Knutson, Keith L.

Abstract Markers of immune related adverse events and response in patients treated with immune checkpoint inhibitors (ICI) may shed light into ICI resistance, T cell exhaustion and other combinatorial therapies. The elevated levels of these biomarkers have potential to predict if PD-1 or PD-1/CTLA-4 antagonist combination will be effective in a certain Melanoma patient. Therefore, it may potentially guide healthcare providers to change treatment plans. In this study, the ICI treatments we focused on were PD-1 or combination of PD-1/CTLA-4 blockades. The measurement of the biomarkers was conducted at Mayo Clinic, from serum samples obtained in 2 time points, pre-treatments and 2–3 months after the first ICI treatments. Validated IVD kits were used per manufacture’s instruction. Biomarkers could be measured using stored frozen serum samples according to the instructions on how the biomarkers will be measured. We investigated 13 biomarkers in the sera of 76 melanoma patients who received immune checkpoint therapies. The biomarkers tested were, Human ELAFIN ELISA, Human IL-18 ELISA, Reg3α + Universal kit, Anti-Nuclear Antibody Test System, FLUORO AID-1 Test for anti-mitochondrial antibodies, anti-smooth muscle antibodies and anti-parietal cell antibodies, Anti-MDA5 ELISA Kit, Anti-synthetase ELISA Skin, Antineutrophil cytoplasmic antibodies MPO-ANCA ELISA, Antineutrophil cytoplasmic antibodies PR3-ANCA ELISA, Dsg1, Dsg3 ELISA, BP180, BP230, type-VII collagen. When compared with the samples obtained before treatments, IL-18 levels significantly elevated (p value < 0.0001) in post treatment samples of non-responders. Further studies are needed to confirm if elevated IL-18 contribute to the biology of resistance to ICI therapies. Supported by MBLI

Abstract Dendritic cells (DC) are important regulators of T cell immunity. The degree of stimulation, the pattern of co-stimulatory molecules expressed, and the cytokines secreted by DC dictate the nature of the effector and memory cells generated, particularly with respect to their Th1 or Th2 phenotypes. In this report we demonstrate that addition of activated DC to spleen cultures containing established Th2 polarized CD4+ T cells was sufficient to suppress Th2 and to induce Th1 cytokines in a recall response, a phenomenon referred to as phenotype reversal. The ability of activated DC to induce phenotype reversal displayed exquisite antigen specificity. The DC activator B7-DC XAb was more than 10,000-fold more efficient at inducing phenotype reversal than the TLR agonists, CpG-ODN and Gardiquimod. Characterization of the mechanisms governing phenotype reversal revealed the requirement for cognate interaction between the TCR: pMHC complex, the expression of the co-stimulation/adhesion molecule ICAM-1, and secretion of IL-12 and IFNƒ×ƒnby the activated DC. Requirement for the co-stimulation/adhesion molecule SLAM was found to be quantitative. Thus, activation of DC, particularly by cross linking B7-DC, can modulate well established Th2 T cell responses in an antigen specific manner.

Abstract The PD-1:PD-L1 axis is a major immune regulatory pathway that blunts T cell activation in the tumor microenvironment. We recently identified that PD-1 is also upregulated on ovarian mouse tumor-infiltrating myeloid dendritic cells (TIDCs) that exhibit an immune suppressive phenotype. Extending those observations in this study, we now report that PD-1 is also expressed on human myeloid TIDCs of ovarian cancer patients, on which it suppresses the expression of co-stimulatory molecules (CD40 and CD80) as well as production of inflammatory cytokines. Mechanistic studies revealed that PD-1 on TIDCs is associated with Src homology domain-containing phosphatase-2 (SHP-2) and that PD-1-mediated blockade of NFkB-dependent cytokine release is SHP-2 dependent. PD-1 also inhibits NFkB-mediated antigen presentation which appears, however, to be independent of SHP-2. Thus, suppression of NFkB is critical in mediating PD-1-induced paralysis of ovarian tumor-associated immune TIDCs and is mediated through multiple signaling circuits that are both SHP-2 dependent and independent.

Abstract PD-1: PD-L1 is a major inhibitory axis that acts to suppress tumor-rejecting effector responses. In addition to its expression and inhibitory functions in T and B cells; PD-1 has also been shown to be expressed on and thereby impact the functions of cells of innate arm such as dendritic cells (DCs) primarily at the tumor site but not in the periphery. We show here that one of the culprits in the tumor microenvironment responsible for enhancing PD-1 expression on the tumor-associated DCs is the cytokine IL-10; which is expressed in abundance in many malignancies including ovarian cancer. Based on inhibition and knockdown studies, we show that IL-10 mediated PD-1 expression depends on STAT3 activation. Using murine model of ovarian carcinoma (ID8), we show that tumor-associated DCs express not only high levels of PD-1 on the surface but also have increased expression of STAT-3 and p-STAT3 compared to splenic DCs. Blockade of PD-1 on DCs led to increased production of IL-10 which correlated with a further increase in PD-1 expression. In in vivo studies, blockade of PD-1 and IL-10 neutralization as combination therapy augmented the anti-tumor response in ID8 ovarian tumor bearing mice; leading to a decrease in tumor mass and a significant increase in survival. These results show that IL-10 and PD-1 pathway intersect in DCs in theTME hence making them attractive targets for therapy of ovarian cancer.

Abstract HER2 is a prime target for cancer therapeutics due to its high overexpression in tumors. Advanced clinical trials, in breast and prostate cancer, investigating the use of the HLA-A2-binding HER2 peptide p369-377 (E75) as a vaccine are ongoing. In the present study, we investigated the proteasomal processing of p369-377 and other epitopes from HER2. We did not detect processing of p369-377 by either the proteasome or immunoproteasome in vitro, suggesting that tumor cells do not naturally process this epitope from HER2 for presentation on HLA-A2. However, other HER2 peptides were found to be consistently processed by the proteasome and immunoproteasome. One newly identified processed peptide, HER2 p373-382, was found to bind HLA-A2 stronger than p369-377, despite algorithms that predicted p369-377 as a stronger binder. Cytotoxic T lymphocytes (CTL) specific for p373-382 recognized target cells pulsed with either p373-382 or p369-377. CTL specific for p373-382 also lysed HER2+HLA-A2+ human breast cancer cells more efficiently than p369-377-specific CTL. These results suggest that cancer cells are naturally processing and presenting p373-382. Furthermore, our results suggest that T cells generated against p369-377 in previous studies may have been cross-reacting with p373-382. Thus, the newly identified p373-382 peptide may be a more appropriate candidate for vaccines with this new evidence that it is processed and presented by HLA-A2 for recognition by HER2-specific CTL.

Abstract Ovarian cancer is an immune reactive tumor with a complex suppressive network that blunts immune eradication. One putative pathway of evasion may be recruitment of CD4 regulatory T cells (Treg) into the tumor microenvironment. This study investigated the association of tumor infiltrating Tregs in ovarian cancer patients with poor survival. Methods: Immunofluorescence of intraepithelial CD4+CD25+FOXP3+ Tregs, CD3+ and CD8+ cells was performed in tumors of 52 ovarian cancer patients. Average and maximum count of cells were associated with survival via Cox regression models and summarized with hazard ratios (HR) and 95% confidence intervals (CIs). Results: The maximum counts of Tregs in these patients suggests an association between higher number of Tregs and poor clinical outcome (HR=1.48, CI=0.97, 2.28), although not statistically significant (p=0.07). Moreover, presence of high CD8/Treg ratio (HR=0.7, CI=0.53, 0.91; p=0.008) as well as high CD8/CD4 ratio (HR=0.76, CI=0.57, 1.0; p=0.05) appear to be associated with good outcome. The CD3 lymphocyte count was not associated with survival (HR=0.9, CI=0.66, 1.24; p=0.52). Conclusion: Although the present pilot study was conducted with a limited number of patients, our data suggests that higher numbers of infiltrating Tregs might be associated with poor survival and low CD8/Treg ratio may be correlated with improved survival in patients with epithelial ovarian carcinoma. We plan to confirm these results in a larger set of patients.

Abstract Tumor dormancy remains a major hurdle in the treatment of cancers. Recently, the association between cancer stem cells (CSC) and tumor dormancy has been speculated in variety of cancers. Despite conventional therapies of breast cancer, most of the US deaths are attributed to relapse which is likely due to a failure of current treatment regimens to eliminate breast cancer stem cells (BCSC). We reported IFN-γ-induced HER-2/neu antigen loss and tumor relapse. We performed in vitro and in vivo studies using neu positive mammary carcinoma (MMC) tumors and their dominant negative (dn) IFN-γ Rα MMC sub-line. We showed that IFN-γ producing CD8+ T cells induced the de novo generation of a distinct BCSC variant that differed from conventional BCSC. The novel phenotype: i) is not intrinsically quiescent, ii) is reversible by blocking IFN-γ Rα signaling in the tumor, iii) upregulates serine protease inhibitors (SPI-6/PI-9) and MUC-1 that could render the tumors refractory to granzyme/perforin- and antibody-induced apoptosis, respectively, and iv) downregulates HER-2/neu expression upon emerging under the immune pressure. While HER-2/neu+ conventional BCSC have been shown to be sensitive to HER-2/neu-targeted immunotherapy, these novel BCSC-like phenotypes are refractory to such immunotherapy because of HER-2/neu loss. Identification of such tumor immunoediting pathways and mechanisms is expected to improve immunotherapy of breast cancer, by pathway blocking strategies.

Abstract Glycosphingolipid (GSL) Lactosyl Ceramide (LacCer) is thought to be involved in Pneumocystis interaction with the host. Our previous results show that treatment with glycosphingolipid synthesis inhibitor PDMP reduces the fungus lung burden as well as symptoms of inflammation in mice with Pneumocystis pneumonia (PCP). Experiments were set up to resolve whether anti-inflammatory effects were due to the specific mechanisms involved in innate immune responses to Pneumocystis, or to some general anti-inflammatory property of PDMP. Animals were infected with live organisms, or challenged with either beta-glucan (the pro-inflammatory component of Pneumocystis cell wall) or LPS (inducer of lung inflammation unrelated to Pneumocystis). At the experimental endpoint the following inflammatory parameters were assessed: leukocyte recruitment to the lungs, production of pro-inflammatory cytokines and chemokines, histopathology and lung damage. Results show that glucan-induced acute inflammation partially mimics the inflammation caused by the whole organism, and PDMP suppresses some of the inflammatory parameters affected in PCP. In contrast, although LPS induces comparable intensity of inflammation as live Pneumocystis or glucan, PDMP does not suppress any inflammatory parameters measured in this group. These results suggest that the mechanism of PDMP action is related to the features specific to Pneumocystis and host recognition of the microorganism. Further studies will attempt to determine the role of LacCer in these processes. Supported by NIH-RO1-HL62150 and Mayo Clinic

Lung adenocarcinoma (LUAD) is the most prevalent form of non–small cell lung cancer (NSCLC) and a leading cause of cancer death. Immune checkpoint inhibitors (ICIs) of programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) signaling induce tumor regressions in a subset of LUAD, but many LUAD tumors exhibit resistance to ICI therapy. Here, we identified Prkci as a major determinant of response to ICI in a syngeneic mouse model of oncogenic mutant Kras / Trp53 loss (KP)–driven LUAD. Protein kinase Cι (PKCι)–dependent KP tumors exhibited resistance to anti–PD-1 antibody therapy (α-PD-1), whereas KP tumors in which Prkci was genetically deleted (KPI tumors) were highly responsive. Prkci- dependent resistance to α-PD-1 was characterized by enhanced infiltration of myeloid-derived suppressor cells (MDSCs) and decreased infiltration of CD8 + T cells in response to α-PD-1. Mechanistically, Prkci regulated YAP1-dependent expression of Cxcl5 , which served to attract MDSCs to KP tumors. The PKCι inhibitor auranofin inhibited KP tumor growth and sensitized these tumors to α-PD-1, whereas expression of either Prkci or its downstream effector Cxcl5 in KPI tumors induced intratumoral infiltration of MDSCs and resistance to α-PD-1. PRKCI expression in tumors of patients with LUAD correlated with genomic signatures indicative of high YAP1-mediated transcription, elevated MDSC infiltration and low CD8 + T cell infiltration, and with elevated CXCL5 / 6 expression. Last, PKCι-YAP1 signaling was a biomarker associated with poor response to ICI in patients with LUAD. Our data indicate that immunosuppressive PKCι-YAP1-CXCL5 signaling is a key determinant of response to ICI, and pharmacologic inhibition of PKCι may improve therapeutic response to ICI in patients with LUAD.

PURPOSE APOBEC mutagenesis underlies somatic evolution and accounts for tumor heterogeneity in several cancers, including breast cancer (BC). In this study, we evaluated the characteristics of a real-world cohort for time-to-treatment discontinuation (TTD) and overall survival on CDK4/6 inhibitors (CDK4/6i) plus endocrine therapy (ET) and immune checkpoint inhibitors. METHODS Comprehensive genomic profiling results from 29,833 BC samples were analyzed for tumor mutational burden and APOBEC signatures. For clinical outcomes, a deidentified nationwide (United States–based) BC Clinico-Genomic Database (CGDB) was evaluated with log-rank and Cox models. Patients with hormone receptor–positive (HR+) human epidermal growth factor receptor 2–negative (HER2–) BC who received first-line ET and CDK4/6i were included. Eligible patients from Mayo Clinic and Duke University were HR+ HER2– BC with sequencing data between September 2013 and July 2020. RESULTS Of 29,833 samples sequenced, 7.9% were APOBEC+ with a high rate in invasive lobular carcinoma (16.7%) and in metastatic tumors (9.7%) relative to locally biopsied BC (4.3%; P < .001). In CGDB, 857 patients with HR+ HER2– BC received ET plus CDK4/6i in the first line. APOBEC+ patients had significantly shorter TTD on ET plus CDK4/6i than APOBEC– patients, 7.8 (95% CI, 4.3 to 14.6) versus 12.4 months (95% CI, 11.2 to 14.1; hazard ratio, 1.6; 95% CI, 1.03 to 2.39; P = .0036). Clinical benefit to immune checkpoint inhibitors was observed in HR+ HER2–, APOBEC+, tumor mutational burden–high patients, with four of nine CGDB patients (TTD 0.3-11.3 months) and four of six patients in Duke/Mayo cohorts (TTD 0.9-40.5 months) with a TTD of ≥ 3 months. CONCLUSION APOBEC+ HR+ HER2– patients had shorter TTD on first-line ET plus CDK4/6i relative to APOBEC– patients. Further research is needed to optimize the treatment of APOBEC+ HR+ HER2– BC and to investigate the efficacy of immunotherapeutic strategies in this population.