The human lens is comprised largely of crystallin proteins assembled into a highly ordered, interactive macro-structure essential for lens transparency and refractive index. Any disruption of intra- or inter-protein interactions will alter this delicate structure, exposing hydrophobic surfaces, with consequent protein aggregation and cataract formation. Cataracts are the most common cause of blindness worldwide, affecting tens of millions of people, and currently the only treatment is surgical removal of cataractous lenses. The precise mechanisms by which lens proteins both prevent aggregation and maintain lens transparency are largely unknown. Lanosterol is an amphipathic molecule enriched in the lens. It is synthesized by lanosterol synthase (LSS) in a key cyclization reaction of a cholesterol synthesis pathway. Here we identify two distinct homozygous LSS missense mutations (W581R and G588S) in two families with extensive congenital cataracts. Both of these mutations affect highly conserved amino acid residues and impair key catalytic functions of LSS. Engineered expression of wild-type, but not mutant, LSS prevents intracellular protein aggregation of various cataract-causing mutant crystallins. Treatment by lanosterol, but not cholesterol, significantly decreased preformed protein aggregates both in vitro and in cell-transfection experiments. We further show that lanosterol treatment could reduce cataract severity and increase transparency in dissected rabbit cataractous lenses in vitro and cataract severity in vivo in dogs. Our study identifies lanosterol as a key molecule in the prevention of lens protein aggregation and points to a novel strategy for cataract prevention and treatment.

Resveratrol is a cancer preventative agent that is found in red wine. Piceatannol is a closely related stilbene that has antileukaemic activity and is also a tyrosine kinase inhibitor. Piceatannol differs from resveratrol by having an additional aromatic hydroxy group. The enzyme CYP1B1 is overexpressed in a wide variety of human tumours and catalyses aromatic hydroxylation reactions. We report here that the cancer preventative agent resveratrol undergoes metabolism by the cytochrome P450 enzyme CYP1B1 to give a metabolite which has been identified as the known antileukaemic agent piceatannol. The metabolite was identified by high performance liquid chromatography analysis using fluorescence detection and the identity of the metabolite was further confirmed by derivatisation followed by gas chromatography -mass spectrometry studies using authentic piceatannol for comparison. This observation provides a novel explanation for the cancer preventative properties of resveratrol. It demonstrates that a natural dietary cancer preventative agent can be converted to a compound with known anticancer activity by an enzyme that is found in human tumours. Importantly this result gives insight into the functional role of CYP1B1 and provides evidence for the concept that CYP1B1 in tumours may be functioning as a growth suppressor enzyme.

Telomerase is a major new target for the rational design of novel anticancer agents. We have previously identified anthraquinone-based molecules capable of inhibiting telomerase by stabilizing G-quadruplex structures formed by the folding of telomeric DNA. In the present study we describe the synthesis and biological evaluation of a series of analogous fluorenone-based compounds with the specific aims of, first, determining if the anthraquinone chromophore is a prerequisite for activity and, second, whether the conventional cytotoxicity inherent to anthraquinone-based molecules may be reduced by rational design. This fluorenone series of compounds exhibits a broad range of telomerase inhibitory activity, with the most potent inhibitors displaying levels of activity (8-12 microM) comparable with other classes of G-quadruplex-interactive agents. Comparisons with analogous anthraquinone-based compounds reveal a general reduction in the level of cellular cytotoxicity. Molecular modeling techniques have been used to compare the interaction of fluorenone- and analogous anthraquinone-based inhibitors with a human G-quadruplex structure and to rationalize their observed biological activities.

A number of 1,4- and 2,6-difunctionalized amidoanthracene-9, 10-diones have been prepared. We have examined their in vitro cytotoxicity in several tumor cell lines and their ability to inhibit the telomere-addition function of the human telomerase enzyme together with their inhibition of the Taq polymerase enzyme. Compounds with -(CH2)2- side chains terminating in basic groups such as piperidine show inhibition of telomerase at telIC50 levels of 4-11 microM. These are thus among the most potent nonnucleoside telomerase inhibitors reported to date. Cytotoxicity levels in human tumor cell lines were at comparable levels for several compounds. Implications for amidoanthracene-9,10-dione telomerase inhibitors as potential anticancer agents are discussed.