The andean anticancer herbal product BIRM causes destabilization of androgen receptor and induces caspase-8 mediated-apoptosis in prostate cancer
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Nagarajarao Shamaladevi1,*, Shinako Araki1,6,*, Dominic A. Lyn1, Rajnikanth Ayyathurai2, Jie Gao3, Vinata B. Lokeshwar4, Hugo Navarrete5, Bal L. Lokeshwar3
1Departments of Urology and Sylvester Cancer Center, Miller School of Medicine, University of Miami, Miami FL, USA
2Northwest Georgia Physicians Group, Gainesville, GA, USA
3Georgia Cancer Center and Department of Medicine, Augusta University, Augusta GA, USA
4Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta GA, USA
5Herbarium QCA, Pontificia Universidad Catolica del-Ecuador, Quito, Ecuador
6Dr. Shinako Araki is at Okayama University graduate school of Medicine, Okayama, Japan
*These authors contributed equally to this work
Bal L. Lokeshwar, email: [email protected]
Keywords: Anti-cancer herbal preparation, androgen receptor, prostate cancer, chemoprevention, caspase-8
Received: December 27, 2015 Accepted: September 25, 2016 Published: October 01, 2016
BIRM is an anticancer herbal formulation from Ecuador. Previous study established its antitumor and antimetastatic activity against prostate cancer models. The activity of BIRM against human prostate cancer (PCa) cells was investigated to uncover its mechanism of antitumor activity. In androgen receptor (AR)-expressing PCa cells BIRM was 2.5-fold (250%) more cytotoxic in presence of androgen (DHT) compared to cells grown in the absence of DHT. In AR-positive cells (LAPC-4 and LNCaP) BIRM caused a dose and time-dependent down-regulation of AR and increased apoptosis. Exposing cells to BIRM did not affect the synthesis of AR and AR promoter activity but increased degradation of AR via proteasome-pathway. BIRM caused destabilization of HSP90-AR association in LAPC-4 cells. It induced apoptosis in PCa cells by activation of caspase-8 via death receptor and FADD-mediated pathways. A synthetic inhibitor of Caspase-8 cleavage (IETD-CHO) aborted BIRM–induced apoptosis. The effect of BIRM on AKT-mediated survival pathway in both AR+ and AR- negative (PC-3 and DU145) showed decreased levels of p-AKTser 473 in all PCa cell lines. BIRM dosed by oral gavage in mice bearing PC-3ML tumors showed selective efficacy on tumor growth; before tumors are established but limited efficacy when treated on existing tumors. Moreover, BIRM inhibited the LNCaP tumor generated by orthotropic implantation into dorsal prostate of nude mice. Partial purification of BIRM by liquid-liquid extraction and further fractionation by HPLC showed 4-fold increased specific activity on PCa cells. These results demonstrate a mechanistic basis of anti-tumor activity of the herbal extract BIRM.
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