Galectin-3 up-regulation in hypoxic and nutrient deprived microenvironments promotes cell survival

PLoS One. 2014 Nov 4;9(11):e111592. doi: 10.1371/journal.pone.0111592. eCollection 2014.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Hypoxia
  • Cell Line, Tumor
  • Cell Survival
  • Galectin 3 / analysis
  • Galectin 3 / genetics*
  • Galectin 3 / metabolism
  • Gene Expression Regulation, Neoplastic
  • Glioblastoma / genetics
  • Glioblastoma / metabolism
  • Glioblastoma / pathology*
  • Humans
  • Hypoxia / genetics
  • Hypoxia / metabolism
  • Hypoxia / pathology
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Mice, Nude
  • NF-kappa B / metabolism
  • Oxygen / metabolism
  • RNA Interference
  • RNA, Small Interfering / genetics
  • Up-Regulation

Substances

  • Galectin 3
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • NF-kappa B
  • RNA, Small Interfering
  • Oxygen

Grants and funding

Contract grant sponsor: Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP www.fapesp.br), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq www.cnpq.br) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes-UDELAR). Contract grant number: CEPID 98/14247-6, FAPESP 2009/10857-0 and INCT-Redoxoma. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.