The Microbiome and Its Implications in Cancer Immunotherapy

Abstract

Cancer is responsible for ~18 million deaths globally each year, representing a major cause of death. Several types of therapy strategies such as radiotherapy, chemotherapy and more recently immunotherapy, have been implemented in treating various types of cancer. Microbes have recently been found to be both directly and indirectly involved in cancer progression and regulation, and studies have provided novel and clear insights into the microbiome-mediated emergence of cancers. Scientists around the globe are striving hard to identify and characterize these microbes and the underlying mechanisms by which they promote or suppress various kinds of cancer. Microbes may influence immunotherapy by blocking various cell cycle checkpoints and the production of certain metabolites. Hence, there is an urgent need to better understand the role of these microbes in the promotion and suppression of cancer. The identification of microbes may help in the development of future diagnostic tools to cure cancers possibly associated with the microbiome. This review mainly focuses on various microbes and their association with different types of cancer, responses to immunotherapeutic modulation, physiological responses, and prebiotic and postbiotic effects.

Gut microbiota and immune alteration in cancer development: implication for immunotherapy

“…The principle of immunotherapy is based on the fundamental concept, 'cancer immunoediting', stating that the immune system can be protective to the host meanwhile prompting cancer progression. 17 During immunoediting, the immune system shapes the immunogenicity of tumours in three phases-elimination, equilibrium and escape. 17 In the first phase, both innate and adaptive immune systems detect and destroy early tumours before they become clinically visible.…”

Nerves in gastrointestinal cancer: from mechanism to modulations

“…This phenomenon is further reflected by the observation that the gut microbiome of patients with CRC displays prominent differences compared with healthy individuals, including reduced butyrate-producing bacterial lineages and enriched levels of pathogenic bacteria such as Escherichia coli, Salmonella and Shigella. Such bacteria have been shown to strongly adhere to colonic epithelial cells and induce DNA damage in vitro (rat cell lines) and in vivo (CRC mouse models) 3,[241][242][243] . Patients with CRC also display an altered virome (such as presence of cytomegalovirus) and mycobiome (for example, abundance of fungal Malassezia), when compared with healthy individuals, but no link with neural messengers has been established yet 228 .…”

Harness the functions of gut microbiome in tumorigenesis for cancer treatment

“…Many factors are deciding the immunotherapy efficacy, including mutational load, cancer metabolism, and microbiota [ 40 ]. Evidence demonstrates that the composition of microbiota impacts responses to anticancer immunotherapies and can be a novel biomarker of response assessment [ 256 , 257 ]. It was demonstrated that the presence of specific immune‐potentiating bacteria, including Akkermansia muciniphila, Faecalibacterium prausnitzii, Bifidobacterium spp ., and Bacteroides fragilis , is critical for ICI therapy.…”