Editorial: Cancer Plasticity and the Microenvironment: Implications for Immunity and Therapy Response

Novel therapeutic drug strategies to tackle immune-oncological challenges faced by cancer patients during COVID-19

INTRODUCTION

For the clinical treatment of cancer patients, coronavirus (SARS-CoV-2) can cause serious immune-related problems. Cancer patients, who experience immunosuppression due to the pathogenesis and severity of disease, may become more aggressive due to multiple factors such as age, comorbidities, and immunosuppression. In this pandemic era, COVID-19 causes lymphopenia, cancer cell awakening, inflammatory diseases, and a cytokine storm that worsens disease-related morbidity and prognosis.

AREAS COVERED

We discuss all the risk factors of COVID-19 associated with cancer patients and propose new strategies to use antiviral and anticancer drugs for therapeutic purposes. We bring new drugs, cancers and COVID-19 treatment strategies together to address the immune system challenges faced by oncologists.

EXPERT OPINION

The chronic inflammatory microenvironment caused by COVID-19 awakens dormant cancer cells through inflammation and autoimmune activation. Drug-related strategies to ensure that clinical treatment can reduce the susceptibility of cancer patients to COVID-19, and possible counter-measures to minimize the harm caused by the COVID-19 have been outlined. The response to the pandemic and recovery has been elaborated, which can provide information for long-term cancer treatment and speed up the optimization process.

Engineered in vitro tumor models for cell-based immunotherapy

Tumor immunotherapy is rapidly evolving as one of the major pillars of cancer treatment. Cell-based immunotherapies, which utilize patient's own immune cells to eliminate cancer cells, have shown great promise in treating a range of malignancies, especially those of hematopoietic origins. However, their performance on a broader spectrum of solid tumor types still fall short of expectations in the clinical stage despite promising preclinical assessments. In this review, we briefly introduce cell-based immunotherapies and the inhibitory mechanisms in tumor microenvironments that may have contributed to this discrepancy. Specifically, a major obstacle to the clinical translation of cell-based immunotherapies is in the lack of preclinical models that can accurately assess the efficacies and mechanisms of these therapies in a (patho-)physiologically relevant manner. Lately, tissue engineering and organ-on-a-chip tools and microphysiological models have allowed for more faithful recapitulation of the tumor microenvironments, by incorporating crucial tumor tissue features such as cellular phenotypes, tissue architecture, extracellular matrix, physical parameters, and their dynamic interactions. This review summarizes the existing engineered tumor models with a focus on tumor immunology and cell-based immunotherapy. We also discuss some key considerations for the future development of engineered tumor models for immunotherapeutics. STATEMENT OF SIGNIFICANCE: Cell-based immunotherapies have shown great promise in treating hematological malignancies and some epithelial tumors. However, their performance on a broader spectrum of solid tumor types still fall short of expectations. Major obstacles include the inhibitory mechanisms in tumor microenvironments (TME) and the lack of preclinical models that can accurately assess the efficacies and mechanisms of cellular therapies in a (patho-)physiologically relevant manner. In this review, we introduce recent progress in tissue engineering and microphysiological models for more faithful recapitulation of TME for cell-based immunotherapies, and some key considerations for the future development of engineered tumor models. This overview will provide a better understanding on the role of engineered models in accelerating immunotherapeutic discoveries and clinical translations.

Cellular plasticity and drug resistance in sarcoma

Sarcomas, originating from mesenchymal progenitor stem cells, are a group of rare malignant tumors with poor prognosis. Wide surgical resection, chemotherapy, and radiotherapy are the most common sarcoma treatments. However, sarcomas' response rates to chemotherapy are quite low and sarcoma cells can have intrinsic or acquired resistance after treatment with chemotherapeutics drugs, leading to the development of multi-drug resistance (MDR). Cancer cellular plasticity plays pivotal roles in cancer initiation, progression, therapy resistance and cancer relapse. Moreover, cancer cellular plasticity can be regulated by a multitude of factors, such as genetic and epigenetic alterations, tumor microenvironment (TME) or selective pressure imposed by treatment. Recent studies have demonstrated that cellular plasticity is involved in sarcoma progression and chemoresistance. It's essential to understand the molecular mechanisms of cellular plasticity as well as its roles in sarcoma progression and drug resistance. Therefore, this review focuses on the regulatory mechanisms and pathological roles of these diverse cellular plasticity programs in sarcoma. Additionally, we propose cellular plasticity as novel therapeutic targets to reduce sarcoma drug resistance.

Integrating the Tumor Microenvironment into Cancer Therapy

Tumor progression is mediated by reciprocal interaction between tumor cells and their surrounding tumor microenvironment (TME), which among other factors encompasses the extracellular milieu, immune cells, fibroblasts, and the vascular system. However, the complexity of cancer goes beyond the local interaction of tumor cells with their microenvironment. We are on the path to understanding cancer from a systemic viewpoint where the host macroenvironment also plays a crucial role in determining tumor progression. Indeed, growing evidence is emerging on the impact of the gut microbiota, metabolism, biomechanics, and the neuroimmunological axis on cancer. Thus, external factors capable of influencing the entire body system, such as emotional stress, surgery, or psychosocial factors, must be taken into consideration for enhanced management and treatment of cancer patients. In this article, we review prognostic and predictive biomarkers, as well as their potential evaluation and quantitative analysis. Our overarching aim is to open up new fields of study and intervention possibilities, within the framework of an integral vision of cancer as a functional tissue with the capacity to respond to different non-cytotoxic factors, hormonal, immunological, and mechanical forces, and others inducing stroma and tumor reprogramming.

Integrating tumor hypoxic stress in novel and more adaptable strategies for cancer immunotherapy

Immunotherapy is poised to become an increasingly utilized therapy in the treatment of cancer. However, several abnormalities in the tumor microenvironment (TME) that can thwart the efficacy of immunotherapies have been established. Microenvironmental hypoxia is a determining factor in shaping aggressiveness, metastatic potential and treatment resistance of solid tumors. The characterization of this phenomenon could prove beneficial for determining a patient's treatment path and for the introduction of novel targetable factors that can enhance therapeutic outcome. Indeed, the ablation of hypoxia has the potential to sensitize tumors to immunotherapy by metabolically remodeling their microenvironment. In this review, we discuss the intrinsic contributions of hypoxia to cellular plasticity, heterogeneity, stemness and genetic instability in the context of immune escape. In addition, we will shed light on how managing hypoxia can ameliorate response to immunotherapy and how integrating hypoxia gene signatures could play a role in this pursuit.

[An integral view of cancer (III). Evaluation of new biomarkers and treatment strategies]

We propose a comprehensive approach to oncological disease, based on a systemic consideration of biology, health and disease. Our two previous review articles focused on tumour microenvironment and the discovery of new biomarkers; here we discuss the practical application of these principles to pathology, through the identification, evaluation and quantitative analysis of new prognostic and predictive factors (Immunoscore, TIME). We also consider the clinical use of promising, better tolerated treatments, such as immunotherapy. The integrative pathologist now has access to the latest improved oncology stratification tools designed to identify effective treatment strategies, based on the natural evolution of clinical and scientific knowledge that transcend the gene-centric theory of cancer.