The Role of Lactobacillus Strain Probiotics in Breast Cancer: Strain-Specific Mechanisms and Therapeutic Potential Beyond Probiotics.

As one of the most complex diseases, breast cancer (BC) is a leading cause of death among women globally, and various species of probiotics may offer benefits in managing BC treatment. While previous studies have examined the impact of potent probiotics concerning BC and its associated risk factors, particularly Lactobacillus and Bifidobacterium, it is essential to note that these effects are strain-specific. Research on the specific effects of different Lactobacillus strains in preventing or alleviating BC complications is limited, even though Lactobacillus has been extensively studied, especially in vitro and in vivo. In this regard, oral administration of Lactobacillus strains, including Lactobacillus acidophilus (L. acidophilus), Lacticaseibacillus casei (L. casei), Lacticaseibacillus helveticus (L. helveticus), Ligilactobacillus lactis (L. lactis), and Lactiplantibacillus plantarum (L. plantarum), significantly promotes immune responses and anti-cancer properties against BC. In addition, oral capsule supplements containing several Lactobacillus strains, such as Lacticaseibacillus rhamnosus (L. rhamnosus) and L. acidophilus, combined with Bifidobacteria or prebiotics (a synbiotic), have been clinically proven to be effective. Moreover, some anti-carcinogenic mechanisms of Lactobacillus strains may appear more prominent than others, which contribute to alleviating cancer complications. These include interactions with the gut microbiota, modulation of the immune system, induction of apoptosis, anti-inflammatory effects, the impact of probiotic-derived agents, and epigenetic regulation. This paper reviews the pathways related to Lactobacillus strains to understand their unique impacts on BC better and explores the potential mechanisms involved. Given the possible diversity of effects among different Lactobacillus strains, future research should focus on specific strains.