Background:

Homoharringtonine (Omacetaxine mepesuccinate;HHT) is a cytotoxic alkaloid with antitumor properties which acts by inhibiting translation elongation.

Homoharringtonine inhibits IL-6-induced STAT3 phosphorylation in a dose- and time-dependent manner. Homoharringtonine (HHT) inhibits cells growth, cell viability and colony formation, as well as induced cell apoptosis through mitochondria pathway. The cytotoxicity of Homoharringtonine on human NSCLC cell lines is investigated, A549 (wild type EGFR) and NCI-H1975 (H1975, mutant EGFR with L858R and T790M), Gefitinib is used as a control. By MTT assay, Homoharringtonine has moderate cytotoxicity to A549 with an IC50 of 3.7 μM and H1975 cells are more sensitive to Homoharringtonine with an IC50 of 0.7 μM. Homoharringtonine inhibits the cell proliferation and growth of A549 cells and H1975 cells in a time- and dose-dependent manner through MTT assay. By trypan blue exclusion assay, Homoharringtonine rapidly reduces viable A549 and H1975 cells in a dose- and time-dependent manner. Homoharringtonine significantly inhibits the clonogenic ability of A549 and H1975 cells[1].

Homoharringtonine (10 mg/kg) efficiently represses tumor growth compared to vehicle control or Gefitinib (P<0.05). Additionally, Homoharringtonine (HHT) treatment does not reduce the mice body weight, which suggests that Homoharringtonine has no apparent side effect. All the mice are euthanized, the tumors are isolated and imaged and the tumor sample cells are harvested to extract protein for determination if Homoharringtonine inhibits STAT3 phosphorylation via western blot. The level of STAT3 phosphorylation and MCL1 from Homoharringtonine treatment group is significantly decreased compared to vehicle control or Gefitinib treatment. Meanwhile, consistant with the results in the above, AKT1/2/3 and ERK1/2 phosphorylation is not inhibited with Homoharringtonine treatment. To further examine the STAT3 phosphorylation in the xenograft tumor samples with different treatments, the tumor samples are frozen and cutted into 10 μm sections for fluorescent immunohistochemistry. Homoharringtonine treatment inhibits STAT3 phosphorylation compared to vehicle control or Gefitinib treatment[1].

参考文献:
[1]. Cao W, et al. Homoharringtonine induces apoptosis and inhibits STAT3 via IL-6/JAK1/STAT3 signal pathway in Gefitinib-resistant lung cancer cells. Sci Rep. 2015 Jul 13;5:8477