ORCID ID
Graduation Date
Summer 8-9-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Programs
Cancer Research
First Advisor
Punita Dhawan
Second Advisor
Amar B. Singh
Third Advisor
Kurt W. Fisher
Fourth Advisor
Geoffrey Thiele
Abstract
Colitis-associated cancer (CAC) is the most devastating complication of longstanding inflammatory bowel disease (IBD). Understanding the mechanisms underlying the switch from damage-repair to dysplasia in IBD is critical for identifying novel therapies to facilitate mucosal healing while mitigating CAC risk. Microtubule-associated serine-threonine kinase-like (MASTL), though crucial in cell growth and repair, is upregulated in sporadic colorectal cancer and CAC. This study sought to delineate the role of MASTL in colitis and CAC development.
First, we examined whether MASTL is associated with colitis and recovery. Review of publicly available data found significant elevation of MASTL and interleukin (IL)-22 in biopsies from late-stage ulcerative colitis patients compared to controls, with MASTL upregulation associated with high IL-22 expression. IL-22 helps restore intestinal barrier integrity post-colitis but is also elevated in CAC. Functional similarities between IL-22 and MASTL led us to hypothesize that IL-22 elevates MASTL expression to promote intestinal epithelial regeneration post-colitis. We confirmed higher MASTL expression in IBD patient colon samples compared to controls. In vitro, IL-22 increases MASTL protein in colon cell lines via AKT signaling, with MASTL knockout (KO) impeding IL-22-induced cell proliferation and survival. Further, carbonic anhydrase IX (CAIX)—known to be associated with colitis and CAC—was found to interact with and stabilize MASTL. CAIX-MASTL association increased post-IL-22, and CAIX inhibition abrogated IL-22-induced MASTL upregulation/stabilization.
Next, we wanted to understand how MASTL regulates epithelial recovery and promotes progression to CAC. For this, we observed the effects of intestine-localized, inducible MASTL KO in mouse models of colitis recovery and CAC. Loss of MASTL induced significant epithelial injury, decreased cell proliferation, and impaired recovery. In the AOM/DSS model of CAC, control mice developed low- and high-grade tumors while MASTL KO mice developed only low-grade tumors and had reduced β-catenin expression/nuclear localization. Single cell RNA sequencing (scRNA-seq) of mouse colonic mucosa revealed that MASTL is enriched in transit-amplifying and stem cells. MASTL KO mice demonstrate depletion of these cell types and downregulation of pathways vital for stem cell maintenance. Our findings demonstrate important, novel functions of MASTL in colon epithelial homeostasis and tumorigenesis via intestinal stem cell regulation.
Recommended Citation
Pravoverov, Kristina, "Understanding the role of MASTL in colon homeostasis and colitis-associated cancer development" (2024). Theses & Dissertations. 862.
https://digitalcommons.unmc.edu/etd/862
Copyright permissions for chapter 2 (published in the American Journal of Physiology: Gastrointestinal and Liver Physiology)
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Comments
Copyright 2024, the author