Despite the advances in diagnostic and therapeutic field, colorectal cancer (CRC) still remains the third most common cause of death worldwide, with more than 600,000 cancer-related deaths per year.

5-fluorouracil (5-FU), an antimetabolite in the fluoropyrimidine class, is the third most commonly used chemotherapeutic agent worldwide for the treatment of solid malignancies [1]. Despite advances in novel cancer therapies, commonly used in combination with fluoropyrimidines, 5-FU remains one of the most effective and safe chemotherapy agents to manage colorectal cancer (CRC).

DNA microsatellites are tandemly repeating short (1-6 base pairs) DNA motifs, such as mononucleotide (A)n, dinucleotide (CA)n, trinucleotide (CAG)n, and tetranucleotide (AAAG)n, with each motif potentially repeating up to 50 times.

The intestinal microbiota creates a bodily barrier for invading pathogen by using aggressive exclusion. Pathogens and immune cells can interact directly and dynamically with symbiotic bacteria, determining the pathophysiology and outcome of an infection. They can defend the host through a variety of processes, including attachment site occupancy, nutrition intake, metabolite competition, and the synthesis of antimicrobial compounds including bacteriocins that influence pathogen survival (a process referred to as colonization resistance).

The American Cancer Society estimates there will be 156,540 new diagnoses and 53,200 deaths from colorectal cancer (CRC) in the United States in 2020.