thiostrepton (RSO-021)

Functional experiments revealed that the cancer-inhibitory effect of thiostrepton is reduced in the absence of DAB2IP, suggesting that upregulation of this protein contributes to its action. These findings encourage further development of thiostrepton for the treatment of solid cancers and unveil a novel molecular target underlying its anti-tumoral activity.

These effects are conserved in human T cells, as thiostrepton also inhibits the differentiation of human Tregs. Our findings highlight thiostrepton as a promising Treg-targeting immunomodulatory compound with the potential to enhance antitumor immune responses.

Furthermore, we have unlinked the high ROS (reactive oxygen species) induction reported in earlier in vitro studies from apoptosis induction upon thiostrepton treatment in C. elegans. Overall, our genetic data indicate that apoptosis induction mediated by thiostrepton occurs at the level of the core apoptotic machinery.

These findings suggest that FOXM1 inhibition could be particularly effective in patients with high KPNA2 expression, offering a novel therapeutic strategy for this specific molecular subtype. Several FOXM1 inhibitors, including thiostrepton and FDI-6, warrant investigation as potential targeted treatments for KPNA2-high HR+HER2- breast cancer patients.

Overall, our results indicate that FOXM1 can serve as a novel target for ICC immunotherapy. By targeting FOXM1, TST exerts "dual anti-tumor" effects and has the potential to become a promising immunotherapy agent for ICC patients.

Thiostrepton-related changes in cell survival and cell migration, as well as mechanistical processes, were almost completely reversed by treatment with the antioxidant N-acetylcysteine (NAC), suggesting that the mechanism is dependent on reactive oxygen species (ROS). These results demonstrated that thiostrepton induced apoptosis and inhibited migration through ROS-induced ER stress and proteotoxic stress in colorectal cancer.

Inhibiting FOXM1 pharmacologically with thiostrepton produced tumor-suppressive effects and improved immunotherapy responses in a Lewis lung carcinoma mouse model. The senescence-related signature demonstrates potential in predicting patient prognosis and immunotherapy efficacy in LUAD.

These results suggest that, in addition to inhibiting FoxM1, TST may induce proteotoxicity and autophagy to disrupt cellular tubulin polymerization, and this mechanism might account for its antimitotic effects, enhancement of Taxol anticancer effects, and ability to overcome Taxol resistance in MDA-MB-231 cells. These data further imply that TST may be useful to improve the therapeutic efficacy of Taxol.

Thus, TS is a promising therapeutic agent for Cushing disease. Our list of hit compounds and new mechanistic insights into TS effects serve as a valuable foundation for future research.

Analysis of ferroptosis-related genes confirms dysregulation following TST treatment in HaCaT cells. Furthermore, TST treatment exhibits effects on mitochondrial morphology and function, affirming its induction of apoptosis in the cells through heightened oxidative stress due to mitochondrial damage and dysregulation of mitochondrial membrane potential.

In addition, to investigate potential correlations between FOXM1 down-regulation and oncologic characteristics, we treated ES cell lines with thiostrepton, a naturally occurring antibiotic that inhibits both small interfering RNA (siRNA) and FOXM1...Finally, cDNA microarray analysis data showed that FOXM1 regulated cIAP2, which is one of the apoptosis inhibitors activated by the TNFα-mediated NF-κB pathway. In conclusion, the FOXM1 gene may be a promising therapeutic target for ES.

Moreover, c-FLIP overexpression significantly increased the expression and phosphorylation of SMAD2/3 proteins and vice versa. In conclusion, our study reveals c-FLIP/SMAD2/3 signaling pathway as a novel mechanism of antitumor activity of thiostrepton.