title: Metallothionein 1G promotes the differentiation of HT-29 human colorectal cancer cells.
abstract: Metallothioneins (MTs) are a family of low-molecular-weight, cysteine-rich proteins involved in zinc and redox metabolism, that are epigenetically downregulated during colorectal cancer (CRC) progression, but may be re-induced with a variety of agents. Since loss of MT expression is associated with a worse prognosis, in the present study we investigated the effects of overexpression of the most significantly downregulated isoform in CRC, namely MT1G, on the HT-29 cell line. Overexpression of MT1G resulted in xenograft tumors with an aberrant morphology, characterized by an evident increase in mucin-containing cells that were identified as goblet cells under electron microscopy. Immunohistochemical detection of CDX2 and cytokeratin 20 was also increased, as were goblet‑cell and enterocyte-specific genes by qRT-PCR. Microarray analysis of gene expression confirmed the alteration of several differentiation signaling pathways, including the Notch pathway. Using sodium butyrate and post-confluent growth as inducers of differentiation, we demonstrated that MT1G does indeed play a functional role in promoting goblet over enterocyte differentiation in vitro. Labile zinc is also induced upon differentiation of CRC cells, functionally contributing to enterocyte over goblet differentiation, as revealed using zinc‑specific chelating agents. Overall, our results uncover a new tumor-suppressor activity of MT1G in promoting the differentiation of at least some CRC tumors, and implicate MTs and zinc signaling as new players in colorectal differentiation. This further contributes to the hypothesis that re-induction of MTs may have therapeutic value by diminishing the aggressiveness of CRC tumors.
authors.affiliation: Cancerology Laboratory, Leloir Institute, IIBBA-CONICET, Buenos Aires 1405, Argentina.
authors.forename: Juan Martín
authors.initials: JM
authors.lastname: Arriaga
authors.affiliation: Acute Interzonal General Hospiutal 'Eva Perón', Buenos Aires 1650, Argentina.
authors.forename: Alicia Inés
authors.initials: AI
authors.lastname: Bravo
authors.affiliation: Cancerology Laboratory, Leloir Institute, IIBBA-CONICET, Buenos Aires 1405, Argentina.
authors.forename: José
authors.initials: J
authors.lastname: Mordoh
authors.affiliation: Center for Oncology Research, Cancer Foundation (CIO-FUCA), Buenos Aires 1426, Argentina.
authors.forename: Michele
authors.initials: M
authors.lastname: Bianchini
mesh_terms: D000818:Animals; D020148:Butyric Acid / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D019073:HT29 Cells; D006801:Humans; D008297:Male; D008668:Metallothionein / Q000378:metabolism*; D008819:Mice, Nude; D020411:Oligonucleotide Array Sequence Analysis; D023041:Xenograft Model Antitumor Assays; D015032:Zinc / Q000378:metabolism
chemical_list: C499629:MT1G protein, human; D020148:Butyric Acid; D008668:Metallothionein; D015032:Zinc