Role of Probiotics in Breast Cancer: From Experimental Models to Clinical Translation

Abstract

In spite of considerable advances in its management, breast cancer continues being an important medical issue affecting predominantly reproductive females. Recent investigations have suggested that microbiotas of the gut and breasts may contribute to the onset of breast cancer and further breast cancer development and treatment. In the current review, the epidemiologic, mechanistic, preclinical, and clinical literature about the relationship between the gut microbiota dysbiosis and breast cancer will be analyzed especially in regard to the gut-breast connection and probiotic use. Using novel methods of sequencing, researchers found that there were differences in microbiota profiles in the breast and disturbances in the compositions of both gut and breast microbiotas could participate in carcinogenesis, immunity failure, and abnormality in estrogen metabolism. Mechanisms behind these relationships may involve the following processes: reactivation of estrobolome, inflammation regulation, changes in intestinal barrier, transfer of microbe-associated metabolites, and epigenetics control. The dysbiosis of the microbiota is characterized by the decrease in the microbiota diversity, the reduction in the abundance of short chain fatty acid-producing bacteria, and an increase in pro-inflammatory microbes. Probiotics like Lactobacillus and Bifidobacterium could be useful in breast cancer treatment due to microbiota alteration, suppression of cancer-promoting enzymes, assistance in the process of detoxification of carcinogens, immunomodulation, oncogenic signaling modulation, and strengthening the integrity of the intestinal barrier. Preclinically, positive effect on tumor development and angiogenesis as well as better immune responses were expected. However, the necessity in further clinical trials exists.