Immunotherapy of Colorectal Cancer

Targeting colorectal cancer cells using AND-gated adaptor RevCAR T-cells

Despite the success of chimeric antigen receptor (CAR) T-cells especially for treating hematological malignancies, critical drawbacks, such as "on-target, off-tumor" toxicities, need to be addressed to improve safety in translating to clinical application. This is especially true, when targeting tumor-associated antigens (TAAs) that are not exclusively expressed by solid tumors but also on hea9lthy tissues. To improve the safety profile, we developed switchable adaptor CAR systems including the RevCAR system. RevCAR T-cells are activated by cross-linking of bifunctional adaptor molecules termed target modules (RevTM). In a further development, we established a Dual-RevCAR system for an AND-gated combinatorial targeting by splitting the stimulatory and co-stimulatory signals of the RevCAR T-cells on two individual CARs. Examples of common markers for colorectal cancer (CRC) are the carcinoembryonic antigen (CEA) and the epithelial cell adhesion molecule (EpCAM), while these antigens are also expressed by healthy cells. Here we describe four novel structurally different RevTMs for targeting of CEA and EpCAM. All anti-CEA and anti-EpCAM RevTMs were validated and the simultaneous targeting of CEA+ and EpCAM+ cancer cells redirected specific in vitro and in vivo killing by Dual-RevCAR T-cells. In summary, we describe the development of CEA and EpCAM specific adaptor RevTMs for monospecific and AND-gated targeting of CRC cells via the RevCAR platform as an improved approach to increase tumor specificity and safety of CAR T-cell therapies.

The New Era of Cancer Immunotherapy: Targeting Myeloid-Derived Suppressor Cells to Overcome Immune Evasion

Suppression of antitumor immune responses is one of the main mechanisms by which tumor cells escape from destruction by the immune system. Myeloid-derived suppressor cells (MDSCs) represent the main immunosuppressive cells present in the tumor microenvironment (TME) that sustain cancer progression. MDSCs are a heterogeneous group of immature myeloid cells with a potent activity against T-cell. Studies in mice have demonstrated that MDSCs accumulate in several types of cancer where they promote invasion, angiogenesis, and metastasis formation and inhibit antitumor immunity. In addition, different clinical studies have shown that MDSCs levels in the peripheral blood of cancer patients correlates with tumor burden, stage and with poor prognosis in multiple malignancies. Thus, MDSCs are the major obstacle to many cancer immunotherapies and their targeting may be a beneficial strategy for improvement the efficiency of immunotherapeutic interventions. However, the great heterogeneity of these cells makes their identification in human cancer very challenging. Since both the phenotype and mechanisms of action of MDSCs appear to be tumor-dependent, it is important to accurately characterized the precise MDSC subsets that have clinical relevance in each tumor environment to more efficiently target them. In this review we summarize the phenotype and the suppressive mechanisms of MDSCs populations expanded within different tumor contexts. Further, we discuss about their clinical relevance for cancer diagnosis and therapy.

Assessment for Risk Status of Colorectal Cancer Patients: A Novel Prediction Model Based on Immune-Related Genes

Heterogeneity in patients with colorectal cancer (CRC) leads to different strategies in clinical decision making. Identifying distinctive subgroups in patients contributes to develop more individualized treatments. This study constructed a novel prediction model for the prognosis of CRC patients based on the value of risk score combining the expression status of immune-related genes and coefficients. In this study, we built an interactive network of prognosis-related immune genes and transcription factors and adopted several methods to verify the accuracy of model. Moreover, we assessed the correlation between risk score and immune infiltration. The results suggested that the model was well fit and the risk score could be an independent predictive factor for CRC patients. This model has high application value in the clinic.

Strategy to targeting the immune resistance and novel therapy in colorectal cancer

Assessing the CRC subtypes that can predict the outcome of colorectal cancer (CRC) in patients with immunogenicity seems to be a promising strategy to develop new drugs that target the antitumoral immune response. In particular, the disinhibition of the antitumoral T‐cell response by immune checkpoint blockade has shown remarkable therapeutic promise for patients with mismatch repair (MMR) deficient CRC. In this review, the authors provide the update of the molecular features and immunogenicity of CRC, discuss the role of possible predictive biomarkers, illustrate the modern immunotherapeutic approaches, and introduce the most relevant ongoing preclinical study and clinical trials such as the use of the combination therapy with immunotherapy. Furthermore, this work is further to understand the complex interactions between the immune surveillance and develop resistance in tumor cells. As expected, if the promise of these developments is fulfilled, it could develop the effective therapeutic strategies and novel combinations to overcome immune resistance and enhance effector responses, which guide clinicians toward a more “personalized” treatment for advanced CRC patients.

Large-scale database mining reveals hidden trends and future directions for cancer immunotherapy

Cancer immunotherapy has fundamentally changed the landscape of oncology in recent years and significant resources are invested into immunotherapy research. It is in the interests of researchers and clinicians to identify promising and less promising trends in this field in order to rationally allocate resources. This requires a quantitative large-scale analysis of cancer immunotherapy related databases.

We developed a novel tool for text mining, statistical analysis and data visualization of scientific literature data. We used this tool to analyze 72002 cancer immunotherapy publications and 1469 clinical trials from public databases. All source codes are available under an open access license.

The contribution of specific topics within the cancer immunotherapy field has markedly shifted over the years. We show that the focus is moving from cell-based therapy and vaccination towards checkpoint inhibitors, with these trends reaching statistical significance. Rapidly growing subfields include the combination of chemotherapy with checkpoint blockade. Translational studies have shifted from hematological and skin neoplasms to gastrointestinal and lung cancer and from tumor antigens and angiogenesis to tumor stroma and apoptosis.

This work highlights the importance of unbiased large-scale database mining to assess trends in cancer research and cancer immunotherapy in particular. Researchers, clinicians and funding agencies should be aware of quantitative trends in the immunotherapy field, allocate resources to the most promising areas and find new approaches for currently immature topics.

Genomics and emerging biomarkers for immunotherapy of colorectal cancer

Colorectal cancer (CRC) is a common and lethal disease with a high therapeutic need. For most patients with metastatic CRC, chemotherapy is the only viable option. Currently, immunotherapy is restricted to the particular genetic subgroup of mismatch-repair deficient (MMRd)/microsatellite instable (MSI) CRC. Anti-PD1 therapy was recently FDA-approved as a second-line treatment in this subgroup. However, in a metastatic setting, these MMRd/MSI tumors are vastly outnumbered by mismatch-repair proficient (MMRp)/microsatellite stable (MSS) tumors. These MMRp/MSS tumors do not meaningfully respond to any traditional immunotherapy approach including checkpoint blockade, adoptive cell transfer and vaccination. This resistance to immunotherapy is due to a complex tumor microenvironment that counteracts antitumor immunity through a combination of poorly antigenic tumor cells and an immunosuppressive tumor microenvironment. To find ways of overcoming immunotherapy resistance in the majority of CRC patients, it is necessary to analyze the immunological makeup in an in-depth and personalized way and in the context of their tumor genetic makeup. Flexible, biomarker-guided early-phase immunotherapy trials are needed to optimize this workflow. In this review, we detail key mechanisms for immune evasion and emerging immune biomarkers for personalized immunotherapy in CRC. Also, we present a template for biomarker-guided clinical trials that are needed to move new immunotherapy approaches closer to clinical application.

Personalized and precision medicine: integrating genomics into treatment decisions in gastrointestinal malignancies

The advent of next generation sequencing (NGS) technologies has advanced our understanding of the intrinsic biology of different gastrointestinal (GI) tumor types. The use of novel, more efficient sequencing platforms has improved turnaround times of sequencing results. This is providing real time opportunities to put precision medicine to the test. A number of early phase clinical trials are testing targeted therapies in unique molecularly characterized subsets of patients (baskets). While basket studies are gaining momentum, treatment failures serve to remind us that shifting from a histology-driven to a histology-agnostic approach is unlikely to be a failure-free strategy for a number of tumor types as recently learnt from vemurafenib failure in BRAF mutated metastatic colorectal cancer (mCRC). GI malignancies are clinically and molecularly heterogeneous. Unfortunately, development of biomarkers of response to therapy as well as targeted therapies for GI adenocarcinomas has fallen behind compared to other malignancies. Trastuzumab is the only FDA approved targeted therapy for GI adenocarcinomas for which a biomarker of response (HER2 amplifications) is available. In addition, RAS mutations are known to predict lack of response to epidermal growth factor receptor (EGFR) inhibitors in advanced colorectal cancer (CRC) patients. However, NGS has recently revealed that a number of actionable genetic aberrations are present at low prevalence across different GI malignancies. Prospective randomized clinical trials will determine whether matching actionable aberration with targeted therapy will contribute to improve survival in patients with GI malignancies. Here, we review current evidence for targeted therapies in GI malignancies, as well as application and pitfalls of NGS including tissue testing and liquid biopsies.