Animal Studies
The goal of the studies described herein are to develop first-in-class
agents for the chemoprevention of colorectal cancer in humans. Rodents
are widely regarded as essential models for early pharmacology and
toxicology studies, and mice were chosen owing to extensive published
data demonstrating CRC chemoprevention by conventional PDE5i. For all
animal studies, six-week-old C57BL6 mice were purchased from Jackson
Laboratories (Bar Harbor, ME), and allowed to acclimate to the Augusta
University animal facility for at least 2 weeks prior to
experimentation. Mice were housed in shoebox cages with 5 mice of the
same sex per cage with water and irradiated rodent chow (Teklad 8904)ad libitum . Cages were maintained in conventional specific
pathogen free environment at 24°C, and a 12 h light/dark cycle. On
completion of experiments or at any signs of morbidity, mice were
euthanized by controlled CO2 delivery for humane
asphyxiation followed by decapitation. The experimental design included
equal numbers of randomly chosen male and female mice for the
proof-of-principle pharmacokinetic studies, but only male mice were used
for the surgical procedure and for the colon proliferation studies since
our previous studies have found no difference in the response to cGMP
elevation on colon homeostasis or colon cancer prevention. Statistical
analysis was only undertaken for studies where each group size was at
least n = 5. All studies carried out with animals were approved by the
Augusta University Institutional Animal Care and Use Committee.
Descriptions of animal studies are compliant with the ARRIVE guidelines
(Percie du Sert et al. , 2020) and recommendations made by the
British Journal of Pharmacology (Lilley et al. , 2020).