Objective  To investigate targeted therapy of ovarian cancer with new fusion proteins that were produced by fusing the first 390 amino acids of diphtheria toxin (DT390) to the TMTP1 peptide.

  Methods  The cisplatin-resistant cell line, C13*, and cisplatin-sensitive cell line, OV2008, were selected as models and divided into control, TMTP1, DT390-TMTP1, DT390-biTMTP1, and DT390-triTMTP1 groups. Laser scanning confocal microscopy was used to observe nuclear morphology. 3-(4, 5-Dimethylthiazol-2-yl) -2, 5-diphenyltetrazolium bromide (MTT) and flow cytometry assays were used to detect cell survival and apoptosis, respectively. The formation of subcutaneous tumors in nude mice following injection of C13* cells was used to observe the formation and growth of ovarian cancer. Apoptosis of cells in the subcutaneous tumor tissue was detected by the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay.

  Results  Laser scanning confocal microscopy showed that DT390-biTMTP1 and DT390-triTMTP1 induced nuclear shrinkage and fragmentation. The MTT assay showed that cell survival was obviously reduced with increasing concentrations of DT390-biTMTP1 and DT390-triTMTP1. Flow cytometry revealed that DT390-biTMTP1 and DT390-triTMTP1 significantly increased cell apoptosis (P < 0.05). The apoptosis rates of the DT390-biTMTP1 and DT390-triTMTP1 groups were 66.0%±12.0% and 72.9%±4.6%, respectively. These were higher than the 55.5%±8.9% and 65.1%±9.8% obvserved in OV2008 cells. DT390-biTMTP1 and DT390-triTMTP1 significantly inhibited the tumor formation (P < 0.01) and growth (P < 0.05), and increased apoptosis (P < 0.05) of subcutaneous tumors. However, DT390-TMTP1 had insignificant effects on C13* and OV2008 cells.

  Conclusions  DT390-biTMTP1 and DT390-triTMTP1 preferentially targeted and inhibited ovarian cancer cells. These fusion proteins may be a promising strategy for clinical therapy of ovarian cancer.