Casticin inhibits the hedgehog signaling and leads to apoptosis in AML stem-like KG1a and mature KG1 cells

Objectives: Acute myeloid leukemia (AML) is a severe blood cancer with less than 50% long-term survival. Despite advancements in treatment options, relapse is still the major obstacle. The main reason of this problem is ineffective targeting of leukemic stem cells (LSCs), which play an important role in tumor development and relapse. In our previous studies, we found that casticin, the major polyphenolic component of Vitex trifolia's fruit, targets both leukemic cells and LSCs without affecting healthy tissues. Therefore, in this study, we aimed to investigate the effect of casticin-mediated cell death in relation to the LSCs-favored survival pathways at gene and protein expression levels using in vitro LSC-like and parental leukemic cell models. Methods: We validated the LSC character of KG1a and KG1 cells (84.55% CD34+, CD38- and 93.55% CD34+, CD38+, respectively) by flow cytometry. For the investigation of casticin's mechanism of action, we employed real time-PCR, western blotting and bioinformatics analyses. Results: Our results showed an increase in cleaved PARP/β-actin ratio but no change in LC3BI/II and SQSTM/β-actin ratios. Our gene expression, bioinformatics and immunoblotting analyses represented significant decrease in Shh, Gli and Wnt levels. We also elucidated a possible crosstalk between Hedgehog and other oncogenic cascades via the Gli, Notch, YAP, p38, Mcl-1, and Myc proteins in casticin mediated anti-leukemic effect. Conclusions: In conclusion, we found that casticin induces apoptosis in both LSC-like and parental leukemia cells mainly by suppressing Shh signaling, which is crucial for LSC survival and AML relapse. © 2024 the author(s), published by De Gruyter, Berlin/Boston.