title: Galectin-3 up-regulation in hypoxic and nutrient deprived microenvironments promotes cell survival.
abstract: Galectin-3 (gal-3) is a β-galactoside binding protein related to many tumoral aspects, e.g. angiogenesis, cell growth and motility and resistance to cell death. Evidence has shown its upregulation upon hypoxia, a common feature in solid tumors such as glioblastoma multiformes (GBM). This tumor presents a unique feature described as pseudopalisading cells, which accumulate large amounts of gal-3. Tumor cells far from hypoxic/nutrient deprived areas express little, if any gal-3. Here, we have shown that the hybrid glioma cell line, NG97ht, recapitulates GBM growth forming gal-3 positive pseudopalisades even when cells are grafted subcutaneously in nude mice. In vitro experiments were performed exposing these cells to conditions mimicking tumor areas that display oxygen and nutrient deprivation. Results indicated that gal-3 transcription under hypoxic conditions requires previous protein synthesis and is triggered in a HIF-1α and NF-κB dependent manner. In addition, a significant proportion of cells die only when exposed simultaneously to hypoxia and nutrient deprivation and demonstrate ROS induction. Inhibition of gal-3 expression using siRNA led to protein knockdown followed by a 1.7-2.2 fold increase in cell death. Similar results were also found in a human GBM cell line, T98G. In vivo, U87MG gal-3 knockdown cells inoculated subcutaneously in nude mice demonstrated decreased tumor growth and increased time for tumor engraftment. These results indicate that gal-3 protected cells from cell death under hypoxia and nutrient deprivation in vitro and that gal-3 is a key factor in tumor growth and engraftment in hypoxic and nutrient-deprived microenvironments. Overexpression of gal-3, thus, is part of an adaptive program leading to tumor cell survival under these stressing conditions.
authors.affiliation: Faculdade de Medicina da Universidade de São Paulo, Instituto do Câncer do Estado de São Paulo, São Paulo, SP, Brazil.
authors.forename: Rafael Yamashita
authors.initials: RY
authors.lastname: Ikemori
authors.affiliation: Faculdade de Medicina da Universidade de São Paulo, Instituto do Câncer do Estado de São Paulo, São Paulo, SP, Brazil; Laboratório de Investigação Médica em Medicina Nuclear - LIM43, São Paulo, SP, Brazil.
authors.forename: Camila Maria Longo
authors.initials: CM
authors.lastname: Machado
authors.affiliation: Faculdade de Medicina da Universidade de São Paulo, Instituto do Câncer do Estado de São Paulo, São Paulo, SP, Brazil.
authors.forename: Karina Mie
authors.initials: KM
authors.lastname: Furuzawa
authors.affiliation: Departamento de Patologia do Instituto Adolfo Lutz, São Paulo, SP, Brazil.
authors.forename: Suely
authors.initials: S
authors.lastname: Nonogaki
authors.affiliation: Facultad de Medicina de La Universidad de La Republica, Montevideo, Uruguay.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Osinaga
authors.affiliation: Aichi-Medical University, Nagakute, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Umezawa
authors.affiliation: Instituto Federal do Rio de Janeiro, Instituto Nacional do Câncer, Rio de Janeiro, RJ, Brazil.
authors.forename: Marcelo Alex
authors.initials: MA
authors.lastname: de Carvalho
authors.affiliation: Departamento de Microbiologia e Imunologia, Instituto de Biologia, UNICAMP, Campinas, SP, Brazil.
authors.forename: Liana
authors.initials: L
authors.lastname: Verinaud
authors.affiliation: Faculdade de Medicina da Universidade de São Paulo, Instituto do Câncer do Estado de São Paulo, São Paulo, SP, Brazil.
authors.forename: Roger
authors.initials: R
authors.lastname: Chammas
mesh_terms: D000818:Animals; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002470:Cell Survival; D037502:Galectin 3 / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008819:Mice, Nude; D016328:NF-kappa B / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D015854:Up-Regulation
chemical_list: D037502:Galectin 3; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016328:NF-kappa B; D034741:RNA, Small Interfering; D010100:Oxygen