RANK Ligand Modulation of Autophagy in Oral Squamous Cell Carcinoma Tumor Cells

J Cell Biochem. 2016 Jan;117(1):118-25. doi: 10.1002/jcb.25255.

Abstract

Autophagy is a cellular process to recycle nutrients and has been implicated in cancer treatment. Oral squamous cell carcinoma (OSCC) is the most common oral cancer which ranks 3% of cancers in men and 2% in women. In this study, immunohistochemical staining of OSCC tumor specimens from human subjects and an athymic mouse model demonstrated high levels of autophagy markers LC3-II and ATG5 expression. Further, we identified high levels LC3-II expression in OSCC tumor cell lines (SCC-1, SCC-12, and SCC-14a) compared to normal human epithelial (RWPE-1) cells. OSCC cells express high levels of RANK ligand (RANKL); however, a functional role in autophagy is unknown. Interestingly, RANKL stimulation significantly increased autophagosome-related gene expressions such as LC3, ATG5, BECN1, and PI3KC3 mRNA expression in OSCC cells. Further, Western blot analysis of total cell lysates demonstrated a dose-dependent increase in LC3-II and ATG5 expression in RANKL-stimulated cells. In addition, RANKL increased expression of LC3-I and LC3-II, essential for autophagosome formation. Confocal microscopy analysis of LC3-II and localization with lysosome further confirms autophagosome formation in response to RANKL treatment in OSCC cells. Collectively, our results indicate a novel function of RANKL to induce autophagosome formation, and could be a potential therapeutic target to control OSCC tumor progression.

Keywords: ATG5; AUTOPHAGOSOME; LC3; ORAL SQUAMOUS CELL CARCINOMA (OSCC); RANK LIGAND.

Publication types

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

MeSH terms

  • Autophagy / genetics
  • Autophagy / physiology*
  • Autophagy-Related Protein 5 / genetics
  • Autophagy-Related Protein 5 / metabolism
  • Carcinoma, Squamous Cell / metabolism*
  • Cell Line, Tumor
  • Humans
  • In Vitro Techniques
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Mouth Neoplasms / metabolism*
  • RANK Ligand / genetics
  • RANK Ligand / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • ATG5 protein, human
  • Autophagy-Related Protein 5
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • RANK Ligand