Oxidative stress is a hallmark in the etiology of cancer and tumors and is primarily due to an imbalance in the generation of reactive oxygen species (ROS) and the cellular built-in antioxidant defence system. ROS imbalances the redox homeostasis, which ignites cellular signaling, leading to tumorigenesis. Ultraviolet radiation (UVR), radiation (γ radiation), and various environmental factors including heat, chemicals, exercise, carcinogenic pollutants, may enhance the production of cellular ROS that introduce apoptosis in tumor cells, hence killing malignant cells. On the other hand, chronic accumulation of ROS may also progress cancer/tumor growth by suppressing the cellular built-in defence system. Cancer is a complex disease, the outcomes of which largely depend on the cross-talk between the tumor and its microenvironment. Studies of host-tumor relationships have delineated an interplay of cancer cells, stromal elements, and immune components. Inside the tumor niche, many host response factors are produced, for example protection against cytotoxic reactions to tumor-promoting inflammatory reactions.

The specific factors that dictate the outcome of the anticancer response remain largely unknown, but tumor cells typically exploit host factors to enhance disease progression and create a local immunosuppressive network. The explanation of certain cellular pathways helping to prevent protective immunity have introduced novel immunotherapeutics (T cell costimulatory molecules CTLA-4 and PD-1, cancer vaccines for dendritic cells pulsed with tumor antigens, and engineered T cells having chimeric antigen receptors anti-CD19 for lymphoid leukemias etc.) targeting specific defects within host reactions. Various immunological factors may be activated by phytochemicals/antioxidants, and it is necessary to report and highlight specific antioxidants which modulate the cellular redox balance and help upregulate the immune system in tumorigenesis. The recurrence of tumor cells is seen in almost all cancer types, due to a subset of malignant cells that may have the potential to initiate tumors. These tumors are neither eliminated by immune cells nor able to grow straight into overt tumors. Stem cells have multiple types such as pluripotent, immune-privileged, and long-living, but depend on specialized niches. These criteria would be fulfilled by cancer stem cells (CSCs.) Thus, latent tumors may be maintained by a niche-constrained reservoir of long-living CSCs that are exempt from immunosurveillance, while niche-independent and more immunogenic daughter cells are constantly eliminated.

The aim of this Special Issue is to explore certain specific novel drug(s)/phytochemicals, which can modulate the cellular redox species and help avoid recurrence of tumorigenesis, along with enhancing tumor cell immunity in their micro niches. Original research and review articles are welcomed.

Potential topics include but are not limited to the following:

• Evolution of tumor immunology and advancements. Study of the involvement of different immune cells at distinct stages of tumor progression and role of antioxidants
• Shaping up of tumors during various developmental stages
• Therapeutic uses of antioxidants/phytochemicals in treatment of various cancers
• Why tumors are being contained but not fully eliminated by the immune system?
• Any specific cancer stem cells (CSCs) are required for tumor propagation, and how these CSCs bypass the suppressing effect of antioxidants on redox balance?
• Impact of antioxidants on the molecular characteristics of tumor cells
• Implementation of chemotherapies in basic cancer research and clinical oncology
• Highlighting the rapidly developing areas in cancer immunology and immunotherapy using various natural antioxidants
• Molecular docking and network pharmacology associated studies of cancer inhibiting phytochemicals