Abstract
The immune system plays a key role in cancer suppression. Immunotherapy is widely used as a treatment method in patients with various types of cancer. Immune checkpoint blockade using antibodies, such as anti-PD-1, anti-PD-L1, and anti-CTLA-4, is currently gaining popularity. A systematic literature search was executed, and all available data was summarized. This review shows that specific dietary patterns (such as, e.g., animal-based, vegetarian, or Mediterranean diet) alter the gut microbiome’s composition. An appropriate intestinal microbiota structure might modulate the function of human immune system, which affects the bodily anti-cancer response. This paper shows also that specific bacteria species inhabiting the gastrointestinal tract can have a beneficial influence on the efficacy of immunotherapy. Antibiotics weaken gut bacteria and worsen the immune checkpoint blockers’ efficacy, whereas a faecal microbiota transplant or probiotics supplementation may help restore bacterial balance in the intestine. Other factors (like vitamins, glucose, or BMI) change the cancer treatment response, as well. This review demonstrates that there is a strong association between one’s diet, gut microbiome composition, and the outcome of immunotherapy. However, further investigation on this subject is required.
Highlights
According to the current knowledge, the immune system plays an extremely important role in the pathogenesis of cancer [1]
Transfer of Ruminococci or Alistipes shahii restores the efficacy of this kind of treatment because these bacteria species are correlated with an increased tumor necrosis factor (TNF)-α production, whereas Lactobacillus species are negatively correlated with TNF-α production and worsen the clinical outcome [16,24,72,84,99]
Kim et al on mouse models has shown that the combination of phenformin with PD-1 antibodies increases the effectiveness of this therapy, compared to the use of anti-PD-1 antibodies in monotherapy
Summary
According to the current knowledge, the immune system plays an extremely important role in the pathogenesis of cancer [1]. The most important ones include the upregulation of checkpoint receptor ligands, which results in the reduction of the number of tumor infiltrating lymphocytes (TIL), the production of soluble immunosuppressive factors (IL-10, TGF-beta), the downregulation of elements responsible for antigen presentation, and tumor infiltration by suppressor immune cells (regulatory T cells, Treg) [8]. The immune checkpoints blockade works by activating a tumor-specific immunological response This method of immunotherapy is currently dominant in the treatment of cancer [9,10]. The expression of immune checkpoints on cancer cells and immune cells plays an important role in tumor escape from immune surveillance. Expression of CTLA-4 occurs on Treg cells, causing their activation and immunosuppressive effect on cytotoxic T lymphocytes (CTLs). Anti-CTLA-4 therapy uses monoclonal antibodies—ipilimumab and tremelimumab [15]
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