There is significant evidence supporting the hypotheses that lifestyle, diet, and bioactive components in foods are important modifiers of cancer risk. However, our ability to assess host response noninvasively is limited. To overcome this, we have developed a technology to isolate several million viable exfoliated somatic colonic cells from a small sample of stool (0.5-1.0 g) by a procedure known as somatic cell sampling and recovery (SCSR). Orally administered carotenoids appear in these cells several days after consuming the supplement, usually showing a peak concentration between 5-7 d after their ingestion. The time lag observed for the appearance of orally administered carotenoids in SCSR cells corresponds to the turnover rate of the colonic mucosa. This is an example of how changes in cell turnover rates can be carefully assessed using the SCSR system. The specific mechanisms by which individual constituents of diet affect the cancer process are not fully understood. However, host response to dietary constituents may be investigated, noninvasively, by following the modulation of tumor-associated molecular markers in these exfoliated SCSR cells. We have demonstrated the feasibility of using SCSR cells to detect the expression of carcinoembryonic antigen, CD44, and its splice variants, c-myc, c-erbb2, and mutations in the p53 gene. In this regard, SCSR cells are a readily available surrogate cellular target that may serve to monitor changes in cell turnover, differentiation, and expression of cancer-associated biomarkers that are likely to be modulated by bioactive food components.

The possibility of using exfoliated colonic epithelial cells for assessing the bioavailability of b-carotene was examined. Analysis of exfoliated colonic epithelial cells showed the presence of b-carotene and vitamin A. The b-carotene content was significantly lower in cells from stool samples of subjects on a b-carotene-poor diet than those receiving a single dose of a b-carotene supplement. Colonic epithelial cells isolated from stool samples collected daily during a wash-out period while the subjects were on a b-carotene-poor diet showed a steady decrease in b-carotene content, reaching the lowest value on day 7. Kinetic analysis showed that a single dose of a b-carotene supplement in the form of spirulina (Spirulina platensis) or agathi (Sesbania grandiflora) after the wash-out period caused an increase in the b-carotene content after a lag period of 5 -7 d, but the vitamin A levels during these periods were not significantly affected. Analysis of plasma b-carotene concentration also showed similar changes, which correlated with those of exfoliated colonic cells. A relationship between the b-carotene content of the diet and that of the colonic epithelial cells suggests that analysis of the b-carotene content in exfoliated human colonic epithelial cells is a useful non-invasive method to assess the bioavailability of provitamin A b-carotene.Bioavailability: Vitamin A: b-Carotene: Colonic epithelial cells

The possible use of isolated exfoliated colonic epithelial cells in culture as an in vitro model to study the uptake of vitamin A and β-carotene was tested. Freshly isolated exfoliated cells maintained in culture take up β-carotene in a concentration-dependent manner. The uptake was found to increase in the presence of primary bile acids such as deoxy cholate, lipids such as triolein and lecithin in a concentration-dependent manner. These results suggest that exfoliated colonic epithelial cells isolated from stool samples of human subjects can be maintained in culture and serve as a useful non-invasive system to study the bioavailability of vitamin A and provitamin A carotenoids.

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