Therapeutic Role of Secondary Metabolites from Probiotic Strains for Ehrlich Solid Tumors in Mice

This study aimed to screen the bioactive components in Streptococcus equinus WC₁ (SE-WC₁) and Limosilactobacillus reuteri GM₄ (LR-GM₄) and estimate the therapeutic role in Ehrlich solid tumors (EST) mice model. Forty-four male albino EST mice were assigned into 7 groups and treated daily for 2 weeks, including the EST group, the EST mice that received SE-WC₁ at a low or a high dose (0.5 ml *10⁶ or 0.5 ml *10⁸ cfu), the EST mice that received LR-GM₄ at the low or the high dose (0.5 ml *10⁶ or 0.5 ml *10⁸ cfu), and the EST mice that received SE-WC₁ plus LR-GM₄ at the low or the high dose. Tumors were harvested, weighed, examined, and used for the determination of apoptosis-related gene expression. Samples of the intestine, liver, and kidney were gathered for histological examination. The GC–MS identified 24 and 36 bioactive compounds in SE-WC₁ and LR-GM₄, respectively. The main compound in SE-WC₁ was lupeol; however, the main compound in LR-GM₄ was retinaldehyde. EST mice showed disturbances in Bcl-2, Bax, and p53 mRNA expression along with histological changes in the intestine, liver, and kidney. Administration of both bacterial strains reduced the tumor weight, alleviated the disturbances in the gene expression, and improved the histological structure of the intestine, liver, and kidney in a dose-dependent. Moreover, LR-GM₄ was more effective than SE-WC₁ due to its higher content of bioactive compounds. It could be concluded that these strains of probiotics are promising for the treatment of solid tumors.