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For three years, COVID-19 has circulated among our communities and around the world, fundamentally changing social interactions, health care systems, and service delivery. For people living with (and receiving treatment for) cancer, pandemic conditions presented significant additional hurdles in an already unstable and shifting environment, including disrupted personal contact with care providers, interrupted access to clinical trials, distanced therapeutic encounters, multiple immune vulnerabilities, and new forms of financial precarity. In a 2020 perspective in this journal, we examined how COVID-19 was reshaping cancer care in the early stages of the pandemic and how these changes might endure into the future. Three years later, and in light of a series of interviews with patients and their caregivers from the United States and Australia conducted during the pandemic, we return to consider the potential legacy effects of the pandemic on cancer care. While some challenges to care provision and survivorship were unforeseen, others accentuated and amplified existing problems experienced by patients, caregivers, and health care providers. Both are likely to have enduring effects in the “post-pandemic” world, raising the importance of focusing on lessons that can be learned for the future.

To determine the feasibility and impact of neoadjuvant therapy (NT) in patients who present with advanced melanoma amenable to surgical resection.Given current effective systemic therapy for melanoma, the use of NT is being explored in patients with advanced melanoma with disease amenable to surgical resection.Prospective data from 3 institutions was obtained in patients with clinically evident Stage III/IV melanoma who underwent NT. The primary objective was to compare recurrence-free survival between patients who had pathologic complete response (pCR) to those with persistent disease.NT was offered to 45 patients, with 43 patients initiating various NT regimens including PD-1 antagonist (PD-1) therapy (N = 16), PD-1 plus ipilimumab (N = 10), BRAF/MEK inhibitor therapy (N = 14), a combination of those three (N = 1), and talimogene laherparepvec (TVEC) (N = 2). Thirty-two (74.1%) patients underwent surgery whereas 11 patients did not undergo surgery for these reasons: clinical CR (N = 7), progressive disease not amenable to resection (N = 3), and ongoing therapy (N = 1). 12 of 32 patients (37.5%) had pCR with these therapies: PD-1 (N = 4), PD-1 plus ipilimumab (N = 2), BRAF/MEK (N = 4), combination (N = 1), and TVEC (N = 1). At median follow-up of 16.4 months there was only 1 recurrence in the pCR group and patients with a pCR had significantly improved recurrence-free survival compared to patients without pCR (p = 0.004).Despite variability in NT regimens across institutions, NT for melanoma is feasible and associated with improved prognosis in patients who achieve a pCR. Maximizing rates of pCR could improve prognosis for patients with advanced melanoma.

Supplementary Table S3

Supplementary Figures S1 - S11

The APOBEC family of cytidine deaminases is one of the most common endogenous sources of mutations in human cancer. Genomic studies of tumors have found that APOBEC mutational signatures are enriched in the HER2 subtype of breast cancer and are associated with immunotherapy response in diverse cancer types. However, the direct consequences of APOBEC mutagenesis on the tumor immune microenvironment have not been thoroughly investigated. To address this, we developed syngeneic murine mammary tumor models with inducible expression of APOBEC3B. We found that APOBEC activity induced antitumor adaptive immune responses and CD4+ T cell–mediated, antigen-specific tumor growth inhibition. Although polyclonal APOBEC tumors had a moderate growth defect, clonal APOBEC tumors were almost completely rejected, suggesting that APOBEC-mediated genetic heterogeneity limits antitumor adaptive immune responses. Consistent with the observed immune infiltration in APOBEC tumors, APOBEC activity sensitized HER2-driven breast tumors to anti–CTLA-4 checkpoint inhibition and led to a complete response to combination anti–CTLA-4 and anti-HER2 therapy. In human breast cancers, the relationship between APOBEC mutagenesis and immunogenicity varied by breast cancer subtype and the frequency of subclonal mutations. This work provides a mechanistic basis for the sensitivity of APOBEC tumors to checkpoint inhibitors and suggests a rationale for using APOBEC mutational signatures and clonality as biomarkers predicting immunotherapy response in HER2-positive (HER2+) breast cancers.

Legends for Figures S1-S11 and Supplementary Tables S1-S3

EFfect of TGFbeta blockade on TIL PD-1 surface expression.

Although anti–PD-1 therapy has improved clinical outcomes for select patients with advanced cancer, many patients exhibit either primary or adaptive resistance to checkpoint inhibitor immunotherapy. The role of the tumor stroma in the development of these mechanisms of resistance to checkpoint inhibitors remains unclear. We demonstrated that pharmacologic inhibition of the TGFβ signaling pathway synergistically enhanced the efficacy of anti–CTLA-4 immunotherapy but failed to augment anti–PD-1/PD-L1 responses in an autochthonous model of BRAFV600E melanoma. Additional mechanistic studies revealed that TGFβ pathway inhibition promoted the proliferative expansion of stromal fibroblasts, thereby facilitating MMP-9–dependent cleavage of PD-L1 surface expression, leading to anti–PD-1 resistance in this model. Further work demonstrated that melanomas escaping anti–PD-1 therapy exhibited a mesenchymal phenotype associated with enhanced TGFβ signaling activity. Delayed TGFβ inhibitor therapy, following anti–PD-1 escape, better served to control further disease progression and was superior to a continuous combination of anti–PD-1 and TGFβ inhibition. This work illustrates that formulating immunotherapy combination regimens to enhance the efficacy of checkpoint blockade requires an in-depth understanding of the impact of these agents on the tumor microenvironment. These data indicated that stromal fibroblast MMP-9 may desensitize tumors to anti–PD-1 and suggests that TGFβ inhibition may generate greater immunologic efficacy when administered following the development of acquired anti–PD-1 resistance.See related Spotlight on p. 1444

qRT-PCR primers used in the current study.

The β-catenin signaling pathway has been demonstrated to promote the development of a tolerogenic dendritic cell (DC) population capable of driving regulatory T-cell (Treg) differentiation. Further studies have implicated tolerogenic DCs in promoting carcinogenesis in preclinical models. The molecular mechanisms underlying the establishment of immune tolerance by this DC population are poorly understood, and the methods by which developing cancers can co-opt this pathway to subvert immune surveillance are currently unknown. This work demonstrates that melanoma-derived Wnt5a ligand upregulates the durable expression and activity of the indoleamine 2,3-dioxygenase-1 (IDO) enzyme by local DCs in a manner that depends upon the β-catenin signaling pathway. These data indicate that Wnt5a-conditioned DCs promote the differentiation of Tregs in an IDO-dependent manner, and that this process serves to suppress melanoma immune surveillance. We further show that the genetic silencing of the PORCN membrane–bound O-acyl transferase, which is necessary for melanoma Wnt ligand secretion, enhances antitumor T-cell immunity, and that the pharmacologic inhibition of this enzyme synergistically suppresses melanoma progression when combined with anti–CTLA-4 antibody therapy. Finally, our data suggest that β-catenin signaling activity, based on a target gene expression profile that includes IDO in human sentinel lymph node–derived DCs, is associated with melanoma disease burden and diminished progression-free survival. This work implicates the Wnt–β-catenin signaling pathway as a novel therapeutic target in the melanoma immune microenvironment and demonstrates the potential impact of manipulating DC function as a strategy for optimizing tumor immunotherapy. Cancer Immunol Res; 3(9); 1082–95. ©2015 AACR.

Trial Schema

Purpose:In this prospective trial, we sought to assess the feasibility of concurrent administration of ipilimumab and radiation as adjuvant, neoadjuvant, or definitive therapy in patients with regionally advanced melanoma.Patients and Methods:Twenty-four patients in two cohorts were enrolled and received ipilimumab at 3 mg/kg every 3 weeks for four doses in conjunction with radiation; median dose was 4,000 cGy (interquartile range, 3,550–4,800 cGy). Patients in cohort 1 were treated adjuvantly; patients in cohort 2 were treated either neoadjuvantly or as definitive therapy.Results:Adverse event profiles were consistent with those previously reported with checkpoint inhibition and radiation. For the neoadjuvant/definitive cohort, the objective response rate was 64% (80% confidence interval, 40%–83%), with 4 of 10 evaluable patients achieving a radiographic complete response. An additional 3 patients in this cohort had a partial response and went on to surgical resection. With 2 years of follow-up, the 6-, 12-, and 24-month relapse-free survival for the adjuvant cohort was 85%, 69%, and 62%, respectively. At 2 years, all patients in the neoadjuvant/definitive cohort and 10/13 patients in the adjuvant cohort were still alive. Correlative studies suggested that response in some patients were associated with specific CD4+ T-cell subsets.Conclusions:Overall, concurrent administration of ipilimumab and radiation was feasible, and resulted in a high response rate, converting some patients with unresectable disease into surgical candidates. Additional studies to investigate the combination of radiation and checkpoint inhibitor therapy are warranted.

Supplementary Figures 1-8 from Enhanced Activation of Human Dendritic Cells by Inducible CD40 and Toll-like Receptor-4 Ligation

Supplementary Methods from Enhanced Activation of Human Dendritic Cells by Inducible CD40 and Toll-like Receptor-4 Ligation

Despite the potency of dendritic cells (DC) as antigen-presenting cells for priming adaptive immunity, DC-based cancer vaccines have been largely insufficient to effectively reduce tumor burden or prevent tumor progression in most patients. To enhance DC-based vaccines, we used the combination of a synthetic ligand-inducible CD40 receptor (iCD40) along with Toll-like receptor-4 (TLR-4) ligation in human monocyte-derived DCs. The iCD40 receptor permits targeted, reversible activation of CD40 in vivo, potentially bypassing the essential role of CD4+ T cells for activation of DCs. As a rigorous preclinical study of this approach, we evaluated key parameters of DC activation and function. Whereas neither iCD40 nor TLR-4 signaling alone led to high levels of interleukin (IL)-12p70 and IL-6, using iCD40 in combination with lipopolysaccharide (LPS) or monophosphoryl lipid A led to strongly synergistic production of both. Furthermore, this approach led to high expression of DC maturation markers, epitope-specific CTL and T helper 1 responses, as well as DC migration in vitro and in vivo. Moreover, use of iCD40-modified and LPS-stimulated DCs led to targeted expansion of autologous T cells against tumor-associated antigens, including prostate-specific membrane antigen, and elimination of preestablished tumors, supporting this technology as a potent strategy for DC-based cancer immunotherapy. [Cancer Res 2007;67(21):10528–10]

The APOBEC family of cytidine deaminases is one of the most common endogenous sources of mutations in human cancer. Genomic studies of tumors have found that APOBEC mutational signatures are enriched in the HER2 subtype of breast cancer and are associated with immunotherapy response in diverse cancer types. However, the direct consequences of APOBEC mutagenesis on the tumor immune microenvironment have not been thoroughly investigated. To address this, we developed syngeneic murine mammary tumor models with inducible expression of APOBEC3B. We found that APOBEC activity induced antitumor adaptive immune responses and CD4+ T cell–mediated, antigen-specific tumor growth inhibition. Although polyclonal APOBEC tumors had a moderate growth defect, clonal APOBEC tumors were almost completely rejected, suggesting that APOBEC-mediated genetic heterogeneity limits antitumor adaptive immune responses. Consistent with the observed immune infiltration in APOBEC tumors, APOBEC activity sensitized HER2-driven breast tumors to anti–CTLA-4 checkpoint inhibition and led to a complete response to combination anti–CTLA-4 and anti-HER2 therapy. In human breast cancers, the relationship between APOBEC mutagenesis and immunogenicity varied by breast cancer subtype and the frequency of subclonal mutations. This work provides a mechanistic basis for the sensitivity of APOBEC tumors to checkpoint inhibitors and suggests a rationale for using APOBEC mutational signatures and clonality as biomarkers predicting immunotherapy response in HER2-positive (HER2+) breast cancers.

The tumor-intrinsic NOD-, LRR- and pyrin domain-containing protein-3 (NLRP3) inflammasome–heat shock protein 70 (HSP70) signaling axis is triggered by CD8 + T cell cytotoxicity and contributes to the development of adaptive resistance to anti–programmed cell death protein 1 (PD-1) immunotherapy by recruiting granulocytic polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) into the tumor microenvironment. Here, we demonstrate that the tumor NLRP3-HSP70 axis also drives the accumulation of PMN-MDSCs into distant lung tissues in a manner that depends on lung epithelial cell Toll-like receptor 4 (TLR4) signaling, establishing a premetastatic niche that supports disease hyperprogression in response to anti–PD-1 immunotherapy. Lung epithelial HSP70-TLR4 signaling induces the downstream Wnt5a-dependent release of granulocyte colony-stimulating factor (G-CSF) and C-X-C motif chemokine ligand 5 (CXCL5), thus promoting myeloid granulopoiesis and recruitment of PMN-MDSCs into pulmonary tissues. Treatment with anti–PD-1 immunotherapy enhanced the activation of this pathway through immunologic pressure and drove disease progression in the setting of Nlrp3 amplification. Genetic and pharmacologic inhibition of NLRP3 and HSP70 blocked PMN-MDSC accumulation in the lung in response to anti–PD-1 therapy and suppressed metastatic progression in preclinical models of melanoma and breast cancer. Elevated baseline concentrations of plasma HSP70 and evidence of NLRP3 signaling activity in tumor tissue specimens correlated with the development of disease hyperprogression and inferior survival in patients with stage IV melanoma undergoing anti–PD-1 immunotherapy. Together, this work describes a pathogenic mechanism underlying the phenomenon of disease hyperprogression in melanoma and offers candidate targets and markers capable of improving the management of patients with melanoma.

Purpose:In this prospective trial, we sought to assess the feasibility of concurrent administration of ipilimumab and radiation as adjuvant, neoadjuvant, or definitive therapy in patients with regionally advanced melanoma.Patients and Methods:Twenty-four patients in two cohorts were enrolled and received ipilimumab at 3 mg/kg every 3 weeks for four doses in conjunction with radiation; median dose was 4,000 cGy (interquartile range, 3,550–4,800 cGy). Patients in cohort 1 were treated adjuvantly; patients in cohort 2 were treated either neoadjuvantly or as definitive therapy.Results:Adverse event profiles were consistent with those previously reported with checkpoint inhibition and radiation. For the neoadjuvant/definitive cohort, the objective response rate was 64% (80% confidence interval, 40%–83%), with 4 of 10 evaluable patients achieving a radiographic complete response. An additional 3 patients in this cohort had a partial response and went on to surgical resection. With 2 years of follow-up, the 6-, 12-, and 24-month relapse-free survival for the adjuvant cohort was 85%, 69%, and 62%, respectively. At 2 years, all patients in the neoadjuvant/definitive cohort and 10/13 patients in the adjuvant cohort were still alive. Correlative studies suggested that response in some patients were associated with specific CD4+ T-cell subsets.Conclusions:Overall, concurrent administration of ipilimumab and radiation was feasible, and resulted in a high response rate, converting some patients with unresectable disease into surgical candidates. Additional studies to investigate the combination of radiation and checkpoint inhibitor therapy are warranted.

Generating responses to tumor antigens poses a challenge for immunotherapy. This phase II trial (NCT02129075) tested fms-like tyrosine kinase 3 (Flt3) ligand pre-treatment enhancement of responses to dendritic cell (DC)-targeting vaccines. We evaluated a regimen of Flt3L (CDX-301) to increase DCs and other antigen-presenting cells, poly-ICLC (TLR3 agonist that activates DCs) and a vaccine comprising anti-DEC-205-NY-ESO-1, a fusion antibody targeting CD205, linked to NY-ESO-1. High-risk melanoma patients were randomized to vaccine, with and without CDX-301. The end point was immune response to NY-ESO-1. Flt3L increased peripheral monocytes and conventional DCs (cDCs), including cross-presenting cDC1 and cDC2 and plasmacytoid DCs. Significant increases in humoral and T-cell responses and activation of DCs, natural killer cells and T cells were elicited. Transcriptional analyses revealed gene signatures associated with CDX-301 induction of an early, durable immune response. This study reveals in vivo effects of Flt3L on innate immune cells in the setting of vaccination, leading to an immunogenic vaccine regimen. Bhardwaj et al. report that adding Flt3 ligand to the treatment strategy effectively increased DC populations and increased T-cell responses in a randomized phase II trial of a DC-targeted vaccine for the melanoma antigen NY-ESO-1.

BACKGROUND: In melanoma patients, microscopic tumor in the sentinel lymph node biopsy (SLN) increases the risk of distant metastases but the transition from tumor in the SLN to metastatic disease remains poorly understood. METHODS: Fluorescent staining for CD3, CD20, CD11c, and DNA was performed on SLN tissue and matching primary tumors. Regions of interest (ROI) were then chosen geometrically (e.g. tumor) or by fluorescent cell subset markers (e.g. CD11c). Each ROI was further analyzed using NanoString Digital Spatial Profiling high-resolution multiplex profiling. Digital counts for 59-panel immune related proteins were collected and normalized to account for system variation and ROI area. RESULTS: Tumor regions of SLNs had variable infiltration of CD3 cells among patients. The patient with overall survival (OS) > 8 years had the most CD11c- and CD3-expressing cells infiltrating the SLN tumor region. All patients had CD11c (dendritic cell, DC) infiltration into the SLN tumor region. Selecting ROI by specific cell subtype, we compared protein expression of CD11c cells between tumor and non-tumor/normal tissue SLN regions. Known markers of DC activation such as CD86, HLA-DR, and OX40L were lowest on CD11c cells within SLN tumor for the patient with OS < 1 year and highest on the patient with OS > 8 years. CONCLUSION: We demonstrate the feasibility of profiling the protein expression of CD11c cells within the SLN tumor. Identifying early regulators of melanoma control when the disease is microscopically detected in the SLN is beneficial and requires follow-up studies in a larger cohort of patients.

The mechanisms underlying tumor immunosurveillance and their association with the immune-related adverse events (irAEs) associated with checkpoint inhibitor immunotherapies remain poorly understood. We describe a metastatic melanoma patient exhibiting multiple episodes of spontaneous disease regression followed by the development of several irAEs during the course of anti-programmed cell death protein 1 antibody immunotherapy. Whole-exome next-generation sequencing studies revealed this patient to harbor a pyrin inflammasome variant previously described to be associated with an atypical presentation of familial Mediterranean fever. This work highlights a potential role for inflammasomes in the regulation of tumor immunosurveillance and the pathogenesis of irAEs.

Immune checkpoint blockade (ICB) therapies have significantly prolonged patient survival across multiple tumor types, particularly in melanoma. Interestingly, sex-specific differences in response to ICB have been observed, with males receiving a greater benefit from ICB than females, although the mechanism or mechanisms underlying this difference are unknown. Mining published transcriptomic data sets, we determined that the response to ICBs is influenced by the functionality of intratumoral macrophages. This puts into context our observation that estrogens (E2) working through the estrogen receptor α (ERα) stimulated melanoma growth in murine models by skewing macrophage polarization toward an immune-suppressive state that promoted CD8+ T cell dysfunction and exhaustion and ICB resistance. This activity was not evident in mice harboring macrophage-specific depletion of ERα, confirming a direct role for estrogen signaling within myeloid cells in establishing an immunosuppressed state. Inhibition of ERα using fulvestrant, a selective estrogen receptor downregulator (SERD), decreased tumor growth, stimulated adaptive immunity, and increased the antitumor efficacy of ICBs. Further, a gene signature that determines ER activity in macrophages predicted survival in patients with melanoma treated with ICB. These results highlight the importance of E2/ER signaling as a regulator of intratumoral macrophage polarization, an activity that can be therapeutically targeted to reverse immune suppression and increase ICB efficacy.

BackgroundImmunotherapy resistance has been correlated with epithelial-to-mesenchymal transition (EMT),1 2 however our understanding of tumor-intrinsic mechanisms driving this immune evasive phenotype is lacking. We have previously shown that Wnt ligands are upregulated in anti-PD-1 resistant melanomas,3 and postulated that upstream transcriptional regulation of select EMT pathways may underpin these findings. The hedgehog signaling (HH) transcription factor Gli2 promotes EMT.MethodsGli2 was constitutively activated (Gli2CA ) in a BRAFV600EPTEN-/- murine cell line via an N-terminal truncating mutation and silenced using CRISPR-Cas9. Multi-parameter flow cytometry and RNAseq was utilized to evaluate the impact of Gli2 on the tumor immune microenvironment. Anti-PD-1 resistance studies were performed in Gli2CA and control tumors. Bioinformatics studies were conducted using the melanoma TCGA and Hugo et al databases.2ResultsWe found upregulation of Gli2 targets in patients with anti-PD-1-refractory metastatic melanoma as well as in an autochthonous BRAFV600EPTEN-/- melanoma model after escape from anti-PD-1. RNAseq and Western blot studies demonstrated Gli2CA to promote EMT and Wnt ligand production in addition to upregulated COX2 in BRAFV600EPTEN-/- melanoma. This finding was reversed by genetic ablation and pharmacologic inhibition of Gli2, implicating a previously undescribed role for Gli2 in modulating COX2. These data were consistent with a notable correlation between a Gli2 signature and a prostaglandin synthesis signature in human melanoma TCGA database. Flow cytometry analysis showed exclusion of cytolytic T and NK cells, a shift from cDC1s to cDC2s, and enhanced MDSC recruitment in Gli2CA tumors. Consistent with these findings, whole tumor RNAseq of Gli2CA tumors demonstrated a decrease in Cd3e, Prf1, and Xcr1 with a concomitant increase in Cxcl1, Cxcl2, Ccl2, Ptgs2, and Arg1 relative to control tumors. RNAseq of FACS-sorted DCs from Gli2CA tumors demonstrated a loss of cDC1-associated genes including Xcr1, Wdfy4, and Clec9a compared to DCs derived from control tumors. In-line with our previous results showing that Wnt5a promotes MDSC recruitment in a Yap-dependent manner,4 we found that Yap inhibition or Wnt5a deletion in the BRAFV600EPTEN-/-Gli2CA cell line diminished MDSC-recruiting chemokines. Further consistent with these findings, Gli2CA tumors resist anti-PD-1 antibody therapy.Abstract 923 Figure 1Gli2 in tumors promotes Wnt and prostaglandin signaling, generating an immunosuppressive microenvironmentConclusionsOur data demonstrates that the HH transcription factor Gli2 drives the development of a tolerogenic tumor microenvironment unfavorable to anti-PD-1 immunotherapy by coordinating the upregulation of Wnt ligand expression and prostaglandin synthesis (figure 1). We propose that HH gene signatures are worthy of further study as a guide for selecting Wnt ligand and prostaglandin inhibitors in future immunotherapy studies.AcknowledgementsThe authors would like to acknowledge the Duke Cancer Institute Flow Cytometry Core.ReferencesBagaev A, et al. Conserved pan-cancer microenvironment subtypes predict response to immunotherapy. Cancer Cell 2021.Hugo W, et al. Genomic and transcriptomic features of response to anti-PD-1 therapy in metastatic melanoma. Cell 2016;165(1):35–44.DeVito NC, et al. Pharmacological Wnt ligand inhibition overcomes key tumor-mediated resistance pathways to anti-PD-1 immunotherapy. Cell Rep 2021;35(5):109071.Theivanthiran B, et al. A tumor-intrinsic PD-L1/NLRP3 inflammasome signaling pathway drives resistance to anti-PD-1 immunotherapy. J Clin Invest 2020;130(5):2570–2586.

BackgroundConventional dendritic cells (DCs) are essential mediators of anti-tumor immunity and the efficacy of anti-PD-1 checkpoint immunotherapies.1 Recent studies suggest that tumor-mediated development of a sub-population of tolerogenic DCs plays an important role in immune evasion.2 3 Metabolic reprogramming regulates tolerogenic DCs in the tumor microenvironment (TME).4 5 Activation of DCs leads to rewiring of cDC metabolism towards glycolysis to support T cell activation while tolerogenic DCs display enhanced fatty acid oxidation.6 Related to DC metabolic alterations, tumor-associated DCs (TADCs) are enriched in lipids and have a reduced capacity to present antigen to T cells. Lipid homeostasis is maintained through a complex network of transcription factors including sterol regulatory element-binding protein-2 (SREBP2) which drives the expression of mevalonate pathway genes.7 The identification of those tumor-controlled pathways that regulate tolerogenic DCs in the TME is expected to lead to the discovery of a novel family of immunotherapeutic targets.MethodsWe use transgenic mouse models of melanoma, sentinel lymph node (LN) tissue specimens derived from melanoma patients, single-cell RNA sequencing (scRNAseq), and flow cytometry-based metabolic assays to identify novel tumor-associated regulatory programs amongst different sub-populations of conventional DCs in the TME.Results scRNAseq of DCs isolated from the tumor-draining LN (TDLN) of a BRAFV600EPTEN-/- transgenic melanoma model revealed critical genetic differences in distinct DC sub-populations. We observed a migratory DC subset enriched in the expression of numerous immunoregulatory genes and identified CD63 as a surface marker to distinguish this DC subset from other conventional cDC1s and cDC2s. Further studies demonstrated CD63+ DCs to suppress T cell activation and promote CD4+FOXP3+ regulatory T cell (Treg) differentiation. Relative to other cDC subsets, CD63+ DCs overexpress genes of the mevalonate pathway leading to increased lipid content. Treatment of melanoma-bearing mice with a pharmacologic inhibitor of SREBP2 leads to a significant reduction in CD63+ DCs in the TDLN and reduced Tregs, resulting in suppressed tumor growth. Importantly, scRNAseq of DCs isolated from sentinel LNs of melanoma patients reveal that this population is conserved in humans.ConclusionsLipid homeostasis in TADCs is a major determinant of their metabolic state, but despite significant advances, the molecular pathways regulating tolerogenic DCs have remained poorly understood. Collectively, this data demonstrates an important role of the mevalonate pathway in driving a tolerogenic DC program and highlights the therapeutic targeting of SREBP2 and DC lipid metabolism as a promising approach to overcoming immune tolerance in the TME and boosting immunotherapy responses.ReferencesGardner A, Ruffell B. Dendritic cells and cancer immunity. Trends Immunol 2016;37:855–865. doi:10.1016/j.it.2016.09.006DeVito NC, Plebanek MP, Theivanthiran B, Hanks BA. Role of tumor-mediated dendritic cell tolerization in immune evasion. Front Immunol 2019;10:2876. doi:10.3389/fimmu.2019.02876Gerhard GM, Bill R, Messemaker M, Klein AM, Pittet MJ. Tumor-infiltrating dendritic cell states are conserved across solid human cancers. J Exp Med 2021;218. doi:10.1084/jem.20200264Plebanek MP, Sturdivant M, DeVito NC, Hanks BA. Role of dendritic cell metabolic reprogramming in tumor immune evasion. Int Immunol 2020;32:485–491. doi:10.1093/intimm/dxaa036Wculek SK, Khouili SC, Priego E, Heras-Murillo I, Sancho D. Metabolic control of dendritic cell functions: digesting information. Front Immunol 2019;10:775. doi:10.3389/fimmu.2019.00775Zhao F. et al. Paracrine Wnt5a-beta-Catenin signaling triggers a metabolic program that drives dendritic cell tolerization. Immunity 2018;48:147-+, doi:10.1016/j.immuni.2017.12.004Xue L. et al. Targeting SREBP-2-Regulated mevalonate metabolism for cancer therapy. Front Oncol 2020;10:1510, doi:10.3389/fonc.2020.01510Ethics ApprovalCollection of human tissue specimens was approved by the Duke Institutional Review Board under the title Immune Markers of Sentinel Nodes in Melanoma and the protocol number Pro00090678. All patients gave informed consent prior to participating in the study. All experiments involving animals were approved by the Duke University Institutional Animal Care and Use Committee (IACUC) under protocol number A174-18-07

Simple Summary The tumor-intrinsic NLRP3 inflammasome is a newly recognized player in the regulation of tumor-directed immune responses and promises to provide fresh insight into how tumors respond to immunotherapy. This brief review discusses recent data describing how activation of the tumor-intrinsic NLRP3 inflammasome contributes to immune evasion and what this pathway may provide to the field of immuno-oncology both in terms of pharmacologic targets capable of boosting responses to checkpoint inhibitor therapies and predictive biomarkers indicating which tumors may be most susceptible to these new therapeutic strategies. Abstract The tumor-intrinsic NOD-like receptor family, pyrin-domain-containing-3 (NLRP3) inflammasome, plays an important role in regulating immunosuppressive myeloid cell populations in the tumor microenvironment (TME). While prior studies have described the activation of this inflammasome in driving pro-tumorigenic mechanisms, emerging data is now revealing the tumor NLRP3 inflammasome and the downstream release of heat shock protein-70 (HSP70) to regulate anti-tumor immunity and contribute to the development of adaptive resistance to anti-PD-1 immunotherapy. Genetic alterations that influence the activity of the NLRP3 signaling axis are likely to impact T cell-mediated tumor cell killing and may indicate which tumors rely on this pathway for immune escape. These studies suggest that the NLRP3 inflammasome and its secreted product, HSP70, represent promising pharmacologic targets for manipulating innate immune cell populations in the TME while enhancing responses to anti-PD-1 immunotherapy. Additional studies are needed to better understand tumor-specific regulatory mechanisms of NLRP3 to enable the development of tumor-selective pharmacologic strategies capable of augmenting responses to checkpoint inhibitor immunotherapy while minimizing unwanted off-target effects. The execution of upcoming clinical trials investigating this strategy to overcome anti-PD-1 resistance promises to provide novel insight into the role of this pathway in immuno-oncology.

Background The emergence of immune checkpoint inhibitors (ICIs) has improved survival for patients with metastatic melanoma. The types of disease-response patterns to ICI therapy can be more complex relative to traditional chemotherapy and include mixed responses, pseudoprogression, and oligoprogression. The potential benefit of surgery after incomplete response to ICI therapy has not been explored. The purpose of this study was to explore outcomes of surgery after ICI therapy in patients with metastatic melanoma. Methods A retrospective study was conducted at two centers and included patients with melanoma who underwent surgery after treatment with monotherapy or combination therapy with anti–programmed cell death protein (PD) 1 and/or anti–cytotoxic T-lymphocyte associated protein (CTLA)-4 checkpoint blockade. Results Of 25 patients, nine received anti–CTLA-4 therapy, eight received anti–PD-1 therapy, and eight received both anti–CTLA-4 and anti–PD-1 therapies before surgery. Five patients were treated in the adjuvant setting and developed new lesions, whereas 20 patients were treated for metastatic disease and underwent surgery for persistent disease on imaging after ICI therapy. Twenty-five patients underwent 30 operations without complications. Twenty-seven of 30 masses were confirmed to be melanoma on pathology, one was a desmoid tumor and two were necrosis. At a median follow-up of 14.2 months, 2 patients died, 8 were alive with a known disease, and 15 continued to have no further evidence of disease. Conclusions Surgery was well tolerated in this cohort of patients receiving ICI therapy for melanoma. Surgery may benefit select patients with an oligoprogressive disease after ICI therapy. After a mixed response, surgery remains the only definitive method to render some patients free of disease.

Clinical trials that have a pharmacokinetic or a pharmacodynamic immunologic mechanism of action–based primary outcome could substantially improve the validity and efficiency of early development of immuno-oncology agents. Here, we outline different trial design options in this area, review examples from the literature and their unique immunologic aspects, and highlight how these trials have been underutilized. We illustrate how new technologies and translationally focused approaches can be successfully used to develop different classes of immunotherapeutic agents.

Pancreatic adenocarcinoma commonly presents as metastatic disease and harbors a dire prognosis due to its aggressive behavior, propensity for resistance to therapies, and lack of targetable driver mutations. Additionally, despite advances in other cancers, immunotherapy has been ineffective in this disease thus far and treatment remains centered around cytotoxic chemotherapy. Here, we present a case of a patient with pancreatic adenocarcinoma harboring both high microsatellite instability (MSI-H) and HER2 amplification. After an initial response to standard-of-care chemotherapy with FOLFIRINOX followed by progression, she was treated with dual immune checkpoint blockade, which resulted in a period of disease control. This was complicated by the development of autoimmune hypophysitis and an incidental finding of brain metastasis on magnetic resonance imaging (MRI). Her extracranial disease progressed while receiving stereotactic radiosurgery, with findings of lymphangitic spread in her lungs, and her treatment was changed to gemcitabine/nab-paclitaxel with trastuzumab. This resulted in a degree of extracranial disease control, though she experienced progressive brain metastases despite radiation and therapeutic switch to lapatinib and trastuzumab. Ultimately, the patient developed leptomeningeal disease which was not controlled by intrathecal trastuzumab. Given the rarity of central nervous system metastasis, HER2 amplification, and MSI in pancreatic cancer, this patient's presentation represents a confluence of multiple unique features. This case highlights the clinical value of up-front next-generation sequencing in metastatic pancreatic cancer and the ability of pancreatic cancer with actionable molecular variants to develop atypical sites of disease and adaptive resistance.

The APOBEC family of cytidine deaminases is one of the most common endogenous sources of mutations in human cancer. Genomic studies of tumors have found that APOBEC mutational signatures are particularly enriched in the HER2 subtype of breast cancer and have been associated with immunotherapy response in diverse cancer types. However, the direct consequences of APOBEC mutagenesis on the tumor immune microenvironment have not been thoroughly investigated. To address this, we developed syngeneic murine mammary tumor models with inducible expression of APOBEC3B. We found that APOBEC activity induces an antitumor adaptive immune response and CD4+ T cell-mediated tumor growth inhibition. While polyclonal APOBEC tumors had a moderate growth defect, clonal APOBEC tumors were almost completely rejected by the immune system, suggesting that APOBEC-mediated genetic heterogeneity limits the antitumor adaptive immune response. Consistent with the observed immune infiltration in APOBEC tumors, APOBEC activity sensitized HER2-driven breast tumors to checkpoint inhibition. In human breast cancers, the relationship between APOBEC mutagenesis and immunogenicity varied by breast cancer subtype and the frequency of subclonal mutations. This work provides a mechanistic basis for the sensitivity of APOBEC tumors to checkpoint inhibitors and suggests a rationale for using APOBEC mutational signatures as a biomarker predicting immunotherapy response in HER2-positive breast cancers.SIGNIFICANCEAPOBEC mutational signatures are observed in many cancers, yet the consequences of these mutations on the tumor immune microenvironment are not well understood. Using a novel mouse model, we show that APOBEC activity sensitizes HER2-driven mammary tumors to checkpoint inhibition and could inform immunotherapy treatment strategies for HER2-positive breast cancer patients.

Five years ago, the Melanoma Research Foundation (MRF) conducted an assessment of the challenges and opportunities facing the melanoma research community and patients with melanoma. Since then, remarkable progress has been made on both the basic and clinical research fronts. However, the incidence, recurrence, and death rates for melanoma remain unacceptably high and significant challenges remain. Hence, the MRF Scientific Advisory Council and Breakthrough Consortium, a group that includes clinicians and scientists, reconvened to facilitate intensive discussions on thematic areas essential to melanoma researchers and patients alike, prevention, detection, diagnosis, metastatic dormancy and progression, response and resistance to targeted and immune-based therapy, and the clinical consequences of COVID-19 for patients with melanoma and providers. These extensive discussions helped to crystalize our understanding of the challenges and opportunities facing the broader melanoma community today. In this report, we discuss the progress made since the last MRF assessment, comment on what remains to be overcome, and offer recommendations for the best path forward.

Background Responses to anti-PD-1 antibodies (aPD1) have changed the therapeutic landscape of metastatic melanoma, however predictive biomarkers of resistance are lacking. Beta-catenin pathway activation has been inversely correlated with tumor-infiltrating T lymphocytes in melanoma as well as several other solid tumors.1 However, activating mutations involving this pathway are rare, implying that the modulation of upstream Wnt ligand/Fzd receptor (Wnt/Fzd) signaling could be a critical regulator of anti-tumor immunity. Indeed, expression of certain Wnt ligands has been associated with inferior responses to checkpoint inhibitor immunotherapy in metastatic melanoma patients.2 In addition, we have further found tumor-derived paracrine and autocrine Wnt ligand signaling to drive dendritic cell tolerization and to be associated with escape from aPD1 therapy in transgenic mouse models.3 4 No studies to date have focused on the impact of the various regulators and components of proximal Wnt/Fzd receptor signaling on resistance to aPD1 therapy in melanoma patients. We therefore developed a unique Wnt/Fzd pathway panel using Nanostring technology to examine alterations in Wnt ligands, their receptors, and regulators as a predictor of aPD1 resistance. Methods To test whether this panel could identify aPD1 resistant patients, Nanostring analysis was performed on archival FFPE tissue specimens of 12 responding (R) and 12 nonresponding (NR) metastatic melanoma patients (pts) taken prior to aPD1 monotherapy. Response was assessed radiographically by week 12 RECIST criteria. Results Several components of both canonical and non-canonical Wnt ligand signaling, including regulators of autocrine/paracrine signaling, were upregulated in aPD1 NR pts compared to R pts (figure 1, table 1). GZMB, CD8, and IFNG were among cytotoxic T cell related genes upregulated in Rs. Upregulation of SFRP2 and DKK2 in NR pts, classically negative feedback regulators of Wnt ligands, are a reflection of enhanced Wnt ligand signaling activity. Conclusions This study supports the importance of paracrine and autocrine Wnt ligand signaling in the regulation of effector T cell responses and aPD1 resistance in cancer. In addition to predicting response to aPD1 checkpoint inhibitor immunotherapy, these findings further suggest that this Wnt signaling panel could serve as a predictive marker of immunologic response to Wnt ligand inhibitors, such as the PORCN inhibitors, which are currently under development. We continue to accrue additional pts to further validate these findings. Future studies will include a comparison of pre-treatment and on-treatment biopsies to evaluate these markers as predictors of adaptive aPD1 resistance. Acknowledgements Holly Dressman, PhD of the Duke Center for Genomic and Computational Biology for her assistance with the Nanostring samples; Jenna Goodwin, Carol Ann Wiggs, and Jennifer Nixon of the Duke Clinical Melanoma Research Team for their assistance with the melanoma tissue acquisition protocol; Tadas Rimkus of Nanostring for his assistance with analysis Trial Registration NCT02694965 Ethics Approval This study was approved by Duke University’s Institutional Review Board, protocol number Pro00059349 Consent Not applicable References Luke JJ, B.R., Spranger S, Sweis RF, Lingen MW, Lengyel E, Zha Y, Gajewski TF. Wnt/Beta-catenin pathway activation correlates with immune exclusion across most human cancers. Journal of Clinical Oncology 2016;34(15). Hugo W, et al. Genomic and transcriptomic features of response to anti-pd-1 therapy in metastatic melanoma. Cell 2016;165(1): p. 35–44. DeVito NC, X.C., Zhao F, Evans KS, Theivanthiran B, Lewicki J, Hoey T, Hurwitz H, Strickler JH, Hanks BA. Paracrine wnt-β-catenin signaling inhibition as a strategy to enhance the efficacy of anti-PD-1 antibody (Ab) therapy in a transgenic model of melanoma. Journal of Clinical Oncology, 2017. 35(no. 15_suppl). Zhao F, et al. Paracrine Wnt5a-beta-Catenin signaling triggers a metabolic program that drives dendritic cell tolerization. Immunity 2018;48(1): p. 147–160 e7.

SUMMARY While immune checkpoint blockade is associated with prolonged responses in multiple cancers, most patients still do not benefit from this therapeutic strategy. The Wnt-β-catenin pathway is associated with diminished T cell infiltration; however, activating mutations are rare, implicating a role for autocrine/paracrine Wnt ligand-driven signaling in immune evasion. In this study, we show that proximal mediators of the Wnt signaling pathway are associated with anti-PD-1 resistance, and pharmacologic inhibition of Wnt ligand signaling supports anti-PD-1 efficacy by reversing dendritic cell tolerization and the recruitment of granulocytic myeloid-derived suppressor cells in autochthonous tumor models. We further demonstrate that the inhibition of Wnt signaling promotes the development of a tumor microenvironment that is more conducive to favorable responses to checkpoint blockade in cancer patients. These findings support a rationale for Wnt ligand-focused treatment approaches in future immunotherapy clinical trials and suggest a strategy for selecting those tumors more responsive to Wnt inhibition., Graphical abstract, In brief Anti-PD-1-refractory melanoma exhibits elevated Wnt ligand signaling activity. DeVito et al. demonstrate that pharmacologic inhibition of proximal Wnt ligand signaling sensitizes transgenic models of melanoma and lung cancer to anti-PD-1 checkpoint inhibitor immunotherapy by reversing dendritic cell tolerization and suppressing recruitment of granulocytic myeloid-derived suppressor cells to the tumor bed.

Immune checkpoint inhibitors, including antibodies that block programmed cell death protein-1 (PD-1) and PD-L1, have transformed the management of many cancers. However, the majority of patients have primary or acquired resistance to these immunotherapies. There is a significant unmet need for predictive biomarkers that can reliably identify patients who derive a clinically meaningful response from PD-1/PD-L1 blockade. High tumor mutational burden (TMB-H) has shown promise as a biomarker in lung cancer, but the broad applicability of TMB-H as a biomarker of response across all solid tumors is unclear. The FDA has approved the PD-1 inhibitor, pembrolizumab, as a therapy for all solid tumors with TMB equal to or greater than 10 mutations/megabase as measured by the FoundationOne CDx assay. This approval was based on an exploratory analysis of the KEYNOTE-158 study, which was a single-arm, phase II multi-cohort study of pembrolizumab for select, previously treated advanced solid tumors. Here, we elucidate the caveats of using TMB as a biomarker with a universal threshold across all solid tumors. While we recognize the importance of this and other FDA pan-cancer approvals, several questions about TMB as a predictive biomarker remain unanswered. In this perspective, we discuss clinical trial evidence in this area. We review the relationship between TMB and the tumor immune microenvironment. We highlight the risks of extrapolating evidence from a limited number of tumor histologies to all solid tumors, and we propose avenues for future research.

Background/aim To determine whether BMI and sarcopenia were related to treatment-limiting toxicity or efficacy of pembrolizumab treatment in melanoma patients. Patients and methods Medical records for melanoma patients undergoing pembrolizumab treatment at Duke University from January 2014 to September 2018 were reviewed. Pre-treatment measurements such as BMI were collected. Pre-treatment CT imaging was used to determine psoas muscle index (PMI). Patients in the lowest sex-specific tertile of PMI were sarcopenic. Logistic regression measured associations with treatment toxicity and response. Kaplan-Meier analysis assessed progression-free survival (PFS) and overall survival (OS). Results Among 156 patients, the overall objective response rate was 46.2% and 29 patients (18.6%) experienced treatment-limiting toxicity. Sarcopenia was not significantly associated with toxicity, response, or survival. However, obese patients (BMI >30) experienced higher rates of toxicity (p=0.0007). Conclusion Sarcopenia did not appear to predict clinically relevant outcomes. Obesity, however, represents a readily available predictor of pembrolizumab toxicity.

Background This study evaluates the utility of whole-body PET-CT for the initial staging and subsequent surveillance imaging of patients with completely resected stage II and stage III melanoma. Methods A single-center, retrospective review of patients who received perioperative whole-body PET-CT from January 1, 2005 to December 1, 2019 within three months of initial melanoma diagnosis was performed. Results Of 258 total patients with completely resected melanoma who had a PET-CT within 3 months after their melanoma diagnosis, 113 had stage II and 145 had stage III melanoma. PET-CT detected distant metastasis in 3 (2.7%) of 113 stage II patients and 7 (4.8%) of 145 stage III patients. 179 of 258 patients had adequate follow-up time to determine whether they received surveillance cross-sectional imaging and whether they had a melanoma recurrence. 143 (79.9%) received subsequent surveillance imaging, 74 of whom developed a recurrence. In 64 (86.5%) of 74 cases, recurrence was detected by routine surveillance. 26 (34.2%) of 76 stage II and 65 (63.1%) of 103 stage III patients developed a recurrence. The median time to recurrence among the 179 patients for stage II and III was 16.3 and 13.0 months, respectively. Conclusions These findings indicate that baseline staging with whole-body PET-CT rarely provides information that changes initial management. Rather, the value of the initial PET-CT is as a baseline for subsequent surveillance scans. Therefore, it may be premature to discourage cross-sectional imaging for patients with stage II and III melanoma without supportive evidence or a reliable biomarker of recurrent disease.

The dendritic cell (DC) is recognized as a vital mediator of anti-tumor immunity. More recent studies have also demonstrated the important role of DCs in the generation of effective responses to checkpoint inhibitor immunotherapy. Metabolic programming of DCs dictates their functionality and can determine which DCs become immunostimulatory versus those that develop a tolerized phenotype capable of actively suppressing effector T-cell responses to cancers. As a result, there is great interest in understanding what mechanisms have evolved in cancers to alter these metabolic pathways, thereby allowing for their continued progression and metastasis. The therapeutic strategies developed to reverse these processes of DC tolerization in the tumor microenvironment represent promising candidates for future testing in combination immunotherapy clinical trials.

The vast majority of cancer-related deaths are due to metastasis, a process that requires evasion of the host immune system. In addition, a significant percentage of cancer patients do not benefit from our current immunotherapy arsenal due to either primary or secondary immunotherapy resistance. Importantly, select subsets of dendritic cells (DCs) have been shown to be indispensable for generating responses to checkpoint inhibitor immunotherapy. These observations are consistent with the critical role of DCs in antigen cross-presentation and the generation of effective anti-tumor immunity. Therefore, the evolution of efficient tumor-extrinsic mechanisms to modulate DCs is expected to be a potent strategy to escape immunosurveillance and various immunotherapy strategies. Despite this critical role, little is known regarding the methods by which cancers subvert DC function. Herein, we focus on those select mechanisms utilized by developing cancers to co-opt and tolerize local DC populations. We discuss the reported mechanisms utilized by cancers to induce DC tolerization in the tumor microenvironment, describing various parallels between the evolution of these mechanisms and the process of mesenchymal transformation involved in tumorigenesis and metastasis, and we highlight strategies to reverse these mechanisms in order to enhance the efficacy of the currently available checkpoint inhibitor immunotherapies.

BackgroundOur understanding of those underlying mechanisms that contribute to metastatic progression in melanoma remains limited. While uncommon, melanoma hyperprogression in response to immunotherapy is likely to be an extreme form of acquired resistance. Therefore, studies that define the underlying mechanisms of these processes are expected to provide insight into the discovery of novel therapeutic targets and predictive biomarkers. We previously demonstrated that tumor-intrinsic NLRP3 drives adaptive resistance to anti-PD-1 immunotherapy (anti-PD-1) by inducing the recruitment of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) via the upregulation of CXCL5. Gain-of-function polymorphisms in the TLR4 gene have been associated with pulmonary metastases in melanoma patients. We have shown HSP70 to promote PMN-MDSC chemotaxis via the stimulation of TLR4 signaling. As a result, we hypothesized that the tumor NLRP3 inflammasome may also contribute to distant metastatic progression and disease hyperprogression during immunotherapy by establishing a long-distance signaling axis mediated by HSP70-TLR4 signaling in the lung.MethodsWe pharmacologically and genetically inhibited the NLRP3 inflammasome and HSP70 in a transgenic BRAFV600E mouse model to examine their role in distant metastatic progression before and during anti-PD-1. An inducible type II pulmonary epithelial cell-specific TLR4 knock-out mouse model was engineered to examine the role of distant HSP70-TLR4 signaling in the recruitment of PMN-MDSCs and subsequent metastatic progression to the lung. Plasma HSP70 levels were monitored in melanoma patients undergoing anti-PD-1ResultsAnti-PD-1 significantly increases CXCL2/CXCL5 expression and PMN-MDSC accumulation in the lungs of the transgenic BRAFV600E model. This effect is reversed by 1) tumor-targeted ablation and pharmacologic inhibition of NLRP3 but not systemic host knock-out of NLRP3, 2) Pharmacologic Wnt5a ligand inhibition, 3) tumor-specific ablation and inhibition of HSP70. Inducible knock-out of TLR4 in type II epithelial cells suppressed Wnt5a and CXCL5 expression and inhibited the recruitment of PMN-MDSCs to the lung in response to anti-PD-1. Tumor-specific inhibition of NLRP3/HSP70 and lung-specific ablation of TLR4 suppressed metastatic progression following anti-PD-1 in the BRAFV600E melanoma model. Combination anti-PD-1 and NLRP3 inhibition suppressed primary melanoma progression and distant melanoma metastases versus anti-PD-1 monotherapy. Elevated plasma levels of HSP70 were associated with disease hyperprogression in metastatic melanoma patients undergoing anti-PD-1Abstract 319 Figure 1Tumor-intrinsic NLRP3 inflammasome and metastasisConclusionsTogether, these results describe a novel cross-talk mechanism between the primary tumor and the lung that mediates distant metastatic progression that is accentuated following anti-PD-1 (figure 1). Future clinical studies are needed to evaluate the pharmacologic inhibition of this tumor-lung NLRP3/HSP70/TLR4/Wnt5a/CXCL5 axis on melanoma metastasis and disease hyperprogression during checkpoint inhibitor immunotherapy

Background MBM have a unique molecular profile compared to ECM. Methods We analyzed a previously published dataset from MD Anderson Cancer Center, including RNA-seq on surgically resected, FFPE MBM and ECM from the same patients. STAR pipeline was used to estimate mRNA abundance. DESeq2 package was used to perform differential gene expression (DGE) analyses. Pathway analysis was performed using Gene Set Enrichment Analysis (GSEA). Paired DGE and GSEA compared MBM vs. lymph node (LN) metastases (n = 16) and MBM vs. skin mets (n = 10). CIBERSORTx estimated relative abundance of immune cell types in MBM and ECM. GATK Mutect2 pipeline was used to call somatic mutations using paired normal tumor samples. Mutations were annotated using the Ensembl Variant Effect Predictor and visualized using the Maftools package in R. RNA-seq was available on 54 human primary cutaneous melanomas (CM). Gene Ontology or KEGG Pathway analysis was performed using goana function of limma package in R. Results Paired GSEA found that autophagy pathways may be up-regulated in MBM vs. LN and MBM vs. skin mets. On a single-gene level, the most strongly up-regulated genes in autophagy pathways were GFAP and HBB. Fold changes in other autophagy-related genes were low and did not reach significance. Comparison between CM which recurred in brain vs. CM which did not recur identified up-regulation of autophagy pathways. CIBERSORTx identified an increased proportion of immune suppressive M2 macrophages compared to tumor suppressive M1 macrophages in MBMs and ECMs. Conclusion Up-regulation of autophagy pathways was observed in patient-matched MBM vs. LN and skin mets. This finding was driven by up-regulation of GFAP and HBB, which could reflect changes in the tumor microenvironment. Higher M2:M1 ratio may contribute to an immune suppressive tumor microenvironment and may be targetable. Validation of our findings in an independent Duke dataset is ongoing.

As cancer strikes, individuals vary not only in terms of factors that contribute to its occurrence and development, but as importantly, in their capacity to respond to treatment. While exciting new therapeutic options that mobilize the immune system against cancer have led to breakthroughs for a variety of malignancies, success is limited to a subset of patients. Pre-existing immunological features of both the host and the tumor may contribute to how patients will eventually fare with immunotherapy. A broad understanding of baseline immunity, both in the periphery and in the tumor microenvironment, is needed in order to fully realize the potential of cancer immunotherapy. Such interrogation of the tumor, blood, and host immune parameters prior to treatment is expected to identify biomarkers predictive of clinical outcome as well as to elucidate why some patients fail to respond to immunotherapy. To approach these opportunities for progress, the Society for Immunotherapy of Cancer (SITC) reconvened the Immune Biomarkers Task Force. Comprised of an international multidisciplinary panel of experts, Working Group 4 sought to make recommendations that focus on the complexity of the tumor microenvironment, with its diversity of immune genes, proteins, cells, and pathways naturally present at baseline and in circulation, and novel tools to aid in such broad analyses.