The emerging role of immunotherapy in colorectal cancer

Immunotherapy for colorectal cancer: where are we heading?

INTRODUCTION

In the last few years, significant advances in molecular biology have provided new therapeutic options for colorectal cancer (CRC). The development of new drugs that target the immune response to cancer cells seems very promising and has already been established for other tumor types. In particular, the use of immune checkpoint inhibitors seems to be an encouraging immunotherapeutic strategy. Areas covered: In this review, the authors provide an update of the current evidence related to this topic, though most immunotherapies are still in early-phase clinical trials for CRC. To understand the key role of immunotherapy in CRC, the authors discuss the delicate balance between immune-stimulating and immune-suppressive networks that occur in the tumor microenvironment. Expert opinion: Modulation of the immune system through checkpoint inhibition is an emerging approach in CRC therapy. Nevertheless, selection criteria that could enable the identification of patients who may benefit from these agents are necessary. Furthermore, potential prognostic and predictive immune biomarkers based on immune and molecular classifications have been proposed. As expected, additional studies are required to develop biomarkers, effective therapeutic strategies and novel combinations to overcome immune escape resistance and enhance effector response.

Viroimmunotherapy for Colorectal Cancer: Clinical Studies

Colorectal cancer is a leading cause of cancer incidence and death. Therapies for those with unresectable or recurrent disease are not considered curative at present. More effective and less toxic therapies are desperately needed. Historically, the immune system was thought to be an enemy to oncolytic viral therapy. Thinking that oncolysis would be the only mechanism for cell death, oncolytic virologists theorized that immune clearance was a detriment to oncolysis. Recent advances in our understanding of the tumor microenvironment, and the interplay of tumor survival and a patient's immune system have called into question our understanding of both arenas. It remains unclear what combination of restrictions or enhancements of innate and/or cell-mediated immunity can yield the highest likelihood of viral efficacy. This article reviews the variety of mechanisms explored for viruses such as immunotherapy for colorectal cancer.

A Leishmania murine model to evaluate the immunomodulatory properties of Pythium insidiosum proteins

Pythium insidiosum immunomodulatory vaccine (PiV) has been tested in clinical and experimental pythiosis. Previous data showed that P. insidiosum immunogens have the ability to switch the Th2 immune response, normally in place during pythiosis, to a curative Th1 response. Pythiosis cannot be reproduced in experimental rodents with the exception of rabbits, and thus thorough evaluation of PiV´s immunomodulatory properties has been limited by the lack of a compatible inbred mouse model. In this study, we took advantage of the murine BALB/c Leishmania infection model, where infected mice produce a Th2 response, to evaluate the PiV Th2 to Th1 immunomodulatory potential. Twenty-one days following challenge with L. major, large cutaneous granulomas developed in control mice, consistent with the expected Th2 response. In contrast, Leishmania-induced cutaneous lesions in PiV-immunized mice were minimal or absent. Flow cytometry analysis of spleen cells from mice immunized with PiV and subsequently challenged with L. major displayed more CD4+ and CD8+ cells than the control group. Moreover, spleen cells from mice that were immunized with PiV then challenged with L. major secreted high levels of IFN-γ, with a moderate IL-2, IL-4, and IL-10 mixed cytokine profile upon in vitro re-stimulation with PiV. Anti-P. insidiosum IgG1 in immunized animals was present at low titers suggesting a minor immunological role for this Ig isotype in this model. Our preliminary data showed that BALB/c mice challenged with L. major represent an attractive model in which to study PiV´s immunomodulatory properties.

Tailored Treatment of Colorectal Cancer: Surgical, Molecular, and Genetic Considerations

Colorectal cancer (CRC) is a complex cancer disease, and approximately 40% of the surgically cured patients will experience cancer recurrence within 5 years. During recent years, research has shown that CRC treatment should be tailored to the individual patient due to the wide variety of risk factors, genetic factors, and surgical complexity. In this review, we provide an overview of the considerations that are needed to provide an individualized, patient-tailored treatment. We emphasize the need to assess the predictors of CRC, and we summarize the latest research on CRC genetics and immunotherapy. Finally, we provide a summary of the significant variations in the colon and rectal anatomy that is important to consider in an individualized surgical approach. For the individual patient with CRC, a tailored treatment approach is needed in the preoperative, operative, and postoperative phase.

Beyond checkpoint inhibition - Immunotherapeutical strategies in combination with radiation

The revival of cancer immunotherapy has taken place with the clinical success of immune checkpoint inhibition. However, the spectrum of immunotherapeutic approaches is much broader encompassing T cell engaging strategies, tumour-specific vaccination, antibodies or immunocytokines. This review focuses on the immunological effects of irradiation and the evidence available on combination strategies with immunotherapy. The available data suggest great potential of combined treatments, yet also poses questions about dose, fractionation, timing and most promising multimodal strategies.