Micro Regional Heterogeneity of 64Cu-ATSM and 18F-FDG Uptake in Canine Soft Tissue Sarcomas: Relation to Cell Proliferation, Hypoxia and Glycolysis.
OBJECTIVE
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.
Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark; Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, Copenhagen N, Denmark.
Kamilla Westarp
KW
Zornhagen
Department of Micro- and Nanotechnology, Technical University of Denmark, Kgs. Lyngby, Denmark.
Anders E
AE
Hansen
Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, Copenhagen N, Denmark.
Jytte
J
Oxboel
Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, Copenhagen N, Denmark.
Andreas E
AE
Clemmensen
Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, Copenhagen N, Denmark.
Henrik H
HH
El Ali
Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Annemarie T
AT
Kristensen
Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, Copenhagen N, Denmark.
Andreas
A
Kjær
D000818:Animals; D049109:Cell Proliferation / Q000502:physiology; D003301:Copper Radioisotopes; D004285:Dogs; D019788:Fluorodeoxyglucose F18; D006019:Glycolysis / Q000502:physiology; D000860:Hypoxia / Q000503:physiopathology; D049268:Positron-Emission Tomography; D012509:Sarcoma / Q000175:diagnosis*
D003301:Copper Radioisotopes; D019788:Fluorodeoxyglucose F18