LIMITING THE TOXICITY OF CHEMOTHERAPY BY ENHANCING REGENERATION OF INTESTINAL STEM CELLS

Chemotherapy is the backbone treatment for most malignancies. Typical cytotoxic chemotherapy drugs, such as doxorubicin, a topoisomerase II inhibitor, also harm normal cells that divide rapidly, such as the gastrointestinal lining, and cause morbidity and mortality that limits medical treatment. There is a need to reduce chemotherapy toxicity and thus provide a therapeutic benefit and improve overall quality of life of cancer patients. Intestinal stem cells are selectively killed by chemotherapy drugs, which trigger a poorly characterized activation of quiescent stem cells and/or progenitors for crypt regeneration. Growth Factor‐Independent 1 (GFI1) is a zinc finger transcriptional repressor implicated in the differentiation of secretory precursors into goblet and Paneth cells in the intestinal epithelium. Here, we hypothesize that following injury, increasing reversion of Gfi1 + secretory cells into stem cells will improve intestinal epithelium regeneration and mitigate chemo‐induced injury. Methods In our injury model, mice were treated with 20 mg/kg Doxorubicin through intraperitoneal injection leading to Lgr5+ stem cell injury and crypt loss. Gfi1 reporter mice (Gfi1cre; ROSA26 floxSTOP‐ YFP ) mice and intestinal organoids were used to investigate intestinal stem cell reversion and repair mechanism following injury. Results Under homeostatic conditions, Gfi1‐lineal cells were secretory Paneth and Goblet cells, which were not part of the stem cell pool. After injury, we found that Gfi1 + secretory cells can re‐enter the cell cycle and give rise to all cell lineages of the intestinal epithelium, indicating that Gfi1‐lineal cells revert to become active stem cells and repopulate the stem cell pool following tissue injury. The extent of reversion was generally correlated with the severity of injury as assessed by dysmorphic crypts. To identify potential boosters of intestinal regeneration, we generated three‐dimensional organoid cultures from Gfi1 reporter mice which provide a convenient and physiologically relevant model to identify key pathways regulating stem cell injury and regeneration caused by chemotherapy drugs. Our results demonstrated that PI3kinase/AKT activation using PTEN inhibitor improved cell survival, and elevated WNT signaling using high R‐spondin treatment increased efficiency of Gfi1 + cell reversion upon injury. High R‐spondin treatment and PTEN inhibition combined to enhance both survival and reversion upon injury. Additionally, we used AKT inhibitor to suppress AKT activity. AKT inhibition prevented survival of organoids after injury despite R‐spondin or PTEN inhibitor co‐treatment, indicating that AKT is epistatic to WNT signaling, and activation of AKT after injury is critical for intestinal epithelium regeneration. Conclusions These findings indicate that Gfi1 + secretory cells display plasticity and can reacquire stemness upon tissue damage. Moreover, PI3kinase/AKT and WNT are key regulators of cell survival and stem cell reversion after severe tissue injury. Our studies in intestinal stem cells will improve our current understanding injury‐induced regeneration and identify potential therapeutic strategies to mitigate the effects of chemo‐induced normal tissue injury and improve cancer chemotherapy. Support or Funding Information NIH R01 DK092306 U01 DK103117 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .