Abstract LB220: Cellular Differentiation and Growth Control in the Human Colonic epithelium: Comparing Clinical Trial Outcomes to Responses in Human Colonoid Culture

Introduction: As part of our effort to understand the role of trace elements in colon polyp chemoprevention, we have conducted both colonoid culture (ex vivo) and human subject (in vivo) studies using Aquamin®— a calcium-, magnesium-, trace elements-rich, multi-mineral product derived from red marine algae as an intervention. Calcium alone was used as a comparator. Methods: Thirty subjects at-risk for colorectal cancer were enrolled and randomized to receive Aquamin® or calcium alone (each providing 800-mg calcium per day) or placebo. Colon biopsies were obtained before and after 90 days of intervention. We employed histologically normal colonic tissue from the same subjects (at baseline), to propagate in colonoid culture. Once established and expanded, we used the same interventions for a period of two weeks and compared the response (at 1.5mM) to the outcome of the studies conducted in human colonic biopsies after 90 days of intervention. Specifically, colonoid tissue and biopsies were subjected to analysis for markers of growth and differentiation by quantitative immunohistochemistry and tandem mass tag mass spectrometry-based proteomics. Results: The normal tissue colonoids demonstrated a high degree of differentiation as indicated by gross and microscopic appearance, and cytokeratin 20 (CK20) expression without either intervention. Only modest increases were seen in the CK20 expression with either calcium alone or Aquamin®. Similarly, CK20 expression was higher in baseline biopsies and there was no increase in the expression with calcium but a 5% increase seen with Aquamin® after 90 days of intervention. On proteomic screen, CK20 expression was increased by 40% in colonoid tissue in response to both interventions at 1.5mM, while CK20 expression increased by 10% and 21% with Calcium and Aquamin® in colon biopsies. When the colonoids were assessed for Ki67 (growth marker) expression, it was decreased by 17.2% and 18.4% with calcium alone and Aquamin® respectively as compared to the control. Analyzing colon biopsies after 90 days of intervention revealed that Aquamin® reduced the level of Ki67 expression by 20%, while no change was seen with calcium alone. Differential proteomic expression of proliferating cell nuclear antigen was decreased by 32% and 39% by calcium and Aquamin® at 1.5mM in colonoid tissue, whereas Ki67 protein was decreased by 4% and 22% with calcium and Aquamin®, respectively in colon biopsies. Conclusion: Colon tissue maintained in colonoid culture, thus, provides a good surrogate for human tissue collected in a clinical trial. It can be used to assess personalized responses or can provide a quick snapshot of the response in a relatively short time. Differential proteomic expression appears to be more sensitive than quantitative immunohistochemistry. A combination of calcium and additional trace elements proved to be more effective than calcium alone in altering differentiation and growth markers in either setting. Citation Format: Muhammad N. Aslam, Shannon McClintock, Mohamed Ali H Jawad-Makki, Karsten Knuver, Daniyal M. Nadeem, Haris Ahmad, Durga Attili, Danielle (Kim) Turgeon, James Varani. Cellular Differentiation and Growth Control in the Human Colonic epithelium: Comparing Clinical Trial Outcomes to Responses in Human Colonoid Culture [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB220.