As of 2008, prostate cancer remains the number one cause of estimated new cancer cases in American men. Although early prostate cancer responds to androgen ablation, most tumors eventually recur as hormone-refractory prostate cancer (HRPC). Recent advances have identified many abnormal signaling pathways that contribute to the development of HRPC, mainly including dysregulation of androgen receptor (AR) function and the over-expression of the anti-apoptotic proteins, Bcl-2/Bcl-xL.
It was found that thiazolidinediones (TZD), which include the anti-diabetic agents troglitazone, rosiglitazone, pioglitazone and ciglitazone, possess anti-tumor activity. It has been revealed that the anti-tumor activity of the TZDs could be attributed to PPARγ-independent mechanisms including Bcl-2/Bcl-xL inhibition and AR transcriptional repression. The objective of this dissertation is to further modify the TZD structures to enhance anti-prostate cancer activity by targeting the dysregulated Bcl-2/Bcl-xL and AR signaling pathways.
Directed by method of molecular modeling, over 50 troglitazone derivatives have been designed and synthesized in two stages, yielding the optimal compound HepCNCF3, which showed two orders of magnitude improvement in Bcl-xL/Bcl-2 inhibition compared to troglitazone. Results from molecular modeling, Western blotting assay and co-immunoprecipitation assay confirmed the inhibitory effects of HepCNCF3 on Bcl-2/Bcl-xL and its function of apoptosis induction at low micromolar level in prostate cancer cells.
The effects of ciglitazone on transcriptional repression of AR have been verified, and as a lead compound, ciglitazone possessed advantages of simpler molecular and stronger potency compared to troglitazone. Partly aided by method of focused-library solid-phase combinatorial chemistry, three stages of optimization have been performed based on ciglitazone. Out of totally approximately 150 new derivatives, the optimal compounds such as CG12, CC5 and CC22 showed one order of magnitude improvement in AR repression and cytotoxicity in LNCaP cells than ciglitazone. The optimized activites of these compounds have been confirmed in AR reporter gene luciferase assay, Western blotting assay and flow-cytometry analysis.
Overall, through comprehensive methods of computer-based design, ligand-based design and solid-phase combinatorial chemistry, several promising agents targeting on the abnormalities in prostate cancer, particularly in HRPC, have been successfully developed and their effects of Bcl-2/Bcl-xL inhibition or AR ablation have been validated.