The microbiome and lung cancer

The microbiome is the ecological community of commensal, symbiotic, and pathogenic microorganisms that share our body space (1). These microorganisms include protozoa, fungi, bacteria, and viruses, and form organ-specific microbial communities. The size and composition of the microbiome vary from one body part to another, are affected by host and environmental factors, and can contribute to both disease and the body’s response to it. According to current estimates, the number of microbial cells is equal to the number of host cells and the total microbiome constitutes 0.2 kg in weight (2). It is a well-known fact that microbial organisms have been the cause of infectious diseases and morbidity in humans. However, an increasing level of evidence currently supports the role of microbial etiopathogenesis for non-infectious diseases including cancer (3). Epidemiological studies in humans were initially able to show association of microorganisms with cancer. Animal models were then used to prove an etiopathogenic role of specific microorganisms in human cancer. The goal of this manuscript is to briefly summarize the current state of knowledge of various roles played by microorganisms as related to cancer. Additionally, the putative role of microbiome in lung cancer is discussed with a brief discussion on the methods for isolation of microbiome from human samples for genomic sequencing. The intent of the review is to provide a primer and a summary of current knowledge of the field to clinicians treating lung cancer