Chemoprevention of indirect and direct chemical carcinogenesis by carotenoids as XXXX radical quenchers.

@entity2491 @entity1 @entity20386 @entity2482 @entity2066 @entity20072 @entity19 @entity1489 @entity26 @entity5 @entity3014 @entity9627 @entity189 @entity35 @entity105 @entity356 @entity1141
@entity2066 (BC) and @entity20386 (CX), two carotenoids with and without pro-vitamin A activity, respectively, were found to help to prevent @entity3014 (BP)-induced @entity105 in the dark and BP photocarcinogenesis (UV 300-400 nm) when given as an oral supplement to female Swiss albino @entity19 . The same experimental procedure was adapted to @entity9627 ( @entity9627 ) photoinduction of mammary @entity189 in @entity19 . Here also, the two carotenoids were strongly antitumorigenic. Indeed, @entity9627 photomutagenesis, tested in @entity2491 TA 102, appeared to depend on a two-step reaction, namely an @entity26 -independent DNA- @entity9627 photoadduct, followed by an @entity26 -dependent second step, sensitive to carotenoids. This result suggests that dietary carotenoids (powerful antioxidant molecules) might prevent the carcinogenic risk caused by substances that are transformed into ultimate carcinogens by oxidative processes which are indirectly carcinogenic. Finally, to verify whether supplemental carotenoids can affect carcinogenesis where neither light excitation nor oxidative metabolic processes are involved, an experimental attempt was made on @entity356 induced in @entity35 by the direct carcinogen @entity2482 ( @entity2482 ). The results demonstrate that supplemental carotenoids do not affect initiation and progression stages, but do prevent the progression stage of @entity1141 to infiltrating @entity356 . Thus, this provides strong presumptive evidence for @entity26 radical involvement in the later stages of this neoplastic development, as recently reported in the literature. As far as mutagenicity in @entity2491 is concerned, @entity20072 do not exert, as expected, any protective effect on @entity2482 mutagenic activity. The above experimental data suggest that supplemental carotenoids, instead of sunscreen preparations, can be adopted by outdoor workers to prevent @entity1489 . Accordingly, such natural antioxidants may be useful in @entity1 chemoprevention against @entity5 of the lung, breast, urinary bladder, and colon and rectum even after radical surgery.
