Oridonin (1) has attracted considerable attention in recent years due to its unique and safe anticancer pharmacological profile. Nevertheless, it exhibits moderate to poor effects against highly aggressive cancers including triple-negative and drug-resistant breast cancer cells. Herein, we report the rational design and synthesis of novel dienone derivatives with an additional α,β-unsaturated ketone system diversely installed in the A-ring based on this class of natural scaffold that features dense functionalities and stereochemistry-rich frameworks. Efficient and regioselective enone construction strategies have been established. Meanwhile, a unique 3,7-rearrangement reaction was identified to furnish an unprecedented dienone scaffold. Intriguingly, these new analogues have been demonstrated to significantly induce apoptosis and inhibit colony formation with superior antitumor effects against aggressive and drug-resistant breast cancer cells in vitro and in vivo, while also exhibiting comparable or lower toxicity to normal human mammary epithelial cells in comparison with 1.

Many tumors maintain chromosome-ends through a telomerase-independent, DNA-templated mechanism called alternative lengthening of telomeres (ALT). While ALT occurs in only a subset of tumors, it is strongly associated with mutations in the genes ATRX and DAXX, which encode components of an H3.3 histone chaperone complex. The role of ATRX and DAXX mutations in potentiating the mechanism of ALT remains incompletely understood. Here we characterize an osteosarcoma cell line, G292, with wild-type ATRX but a unique chromosome translocation resulting in loss of DAXX function. While ATRX and DAXX form a complex in G292, this complex fails to localize to nuclear PML bodies. We demonstrate that introduction of wild type DAXX suppresses the ALT phenotype and restores the localization of ATRX/DAXX to PML bodies. Using an inducible system, we show that ALT-associated PML bodies are disrupted rapidly following DAXX induction and that ALT is again restored following withdrawal of DAXX.