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Gahete M.D.,Hospital Universitario Reina Sofia And Ciberobn Fisiopatologia Of La Obesidad | Cordoba-Chacon J.,Hospital Universitario Reina Sofia And Ciberobn Fisiopatologia Of La Obesidad | Hergueta-Redondo M.,Research Institute Biomedicas Alberto Sols | Martinez-Fuentes A.J.,Hospital Universitario Reina Sofia And Ciberobn Fisiopatologia Of La Obesidad | And 4 more authors.
PLoS ONE | Year: 2011

The human ghrelin gene, which encodes the ghrelin and obestatin peptides, contains 5 exons (Ex), with Ex1-Ex4 encoding a 117 amino-acid (aa) preproprotein that is known to be processed to yield a 28-aa (ghrelin) and/or a 23-aa (obestatin) mature peptides, which possess biological activities in multiple tissues. However, the ghrelin gene also encodes additional peptides through alternative splicing or post-translational modifications. Indeed, we previously identified a spliced mRNA ghrelin variant in mouse (In2-ghrelin-variant), which is regulated in a tissue-dependent manner by metabolic status and may thus be of biological relevance. Here, we have characterized a new human ghrelin variant that contains Ex0-1, intron (In) 1, and Ex2 and lacks Ex3-4. This human In1-ghrelin variant would encode a new prepropeptide that conserves the first 12aa of native-ghrelin (including the Ser3-potential octanoylation site) but has a different C-terminal tail. Expression of In1-variant was detected in 22 human tissues and its levels were positively correlated with those of ghrelin-O-acyltransferase (GOAT; p = 0.0001) but not with native-ghrelin expression, suggesting that In1-ghrelin could be a primary substrate for GOAT in human tissues. Interestingly, levels of In1-ghrelin variant expression in breast cancer samples were 8-times higher than those of normal mammary tissue, and showed a strong correlation in breast tumors with GOAT (p = 0.0001), ghrelin receptor-type 1b (GHSR1b; p = 0.049) and cyclin-D3 (a cell-cycle inducer/proliferation marker; p = 0.009), but not with native-ghrelin or GHSR1a expression. Interestingly, In1-ghrelin variant overexpression increased basal proliferation of MDA-MB-231 breast cancer cells. Taken together, our results provide evidence that In1-ghrelin is a novel element of the ghrelin family with a potential pathophysiological role in breast cancer. Source


Moreno-Bueno G.,Research Institute Biomedicas Alberto Sols | Moreno-Bueno G.,Anderson Cancer Center Madrid | Salvador F.,Research Institute Biomedicas Alberto Sols | Martin A.,Research Institute Biomedicas Alberto Sols | And 15 more authors.
EMBO Molecular Medicine | Year: 2011

Basal-like breast carcinoma is characterized by the expression of basal/myoepithelial markers, undifferentiated phenotype, highly aggressive behaviour and frequent triple negative status (ESR-, PR-, Her2neu-). We have previously shown that epithelial-mesenchymal transition (EMT) occurs in basal-like breast tumours and identified Lysyl-oxidase-like 2 (LOXL2) as an EMT player and poor prognosis marker in squamous cell carcinomas. We now show that LOXL2 mRNA is overexpressed in basal-like human breast carcinomas. Breast carcinoma cell lines with basal-like phenotype show a specific cytoplasmic/perinuclear LOXL2 expression, and this subcellular distribution is significantly associated with distant metastatic incidence in basal-like breast carcinomas. LOXL2 silencing in basal-like carcinoma cells induces a mesenchymal-epithelial transition (MET) associated with a decrease of tumourigenicity and suppression of metastatic potential. Mechanistic studies indicate that LOXL2 maintains the mesenchymal phenotype of basal-like carcinoma cells by a novel mechanism involving transcriptional downregulation of Lgl2 and claudin1 and disorganization of cell polarity and tight junction complexes. Therefore, intracellular LOXL2 is a new candidate marker of basal-like carcinomas and a target to block metastatic dissemination of this aggressive breast tumour subtype. © 2011 EMBO Molecular Medicine. Source

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