Colorectal Cancer and Probiotics: Are Bugs Really Drugs?

Abstract

Colorectal cancer (CRC) is one of the most common types of cancer worldwide. There are many factors that predispose a patient to the disease such as age, family history, ethnicity, and lifestyle. There are different genetic factors and diseases that also increase a person's risk for developing CRC. Studies have found associations between gut microbiome and the risk for developing versus protection against CRC. Normal gut microbiome aid in daily functions of the human body such as absorption, metabolism, detoxification, and regulation of inflammation. While some species of bacteria prevent CRC development and aid in therapeutic responses to various treatment regiments, other species seem to promote CRC pathogenesis. In this regard, many studies have been conducted to not only understand the biology behind these opposing different bacterial species; but also to determine if supplementation of these tumor opposing bacterial species as probiotics lends toward decreased risk of CRC development and improved therapeutic responses in patients with CRC. In this literature review, we aim to discuss the basics on colorectal cancer (epidemiology, risk factors, targets, treatments), discuss associations between different bacterial strains and CRC, and discuss probiotics and their roles in CRC prevention and treatment.

Keywords: bacteria; chemoprevention; colorectal cancer; gut microflora; probiotics.

Figure 1

Mechanisms of probiotics. Probiotics increase other beneficial bacteria, while decreasing pathogenic bacteria and their harmful mechanisms. They have also been shown to increase short chain fatty acids (SCFAs) and antioxidants, while also decreasing carcinogens in the intestines. Possible actions that probiotics have are to increase tumor cell apoptosis and increase in tumor suppressor genes; these may be possible areas to research further into for colorectal cancer (CRC) prevention and adjuvant therapies.