Abstract B81: Prostate 5LX® inhibits proliferation of prostate cancer cells through alteration of inflammatory pathways

Abstract

Abstract Purpose: Inflammation has been recognized as a key factor in the development of age-related degenerative diseases including cancer. Among important pro-inflammatory factors, bioactive lipids derived from cyclooxygenase (COX) or lipoxygenase (LOX) enzymes have been implicated as key targets for treatment and prevention of cancers. Here we report the effect of a multi-herb product “Prostate 5LX” on metabolism of inflammatory mediators in human prostate cancer and rat macrophage cells and their association with anti-proliferative activity. Methods: The effect of Prostate 5LX and its individual components on eicosanoid metabolism in human prostate cancer PC3, LNCaP, rat leukemia RBL-1 and macrophage RAW267.4 cells were examined using a validated LC/MS/MS analytical method. The effect of this natural product on the expression of inflammation associated genes in RAW267.4 cells was measured using TaqMan inflammation array kits and RT-PCR. Protein expression of relevant enzymes was evaluated by Western blot using appropriate antibodies. Results: When PC3 cells were treated with as little as 50 μg (0.1μl) Prostate 5LX/ml, the relative formation of 5-LOX products, LTB4 and 5-HETE was reduced by 69.2% and 36.7%, respectively. Similarly, Prostate 5LX at this concentration almost totally blocked the formation of LTB4 and 5-HETE in RBL-1 cells which are known to have relatively higher levels of 5-LOX and are a good model for evaluation of 5-LOX activity. The effect of Prostate 5LX on inhibition of 5-LOX activity was concentration-dependent. Unexpectedly, the level of 12-HETE, a 12-LOX metabolite, in PC3 or RBL-1 cells treated with Prostate 5LX was also significantly reduced in a concentration-dependent manner compared to untreated controls. To further our understanding of the role of individual botanical extracts in contributing to these unique biological activities, the effect of individual extracts on 5-LOX and 12-LOX metabolism was evaluated against the parent product in RBL-1 cells. While Saw Palmetto (80 μg/ml), green tea (50 μg/ml) and rosemary (10 μg/ml) significantly inhibited formation of 5-HETE by 67.1±11.2%, 45.3±8.3% and 68.5± 12.1%, respectively, stinging nettle (50 μg/ml) extract inhibited production of 12-HETE by 46.1% in RBL-1 cells. Intriguingly, the inhibitory effect of Prostate 5LX in the concentration comparable to that used for those individual botanical extracts, was much more stronger than any of the individual components evidenced by a 97.1% reduced formation of 5-HETE. The expression of both 5-LOX and 12-LOX proteins was reduced by Prostate 5LX in PC3, LNCaP and RBL-1 cells. Furthermore, the expression of LTA4 hydrolyase and leukotriene receptors were also markedly reduced by Prostate 5LX in Raw 267.4 cells. Interestingly, the growth of prostate cancer PC3 and LNCaP cells were significantly inhibited by Prostate 5LX (250 μg/ml) and these inhibitory effects appeared to be mediated through inhibition of 5-LOX and 12-LOX pathways in LNCaP and PC3 cells, respectively. Conclusions: Taken together, these preliminary data suggest that Prostate 5LX is capable of inhibiting the proliferation of prostate cancer cells mediated by alteration of lipoxygenase pathways, especially 5- and 12-LOX pathways. Given that inflammation plays an important role in prostate cancer initiation and development, these data may provide new insight on how this natural product affects prostate health, particularly prevents the development of prostate cancer. Citation Information: Cancer Prev Res 2011;4(10 Suppl):B81.