Deleted in malignant brain tumors 1 (DMBT1) expression and impact on colonic dysplasia

PROJECT SUMMARY/ABSTRACT Bacteria-host interactions are emerging as critically important mechanisms for cancer progression but are poorly defined in precancerous colonic dysplasia. Host proteins responsible for maintaining the bacteria-resistant barrier in the colon can also function as regulators of epithelial cell differentiation and growth, such as Deleted

in Malignant Brain Tumors 1 (DMBT1). DMBT1 is a secreted glycoprotein highly expressed at epithelial barrier sites in the human gastrointestinal tract. Published data show DMBT1 is upregulated in gastric metaplasia and gastric adenocarcinoma, but the expression and mechanistic role of DMBT1 in colonic precancerous lesions

is unknown. Recent research suggests DMBT1 slows epithelial proliferation and may inhibit the development of colorectal cancer (CRC). My preliminary data show the DMBT1 gene is downregulated in distal colonic dysplasia. Our spatial transcriptomics data reveals downregulated DMBT1 expression in dysplastic foci compared with

normal colonocytes. In mouse colon tissue, I use immunofluorescence to characterize DMBT1 protein expression. The DMBT1 staining is predominantly in mid-crypt colonocytes with cytoplasmic localization and enhanced staining near the apical border. I further show DMBT1 expression in 3 different mouse models of CRC:

azoxymethane/dextran sodium sulfate, C. difficile-associated tumorigenesis in Apcmin, and Lrig1CreER/+;Apcfl/+ mice. In 100% of the dysplastic foci (n = 57 foci from 11 mice), the immunofluorescent staining of DMBT1 protein is reduced in precise correlation with upregulated β-catenin. Analysis of DMBT1 expression in human CRC

samples, including tissue microarrays containing early dysplasia, shows DMBT1 protein localization and abundance correlates with disease progression. Specifically, more advanced pathologies correlate with DMBT1 loss or secretion. Based on my preliminary data and published literature, it appears DMBT1 may function as a

tumor suppressor specifically acting in early CRC dysplasia. Previous studies show DMBT1 is transcriptionally regulated via canonical innate immune signaling pathways (e.g. NF-κB, STAT3) in infection and inflammatory bowel disease. However, the critical pathways mediating DMBT1 downregulation in colonic dysplasia are

unknown. My hypothesis is that reduced DMBT1 expression in colonic dysplasia is transcriptionally regulated and provides a selective advantage for tumorigenesis through hyperproliferation and altered cell polarity. To test this, I will determine the timeline and mechanism of DMBT1 loss using CRC mouse models

and biochemical and genetic manipulations of cellular pathways commonly dysregulated in CRC (Aim 1), and I will determine how loss of DMBT1 might be advantageous for tumor development in CRC by establishing DMBT1 knockout (DMBT1 -/- ) cells, human organoids, and a DMBT1 -/- CRC mouse model. Potentially, the loss of DMBT1

staining may aid with clinically distinguishing dysplasia from reactive changes in inflammatory bowel disease and provide a biomarker for early dysplastic transformation in human CRC.