Micro Regional Heterogeneity of 64Cu-ATSM and 18F-FDG Uptake in Canine Soft Tissue Sarcomas: Relation to Cell Proliferation, Hypoxia and Glycolysis

PLoS One. 2015 Oct 26;10(10):e0141379. doi: 10.1371/journal.pone.0141379. eCollection 2015.

Abstract

Objectives: Tumour microenvironment heterogeneity is believed to play a key role in cancer progression and therapy resistance. However, little is known about micro regional distribution of hypoxia, glycolysis and proliferation in spontaneous solid tumours. The overall aim was simultaneous investigation of micro regional heterogeneity of 64Cu-ATSM (hypoxia) and 18F-FDG (glycolysis) uptake and correlation to endogenous markers of hypoxia, glycolysis, proliferation and angiogenesis to better therapeutically target aggressive tumour regions and prognosticate outcome.

Methods: Exploiting the different half-lives of 64Cu-ATSM (13 h) and 18F-FDG (2 h) enabled simultaneous investigation of micro regional distribution of hypoxia and glycolysis in 145 tumour pieces from four spontaneous canine soft tissue sarcomas. Pairwise measurements of radioactivity and gene expression of endogenous markers of hypoxia (HIF-1α, CAIX), glycolysis (HK2, GLUT1 and GLUT3), proliferation (Ki-67) and angiogenesis (VEGFA and TF) were performed. Dual tracer autoradiography was compared with Ki-67 immunohistochemistry.

Results: Micro regional heterogeneity in hypoxia and glycolysis within and between tumour sections of each tumour piece was observed. The spatial distribution of 64Cu-ATSM and 18F-FDG was rather similar within each tumour section as reflected in moderate positive significant correlations between the two tracers (ρ = 0.3920-0.7807; p = 0.0180 -<0.0001) based on pixel-to-pixel comparisons of autoradiographies and gamma counting of tumour pieces. 64Cu-ATSM and 18F-FDG correlated positively with gene expression of GLUT1 and GLUT3, but negatively with HIF-1α and CAIX. Significant positive correlations were seen between Ki-67 gene expression and 64Cu-ATSM (ρ = 0.5578, p = 0.0004) and 18F-FDG (ρ = 0.4629-0.7001, p = 0.0001-0.0151). Ki-67 gene expression more consistently correlated with 18F-FDG than with 64Cu-ATSM.

Conclusions: Micro regional heterogeneity of hypoxia and glycolysis was documented in spontaneous canine soft tissue sarcomas. 64Cu-ATSM and 18F-FDG uptakes and distributions showed significant moderate correlations at the micro regional level indicating overlapping, yet different information from the tracers.18F-FDG better reflected cell proliferation as measured by Ki-67 gene expression than 64Cu-ATSM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Proliferation / physiology
  • Copper Radioisotopes*
  • Dogs
  • Fluorodeoxyglucose F18*
  • Glycolysis / physiology
  • Hypoxia / physiopathology
  • Positron-Emission Tomography
  • Sarcoma / diagnosis*

Substances

  • Copper Radioisotopes
  • Fluorodeoxyglucose F18

Grants and funding

This study was supported by a PhD fellowship co-funded by the Department of Veterinary Clinical and Animal Sciences, University of Copenhagen; Copenhagen University Hospital and The Graduate Programme of Companion Animal Clinical and Comparative Sciences, University of Copenhagen granted to KWZ. Financial support from the Foundation of Scientific Studies in Companion Animal Diseases and Treatment and the Foundation of Disease Control in Companion Animals received by KWZ is gratefully acknowledged. Likewise the John and Birthe Meyer Foundation; the AP Møller Foundation; the Novo Nordisk Foundation; the Lundbeck Foundation; the Svend Andersen Foundation; the Arvid Nilsson Foundation; the Research Foundation of Rigshospitalet; the Research Foundation of the Capital Region; the Innovation Fund Denmark and the Research Council for Independent Research is gratefully acknowledged for funding granted to AK. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.