Anticancer Potential of Novel Curcumin Analogues towards Hormone-Refractory Prostate Cancer
Prostate cancer, a hormonally driven and dependent malignancy, is a leading cause of cancer-related deaths in men. Hormonal therapy including surgical castration and medical/chemical castration to cause regression of androgen-dependent tumors has become the standard therapy for the advanced stage of prostate cancer. However, recurrent prostate cancer is initially sensitive to hormone therapy. Over time most patients eventually fail this therapy and progress to a hormone insensitive form of prostate cancer classified as hormone-refractory prostate cancer (HRPC). At this stage, the median survival rate is less than 12 months and therapeutic options have shown little effect on the progression of the disease. Therefore, novel treatment strategies and drugs are urgently required for HRPC. The current project explored the cytotoxic effects and anticancer mechanism of new curcumin analogues towards HRPC in vitro. Androgen-independent prostate cancer cell lines PC-3 and DU145 were treated with a series of curcumin analogues at 0-10 μM for 72 h and cytotoxicity was determined by the sulforhodamine B (SRB) assay. RL118 and RL121 were found the most potent analogues with EC50 values of 0.50 and 0.58 μM in PC-3 cells and EC50 values of 0.76 and 0.69 μM in DU 145 cells, respectively. Subsequently, further studies were conducted using RL118 and RL121. Flow cytometry was performed to determine their effect on cell cycle and apoptosis. Both analogues increased the number of cells in the G2/M phase of the cell cycle and induced apoptosis as determined by flow cytometry. Specifically, in PC-3 cells, RL121 induced a significant 86% increase at 24 h and 57% increase at 48 h of G2/M phase cells compared to control, while RL118 caused a significant increase by 42% and 30% at 24 and 48 h in G2/M phase cells compared to control. Moreover, both RL118 and RL121 induced a substantial apoptosis in both cell lines. In DU 145 cells, a 38-fold increase in apoptotic cells by RL118 and 78-fold increase by RL121 compared to control occurred after 48 h. Furthermore, the effect of treatment on the expression of key proteins was also determined using Western blotting at 24, 48 h time points. Western blotting results showed that both analogues inhibited the expression of NFκB, β-catenin, EGFR, 4E-BP1, p-4E-BP1, mTOR, p-mTOR, AKT and p-AKT, as well as activated the expression of cleaved casepase-3. In particular, RL121 reduced the expression of p-4EBP1 and p-AKT in PC-3 cells by 95 % and 94% of control after 48 h and increased the expression of cleaved caspase 3 in DU 145 cells by 4.1 and 2.8-fold compared to control after 24 and 48 h. Thus, our findings provide evidence that RL118 and RL121 have potent anticancer activity in HPRC cells and both analogues warrant further examination in vivo.
Advisor: Rosengren, Rhonda J.
Degree Name: Master of Science
Degree Discipline: Pharmacology and Toxicology
Publisher: University of Otago
Keywords: Hormone-Refractory Prostate Cancer; curcumin analogues; in vitro
Research Type: Thesis