Search

Resveratrol is a naturally occurring polyphenol, which causes apoptosis in cultured cancer cells. We describe a cell surface resveratrol receptor on the extracellular domain of hetero-dimeric αVβ3 integrin in MCF-7 human breast cancer cells. This receptor is linked to induction by resveratrol of extracellular-regulated kinases 1 and 2 (ERK1/2)- and serine-15-p53-dependent phosphorylation leading to apoptosis. The integrin receptor is near the Arg-Gly-Asp (RGD) recognition site on the integrin; an integrin-binding RGD peptide inhibits induction by resveratrol of ERK1/2- and p53-dependent apoptosis. Antibody (Ab) to integrin αVβ3, but not to αVβ5, inhibits activation by resveratrol of ERK1/2 and p53 and consequent apoptosis in estrogen receptor-α (ERα) positive MCF-7, and ERα-negative MDA-MB231 cells. Resveratrol is displaced from the purified integrin by an RGD, but not RGE, peptide, and by αVβ3 integrin-specific Ab. Resveratrol action is blocked by siRNAβ3, but not by siRNAαV. [14C]-Resveratrol binds to c...

The effects of cytokinins on the different branches of the indole alkaloid pathway were investigated in Catharanthus roseus cell cultures. Addition of zeatin to a 2,4-dichlorophenoxyacetic acid-containing medium decreased tryptamine levels and increased the bioconversion of secologanin to ajmalicine. Zeatin also enhanced the geraniol-10 hydroxylase activities and modified the indole alkaloid pattern. The results are discussed in the light of previous works showing that cytokinins have a positive effect on indole alkaloid accumulation in some lines of C. roseus.

Cytokinins were found to stimulate the alkaloid synthesis induced by removing auxin from the medium of a cell line of Catharanthus roseus. Diluting the mineral salts of the culture medium decreased the alkaloid production but increased the "sensitivity" of the cells. Addition of high levels of Ca(2+), Mg(2+) or Sr(2+) to B5 media in which the mineral salts were diluted to 5-40%, increased the alkaloid production. The latter effect is related only partially to enhanced osmotic potential.

Catharanthus roseus cells were cultured in three types of media. These media were: a low sucrose subculture medium and two high sucrose media, each of which differed in their mineral and hormonal contents. The kinetics of tryptophan decarboxylase activity and the accumulations of tryptophan, tryptamine, ajmalicine and serpentine were different in each series but no correlation between maximum enzyme activity and alkaloid contents was observed. Ajmalicine and serpentine productions were unaffected by addition of Trp to the media, whereas addition of secologanin enhanced alkaloid production. The results seem to imply that the terpenoid pathway is the limiting factor in alkaloid production in C. roseus cells.