Imaging and modulating antisense microdistribution in solid human xenograft tumor models.
OBJECTIVE
The tumor microenvironment is complex and heterogeneous, populated by tortuous irregular vasculature, hypoxic cells, and necrotic regions. These factors can all contribute to the biodistribution difficulties encountered by most cancer therapeutic agents. Antisense oligodeoxynucleotides (ASO) are a class of therapeutics where limited information is available about their distribution within a solid tumor environment.


METHODS
To assess ASO distribution, a fluorescein-labeled phosphorothionated ASO based on the G3139 mismatch control was injected systemically (i.v.) into tumor-bearing severe combined immunodeficient mice. Hoechst 33342 was injected i.v. to visualize active vasculature. Unstained sections were imaged through tiled fluorescence stereomicroscopy and then quantitated using novel algorithms. Tumor sections from four human tumor models were examined (CaSki, DU-145, C666-1, and C15) for hypoxia, apoptosis/necrosis, and morphology.


RESULTS
For all four tumors, ASO accumulated within regions of hypoxia, necrosis, and apoptosis. Scatter plots of ASO versus active vasculature generated for each individual tumor revealed a consistent pattern of distribution of the ASO within each model. In C666-1 xenografts, the slopes of these scatter plots were significantly reduced from 0.41 to 0.16 when pretreated with the antivascular agent ZD6126 48 h before ASO injection. This was accompanied by the formation of large disseminated necrotic regions in the tumor, along with a 13.1 mmHg reduction in interstitial fluid pressure.


CONCLUSIONS
These data suggest the possibility that these algorithms might offer a generalizable and objective methodology to describe the distribution of molecular therapeutic agents within a tumor microenvironment and to quantitatively assess distribution changes in response to combination therapies.
Mocanu
Joseph D
JD
Division of Applied Molecular Oncology, Ontario Cancer Institute, Canada.
Yip
Kenneth W
KW
Skliarenko
Julia
J
Shi
Wei
W
Busson
Pierre
P
Lo
Kwok-Wai
KW
Bastianutto
Carlo
C
Liu
Fei-Fei
FF
D000465:Algorithms; D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003952:Diagnostic Imaging / Q000379:methods*; D006801:Humans; D000860:Hypoxia; D051379:Mice; D016513:Mice, SCID; D009336:Necrosis; D009368:Neoplasm Transplantation; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D009943:Organophosphorus Compounds / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays
D001562:Benzimidazoles; C455219:N-acetylcochinol-O-phosphate; D016376:Oligonucleotides, Antisense; D009943:Organophosphorus Compounds; C017807:bisbenzimide ethoxide trihydrochloride