Composition of the intestinal microbiota of female Wistar rats with chemically induced breast cancer and under various therapies

Abstract

Breast cancer (BC) is a serious problem that requires early diagnosis and timely successful therapy. An increasing number of studies reveal the relationship between microbiota disorders and the occurrence/progression of breast tumors. Intestinal microbiota is recognized as a kind of endocrine organ and may be considered as a potential diagnostic tumor marker. The research goal was to study and analyze changes in the intestinal microbiota by sequencing the 16S rRNA gene in female Wistar rats with chemically induced BC and subsequent chemotherapy, surgery, and a combination of these treatment methods. The studies were performed on mature female Wistar rats. At the beginning of the experiment, the Wistar female rats were 3 months old and weighed 250-300 g. Five groups of animals were formed for the study. Fecal samples from the studied groups of rats were collected for subsequent metagenomic analysis by sequencing the 16S rRNA gene (in vivo). The 16S rRNA sequencing method was performed using the MiSeq System (Illumina, USA) with the MiSeq Reagent Kit v2 (500-cycles) with paired-end reads of 2 × 250 bp. The study showed that most of the isolated bacteria in the experimental groups belonged to the Firmicutes and Bacteroidetes types. In the group with breast cancer, dysbiosis was found in the intestinal microflora due to increased level of Bacteroidetes and the number of Actinobacteria bacteria. After chemotherapy, decreased level of Firmicutes with increased levels of Bacteroidetes and Proteobacteria were found in the breast cancer group. After surgical treatment of breast cancer, increase of Verrucomicrobia was found due to the effect of Verrucomicrobia on the reparation of the surgical wound. In chemically induced BC as well as under different treatment methods, decreased Firmicutes/(Firmicutes + Bacteroidetes) ratio was found in the intestines of rats compared to the control group. Further studies are required to determine the possibility of using the studied ratio as an auxiliary diagnostic biomarker for BC.