Marine derived macrolide bryostatin 4 inhibits the TGF-β signaling pathway against acute erythroleukemia

Acute erythroleukemia (AEL) is a rare and highly aggressive subtype of acute myeloid leukemia (AML) with an extremely poor prognosis when treated with available drugs. Therefore, new investigational agents capable of inducing remission are urgently required.

Bioinformatics analysis, western blot and qRT-PCR were used to reveal the potential biological mechanism of bryostatin 4 (B4), an antineoplastic macrolide derived from the marine bryozoan Bugula neritina. Then, in vivo experiments were conducted to evaluate the role of transforming growth factor (TGF)-β signaling in the progression of AEL.

Our results revealed that the proliferation of K562 cells and TF-1 cells was significantly inhibited by B4 at IC₅₀ values of 37 nM and 52 nM, respectively. B4 inhibited TGF-β signaling and its downstream pathway targets, particularly the phosphorylation of Smad2, Smad3, Ras, C-RAF, ERK1/2, and MEK. B4 also played an important role in cell invasion and migration in K562 cells and TF-1 cells by reducing the protein levels of the mesenchymal cell marker vimentin. Moreover, Flow cytometry and western blot analyses demonstrated that B4 induced apoptosis and initiated G0/G1 phase arrest by modulating mitochondrial dysfunction and cyclin-dependent kinase (CDK) expression.

These findings indicated that B4 could inhibit the proliferation, migration, invasion, and TGF-β signaling pathways of AEL cells, thus suggesting that B4 possesses therapeutic potential as a treatment for AEL.