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Elucidating the Role of the Maternal Embryonic Leucine Zipper Kinase in Adrenocortical Carcinoma.

ABSTRACT: Adrenocortical carcinoma (ACC) is an aggressive cancer with a 5-year survival rate <35%. Mortality remains high due to lack of targeted therapies. Using bioinformatic analyses, we identified maternal embryonic leucine zipper kinase (MELK) as 4.1-fold overexpressed in ACC compared with normal adrenal samples. High MELK expression in human tumors correlated with shorter survival and with increased expression of genes involved in cell division and growth. We investigated the functional effects of MELK inhibition using newly developed ACC cell lines with variable MELK expression, CU-ACC1 and CU-ACC2, compared with H295R cells. In vitro treatment with the MELK inhibitor, OTSSP167, resulted in a dose-dependent decrease in rates of cell proliferation, colony formation, and cell survival, with relative sensitivity of each ACC cell line based upon the level of MELK overexpression. To confirm a MELK-specific antitumorigenic effect, MELK was inhibited in H295R cells via multiple short hairpin RNAs. MELK silencing resulted in 1.9-fold decrease in proliferation, and 3- to 10-fold decrease in colony formation in soft agar and clonogenicity assays, respectively. In addition, although MELK silencing had no effect on survival in normoxia, exposure to a hypoxia resulted in a sixfold and eightfold increase in apoptosis as assessed by caspase-3 activation and TUNEL, respectively. Together these data suggest that MELK is a modulator of tumor cell growth and survival in a hypoxic microenvironment in adrenal cancer cells and support future investigation of its role as a therapeutic kinase target in patients with ACC.

SUBMITTER: Kiseljak-Vassiliades K

PROVIDER: S-EPMC6669820 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Elucidating the Role of the Maternal Embryonic Leucine Zipper Kinase in Adrenocortical Carcinoma.

Kiseljak-Vassiliades Katja K Zhang Yu Y Kar Adwitiya A Razzaghi Raud R Xu Mei M Gowan Katherine K Raeburn Christopher D CD Albuja-Cruz Maria M Jones Kenneth L KL Somerset Hilary H Fishbein Lauren L Leong Stephen S Wierman Margaret E ME

Endocrinology 20180701 7

Adrenocortical carcinoma (ACC) is an aggressive cancer with a 5-year survival rate <35%. Mortality remains high due to lack of targeted therapies. Using bioinformatic analyses, we identified maternal embryonic leucine zipper kinase (MELK) as 4.1-fold overexpressed in ACC compared with normal adrenal samples. High MELK expression in human tumors correlated with shorter survival and with increased expression of genes involved in cell division and growth. We investigated the functional effects of M ...[more]

PMID: 29790920

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Project description:Background:Maternal embryonic leucine zipper kinase (MELK) is an atypical member of the snf1/AMPK family of serine-threonine kinases, involved in diverse physiological and pathological processes, including cell proliferation, apoptosis, embryogenesis, cancer treatment resistance, and RNA processing. MELK is highly expressed in human cancers and is associated with more aggressive forms of astrocytoma, glioblastoma, breast cancer, and melanoma to date, no information about porcine MELK (pMELK) has been reported. Methods:In this study, the pMELK coding sequence was cloned from swine spleen and characterized. We also quantitatively determined the expression of MELK in 11 tissues isolated from a piglet and determined its subcellular localization when expressed in swine umbilical vein endothelial cells (SUVEC) as a fusion protein. Moreover, we report the functional characterization of pMELK protein concerning its role in apoptosis. Results:Sequencing analysis showed that full-length of pMELK is 2,072 bp with 17 exons, encoding 655 amino acids, including an S-TKc conserved domain. Comparison of pMELK with ten other mammalian species of their orthologous sequences showed >91% homology and an evolutionary distance <0.05, demonstrating that MELK is highly conserved in evolution. Relative quantification of MELK expression in 11 tissue samples isolated from 30-day-old piglets showed MELK expression in all tested organs and the highest expression in the superficial inguinal lymph node. Constructed a plasmid named pEGFP-MELK, and the fusion protein GFP-MELK was successfully expressed in SUVECs. Fluorescence microscopy revealed the subcellular distribution of the fusion protein GFP-MELK was limited to the cytoplasm. About function, Flow cytometry analysis showed that overexpression of GFP-pMELK in SUVEC cells enhances staurosporine (STS)-induced apoptosis, but not significantly different. The pMELK protein also was found to interact with porcine BCL-G and transient transfection of the recombinant plasmid pCMV-HA-pMELK into SUVEC cells stably expressing GFP-pBCL-G protein inhibited pBCL-G -induced apoptosis significantly. Conclusions:The present study provided useful information on pMELK basic details and function in apoptosis offer a potential new molecular model for disease interventions and disease related to human MELK and BCL-G.

Dataset Information

Elucidating the Role of the Maternal Embryonic Leucine Zipper Kinase in Adrenocortical Carcinoma.

Publications

Elucidating the Role of the Maternal Embryonic Leucine Zipper Kinase in Adrenocortical Carcinoma.

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