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Five-year survival for human papilloma virus-unrelated head and neck squamous cell carcinomas remain below 50%. We assessed the safety of administering combination hypofractionated stereotactic body radiation therapy with single-dose durvalumab (anti-PD-L1) neoadjuvantly (n = 21) (NCT03635164). The primary endpoint of the study was safety, which was met. Secondary endpoints included radiographic, pathologic and objective response; locoregional control; progression-free survival; and overall survival. Among evaluable patients at an early median follow-up of 16 months (448 d or 64 weeks), overall survival was 80.1% with 95% confidence interval (95% CI) (62.0%, 100.0%), locoregional control and progression-free survival were 75.8% with 95% CI (57.5%, 99.8%), and major pathological response or complete response was 75% with 95% exact CI (51.6%, 100.0%). For patients treated with 24 Gy, 89% with 95% CI (57.1%, 100.0%) had MPR or CR. Using high-dimensional multi-omics and spatial data as well as biological correlatives, we show that responders had: (1) an increase in effector T cells; (2) a decrease in immunosuppressive cells; and (3) an increase in antigen presentation post-treatment.

E-cadherin expression and Jak mutational status of LLC cells

Flow cytometry gating strategy for identifying Foxp3 expression in CD4+ T cells and PD-1, CD44, and CD69 on CD8+ T cells

Immune checkpoint inhibitors targeting the interaction between programmed cell death-1 (PD-1) and its ligand PD-L1 induce tumor regression in a subset of non–small cell lung cancer patients. However, clinical response rates are less than 25%. Evaluation of combinations of immunotherapy with existing therapies requires appropriate preclinical animal models. In this study, murine lung cancer cells (CMT167 and LLC) were implanted either orthotopically in the lung or subcutaneously in syngeneic mice, and response to anti–PD-1/PD-L1 therapy was determined. Anti–PD-1/PD-L1 therapy inhibited CMT167 orthotopic lung tumors by 95%. The same treatments inhibited CMT167 subcutaneous tumors by only 30% and LLC orthotopic lung tumors by 35%. CMT167 subcutaneous tumors had more Foxp3+ CD4+ T cells and fewer PD-1+ CD4+ T cells compared with CMT167 orthotopic tumors. Flow cytometric analysis also demonstrated increased abundance of PD-L1high cells in the tumor microenvironment in CMT167 tumor–bearing lungs compared with CMT167 subcutaneous tumors or LLC tumor–bearing lungs. Silencing PD-L1 expression in CMT167 cells resulted in smaller orthotopic tumors that remained sensitive to anti–PD-L1 therapy, whereas implantation of CMT167 cells into PD-L1− mice blocked orthotopic tumor growth, indicating a role for PD-L1 in both the cancer cell and the microenvironment. These findings indicate that the response of cancer cells to immunotherapy will be determined by both intrinsic properties of the cancer cells and specific interactions with the microenvironment. Experimental models that accurately recapitulate the lung tumor microenvironment are useful for evaluation of immunotherapeutic agents. Cancer Immunol Res; 5(9); 767–77. ©2017 AACR.

Flow cytometry gating strategy for identifying CD4+ and CD8+ T cells

Flow gating strategy for identification of PD-L1(high) cells in the TME

Flow cytometry gating strategy for recovery of lung cancer cells from tumor-bearing mice

Heatmap of cytokines that were expressed >5-fold higher in CMT167 cells in vivo compared to LLC cells in vivo

Silencing of PD-L1 in CMT167 cells using shRNA

Direct DNA sequencing chromatograms of Kras in CMT167, LLC, and LL/2 cells

Total number of CD4+T cells remain unchanged following Control-Fc and ephrin-B2-Fc (20 μg/ml) treatment of T cells (A). Correlation analysis was also performed between TGF-β and EFNB2, EphB4 on R2 analysis platform (B-C). Alterations of cell growth and survival markers in western blots performed using lysates of T cells treated with ephrin-B2-Fc and control-Fc (D). These samples were run on the same gel.

Supplementary Figure 6 (A) Survival curve comparing patients with high expression of FLT3, the FLT3LG receptor, to patients with low expression of FLT3 expression. (B) Survival curve comparing patients with high expression of FLT3LG to patients with low expression of FLT3LG.

Mice implanted with PDX tumors show significantly reduced uptake of supra-paramagnetic iron oxide nanoparticles (SPIO) in the combined sEphB4-HSA and RT group compared to the groups treated with RT alone or with sEphB4-HSA alone in DCE-MRI imaging (A-B). Delta T2 represents magnitude of decrease in T2 signal. One-way ANOVA was used to calculate the significance of the differences between groups. CIBERSORT analysis of a HNSCC TCGA dataset shows that patients with low M2:M1 ratio have improved overall survival (C) and disease-free survival (D). Analysis of HNSCC TCGA showing correlation between M2-related marker-HRH1 and ephrin-B2 (EFNB2) (E), EphB4 (F).

Immunofluorescence staining showing co-expression of EphB4 and pan-keratin in Ly2 tumors.

Supplementary Figure 5 (A) IL-15 amounts in serum of Balb/c mice treated with RT, anti-CD25, anti-asialoGM1 to deplete NK cells, and FLT3L; **** p{less than or equal to}0.0001; n=6. (B) Flow cytometric analysis of DCs MOC2 tumors after treatment with radiation therapy and anti-CD25; n=5. (C) growth curves of MOC2 tumors in individual mice treated with radiation therapy, anti-CD25, and anti-CD137.

IHC staining confirming expression of ephrin-B2 in areas stained with fibroblast-expressing α-Smooth muscle actin (α-SMA)

Blockade of EphB4-ephrin-B2 interaction combined with RT suppresses tumor growth in HNSCC tumors

This shows the efficiency of immuodepletion experiments

(A) ELISA assay measuring the concentration of TNYL-RAW-Fc protein in plasma 7 days after hydrodynamic injection of the TNYL-RAW-Fc plasmid. Data represent mean {plus minus} SD from measurements using different mice (n=2). (B) Inhibition of EphB4-ephrin-B2 signaling by TNYL-RAW-Fc does not affect immune cell populations in the circulation of Ly2 tumor-bearing mice.

The complement cascade is a part of the innate immune system that acts primarily to remove pathogens and injured cells. However, complement activation is also peculiarly associated with tumor progression. Here we report mechanistic insights into this association in multiple immunocompetent orthotopic models of lung cancer. After tumor engraftment, we observed systemic activation of the complement cascade as reflected by elevated levels of the key regulator C3a. Notably, growth of primary tumors and metastases was both strongly inhibited in C3-deficient mice (C3−/− mice), with tumors undetectable in many subjects. Growth inhibition was associated with increased numbers of IFNγ+/TNFα+/IL10+ CD4+ and CD8+ T cells. Immunodepletion of CD4+ but not CD8+ T cells in tumor-bearing subjects reversed the inhibitory effects of C3 deletion. Similarly, antagonists of the C3a or C5a receptors inhibited tumor growth. Investigations using multiple tumor cell lines in the orthotopic model suggested the involvement of a C3/C3 receptor autocrine signaling loop in regulating tumor growth. Overall, our findings offer functional evidence that complement activation serves as a critical immunomodulator in lung cancer progression, acting to drive immune escape via a C3/C5–dependent pathway.Significance: This provocative study suggests that inhibiting complement activation may heighten immunotherapeutic responses in lung cancer, offering findings with immediate implications, given the existing clinical availability of complement antagonists. Cancer Res; 78(1); 143–56. ©2017 AACR.

Supplementary Figure 3 (A) MOC2 tumor volumes of mice treated with RT, anti-CD25, and pLEV vehicle control (black line); RT, anti-CD25, and pLEV FLT3L plasmid (green line), and RT + anti-CD25 (red line). n=7. (B) Flow Cytometry analysis of CD8 T cell populations in MOC2 tumors and lymph nodes (LN) of C57 BL/6 mice. MOC2 tumors were harvested 3 days after RT, NK cell depletion and FLT3L therapy; n=6.

Purpose:Natural killer (NK) cells are type I innate lymphoid cells that are known for their role in killing virally infected cells or cancer cells through direct cytotoxicity. In addition to direct tumor cell killing, NK cells are known to play fundamental roles in the tumor microenvironment through secretion of key cytokines, such as FMS-like tyrosine kinase 3 ligand (FLT3L). Although radiotherapy is the mainstay treatment in most cancers, the role of radiotherapy on NK cells is not well characterized.Experimental Design:This study combines radiation, immunotherapies, genetic mouse models, and antibody depletion experiments to identify the role of NK cells in overcoming resistance to radiotherapy in orthotopic models of head and neck squamous cell carcinoma.Results:We have found that NK cells are a crucial component in the development of an antitumor response, as depleting them removes efficacy of the previously successful combination treatment of radiotherapy, anti-CD25, and anti-CD137. However, in the absence of NK cells, the effect can be rescued through treatment with FLT3L. But neither radiotherapy with FLT3L therapy alone nor radiotherapy with anti-NKG2A yields any meaningful tumor growth delay. We also identify a role for IL2 in activating NK cells to secrete FLT3L. This activity, we show, is mediated through CD122, the intermediate affinity IL2 receptor, and can be targeted with anti-CD25 therapy.Conclusions:These findings highlight the complexity of using radio-immunotherapies to activate NK cells within the tumor microenvironment, and the importance of NK cells in activating dendritic cells for increased tumor surveillance.

qPCR analysis shows elevated expression of EphB4 on intratumoral macrophages harvested from Ly2 tumors compared to ephrin-B2.

Systemic depletion of CD8+ T cells results in increased tumor growth in Ly2 tumors treated with TNYL-RAW-Fc (A). Confirmation of CD8+ T cell depletion by flow cytometry (B). Student's t-test or one-way ANOVA was used to calculate the significance of the differences between the groups.

Supplementary Figure 1 (A) Flow cytometry analysis of NK cell population expression of NKG2A in MOC2 tumors 3 days after RT; n=3. (B). Flow cytometry analysis of NK cell populations in MOC2 tumors 3 days after RT and anti-NKG2A therapy; n=6. (C) Flow cytometry analysis of CD4 T cell populations in MOC2 tumors 3 days after RT, anti-NKG2A therapy and NK cell depletion with NK1.1 antibody; n=6. (D) MOC2 tumor volumes of C57BL/6 mice treated with RT and isotype control (red line), anti-CD137, anti-CD25, and anti-NKG2A (blue line), anti-CD17 and antiCD25 (black line); n=7.

These figures show experiments of tumor growth in Factor B-/- mice. They also show gating strategy for flow cytometry and changes in inflammatory cells. Data showing loss of CIITA in cancer cells alters the response to complement depletion.

Supplementary Figure 4 (A) Gating strategy used in flow cytometry analysis analyzing NK46+ CD3-NK cells, CD11c+ MHCII+ DCs, CD3+ CD4+ T cells, and CD3+ CD8+ T cells. (B) Flow cytometry analysis of NK cell populations in blood from WT C57BL/6 mice treated with RT, anti-CD25, and anti-CD137; n=4. (C) Flow cytometry of CD4 T cell populations in tumors from WT C57BL/6 mice treated with RT, anti-CD25, and anti-CD137 and from DEREG mice treated with RT, anti-CD25, antiCD137, and diphtheria toxin (DT); *p{less than or equal to}0.05, ** p{less than or equal to}0.01; n=6. (D) FLT3L present in serum of C57BL6 treated with radiation therapy, anti-CD25, and anti-CD137, and DEREG mice treated with radiation therapy, anti-CD25, anti-CD137, and diphtheria toxin (DT); ** p{less than or equal to}0.01; n=6

Supplementary Figure 2 (A) Flow cytometry analysis of LY2 tumors analyzing DC populations; n=6. (B) Analysis of FLT3L present in the serum of LY2 bearing mice treated with radiation therapy and isotype antibodies, radiation therapy and anti-CD25 antibody, radiation therapy and anti-CD25 antibody and anti-asialoGM1 antibody to deplete NK cells, and radiation therapy, anti-CD25 antibody, anti-asialoGM1 antibody to deplete NK cells, and FLT3L therapy; n=5.

Purpose:Natural killer (NK) cells are type I innate lymphoid cells that are known for their role in killing virally infected cells or cancer cells through direct cytotoxicity. In addition to direct tumor cell killing, NK cells are known to play fundamental roles in the tumor microenvironment through secretion of key cytokines, such as FMS-like tyrosine kinase 3 ligand (FLT3L). Although radiotherapy is the mainstay treatment in most cancers, the role of radiotherapy on NK cells is not well characterized.Experimental Design:This study combines radiation, immunotherapies, genetic mouse models, and antibody depletion experiments to identify the role of NK cells in overcoming resistance to radiotherapy in orthotopic models of head and neck squamous cell carcinoma.Results:We have found that NK cells are a crucial component in the development of an antitumor response, as depleting them removes efficacy of the previously successful combination treatment of radiotherapy, anti-CD25, and anti-CD137. However, in the absence of NK cells, the effect can be rescued through treatment with FLT3L. But neither radiotherapy with FLT3L therapy alone nor radiotherapy with anti-NKG2A yields any meaningful tumor growth delay. We also identify a role for IL2 in activating NK cells to secrete FLT3L. This activity, we show, is mediated through CD122, the intermediate affinity IL2 receptor, and can be targeted with anti-CD25 therapy.Conclusions:These findings highlight the complexity of using radio-immunotherapies to activate NK cells within the tumor microenvironment, and the importance of NK cells in activating dendritic cells for increased tumor surveillance.

Lung cancers bearing oncogenically-mutated EGFR represent a significant fraction of lung adenocarcinomas (LUADs) for which EGFR-targeting tyrosine kinase inhibitors (TKIs) provide a highly effective therapeutic approach. However, these lung cancers eventually acquire resistance and undergo progression within a characteristically broad treatment duration range. Our previous study of EGFR mutant lung cancer biopsies highlighted the positive association of a TKI-induced interferon γ transcriptional response with increased time to treatment progression. To test the hypothesis that host immunity contributes to the TKI response, we developed novel genetically-engineered mouse models of EGFR mutant lung cancer bearing exon 19 deletions (del19) or the L860R missense mutation. Both oncogenic EGFR mouse models developed multifocal LUADs from which transplantable cancer cell lines sensitive to the EGFR-specific TKIs, gefitinib and osimertinib, were derived. When propagated orthotopically in the left lungs of syngeneic C57BL/6 mice, deep and durable shrinkage of the cell line-derived tumors was observed in response to daily treatment with osimertinib. By contrast, orthotopic tumors propagated in immune deficientnu/numice exhibited modest tumor shrinkage followed by rapid progression on continuous osimertinib treatment. Importantly, osimertinib treatment significantly increased intratumoral CD3+ T cell content relative to diluent treatment. The findings provide strong evidence supporting the requirement for adaptive immunity in the durable therapeutic control of EGFR mutant lung cancer.

Gammaherpesvirus (γHV) non-coding RNAs (ncRNAs) are integral modulators of viral infection. The γHVs engage RNA polymerase III (pol III)-dependent transcription of both host and viral ncRNAs, which contribute to viral establishment, gene expression, and pathogenesis. Viral ncRNAs, such as the EBV-encoded RNAs (EBERs), reportedly interact with multiple host RNA-binding proteins (RBPs) and contribute to inflammatory responses implicated in the development of malignancies. Here, we examined RBP interactions of the pol III-transcribed tRNA-miRNA encoded non-coding RNAs (TMERs) of murine γHV68, and the potential contributions of these and the related EBERs to in vivo pathogenesis. Using sequential enzymatic treatments, we found that several TMER1 forms retain a 5’-triphosphate, lending the possibility of recognition by the innate immune sensor RIG-I. We further examined the interactions of TMERs and EBERs with host RBPs, and found that multiple TMERs and EBERs interact with the La protein, though minimal interaction was detected with RIG-I during primary virus infection. Finally, we investigated the contributions of the TMERs and EBERs to disease in an immune-compromised mouse model with a series of viral recombinants. We found that expression of multiple single TMERs, or the EBERs expressed in place of the TMERs, was capable of restoring virulence to a viral recombinant lacking expression of all TMERs. Ultimately, these studies demonstrate that divergent pol III-transcribed γHV ncRNAs share interaction characteristics with two host RBPs and conserved contributions to disease, despite little to no significant sequence conservation. These findings support a model of convergent functions of the sequence-variable pol III-transcribed γHV ncRNAs.IMPORTANCEViruses manipulate the infected cell and host inflammatory responses through expression of coding and non-coding RNAs. The gammaherpesviruses are a subfamily of herpesviruses associated with chronic inflammatory diseases and malignancies, especially in immune-compromised individuals. Among these, the human Epstein-Barr virus and murine gammaherpesvirus 68 (γHV68) express highly abundant, RNA polymerase III-dependent, short non-coding RNAs. Whether these sequence-divergent ncRNAs have conserved functional properties is unknown. By using viral recombinants to allow direct comparison of these ncRNAs during primary infection, we find that the sequence-divergent ncRNAs of γHV68 and EBV share a conserved property to bind to the host RNA binding protein, La, and function interchangeably to facilitate in vivo pathogenesis. These studies demonstrate that abundant, RNA polymerase III-dependent viral ncRNAs can potently function to alter the host cell landscape and promote disease in a sequence-independent manner.

Autosomal dominant polycystic kidney disease (ADPKD), the most common monogenic nephropathy, is characterized by phenotypic variability exceeding genic effects. Dysregulated metabolism and immune cell function are key disease modulators. The tryptophan metabolites, kynurenines, produced through IDO1, are known immunomodulators. Here, we study the role of tryptophan metabolism in PKD using an orthologous disease model (C57Bl/6J Pkd1RC/RC). We found elevated kynurenine and IDO1 levels in Pkd1RC/RC kidneys versus wildtype. Further, IDO1 levels were increased in ADPKD cell lines and patient cyst cells. Genetic Ido1 loss in Pkd1RC/RC animals resulted in reduced PKD severity as measured by %kidney weight/body weight and cystic index. Consistent with a immunomodulatory role of kynurenines, Pkd1RC/RC;Ido1-/- mice presented with significant changes in the cystic immune microenvironment (CME) versus controls. Of note, kidney macrophage numbers decreased and CD8+ T cell numbers increased, both known PKD modulators. Also, pharmacological IDO1 inhibition using a tryptophan analog in Pkd1RC/RC animals resulted in less severe PKD versus controls with similar changes in the CME as in the genetic model. Together, our data suggest that tryptophan metabolism is dysregulated in ADPKD and that its inhibition results in changes to the CME and slows disease progression, making IDO1 a novel therapeutic target for ADPKD.

We have examined the response of memory CD4 T cells to tolerogenic signals. Although memory CD4 T cells could respond to antigen delivered without adjuvant, they undergo cell death upon further restimulation. Our data suggest that the Tcells die as a consequence of mitotic catastrophe that occurs when cells are unable to complete cell division., Summary Memory T cells respond rapidly in part because they are less reliant on a heightened levels of costimulatory molecules. This enables rapid control of secondary infecting pathogens but presents challenges to efforts to control or silence memory CD4 T cells, for example in antigen‐specific tolerance strategies for autoimmunity. We have examined the transcriptional and functional consequences of reactivating memory CD4 T cells in the absence of an adjuvant. We find that memory CD4 T cells generated by infection or immunisation survive secondary activation with antigen delivered without adjuvant, regardless of their location in secondary lymphoid organs or peripheral tissues. These cells were, however, functionally altered following a tertiary immunisation with antigen and adjuvant, proliferating poorly but maintaining their ability to produce inflammatory cytokines. Transcriptional and cell cycle analysis of these memory CD4 T cells suggests they are unable to commit fully to cell division potentially because of low expression of DNA repair enzymes. In contrast, these memory CD4 T cells could proliferate following tertiary reactivation by viral re‐infection. These data indicate that antigen‐specific tolerogenic strategies must examine multiple parameters of Tcell function, and provide insight into the molecular mechanisms that may lead to deletional tolerance of memory CD4 T cells.

Pancreatic ductal adenocarcinoma (PDAC) has a heterogeneous tumor microenvironment (TME) comprised of myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages, neutrophils, regulatory T cells, and myofibroblasts. The precise mechanisms that regulate the composition of the TME and how they contribute to radiotherapy (RT) response remain poorly understood. In this study, we analyze changes in immune cell populations and circulating chemokines in patient samples and animal models of pancreatic cancer to characterize the immune response to radiotherapy. Further, we identify STAT3 as a key mediator of immunosuppression post-RT. We found granulocytic MDSCs (G-MDSCs) and neutrophils to be increased in response to RT in murine and human PDAC samples. We also found that RT-induced STAT3 phosphorylation correlated with increased MDSC infiltration and proliferation. Targeting STAT3 using an anti-sense oligonucleotide in combination with RT circumvented RT-induced MDSC infiltration, enhanced the proportion of effector T cells, and improved response to RT. In addition, STAT3 inhibition contributed to the remodeling of the PDAC extracellular matrix when combined with RT, resulting in decreased collagen deposition and fibrotic tissue formation. Collectively, our data provide evidence that targeting STAT3 in combination with RT can mitigate the pro-tumorigenic effects of RT and improve tumor response.

Although the consequences of splenectomy are well understood in mice, much less is known about the immunologic changes that occur following splenectomy in humans. We sought to characterize the circulating immune cell populations of patients before and after elective splenectomy to determine if these changes are related to postsplenectomy survival outcomes. Retrospective clinical information was collected from 95 patients undergoing elective splenectomy compared with 91 patients undergoing pancreaticoduodenectomy (Whipple procedure). We further analyzed peripheral blood from five patients in the splenectomy group, collected before and after surgery, using single-cell cytometry by time-of-flight mass spectrometry. We compared pre- and postsplenectomy data to characterize both the major and minor immune cell populations in significantly greater detail. Compared with patients undergoing a Whipple procedure, splenectomized patients had significant and long-lasting elevated counts of lymphocytes, monocytes, and basophils. Cytometry by time-of-flight mass spectroscopy analysis demonstrated that the elevated lymphocytes primarily consisted of naive CD4+ T cells and a population of activated CD25+CD56+CD4+ T cells, whereas the elevated monocyte counts were mainly mature, activated monocytes. We also observed a significant increase in the expression of the chemokine receptors CCR6 and CCR4 on several cellular populations. Taken together, these data indicate that significant immunological changes take place following splenectomy. Whereas other groups have compared splenectomized patients to healthy controls, this study compared patients undergoing elective splenectomy to those undergoing a similar major abdominal surgery. Overall, we found that splenectomy results in significant long-lasting changes in circulating immune cell populations and function.

Innate and adaptive immune cells modulate Autosomal Dominant Polycystic Kidney Disease (ADPKD) severity, a common kidney disease with inadequate treatment options. ADPKD shares parallels with cancer where immune checkpoint inhibitors have been shown to reactivate CD8+ T cells and slow tumor growth. We have shown that, in PKD, CD8+ T cell loss worsens disease. This study used orthologous early-onset and adult-onset ADPKD models (Pkd1 p.R3277C) to evaluate the role of immune checkpoints in PKD. Flow cytometry of kidney cells showed increased levels of PD-1 on CD8+ T cells and PD-L1 on macrophages and epithelial cells in Pkd1RC/RC mice versus wildtypes, paralleling disease severity. PD-L1 was also upregulated in ADPKD human cells and patient kidney tissue versus controls. Genetic PD-L1 loss or treatment with an anti-PD-1 antibody did not impact PKD severity in early-onset or adult-onset ADPKD models. However, treatment with anti-PD-1 plus anti-CTLA-4, blocking two immune checkpoints, improved PKD outcomes in adult-onset ADPKD mice; neither monotherapy altered PKD. Combination therapy resulted in increased kidney CD8+ T cell numbers/activation and decreased kidney regulatory T cell numbers. Together, our data suggests that immune checkpoint activation is an important feature of and potential novel therapeutic target in ADPKD.

PurposeLung cancers bearing oncogenic EML4-ALK fusions respond to targeted tyrosine kinase inhibitors (TKIs; e.g. alectinib), with variation in the degree of shrinkage and duration of treatment (DOT). We previously demonstrated a positive association of a TKI-induced interferon gamma (IFNγ) transcriptional response with DOT in EGFR-mutant lung cancers. Herein, we used murine models of EML4-ALK lung cancer to test a role for host immunity in the therapeutic response to alectinib.Experimental DesignThree murine EML4-ALK cell lines (EA1, EA2, EA3) were implanted orthotopically into the lungs of immunocompetent and immunodeficient mice and treated with alectinib. Tumor volumes were serially measured by μCT. Immune cell content was measured by flow cytometry, multispectral immunofluorescence and CyTOF. Transcriptional responses to alectinib were assessed by RNAseq and secreted chemokines were measured by ELISA.ResultsAll cell lines were sensitive to alectinib in vitro. EA1 and EA3 tumors retained residual disease that rapidly progressed upon termination of treatment while EA2 tumors were eliminated by TKI treatment. Alectinib induced inflammatory transcriptional programs and multiple chemokines in all cell lines while untreated tumors exhibited distinct baseline chemokine expression patterns and content of CD8+ T cells and myeloid subsets. When propagated in immune-deficient mice, all three cell line-derived lung tumor models exhibited significant shrinkage followed by prompt progression despite continuous alectinib treatment.ConclusionsThe findings support an hypothesis that host and TKI-stimulated production of chemokines by tumor cells promotes functional engagement of adaptive immune cells within the tumor microenvironment that enhances the durability and depth of TKI response.Statement of Translational RelevancePatients with metastatic lung cancer harboring ALK fusions are treated with targeted tyrosine kinase inhibitors (TKI) in the first line setting. Despite bearing the same driver oncogene, patients experience a range of tumor burden reduction and variable amounts of residual disease. Residual disease burden associates with patient survival and contributes to the emergence of drug resistance yielding treatment failure. The factors mediating this differential response to TKI and residual disease are incompletely understood. Our group has developed a panel of murine ALK driven lung cancer cell lines that reproducibly show differences in the depth and duration of response when implanted into immunocompetent mice. Data using this model indicate that the presence of CD8+ T cells is a major contributor to the depth and duration of response. These models will be critical in developing rational combination therapies to augment the immune microenvironment engagement along with TKIs to improve outcomes for these patients.

Background Radioresistance represents a major problem in the treatment of head and neck cancer (HNC) patients. To improve response, understanding tumor microenvironmental factors that contribute to radiation resistance is important. Regulatory T cells (Tregs) are enriched in numerous cancers and can dampen the response to radiation by creating an immune-inhibitory microenvironment. The purpose of this study was to investigate mechanisms of Treg modulation by radiation in HNC. Methods We utilized an orthotopic mouse model of HNC. Anti-CD25 was used for Treg depletion. Image-guided radiation was delivered to a dose of 10 Gy. Flow cytometry was used to analyze abundance and function of intratumoral immune cells. Enzyme-linked immunosorbent assay was performed to assess secreted factors. For immune-modulating therapies, anti–PD-L1, anti-CTLA-4, and STAT3 antisense oligonucleotide (ASO) were used. All statistical tests were two-sided. Results Treatment with anti-CD25 and radiation led to tumor eradication (57.1%, n = 4 of 7 mice), enhanced T-cell cytotoxicity compared with RT alone (CD4 effector T cells [Teff]: RT group mean = 5.37 [ 0.58] vs RT + αCD25 group mean =10.71 [0.67], P = .005; CD8 Teff: RT group mean = 9.98 [0.81] vs RT + αCD25 group mean =16.88 [2.49], P = .01) and induced tumor antigen-specific memory response (100.0%, n = 4 mice). In contrast, radiation alone or when combined with anti-CTLA4 did not lead to durable tumor control (0.0%, n = 7 mice). STAT3 inhibition in combination with radiation, but not as a single agent, improved tumor growth delay, decreased Tregs, myeloid-derived suppressor cells, and M2 macrophages and enhanced effector T cells and M1 macrophages. Experiments in nude mice inhibited the benefit of STAT3 ASO and radiation. Conclusion We propose that STAT3 inhibition is a viable and potent therapeutic target against Tregs. Our data support the design of clinical trials integrating STAT3 ASO in the standard of care for cancer patients receiving radiation.

Despite routine platinum-based chemotherapeutic use in cancer treatment, there remains a need to improve efficacy and patient selection. Using multi-omic assessment of cisplatin responsive and resistant human bladder cancer cell lines and whole-genome CRISPR screens, we identified NPEPPS, the puromycin-sensitive aminopeptidase as a novel driver of cisplatin resistance. Volume-regulated anion channels (VRACs) have been shown to directly import the majority of intracellular cisplatin. Here, we show that the mechanism of NPEPPS-mediated cisplatin resistance is by binding to VRACs and blocking the import of cisplatin into the cell. We show that NPEPPS depletion increased intracellular cisplatin and made cisplatin-resistant cells more responsive to cisplatin in vitro and in vivo. Overexpression of NPEPPS in cisplatin-sensitive cells decreased intracellular cisplatin and resulted in increased treatment resistance. The same results also hold for carboplatin. Our findings describe the first mechanism by which VRACs can be targeted to control the import of cisplatin and carboplatin.

Investigating the dynamics of virus-host interactions in vivo remains an important challenge, often limited by the ability to directly identify virally-infected cells. Here, we combine detection of a beta-lactamase activated fluorescent substrate with full spectrum flow cytometry to identify primary targets of murine gammaherpesvirus 68 (MHV68) infection in the peritoneal cavity. By optimizing substrate and detection conditions, we were able to achieve multiparameter characterization of infected cells and the ensuing host response. MHV68 infection leads to a pronounced increase in immune cells, with CD8+ T cells increasing by 3 days, and total infiltrate peaking around 8 days post-infection. MHV68 infection results in near elimination of large peritoneal macrophages by 8 days post-infection, and a concordant increase in small peritoneal macrophages and monocytes. Infection is associated with prolonged changes to myeloid cells, with a distinct population of MHC IIhigh large peritoneal macrophages emerging by 14 days. Targets of MHV68 infection could be readily detected. Between 1 to 3 days post-infection, MHV68 infects ~5-10% of peritoneal cells, with >75% being large peritoneal macrophages. By 8 days post-infection, the frequency of MHV68 infection is reduced at least 10-fold, with infection primarily in small peritoneal macrophages, with few infected dendritic cells and B cells. MHV68 infection at 3 days post-infection contains both lytic and latent infection, consistent with the identification of cells with active reporter gene expression. Our findings demonstrate the utility of the beta-lactamase MHV68 reporter system for high throughput single-cell analysis and identify dynamic changes during primary gammaherpesvirus infection.ImportanceIdentifying virally-infected cells in vivo is key to tracking viral infection and understanding host-pathogen interactions. The ability to further characterize and phenotype virally-infected cells is technically challenging. We use a mouse gammaherpesvirus, MHV68, expressing a reporter gene to identify infected cells during primary infection via flow cytometry. Optimization using this reporter system allowed us to further characterize infected cells via multiparameter full spectrum flow cytometry. Our study provides a technical model for high throughput single-cell immunophenotyping methods in the context of gammaherpesvirus infection. Furthermore, we show that acute MHV68 infection in the peritoneal cavity dramatically changes the immune landscape of this tissue, results in a high number of infected macrophages at early times, and is characterized by both lytic and latent infection within immune cells.