Search

Glycyrrhetinic acid is an active triterpenoid metabolite of glycyrrhizin abundantly present in licorice roots. Glycyrrhetinic acid exists as α and β stereo-isomeric forms. Both stereo-isomeric forms are known to have anti-inflammatory and anticancer activity. However, the effects and anticancer mechanism of α glycyrrhetinic acid in prostate cancer cells has not yet been evaluated. Therefore, we investigated the growth inhibition, induction of apoptosis and the anticancer mechanisms of 18α-glycyrrhetinic acid (AGA), on the androgen-independent metastatic prostate cancer cell line DU-145. Our results showed that AGA inhibited proliferation and growth of these cells by inducing apoptosis as determined by Annexin V and flow cytometry analyses. Our studies also showed that HUVEC tube formation was drastically reduced when cultured in conditioned medium of AGA-treated DU-145 cells. In addition, AGA treatment prevented the invasion of DU-145 prostate cancer cells on matrigel coated transwells via down-regulation of NF-κB (p65), VEGF and MMP-9 expression. Furthermore, AGA treatment also down-regulated the expression of pro-inflammatory cytokine/growth factor genes HMGB1, IL-6 and IL-8 in DU-145 cells. Interestingly, AGA simultaneously upregulated the expression of non-steroidal anti-inflammatory gene-1 (NAG-1) in DU-145 cells suggesting its anti-inflammatory activity on prostate cancer cells. Taken together, the results of this study suggest that AGA may be a promising anticancer agent that merits further investigation for the chemoprevention and treatment of prostate cancer.

Translationally controlled tumor protein (TCTP) is a novel anti apoptotic protein which is highly expressed in several cancer cell types including prostate cancer. However, studies investigating the role of TCTP in prostate cancer are scarce. Therefore, in this study we evaluated the effect of small interference RNA (siRNA) based knocking down of TCTP gene in prostate cancer cells. Cell proliferation and apoptosis were evaluated. Our results showed that TCTP is highly expressed in LNCaP cells compared to normal prostate epithelial cells. Transfection with TCTP siRNA specifically and drastically reduced the expression of both mRNA and protein levels of TCTP in LNCaP cells. The decreased expression of TCTP was associated with decreased viability of LNCaP cells. Further analysis of the transfected LNCaP cells showed that they undergo apoptosis via caspase-8 and caspase-3 dependent pathways. Results presented herein suggest a potential therapeutic application for prostate cancer by targeting TCTP gene using an siRNA approach.

High mobility group box protein 1 (HMGB1), transcriptional activity regulatory protein is associated with most cancers including prostate cancer. To investigate the effects of down-regulation of HMGB1 expression, we have transfected LNCaP cells with four short hairpin RNA (shRNA) targeting HMGB1 plasmid vectors. Transfection with the four shRNAs efficiently and specifically reduced the HMGB1 expression in LNCaP cells. The gene silencing effects on HMGB1 expression were subsequently confirmed by RT-PCR and immunoblotting analyses. Down-regulation of HMGB1 expression resulted in the inhibition of cell growth in LNCaP prostate cancer cells and the decreased cell number was due to transfected cells undergoing apoptosis via caspase-3-dependent pathways. These findings suggest that HMGB1 is critical for the survival of prostate cancer cells and targeted knockdown of HMGB1 mRNA can be used as a strategy to kill prostate cancer cells. Our findings may have some potential therapeutic relevance for treating prostate cancer.

Over 2 million Americans are currently living with prostate cancer. Current chemotherapeutic strategies are only partially effective in controlling the disease. There is always a need for an effective newer drug for treating prostate cancer. Use of active principles from medically important herbs has proven to be effective in treating various forms of cancers. Glycyrrhizin, a triterpene compound isolated from roots of licorice has been found to exhibit potent in vitro cytotoxic activity against several human cancer cell lines. In this study, we evaluated the effects of glycyrrhizin on the viability of two human prostate cancer cells LNCaP (hormone-dependent) and DU-145 (hormone-independent) in vitro. Cell viability assay showed that glycyrrhizin inhibited the cell proliferation of prostate cancer cells in a time- and dose-dependent manner. The decreased viability of prostate cancer cells was due to apoptosis as confirmed by Annexin-V FITC flow cytometric analyses. Glycyrrhizin also caused DNA damage in DU-145 and LNCaP cells in a time-dependent manner. Caspase-3 and -8 activities were not detected in glycyrrhizin-treated prostate cancer cells suggesting that caspase-independent pathways may be involved in the apoptotic mechanism. Collectively, these studies suggest that glycyrrhizin has therapeutic potential against prostate cancer.