Inhibitory effect of DAPT on Notch signaling pathway in curcumin mediated photodynamic therapy for cervical cancer xenografts in nude mice

Abstract

Objective: Curcumin was used as photosensitizers in photodynamic therapy on cervical cancer xenografts in nude mice.Analysis the expression changes of Notch and downstream gene as NF-κB and VEGF before and after DAPT inhibition of Notch signaling pathway in vivo experiments.Our aim was to investigate the possible mechanism of Notch signaling pathway in the treatment of cervical cancer with PDT. Methods: A cervical cancer model of nude mice was established by subcutaneous inoculation of human cervical cancer Me180 cells 200 μl.After the success of the model, the experimental animals were divided into 4 groups (model group, curcumin PDT group, simple DAPT group, curcumin-PDT+ DAPT group), each group was 12.Tumor volume changes were analyzed and HE staining was observed in each group.MRNA and protein expression of Notch1 and its downstream NF-κB, VEGF were detected by RT-PCR, immunohistochemistry and Western blot before and after inhibition of Notch signaling pathway by DAPT. Results: Except the control group, the tumor volume of the other three groups remained unchanged or slightly reduced after 1-7 days of treatment.The difference was significant (P<0.05). HE staining showed the most obvious necrosis of curcumin-PDT group with DAPT.Both DAPT and curcumin-PDT could reduce the expression level of Notch1 in mRNA.The inhibition rates were 42.17% and 40.54%, respectively.And the inhibitory effect of curcumin-PDT with DAPT on Notch-1 was the strongest (79.22%) (P<0.01), and two of them had synergistic effect after combination with curcumin-PDT.But the expression of Notch-2 has no obvious inhibitory effect (P>0.05). Both DAPT and curcumin-PDT can inhibit the protein expression of Notch1, NF-κB and VEGF, and two of them have synergistic effect after combined use. Conclusions: DAPT can effectively block the Notch signaling pathway and inhibit the proliferation of cervical cancer cell line Me180.The application of DAPT to inhibit Notch signaling pathway after photodynamic therapy can achieve synergistic effect, which is mainly related to the down-regulation of the expression of Notch1 and NF-κB.Notch signaling pathway may be one of the targets of curcumin-PDT photodynamic therapy.