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In our opinion the most urgent needs to improve patient outcomes are: 1) a deeper ability to measure cancer immunobiology, and 2) increased availability of agents that, coupled with predictive biomarkers, will be used to tailor anti-cancer immunity. Tailoring effective immunotherapy will entail combinations of immunotherapeutics that augment priming of anti-cancer immunity, boost expansion of effector and memory cells of the T, B and NK lineage, amplify innate immunity and relieve checkpoint inhibition. Alternatives to inducing adaptive immunity to cancer include synthetic immunology that incorporate bi-specifics that target T cells to cancer or adoptive immunotherapy with gene-modified immune cells.

Meeting abstracts Analysis of tumor-infiltrating immune cells using quantitative immunohistochemistry (IHC) has proved to be a powerful prognostic biomarker in colon cancer [[1][1], [2][2]]. Similar observations have been made in patients with oral, head and neck squamous cell carcinoma (OHNSCC)

Meeting abstracts Generation of a therapeutic immune response against a diverse set of antigens expressed by a patient's cancer is a central goal of cancer immunotherapy. This goal is important because diverse responses may prevent escape of antigen loss variants. To accomplish this goal we have

The importance of anti-tumor immunity by CD8+ T cells is well defined, but antigen-specific immune monitoring for CD8+ responses across many potential tumor antigens is expensive and difficult. This difficulty is compounded by increasing evidence that every tumor has unique mutant neoepitopes. We hypothesized that new technologies in peptide printing might allow us to partially overcome this obstacle by instead characterizing antibody responses against a paired array of neoepitope and native peptides. We designed a 15-mer peptide array of mutated and native peptides from the murine mammary carcinoma 4T1 and used it to characterize the serum IgG antibody responses to vaccination with 4T1 autophagosome-enriched vaccine (DRibbles), poly-IC adjuvant, the combination of both, or naïve animals across 4 independent experiments. This array was printed by JPT peptides and included 75 pairs of single-nucleotide polymorphic and native peptides identified by both our own whole exome sequencing and the current 4T1 literature. We also included other sequences of interest to 4T1 immunity such as the retrovirus fragment AH1. MHCI peptide predictions were robust and used the top NetMHCpan v2.8 score from all possible windowed 8,9,10, and 11-mers for H2-Kd,Ld, and Dd surrounding the mutation site in its native protein context. The results of this work identify a linear correlation between higher predicted peptide MHCI binding affinity and the IgG antibody signals increased in combination treated groups versus controls. Linear regression analysis demonstrates that normalized antibody responses to mutated and native 4T1 peptides are more likely to be higher in sera from autophagosome-enriched vaccine plus poly-IC treated animals than naïve animals if these peptides contain higher affinity domains for MHCI (p These results identify a previously unknown link between predicted MHCI binding affinity and the anti-tumor antibody response following combination immunotherapy - suggesting some antigen-specific interaction between B cells and CD8+ T cells that might be exploited to improve the immune monitoring of cancer therapies. Citation Format: Tyler W. Hulett, Shawn Jensen, Christopher Dubay, Carlo Bifulco, Michael Afentoulis, Ashok Reddy, Larry David, Bernard A. Fox. Increased IgG antibody responses to neoepitope and native peptides containing high affinity domains for MHCI following combination cancer immunotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4900.

Recent work by Rosenberg, et. al. demonstrates the role of mutated epitopes in natural anti-cancer adaptive immunity. This has led some to hypothesize that cancer vaccines may need to induce or augment immunity against mutated and potentially patient-specific epitopes to achieve therapeutic efficacy. In the case of whole-cell cancer vaccines, this could happen either indirectly through epitope spreading, or directly against 'hotspot' mutation sites on oncogenes. The purpose of this study is to determine whether patients who received an irradiated GM-CSF-secreting whole-cell prostate cancer vaccine, GVAX, preferentially developed humoral immune responses against mutated proteins. Archived pre-treatment and week 11 serum from patients enrolled on an investigator-initiated combination immunotherapy trial were assessed using protein arrays (ProtoArray, Invitrogen). Antibody responses that were increased in the week 11 sera were considered increased as a result of immunotherapy. Next we utilized reported liquid chromatography tandem mass spectrometry (LC-MS/MS) proteomics and whole-exome sequencing data for LNCaP and PC3, the two cell lines contained in prostate GVAX, to assess whether the targets of elevated antibody responses detected by protein array were directed preferentially against the mutated proteins contained in the vaccine. Of the 7554 different human proteins included in our analysis, a mean of 63 candidate responses were identified for each patient (SD = 43). These candidate responses were then compared to published non-synonymous mutations in LNCaP and PC3, published LC-MS/MS proteomics on the protein content of LNCaP and PC3, and randomized lists of proteins on the array [1-3]. Preliminary analysis suggests that there was no increase in antibody responses above background against proteins with published cell-line specific mutations. However, the number of antibody responses was increased against proteins identified by mass spectrometry (p = 0.017). This result suggests that when GM-CSF secreting whole-cell vaccine is not combined with other immunotherapies, vaccine alone may be insufficient to induce or augment immune responses against mutated epitopes. Supported by The Prostate Cancer Foundation, DAMD PC02009, Robert W. Franz, the Chiles Foundation, ARCS Foundation: Portland, and the OCTRI, OSLER TL1 award.