Investigation of the protective and therapeutic effects of <i>Lactobacillus casei</i> and <i>Saccharomyces cerevisiae</i> in a breast cancer mouse model

Abstract

<abstract><sec> <title>Introduction</title> <p>The development of novel strategies for cancer therapy is crucial to improve standard treatment protocols.</p> </sec><sec> <title>Aim</title> <p>This study aimed to determine the protective and therapeutic effects of heat-killed preparations of <italic>Lactobacillus casei</italic> and <italic>Saccharomyces cerevisiae</italic> in a breast cancer mouse model.</p> </sec><sec> <title>Methods</title> <p>Forty-two female BALB/c mice (7–8 weeks old) were divided into six groups (seven mice per group). Four groups were injected with 10⁷ Ehrlich ascites tumor (EAT) cells suspended in phosphate-buffered saline (PBS) subcutaneously into the left side of the mammary fat pad. Tumor growth was monitored weekly until all animals developed a palpable tumor. The tumor-bearing mice in the experimental groups received heat-killed <italic>L. casei</italic> or <italic>S. cerevisiae</italic> three times per week for 35 days. The mice in the control group received PBS. The remaining two groups received heated <italic>L. casei</italic> or <italic>S. cerevisiae</italic> and then were injected with EAT cells. After 35 days, all mice were sacrificed to determine the immune response.</p> </sec><sec> <title>Results</title> <p>Animals that received heated <italic>S. cerevisiae</italic> exhibited the lowest rate of tumor growth compared with the other groups. TGF-β and IL-4 secretion was increased in all mice, whereas the secretion of INF-γ and IL-10 was decreased in breast tissues. Moreover, at the histopathological level, the volume of viable tumor in the control group was higher than in the treated groups.</p> </sec><sec> <title>Conclusion</title> <p>Supplementary treatment with <italic>S. cerevisiae</italic> resulted in the best outcome in the breast cancer model compared with other treated and vaccinated groups.</p> </sec></abstract>