Inhibition of SGK1 enhances mAR-induced apoptosis in MCF-7 breast cancer cells. 2015

Guilai Liu, and Sabina Honisch, and Guoxing Liu, and Sebastian Schmidt, and Stavros Pantelakos, and Saad Alkahtani, and Mahmoud Toulany, and Florian Lang, and Christos Stournaras
a Department of Physiology ; University of Tübingen ; Tübingen , Germany.

Functional membrane androgen receptors (mAR) have previously been described in MCF-7 breast cancer cells. Their stimulation by specific testosterone albumin conjugates (TAC) activate rapidly non-genomic FAK/PI3K/Rac1/Cdc42 signaling, trigger actin reorganization and inhibit cell motility. PI3K stimulates serum and glucocorticoid inducible kinase SGK1, which in turn regulates the function of mAR. In the present study we addressed the role of SGK1 in mAR-induced apoptosis. TAC-stimulated mAR activation elicited apoptosis of MCF-7 cells, an effect significantly potentiated by concomitant incubation of the cells with TAC and the specific SGK1 inhibitors EMD638683 and GSK650394. In line with this, TAC and EMD638683 activated caspase-3. These effects were insensitive to the classical androgen receptor (iAR) antagonist flutamide, pointing to iAR-independent, mAR-induced responses. mAR activation and SGK1 inhibition further considerably augmented the radiation-induced apoptosis of MCF-7 cells. Moreover, TAC- and EMD638683 triggered early actin polymerization in MCF-7 cells. Blocking actin restructuring with cytochalasin B abrogated the TAC- and EMD638683-induced pro-apoptotic responses. Further analysis of the molecular signaling revealed late de-phosphorylation of FAK and Akt. Our results demonstrate that mAR activation triggers pro-apoptotic responses in breast tumor cells, an effect significantly enhanced by SGK1 inhibition, involving actin reorganization and paralleled by down-regulation of FAK/Akt signaling.

UI MeSH Term Description Entries
D010766 Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Phosphorylations
D011944 Receptors, Androgen Proteins, generally found in the CYTOPLASM, that specifically bind ANDROGENS and mediate their cellular actions. The complex of the androgen and receptor migrates to the CELL NUCLEUS where it induces transcription of specific segments of DNA. Androgen Receptors,5 alpha-Dihydrotestosterone Receptor,Androgen Receptor,Dihydrotestosterone Receptors,Receptor, Testosterone,Receptors, Androgens,Receptors, Dihydrotestosterone,Receptors, Stanolone,Stanolone Receptor,Testosterone Receptor,5 alpha Dihydrotestosterone Receptor,Androgens Receptors,Receptor, 5 alpha-Dihydrotestosterone,Receptor, Androgen,Receptor, Stanolone,Stanolone Receptors,alpha-Dihydrotestosterone Receptor, 5
D001943 Breast Neoplasms Tumors or cancer of the human BREAST. Breast Cancer,Breast Tumors,Cancer of Breast,Breast Carcinoma,Cancer of the Breast,Human Mammary Carcinoma,Malignant Neoplasm of Breast,Malignant Tumor of Breast,Mammary Cancer,Mammary Carcinoma, Human,Mammary Neoplasm, Human,Mammary Neoplasms, Human,Neoplasms, Breast,Tumors, Breast,Breast Carcinomas,Breast Malignant Neoplasm,Breast Malignant Neoplasms,Breast Malignant Tumor,Breast Malignant Tumors,Breast Neoplasm,Breast Tumor,Cancer, Breast,Cancer, Mammary,Cancers, Mammary,Carcinoma, Breast,Carcinoma, Human Mammary,Carcinomas, Breast,Carcinomas, Human Mammary,Human Mammary Carcinomas,Human Mammary Neoplasm,Human Mammary Neoplasms,Mammary Cancers,Mammary Carcinomas, Human,Neoplasm, Breast,Neoplasm, Human Mammary,Neoplasms, Human Mammary,Tumor, Breast
D002462 Cell Membrane The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells. Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000199 Actins Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or F-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or G-actin. In conjunction with MYOSINS, actin is responsible for the contraction and relaxation of muscle. F-Actin,G-Actin,Actin,Isoactin,N-Actin,alpha-Actin,alpha-Isoactin,beta-Actin,gamma-Actin,F Actin,G Actin,N Actin,alpha Actin,alpha Isoactin,beta Actin,gamma Actin
D013739 Testosterone A potent androgenic steroid and major product secreted by the LEYDIG CELLS of the TESTIS. Its production is stimulated by LUTEINIZING HORMONE from the PITUITARY GLAND. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to DIHYDROTESTOSTERONE or ESTRADIOL. 17-beta-Hydroxy-4-Androsten-3-one,17-beta-Hydroxy-8 alpha-4-Androsten-3-one,8-Isotestosterone,AndroGel,Androderm,Andropatch,Androtop,Histerone,Sterotate,Sustanon,Testim,Testoderm,Testolin,Testopel,Testosterone Sulfate,17 beta Hydroxy 4 Androsten 3 one,17 beta Hydroxy 8 alpha 4 Androsten 3 one,8 Isotestosterone
D017209 Apoptosis A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, i.e., DNA FRAGMENTATION. It is genetically programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Apoptosis, Extrinsic Pathway,Apoptosis, Intrinsic Pathway,Caspase-Dependent Apoptosis,Classic Apoptosis,Classical Apoptosis,Programmed Cell Death,Programmed Cell Death, Type I,Apoptoses, Extrinsic Pathway,Apoptoses, Intrinsic Pathway,Apoptosis, Caspase-Dependent,Apoptosis, Classic,Apoptosis, Classical,Caspase Dependent Apoptosis,Cell Death, Programmed,Classic Apoptoses,Extrinsic Pathway Apoptoses,Extrinsic Pathway Apoptosis,Intrinsic Pathway Apoptoses,Intrinsic Pathway Apoptosis
D017346 Protein Serine-Threonine Kinases A group of enzymes that catalyzes the phosphorylation of serine or threonine residues in proteins, with ATP or other nucleotides as phosphate donors. Protein-Serine-Threonine Kinases,Serine-Threonine Protein Kinase,Serine-Threonine Protein Kinases,Protein-Serine Kinase,Protein-Serine-Threonine Kinase,Protein-Threonine Kinase,Serine Kinase,Serine-Threonine Kinase,Serine-Threonine Kinases,Threonine Kinase,Kinase, Protein-Serine,Kinase, Protein-Serine-Threonine,Kinase, Protein-Threonine,Kinase, Serine-Threonine,Kinases, Protein Serine-Threonine,Kinases, Protein-Serine-Threonine,Kinases, Serine-Threonine,Protein Kinase, Serine-Threonine,Protein Kinases, Serine-Threonine,Protein Serine Kinase,Protein Serine Threonine Kinase,Protein Serine Threonine Kinases,Protein Threonine Kinase,Serine Threonine Kinase,Serine Threonine Kinases,Serine Threonine Protein Kinase,Serine Threonine Protein Kinases

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