Fasting Reduces Intestinal Radiotoxicity Enabling Dose-Escalated Radiotherapy For Pancreatic Cancer

<p>Surgical resection is the only potentially curative treatment for pancreatic cancer, but only 15-20% of patients have resectable tumors. In unresectable cases, stereotactic body radiotherapy (SBRT) may be used to give tumor-directed radiotherapy (RT). Unfortunately, this can cause severe gastrointestinal (GI) toxicity due to proximity of the pancreatic head to the duodenum. Protecting the intestine from the toxic side-effects of radiation may enable dose-escalation that could achieve more effective local control of disease. We and others have previously shown that a fast of 24 hours protects mice from lethal doses of the DNA-damaging agent etoposide. In this study, we demonstrate that a 24 hour fast also protects mice from lethal doses of total-abdominal radiation. Histologic analyses using the Withers-Elkind microcolony assay show that fasting protected small intestinal (SI) stem cells from radiation damage and promoted early regeneration. To show a proof-of-principle for the use of this radioporotective maneuver in cancer therapy, we used an orthotopic model of pancreatic cancer using KPC tumor cells syngeneic to C57BL/6. Here, we show that fasting-mediated intestinal protection enabled dose escalated SBRT for treatment of these orthotopic tumors. RT with fasting-mediated radioprotection delayed tumor growth and improved survival compared to controls. Given this robust phenotype, we developed a 3D culture ex vivo assay using intestinal stem cell-enriched epithelial spheroid cultures. We modified these intestinal spheroids with a bioluminescent reporter and used these cells to develop a modified clonogenic assay for 3D culture that can be used to identify novel radioprotectors, such as a fasting mimetic. Taken together, these results suggest that fasting protects small intestinal stem cells, allowing animals to receive potentially curative doses of abdominal radiation that would otherwise be lethal. Future work will aim to identifying the mechanisms by which fasting confers intestinal protection and drug candidates that can be used to mimic this fasting-mediated protection.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation (PhD)

Year dc:date.available

2019

Authors dc:creator

• de la Cruz Bonilla, Marimar
• <p>0000-0003-3958-7403</p>

Contributors dc:contributor

• Helen Piwnica-Worms
• Cullen M. Taniguchi
• Michelle Barton

• radiation
• small intestine
• toxicity
• pancreas
• pdac
• stem cells
• fasting
• Cancer Biology
• Radiation Medicine

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/969

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-2016