双歧杆菌表面分子诱导大肠癌细胞分化的研究

摘要

Objective　To investigate the direct antitumor effect of several surface molecules of Bifidobacterium bifidum 1101 such as whole peptidoglycan (WPG), lipoteichoic acid (LTA), and polysaccharides (PS) on human colonic adenocarcinoma cell line LoVo. Methods　MTT assay and flow cytometry (FCM) were used to evaluate the effect of Bifidobacterial surface molecules on the growth of LoVo cells. Morphological study, fluorescent polarimetry and differentiation-specific enzyme analysis were used to determine whether LTA treatment could induce the differentiation of the cells. Results　LTA but not WPG or PS significantly inhibited the proliferation of LoVo cells in a dose and time dependent manner. Cell cycle analysis by FCM revealed that LTA induced changes in cycle distribution resulting in G0/G1 phase commitment. Morphological alterations observed by light and electron microscopy indicated maturity of cytoplasm and nucleus following treatment by 50μg/ml of LTA. Membrane fluidity was also altered, and intestinal alkaline phosphatase specific for the differentiation of LoVo cells roused dramatically during culture in LTA. It was further found that LTA elevated ［Ca2+］i which resulted from Ca2+ influx instead of the release of stored calcium. Conclusion　These observations indicated that LTA was able to inhibit the growth of LoVo cells and induce the differentiation of the cells. Calcium influx may play an important role in this process.%目的研究双歧杆菌表面分子完整肽聚糖（whole peptidoglycan, WPG）、脂磷壁酸（lipoteichoic acid, LTA）和多糖（polysaccharides, PS）的直接抗肿瘤作用。方法采用MTT、形态学、流式细胞仪分析、荧光偏振以及特征性分化酶检测等方法观察了它们对培养的LoVo细胞生长的抑制作用及可能的机理。结果 LTA抑制LoVo细胞的生长，将细胞阻滞于G0/G1期。50μg/ml LTA使细胞核与细胞浆向成熟细胞分化，并且降低细胞膜的流动性。LoVo细胞特征性分化酶——肠型碱性磷酸酶的合成亦显著增加。LTA还诱导细胞内钙离子浓度增加，增加的钙离子来自于外钙内流而非内贮钙释放。结论 LTA作用于LoVo细胞后，直接抑制了该细胞的生长，并诱导LoVo细胞向成熟细胞分化，钙离子内流引起的信号传导在此过程中可能发挥了重要的作用。