DAPT Enhances Sensitivity Of MDA-MB-231 Cells To Doxorubicin

Objective This work aimed to determined the inhibitory effect of y-secretase inhibitor DAPT and doxorubicin (Dox) on cell proliferation, cell cycle distribution, apoptosis and tumor xenografts of human triple negative breast cancer MDA-MB-231 cell lines.Methods The inhibitory effect of DAPT and Dox on the growth of MDA-MB-231 cell lines in vitro was tested by Cell Counting Kit-8(CCK-8) assay. The cell apoptosis and cell cycle distribution was detected by flow cytometry. The nude mice injected subcutaneously with MDA-MB-231 cell lines were treated with DAPT, Dox or combination of both by intraperitoneal injection. Tumor volume and total body weight were measured every three days and drug toxicity was monitored by weight loss. The expression of Notch-1, HES-1, BCL-2, Bax, CyclinDl and PTEN protein was detected by Western Blot.Results CCK-8 results showed that DAPT alone could inhibit the growth of human triple negative breast cancer MDA-MB-231 cell lines. The combined therapy of DAPT and Dox is more effective than the single agent with either DAPT or Dox alone (P<0.05). The combined treatment of DAPT and Dox induces cell cycle recession and promotes apoptosis of MDA-MB-231 cell lines more significantly than the single agent with either DAPT or Dox alone (P<0.05). Enhanced antitumor activity was observed in mice treated with the combination of DAPT and Dox, compared with DAPT or Dox alone(P<0.05). Combined treatment with DAPT and Dox decreased body weight about 20% than the single agent with either DAPT or Dox alone (P<0.05). Western blot analysis results showed that the protein of Notch-1 and CyclinDl of the group treated with DAPT and Dox was lower than that in other treatment groups(P<0.05). However, an induction of PTEN and pro-apoptotic protein Bax expression were observed in combined treatment group(P<0.05).Conclusion DAPT could enhance the sensitivity to Dox in MDA-MB-231 cell lines, but the combined treatment is stressful. The combined treatment induced the downregulation of Notch-1,HES-1, BCL-2 and CyclinDl and upregulation of PTEN and Bax protein expressions. This could be one of the synergistic antitumor mechanisms of the two drugs.