Targeting MELK by OTSSP167 effectively inhibits tumor growth and hampers
lung metastasis in esophageal squamous cell carcinoma
Abstract
Background and Purpose: Esophageal squamous cell carcinoma (ESCC) is the
sixth leading cause of cancer-related deaths worldwide and there is no
clinically effective targeted therapeutic drugs. OTSSP167, an orally
administrated inhibitor targeting maternal embryonic leucine zipper
kinase (MELK), is currently in several clinical trials in patients with
hematological or solid malignancies. The objective of the study is to
determine the antitumor activity of OTSSP167 against ESCC and elucidate
its underlying mechanism. Experimental Approach: Effects of OTSSP167 on
ESCC cell viability, colony formation, apoptosis, migration, invasion
and the related signaling molecules were determined. the anti-neoplastic
activity of OTSSP167 against tumor growth and metastasis was evaluated
in the ESCC xenograft model and lung metastasis mouse model,
respectively. Key Results: OTSSP167 effectively inhibited ESCC cell
proliferation and colony formation. In addition, OTSSP167 induced cell
apoptosis in a mitochondrial-dependent pathway via downregulation of
Survivin. OTSSP167 also exhibited strong synergism with 5-fluorouracil
and cisplatin in inducing cell growth inhibition and apoptosis.
Furthermore, OTSSP167 remarkably suppressed migration and invasion of
ESCC cells with MMP-2 decreased. Importantly, OTSSP167 potently hampered
the growth and lung metastasis of ESCC in nude mice. Mechanistically, we
demonstrated that MELK/FOXM1 signaling was fundamental for the
OTSSP167-mediated tumor growth inhibition as well as metastasis blockage
in ESCC. Conclusion and Implications: OTSSP167 exhibits a strong
anti-neoplastic activity against ESCC growth and metastasis through
targeting MELK/FOXM1 signaling. These data suggests that OTSSP167 is a
promising therapeutic agent and warrants clinical trials to further
investigate its efficacy in ESCC patients.