Dr. Bray Links

Tuesday, February 21, 2017

Retinol and Cancer Prevention

High consumption of fruit and vegetables rich in carotenoids may help prevent cancer (1–4). β-Carotene, a nutrient in fruit and vegetables, can be metabolized into vitamin A, through the conversion of β-carotene into retinaldehyde by β,β-carotene 15,15′-monooxygenase (BCMO15 EC, also known as BCDO1; cloned as BCMO1). This enzyme is present in the intestine, liver, and other tissues (5–8). Retinaldehyde, the enzyme product, can be metabolized to retinol (vitamin A) or retinoic acid. One mechanism by which carotenoids exert their antitumor effects is through retinoic acid–mediated inhibition of tumor cell invasion and metastasis. Invasion of tumor cells into a new tissue requires the digestion of and migration through extracellular matrix (ECM). Matrix metalloproteinases (MMPs) digest ECM components, which allows tumors to invade and form metastases (9). Human MMPs constitute a superfamily of zinc-dependent endopeptidases classified by their structure and substrate (10, 11). MMP7 (matrilysin) has been reported to be overexpressed in 80% of colorectal cancers; it may be important in early tumor growth and in invasion and metastasis (12–16). MMP28 (epilysin) expression is increased in some tumors and cancer cell lines (17, 18). 


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