Streptomyces, shared microbiome member of soil and gut, as 'old friends' against colon cancer.

Inflammation contributes to colon cancer initiation. The disease along with allergy and autoimmunity has been on the rise in Western and more recently in developing countries. This shared rise may imply a shared cause. Streptomycetes are known as soil residents and produce numerous antiproliferative, anti-inflammatory/immunosuppressive compounds, e.g. rapamycin and tacrolimus. Recently, Streptomyces has been shown in gut microbiome with a lower prevalence in humans than nonhumans whose microbiomes might be more representative of past humans' in a hunter-gatherer and farming environment. It was previously suggested that Streptomyces producing antiproliferatives/immunosuppressants would be 'old friends' against allergy and autoimmunity as well as inflammatory bowel diseases. Here, it is suggested that these streptomycetes within gut microbiome have also been evolved as 'old friends' to suppress colon tumorigenesis through their numerous antiproliferatives/immunosuppressants. Subsequently, the shortage of exposure to nature in our current lifestyle has cost us the shortage of these friends and vulnerability to colon cancer. An attractive research area in the future would be whether the shortage of Streptomyces exposure can be the underlying reason for colon cancer, allergy and autoimmunity rise, and if the restoration of these 'old friends' through probiotics or more exposure to nature can prevent colon cancer.