Medicinal Plants Classification Biosynthesis and ... - Index of

20
Rosa Martha Perez Gutierrez, Adriana Maria Neira Gonzalez et al.
Recently, much attention has been devoted to identifying colon cancer chemopreventive
agents of dietary origin (Surth, 1999). Moreover, β-carotene supplementation reduced the rate
of colon cell proliferation in patients with adenomatous polyps (Cahill et al., 1993).
Concomitantly, protection by β -carotene against colon cancer was shown in animal models
(Alabaster et al., 1995) as well as in cultured cells. In particular, was observed recently that
β-carotene arrested the growth of different human colon adenocarcinoma cells in a manner
strictly related to the cell's ability to accumulate the carotenoid and by a mechanism
involving both cell cycle arrest and induction of apoptosis (Iftikhar et al., 1996).
Taken together, these data raise questions about the possibility that the growth-inhibitory
and proapoptotic effects of β-carotene observed in experimental and clinical studies may
involve a reduction in the expression of COX-2. Therefore, Palozza et al., (2005) verifying
the effect of β-carotene on the growth of human colon adenocarcinoma cells overexpressing
(LS-174, HT-29, WiDr) or not expressing (HCT116) COX-2, COX-2 expression induced by
the growth factor heregulin-�, which promotes COX-2 expression through the stimulation of
HER2/HER3 receptors, and induction of apoptosis. The downregulation of COX-2 by βcarotene
occurred in both untreated and heregulin-treated cells. It was accompanied by an
increased ability of cells to undergo apoptosis and by a decrease in intracellular ROS
production and in the activation of ERK1/2. Moreover, cells not expressing COX-2 were
insensitive to the growth-inhibitory and proapoptotic effects of the carotenoid. The
suppression of COX-2 by β-carotene may represent a molecular mechanism by which this
compound acts as an antitumor agent in colon carcinogenesis.
Leung et al., (2008) examine the relationship between the lipid-soluble antioxidant
vitamins, the extent of free radical activity, tumor stage, the systemic inflammatory response
and survival in patients with colorectal cancer. In this study showed that the systemic
inflammatory response was associated with a reduction of lipid-soluble antioxidant vitamins,
whereas advanced tumor stage was associated with increased lipid peroxidation in patients
with colorectal cancer. Of the antioxidant vitamins measured, only retinol was independently
associated with cancer-specific survival.
Cervical Intraepithelial Neoplasia
Given the promise of diet and micronutrient supplementation on cancer chemoprevention
in numerous epidemiological trials, four randomized clinical trials using β-carotene as a
possible chemopreventative agent for cervical cancer have been completed to date with
mixed results (Fairleyet al., 1996).
One report presents data from a 2-year, randomized, placebo-controlled,
chemoprevention trial evaluating the effect of β-carotene in the treatment of high-grade CIN
(CIN 2 and 3). Intermediate biomarkers of cervical cancer risk, including grade of CIN
(cervical intraepithelial neoplasia) and HPV (Human papillomavirus) presence, and risk
category (high, intermediate, low, indeterminate, or none) were also evaluated. Serum and
vaginal micronutrient levels were measured to determine whether they were predictive of
lesion regression. In conclusion, cervical biopsies and the associated cell-mediated immune