Politics and health care spending in the United States: A case study from the passage of the 2003 Medicare Modernization Act.

This paper analyzes the interplay between congressional politics, the actions of the executive branch, and hospitals' regulated Medicare payments. We focus on the 2003 Medicare Modernization Act (MMA) and analyze a provision in the law - Section 508 - that raised certain hospitals' regulated payments. We show, via our analysis of the Section 508 program, that Medicare payments are malleable and can be influenced by political dynamics. In the cross-section, hospitals represented by members of Congress who voted "yea" on the MMA were more likely to receive Section 508 payment increases. We interviewed the Secretary of Health and Human Services who oversaw the MMA, and he described how these payment increases were designed to win support for the law. The Section 508 payment increases raised hospitals' activity and spending. Members of Congress representing recipient hospitals received increased campaign contributions after the Section 508 payment increases were extended. Ultimately, our analysis highlights how Medicare payment increases can serve as an appealing tool for legislative leaders working to win votes for wider pieces of legislation.

CD8+ T cells sustain antitumor response by mediating crosstalk between adenosine A2A receptor and glutathione/GPX4.

Antitumor responses of CD8+ T cells are tightly regulated by distinct metabolic fitness. High levels of glutathione (GSH) are observed in the majority of tumors, contributing to cancer progression and treatment resistance in part by preventing glutathione peroxidase 4-dependent (GPX4-dependent) ferroptosis. Here, we show the necessity of adenosine A2A receptor (A2AR) signaling and the GSH/GPX4 axis in orchestrating metabolic fitness and survival of functionally competent CD8+ T cells. Activated CD8+ T cells treated ex vivo with simultaneous inhibition of A2AR and lipid peroxidation acquire a superior capacity to proliferate and persist in vivo, demonstrating a translatable means to prevent ferroptosis in adoptive cell therapy. Additionally, we identify a particular cluster of intratumoral CD8+ T cells expressing a putative gene signature of GSH metabolism (GMGS) in association with clinical response and survival across several human cancers. Our study addresses a key role of GSH/GPX4 and adenosinergic pathways in fine-tuning the metabolic fitness of antitumor CD8+ T cells.

The Human Soluble NKG2D Ligand Differentially Impacts Tumorigenicity and Progression in Temporal and Model-Dependent Modes.

NKG2D is an activating receptor expressed by all human NK cells and CD8 T cells. Harnessing the NKG2D/NKG2D ligand axis has emerged as a viable avenue for cancer immunotherapy. However, there is a long-standing controversy over whether soluble NKG2D ligands are immunosuppressive or immunostimulatory, originating from conflicting data generated from different scopes of pre-clinical investigations. Using multiple pre-clinical tumor models, we demonstrated that the impact of the most characterized human solid tumor-associated soluble NKG2D ligand, the soluble MHC I chain-related molecule (sMIC), on tumorigenesis depended on the tumor model being studied and whether the tumor cells possessed stemness-like properties. We demonstrated that the potential of tumor formation or establishment depended upon tumor cell stem-like properties irrespective of tumor cells secreting the soluble NKG2D ligand sMIC. Specifically, tumor formation was delayed or failed if sMIC-expressing tumor cells expressed low stem-cell markers; tumor formation was rapid if sMIC-expressing tumor cells expressed high stem-like cell markers. However, once tumors were formed, overexpression of sMIC unequivocally suppressed tumoral NK and CD8 T cell immunity and facilitated tumor growth. Our study distinguished the differential impacts of soluble NKG2D ligands in tumor formation and tumor progression, cleared the outstanding controversy over soluble NKG2D ligands in modulating tumor immunity, and re-enforced the viability of targeting soluble NKG2D ligands for cancer immunotherapy for established tumors.

Identification and Characterization of a Novel Indoleamine 2,3-Dioxygenase 1 Protein Degrader for Glioblastoma.

Indoleamine 2,3-dioxygenase 1 (IDO1) is a potent immunosuppressive enzyme that inhibits the antitumor immune response through both tryptophan metabolism and non-enzymatic functions. To date, most IDO1-targeted approaches have focused on inhibiting tryptophan metabolism. However, this class of drugs has failed to improve the overall survival of patients with cancer. Here, we developed and characterized proteolysis targeting chimeras (PROTACs) that degrade the IDO1 protein. IDO1-PROTACs were tested for their effects on IDO1 enzyme and non-enzyme activities. After screening a library of IDO1-PROTAC derivatives, a compound was identified that potently degraded the IDO1 protein through cereblon-mediated proteasomal degradation. The IDO1-PROTAC: (i) inhibited IDO1 enzyme activity and IDO1-mediated NF-κB phosphorylation in cultured human glioblastoma (GBM) cells, (ii) degraded the IDO1 protein within intracranial brain tumors in vivo, and (iii) mediated a survival benefit in mice with well-established brain tumors. This study identified and characterized a new IDO1 protein degrader with therapeutic potential for patients with glioblastoma.

Direct N-Glycosylation Profiling of Urine and Prostatic Fluid Glycoproteins and Extracellular Vesicles.

Expressed prostatic secretions (EPS), also called post digital rectal exam urines, are proximal fluids of the prostate that are widely used for diagnostic and prognostic assays for prostate cancer. These fluids contain an abundant number of glycoproteins and extracellular vesicles secreted by the prostate gland, and the ability to detect changes in their N-glycans composition as a reflection of disease state represents potential new biomarker candidates. Methods to characterize these N-glycan constituents directly from clinical samples in a timely manner and with minimal sample processing requirements are not currently available. In this report, an approach is described to directly profile the N-glycan constituents of EPS urine samples, prostatic fluids and urine using imaging mass spectrometry for detection. An amine reactive slide is used to immobilize glycoproteins from a few microliters of spotted samples, followed by peptide N-glycosidase digestion. Over 100 N-glycan compositions can be detected with this method, and it works with urine, urine EPS, prostatic fluids, and urine EPS-derived extracellular vesicles. A comparison of the N-glycans detected from the fluids with tissue N-glycans from prostate cancer tissues was done, indicating a subset of N-glycans present in fluids derived from the gland lumens. The developed N-glycan profiling is amenable to analysis of larger clinical cohorts and adaptable to other biofluids.

Tumor Cell IDO Enhances Immune Suppression and Decreases Survival Independent of Tryptophan Metabolism in Glioblastoma.

PURPOSE: Glioblastoma (GBM) is an incurable primary brain tumor that has not benefited from immunotherapy to date. More than 90% of GBM expresses the tryptophan (Trp) metabolic enzyme, indoleamine 2,3-dioxygenase 1 (IDO). This observation supported the historical hypothesis that IDO suppresses the antitumor immune response solely through a mechanism that requires intratumoral Trp depletion. However, recent findings led us to investigate the alternative hypothesis that IDO suppresses the anti-GBM immune response independent of its association with Trp metabolism. EXPERIMENTAL DESIGN: IDO-deficient GBM cell lines reconstituted with IDO wild-type or IDO enzyme-null cDNA were created and validated in vitro and in vivo. Microarray analysis was conducted to search for genes that IDO regulates, followed by the analysis of human GBM cell lines, patient GBM and plasma, and The Cancer Genome Atlas (TCGA) database. Ex vivo cell coculture assays, syngeneic and humanized mouse GBM models, were used to test the alternative hypothesis. RESULTS: Nonenzymic tumor cell IDO activity decreased the survival of experimental animals and increased the expression of complement factor H (CFH) and its isoform, factor H like protein 1 (FHL-1) in human GBM. Tumor cell IDO increased CFH and FHL-1 expression independent of Trp metabolism. Increased intratumoral CFH and FHL-1 levels were associated with poorer survival among patients with glioma. Similar to IDO effects, GBM cell FHL-1 expression increased intratumoral regulatory T cells (Treg) and myeloid-derived suppressor cells while it decreased overall survival in mice with GBM. CONCLUSIONS: Our study reveals a nonmetabolic IDO-mediated enhancement of CFH expression and provides a new therapeutic target for patients with GBM.

Immune Responses Vary in Preinvasive Colorectal Lesions by Tumor Location and Histology.

Immune responses vary in colorectal cancers, which strongly influence prognosis. However, little is known about the variance in immune response within preinvasive lesions. The study aims to investigate how the immune contexture differs by clinicopathologic features (location, histology, dysplasia) associated with progression and recurrence in early carcinogenesis. We performed a cross-sectional study using preinvasive lesions from the surgical pathology laboratory at the Medical University of South Carolina. We stained the tissues with immunofluorescence antibodies, then scanned and analyzed expression using automated image analysis software. We stained CD117 as a marker of mast cells, CD4/RORC to indicate Th17 cells, MICA/B as a marker of NK-cell ligands, and also used antibodies directed against cytokines IL6, IL17A, and IFNγ. We used negative binomial regression analysis to compare analyte density counts by location, histology, degree of dysplasia adjusted for age, sex, race, and batch. All immune markers studied (except IL17a) had significantly higher density counts in the proximal colon than distal colon and rectum. Increases in villous histology were associated with significant decreases in immune responses for IL6, IL17a, NK ligand, and mast cells. No differences were observed in lesions with low- and high-grade dysplasia, except in mast cells. The lesions of the proximal colon were rich in immune infiltrate, paralleling the responses observed in normal mucosa and invasive disease. The diminishing immune response with increasing villous histology suggests an immunologically suppressive tumor environment. Our findings highlight the heterogeneity of the immune responses in preinvasive lesions, which may have implications for prevention strategies. PREVENTION RELEVANCE: Our study is focused on immune infiltrate expression in preinvasive colorectal lesions; our results suggest important differences by clinicopathologic features that have implications for immune prevention research.

Tumor-derived NKG2D ligand sMIC reprograms NK cells to an inflammatory phenotype through CBM signalosome activation.

Natural Killer (NK) cell dysfunction is associated with poorer clinical outcome in cancer patients. What regulates NK cell dysfunction in tumor microenvironment is not well understood. Here, we demonstrate that the human tumor-derived NKG2D ligand soluble MIC (sMIC) reprograms NK cell to secrete pro-tumorigenic cytokines with diminished cytotoxicity and polyfunctional potential. Antibody clearing sMIC restores NK cell to a normal cytotoxic effector functional state. We discovered that sMIC selectively activates the CBM-signalosome inflammatory pathways in NK cells. Conversely, tumor cell membrane-bound MIC (mMIC) stimulates NK cell cytotoxicity through activating PLC2γ2/SLP-76/Vav1 pathway. Ultimately, antibody targeting sMIC effectuated the in vivo anti-tumor effect of adoptively transferred NK cells. Our findings uncover an unrecognized mechanism that could instruct NK cell to a dysfunctional state in response to cues in the tumor microenvironment. Our findings provide a rationale for co-targeting sMIC to enhance the efficacy of the ongoing NK cell-based cancer immunotherapy.

Preinvasive Colorectal Lesions of African Americans Display an Immunosuppressive Signature Compared to Caucasian Americans.

BACKGROUND: African Americans (AAs) have higher colorectal cancer (CRC) incidence and mortality rate than Caucasian Americans (CAs). Recent studies suggest that immune responses within CRCs contribute to the disparities. If racially distinct immune signatures are present in the early phases of carcinogenesis, they could be used to develop interventions to prevent or slow disease. METHODS: We selected a convenience sample of 95 patients (48 CAs, 47 AAs) with preinvasive colorectal adenomas from the surgical pathology laboratory at the Medical University of South Carolina. Using immunofluorescent-conjugated antibodies on tissue slides from the lesions, we quantified specific immune cell populations: mast cells (CD117+), Th17 cells (CD4+RORC+), and NK cell ligand (MICA/B) and inflammatory cytokines, including IL-6, IL-17A, and IFN-γ. We compared the mean density counts (MDCs) and density rate ratios (RR) and 95% CI of immune markers between AAs to CAs using negative binomial regression analysis. We adjusted our models for age, sex, clinicopathologic characteristics (histology, location, dysplasia), and batch. RESULTS: We observed no racial differences in age or sex at the baseline endoscopic exam. AAs compared to CAs had a higher prevalence of proximal adenomas (66% vs. 40%) and a lower prevalence of rectal adenomas (11% vs. 23%) (p =0.04) but no other differences in pathologic characteristics. In age, sex, and batch adjusted models, AAs vs. CAs had lower RRs for cells labeled with IFNγ (RR 0.50 (95% CI 0.32-0.81); p=0.004) and NK cell ligand (RR 0.67 (0.43-1.04); p=0.07). In models adjusted for age, sex, and clinicopathologic variables, AAs had reduced RRs relative to CAs for CD4 (p=0.02), NK cell ligands (p=0.01), Th17 (p=0.005), mast cells (p=0.04) and IFN-γ (p< 0.0001). CONCLUSIONS: Overall, the lower RRs in AAs vs. CAs suggests reduced effector response capacity and an immunosuppressive ('cold') tumor environment. Our results also highlight the importance of colonic location of adenoma in influencing these differences; the reduced immune responses in AAs relative to CAs may indicate impaired immune surveillance in early carcinogenesis. Future studies are needed to understand the role of risk factors (such as obesity) in influencing differences in immune responses by race.

Neutrophils Alter DNA Repair Landscape to Impact Survival and Shape Distinct Therapeutic Phenotypes of Colorectal Cancer.

BACKGROUND & AIMS: Tumor-infiltrating neutrophils (polymorphonuclear neutrophils [PMNs]) are a prominent feature of colorectal cancer (CRC), where they can promote cytotoxicity or exacerbate disease outcomes. We recently showed that in acute colon injury, PMNs can increase DNA double-strand break (DSB) burden and promote genomic instability via microRNA-dependent inhibition of homologous recombination (HR) repair. In this study, we aimed to establish whether in inflamed colon, neutrophils shape the DSB-repair responses to impact CRC progression and sensitivity/resistance to DNA-repair targeted therapy. METHODS: Human sporadic CRC biopsies, The Cancer Genome Atlas gene expression analyses, tumor xenografts, and murine CRC models, as well as small-molecule inhibition of key DSB-repair factors were leveraged to investigate changes in the DSB-repair landscape and identify unique CRC responses with/without tumor infiltration by PMNs. RESULTS: We reveal that neutrophils exert a functional dualism in cancer cells, driving temporal modulation of the DNA damage landscape and resolution of DSBs. PMNs were found to promote HR deficiency in low-grade CRC by miR-155-dependent downregulation of RAD51, thus attenuating tumor growth. However, neutrophil-mediated genotoxicity due to accumulation of DSBs led to the induction of non-homologous end-joining (NHEJ), allowing for survival and growth of advanced CRC. Our findings identified a PMN-induced HR-deficient CRC phenotype, featuring low RAD51 and low Ku70 levels, rendering it susceptible to synthetic lethality induced by clinically approved PARP1 inhibitor Olaparib. We further identified a distinct PMN-induced HR-deficient CRC phenotype, featuring high Ku70 and heightened NHEJ, which can be therapeutically targeted by specific inhibition of NHEJ. CONCLUSIONS: Our work delineates 2 mechanism-based translatable therapeutic interventions in sporadic CRC.

Plasma cells are enriched in localized prostate cancer in Black men and are associated with improved outcomes.

Black men die more often of prostate cancer yet, interestingly, may derive greater survival benefits from immune-based treatment with sipuleucel-T. Since no signatures of immune-responsiveness exist for prostate cancer, we explored race-based immune-profiles to identify vulnerabilities. Here we show in multiple independent cohorts comprised of over 1,300 patient samples annotated with either self-identified race or genetic ancestry, prostate tumors from Black men or men of African ancestry have increases in plasma cell infiltrate and augmented markers of NK cell activity and IgG expression. These findings are associated with improved recurrence-free survival following surgery and nominate plasma cells as drivers of prostate cancer immune-responsiveness.

Targeting CD73 to augment cancer immunotherapy.

CD73 (ecto-5'-nucleotidase) is a novel immunoinhibitory protein that plays a key role for tumor growth and metastasis. Its main function is to convert extracellular ATP to immunosuppressive adenosine in concert with CD39 in normal tissues to limit excessive immune response. However, tumors take advantage of the CD73-mediated adenosinergic mechanism to protect them from immune attack. In particular, inducible expression of CD73 along with other adenosinergic molecules on both cancer cells and host cells sustains immunosuppressive tumor microenvironment by affecting multiple aspects of the immune response. Owing to its multifaceted capacity to tumor promotion as an emerging immune checkpoint, CD73 is an ideal therapeutic target for cancer treatment especially in combination with conventional therapy and/or other immune checkpoint inhibitors. In this review, we will discuss the roles of CD73 on tumor and immune cells and will highlight the therapeutic value of CD73 for combination therapy.

Immunosuppressive IDO in Cancer: Mechanisms of Action, Animal Models, and Targeting Strategies.

Indoleamine 2, 3-dioxygenase 1 (IDO; IDO1; INDO) is a rate-limiting enzyme that metabolizes the essential amino acid, tryptophan, into downstream kynurenines. Canonically, the metabolic depletion of tryptophan and/or the accumulation of kynurenine is the mechanism that defines how immunosuppressive IDO inhibits immune cell effector functions and/or facilitates T cell death. Non-canonically, IDO also suppresses immunity through non-enzymic effects. Since IDO targeting compounds predominantly aim to inhibit metabolic activity as evidenced across the numerous clinical trials currently evaluating safety/efficacy in patients with cancer, in addition to the recent disappointment of IDO enzyme inhibitor therapy during the phase III ECHO-301 trial, the issue of IDO non-enzyme effects have come to the forefront of mechanistic and therapeutic consideration(s). Here, we review enzyme-dependent and -independent IDO-mediated immunosuppression as it primarily relates to glioblastoma (GBM); the most common and aggressive primary brain tumor in adults. Our group's recent discovery that IDO levels increase in the brain parenchyma during advanced age and regardless of whether GBM is present, highlights an immunosuppressive synergy between aging-increased IDO activity in cells of the central nervous system that reside outside of the brain tumor but collaborate with GBM cell IDO activity inside of the tumor. Because of their potential value for the in vivo study of IDO, we also review current transgenic animal modeling systems while highlighting three new constructs recently created by our group. This work converges on the central premise that maximal immunotherapeutic efficacy in subjects with advanced cancer requires both IDO enzyme- and non-enzyme-neutralization, which is not adequately addressed by available IDO-targeting pharmacologic approaches at this time.

Antibody targeting tumor-derived soluble NKG2D ligand sMIC reprograms NK cell homeostatic survival and function and enhances melanoma response to PDL1 blockade therapy.

BACKGROUND: Melanoma patients who have detectable serum soluble NKG2D ligands either at the baseline or post-treatment of PD1/PDL1 blockade exhibit poor overall survival. Among families of soluble human NKG2D ligands, the soluble human MHC I chain-related molecule (sMIC) was found to be elevated in melanoma patients and mostly associated with poor response to PD1/PDL1 blockade therapy. METHODS: In this study, we aim to investigate whether co-targeting tumor-released sMIC enhances the therapeutic outcome of PD1/PDL1 blockade therapy for melanoma. We implanted sMIC-expressing B16F10 melanoma tumors into syngeneic host and evaluated therapeutic efficacy of anti-sMIC antibody and anti-PDL1 antibody combination therapy in comparison with monotherapy. We analyzed associated effector mechanism. We also assessed sMIC/MIC prevalence in metastatic human melanoma tumors. RESULTS: We found that the combination therapy of the anti-PDL1 antibody with an antibody targeting sMIC significantly improved animal survival as compared to monotherapies and that the effect of combination therapy depends significantly on NK cells. We show that combination therapy significantly increased IL-2Rα (CD25) on NK cells which sensitizes NK cells to low dose IL-2 for survival. We demonstrate that sMIC negatively reprograms gene expression related to NK cell homeostatic survival and proliferation and that antibody clearing sMIC reverses the effect of sMIC and reprograms NK cell for survival. We further show that sMIC/MIC is abundantly present in metastatic human melanoma tumors. CONCLUSIONS: Our findings provide a pre-clinical proof-of-concept and a new mechanistic understanding to underscore the significance of antibody targeting sMIC to improve therapeutic efficacy of anti-PD1/PDL1 antibody for MIC/sMIC+ metastatic melanoma patients.

Advanced Age Increases Immunosuppression in the Brain and Decreases Immunotherapeutic Efficacy in Subjects with Glioblastoma.

PURPOSE: Wild-type isocitrate dehydrogenase-expressing glioblastoma (GBM) is the most common and aggressive primary brain tumor with a median age at diagnosis of ≥65 years. It accounts for approximately 90% of all GBMs and has a median overall survival (OS) of <15 months. Although immune checkpoint blockade (ICB) therapy has achieved remarkable survival benefits in a variety of aggressive malignancies, similar success has yet to be achieved for GBM among phase III clinical trials to date. Our study aimed to understand the relationship between subject age and immunotherapeutic efficacy as it relates to survival from glioma. EXPERIMENTAL DESIGN: (i) Clinical data: GBM patient datasets from The Cancer Genome Atlas, Northwestern Medicine Enterprise Data Warehouse, and clinical studies evaluating ICB were stratified by age and compared for OS. (ii) Animal models: young, middle-aged, and older adult wild-type and indoleamine 2,3 dioxygenase (IDO)-knockout syngeneic mice were intracranially engrafted with CT-2A or GL261 glioma cell lines and treated with or without CTLA-4/PD-L1 mAbs, or radiation, anti-PD-1 mAb, and/or a pharmacologic IDO enzyme inhibitor. RESULTS: Advanced age was associated with decreased GBM patient survival regardless of treatment with ICB. The advanced age-associated increase of brain IDO expression was linked to the suppression of immunotherapeutic efficacy and was not reversed by IDO enzyme inhibitor treatment. CONCLUSIONS: Immunosuppression increases in the brain during advanced age and inhibits antiglioma immunity in older adults. Going forward, it will be important to fully understand the factors and mechanisms in the elderly brain that contribute to the decreased survival of older patients with GBM during treatment with ICB.

Association between inflammatory bowel disease and prostate cancer: A large-scale, prospective, population-based study.

Inflammatory bowel disease (IBD) is an established risk factor for colorectal cancer. Recent reports suggesting IBD is also a risk factor for prostate cancer (PC) require further investigation. We studied 218 084 men in the population-based UK Biobank cohort, aged 40 to 69 at study entry between 2006 and 2010, with follow-up through mid-2015. We assessed the association between IBD and subsequent PC using multivariable Cox regression analyses, adjusting for age at assessment, ethnic group, UK region, smoking status, alcohol drinking frequency, body mass index, Townsend Deprivation Index, family history of PC and previous prostate-specific antigen testing. Mean age at study entry was 56 years, 94% of the men were white, and 1.1% (n = 2311) had a diagnosis of IBD. After a median follow-up of 78 months, men with IBD had an increased risk of PC (adjusted hazard ratio [aHR] = 1.31, 95% confidence interval [CI] = 1.03-1.67, P = .029). The association with PC was only among men with the ulcerative colitis (UC; aHR = 1.47, 95% CI = 1.11-1.95, P = .0070), and not Crohn's disease (aHR 1.06, 95% CI = 0.63-1.80, P = .82). Results are limited by lack of data on frequency of health care interactions. In a large-scale, prospective cohort study, we detected an association between IBD, and UC specifically, with incident PC diagnosis.

Past, Current, and Future of Immunotherapies for Prostate Cancer.

Prostate cancer (PCa) is the most common cancer in men, and the second leading cause of cancer related death in men in Western countries. The standard therapy for metastatic PCa is androgen suppression therapy (AST). Men undergoing AST eventually develop metastatic castration-resistant prostate cancer (mCRPC), of which there are limited treatment options available. Immunotherapy has presented substantial benefits for many types of cancer, but only a marginal benefit for mCRPC, at least in part, due to the immunosuppressive tumor microenvironment (TME). Current clinical trials are investigating monotherapies or combination therapies involving adoptive cellular therapy, viral, DNA vaccines, oncolytic viruses, and immune checkpoint inhibitors (ICI). Immunotherapies are also being combined with chemotherapy, radiation, and AST. Additionally, preclinical investigations show promise with the recent description of alternative ways to circumvent the immunosuppressive nature of the prostate tumor microenvironment, including harnessing the immune stimulatory NKG2D pathway, inhibiting myeloid derived suppressor cells, and utilizing immunomodulatory oncolytic viruses. Herein we provide an overview of recent preclinical and clinical developments in cancer immunotherapies and discuss the perspectives for future immunotherapies in PCa.

NK Cell Plasticity in Cancer.

Natural killer (NK) cells are critical immune components in controlling tumor growth and dissemination. Given their innate capacity to eliminate tumor cells without prior sensitization, NK-based therapies for cancer are actively pursued pre-clinically and clinically. However, recent data suggest that tumors could induce functional alterations in NK cells, polarizing them to tumor-promoting phenotypes. The potential functional plasticity of NK cells in the context of tumors could lead to undesirable outcomes of NK-cell based therapies. In this review, we will summarize to-date evidence of tumor-associated NK cell plasticity and provide our insights for future investigations and therapy development.

Antibody targeting tumor-derived soluble NKG2D ligand sMIC provides dual co-stimulation of CD8 T cells and enables sMIC+ tumors respond to PD1/PD-L1 blockade therapy.

BACKGROUND: Insufficient co-stimulation accounts for a great deal of the suboptimal activation of cytotoxic CD8 T cells (CTLs) and presumably unsatisfactory clinical expectation of PD1/PD-L1 therapy. Tumor-derived soluble NKG2D ligands are associated with poor clinical response to PD1/PD-L1 blockade therapy in cancer patients. One of the mostly occurring tumor-derived soluble NKG2D ligands, the soluble MHC I chain related molecule (sMIC) can impair co-stimulation to CD8 T cells. We investigated whether co-targeting sMIC can provide optimal co-stimulation to CTLs and enhance the therapeutic effect of PD1/PD-L1 blockades. METHODS: Single agent therapy of a PD1/PD-L1 blockade antibody or a sMIC-targeting non-blocking antibody or a combination therapy of the two antibodies were implied to well-characterized pre-clinical MIC/sMIC+ tumor models that closely resemble the NKG2D-mediated oncoimmune dynamics of MIC+ cancer patients. Therapeutic efficacy and associated effector mechanisms were evaluated. RESULTS: We show that antibody co-targeting sMIC enables or enhances the response of sMIC+ tumors to PD1/PD-L1 blockade therapy. The therapy response of the combination therapy was associated with enhanced antigen-specific CD8 T cell enrichment and function in tumors. We show that co-targeting sMIC with a nonblocking antibody provides antigen-specific CD8 T cells with NKG2D and CD28 dual co-stimulation, in addition to elimination of inhibitory signals, and thus amplifies antigen-specific CD8 T cell anti-tumor responses. CONCLUSION: Our findings provide the proof-of-concept rationale and previously undiscovered mechanisms for co-targeting sMIC to enable and enhance the response to PD1/PD-L1 blockade therapy in sMIC+ cancer patients.

CD73: an emerging checkpoint for cancer immunotherapy.

CD73 is a novel immune checkpoint associated with adenosine metabolism that promotes tumor progression by suppressing antitumor immune response and promoting angiogenesis. The inhibition of CD73, in combination with immune checkpoint blockade, targeted therapy or conventional therapy, improves antitumor effects in numerous preclinical mouse models of cancer. Emerging evidence suggests that the combination of anti-CD73 and immune checkpoint blockade has promising clinical activity in patients with advanced solid tumors. In this review, we will discuss the specific role of CD73 on both tumor cells and nontumor cells in regulating tumor immunity and tumorigenesis and provide an update on the current view of the antitumor activity of targeting CD73 by mAb or small molecule selective inhibitors in preclinical and clinical settings.