Author ORCID Identifier
0000-0002-4367-4529
Date of Graduation
12-2023
Document Type
Thesis (MS)
Program Affiliation
Biomedical Sciences
Degree Name
Masters of Science (MS)
Advisor/Committee Chair
Eduardo Vilar-Sanchez
Committee Member
Subrata Sen
Committee Member
Jared K. Burks
Committee Member
Ann M. Killary
Committee Member
Alexandre Reuben
Committee Member
Jason A. Willis
Abstract
Mismatch Repair (MMR) is a crucial DNA repair system to maintain genomic integrity in cells that is integrated by specific genes including MLH1, MSH2, MSH6, and PMS2. These genes play a critical role in repairing errors that occur in base pairing by stabilizing the genetic material. When the MMR system fails to correct those errors, MMR deficiency occurs where monoallelic mutations in the MMR genes result in a condition known as Lynch Syndrome (LS). LS makes up approximately 3% of all colorectal cancer (CRC) and is regarded as a hereditary form of CRC, which progresses from MMR-deficient (MMRd) intestinal stem cells (ISCs). Many studies have shown that the immune system plays a critical role in influencing the genetic expression of stem cells. Our lab has also shown that naproxen, a non-steroidal anti-inflammatory drug (NSAID), has been effective at activating different subtypes of immune cells including macrophages. The purpose of this study was to understand how the immune cell compartment interacts with MMRd cells within the ISC niche. In this study, biopsied normal colorectal mucosa from MMRd patients after 6 months of exposure to naproxen was stained with stem cell and differentiation biomarkers using an in situ hybridization assay to quantify the marker density. Colon samples from MMRd mice were also collected and grown as organoids. The interactions between ISCs and the immune system were observed via changes in gene expression by culturing organoids with macrophage secretome. Mass Spectrometry was also used to identify factors in the macrophage secretome that may have contributed to the observed changes. Overall, results indicate that there is a significant increase in the quantification of stem cell biomarkers in MMRd normal mucosa after daily exposure to naproxen. There are also secreted factors present in the macrophage secretome, which are involved in the regulation of cellular proliferation and apoptosis thus validating our findings that the immune system modulates the MMRd ISC niche.
Keywords
MMR, Lynch Syndrome, Colorectal Cancer, colon, immune system, macrophage, intestinal stem cell, MMRd, LGR5