e-Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2020

Therapeutic inhibition vs. intestinal deletion of CYP24A1 and its effects on chemotherapy-induced gastrointestinal mucositis (#207)

Cyan L Sylvester 1 , Paul H Anderson 1 , Andrea M Stringer 1
  1. University of South Australia, Adelaide, SOUTH AUSTRALIA (SA), Australia

Aims: 5-fluorouracil (5-FU) is a chemotherapy agent known to cause gastrointestinal mucositis (GM), for which there is currently no effective treatment. Vitamin D maintains barrier function in the intestine, and therefore may reduce severity of GM. We investigated the incidence and severity 5-FU-induced GM for both intestine-specific gene deletion of CYP24A1 vs. therapeutic inhibition of CYP24A1 in animal models, investigating specific effects on goblet cells.

Methods: Male transgenic Vill-Cre-CYP24A1 homozygous knock-out and control mice (n=18, 10 weeks old) received a single intraperitoneal injection of 450mg/kg 5-fluorouracil (5-FU) or saline (vehicle control). Wild type C57Bl6 mice (n=36, 10 weeks old) received a single intraperitoneal injection of 450mg/kg 5-FU or saline, and subcutaneous 500ng/kg CYP24A1 inhibitor or saline daily for five days prior and two days following 5-FU administration. All mice were humanely killed 48 h following 5-FU administration. Routine H&E and Alcian blue-PAS mucin staining were carried out on intestinal sections. Villous height (VH), villous area (VA) and crypt depth (CD) were measured, and goblet cells counts (GCC) were tallied in the intestine using NDP.view 2. One-way ANOVA (with Tukey’s test) and Kruskal–Wallis analysis were used for statistical analyses for parametric and non-parametric data, respectively.

Results: 5-FU significantly reduced VH (p=0.0005) VA (p=0.0006) in the small intestine and reduced CD (p=0.0094) in the colon. Therapeutic inhibition of CYP24A1 administered with 5-FU significantly increased VH in the small intestine compared to 5-FU alone (p=0.0491). 5-FU significantly decreased GCC per villus in both the inhibition and deletion models in the small intestine (p=0.0002). Colon GCC were unchanged in both the inhibition and deletion models.

Conclusions: CYP24A1 inhibition or deletion alleviates intestinal damage in 5-FU-treated mice. Our findings suggest a potential mechanism is maintaining barrier function. Specific studies investigating barrier function are now required to fully elucidate the mechanisms.