Cancer and the Microbiome
Cancer, which is the second-leading cause of death in the world, refers to the malignant diseases which are characterized by the development of abnormal cells that can divide uncontrollably and can infiltrate and affect normal body tissues. Cancer can develop from almost anywhere in the human body. Normally, human cells grow and divide to form new cells. When these cells grow old or become damaged, they die, and new cells take their place. However, this natural process of the cell cycle breaks down when cancer develops. As cells grow old, become damaged, or abnormal, these cells survive and keep growing aberrantly instead of dying. This process may result in the formation of abnormal growths, called tumors.
It has been shown that microbes may have an indirect role in cancer by causing inflammation, which then may influence the development of cancer. However, there are some other microbes that can have a direct role in cancer development and progression. H. pylori bacteria, which is the common cause of stomach ulcers, can play a role in the development of stomach and esophagus cancers. A number of viruses can be associated with cancer development. These include Hepatitis B and C virus which are known to be risk factors of liver cancer. Human papillomavirus, or HPV, which can be transmitted sexually is significantly associated with cervical cancers. Moreover, mononucleosis causing Epstein-Barr virus or EBV can be associated with the cancers of white blood cells- lymphomas.
A recent study also showed the significance of the gut microbiome in lung cancer. Conducting 30 lung cancer patients and 30 healthy controls, the authors of this study showed that there was no significant difference in microbial diversity (alpha diversity) between lung cancer patients and the controls. However, the authors found that the composition (beta diversity) differed significantly between lung cancer patients and the controls. In this case, the healthy controls had a higher abundance of the bacterial phylum Actinobacteria and genus Bifidobacterium, while the lung cancer patients demonstrated higher levels of Enterococcus. The authors showed that these bacteria acted as potential biomarkers for Lung malignancies, where they also showed that the aberrant function of gut microbiota in patients with lung cancer.
Another study showed that gut microbiota can significantly increase the efficacy of cancer treatments. The study found two bacterial groups, Bacteroides ovate and Bacteroides xylanisolvens, which showed a significant correlation with cancer treatment. When these bacterial species were administered orally in a murine lung cancer model, the efficacy of erlotinib significantly increased along with the expression of CXCL9 and IFN-γ.
These studies indicate that the gut microbiome can play a key role in both cancer detection and treatment. Therefore, further studies are a must for identifying the significance between gut microbes and other cancer types.
The diversity of gut microbiota
Picture Source: microbiota-site.com
