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Both epidemiological and experimental findings have indicated that components of Western diets influence colonic tumorigenesis. Among dietary constituents, calcium and cholecalciferol have emerged as promising chemopreventive agents. We have demonstrated that a Western-style diet (WD) with low levels of calcium and cholecalciferol and high levels of (n-6) PUFA, increased the incidence of neoplasia in mouse intestine compared with a standard AIN-76A diet; models included wild-type mice and mice with targeted mutations, in the present study, adenomatous polyposis coli [(Apc).sup.1638N/+] mice carrying a heterozygous Apc mutation were fed either an AIN-76A diet, a WD, or a WD supplemented with calcium and cholecalciferol (WD/Ca/VitD3). Diets were fed for 24 wk and effects on cellular and molecular events were assessed by performing immunohistochemistry in colonic epithelium along the crypt-to-surface continuum. Feeding WD to [Apc.sup.1638N/+] mice not only enhanced cyclin D1 expression in colonic epithelium compared with AIN-76A treatment as previously reported but also significantly increased the expression of the antiapoptotic protein B-celllymphoma 2(Bcl-2) concomitantly with a decrease in the proapoptotic Bcl2-associated X protein and the number of apoptotic epithelial cells. WD treatment enhanced mutant Apc-driven small intestinal carcinogenesis and also resulted in the formation of a small number of colonic adenomas (0.16 [+ or -] 0.09; P < 0.05). By contrast, the WD/Ca/VitD3 diet reversed WD-induced growth, promoting changes in colonic epithelium. Importantly, [Apc.sup.1638N/+] mice fed the WD/Ca/VitD3 diet did not develop colonic tumors, further indicating that dietary calcium and cholecalciferol have a key role in the chemoprevention of colorectal neoplasia in this mouse model of human colon cancer.

The design and synthesis of vitamin D3 dimers and 1alpha,25-dihydroxyvitamin D3(calcitriol) dimers are described with a view to doubly bind the vitamin D receptor (VDR) and inducting homodimerization. By using Wittig-Horner approach to construct the vitamin D triene system and prepare the dimers with a linker of modulated length with the purpose of optimizing the vitamin D3-VDR interaction is also discussed.

A newly designed vector system which could be used to create a random mutant library with multiple integrations of DNA fragments into the Rhodococcus genome in a single step is described. The system could be applied to integrate multiple copies of expression cassettes for proline iminopeptidase and vitamin [D.sub.3] hydroxylase into the Rhodococcus genome.