Subtype-specific expression of MELK is partly due to copy number alterations in breast cancer

Maternal embryonic leucine-zipper kinase (MELK) regulates cell cycle progression and is highly expressed in many cancers. The molecular mechanism of MELK dysregulation has not been determined in aggressive forms of breast cancer, such as triple negative breast cancer (TNBC). To evaluate molecular markers of MELK aberrations in aggressive breast cancer, we assessed MELK gene amplification and expression in breast tumors. MELK mRNA expression is highly up-regulated in basal-like breast cancer (BLBC), the major molecular subtype of TNBC, compared to luminal or other subtypes of breast tumors. MELK copy number (CN) gains are significantly associated with BLBC, whereas no significant association of CpG site methylation or histone modifications with breast cancer subtypes was observed. Accordingly, the CN gains appear to contribute to an increase in MELK expression, with a significant correlation between mRNA expression and CN in breast tumors and cell lines. Furthermore, immunohistochemistry (IHC) assays revealed that both nuclear and cytoplasmic staining scores of MELK were significantly higher in invasive ductal carcinoma (IDC) tumors compared to ductal carcinoma in situ (DCIS) and normal breast tissues. Our data showed that upregulation of MELK in BLBC may be in part driven by CN gains, rather than epigenetic modifications, indicating a potential for overexpression and CN gains of MELK to be developed as a diagnostic and prognostic marker to identify patients who have more aggressive breast cancer.

The driving role of the Cdk5/Tln1/FAKS732 axis in cancer cell extravasation dissected by human vascularized microfluidic models

BACKGROUND

Understanding the molecular mechanisms of metastatic dissemination, the leading cause of death in cancer patients, is required to develop novel, effective therapies. Extravasation, an essential rate-limiting process in the metastatic cascade, includes three tightly coordinated steps: cancer cell adhesion to the endothelium, trans-endothelial migration, and early invasion into the secondary site. Focal adhesion proteins, including Tln1 and FAK, regulate the cytoskeleton dynamics: dysregulation of these proteins is often associated with metastatic progression and poor prognosis.

METHODS

Here, we studied the previously unexplored role of these targets in each extravasation step using engineered 3D in vitro models, which recapitulate the physiological vascular niche experienced by cancer cells during hematogenous metastasis.

RESULTS

Human breast cancer and fibrosarcoma cell lines respond to Cdk5/Tln1/FAK axis perturbation, impairing their metastatic potential. Vascular breaching requires actin polymerization-dependent invadopodia formation. Invadopodia generation requires the structural function of FAK and Tln1 rather than their activation through phosphorylation. Our data support that the inhibition of FAKS732 phosphorylation delocalizes ERK from the nucleus, decreasing ERK phosphorylated form. These findings indicate the critical role of these proteins in driving trans-endothelial migration. In fact, both knock-down experiments and chemical inhibition of FAK dramatically reduces lung colonization in vivo and TEM in microfluidic setting. Altogether, these data indicate that engineered 3D in vitro models coupled to in vivo models, genetic, biochemical, and imaging tools represent a powerful weapon to increase our understanding of metastatic progression.

CONCLUSIONS

These findings point to the need for further analyses of previously overlooked phosphorylation sites of FAK, such as the serine 732, and foster the development of new effective antimetastatic treatments targeting late events of the metastatic cascade.

Analysis of Copy-Number Variations and Feline Mammary Carcinoma Survival

Feline mammary carcinomas (FMCs) are highly malignant. As the disease-free survival (DFS) and overall survival (OS) are short, prognostication is crucial. Copy-number variations (CNVs) analysis by next-generation sequencing serves to identify critical cancer-related genomic regions. Thirty-three female cats with FMCs were followed during two years after surgery. Tumours represented tubulopapillary and solid carcinomas encompassing six molecular subtypes. Regardless of the histopathological diagnosis, molecular subtypes showed important differences in survival. Luminal A tumours exhibited the highest DFS (p = 0.002) and cancer-specific OS (p = 0.001), and the lowest amount of CNVs (p = 0.0001). In contrast, basal-like triple-negative FMCs had the worst outcome (DFS, p < 0.0001; and OS, p < 0.00001) and were the most aberrant (p = 0.05). In the multivariate analysis, copy-number losses (CNLs) in chromosome B1 (1-23 Mb) harbouring several tumour-repressors (e.g. CSMD1, MTUS1, MSR1, DBC2, and TUSC3) negatively influenced DFS. Whereas, copy-number gains (CNGs) in B4 (1-29 Mb) and F2 (64-82.3 Mb) comprising epithelial to mesenchymal transition genes and metastasis-promoting transcription factors (e.g. GATA3, VIM, ZEB1, and MYC) negatively influenced DFS and cancer-specific OS. These data evidence an association between specific CNVs in chromosomes B1, B4 and F2, and poor prognosis in FMCs.

MELK promotes Endometrial carcinoma progression via activating mTOR signaling pathway

Background

Endometrial carcinoma (EC) is one of the most common gynecological malignancies among women. Maternal embryonic leucine Zipper Kinase (MELK) is upregulated in a variety of human tumors, where it contributes to malignant phenotype and correlates with a poor prognosis. However, the biological function of MELK in EC progression remains largely unknown.

Methods

We explored the MELK expression in EC using TCGA and GEO databases and verified it using clinical samples by IHC methods. CCK-8 assay, colony formation assay, cell cycle assay, wound healing assay and subcutaneous xenograft mouse model were generated to estimate the functions of MELK and its inhibitor OTSSP167. qRT-PCR, western blotting, co-immunoprecipitation, chromatin immunoprecipitation and luciferase reporter assay were performed to uncover the underlying mechanism concerning MELK during the progression of EC.

Findings

MELK was significantly elevated in patients with EC, and high expression of MELK was associated with serous EC, high histological grade, advanced clinical stage and reduced overall survival and disease-free survival. MELK knockdown decreased the ability of cell proliferation and migration in vitro and subcutaneous tumorigenesis in vivo. In addition, high expression of MELK could be regulated by transcription factor E2F1. Moreover, we found that MELK had a direct interaction with MLST8 and then activated mTORC1 and mTORC2 signaling pathway for EC progression. Furthermore, OTSSP167, an effective inhibitor, could inhibit cell proliferation driven by MELK in vivo and vitro assays.

Interpretation

We have explored the crucial role of the E2F1/MELK/mTORC1/2 axis in the progression of EC, which could be served as potential therapeutic targets for treatment of EC.

Funding

This research was supported by National Natural Science Foundation of China (No:81672565), the Natural Science Foundation of Shanghai (Grant NO:17ZR1421400 to Dr. Zhihong Ai) and the fundamental research funds for central universities (No: 22120180595).

Long noncoding RNA LINC02418 regulates MELK expression by acting as a ceRNA and may serve as a diagnostic marker for colorectal cancer

Some types of long noncoding RNAs (lncRNAs) are aberrantly expressed in human diseases, including cancer. However, the overall biological roles and clinical significances of most lncRNAs in colorectal cancer (CRC) are not fully understood. First, The Cancer Genome Atlas (TCGA) was analyzed to identify differentially expressed lncRNAs between CRC tissues and noncancerous tissues. We identified that LINC02418 was highly expressed in CRC tissues and cell lines. Next, we evaluated the effect of LINC02418 on CRC tumorigenesis and its regulatory functions of absorbing microRNA and indirectly stimulating protein expression by acting as a ceRNA. Mechanistically, LINC02418 acted as a ceRNA to upregulate MELK expression by absorbing miR-1273g-3p. In addition, the diagnostic performance of cell-free LINC02418 and exosomal LINC02418 were both evaluated by the receiver operating characteristic curve and the area under the curve (AUC). Exosomal LINC02418 could distinguish the patients with CRC from the healthy controls (AUC = 0.8978, 95% confidence interval = 0.8644–0.9351) better than cell-free LINC02418 (AUC = 0.6784, 95% confidence interval = 0.6116–0.7452). Collectively, we determined that LINC02418 was significantly overexpressed in CRC and that the LINC02418–miR-1273g-3p–MELK axis played a critical role in CRC tumorigenesis. Finally, exosomal LINC02418 is a promising, novel biomarker that can be used for the clinical diagnosis of CRC.

Development and Validation of Tumor-educated Blood Platelets Integrin Alpha 2b (ITGA2B) RNA for Diagnosis and Prognosis of Non-small-cell Lung Cancer through RNA-seq

Background: Currently, there are no molecular biomarkers for the early detection of non-small-cell lung cancer (NSCLC). This study focused on identifying RNAs found on tumor-educated blood platelets (TEPs) for detecting stage I NSCLC. Methods: Platelet RNAs, isolated from the blood of 9 patients with NSCLC (stages I and II) and 8 healthy controls, were analyzed using RNA-seq. ITGA2B was selected as a candidate marker. Two different Polymerase Chain Reactions (PCR) were used to measure ITGA2B in platelet samples from healthy controls (n = 150), patients with NSCLC (n = 243), and patients with benign pulmonary nodules (n = 141) in two cohorts. Results: Platelet ITGA2B levels were significantly higher (p < 0.001) in patients with NSCLC than in all controls. The diagnostic accuracy of ITGA2B was area under the curve (AUC) of 0.922 [95% confidence interval (CI), 0.892-0.952], sensitivity of 92.8%, and specificity of 78.6% in the test cohort and 0.888, 91.2%, and 56.5% in the validation cohort for NSCLC by quantitative real time PCR (q-PCR). Furthermore, ITGA2B maintained diagnostic accuracy for patients with NSCLC using Droplet Digital PCR (ddPCR) and the other type of internal control, Ribosomal Protein L32 (RPL32) [ddPCR: 0.967 (0.929-1.000) and RPL32: 0.847(0.773-0.920)]. A nomogram incorporating ITGA2B, carcinoembryonic antigen (CEA) and stage could predict the overall survival (C-index = 0.756). Conclusions: TEP ITGA2B is a promising marker to improve identification of patients with stage I NSCLC and differentiate malignant from benign lung nodules.

MELK: a potential novel therapeutic target for TNBC and other aggressive malignancies

INTRODUCTION

There is an unmet need in triple-negative breast cancer (TNBC) patients for targeted therapies. Maternal embryonic leucine zipper kinase (MELK) is a promising target for inhibition based on the abundance of correlative and functional data supporting its role in various cancer types. Areas covered: This review endeavors to outline the role of MELK in cancer. Studies covering a range of biological functions including proliferation, apoptosis, cancer stem cell phenotypes, epithelial-to-mesenchymal transition, metastasis, and therapy resistance are discussed here in order to understand the potential of MELK as a clinically significant target for TNBC patients. Expert opinion: Targeting MELK may offer a novel therapeutic opportunity in TNBC and other cancers. Despite the abundance of correlative data, there is still much we do not know. There are a lack of potent, specific inhibitors against MELK, as well as an insufficient understanding of MELK's downstream substrates. Addressing these issues is the first step toward identifying a patient population that could benefit from MELK inhibition in combination with other therapies.

Preclinical evaluation of biomarkers associated with antitumor activity of MELK inhibitor

MELK is upregulated in various types of human cancer and is known to be associated with cancer progression, maintenance of stemness, and poor prognosis. OTS167, a MELK kinase inhibitor, shows potent growth-suppressive effect on human tumors in a xenograft model, but the detailed mode of action has not been fully elucidated. In this study, we demonstrate the molecular mechanism of action of MELK inhibitor OTS167 in a preclinical model. OTS167-treated cells caused morphological transformation, induced the differentiation markers, and reduced stem-cell marker expression. Furthermore, we identified DEPDC1, known as an oncogene, as an additional downstream molecule of the MELK signaling pathway. MELK enhanced DEPDC1 phosphorylation and its stability. The expression of MELK and downstream molecules was decreased in OTS167-treated xenograft tumor tissues, which revealed central necrosis and significant growth suppression. Our data should further shed light on the mechanism of action how OTS167 suppresses tumor growth through the inhibition of the MELK signaling pathway and suggest the possibility of biomarkers for the assessment of clinical efficacy.

Identification of IL11RA and MELK amplification in gastric cancer by comprehensive genomic profiling of gastric cancer cell lines

AIM

To identify common copy number alterations on gastric cancer cell lines.

METHODS

Four gastric cancer cell lines (ACP02, ACP03, AGP01 and PG100) underwent chromosomal comparative genome hybridization and array comparative genome hybridization. We also confirmed the results by fluorescence in situ hybridization analysis using the bacterial artificial chromosome clone and quantitative real time PCR analysis.

RESULTS

The amplification of 9p13.3 was detected in all cell lines by both methodologies. An increase in the copy number of 9p13.3 was also confirmed by fluorescence in situ hybridization analysis. Moreover, the interleukin 11 receptor alpha (IL11RA) and maternal embryonic leucine zipper kinase (MELK) genes, which are present in the 9p13.3 amplicon, revealed gains of the MELK gene in all the cell lines studied. Additionally, a gain in the copy number of IL11RA and MELK was observed in 19.1% (13/68) and 55.9% (38/68) of primary gastric adenocarcinoma samples, respectively.

CONCLUSION

The characterization of a small gain region at 9p13.3 in gastric cancer cell lines and primary gastric adenocarcinoma samples has revealed MELK as a candidate target gene that is possibly related to the development of gastric cancer.

The role of Pax5 in leukemia: diagnosis and prognosis significance

Pax5 transcription factor, also known as B-cell specific activator protein (BSAP), plays a dual role in the hematopoietic system. Pax5 expression is essential in B-cell precursors for normal differentiation and maturation of B-cells. On the other hand, it inhibits the differentiation and progress toward other lineages. The expression of this factor is involved in several aspects of B-cell differentiation, including commitment, immunoglobulin gene rearrangement, BCR signal transduction and B-cell survival, so that the deletion or inactivating mutations of Pax5 cause cell arrest in Pro-B-cell stage. In recent years, point mutations, deletions and various rearrangements in Pax5 gene have been reported in several types of human cancers. However, no clear relationship has been found between these aberrations and disease prognosis. Specific expression of Pax5 in B-cells can raise it as a marker for the diagnosis and differentiation of B-cell leukemias and lymphomas as well as account for remission or relapse. Extensive studies on Pax5 along with other genes and immunomarkers are necessary for decisive results in this regard.