Spectral imaging-based methods for quantifying autophagy and apoptosis

Cancer Biol Ther. 2011 Aug 15;12(4):349-56. doi: 10.4161/cbt.12.4.17175. Epub 2011 Aug 15.

Abstract

Spectral imaging systems are capable of detecting and quantifying subtle differences in light quality. In this study we coupled spectral imaging with fluorescence and white light microscopy to develop new methods for quantifying autophagy and apoptosis. For autophagy, we employed multispectral imaging to examine spectral changes in the fluorescence of LC3-GFP, a chimeric protein commonly used to track autophagosome formation. We found that punctate autophagosome-associated LC3-GFP exhibited a spectral profile that was distinctly different from diffuse cytosolic LC3-GFP. We then exploited this shift in spectral quality to quantify the amount of autophagosome-associated signal in single cells. Hydroxychloroquine (CQ), an anti-malarial agent that increases autophagosomal number, significantly increased the punctate LC3-GFP spectral signature, providing proof-of-principle for this approach. For studying apoptosis, we employed the Prism and Reflector Imaging Spectroscopy System (PARISS) hyperspectral imaging system to identify a spectral signature for active caspase-8 immunostaining in ex vivo tumor samples. This system was then used to rapidly quantify apoptosis induced by lexatumumab, an agonistic TRAIL-R2/DR5 antibody, in histological sections from a preclinical mouse model. We further found that the PARISS could accurately distinguish apoptotic tumor regions in hematoxylin and eosin-stained sections, which allowed us to quantify death receptor-mediated apoptosis in the absence of an apoptotic marker. These spectral imaging systems provide unbiased, quantitative and fast means for studying autophagy and apoptosis and complement the existing methods in their respective fields.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal / pharmacology
  • Apoptosis / drug effects
  • Apoptosis / physiology*
  • Autophagy / drug effects
  • Autophagy / physiology*
  • Caspase 8 / metabolism
  • Cell Line, Tumor
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / pathology
  • Diagnostic Imaging / methods*
  • Female
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Hydroxychloroquine / pharmacology
  • Mice
  • Mice, Nude
  • Microscopy, Fluorescence / methods
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Neoplasm Transplantation
  • Phagosomes / drug effects
  • Phagosomes / metabolism
  • Receptors, TNF-Related Apoptosis-Inducing Ligand / immunology
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Reproducibility of Results
  • Spectrum Analysis / methods*
  • Transplantation, Heterologous

Substances

  • Antibodies, Monoclonal
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • Receptors, TNF-Related Apoptosis-Inducing Ligand
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Hydroxychloroquine
  • lexatumumab
  • Caspase 8