S100A8/A9 (calprotectin) negatively regulates G2/M cell cycle progression and growth of squamous cell carcinoma

PLoS One. 2013 Jul 9;8(7):e69395. doi: 10.1371/journal.pone.0069395. Print 2013.

Abstract

Malignant transformation results in abnormal cell cycle regulation and uncontrolled growth in head and neck squamous cell carcinoma (HNSCC) and other cancers. S100A8/A9 (calprotectin) is a calcium-binding heterodimeric protein complex implicated in cell cycle regulation, but the specific mechanism and role in cell cycle control and carcinoma growth are not well understood. In HNSCC, S100A8/A9 is downregulated at both mRNA and protein levels. We now report that downregulation of S100A8/A9 correlates strongly with a loss of cell cycle control and increased growth of carcinoma cells. To show its role in carcinogenesis in an in vitro model, S100A8/A9 was stably expressed in an S100A8/A9-negative human carcinoma cell line (KB cells, HeLa-like). S100A8/A9 expression increases PP2A phosphatase activity and p-Chk1 (Ser345) phosphorylation, which appears to signal inhibitory phosphorylation of mitotic p-Cdc25C (Ser216) and p-Cdc2 (Thr14/Tyr15) to inactivate the G2/M Cdc2/cyclin B1 complex. Cyclin B1 expression then downregulates and the cell cycle arrests at the G2/M checkpoint, reducing cell division. As expected, S100A8/A9-expressing cells show both decreased anchorage-dependent and -independent growth and mitotic progression. Using shRNA, silencing of S100A8/A9 expression in the TR146 human HNSCC cell line increases growth and survival and reduces Cdc2 inhibitory phosphorylation at Thr14/Tyr15. The level of S100A8/A9 endogenous expression correlates strongly with the reduced p-Cdc2 (Thr14/Tyr14) level in HNSCC cell lines, SCC-58, OSCC-3 and UMSCC-17B. S100A8/A9-mediated control of the G2/M cell cycle checkpoint is, therefore, a likely suppressive mechanism in human squamous cell carcinomas and may suggest new therapeutic approaches.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Calgranulin A / genetics*
  • Calgranulin A / metabolism
  • Calgranulin B / genetics*
  • Calgranulin B / metabolism
  • Carcinoma, Squamous Cell / genetics*
  • Carcinoma, Squamous Cell / metabolism
  • Cell Division / genetics*
  • Cell Line, Tumor
  • Cell Proliferation
  • G2 Phase / genetics*
  • G2 Phase Cell Cycle Checkpoints
  • Gene Expression Regulation, Neoplastic
  • Head and Neck Neoplasms / genetics*
  • Head and Neck Neoplasms / metabolism
  • Humans
  • Models, Biological
  • Protein Binding
  • Protein Phosphatase 2 / metabolism
  • Signal Transduction
  • Squamous Cell Carcinoma of Head and Neck

Substances

  • Calgranulin A
  • Calgranulin B
  • Protein Phosphatase 2