Advances and challenges in cancer immunoprevention and immune interception

Invasive cancers typically evade immune surveillance through profound local and systemic immunosuppression, preventing their elimination or control. Targeting immune interventions to prevent or intercept premalignant lesions, before significant immune dysregulation has occurred, may be a more successful strategy. The field of cancer immune interception and prevention is nascent, and the scientific community has been slow to embrace this potentially most rational approach to reducing the global burden of cancer. This may change due to recent promising advances in cancer immunoprevention including the use of vaccines for the prevention of viral cancers, the use of cancer-associated antigen vaccines in the setting of precancers, and the development of cancer-preventative vaccines for high-risk individuals who are healthy but carry cancer-associated heritable genetic mutations. Furthermore, there is increasing recognition of the importance of cancer prevention and interception by national cancer organizations. The National Cancer Institute (NCI) recently released the National Cancer Plan, which includes cancer prevention among the top priorities of the institute. The NCI's Division of Cancer Prevention has been introducing new funding opportunities for scientists with an interest in the field of cancer prevention: The Cancer Prevention-Interception Targeted Agent Discovery Program and The Cancer Immunoprevention Network. Moreover, the Human Tumor Atlas Network is spearheading the development of a precancer atlas to better understand the biology of pre-invasive changes, including the tissue microenvironment and the underlying genetics that drive carcinogenesis. These data will inform the development of novel immunoprevention/immuno-interception strategies. International cancer foundations have also started recognizing immunoprevention and immune interception with the American Association for Cancer Research, Cancer Research UK and the Society for Immunotherapy of Cancer each implementing programming focused on this area. This review will present recent advances, opportunities, and challenges in the emerging field of cancer immune prevention and immune interception.

Post-translational covalent assembly of CAR and synNotch receptors for programmable antigen targeting

Chimeric antigen receptors (CARs) and synthetic Notch (synNotch) receptors are engineered cell-surface receptors that sense a target antigen and respond by activating T cell receptor signaling or a customized gene program, respectively. Here, to expand the targeting capabilities of these receptors, we develop "universal" receptor systems for which receptor specificity can be directed post-translationally via covalent attachment of a co-administered antibody bearing a benzylguanine (BG) motif. A SNAPtag self-labeling enzyme is genetically fused to the receptor and reacts with BG-conjugated antibodies for covalent assembly, programming antigen recognition. We demonstrate that activation of SNAP-CAR and SNAP-synNotch receptors can be successfully targeted by clinically relevant BG-conjugated antibodies, including anti-tumor activity of SNAP-CAR T cells in vivo in a human tumor xenograft mouse model. Finally, we develop a mathematical model to better define the parameters affecting universal receptor signaling. SNAP receptors provide a powerful strategy to post-translationally reprogram the targeting specificity of engineered cells.

Randomized, Double-Blind, Placebo-Controlled Trial of MUC1 Peptide Vaccine for Prevention of Recurrent Colorectal Adenoma

PURPOSE

To assess whether MUC1 peptide vaccine produces an immune response and prevents subsequent colon adenoma formation.

PATIENTS AND METHODS

Multicenter, double-blind, placebo-controlled randomized trial in individuals age 40 to 70 with diagnosis of an advanced adenoma ≤1 year from randomization. Vaccine was administered at 0, 2, and 10 weeks with a booster injection at week 53. Adenoma recurrence was assessed ≥1 year from randomization. The primary endpoint was vaccine immunogenicity at 12 weeks defined by anti-MUC1 ratio ≥2.0.

RESULTS

Fifty-three participants received the MUC1 vaccine and 50 placebo. Thirteen of 52 (25%) MUC1 vaccine recipients had a ≥2-fold increase in MUC1 IgG (range, 2.9-17.3) at week 12 versus 0/50 placebo recipients (one-sided Fisher exact P < 0.0001). Of 13 responders at week 12, 11 (84.6%) responded to a booster injection at week 52 with a ≥2-fold increase in MUC1 IgG measured at week 55. Recurrent adenoma was observed in 31 of 47 (66.0%) in the placebo group versus 27 of 48 (56.3%) in the MUC1 group [adjusted relative risk (aRR), 0.83; 95% confidence interval (CI), 0.60-1.14; P = 0.25]. Adenoma recurrence occurred in 3/11 (27.3%) immune responders at week 12 and week 55 (aRR, 0.41; 95% CI, 0.15-1.11; P = 0.08 compared with placebo). There was no difference in serious adverse events.

CONCLUSIONS

An immune response was observed only in vaccine recipients. Adenoma recurrence was not different than placebo, but a 38% absolute reduction in adenoma recurrence compared with placebo was observed in participants who had an immune response at week 12 and with the booster injection.

Abstract 6537: Single cell transcriptomics uncovers cellular and molecular differences in PBMCs of responders and non-responders to the MUC1 cancer vaccine given in the preventative setting

Introduction: A single arm trial (NCT007773097) and a double-blind, placebo controlled randomized trial (NCT02134925) were conducted in patients with newly diagnosed advanced colonic adenomas to test the safety and immunogenicity of the MUC1 antigen vaccine and its potential to prevent new adenoma formation. These are the first trials of a non-viral cancer vaccine administered in the absence of cancer. In both trials, the vaccine was safe and strongly immunogenic in 43% and 25% of participants (Responders), respectively. The lack of robust response in a significant number of participants suggested, for the first time, that even in a premalignant setting, the immune system may have already been exposed to regulatory influences that, in the case of the vaccine, determine who does and who does not respond. We hypothesized that there could be molecular and cellular differences in the immune competence between vaccine responders and non-responders, and that they could be identified by studying their pre-vaccination peripheral blood mononuclear cells (PBMCs).

Methods: The two MUC1 vaccine trials are described in https://doi.org/10.1101/2022.10.05.22280474 and https://doi.org/10.1158%2F1940-6207.CAPR-12-0275. We performed single cell RNA-sequencing (scRNAseq) on banked pre-vaccination PBMCs from 16 Responders and 16 Non-Responders, determined by anti-MUC1 IgG response. Using differential gene expression (DGE), pathway enrichment, and network estimation analyses, we identified specific cell types, genes, and pathways that differ between responders and non-responders.

Results: Pre-vaccination PBMCs from Responders contained a significantly higher percentage of CD4+ naive T cells, while Non-Responders showed significantly higher percentage of CD8+ T effector memory (TEM) cells and a higher percentage of CD16+ monocytes. DGE and gene interaction network analysis showed a higher level of expression of T cell activation genes, such as Fos and Jun, in the CD4+ naive T cells in Responders. Further network analysis showed that these genes were directly connected to response. We also found pre-vaccination specific gene ontology (GO) pathways for translational and transcriptional activity enriched in all cell types in Responders compared to Non-Responders.

Conclusion: Our analyses identified candidate biomarkers that are predictive of a preventative cancer vaccine response. Thus, our results can be used for patient selection for vaccine administration. Furthermore, we identified cell type differences and transcriptional pathways that provide information of possible mechanisms of vaccine response.

Citation Format: Daniel Y. Yuan, Michelle L. McKeague, Matthew T. Dracz, Olivera J. Finn, Panayiotis V. Benos. Single cell transcriptomics uncovers cellular and molecular differences in PBMCs of responders and non-responders to the MUC1 cancer vaccine given in the preventative setting [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6537.

Abstract 2875: Evidence of immunosuppression in patients with breast ductal carcinoma in situ

Introduction: Ductal carcinoma in situ (DCIS) is a noninvasive precursor to invasive breast cancer. Although not all DCISlesions progress to cancer, most DCIS are treated as early breast cancer, given the uncertainty of which lesions will progress. The current increase in the incidence of DCIS has sparked interest in the immune contexture of the DCIS lesions as well as the immune status of DCIS patients, as a means to predict which DCIS lesions will progress to cancer. Studies done so far in invasive breast cancer showed that the immune system can mediate both tumor-promoting influence (via T regulatory (Treg) cells, M2 macrophages, myeloid-derived suppressor cells (MDSCs)), as well as tumor-suppressing influences (via CD8+ and CD4+ effector T cells, natural killer cells (NK), M1 macrophages, tissue-resident memory T (Trm) cells, B cell and dendritic (DCs) cells). Similar studies are still lacking in DCIS. Our aim was to start closing the gap in our understanding of the DCIS immune microenvironment, which will pave the way for novel preventative and therapeutic strategy.

Methods: We analyzed by flow cytometry peripheral blood mononuclear cells (PBMCs) from newly diagnosed DCIS patients for the presence of various immune cell types expressing specific phenotypic markers of immune effectors or immune suppressors and compared them with PBMC from age-matched healthy individuals.

Results: We found a statistically significant increase in the frequency of FoxP3+ regulatory T cells in DCIS PBMC compared with healthy controls. There was also a significant increase in Tim-3+CD8+ T effector memory cells (P= 0.035) and Tim-3+ CD8+ NKT cells (P = 0.033) in the PBMCs of patients with DCIS compared with healthy controls. T cells expressing other exhaustion markers, such as PD-1+ and LAG-3+ were present at very low levels in both groups.

Conclusion: Our results suggest that some of the many immunosuppressive mechanisms seen in patients with invasive breast cancer, such as regulatory T cells, are already present in pre-cancer DCIS. Evidence of the beginning of immune suppression is also reflected in the increased frequency of CD4+ and CD8+ T cells expressing the exhaustion marker Tim-3.

Citation Format: Sedigheh Taghinezhad-S, Amir Hossein Mohseni, Pamela L. Beatty, Leisha A. Emens, Olivera J. Finn. Evidence of immunosuppression in patients with breast ductal carcinoma in situ [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2875.

Abstract PR002: A pilot study of a MUC1 vaccine in current and former smokers at high risk for lung cancer

Background: Smoking is the most common etiology for lung cancer and smoking cessation does not eliminate the risk. An emerging area of interest for risk reduction is immunoprevention. MUC1 glycoprotein is aberrantly expressed in adenocarcinomas, including lung cancer and their premalignant lesions. MUC1 vaccine in the premalignant or high-risk setting may be effective in halting neoplastic development and progression. Trial design: Through the NCI-funded Cancer Prevention Network (CPN), we conducted a two-center pilot trial to evaluate immunogenicity of the MUC1 vaccine (assessed at 12 weeks), and safety (assessed at up to 24 weeks) in current and former heavy smokers. 87 participants were screened in order to have at least 40 evaluable for baseline and 12-week immunogenicity assessments. Smoking history of ≥30 pack-years and either current (still smoking or quit &lt; 1 year prior to pre-registration) or former smoker (quit 1-15 years prior to pre-registration); ages 55-80 years; ECOG performance status ≤1; CT scan of the chest done ≤ 6 months prior to pre-registration showing either negative findings (no nodules) or solid or part-solid nodules &lt; 6 mm in size (consistent with &lt; 1% probability of malignancy, Lung-RADs Version 1.0). Exclusion criteria were standard for lung cancer screening. Methods: MUC1 peptide plus polyICLC adjuvant (Hiltonol) vaccine was given at week 0, 2 and 10. Blood was collected for safety tests and immune assays pre and 2 weeks post each vaccine, and at week 24. Anti-MUC1 IgG titer was evaluated by ELISA. Based on previous studies of this vaccine, 40 evaluable participants would provide 96% power to detect immune response rate of 15% versus 40%, using a 2-sided test of proportions with type I error rate of 0.05. PBMC were assayed for the presence of regulatory T cells (Treg) and myeloid derived suppressor cells (MDSC) (secondary endpoint). Circulating levels of inflammatory cytokines and hsCRP were evaluated using commercially available tests (exploratory endpoint). AEs and toxicities were monitored for up to 24 weeks from the first vaccine. Results: 87 individuals were screened and 50 registered. 45 completed the study, 26 current and 19 former smokers (time since last smoked: average 7.8 years; 11 months -13 years). The vaccine was well-tolerated with injection site reactions being the most common AE. Immune response to the vaccine was lower than expected, with 2 current and 2 former smokers developing anti-MUC1 IgG titers ≥2 fold higher at week 12 over baseline (10%). We found high circulating levels of MDSCs in PBMC of both current and former smokers and very low or no serum cytokines. Conclusions: A preventative vaccine trial was feasible in individuals at high risk for lung cancer. However, we discovered a high level of immune suppression, previously documented only in advanced lung cancer. Mitigating the development of lung cancer in heavy smokers through vaccine administration may be limited by related immunosuppression.

Citation Format: Olivera J. Finn, Julie Ward, Tami Krpata, Samantha Fatis, John McKolanis, Jia Xue, Pamela Beatty, Camille Jacqueline, Sharon Kaufman, Colleen Akerley, April Felt, Karrie Fursa, Anne Holland, Liz S. Ambulay, Nathan Foster, Ryan McMurray, Carrie Strand, Andres M. Salazar, Lisa Bengtson, Eva Szabo, Paul Limburg, Malgorzata Wojtowicz, David E. Midthun, Arjun Pennathur. A pilot study of a MUC1 vaccine in current and former smokers at high risk for lung cancer. [abstract]. In: Proceedings of the AACR Special Conference: Precision Prevention, Early Detection, and Interception of Cancer; 2022 Nov 17-19; Austin, TX. Philadelphia (PA): AACR; Can Prev Res 2023;16(1 Suppl): Abstract nr PR002.

Abstract LB179: Patient-derived, vaccine-elicited, anti-MUC1 antibodies directly target tumor cells for elimination via multiple immune mechanisms

During premalignant and malignant transformation, cells undergo antigenic changes that can be recognized by the immune system, and this can be leveraged both for immune prevention and therapy. One such change occurs with MUC1, or Mucin-1, a large variable number tandem repeat (VNTR)-containing transmembrane protein that is overexpressed and hypoglycosylated on a majority of precancerous and adenocarcinoma cells, including those of the colon, lung, breast, pancreas and ovaries. This tumor form of MUC1 is recognized by both cellular and humoral immunity. Healthy individuals at high risk of developing colon cancer due to a history of colonic polyps were enrolled in a clinical trial testing the feasibility of prophylactic vaccination against the tumor form of MUC1, also expressed on polyps (Kimura et al., 2013). Half the participants generated high levels of anti-MUC1 IgG antibodies, some of which were cloned to further analyze their tumor specificity and to potentially develop them as therapeutics for patients with cancer (Lohmueller et al., 2016). As these fully human IgG1 monoclonal antibodies (mAbs) were selected and affinity matured in healthy individuals who experienced no negative side effects to the vaccine in &gt;10 years, it increases the likelihood that as therapeutics they will be safe. To study anti-tumor efficacy and mechanism(s) of action of 12 of these mAbs, tumor cells were co-incubated with immune cells in the presence of the mAbs, and each mAb’s ability to mediate antibody-dependent cellular cytotoxicity (ADCC) by NK cells, antibody-dependent cellular phagocytosis (ADCP) by monocytes, antibody-dependent trogocytosis/trogoptosis (ADCT) by neutrophils, antibody-dependent cytokine release (ADCR) and complement dependent cytotoxicity (CDC) was assessed. Several MUC1 mAbs examined could mediate ADCC, ADCP, ADCT and ADCR, with some mechanisms being cell-line dependent. One mAb was selected for in vivo testing and found to delay breast cancer growth and prolong survival in immunocompromised mice lacking T cells, B cells and NK cells, pointing to ADCP and ADCT as important anti-tumor functions. Additionally, the relationship between epitope location and immune effector functions was explored by creating different MUC1 constructs that vary epitope distance from the cell surface, number of epitopes, etc, to test properties of the target antigen that may affect antibody efficacy. These latter experiments revealed an increased efficiency in phagocytosis and trogocytosis when the mAbs bound an epitope that was both proximal to and anchored to the membrane. Notably, unlike published studies of rituximab and alemtuzumab, the amount of MUC1 mAb binding did not always correlate with increased effector function. Our results may inform not only the development of these MUC1-based therapies but more broadly future therapeutic mAb design against a variety of targets.

Citation Format: Michelle L. McKeague, Jason Lohmueller, Matthew T. Dracz, Najla Saadallah, Jia Xue, Eric D. Ricci, William Lu, Olivera J. Finn. Patient-derived, vaccine-elicited, anti-MUC1 antibodies directly target tumor cells for elimination via multiple immune mechanisms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB179.

Cancer vaccines

Given the renewed interest in vaccine development sparked by the COVID-19 pandemic, we are revisiting the current state of vaccine development for cancer prevention and treatment. Experts discuss different vaccine types, their antigens and modes of action, and where we stand on their clinical development, plus the challenges we need to overcome for their broad implementation.

The "Great Debate" at Immunotherapy Bridge 2021, December 1st-2nd, 2021

As part of the 2021 Immunotherapy Bridge virtual congress (December 1–2, Naples, Italy), the Great Debate sessions featured experts who were assigned counter opposing views on four important questions in immunotherapy today. The first topic was whether oncolytic viruses or other specific immunomodulators were the more promising approach for intralesional therapy. The second was whether early surrogate endpoints, such as response rate or progression-free survival, correlate with long-term overall survival was considered. Thirdly, whether vaccines can transform cold into hot tumors was discussed and, finally, broad versus deep analytic profiling approaches to gain insights into immune-oncology development were compared. As with previous Bridge congresses, presenters were invited by the meeting Chairs and positions taken during the debates may not have reflected their respective personal view. In addition, the views summarised in this article are based on available evidence but may reflect personal interpretation of these data, clinical experience and subjective opinion of the speaker.

Identification of Cell Surface Molecules That Determine the Macrophage Activation Threshold Associated With an Early Stage of Malignant Transformation

The ability of immune cells to sense changes associated with malignant transformation as early as possible is likely to be important for the successful outcome of cancer immunosurveillance. In this process, the immune system faces a trade-off between elimination of cells harboring premalignant or malignant changes, and autoimmune pathologies. We hypothesized that the immune system has therefore evolved a threshold for the stage of transformation from normal to fully malignant cells that first provides a threat (danger) signal requiring a response. We co-cultured human macrophages with a unique set of genetically related human cell lines that recapitulate successive stages in breast cancer development: MCF10A (immortalized, normal); MCFNeoT (benign hyperplasia); MCFT1 (atypical hyperplasia); MCFCA1 (invasive cancer). Using cytokines-based assays, we found that macrophages were inert towards MCF10A and MCFNeoT but were strongly activated by MCFT1 and MCFCA1 to produce inflammatory cytokines, placing the threshold for recognition between two premalignant stages, the earlier stage MCFNeoT and the more advanced MCFT1. The cytokine activation threshold paralleled the threshold for enhanced phagocytosis. Using proteomic and transcriptomic approaches, we identified surface molecules, some of which are well-known tumor-associated antigens, that were absent or expressed at low levels in MCF10A and MCFNeoT but turned on or over-expressed in MCFT1 and MCFCA1. Adding antibodies specific for two of these molecules, Annexin-A1 and CEACAM1, inhibited macrophage activation, supporting their role as cancer "danger signals" recognized by macrophages.

Beneficial autoimmunity improves cancer prognosis

Many tumour antigens that do not arise from cancer cell-specific mutations are targets of humoral and cellular immunity despite their expression on non-malignant cells. Thus, in addition to the expected ability to detect mutations and stress-associated shifts in the immunoproteome and immunopeptidome (the sum of MHC class I-bound peptides) unique to malignant cells, the immune system also recognizes antigens expressed in non-malignant cells, which can result in autoimmune reactions against non-malignant cells from the tissue of origin. These autoimmune manifestations include, among others, vitiligo, thyroiditis and paraneoplastic syndromes, concurrent with melanoma, thyroid cancer and non-small-cell lung cancer, respectively. Importantly, despite the undesirable effects of these symptoms, such events can have prognostic value and correlate with favourable disease outcomes, suggesting 'beneficial autoimmunity'. Similarly, the occurrence of dermal and endocrine autoimmune adverse events in patients receiving immune-checkpoint inhibitors can have a positive predictive value for therapeutic outcomes. Neoplasias derived from stem cells deemed 'not essential' for survival (such as melanocytes, thyroid cells and most cells in sex-specific organs) have a particularly good prognosis, perhaps because the host can tolerate autoimmune reactions that destroy tumour cells at some cost to non-malignant tissues. In this Perspective, we discuss examples of spontaneous as well as therapy-induced autoimmunity that correlate with favourable disease outcomes and make a strong case in favour of this 'beneficial autoimmunity' being important not only in patients with advanced-stage disease but also in cancer immunosurveillance.

Abstract 1763: Acute but not chronic LCMV infection generates immunity against abnormally expressed self-antigens on infected and tumor cells and protects against lung and lymphoid cancers in mice

Therapeutic cancer vaccines have been tested for years but showed limited immunogenicity and clinical efficacy mainly because of the immunosuppressive environment generated by tumors. One approach for improving cancer vaccine efficacy would be to use them prior to cancer occurrence to strengthen immunosurveillance. This would ensure cancer elimination at the earliest stages of carcinogenesis and avoid cancer editing and escape. However, identifying antigens that can be incorporated into safe and effective prophylactic cancer vaccines remains a major challenge. Best candidates would be shared tumor-associated antigens (TAA) that are reproducibly and stably expressed on advanced tumors and premalignant lesions but not on normal tissues and that would induce antibodies and T cells causing tumor rejection without danger of autoimmunity. Antibodies and T cells specific for some well-known TAA have been found in individuals without cancer but with a history of acute infections and this pre-existing immunity has been associated with lowered lifetime risk for developing cancer while causing no obvious toxicity. We hypothesized that those immune responses were generated to self-antigens that are abnormally expressed on infected cells and again later on tumor cells, which we named disease-associated antigens (DAA)/tumor associated antigens (TAA), DAA/TAA. We tested this hypothesis here using two strains of lymphocytic choriomeningitis virus (LCMV): Armstrong (Arm) strain and CL-13 that cause acute and chronic infection in mice, respectively. Both strains elicited antibodies that recognized antigens on mouse lung (LLC) and lymphoid (EL4) tumors. Mice were later injected with tumor cells and Arm-infected mice controlled tumor challenge better than naïve controls, whereas the Cl-13 infection in mice had either no effect or promoted tumor growth. We characterized 5 DAA/TAA that were targets of this virus infection-elicited anti-tumor immunity using immunoprecipitation followed by 2D DIGE and mass spectrometry. Our results suggest that a vaccine based on DAA/TAA that are expressed on tumors and infected cells could confer protection against both cancer and a viral infection. Accordingly, we are currently immunizing mice with peptides derived from the 5 DAA/TAA. Mice responding to the vaccine will be given either tumors or LCMV and we will measure their response to both and the immune effector mechanisms mediating the response.

Citation Format: Camille Jacqueline, Sarah Boothman, Jonathan S. Minden, Olivera J. Finn. Acute but not chronic LCMV infection generates immunity against abnormally expressed self-antigens on infected and tumor cells and protects against lung and lymphoid cancers in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1763.

Identification of a macrophage activation threshold associated with malignant transformation and the sensing of candidate “danger signals”

Cancer immunosurveillance is based on the recognition of changes brought by malignant transformation of normal cells, leading to their elimination, immunoediting, or escape. The ability of immune cells to sense changes associated with malignant transformation as early as possible is likely to be important for the successful outcome of cancer immunosurveillance. In this process, the immune system faces a trade-off between elimination of cells harboring premalignant or malignant changes, and autoimmune pathologies. We hypothesized that the immune system has therefore evolved a threshold for distinguishing normal from abnormal cells, perhaps similar to a pathogen recognition threshold at which macrophages distinguish non-dangerous from dangerous microbes. We co-cultured human macrophages with a unique set of genetically related human cell lines that recapitulate breast cancer development: MCF10A (immortalized); MCFneoT (hyperplasia); MCFT1 (atypical hyperplasia); MCFCA1 (invasive cancer). Using cytokines-based assays, we found that the threshold for macrophage activation was between MCFNeoT and MCFT1, with macrophages co-cultured with the atypical hyperplasia and invasive cancer cell lines showing an inflammatory cytokine response. This response was accompanied by an increase in macrophage migration, phagocytosis and capacity to infiltrate MCFT1 spheroids. We are currently validating candidates for “danger signals” that will be shared by MCFT1 and MCFCA1 but absent or expressed at low level in the early state of premalignancy. Using proteomic and transcriptomic approaches, we identified 13 surface or secreted molecules corresponding to this definition, some of which are well-known tumor-associated antigens.

The "Great Debate" at Immunotherapy Bridge 2020, December 3rd, 2020

As part of the 2020 Immunotherapy Bridge virtual congress (December 2nd–3rd, Italy), the Great Debate session featured counterpoint views from leading experts on three clinical questions in immunotherapy today. The first of these was whether antitumoral vaccination is still a treatment option. The second topic debated whether anti-programmed death (PD)-1/PD-ligand (L)1 blockade should be the backbone for immunotherapy combination. Finally, the use of innovative study designs and surrogate endpoints was considered from both an academic and industry perspective. For each topic, two experts presented the argument and counter-argument in support of two different points of view. As with previous Bridge congresses, the debates were assigned by meeting Chairs and positions taken by experts during the debates may not have necessarily reflected their respective personal view. The views summarised in this article are based on available evidence but may reflect personal interpretation of these data, clinical experience and subjective opinion of the speaker.

Prevention of colitis-associated colon cancer using a vaccine to target abnormal expression of the MUC1 tumor antigen

Association between chronic inflammation and cancer development is exemplified by inflammatory bowel disease (IBD) where patients with chronic uncontrolled colitis have a significantly increased risk of developing colitis-associated colorectal cancer (CACC). CACC appears to progresses through the inflammation-dysplasia-carcinoma sequence. This highlights the need to identify targets and interventions that reduce inflammation and prevent development of dysplasia in the context of IBD. Using the dextran sulfate sodium (DSS) mouse model of chronic colitis and CACC, we show that an important target of intervention in human disease would be the epithelial cell molecule MUC1 that is aberrantly expressed on inflamed colonocytes and promotes inflammation and progression to CACC. We show that a MUC1 vaccine can ameliorate chronic colitis and prevent development of dysplasia in the colon and thus extend survival in human MUC1 transgenic mice. This study supports the potential of prophylactic vaccines to target antigens that become aberrantly expressed in chronic inflammation (e.g., IBD) and continue to be expressed on the associated cancers (e.g., colon cancer), to prevent and/or treat both diseases.

Altered Expression of the Epithelial Mucin MUC1 Accompanies Endoscopic Recurrence of Postoperative Crohn's Disease

BACKGROUND

MUC1-glycoprotein is expressed at low levels and in fully glycosylated form on epithelial cells. Inflammation causes MUC1 overexpression and hypoglycosylation. We hypothesized that overexpression of hypoglycosylated MUC1 would be found in postoperative Crohn's disease (CD) recurrence and could be considered an additional biomarker of recurrence severity.

METHODS

We examined archived neo-terminal ileum biopsies from patients with prior ileocecal resection who had postoperative endoscopic assessment of CD recurrence and given a Rutgeerts ileal recurrence score. Consecutive tissue sections were stained using 2 different anti-MUC1 antibodies, HMPV that recognizes all forms of MUC1 and 4H5 that recognizes only inflammation-associated hypoglycosylated MUC1.

RESULTS

A total of 71 postoperative CD patients were evaluated. There was significant increase in MUC1 expression of both glycosylated/normal (P<0.0001) and hypoglycosylated/abnormal (P<0.0001) forms in patients with severe endoscopic CD recurrence (i3+i4), ileal score i2, compared with patients in endoscopic remission (i0+i1). Results were similar regardless of anti-TNF-α use. Although MUC1 expression and Rutgeerts scores were in agreement when characterizing the majority of cases, there were a few exceptions where MUC1 expression was characteristic of more severe recurrence than implied by Rutgeerts score.

CONCLUSIONS

MUC1 is overexpressed and hypoglycosylated in neo-terminal ileum tissue of patients with postoperative CD recurrence. Increased levels are associated with more severe endoscopic recurrence scores, and this is not influenced by anti-TNF-α use. Discrepancies found between Rutgeerts scores and MUC1 expression suggest that addition of MUC1 as a biomarker of severity of postoperative CD recurrence may improve categorization of recurrence status and consequently treatment decisions.

Inflammation-Induced Abnormal Expression of Self-molecules on Epithelial Cells: Targets for Tumor Immunoprevention

Tumor-associated antigens (TAA) are self-molecules abnormally expressed on tumor cells, which elicit humoral and cellular immunity and are targets of immunosurveillance. Immunity to TAAs is found in some healthy individuals with no history of cancer and correlates positively with a history of acute inflammatory and infectious events and cancer risk reduction. This suggests a potential role in cancer immunosurveillance for the immune memory elicited against disease-associated antigens (DAA) expressed on infected and inflamed tissues that are later recognized on tumors as TAAs. To understand probable sources for DAA generation, we investigated in vitro the role of inflammation that accompanies both infection and carcinogenesis. After exposure of normal primary breast epithelial cells to proinflammatory cytokines IL1β, IL6, and TNFα, or macrophages producing these cytokines, we saw transient overexpression of well-known TAAs, carcinoembryonic antigen and Her-2/neu, and overexpression and hypoglycosylation of MUC1. We documented inflammation-induced changes in the global cellular proteome by 2D difference gel electrophoresis combined with mass spectrometry and identified seven new DAAs. Through gene profiling, we showed that the cytokine treatment activated NF-κB and transcription of the identified DAAs. We tested three in vitro-identified DAAs, Serpin B1, S100A9, and SOD2, and found them overexpressed in premalignant and malignant breast tissues as well as in inflammatory conditions of the colon, stomach, and liver. This new category of TAAs, which are also DAAs, represent a potentially large number of predictable, shared, immunogenic, and safe antigens to use in preventative cancer vaccines and as targets for cancer therapies.

Inflammation-induced tumor antigen expression on epithelial cells reveals the mechanism of their generation and provides a system for identification of new tumor targets

Tumor-associated antigens (TAAs) are self-molecules abnormally expressed on tumor cells that elicit humoral and cellular immunity and are targets of effective cancer immunosurveillance. Surprisingly, immunity to TAAs is found in many healthy individuals with no history of cancer. We previously showed that other events in addition to cancer, such as viral and bacterial infections, can cause the expression of some TAAs and correlate with effective tumor immunosurveillance. We are now testing in mice the ability of two LCMV strains, one that causes acute (Armstrong) and one that causes chronic (Cl-13) infection, to elicit expression of and immune memory to TAAs and protect from a later tumor challenge. We observed that infection with the acute strain elicits immunity to specific TAAs expressed by two tumor cell lines that were then used in tumor challenge experiments. So far, we were able to show a protective effect of a previous Armstrong infection against our model of lymphoid tumor (EL4). We also developed a highly reproducible in vitro model of acute inflammation of primary epithelial cells and confirmed that short-term exposure to pro-inflammatory cytokines IL-1β, IL-6 and TNF-α leads to abnormal expression of three well known TAAs, MUC1, CEA and HER2/neu. These cells were found to activate macrophages, which should promote antigen uptake and presentation of these and other TAAs. We have used this system and 2D Difference Gel Electrophoresis (2D-DIGE) combined with mass spectrometry to identified so far seven new TAAs. Because these TAAs are generated first as disease-associated antigens (DAAs), they represent highly predictable shared antigens for safe and effective preventative cancer vaccines.

Myeloid derived suppressor cells in cancer, premalignancy and inflammation: A roadmap to cancer immunoprevention

The ultimate success of any form of cancer therapy or cancer prevention depends on its ability to engage the power of the immune system to completely eliminate a growing tumor, lower the life-time tumor risk and establish long-term memory to prevent recurrence or future tumors. For that reason, all therapies but especially immunotherapies depend on the immune health (immunocompetence) of each treated individual. Cancer and chronic illnesses, combined with a usually more advanced age of cancer patients or those at risk for cancer are known to severely suppress multiple antitumor functions of the immune system. Understanding the critical mechanisms controlling and mediating immune suppression can lead to additional therapies to alleviate the effects of those mechanisms and improve the outcome of cancer therapy and prevention. We introduce and review here a highly immunosuppressive cell population found in cancer, precancer, and chronic inflammatory diseases, myeloid derived suppressor cells (MDSC). First described in the setting of advanced cancer, their presence and immunosuppressive activity has been seen more recently in early premalignant lesions and in chronic inflammatory diseases leading to cancer. We describe the detrimental effects of their presence on cancer immunotherapy, immunosurveillance and immunoprevention and review early attempts to develop drugs to eliminate them or reduce their negative impact.

Antibodies specific for disease-associated antigens (DAA) expressed in non-malignant diseases reveal potential new tumor-associated antigens (TAA) for immunotherapy or immunoprevention

Immune responses to a large number of mutated and non-mutated tumor antigens have been studied in an attempt to unravel the highly complex immune response to cancer. Better understanding of both the effectors and the targets of successful immunosurveillance can inform various immunotherapeutic approaches, which can strengthen or replace natural immunosurveillance that a tumor has managed to escape. In this review we highlight targets of antibodies generated in the context of diseases other than cancer, such as asthma, allergies, autoimmune disorders, inflammation and infections, where the antibody presence correlates either with an increased or a reduced lifetime risk of cancer. We focus on their target antigens, self-molecules abnormally expressed on diseased cells or cross-reactive with exogenous antigens and found on cancer cells as tumor associated antigens (TAA). We refer to them as disease-associated antigens (DAA). We review 4 distinct categories of antibodies according to their target DAA, their origin and their reported impact on cancer risk: natural antibodies, autoantibodies, long-term memory antibodies and allergy-associated antibodies. Increased understanding and focus on their specific targets could enable a more rational choice of antigens for both therapeutic and preventative cancer vaccines and other more effective and less toxic cancer immunotherapies.

Cross-talk between Colon Cells and Macrophages Increases ST6GALNAC1 and MUC1-sTn Expression in Ulcerative Colitis and Colitis-Associated Colon Cancer

Patients with ulcerative colitis have an increased risk of developing colitis-associated colon cancer (CACC). Changes in glycosylation of the oncoprotein MUC1 commonly occur in chronic inflammation, including ulcerative colitis, and this abnormally glycosylated MUC1 promotes cancer development and progression. It is not known what causes changes in glycosylation of MUC1. Gene expression profiling of myeloid cells in inflamed and malignant colon tissues showed increased expression levels of inflammatory macrophage-associated cytokines compared with normal tissues. We analyzed the involvement of macrophage-associated cytokines in the induction of aberrant MUC1 glycoforms. A coculture system was used to examine the effects of M1 and M2 macrophages on glycosylation-related enzymes in colon cancer cells. M2-like macrophages induced the expression of the glycosyltransferase ST6GALNAC1, an enzyme that adds sialic acid to O-linked GalNAc residues, promoting the formation of tumor-associated sialyl-Tn (sTn) O-glycans. Immunostaining of ulcerative colitis and CACC tissue samples confirmed the elevated number of M2-like macrophages as well as high expression of ST6GALNAC1 and the altered MUC1-sTn glycoform on colon cells. Cytokine arrays and blocking antibody experiments indicated that the macrophage-dependent ST6GALNAC1 activation was mediated by IL13 and CCL17. We demonstrated that IL13 promoted phosphorylation of STAT6 to activate transcription of ST6GALNAC1. A computational model of signaling pathways was assembled and used to test IL13 inhibition as a possible therapy. Our findings revealed a novel cellular cross-talk between colon cells and macrophages within the inflamed and malignant colon that contributes to the pathogenesis of ulcerative colitis and CACC.See related Spotlight on p. 160.

Abstract CT222: A pilot study of a MUC1 vaccine in current and former smokers at high risk for lung cancer

Background: Smoking is the most common etiology for lung cancer. Smoking cessation, even when successful, does not eliminate risk of lung cancer. With inconsistent results of lung chemoprevention trials, an emerging area of interest is immunoprevention, in particular vaccines. MUC1 is a transmembrane glycoprotein aberrantly overexpressed in adenocarcinomas, including lung cancer. Abnormal MUC1 expression is also characteristic of premalignant lesions, including bronchial dysplasia and atypical adenomatous hyperplasia. This suggests that immunization with a MUC1 vaccine in the premalignant or high-risk setting, before the tumor and cytotoxic therapy could suppress the immune system, might be effective in inducing strong immunity and reducing cancer risk.

Trial design: Leveraging the infrastructure of the NCI-funded Cancer Prevention Network (CPN) consortium, we are conducting a two-center pilot trial to evaluate co-primary endpoints: immunogenicity of the MUC1 peptide plus polyICLC adjuvant vaccine (assessed at 12 weeks) and safety (assessed at up to 24 weeks) in current and former smokers who are at high risk for lung cancer. 50 participants will be screened in order to have 40 evaluable participants for baseline and 12-week immunogenicity assessments.

Eligibility: Smoking history of ≥30 pack-years and either current smoker (still smoking or quit &lt; 1 year prior to pre-registration) or former smoker (quit 1-15 years prior to pre-registration); ages 55-80 years; ECOG performance status ≤1; CT scan of the chest done ≤ 6 months prior to pre-registration showing either negative findings (no nodules) or solid or part-solid nodules &lt; 6 mm in size (consistent with &lt; 1% probability of malignancy, Lung-RADs Version 1.0). Exclusion criteria are standard.

Immunogenicity and safety: MUC1 peptide plus polyICLC adjuvant vaccine will be administered at week 0, 2 and 10. The primary endpoint is anti-MUC1 IgG titer that is ≥2 fold higher at week 12 compared to baseline. Based on previous studies of this vaccine, we expect that 40 evaluable participants will provide 96% power to detect immunogenicity response rate of 15% versus 40% using a 2-sided test of proportions with type I error rate of 0.05. AEs and toxicities will be monitored for up to 24 weeks from the first vaccine.

Secondary Objectives: We will explore differences, if any, in vaccine immunogenicity in current vs. former smokers. Smoking induces chronic inflammation (hallmark of cancer) associated with immunosuppression. We will evaluate pre-vaccination levels of circulating myeloid derived suppressor cells (MDSC) and correlate with the response to the vaccine. We will explore the impact, if any, of this vaccine on the markers of inflammation (hsCRP, IL-6) and the effect of baseline levels of these markers on the ability to successfully vaccinate. We will also assess the relationship between COPD status and immune response in current versus former smokers.

The trial is open to accrual.

Citation Format: Olivera J. Finn, Julie Ward, Tami Krpata, Lisa Bengtson, John McKolanis, Sharon Kaufman, Colleen Akerley, April Felt, Karrie Fursa, Anne Holland, Nathan Foster, Andres Salazar, Malgorzata Wojtowicz, Eva Szabo, Paul Limburg, David Midthun, Arjun Pennathur. A pilot study of a MUC1 vaccine in current and former smokers at high risk for lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT222.

Circulating Myeloid Derived Suppressor Cells (MDSC) That Accumulate in Premalignancy Share Phenotypic and Functional Characteristics With MDSC in Cancer

Myeloid derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells that accumulate in circulation of cancer patients and at tumor sites where they suppress anti-tumor immunity. We previously reported that in a colon cancer prevention trial of a MUC1 vaccine tested in individuals at increased risk for colon cancer, those who did not mount immune response to the vaccine had higher pre-vaccination levels of circulating MDSC compared to those who did. We also reported that individuals with pancreatic premalignancy, Intraductal Papillary Mucinous Neoplasm (IPMN), had increased circulating levels of MDSC that inversely correlated with spontaneous antibody responses against the pancreatic tumor associated antigen MUC1, abnormally expressed on IPMN. Accumulation of MDSC in cancer and their immunosuppressive role had been well established but their presence in premalignancy was unexpected. In this study we compared MDSC in premalignancy with those in cancer with the hypothesis that there might be differences in the composition of various MDSC subpopulations and their immunosuppressive functions due to different lengths of exposure to disease and/or different tissue microenvironments. In cohorts of patients with premalignant polyps, colon cancer, premalignant IPMN, and pancreatic cancer, we confirmed higher levels of MDSC in premalignancy compared to healthy controls, higher levels of MDSC in cancer compared to premalignancy, but no difference in their subpopulation composition or immunosuppressive capacity. We show that levels of MDSC in premalignancy correlate negatively in vivo with spontaneous MUC1-specific antibody responses and in vitro with polyclonal T cell proliferation and IFN-γ secretion.

The cross-talk between infiltrating macrophages and inflamed or malignant colonic epithelium promotes overexpression of ST6GALNAC1 and epithelial MUC1 tumor form MUC1-sTn

Patients with inflammatory bowel disease (IBD) have an increased risk of developing colitis-associated colon cancer (CACC). Despite the strong relationship between inflammation and cancer, the mechanistic events that contribute to the transition from IBD to CACC remain undefined. Changes in the glycosylation profile of the known oncoprotein MUC1 commonly occur in chronic inflammation and may facilitate progression to cancer. We used a transwell coculture model system to examine the effect of polarized macrophages, such as those contributing to inflammation, on the expression of glycosylation-related enzymes in colon cancer cells. We found that M2-like macrophages induce the expression of ST6GALNAC1 glycosyltransferase which, by adding sialic acid to O-linked GalNAc residues, promotes the formation of the tumor-associated MUC1-sTn glycoform. Cytokine antibody arrays and blocking antibody experiments revealed that high levels of IL-13 and CCL17, present in the conditioned medium of colon cells cocultured with M2 macrophages, activate ST6GALNAC1 expression in colon cancer cells. In silico and in vivo murine and human models of colitis and CACC showed that IL-13 induces the phosphorylation of STAT-6 that directly binds ST6GALNAC1 promoter resulting in its transcription activation and protein over-expression. On the other hand, CCL17 activates ST6GALNAC1 expression via NF-kB pathway signaling. Our findings revealed a novel cross-talk between M2-like macrophages and inflamed and malignant colon cells that contributes to the pathogenesis of colitis and progression to CACC.

Covalent adaptor synNotch and chimeric antigen receptors (CARs) for programmable antigen targeting

Chimeric antigen receptors (CARs) are artificial T cell receptors that re-target patients’ T cells to specifically bind and kill tumor cells. Adoptive cell therapy with CAR T cells targeting CD19 has revolutionized treatment of refractory B cell acute lymphoblastic leukemia, and there is great interest in generating CAR T cells treating other cancers by targeting additional tumor antigens. Another promising class of engineered receptors are synthetic Notch (synNotch) receptors that can sense an antigen of interest on a neighboring cell and turn on expression of any transgene(s) of interest. To expand the targeting capabilities of these receptors, we have developed “universal” CAR and SynNotch receptors whose antigen-specificity can be re-directed by co-administered tumor-specific antibodies. Instead of directly targeting a tumor antigen, our universal receptors contain the SNAPtag self-labeling enzyme, which reacts with antibodies conjugated to benzylguanine (BG) to post-translationally assemble complete covalently associated antigen receptors. We demonstrate that the activation of SNAP CAR and SNAP-SynNotch receptors can be successfully re-targeted by several clinically relevant antibodies including: Rituximab, FMC63, Herceptin, and Cetuximab. SNAP-SynNotch cells demonstrate potent transgene activation, and SNAP-CAR T cells are capable of performing effector functions in a BG-antibody-directed antigen-specific manner. Additionally, the receptor response is titratable by BG-antibody dose. Finally, a continuous mathematical model was constructed to describe and optimize system activity. SNAP synNotch and SNAP CAR T cells provide a powerful new strategy to retarget engineered cells to multiple antigens.

Patient-derived, vaccine-elicited MUC1 antibodies mediate immune effector functions against cancer cells

Cancer cells undergo changes that the immune system recognizes, and this can be leveraged for therapy. Antibodies specific for such changes can exert anti-tumor effects via multiple mechanisms, including blocking oncogenic signaling, serving as Trojan horses carrying toxic compounds, coordinating innate immune engagement for cytotoxicity through cellular and non-cellular means, and promoting antigen uptake to jumpstart adaptive immunity for durable protection. We analyzed 12 high-affinity fully human IgG1 monoclonal antibodies that recognize a tumor-specific hypoglycosylated form of Mucin-1 (MUC1) that is overexpressed in &gt;80% of all cancers. These antibodies are unique and different from humanized murine anti-MUC1 mAbs, having undergone selection and affinity maturation in individuals receiving the MUC1-100mer peptide vaccine (Lohmueller et al. Sci. Rep. 2016). Importantly, in all vaccinated individuals that generated antibodies to MUC1, there have been no adverse events in 8 years, increasing the likelihood that as therapeutic agents they would be safe. To test their immune effector capacity, we used these human anti-MUC1 antibodies in in vitro antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP) and complement-dependent cytotoxicity (CDC) assays with different huMUC1-expressing cell lines, immune effector cells and serum. Several of the anti-MUC1 antibodies can mediate ADCC by NK cells and ADCP by macrophages, although there was very little or no CDC function. Notably, unlike in published studies on rituximab and alemtuzumab, the amount of antibody binding to cancer cells (MUC1) did not always correlate with increased effector function.

Is It Possible to Develop Cancer Vaccines to Neoantigens, What Are the Major Challenges, and How Can These Be Overcome? Neoantigens: Nothing New in Spite of the Name

The term "neoantigen," as applied to molecules newly expressed on tumor cells, has a long history. The groundbreaking discovery of a cancer causing virus in chickens by Rous over 100 years ago, followed by discoveries of other tumor-causing viruses in animals, suggested a viral etiology of human cancers. The search for other oncogenic viruses in the 1960s and 1970s resulted in the discoveries of Epstein-Barr virus (EBV), hepatitis B virus (HBV), and human papilloma virus (HPV), and continues until the present time. Contemporaneously, the budding field of immunology was posing the question can the immune system of animals or humans recognize a tumor that develops from one's own tissues and what types of antigens would distinguish the tumor from normal cells. Molecules encoded by oncogenic viruses provided the most logical candidates and evidence was quickly gathered for both humoral and cellular recognition of viral antigens, referred to as neoantigens. Often, however, serologic responses to virus-bearing tumors revealed neoantigens unrelated to viral proteins and expressed on multiple tumor types, foreshadowing later findings of multiple changes in other genes in tumor cells creating nonviral neoantigens.

A Believer's Overview of Cancer Immunosurveillance and Immunotherapy

The field of tumor immunology has grown around the idea that one of the important roles of the immune system is to eliminate cancer. This idea was difficult to reconcile with the accepted notion that the immune system evolved to distinguish self from nonself and therefore tumors derived from self-tissues would not be recognized. Lack of appropriate animal models prevented experimental testing of cancer immunosurveillance. This changed with the realization that the immune system evolved to recognize danger and with the advent of mouse models deficient in one or more immune function, which showed predicted increases in susceptibility to cancer. Simultaneously, technical advances that enabled the study of the human immune system provided data for the existence of tumor-specific T cells and Abs and led to molecular identification of tumor Ags, fully validating the cancer immunosurveillance hypothesis. Immunotherapy designed to strengthen cancer immunosurveillance has achieved unprecedented clinical successes.

Abstract 5643: TCRβ repertoire analysis from a prophylactic MUC1 cancer vaccine trial

Mucin 1 (MUC1) is a large transmembrane glycoprotein that is overexpressed and hypoglycosylated in many adenocarcinomas, including colon cancer. In the hypoglycosylated state, the peptide core of the 20aa variable number of tandem repeats (VNTR) region is exposed, allowing it to function as an altered-self ligand for antibodies and T cells. VNTR peptides have been previously used as antigens in therapeutic cancer vaccines. A clinical trial was conducted to test immunogenicity and safety of a MUC1 100mer VNTR peptide+polyICLC adjuvant vaccine in a prophylactic setting in patients with premalignant colon adenomas who were at high risk for later developing colon cancer. In this premalignant setting, where patients were expected to have fewer immunosuppressive countermeasures usually present in patients with cancer, nearly half of the individuals generated IgG antibodies with no noted adverse effects. Because the antibody response was isotype-switched, it suggested simultaneous T cell activation. To determine whether changes in T cell clonal abundance following immunization could be detected, we sequenced and analyzed TCRβ repertoires from PBMCs of 21 antibody-responders collected before and after both primary and one-year booster vaccinations. Of the patients analyzed, we identified 8 TCRβ sequences from three patients that were significantly elevated after both priming and boosting immunizations, potentially identifying T cell clones that expanded in response to the vaccine. 16 TCRβ sequences from four individuals were significantly decreased at both time points, potentially identifying T cell clones that left circulation to participate in immune responses in secondary lymphoid organs or tissues. The timing of blood collection at two weeks post immunization may have been too late to allow us to detect all of the vaccine-expanded clones before they left circulation. In summary, we found 24 TCRβ CDR3 sequences from 7/21 vaccine responders that significantly changed in frequency after both primary and booster vaccinations. TCR sequencing studies from patients' T cells expanded in vitro with MUC1 peptide will be performed to determine if they overlap with those sequenced ex vivo.

Citation Format: Michelle L. Miller, Jason Lohmueller, John R. McKolanis, Robert Schoen, Olivera J. Finn. TCRβ repertoire analysis from a prophylactic MUC1 cancer vaccine trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5643.

Abstract LB-305: Randomized, double-blind, placebo-controlled immunoprevention trial with MUC1 vaccine in patients with newly diagnosed advanced adenomas

Background: Immunotherapy targeting tumor-associated antigens aberrantly expressed on colorectal cancers and adenomatous polyps offers the potential for a relatively non-invasive and non-toxic prevention strategy, and because of the specificity of the immune response and its long-term memory, the potential for prolonged protection. In a double-blind randomized trial in patients with a diagnosis of advanced colorectal adenomas within the previous year, we are evaluating MUC1 vaccine with the TLR-3 agonist polyICLC (Hiltonol®) as an adjuvant, for its immunogenicity and effect on colorectal adenoma recurrence at follow up colonoscopy.

Aim: We report on a primary endpoint, MUC1 immunogenicity at week 12 (following vaccine or placebo administration at 0, 2, and 10 weeks), and on determinants of the immune response and vaccine toxicity.

Methods: Subjects with an advanced adenoma (defined as ≥1cm, tubulovillous or villous histology, or with HGD) were randomized. Response to the vaccine was assessed by monitoring IgG anti-MUC1 antibody titer ratio; defined as t12/t0, where t0 is the initial titer measured prior to vaccination, and t12 is the titer drawn at 12 weeks. A ratio of 2.0 was used as the primary definition of a significant immune response. T Regulatory and myleoid derived suppressor cell (MDSC) levels at baseline were assessed in relation to vaccine response. Adverse events (AEs) were recorded according to NCI Common Terminology Criteria for Adverse Events (CTCAE) version 4.0.

Results: 102 subjects were randomized at 6 centers, 52 received MUC1 vaccine and 50 placebo. Subjects had a mean age of 59.4±7.0 (range 40-70) years, 60.8% were male, 88.2% were white, and 18.6% Hispanic or Latino. At 12 weeks the IgG ratio was ≥2.0 in 13/52 (25%) of patients receiving vaccine (ratio range 2.9-17.3), vs. 0/50 in placebo group (P=.0001), and was

≥1.5 in 19/52 (36.5%) of patients receiving vaccine compared to 1/50 (2%) in placebo group (P&lt;.0001). In the vaccinated group, the IgG ratio was ≥2.0 in 45% of women (9/20) vs. 12.5% of men (4/32) (P=0.009) and ≥1.5 in 55% of women (11/20) vs. 25% of men (8/32) (P=0.03). In the vaccinated group, reduced levels of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) pre-vaccination were associated with response, 0.2±0.1 among responders (n=13) vs. 0.8±1.1 among non-responders (N=39) (p=0.0006) whereas monocytic MDSC and T regulatory cells (CD4+CD25, Foxp3) were not. There were no grade 3 adverse events (AE) possibly or probably related to the vaccine. The most common AE was an injection site reaction (grade 1 or 2) which occurred in 80.8% (n=42/52) in vaccine group vs. 6.0% in the placebo group (3/50).

Conclusions: Subjects with an advanced adenoma receiving MUC1 vaccine compared with a placebo are significantly more likely to develop an anti-IgG MUC1 immune response at 12 weeks. Women and subjects with lower circulating PMN-MDSC levels at baseline were more likely to respond. The vaccine was well tolerated. Follow up for the effect of the vaccine on adenomatous polyp recurrence is ongoing.

Citation Format: Robert E. Schoen, Lisa A. Boardman, Marcia Cruz-Correa, Ajay Bansal, Pamela L. Beatty, David Kastenberg, Chin Hur, Lynda Dzubinski, Luz Rodriguez, Andres Salazar, John McKolanis, Drew Seisler, Nathan R. Foster, May-Yin Polley, Paul J. Limburg, Olivera J. Finn. Randomized, double-blind, placebo-controlled immunoprevention trial with MUC1 vaccine in patients with newly diagnosed advanced adenomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-305.

Tumor-resident macrophages modulate intestinal barrier function through sialylation of Mucin 1 in IBD and colitis-associated cancer

Mucin 1 (MUC1) is a transmembrane glycoprotein overexpressed and hypoglycosylated in chronic inflammatory conditions and human adenocarcinoma compared to healthy tissues. We have reported that AOM/DSS-treated human MUC1.Tg mice showed higher tumor incidence and greater inflammation when compared to wild-type (WT) mice. Moreover, high expression levels of pro-inflammatory cytokines, including TNF-α and IL-6, were found in MUC1+ inflamed colon tissues and exogenous TNF-α promoted the transcriptional activity of MUC1 as well as over-expression of its hypoglycosylated form. As macrophages are the major source of TNF-α and IL-6, we analyzed infiltrating type 1 (M1) and type 2 (M2) macrophages into the inflamed and tumorigenic colon tissues. Immunofluorescence assay indicated increased presence of macrophages, and in particular CD206+ (M2), in inflamed colon tissues of MUC1.Tg mice compared to WT mice. In addition, immunostaining of macrophages in colon tissues from IBD patients showed expression of hypoglycosylated MUC1 and the presence of macrophages expressing CD163+, a human M2 marker. Interestingly, in vitro co-culture model system indicated that M1 and M2 polarized macrophages, induced different glycoforms of MUC1 in HT-29 colon cancer cells. In addition, macrophage-secreted factors modulated glycosyltrasferase enzymes, sush as ST6GalNAc1 and ST3GAL1, involved in O-glycan sialylation. We are currently dissecting the molecular basis by which macrophages induced hypoglycosylated and tumor forms of MUC1 during inflammation and colitis-associated cancer (CAC). Our findings will elucidate novel functions of tumor-associated macrophages in altering the intestinal barrier function in IBD and CAC.

Myeloid derived suppressor cells (MDSC) and anti-MUC1 immunosurveillance in pre-malignancy and cancer

Recent work from our lab showed that in a colon cancer prevention trial of a tumor antigen MUC1 vaccine in patients with premalignant colon adenomas, those who did not make anti-MUC1 IgG, had higher pre-vaccination levels of circulating MDSC compared to vaccine responders. This was the first observation of increased MDSC in premalignancy. MDSC in premalignancy have not been compared to MDSC in cancer and our hypothesis is that there might be differences in the composition of various MDSC subpopulation and their immunosuppressive functions due to the shorter time of exposure to disease and differences in the disease microenvironment. We are testing this hypothesis on two cohorts of patient samples, premalignant and malignant colon and pancreas. In both cohorts we saw an increase in MDSC in premalignant and malignant disease over healthy controls. The colon premalignant group could be divided into MDSChighAnti-MUC1 IgGlow and MDSClowAnti-MUC1 IgGhigh confirming our previous observations that MDSC are impeding anti-MUC1 immune response in premalignancy as well therefore potentially facilitating progression to cancer. The pancreas cohort also showed increase in MDSC in patients with pancreatic cysts (IPMN), precursors to pancreatic cancer, as well as their suppression of anti-tumor immunity. Furthermore, we found increased levels of PGE2 and its metabolite in patients’ serum from both cohorts, which is closely related to MDSC proliferation and mechanism of suppression. While we do not see much difference in the MDSC phenotype and subpopulation composition, the immunosuppressive capacity of tumor MDSC appears to be greater. We are currently testing this observation in vitro in T cell suppression assays.

Human Tumor Antigens Yesterday, Today, and Tomorrow

The question of whether human tumors express antigens that can be recognized by the immune system has been answered with a resounding YES. Most were identified through spontaneous antitumor humoral and cellular immune responses found in cancer patients and include peptides, glycopeptides, phosphopeptides, viral peptides, and peptides resulting from common mutations in oncogenes and tumor-suppressor genes, or common gene fusion events. Many have been extensively tested as candidates for anticancer vaccines. More recently, attention has been focused on the potentially large number of unique tumor antigens, mutated neoantigens, that are the predicted products of the numerous mutations revealed by exome sequencing of primary tumors. Only a few have been confirmed as targets of spontaneous immunity and immunosurveillance, and even fewer have been tested in preclinical and clinical settings. The field has been divided for a long time on the relative importance of shared versus mutated antigens in tumor surveillance and as candidates for vaccines. This question will eventually need to be answered in a head to head comparison in well-designed clinical trials. One advantage that shared antigens have over mutated antigens is their potential to be used in vaccines for primary cancer prevention. Cancer Immunol Res; 5(5); 347-54. ©2017 AACR.

Colorectal cancer prevention: Immune modulation taking the stage

Prevention or early detection is one of the most promising strategies against colorectal cancer (CRC), the second leading cause of cancer death in the US. Recent studies indicate that antitumor immunity plays a key role in CRC prevention. Accumulating evidence suggests that immunosurveillance represents a critical barrier that emerging tumor cells have to overcome in order to sustain the course of tumor development. Virtually all of the agents with cancer preventive activity have been shown to have an immune modulating effect. A number of immunoprevention studies aimed at triggering antitumor immune response against early lesions have been performed, some of which have shown promising results. Furthermore, the recent success of immune checkpoint blockade therapy reinforces the notion that cancers including CRC can be effectively intervened via immune modulation including immune normalization, and has stimulated various immune-based combination prevention studies. This review summarizes recent advances to help better harness the immune system in CRC prevention.

Abnormally glycosylated MUC1 establishes a positive feedback circuit of inflammatory cytokines, mediated by NF-κB p65 and EzH2, in colitis-associated cancer

The abnormal hypoglycosylated form of the epithelial mucin MUC1 is over-expressed in chronic inflammation and on human adenocarcinomas, suggesting its potential role in inflammation-driven tumorigenesis. The presence of human MUC1 aggravates colonic inflammation and increases tumor initiation and progression in an in vivo AOM/DSS mouse model of colitis-associated cancer (CAC). High expression levels of pro-inflammatory cytokines, including TNF-α and IL-6, were found in MUC1+ inflamed colon tissues. Exogenous TNF-α promoted the transcriptional activity of MUC1 as well as over-expression of its hypoglycosylated form in intestinal epithelial cells (IECs). In turn, hypoglycosylated MUC1 in IECs associated with p65 and up-regulated the expression of NF-κB-target genes encoding pro-inflammatory cytokines. Intestinal chronic inflammation also increased the expression of histone methyltransferase Enhancer of Zeste protein-2 (EzH2) and its interaction with cytokine promoters. Consequently, EzH2 was a positive regulator of MUC1 and p65-mediated IL-6 and TNF-α gene expression, and this function was not dependent on its canonical histone H3K27 methyltransferase activity. Our findings provide a mechanistic basis for already known tumorigenic role of the hypoglycosylated MUC1 in CAC, involving a transcriptional positive feedback loop of pro-inflammatory cytokines.

mSA2 affinity-enhanced biotin-binding CAR T cells for universal tumor targeting

Chimeric antigen receptor T cells (CAR-Ts) are promising cancer therapeutics. However, since cancer cells can lose the CAR-targeted antigen and avoid destruction, targeting multiple antigens with multiple CARs has been proposed. We illustrate here a less cumbersome alternative, anti-tag CARs (AT-CARs) that bind to tags on tumor-targeting antibodies. We have created novel AT-CARs, using the affinity-enhanced monomeric streptavidin 2 (mSA2) biotin-binding domain that when expressed on T cells can target cancer cells coated with biotinylated antibodies. Human T cells expressing mSA2 CARs with CD28-CD3ζ and 4–1BB-CD3ζ signaling domains were activated by plate-immobilized biotin and by tumor cells coated with biotinylated antibodies against the tumor-associated antigens CD19 and CD20. Furthermore, mSA2 CAR T cells were capable of mediating cancer cell lysis and IFNγ production in an antibody dose-dependent manner. The mSA2 CAR is a universal AT-CAR that can be combined with biotinylated tumor-specific antibodies to potentially target many different tumor types.

Precancer Atlas to Drive Precision Prevention Trials

Cancer development is a complex process driven by inherited and acquired molecular and cellular alterations. Prevention is the holy grail of cancer elimination, but making this a reality will take a fundamental rethinking and deep understanding of premalignant biology. In this Perspective, we propose a national concerted effort to create a Precancer Atlas (PCA), integrating multi-omics and immunity - basic tenets of the neoplastic process. The biology of neoplasia caused by germline mutations has led to paradigm-changing precision prevention efforts, including: tumor testing for mismatch repair (MMR) deficiency in Lynch syndrome establishing a new paradigm, combinatorial chemoprevention efficacy in familial adenomatous polyposis (FAP), signal of benefit from imaging-based early detection research in high-germline risk for pancreatic neoplasia, elucidating early ontogeny in BRCA1-mutation carriers leading to an international breast cancer prevention trial, and insights into the intricate germline-somatic-immunity interaction landscape. Emerging genetic and pharmacologic (metformin) disruption of mitochondrial (mt) respiration increased autophagy to prevent cancer in a Li-Fraumeni mouse model (biology reproduced in clinical pilot) and revealed profound influences of subtle changes in mt DNA background variation on obesity, aging, and cancer risk. The elaborate communication between the immune system and neoplasia includes an increasingly complex cellular microenvironment and dynamic interactions between host genetics, environmental factors, and microbes in shaping the immune response. Cancer vaccines are in early murine and clinical precancer studies, building on the recent successes of immunotherapy and HPV vaccine immune prevention. Molecular monitoring in Barrett's esophagus to avoid overdiagnosis/treatment highlights an important PCA theme. Next generation sequencing (NGS) discovered age-related clonal hematopoiesis of indeterminate potential (CHIP). Ultra-deep NGS reports over the past year have redefined the premalignant landscape remarkably identifying tiny clones in the blood of up to 95% of women in their 50s, suggesting that potentially premalignant clones are ubiquitous. Similar data from eyelid skin and peritoneal and uterine lavage fluid provide unprecedented opportunities to dissect the earliest phases of stem/progenitor clonal (and microenvironment) evolution/diversity with new single-cell and liquid biopsy technologies. Cancer mutational signatures reflect exogenous or endogenous processes imprinted over time in precursors. Accelerating the prevention of cancer will require a large-scale, longitudinal effort, leveraging diverse disciplines (from genetics, biochemistry, and immunology to mathematics, computational biology, and engineering), initiatives, technologies, and models in developing an integrated multi-omics and immunity PCA - an immense national resource to interrogate, target, and intercept events that drive oncogenesis. Cancer Res; 77(7); 1510-41. ©2017 AACR.

Abstract 4126: Validation of hypoglycosylated MUC1-CIN85 protein-protein interaction as a new therapeutic target for prevention of cancer invasion and metastasis

Overexpression and abnormal glycosylation of the epithelial glycoprotein MUC1 in cancer cells promotes metastasis. We have identified CIN85 (Cbl-interacting protein 85 KDa), as a binding partner of MUC1 in tumors. MUC1/CIN85 complex is found in early as well as advanced clinical stages of breast, ovarian, colon and prostate cancers among others. Co-localization of MUC1 and CIN85 on invadopodia structures enhances invasion and migration of cancer cells. Our hypothesis is that preventing the formation or dissociating existing CIN85/MUC1 complexes may result in a less aggressive tumor by decreasing local invasion and preventing distant metastases. To test this hypothesis, we have already identified and tested two novel compounds that significantly reduce the association between hypoglycosylated form of MUC1 and CIN85, and at 10μM concentration drastically reduce the migratory activity of mouse and human epithelial cancer cells. Our preliminary data also suggest that dissociation of the MUC1 and CIN85 complex decreases expression of hypoglycosylated MUC1, restoring the expression of its normal, fully glycosylated form. We are currently investigating the MUC1/CIN85-dependent signaling pathway with a particular focus on the ability of CIN85 to modulate MUC1 glycosylation by controlling its plasma membrane-Golgi trafficking. Ongoing experiments in an in vivo mouse model will confirm the ability of these drug compounds to decrease tumor growth and metastasis and validate CIN85/MUC1 complex as a viable therapeutic target and support development and testing of more potent antagonists.

Citation Format: Sandra Cascio, Jacque Faylo, Raahul Sriram, Anda Vlad, Carlos Camacho, Olivera J. Finn. Validation of hypoglycosylated MUC1-CIN85 protein-protein interaction as a new therapeutic target for prevention of cancer invasion and metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4126. doi:10.1158/1538-7445.AM2017-4126

Abstract 3747: msa2 biotin-binding CAR combined with biotinylated tumor-specific antibodies or DNA aptamers for universal cancer immunotherapy

Chimeric antigen receptor T cells (CAR-Ts) are highly promising as cancer therapeutics, but the creation of CARs for new antigens remains a laborious process. As an alternative strategy researchers are designing universal “tag-CARs” that instead of directly recognizing tumor antigens, recognize tags on tumor-specific antibodies bound to tumor cells, thereby activating T cell effector functions. Here we report the creation of a novel tag-CAR that uses the high affinity monomeric streptavidin 2 (msa2) biotin binding domain to target cancer cells labeled with biotinylated tumor-specific antibodies or DNA aptamers. We constructed lentiviral vectors encoding msa2 CARs with three different signaling architectures - CD28-zeta, CD28-OX40-zeta, and 4-1BB-zeta. After confirming that each msa2 CAR was efficiently expressed on the surface of Jurkat and primary human T cells, we found that plate-immobilized biotin was capable of specifically inducing T cell activation markers and cytokine production. We then stained a variety of cancer cell lines with various tumor-specific biotinylated antibodies or DNA aptamers targeting tumor antigens such as MUC1, CD19, CD20, and EGFR and found that the stained cells specifically activated the msa2-CAR cells and led to cytokine production. We are currently investigating the ability of msa2-CAR cells to lyse antibody and aptamer-bound cancer cells and will be assessing their ability to shrink tumors in a human tumor xenograft mouse model.

Citation Format: Jason J. Lohmueller, James D. Ham, Olivera J. Finn. msa2 biotin-binding CAR combined with biotinylated tumor-specific antibodies or DNA aptamers for universal cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3747. doi:10.1158/1538-7445.AM2017-3747

Current modalities in cancer immunotherapy: Immunomodulatory antibodies, CARs and vaccines

Successes of immune checkpoint inhibitors (ICIs) and chimeric antigen receptor (CAR) T cell therapy in curing patients with otherwise lethal cancers have validated immunotherapy as a treatment for cancer and have inspired excitement for its broader potential. Most promising is the ability of each approach to eliminate bulky and advanced-stage cancers and to achieve durable cures. Despite this success, to date only a subset of cancer patients and a limited number of cancer types respond to these therapies. A major goal now is to expand the types of cancer and number of patients who can be successfully treated. To this end a multitude of immunotherapies are being tested clinically in new combinations, and many new immunomodulatory antibodies and CARs are in development. A third major immunotherapeutic approach with renewed interest is cancer vaccines. While over 20years of therapeutic cancer vaccine trials have met with limited success, these studies have laid the groundwork for the use of therapeutic vaccines in combination with other immunotherapies or alone as prophylactic cancer vaccines. Prophylactic vaccines are now poised to revolutionize cancer prevention as they have done for the prevention of infectious diseases. In this review we examine three major cancer immunotherapy modalities: immunomodulatory antibodies, CAR T cell therapy and vaccines. For each we describe the current state of the art and outline major challenges and research directions forward.

Intra- and Extra-Cellular Events Related to Altered Glycosylation of MUC1 Promote Chronic Inflammation, Tumor Progression, Invasion, and Metastasis

Altered glycosylation of mucin 1 (MUC1) on tumor cells compared to normal epithelial cells was previously identified as an important antigenic modification recognized by the immune system in the process of tumor immunosurveillance. This tumor form of MUC1 is considered a viable target for cancer immunotherapy. The importance of altered MUC1 glycosylation extends also to its role as a promoter of chronic inflammatory conditions that lead to malignant transformation and cancer progression. We review here what is known about the role of specific cancer-associated glycans on MUC1 in protein-protein interactions and intracellular signaling in cancer cells and in their adhesion to each other and the tumor stroma. The tumor form of MUC1 also creates a different landscape of inflammatory cells in the tumor microenvironment by controlling the recruitment of inflammatory cells, establishing specific interactions with dendritic cells (DCs) and macrophages, and facilitating tumor escape from the immune system. Through multiple types of short glycans simultaneously present in tumors, MUC1 acquires multiple oncogenic properties that control tumor development, progression, and metastasis at different steps of the process of carcinogenesis.

Tn-MUC1 DC Vaccination of Rhesus Macaques and a Phase I/II Trial in Patients with Nonmetastatic Castrate-Resistant Prostate Cancer

MUC1 is a glycoprotein expressed on the apical surface of ductal epithelial cells. Malignant transformation results in loss of polarization and overexpression of hypoglycosylated MUC1 carrying truncated carbohydrates known as T or Tn tumor antigens. Tumor MUC1 bearing Tn carbohydrates (Tn-MUC1) represent a potential target for immunotherapy. We evaluated the Tn-MUC1 glycopeptide in a human phase I/II clinical trial for safety that followed a preclinical study of different glycosylation forms of MUC1 in rhesus macaques, whose MUC1 is highly homologous to human MUC1. Either unglycosylated rhesus macaque MUC1 peptide (rmMUC1) or Tn-rmMUC1 glycopeptide was mixed with an adjuvant or loaded on autologous dendritic cells (DC), and responses were compared. Unglycosylated rmMUC1 peptide induced negligible humoral or cellular responses compared with the Tn-rmMUC1 glycopeptide. Tn-rmMUC1 loaded on DCs induced the highest anti-rmMUC1 T-cell responses and no clinical toxicity. In the phase I/II clinical study, 17 patients with nonmetastatic castrate-resistant prostate cancer (nmCRPC) were tested with a Tn-MUC1 glycopeptide-DC vaccine. Patients were treated with multiple intradermal and intranodal doses of autologous DCs, which were loaded with the Tn-MUC1 glycopeptide (and KLH as a positive control for immune reactivity). PSA doubling time (PSADT) improved significantly in 11 of 16 evaluable patients (P = 0.037). Immune response analyses detected significant Tn-MUC1-specific CD4⁺ and/or CD8⁺ T-cell intracellular cytokine responses in 5 out of 7 patients evaluated. In conclusion, vaccination with Tn-MUC1-loaded DCs in nmCRPC patients appears to be safe, able to induce significant T-cell responses, and have biological activity as measured by the increase in PSADT following vaccination. Cancer Immunol Res; 4(10); 881-92. ©2016 AACR.

Immunobiology and immunosurveillance in patients with intraductal papillary mucinous neoplasms (IPMNs), premalignant precursors of pancreatic adenocarcinomas

Premalignant lesions for many cancers have been identified, and efforts are currently directed toward identification of antigens expressed on these lesions that would provide suitable targets for vaccines for cancer prevention. Intraductal papillary mucinous neoplasms (IPMNs) are premalignant pancreatic cysts of which a subset has the potential to progress to cancer. Currently, there are no validated predictive markers for progression to malignancy. We hypothesized that the presence or absence of immune surveillance of these lesions would be one such factor. Here we show that the tumor antigen MUC1, which is abnormally expressed on pancreatic cancer and is a target for cancer immunosurveillance, is also abnormally expressed on premalignant IPMN. We show that some IPMN patients make MUC1-specific IgG. Moreover, we show evidence of CD4 and CD8 T cell infiltration into IPMN areas of high dysplasia suggesting an ongoing immune response within the lesions. We also found, however, increased levels of circulating myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) in some IPMN patients as well as evidence of T cell exhaustion. Further studies correlating immunosurveillance or immunosuppression with IPMN progression to malignancy will help define the immune response as a biomarker of risk, leading potentially to a vaccine to boost spontaneous immunity and prevent progression to cancer.

Human anti-MUC1 antibodies elicited by a prophylactic cancer vaccine for CAR T cell immunotherapy

Hypoglycosylated MUC1 is a tumor-associated protein that is expressed on over 80% of all human cancers including adenocarcinomas of the colon, pancreas, breast, lung, prostate, and ovary, and multiple myeloma. In our recent clinical trial, individuals at-risk for colon adenocarcinoma received a prophylactic MUC1 cancer vaccine. Many individuals responded producing high titers of anti-MUC1 IgG antibodies with no detectable toxicity. This trial provided a rare source of human antibodies elicited and affinity-matured in a healthy human host to abnormal MUC1. Using our recently developed proteomics method, we isolated and identified 13 anti-MUC1 antibodies representing 7 different clonotypes. These antibodies bind to several different epitopes on the MUC1 vaccine peptide with a range of affinities (15.7μM to 130pM). They also stain MUC1 on human cancer cell lines and colon, breast, lung, and pancreas adenocarcinoma tissue sections while showing no reactivity against a large panel of normal tissues that express MUC1. We constructed lentiviral vectors encoding chimeric antigen receptors (CARs) using scFv’s of several of the antibodies as antigen binding regions and a variety of co-signaling domain architectures. Several of the scFv’s were able to retarget human primary T cells to become activated and produce cytokines in a MUC1-dependent manner and to lyse a variety of MUC1+ human tumor cell lines. Preclinical testing in mouse tumor xenograftgrafts is underway. Being of fully human origin and showing a high-degree of tumor specificity and efficacy in preclinical experiments, these antibodies will be tested in future clinical trials for potential approval for therapy of cancer patients.

MUC1 promotes an inflammatory microenvironment aggravating colitis-associated tumorigenesis in mice through up-regulation of pro-inflammatory cytokines

MUC1 is a transmembrane glycoprotein aberrantly expressed in human adenocarcinoma as well as chronic inflammatory conditions. We previously demonstrated that the tumor form of MUC1, in association with p65, upregulates expression of pro-inflammatory cytokines, including IL-6 and TNF-alpha, by modulating their transcription in epithelial cancer cells. Using azoxymethane/dextran sulfate sodium (AOM/DSS) murine model of inflammation driven colon carcinogenesis, we explored mechanism underlying MUC1/p65-induced transcription of IL-6 and TNF-alpha and its significance for the microenvironment of colitis-associated cancer. MUC1.Tg mice showed higher tumor incidence, decreased survival, greater body weight loss and shorter colon length. Consistent with our previous in vitro data, expression of NF-kB-dependent cytokines was higher in MUC1.Tg mice compared to WT. Moreover, we discovered that MUC1/p65 complex modulates IL-6 and TNF gene expression by regulating the crosstalk of post-translational modifications on their promoters. To understand the significance of MUC1/p65-modulated cytokines in progressive colitis that gives rise to colon cancer, we analyzed infiltration of inflammatory cells into the inflamed colon tissues. ELISA assay and gene expression analyses demonstrated that the treatment with AOM/DSS in the presence of human MUC1 on the colonic epithelia resulted in a significant upregulation of M1 type macrophage-associated genes, including IL-6, TNF-alpha and iNOS, whereas expression of M2 type macrophage markers, such as Arginase 1, Ym1 and IL-10, were drastically reduced compared to WT mice. Thus our findings reveal a pro-inflammatory role for MUC1 in colitis-related carcinogenesis.

Cancer immunoprevention

Cancer immunotherapy is now a reality. The results are phenomenal but the cost is outrageous. Even if the cost eventually comes down and immunotherapy becomes more broadly available, using the knowledge derived from immunotherapy to apply to immunoprevention would be a good strategy. The most likely approach to cancer immunoprevention is cancer vaccines. To date, cancer vaccines have been tested mostly in the setting of advanced disease. Numerous immunosuppressive mechanisms have been identified in the tumor microenvironment as well as systemically that compromise the ability of cancer patients to respond to the vaccines. Multiple approaches are being tested to improve therapeutic cancer vaccine efficacy, including combinations with other immunotherapies. An alternative approach is to administer the vaccines to individuals without cancer but at high risk for cancer. Data in support of this approach and immunoprevention in general is accumulating and clinical testing has started.

The FDA guidance on therapeutic cancer vaccines: the need for revision to include preventive cancer vaccines or for a new guidance dedicated to them

Cancer vaccines based on antigens derived from self molecules rather than pathogens have been under basic and clinical investigations for many years. Up until very recently, they had been tested primarily in the setting of metastatic disease with the goal to engage the immune system in slowing down disease progression. Many therapeutic vaccine trials, either investigator initiated or led by pharmaceutical companies, have been completed and many are currently ongoing, following the FDA Guidance on therapeutic cancer vaccines published in 2011. In recent years, the target of cancer vaccines is being shifted to early cancer and even premalignant disease with the goal of preventing cancer. Although some issues addressed in the FDA Guidance on therapeutic vaccines apply to preventive vaccines, many do not. Here, we discuss a set of recommendations for revising the current Guidance to also cover preventive vaccines, or to include in a new Guidance dedicated specifically to vaccines for cancer prevention.