Bacterial Pigments as Potential Antitumor Agents Against Gastrointestinal Cancers: A Comprehensive Systematic Review

Gastrointestinal cancers (GICs) constitute one of the leading causes of cancer-related morbidity and mortality worldwide. Despite currently available therapeutic strategies, new approaches and procedures are needed for their prevention and treatment. In this context, bacterial pigments are compounds with diverse biological activities, including anticancer properties. The aim of this systematic review was to analyze the in vitro antitumor activity of pigments derived from bacteria against GICs. A total of 350 articles published between January 2015 and January 2025 were identified from three electronic databases, although only 27 were finally selected after following established inclusion and exclusion criteria. The results showed that prodigiosin was the most frequently studied bacterial pigment, followed by phycocyanin and violacein, whereas colorectal and liver cancers were the most common types of GICs in which these pigments were tested. In addition, these in vitro studies reflected the mechanisms of action responsible for the antiproliferative activity of bacterial pigments, including cell cycle arrest, apoptosis induction, autophagy modulation, and oxidative stress. In conclusion, the great ability of bacteria to produce pigments provides a potentially valuable source of novel candidate compounds for cancer therapy, but further studies in this field will be necessary to prove their value as antitumor agents.