Colonie Epithelial Cell Proliferation in Responders and Nonresponders to Supplemental Dietary Calcium1

Supplemental dietary calcium decreased and normalized hyperproliferation of colonie epithelial cells in individuals in familial colon cancer kindreds, measured by rates and patterns of (3H]thymidine labeling of epithelial cells in colonie crypts. In whole colonie crypts hyperproliferation was decreased to lower levels in over one-half of the subjects individually studied during the course of the calcium supplementation regimen. The remaining familial colon cancer subjects did not showreductions in cell proliferation measured over the whole crypt. However, when their cell-labeling data were analyzed in regions of the colonie crypt, the size of the proliferate compartment decreased and contracted towards the crypt base after calcium, a pattern typical of individuals at decreased risk for colonie cancer. This contraction of the proliferative region of the crypts occurred through decreased cell labeling in the two crypt compartments closest to the luminal surface and increased cell labeling in the second crypt compartment nearest to the base of the crypt. Following in vitro exposure of colonie epithelial cells to increasing physiological amounts of calcium, cell proliferation in familial colon cancer subjects decreased uniformly and greater heterogeneity in respon siveness was observed in cells from individuals with familial polyposis.