BACKGROUND AND PURPOSE Targeting AR-DBD is a potential strategy toward the treatment of CRPC, however, rational design of a small molecules targeting AR-DBD is still underdevelopment. EXPERIMENTAL APPROACH MST, ITC and other different assays has been used to confirm the binding of SBF-1 to AR, also CHIP ha7s ha7s been used to confirm the blockade of AR binding to its target genes. The associated signaling pathway affected by SBF-1 has been identified by western blotting. Also, mutant AR-LBD and the the AR lacking DBD has led to the identification of the SBF-1 binding location in the AR. KEY RESULTS SBF-1 induced apoptosis and cell cycle arrest in both LNCaP and PC3/AR+ cell lines, also, inhibited the activation of the AR/IGF-1 and IGF1/AKT/FOXO1/PNCA pathways, which evidenced by decreased expression of p-AR, IGF-1, p-AKT, PCNA and Bcl-2. By using multiple methods, we found that SBF-1 could directly bind to AR and block the transcription of its target genes. Moreover, the interaction between SBF-1 and AR-DBD was confirmed, which overcame the re-activation of AR signaling by mutations in the AR-LBD. In the xenograft models of both ARWT and ARmutant prostate cancer, SBF-1 displayed a strong efficacy at very low doses including the inhibition of tumor growth, prolongation of survival time by inhibiting AR signaling. CONCLUSION AND IMPLICATIONS Our study here found a novel identified inhibitor of AR, SBF-1, for the first time, which is different from the current antiandrogens and may serve as a leading compound for the treatment of prostate cancer.

BACKGROUND AND PURPOSE Pharmacological inhibition of indoleamine-2,3-dioxygenase 1 activity is now considered to be a potential therapeutic tool for cancer therapy. However, the anti-cancer efficacy may be the biggest obstacle for the clinical application of current IDO1 inhibitors. EXPERIMENTAL APPROACHES HeLa cell-based IDO1/Kyn assay as well as recombinant IDO1 activity assay were used to determine the IDO1 enzyme activity. Interaction was examined by UV-visible spectra, isothermal titration calorimetry assay, cellular thermal shift assay and co-crystallization. Mouse colon cancer CT26 syngeneic model and azoxymethane/dextran sulfate sodium induced colon carcinogenesis model were employed to confirm the anti-tumor effect in vivo. KEY RESULTS B37 effectively and specifically inhibited IDO1 by targeting its heme-free conformation (apo-IDO1). By competing with heme for binding to apo-IDO1, B37 potently inhibited IDO1 activity with IC50 for 22 pM in the HeLa cell based assay. X-ray co-crystal structures of the inhibitor-enzyme complexes showed that unlike the hIDO1-BMS-986205 complex, the B37-hIDO1 complex displayed stronger hydrophobic interactions, which enhanced its binding affinity measured with ITC. Accordingly, stronger non-covalent interactions including π stacking and hydrogen bonds formed between B37 and apo-hIDO1 underlay the enthalpy-driven force for B37 to bind the enzyme. This binding model endowed B37 potent anti-tumor efficacy in mouse colon cancer CT26 syngeneic model and azoxymethane/dextran sulfate sodium induced colon carcinogenesis model by activating the host’s immune system. Moreover, the combination of B37 with a VEGFR2 inhibitor apatinib synergistically inhibited tumor growth. CONCLUSIONS AND IMPLICATIONS These results revealed that B37 may serve as a candidate for apo-IDO1 inhibition mediated immunotherapy.