Cellular Plasticity: A Route to Senescence Exit and Tumorigenesis

Senescence is a dynamic, multistep program that results in permanent cell cycle arrest and is triggered by developmental or environmental, oncogenic or therapy-induced stress signals. Senescence is considered as a tumor suppressor mechanism that prevents the risk of neoplastic transformation by restricting the proliferation of damaged cells. Cells undergoing senescence sustain important morphological changes, chromatin remodeling and metabolic reprogramming, and secrete pro-inflammatory factors termed senescence-associated secretory phenotype (SASP). SASP activation is required for the clearance of senescent cells by innate immunity. Therefore, escape from senescence and the associated immune editing would be a prerequisite for tumor initiation and progression as well as therapeutic resistance. One of the possible mechanisms for overcoming senescence could be the acquisition of cellular plasticity resulting from the accumulation of genomic alterations and genetic and epigenetic reprogramming. The modified composition of the SASP produced by these reprogrammed cancer cells would create a permissive environment, allowing their immune evasion. Additionally, the SASP produced by cancer cells could enhance the cellular plasticity of neighboring cells, thus hindering their recognition by the immune system. Here, we propose a comprehensive review of the literature, highlighting the role of cellular plasticity in the pro-tumoral activity of senescence in normal cells and in the cancer context.

Gut Microbiota Dysbiosis Is a Crucial Player for the Poor Outcomes for COVID-19 in Elderly, Diabetic and Hypertensive Patients

A new infectious disease, named COVID-19, caused by the coronavirus associated to severe acute respiratory syndrome (SARS-CoV-2) has become pandemic in 2020. The three most common pre-existing comorbidities associated with COVID-19-related death are elderly, diabetic, and hypertensive people. A common factor among these risk groups for the outcome of death in patients infected with SARS-CoV-2 is dysbiosis, with an increase in the proportion of bacteria with a pro-inflammatory profile. Due to this dysbiosis, elderly, diabetic, and hypertensive people present a higher propensity to mount an inflammatory environment in the gut with poor immune editing, culminating in a weakness of the intestinal permeability barrier and high bacterial product translocation to the bloodstream. This scenario culminates in a low-grade, persistent, and systemic inflammation. In this context, we propose here that high circulating levels of bacterial products, like lipopolysaccharide (LPS), can potentiate the SARS-CoV-2-induced cytokines, including IL-6, being crucial for development of the cytokine storm in the severe form of the disease. A better understanding on the possible correlation between gut dysbiosis and poor outcomes observed in elderly, diabetic, and hypertensive people can be useful for the development of new therapeutic strategies based on modulation of the gut microbiota.

Tumor Genotype Is Shaping Immunophenotype and Responses to Immune Checkpoint Inhibitors in Solid Tumors

ABSTRACT A major breakthrough in cancer treatment was ushered in by the development of immune checkpoint blockade therapy such as anti-CTLA4 antibody and anti-PD-1 and anti-programmed cell death-ligand 1 antibodies that are now approved for use in an increasing number of malignancies. Despite the relative success of immune checkpoint inhibitors with certain tumor types, many patients still fail to respond to such therapies, and the field is actively trying to understand the mechanisms of resistance, intrinsic or acquired, to immune checkpoint blockade. Herein, we discuss the roles that somatic genomic mutations in oncogenic pathways play in immune editing, as well as some of the current approaches toward improving response to immunotherapy.

EZH2 inhibition: a promising strategy to prevent cancer immune editing

Immunotherapies are revolutionizing the clinical management of a wide range of cancers. However, intrinsic or acquired unresponsiveness to immunotherapies does occur due to the dynamic cancer immunoediting which ultimately leads to immune escape. The evolutionarily conserved histone modifier enhancer of zeste 2 (EZH2) is aberrantly overexpressed in a number of human cancers. Accumulating studies indicate that EZH2 is a main driver of cancer cells’ immunoediting and mediate immune escape through downregulating immune recognition and activation, upregulating immune checkpoints and creating an immunosuppressive tumor microenvironment. In this review, we overviewed the roles of EZH2 in cancer immunoediting, the preclinical and clinical studies of current pharmacologic EZH2 inhibitors and the prospects for EZH2 inhibitor and immunotherapy combination for cancer treatment.

Immune Checkpoint Regulators: A New Era Toward Promising Cancer Therapy

During the last century, our battle against cancer has been inaugurated upon three main approaches; surgery, radiation and chemotherapy. The latest findings on the effectiveness of immunotherapy in cancer management offer a ray of hope after decades of research and studies on the best treatment methods. Immunotherapy has proven effective in the surveillance and destruction of cancer- causing cells, demonstrating its ability to suppress cancer through controlling the wellestablished immune-editing process. Immuno-editing is a process that comprises three principal elements; elimination, equilibrium, and escape, and is paramount to the comprehension of checkpoint inhibition. Cancer cells employ various approaches to evade the elimination step leading to its immune- escape. The escape mechanism encompasses the up-regulation of negative co-signals that block successful activation of cancer-eradicating immune cells, developing cytokine background that favors the immunosuppressive tumor microenvironment (TME), or dropping the expression of tumor- specific proteins known as neo-antigens, therefore reducing the immunogenic activity against cancer cells. Today, checkpoint inhibitors are considered as a primary approach in our fight against cancer. Strategies targeting the inhibitory roles of checkpoint inhibitors have been shown effective against different cancer types and stages, and some already gained the FDA’s approval. This review seeks to comprehensively cover the historical background as well as the most recent updates for the role of immune checkpoint regulators in the maintenance of immune homeostatic balance as well as keeping the tumorigenic cells in check.

Cancer immunity and immunotherapy

The development of a cancer in an immunologically intact host leads to an interaction between the host immune system and the tumour mass. The three phases of tumour/host interactions (Elimination, Equilibrium, and Escape) form the ‘immune editing hypothesis’, which serves as a valuable framework for understanding of the immune response to cancer and the approaches by which this might be manipulated for therapeutic benefit. Immunotherapy is emerging as an important treatment modality for many tumour types, including melanoma, lung cancer, kidney cancer, lymphoma, and bladder cancer. By the time you read this chapter it is highly likely that additional monotherapy and combination regimens will be approved in multiple tumour types, but an understanding of the basic mechanisms underlying an adaptive antitumour immune response will be valuable in understanding future agents, as well as their toxicities.