to accelerate tumor growth.

Although the immune checkpoint role of programmed death ligand 1 (PD-L1) has been established and targeted in cancer immunotherapy, the tumor-intrinsic role of PD-L1 is less appreciated in tumor biology and therapeutics development, partly because of the incomplete mechanistic understanding. Here we demonstrate a potentially novel mechanism by which PD-L1 promotes the epithelial-mesenchymal transition (EMT) in triple-negative breast cancer (TNBC) cells by suppressing the destruction of the EMT transcription factor Snail. PD-L1 directly binds to and inhibits the tyrosine phosphatase PTP1B, thus preserving p38-MAPK activity that phosphorylates and inhibits glycogen synthase kinase 3β (GSK3β). Via this mechanism, PD-L1 prevents the GSK3β-mediated phosphorylation, ubiquitination, and degradation of Snail and consequently promotes the EMT and metastatic potential of TNBC. Significantly, PD-L1 antibodies that confine the tumor-intrinsic PD-L1/Snail pathway restricted TNBC progression in immunodeficient mice. More importantly, targeting both tumor-intrinsic and tumor-extrinsic functions of PD-L1 showed strong synergistic tumor suppression effect in an immunocompetent TNBC mouse model. Our findings support that PD-L1 intrinsically facilitates TNBC progression by promoting the EMT, and this potentially novel PD-L1 signaling pathway could be targeted for better clinical management of PD-L1–overexpressing TNBCs.

Although immune checkpoint inhibitors have resulted in durable clinical benefits in a subset of patients with advanced cancer, some patients who did not respond to initial anti–PD-1 therapy have been found to benefit from the addition of salvage chemotherapy. However, the mechanism responsible for the successful chemoimmunotherapy is not completely understood. Here we show that a subset of circulating CD8 + T cells expressing the chemokine receptor CX3CR1 are able to withstand the toxicity of chemotherapy and are increased in patients with metastatic melanoma who responded to chemoimmunotherapy (paclitaxel and carboplatin plus PD-1 blockade). These CX3CR1 + CD8 + T cells have effector memory phenotypes and the ability to efflux chemotherapy drugs via the ABCB1 transporter. In line with clinical observation, our preclinical models identified an optimal sequencing of chemoimmunotherapy that resulted in an increase of CX3CR1 + CD8 + T cells. Taken together, we found a subset of PD-1 therapy–responsive CD8 + T cells that were capable of withstanding chemotherapy and executing tumor rejection with their unique abilities of drug efflux (ABCB1), cytolytic activity (granzyme B and perforin), and migration to and retention (CX3CR1 and CD11a) at tumor sites. Future strategies to monitor and increase the frequency of CX3CR1 + CD8 + T cells may help to design effective chemoimmunotherapy to overcome cancer resistance to immune checkpoint blockade therapy.

ProblemPregnancy requires balance between tolerance to the haploidentical fetus and the mother's ability to mount immune responses. There are parallels to this phenomenon that occur in metastatic cancer. We assessed soluble program death ligand‐1 soluble PD‐L1 (sPD‐L1) and galectin‐9 in the blood of pregnant women during gestation as these molecules are highly involved in immune suppression during cancer.Method of studyMaternal blood was collected from 30 primigravida women at monthly intervals during pregnancy, delivery and 6‐week post‐partum. Blood was analyzed for sPD‐L1 and galectin‐9 concentrations by ELISA. Term placentas were collected in formalin and IHC was completed for PD‐L1 and galectin‐9 expression.ResultsMaternal blood levels of sPD‐L1 (0.438 ng/mL) and galectin‐9 (1976 pg/mL) were elevated early in normal pregnancies compared to non‐pregnant controls (0.242 ng/mL and 773 pg/mL, respectively). sPD‐L1 increased throughout gestation, whereas galectin‐9 remained elevated until parturition; both proteins returned to control levels post‐partum. Women carrying male fetuses had significantly higher galectin‐9 levels, but not sPD‐L1, than those carrying females (2263 pg/mL vs 1874 pg/mL; P = .0005). Trophoblast cells of the term placenta coexpress galectin‐9 and PD‐L1.ConclusionImmune‐regulatory molecules galectin‐9 and sPD‐L1 increased during pregnancy and may play a role in immune tolerance that is critical for the fetus.

Immune checkpoint therapy with PD-1 blockade has emerged as an effective therapy for many advanced cancers; however, only a small fraction of patients achieve durable responses. To date, there is no validated blood-based means of predicting the response to PD-1 blockade. We report that Bim is a downstream signaling molecule of the PD-1 pathway, and its detection in T cells is significantly associated with expression of PD-1 and effector T cell markers. High levels of Bim in circulating tumor-reactive (PD-1 + CD11a hi CD8 + ) T cells were prognostic of poor survival in patients with metastatic melanoma who did not receive anti–PD-1 therapy and were also predictive of clinical benefit in patients with metastatic melanoma who were treated with anti–PD-1 therapy. Moreover, this circulating tumor-reactive T cell population significantly decreased after successful anti–PD-1 therapy. Our study supports a crucial role of Bim in both T cell activation and apoptosis as regulated by PD-1 and PD-L1 interactions in effector CD8 + T cells. Measurement of Bim levels in circulating T cells of patients with cancer may provide a less invasive strategy to predict and monitor responses to anti–PD-1 therapy, although future prospective analyses are needed to validate its utility.