Previously, we showed that the growth, antibiotic resistance, and biofilm formation properties of the pathogens Pseudomonas aeruginosa and Klebsiella pneumonia were tremendously inhibited by the cell-free supernatant of the oral probiotic Streptococcus salivarius M18. These anti-pathogenic activities of the supernatant were more efficient under acidic conditions. The present approach takes advantage of the acidic nature of the tumor microenvironment to evaluate the effect of the S. salivarius M18 postbiotics on colon cancer cells. In both two-dimensional (2D) and three-dimensional (3D) cell culture models, S. salivarius M18 cell-free supernatant showed anti-cancer actions in the pH conditions mimicking the acidity of the tumor. The inhibitory effect was more prominent when the colon cancer cells have been treated with the cell-free supernatant obtained from the inulin incubated S. salivarius M18. The results of this study point out the potential of the S. salivarius M18 functional probiotic products to be used for targeting low pH environments including the unique acidic microenvironment of tumors.

之前，我们发现口服益生菌唾液链球菌M18的无细胞上清液极大地抑制了铜绿假单胞菌和肺炎克雷伯菌的生长、抗生素耐药性和生物膜形成特性。上清液的这些抗病原体活性在酸性条件下更有效。本方法利用肿瘤微环境的酸性来评估唾液链球菌 M18 后生元对结肠癌细胞的影响。在二维 (2D) 和三维 (3D) 细胞培养模型中，唾液链球菌M18 无细胞上清液在模拟肿瘤酸度的 pH 条件下显示出抗癌作用。当用从菊糖孵育的唾液链球菌M18 中获得的无细胞上清液处理结肠癌细胞时，抑制作用更为显着。这项研究的结果指出了唾液链球菌M18 功能性益生菌产品用于靶向低 pH 环境（包括肿瘤独特的酸性微环境）的潜力。