Abstract 2256: Triptolide inhibit malignant growth and telomerase activity in malignant neurofibromatosis cells.

Neurofibromatosis patients have an 8-13% risk of developing a malignant peripheral nerve sheath tumor (MPNST) which has a poor prognosis. Increasing telomerase activity and telomerase reverse transcriptase (TERT) mRNA were observed in 82% and 100% of the MPNST patients. Currently, there is no effective drug for MPNST. In this study, we explore the effect of Triptolide (TPL) on MPNST and its molecule mechanism. In vitro, human MPNST cell lines STS26T, T256 and ST88-14 were treated with TPL. Cell proliferation was measured with MTT assay; cell apoptosis was assayed with Annexin-V staining and Sub-G1 phase analysis. STS26T cells treated with TPL were harvested and then assessed for their caspase 9, 8 and 3 activity with fluorescence substrates. Protein and RNA were harvested for the assay of telomerase activity and TERT mRNA level. In vivo, STS26T, T265 and ST88-14 (5×106/site) cells were transplanted into nude mice. Mice bared tumor (100 mm3, STS26T) was treated with TPL (0.25 mg/kg, three times a week) for 4 weeks. Tumor weight was compared between TPL treated and the control group. The results showed that: 1) TPL inhibited the proliferation of STS26T and T256 cells in a dose and time dependent manner: The inhibition concentration (IC50) was 18.05 ng/ml, 15.0 ng/ml and 9.0 ng/ml for STS26T, T256 and ST-88, respectively, indicating that STS26T is more resistant to chemotherapy drug. As compared with IC50 of Taxol at 128 ng/ml, TPL was more potent in suppression of MPNST growth; 2) TPL induced apoptosis of MPNST cells as evidenced by the increased portion of cells in Annexin V positive staining and sub-G1 population. TPL at doses of 12.5-25 ng/ml showed an activation of apoptotic molecular; 3) TPL inhibited the relative telomerase activity (RTA) of STS26T and T256 cells. To reach similar inhibition of RAT, STS26T cells required a higher dose (36 ng/ml v.s. 9 ng/ml); 4) TPL inhibited TERT mRNA of STS26T cells. To define if the reduced telomerase activity was due to the reduction of the TERT synthesis, the effect of TPL on TERT mRNA was examined. TERT mRNA in STS26T cells was greatly reduced with TPL in time and dose dependent. 5) In vivo, TPL in low dose range (0.25 mg/kg) effectively inhibited aggressive xenograft of STS26T. TPL significantly reduced the tumor weight of STS26T as compared to the vehicle alone treated group (0.75 + 0.15g vs 3.1 + 0.45g, P The data demonstrate that TPL possesses potent inhibitory effect on the growth of MPNST tumor cells both in vitro and in vivo, which is related with its reduction of telomerase activity. TPL has a good potential to be developed as a new anti-MPNST drug. Citation Format: Shanmin Yang, Wei Wang, Luqiang Huang, Mei Zhang, Paul Okunieff, Lurong Zhang. Triptolide inhibit malignant growth and telomerase activity in malignant neurofibromatosis cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2256. doi:10.1158/1538-7445.AM2013-2256 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.