Maternal embryonic leucine zipper kinase serves as a potential prognostic marker and leads to sorafenib chemoresistance modified by miR-142-5p in hepatocellular carcinoma

Background: Chemotherapy is an important treatment strategy for advanced hepatocellular carcinoma (HCC). Sorafenib is a first-line systemic drug that has been commonly used clinically for patients with advanced HCC. However, the high resistance rate of sorafenib in HCC patients often hinders its long-term efficacy. Therefore, it is vital to reveal the molecular mechanisms of sorafenib resistance in patients with HCC.

Methods: In current study, we screened out fourteen genes that over-expressed in HCC specimens through integrative bioinformatics analysis. Here, maternal embryonic leucine zipper kinase (MELK) was highlighted as one of the most probable molecules. The Database for Annotation Visualization and Integrated Discovery (DAVID) program was utilized for functional pathway enrichment analysis. Real-time PCR (RT-PCR) and western blot were used to examine the expression levels of MELK. CCK-8, transwell, colony formation assays and flow cytometry were used to detect cell proliferation, the cell cycle. The dual luciferase assays were performed to study the targeting relationship between MELK and miR-142-5p.

Results: MELK expressions were correlated significantly with cell proliferation by regulating cell cycle and DNA replication. High MELK expression in patients with HCC indicated a poor prognosis both the overall and diseases free survival rates. MELK knockdown suppresses cell proliferation, migration and invasion in vitro. miR-142-5p regulates MELK expression through binding to the complementary sequence in the 3'-UTR regions. MELK knockdown enhances sensitivity of sorafenib in HCC sorafenib-resistant (HCC/SR) cells.

Conclusions: MELK may serve as a potential prognostic marker in HCC and MELK knockdown enhanced sensitivity of HepG2/SR cells to sorafenib treatment. Our findings suggest that MELK/miR-142-5p axis could be a potentially therapeutic target for reversing the sorafenib resistance in HCC treatment.