Molecular Mechanisms of Probiotic Action Against Gastrointestinal Cancers

Gastrointestinal (GI) cancers represent a major global health burden. Among them, colorectal cancer (CRC) is the most common type, followed by esophagus, stomach, liver, and pancreatic cancer. Since disturbance of the gut microbiota has been directly associated with the development of severe health issues, including cancer, probiotic administration may induce dysbiosis reversion and ameliorate carcinogenesis. Therefore, manipulation of the gut microbiota composition based on probiotic utilization has gradually attained scientific interest as a potent therapeutic modality for GI cancers. This review aims to synthesize the current in vitro and in vivo evidence on probiotics' effectiveness in GI cancer chemoprevention and treatment. It also provides a classification of the fundamental anticancer features of probiotics, including antiproliferation and cell death induction, anticarcinogenic compound production, reduction in chemotherapy-related toxicity, gut microbiota modulation, intestinal barrier improvement, antioxidant activity, immunomodulatory/anti-inflammatory effects, and carcinogen detoxification. Finally, it underscores the future perspectives and challenges of probiotic administration to individuals. In this regard, it emphasizes the exploitation of advanced encapsulation techniques and the development of novel genetically engineered probiotics and next-generation probiotics as feasible ways to improve their bioavailability, ensure their targeted delivery, and eliminate their mild side effects to the host's health.