After amplification, the expected PCR products were Streptozotocin 18883-66-4 size fractionated onto a 2% agarose gel and stained with ethidium bromide. StatisticalAnalysis All cell culture based experiments were repeated three times. Western blotting and immunostaining results are presented from a representative experiment. The mean and SEM for tumor growth, prostate wetweight, BrdU labeling, Ki 67, and C/EBPa immunostaining index as well as luciferase reporter activities were shown. The significance of differences between groups were analyzed as described in our previous publications using the SPSS computer software. RESULTS GSK 3 Inhibition ReducesTumorGrowth of Prostate CancerXenografts inNudeMice We and others have shown that GSK 3 inhibition reduces androgen receptor mediated gene expression, AR protein levels and cell proliferation in androgen responsive prostate cancer cell lines in vitro. In this study, we extended these in vitro findings to an in vivo setting, xenograft models. We utilized two castration resistant prostate cancer cell lines, the AR positive C4 2 and the AR negative PC 3, in our experiments. For LiCl treatment, we used two different strategies, of which protocol A was to assess the xenograft tumor development/ growth, while protocol B was to assess the effect of GSK 3 inhibition on growth rate of existing tumors. Therefore, in protocol A GSK 3 inhibitor LiCl was delivered at the day after PC 3 cell inoculation and in protocol B LiCl treatment was started when the xenografts were established. In both protocols, LiCl was delivered at a daily dose of 2.0mg/kg of bodyweight. This lithium dose level was based on a previous report where a biological effect was observed in rat models, and is more than 100 fold lower that a therapeutic dose for mental diseases in mouse or human. In both protocols, no obvious abnormality of daily activities, such as apathy, asthenia, movement, drinking, eating, etc. or any sign of side effect were observed from LiCltreated animals. There was no significant difference of animal body weight between treatment and control groups. In protocol A, PC 3 xenografts were developed around 4 weeks after inoculation in PBS treated control animals with a 100% intake rate.
However, in LiCltreated animals, palpable xenograft development was delayed until 6 7 weeks after inoculation. When comparing tumor wet weight at the end of 8 week treatment between these two groups, LiCl treated animals showed a significant reduction compared to PBS control. In protocol B, when PC 3 xenografts were palpable, animals were treated with LiCl for 2 weeks.Tumor wet weight at the end of treatment was compared between LiCl treated and PBS control groups. As high throughput screening shown in Figure 1A, LiCl treatment also significantly reduced tumor wet weight compared to the PBS control. Next, since lithium also suppresses other enzymes besides GSK 3, we used the ATP non competitive GSK 3 specific small molecule inhibitor TDZD 8 to verify GSK 3 inhibition induced in vivo anti tumor effect on prostate cancer. Treatment was initialed when PC 3 xenografts were around 30mm3 in size for a 4 week period. As shown in Figure 1B,C, TDZD 8 significantly reduced xenograft wet weight and size compared to the solvent control. In addition, we also tested TDZD 8 induced tumor suppressio.