Lactobacilli Supernatants Enhance Sensitivity Of Triple Negative Breast Cancer Cells To Cisplatin

Background &.ObjectiveThe prognosis of triple negative breast cancer is poor,and the chemotherapy is generally the preferred method.Cisplatin(DDP),a representative of the platinum drugs,is one of the most commonly used chemotherapy drugs,which can be used as rescue treatment of triple negative breast cancer or second-line chemotherapy of postoperative recurrence of breast cancer.The mechanism of DDP is to interfere the replication of DNA,and its target is the purine and pyrimidine bases of DNA.In clinical practice,a new research idea is to improve the sensitivity of old drugs,and also to avoid the side effects with dose dependently increasing.That’s why the study of cisplatin resistance become more and more popular.Piwil2 is a member of the cancer testis gene family,which is only expressed in spermatogenic cells,but not in other normal tissues.And in recent years,Piwil2 has been found that it can repair DNA damage,this phenomenon may suggest a novel mechanism of DDP resistance.In recent years,a variety of beneficial functions of lactobacilli,including the regulation of intestinal flora,immune regulation,anti-tumor effect have been found,making the study of lactobacilli to become popular,as well.It is found that LS can down regulate the expression of Piwil2 in breast cancer cells.As there is a close relationship between the DDP anti-tumor mechanism and the injury of tumor DNA,while Piwil2 gene is closely related to DNA repair.Meanwhile,a study found that silencing the expression of Piwil2 in cervical cancer cell line could enhance the sensitivity of cells to DDP,which has not been reported in breast cancer cell lines;another study found that LS could down-regulate the expression of Piwil2 gene in breast cancer cells MDA-MB-231.So we wonder whether Piwil2 is related to cisplatin resistance and whether LS can enhance the sensitivity of cisplatin via down-regulation of Piwil2.That’s why we came up with the idea of the study and the aim of our study was to investigate the effect of lactobacilli supernatants on sensitivity of breast cancer cell line MDA-MB-231 to Cisplatin and its mechanism.Methods CCK8 was used to observe the proliferation of triple negative breast cancer cells MDA-MB-231 treated with different DDP(0、1、2、3、4、5μg/ml)and LS(1%、5%、10%、20% v/v)for 24 h,respectively.Western blotting was used to detect the expression of Piwil2 in MDA-MB-231 cells treated as above.After Piwil2 siRNA was transfected in MDA-MB-231 cells to silence the expression of Piwil2,the effect of Piwil2-silenced was measured by western blotting and the proliferation of MDA-MB-231 cells was detected by CCK8.As above we also observed the inhibition of proliferation of MDA-MB-231 cells treated with Combination of LS(1%、5%、10%、20% v/v)and DDP(2μg/ml)for 24 h and the expression of Piwil2.Results When the concentration was higher than 3μg/ml,DDP could inhibit the proliferation of MDA-MB-231 cells(P<0.05),while the concentration was lower than 2μg/ml DDP could not effectively inhibit the proliferation of cells.DDP up-regulated the expression of Piwil2 protein in a dose-dependent manner.And siRNA silencing the expression of Piwil2 could recover the sensitivity of MDA-MB-231 cells to 2μg/ml DDP.Compared with MRS group,LS down-regulated the expression of Piwil2 protein in a dose-dependent manner but did not affect cell proliferation.Compared with group of 2μg/ml DDP,the expression of Piwil2 protein was down-regulated and the cell proliferation was more inhibited treated with combination of 2μg/ml DDP and 20% LS(P <0.05).Conclusion Upregulation of Piwil2 gene might lead to the resistance of triple negative breast cancer cells to DDP.Silencing the expression of Piwil2 could enhance the sensitivity of MDA-MB-231 cells to DDP and lactobacilli supernatants can also enhance sensitivity of MDA-MB-231 cells to DDP via downregulation of Piwil2.Significance It is the first time to study the relationship between LS and sensitivity of DDP.And it is also initial to raise that LS can enhance the sensitivity of DDP.The biotherapy insisted the notion of probiotics of lactobacilli,meanwhile,it provided a novel strategy to study the resistance of cisplatin.Because of its safety,low costs and good prospect,it needs further study in the future.