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SILAC identifies LAD1 as an oncogenic filamin binder regulating actin dynamics in response to EGF and marking aggressive breast tumors

ABSTRACT: Mutations mimicking growth factor-induced proliferation and motility characterize some aggressive subtypes of mammary tumors. To unravel novel players, we applied phosphoproteomics on untransformed mammary cells, which were pre-stimulated with the epidermal growth factor (EGF). This analysis identified ladinin-1 (LAD1), a hitherto poorly characterized protein, as a phosphor-effector of the EGF-to-ERK pathway. We report that LAD1 is essential for mammary cell proliferation and migration. LAD1 is transcriptionally induced, undergoes phosphorylation by EGF and co-localizes with actin stress fibers. Yeast 2-hybrids and co-immunoprecipitation screens revealed that LAD1 binds with filamins, actin cross-linking proteins. Co-sedimentation analyses attribute to LAD1 a role in actin treadmilling, probably in conjuction with SFN/14-3-3sigma. Depletion of LAD1 led to a decrease in viability related transcripts, and inhibited growth of mammary xenografts in an animal model. Furthermore, LAD1 is highly expressed in two aggressive subtypes of breast cancer, as well as predicts poor patient prognosis. These studies identify a new cytoskeletal component essential for signal transduction and for the acquisition of oncogenic attributes by human mammary tumors.

ORGANISM(S): Homo sapiens

PROVIDER: GSE103531 | GEO | 2018/01/31

REPOSITORIES: GEO

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Project description:The present experiments were performed to determine the roles of estrogen receptors M-NM-1 and M-NM-2 (ERM-NM-1 and ERM-NM-2) in normal and neoplastic development in the mouse mammary gland. In wild-type mice, in vivo administration of estradiol (E) + progesterone (P) stimulated mammary ductal growth and alveolar differentiation. Mammary glands from mice in which the ERM-NM-2 gene has been deleted (M-NM-2ERKO mice) demonstrated normal ductal growth and differentiation in response to E + P. By contrast, mammary glands from mice in which the ERM-NM-1 gene has been deleted (M-NM-1ERKO mice) demonstrated only rudimentary ductal structures that did not differentiate in response to E + P. EGF demonstrates estrogen-like activity in the mammary glands of M-NM-1ERKO mice: treatment of M-NM-1ERKO mice with EGF + P (without E) supported normal mammary gland development, induced expression of progesterone receptor (PR), and increased levels of G- protein-coupled receptor (GPR30) protein. Mammary gland development in M-NM-2ERKO mice treated with EGF + P was comparable to that of wild-type mice receiving EGF + P; EGF had no statistically significant effects on the induction of PR or expression of GPR30 in mammary glands harvested from either wild-type mice or M-NM-2ERKO mice. In vitro exposure of mammary glands to 7,12-dimethylbenz[a]anthracene (DMBA) induced preneoplastic mammary alveolar lesions (MAL) in glands from wild-type mice and M-NM-2ERKO mice, but failed to induce MAL in mammary glands from M-NM-1ERKO mice. Microarray analysis of DMBA-treated mammary glands identified 28 functional pathways whose expression was significantly different in M-NM-1ERKO mice versus both M-NM-2ERKO and wild-type mice; key functions that were differentially expressed in M-NM-1ERKO mice included cell division, cell proliferation, and apoptosis. The data demonstrate distinct roles for ERM-NM-1 and ERM-NM-2 in normal and neoplastic development in the mouse mammary gland, and suggest that EGF can mimic the ERM-NM-1-mediated effects of E in this organ. Gene expression of mammary gland organ culture and DMBA-induced lesions from 4 mouse strains.

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SILAC identifies LAD1 as an oncogenic filamin binder regulating actin dynamics in response to EGF and marking aggressive breast tumors

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