In vivo anti-prostate cancer properties of parthenolide
Authors: Christopher Sweeney, Timothy De Grado, Liang Cheng, Vetrichelvan Jayaprakasan, Brandon Washington, Thomas Gardner, Gary Hutchins, Poornima Nakshatri, Harikrishna Nakshatri
Journal: Cancer Research (2004)

4568  INTRODUCTION: We have previously reported the ability of parthenolide to inhibit prostate cancer cell (LNCaP, PC-3) growth as well as angiogenesis in vitro and in vivo. Parthenolide has been shown to inhibit Nuclear Factor-kappa B DNA binding. Experiments detailing the translatability of this data for possible clinical use of parthenolide are described. METHODS: Electromobility shift assay was performed to assess NF-kappa B DNA binding in CWR22Rv1 cells (androgen-responsive but androgen-independent human prostate cancer) with and without parthenolide treatment. MTS and clonogenic assays were performed to determine parthenolide’s IC50 in the CWR22Rv1 cell line in vitro. An established heterotopic xenograft model of subcutaneous CWR22Rv1 cells was employed with four arms: solvent control, 40 mg/kg/day parthenolide by oral gavage, 5 mg/kg/week docetaxel intraperitoneally and the combination of docetaxel plus parthenolide. There were approximately 20 mice in each arm and treatment was commenced 14 days after implantation. Small animal PET imaging using [11C]CO and [18F]choline (FCH) was performed on a random subset of four mice from each group to assess in vivo blood volume and choline metabolism, respectively. Immunohistochemistry (IHC) staining of the p65 subunit of NF-kappa B was performed to determine its frequency and location in 97 human prostatectomy specimens. RESULTS: Constitutive NF-kappa B DNA binding was present in the CWR22Rv1 cell line and inhibited by parthenolide. Parthenolide induced a dose dependent inhibition of CWR22Rv1 proliferation: IC50 - MTT assay: 5 μM (48 hour exposure); clonogenic assay: 1 μM (24 hour exposure). The percent inhibition of tumor volume with each treatment arm compared with solvent control at days 22 and 28 of treatment were: parthenolide - 17 and 24%; docetaxel - 17 and 0%; combination −57 and 55% (combination versus control - p = 0.01). The relative blood volume, expressed as the ratio of tumor surface to muscle [11C]CO concentrations, was 1.31±0.73 for solvent control; 1.27±0.86 for parthenolide; 1.19±0.29 for docetaxel and 0.50±0.13 for the combination (combination vs. solvent control p = 0.04). FCH uptake was also significantly decreased in the combination group (control=1.15±0.10; combination=0.74±0.24, p=0.05). IHC of prostatectomy specimens: normal glands had 14.7% (Range: 0-50%) of cells stain for p65 compared with 79.2% (R: 0-95%) and 88.7% (R: 30-95%) of prostatic intra-epithelial neoplasia and adenocarcinoma areas respectively. CONCLUSION: NF-kappa B is constitutively active in prostate cancer cell lines and is over-expressed in neoplastic prostatic tissue versus normal prostate epithelium. Parthenolide can inhibit NF-kappa B DNA binding and cancer cell proliferation in vitro. Moreover, parthenolide has modest anti-cancer activity as a single agent in vivo but significantly augments the anti-cancer and anti-angiogenic activity of docetaxel in vivo. Supported by DOD and NIH.