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 < 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 < 6 mm in size (consistent with < 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 >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<.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.