Flavokawain B, a kava chalcone, induces apoptosis via up-regulation of death-receptor 5 and Bim expression in androgen receptor negative, hormonal refractory prostate cancer cell lines and reduces tumor growth

Authors

  • Yaxiong Tang,

    1. Department of Urology, University of California, Irvine, Orange, CA
    Current affiliation:
    1. Chengdu Institute of Biology, the Chinese Academy of Sciences, Chengdu, Sichuan, People's Republic of China 610041
    Search for more papers by this author
    • Yaxiong Tang and Xuesen Li contributed equally to this work.

  • Xuesen Li,

    1. Department of Urology, University of California, Irvine, Orange, CA
    Search for more papers by this author
    • Yaxiong Tang and Xuesen Li contributed equally to this work.

  • Zhongbo Liu,

    1. Department of Urology, University of California, Irvine, Orange, CA
    Search for more papers by this author
  • Anne R. Simoneau,

    1. Department of Urology, University of California, Irvine, Orange, CA
    Search for more papers by this author
  • Jun Xie,

    1. Department of Pharmaceutical Sciences, University of California, Irvine, Orange, CA
    Search for more papers by this author
  • Xiaolin Zi

    Corresponding author
    1. Department of Urology, University of California, Irvine, Orange, CA
    2. Department of Chao Family Comprehensive Cancer Center, University of California, Irvine, Orange, CA
    3. Department of Pharmaceutical Sciences, University of California, Irvine, Orange, CA
    • Department of Urology, University of California, Irvine, 101 The City Drive South, Bldg. 55 Rm. 302, Orange, CA 92868, USA
    Search for more papers by this author
    • Tel.: 714-456-8316


Abstract

Limited success has been achieved in extending the survival of patients with metastatic and hormone-refractory prostate cancer (HRPC). There is a strong need for novel agents in the treatment and prevention of HRPC. We have shown that flavokawain B (FKB), a kava chalcone, is about 4- to 12-fold more effective in reducing the cell viabilities of androgen receptor (AR)-negative, HRPC cell lines DU145 and PC-3 than AR-positive, hormone-sensitive prostate cancer cell lines LAPC4 and LNCaP, with minimal effect on normal prostatic epithelial and stromal cells. FKB induces apoptosis with an associated increased expression of proapoptotic proteins: death receptor-5, Bim and Puma and a decreased expression of inhibitors of apoptosis protein: XIAP and survivin. Among them, Bim expression was significantly induced by FKB as early as 4 hr of the treatment. Knockdown of Bim expression by short-hairpin RNAs attenuates the inhibitory effect on anchorage-dependent and -independent growth and caspase cleavages induced by FKB. These findings suggest that the effect of FKB, at least in part, requires Bim expression. In addition, FKB synergizes with TRAIL for markedly enhanced induction of apoptosis. Furthermore, FKB treatment of mice bearing DU145 xenograft tumors results in tumor growth inhibition and increases Bim expression in tumor tissues. Together, these results suggest robust mechanisms for FKB induction of apoptosis preferentially for HRPC and the potential usefulness of FKB for prevention and treatment of HRPC in an adjuvant setting.

Ancillary