High expression of maternal embryonic leucine-zipper kinase (MELK) impacts clinical outcomes in patients with ovarian cancer and its inhibition suppresses ovarian cancer cells growth ex vivo

Evaluating the specific STAT3 inhibitor YHO-1701 in ovarian cancer cell lines and patient-derived cell models: efficacy, mechanisms, and therapeutic potential

OBJECTIVE

Signal transducer and activator of transcription 3 (STAT3) plays key roles in regulating cancer cell proliferation, survival, and metastasis. We aimed to determine the effects of YHO-1701, an oral STAT3 inhibitor, in ovarian cancer (OC).

METHODS

We evaluated the impact of YHO-1701 on cell growth in patient-derived cells (PDCs) and OC cell lines using standard cell proliferation assays. Spheroid models derived from PDCs were assessed using three-dimensional (3D) cell viability assays. Antitumor activity was performed in SKOV3 xenograft mice treated orally administrated YHO-1701 with 20 mg/kg. Changes in STAT3 signaling were analyzed by western blotting. The molecular mechanisms of STAT3 inhibition were investigated by sequencing RNA and analyzing pathways in the SKOV3 using a small interfering RNA targeting STAT3 (STAT3 siRNA) and YHO-1701.

RESULTS

YHO-1701 inhibited the growth of OC cell lines by preventing STAT3 dimerization and decreasing the expression of its downstream signaling molecule, survivin. The growth of PDCs and spheroids obtained from patients with primary and recurrent OCs was significantly inhibited. Antitumor effect was observed in the SKOV3 xenograft mice with YHO-1701. YHO-1701 induced apoptosis in OC cells. Additionally, p53 and/or MAPK signaling pathways were upregulated in SKOV3 cells incubated with YHO-1701 and in those with STAT3 siRNA.

CONCLUSION

Our results showed that YHO-1701 suppressed cell growth in PDCs of OC, accompanied by survivin inhibition, and a decrease in the number of peritoneal metastasis in the mice by YHO-1701, compared with those treated with control. Therefore, YHO-1701 could be a promising candidate agent for treating OC.

Exploration of MELK as a downstream of Del-1 and druggable targets in triple-negative breast cancer

PURPOSE

In our previous study, Developmental endothelial locus-1 (Del-1) was a promising predictive marker for breast cancer. However, the downstream targets of Del-1 remain unknown. Here, we sought to discover a druggable target downstream of Del-1 and investigate the mechanism by which it regulates the course of breast cancer.

METHODS

To investigate Del-1 downregulation effect on breast cancer, we performed transcriptome analysis using RNA sequencing of Del-1 knockdowned MDA-MB-231 cell line Plus, to investigate the expression of Del-1 and Maternal embryonic leucine zipper kinase (MELK), mRNA levels in eight different triple-Negative Breast Cancer (TNBC) cell lines were analyzed. High-throughput sequencing was performed on total RNA isolated. OTS167 was used for MELK inhibition. The effects of MELK on cell proliferation and invasion were determined using the MTT and Matrigel transwell assays. Furthermore, we examined MELK expression in breast cancer tissue.

RESULTS

Del-1 and MELK mRNA expression levels were significantly higher in the TNBC cell lines, MDA-MB-468, HCC-1806, and MBA-MB-231. Knocking down Del-1 with siRNA in HCC-1806 and MBA-MB-231 cells significantly decreased MELK expression and thus suggested a possible relationship between Del-1 and MELK. In MDA-MB-468 cells, a basal-like 1 TNBC cell line, OTS167 significantly inhibited breast cancer cell proliferation and promoted cell apoptosis. To further investigate the relationship between Del-1 and MELK, dual inhibition of both Del-1 and MELK was performed, which significantly reduced the viability of MDA-MB-468 and MBA-MB-231 cells.

CONCLUSION

We found that MELK acts downstream of Del-1 and is a promising druggable target, especially in basal-like and mesenchymal stem-like subtype.

A genome-wide association study of germline variation and melanoma prognosis

Background

The high mortality of cutaneous melanoma (CM) is partly due to unpredictable patterns of disease progression in patients with early-stage lesions. The reliable prediction of advanced disease risk from early-stage CM, is an urgent clinical need, especially given the recent expansion of immune checkpoint inhibitor therapy to the adjuvant setting. In our study, we comprehensively investigated the role of germline variants as CM prognostic markers.

Methods

We performed a genome-wide association analysis in two independent cohorts of N=551 (discovery), and N=550 (validation) early-stage immunotherapy-naïve melanoma patients. A multivariable Cox proportional hazard regression model was used to identify associations with overall survival in the discovery group, followed by a validation analysis. Transcriptomic profiling and survival analysis were used to elucidate the biological relevance of candidate genes associated with CM progression.

Results

We found two independent associations of germline variants with melanoma prognosis. The alternate alleles of these two SNPs were both associated with an increased risk of death [rs60970102 in MELK: HR=3.14 (2.05-4.81), p=1.48×10^-7; and rs77480547 in SH3BP4: HR=3.02 (2.02-4.52), p=7.58×10^-8, both in the pooled cohort]. The addition of the combined risk alleles (CRA) of the identified variants into the prognostic model improved the predictive power, as opposed to a model of clinical covariates alone.

Conclusions

Our study provides suggestive evidence of novel melanoma germline prognostic markers, implicating two candidate genes: an oncogene MELK and a tumor suppressor SH3BP4, both previously suggested to affect CM progression. Pending further validation, these findings suggest that the genetic factors may improve the prognostic stratification of high-risk early-stage CM patients, and propose putative biological insights for potential therapeutic investigation of these targets to prevent aggressive outcome from early-stage melanoma.

AMPK-like proteins and their function in female reproduction and gynecologic cancer

Serine-threonine kinase (STK11), also known as liver kinase B1 (LKB1), is a regulator of cellular homeostasis through regulating the cellular ATP-to-ADP ratio. LKB1 is classified as a tumor suppressor and functions as the key activator of AMP-activated protein kinase (AMPK) and a family of serine-threonine kinases called AMPK-like proteins. These proteins include novel (nua) kinase family 1 (NUAK1 and 2), salt inducible kinase (SIK1), QIK (known as SIK2), QSK (known as SIK3 kinase), and maternal embryonic leuzine zipper kinase (MELK) on tightly controlled and specific residual sites. LKB1 also regulates brain selective kinases 1 and 2 (BRSK1 and 2), additional members of AMPK-like protein family, which functions are probably less studied. AMPK-like proteins play a role in variety of reproductive physiology functions such as follicular maturation, menopause, embryogenesis, oocyte maturation, and preimplantation development. In addition, dysfunctional activity of AMPK-like proteins contributes to apoptosis blockade in cancer cells and induction of the epithelial-mesenchymal transition required for metastasis. Dysregulation of these proteins occurs in ovarian, endometrial, and cervical cancers. AMPK-like proteins are still undergoing further classification and may represent novel targets for targeted gynecologic cancer therapies. In this chapter, we describe the AMPK-like family of proteins and their roles in reproductive physiology and gynecologic cancers.

MELK predicts poor prognosis and promotes metastasis in esophageal squamous cell carcinoma via activating the NF‑κB pathway

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignancies worldwide with a low 5-year survival rate due to the lack of effective therapeutic strategies. Accumulating evidence has indicated that maternal embryonic leucine zipper kinase (MELK) is highly expressed in several tumors and associated with tumor development. However, the biological effects of MELK in ESCC remain unknown. In the present study, cell phenotypical experiments and animal metastasis assays were performed to detect the influence of MELK knockdown in vitro and in vivo. The potential molecular mechanism of MELK-mediated ESCC metastasis was further investigated by western blotting and immunofluorescence staining. The results revealed that the expression of MELK in human ESCC tissues was higher than that in adjacent normal tissues and was positively associated with the poor prognosis of patients. Reducing MELK expression resulted in growth inhibition and suppression of the invasive ability of ESCC cells in vitro and in vivo. MELK inhibition induced alterations of epithelial-mesenchymal transition-associated proteins. Mechanistically, MELK interacted with IκB kinase (IKK) and promoted the phosphorylation of IKK, by which MELK regulated activation of the NF-κB pathway. Collectively, the present study revealed the function and mechanism of MELK in the cell metastasis of ESCC, which may be a potential therapeutic target for ESCC.

Comprehensive analysis to identify noncoding RNAs mediated upregulation of maternal embryonic leucine zipper kinase (MELK) correlated with poor prognosis in hepatocellular

Object: Maternal embryonic leucine zipper kinase (MELK) is involved in the development and progression of various cancers. This work investigated the usefulness of MELK in the prediction of hepatocellular carcinoma (HCC) prognosis.

Methods: Information on MELK expression was obtained by pan-cancer analysis using The Cancer Genome Atlas (TCGA) database. The TCGA-liver hepatic cancer (TCGA-LIHC), Oncomine datasets, International Cancer Genome Consortium (ICGC) datasets were used to investigate MELK expression in HCC. The prognostic roles of MELK in HCC were assessed by univariate and multivariate survival analyses. The underlying mechanism for noncoding RNAs (ncRNAs) involved in MELK expression was investigated by in silico studies, correlation, methylation, and survival analyses. The relationships between MELK expression and immune cells, immune markers, and checkpoint markers were also analyzed.

Results: (1) MELK was identified as an independent predictor of overall survival (OS) in HCC patients (MELK high vs. low expression, HR 2.469; 95% CI 1.217–5.008; p = 0.012) in a multivariate Cox analysis, with a concordance index (C-index) value of 0.727 (95% CI 0.750–0.704). (2) The noncoding RNA miR3142HG and the LINC00265/has-miR-101-3p axis were found to regulate MELK expression in HCC tissue. (3) MELK levels were linked to various immune functions, including tumor infiltration and the expression of immune checkpoints and biomarkers in HCC.

Conclusion: MELK may have an oncogenic function in HCC and was found to be up-regulated by ncRNAs and associated with immune cell infiltration and unfavorable prognosis.

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.

Clinical significance of metabolism-related genes and FAK activity in ovarian high-grade serous carcinoma

BACKGROUND

Administration of poly (ADP-ribose) polymerase (PARP) inhibitors after achieving a response to platinum-containing drugs significantly prolonged relapse-free survival compared to placebo administration. PARP inhibitors have been used in clinical practice. However, patients with platinum-resistant relapsed ovarian cancer still have a poor prognosis and there is an unmet need. The purpose of this study was to examine the clinical significance of metabolic genes and focal adhesion kinase (FAK) activity in advanced ovarian high-grade serous carcinoma (HGSC).

METHODS

The RNA sequencing (RNA-seq) data and clinical data of HGSC patients were obtained from the Genomic Data Commons (GDC) Data Portal and analysed ( https://portal.gdc.cancer.gov/ ). In addition, tumour tissue was sampled by laparotomy or screening laparoscopy prior to treatment initiation from patients diagnosed with stage IIIC ovarian cancer (International Federation of Gynecology and Obstetrics (FIGO) classification, 2014) at the Saitama Medical University International Medical Center, and among the patients diagnosed with HGSC, 16 cases of available cryopreserved specimens were included in this study. The present study was reviewed and approved by the Institutional Review Board of Saitama Medical University International Medical Center (Saitama, Japan). Among the 6307 variable genes detected in both The Cancer Genome Atlas-Ovarian (TCGA-OV) data and clinical specimen data, 35 genes related to metabolism and FAK activity were applied. RNA-seq data were analysed using the Subio Platform (Subio Inc, Japan). JMP 15 (SAS, USA) was used for statistical analysis and various types of machine learning. The Kaplan-Meier method was used for survival analysis, and the Wilcoxon test was used to analyse significant differences. P < 0.05 was considered significant.

RESULTS

In the TCGA-OV data, patients with stage IIIC with a residual tumour diameter of 1-10 mm were selected for K means clustering and classified into groups with significant prognostic correlations (p = 0.0444). These groups were significantly associated with platinum sensitivity/resistance in clinical cases (χ2 test, p = 0.0408) and showed significant relationships with progression-free survival (p = 0.0307).

CONCLUSION

In the TCGA-OV data, 2 groups classified by clustering focusing on metabolism-related genes and FAK activity were shown to be associated with platinum resistance and a poor prognosis.