Dysbiosis of the gut microbiome caused by cigarette smoke exposure (CSE) may facilitate tumor progression, according to study results intended to be presented at Digestive Disease Week 2020. Researchers note that targeting the microbiome could be a potential strategy in neutralizing the detrimental effects of smoking on the progression of cancer.
CSE is a known risk factor for a number of human cancers. Though many have highlighted the presence of carcinogenic compounds in CSE as the cause for this increased risk, the exact molecular mechanisms underlying the interaction are still unknown.
The researchers conducting the present study randomized 6 to 8-week old C57BL/6 mice into gut sterile or control groups. These groups were further divided into CS exposed and non-exposed groups. After 4 weeks, mice were subcutaneously injected with cells from either pancreatic, colon, or bladder cancer lines. The researchers monitored tumor size over 2 months. They also conducted the same experiments in mice lacking an immune response. The researchers also determined the effect of a smoking analogue compound on mice exposed to and not exposed to antibiotics.
Results showed that CSE promoted cancer cell growth in all cell lines and that elimination of the gut microbiome by antibiotics protected against smoke-induced cancer progression. The researchers found that CSE and gut microbiome depletion did not decrease tumor growth in mice lacking an immune response. Furthermore, mice exposed to the smoking analogue compound, but no antibiotics, showed enrichment of Bacteriodetes phyla, as well as the genera Clostridium and Parabacteriodes.
The researchers state that their “study provides novel insights into how smoking/smoking analogs and gut-microbiome interact to influence cancer progression.”
Sharma P, Jain T, Sethi V et al. Cigarette smoke exposure promotes cancer progression through gut microbial dysbiosis. Abstract intended to be presented at Digestive Disease Week 2020; May 2020 (canceled). Chicago, Illinois, United States of America.