Inhibition of MELK Protooncogene as an Innovative Treatment for Intrahepatic Cholangiocarcinoma

Abstract

Background and Objectives: Intrahepatic cholangiocarcinoma (iCCA) is a pernicious tumor characterized by a dismal outcome and scarce therapeutic options. To substantially improve the prognosis of iCCA patients, a better understanding of the molecular mechanisms responsible for development and progression of this disease is imperative. In the present study, we aimed at elucidating the role of the maternal embryonic leucine zipper kinase (MELK) protooncogene in iCCA. Materials and Methods: We analyzed the expression of MELK and two putative targets, Forkhead Box M1 (FOXM1) and Enhancer of Zeste Homolog 2 (EZH2), in a collection of human iCCA by real-time RT-PCR and immunohistochemistry (IHC). The effects on iCCA growth of both the multi-kinase inhibitor OTSSP167 and specific small-interfering RNA (siRNA) against MELK were investigated in iCCA cell lines. Results: Expression of MELK was significantly higher in tumors than in corresponding non-neoplastic liver counterparts, with highest levels of MELK being associated with patients’ shorter survival length. In vitro, OTSSP167 suppressed the growth of iCCA cell lines in a dose-dependent manner by reducing proliferation and inducing apoptosis. These effects were amplified when OTSSP167 administration was coupled to the DNA-damaging agent doxorubicin. Similar results, but less remarkable, were obtained when MELK was silenced by specific siRNA in the same cells. At the molecular level, siRNA against MELK triggered downregulation of MELK and its targets. Finally, we found that MELK is a downstream target of the E2F1 transcription factor. Conclusion: Our results indicate that MELK is ubiquitously overexpressed in iCCA, where it may represent a prognostic indicator and a therapeutic target. In particular, the combination of OTSSP167 (or other, more specific MELK inhibitors) with DNA-damaging agents might be a potentially effective therapy for human iCCA.

Lactic acidosis induces metabolic and phenotypic reprogramming in cholangiocarcinoma cells via the upregulation of thrombospondin‐1

“… 40 In another report, the transcription factor E2F1 was shown to promote the expression levels of THBS1 in HEK293 and U2OS cells. 41 As E2F1 is also functionally involved in CCA progression, 42 , 43 it may mediate LLA‐induced transcriptomic changes. Metabolic reprogramming by THBS1 may involve its binding to CD36, a widely expressed surface glycoprotein that acts as a fatty acid transporter in both lipogenic and respiratory pathways.…”

Wnt/β-catenin signaling as an emerging potential key pharmacological target in cholangiocarcinoma

“…External-beam radiation therapy (EBRT) has also emerged as a valuable alternative for patients with localized, unresectable intrahepatic CCA [16]. The different new molecular targets that have been exploited in the preclinical and clinical trials for the management of CCA include fibroblast growth factor receptors [17], heat-shock protein 90 [18], tyrosine-kinase [19], ROS1 kinase fusion proteins [20], Akt/Erk signaling [21], SOX17, a transcription factor [22], Maternal Embryonic Leucine Zipper Kinase (MELK), a protooncogene [23] and mesothelin [24] etc. However, the development of drugs based on these molecular targets is still in the different stages of preclinical or clinical trials.…”

Cloning, tissue distribution, expression pattern, and function of porcine maternal embryonic leucine zipper kinase

“…Maternal embryonic leucine zipper kinase (MELK) is a member of the Snf1/AMPK family of kinases (1)(2)(3), which participates in a wide range of cellular processes related to the cell cycle (4,5), apoptosis, spliceosome assembly (6), and cell proliferation (7). MELK is highly expressed in human cancers and is associated with more aggressive forms of astrocytoma, glioblastoma, breast cancer, and melanoma (8,9), suggesting that MELK is a potential anticancer target in diverse tumor entities (10).…”