Metallocene-based inhibitors of cancer-associated carbonic anhydrase enzymes IX and XII.

In this study, 20 metallocene-based compounds comprising extensive structural diversity were synthesized and evaluated as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. These compounds proved moderate to good CA inhibitors in vitro, with several compounds displaying selectivity for cancer-associated isozymes CA IX and CA XII compared to off-target CA I and CA II. Compound 6 was the most potent ferrocene-based inhibitor with K(i)s of 5.9 and 6.8 nM at CA IX and XII, respectively. A selection of key drug-like parameters comprising Log P, Log D, solubility, and in vitro metabolic stability and permeability were measured for two of the ferrocene-based compounds, regioisomers 1 and 5. Compounds 1 and 5 were found to have characteristics consistent with lipophilic compounds, however, our findings show that the lipophilicity of the ferrocene moiety is not well modeled by replacement with either a naphthyl or a phenyl moiety in software prediction tools.

Novel orally active antimalarial thiazoles.

An aminomethylthiazole pyrazole carboxamide lead 3 with good in vitro antiplasmodial activity [IC(50): 0.08 µM (K1, chloroquine and multidrug resistant strain) and 0.07 µM (NF54, chloroquine sensitive strain)] and microsomal metabolic stability was identified from whole cell screening of a SoftFocus kinase library. Compound 3 also exhibited in vivo activity in the P. berghei mouse model at 4 × 50 mg/kg administration via the oral route, showing 99.5% activity and 9 days survival and showed low in vitro cytotoxicity. Pharmacokinetic studies in rats revealed good oral bioavailability (51% at 22 mg/kg) with a moderate rate of absorption, reasonable half-life (t(1/2) 3 h), and high volume of distribution with moderately high plasma and blood clearance after IV administration. Toward toxicity profiling, 3 exhibited moderate potential to inhibit CYP1A2 (IC(50) = 1.5 µM) and 2D6 (IC(50) = 0.4 µM) as well as having a potential hERG liability (IC(50) = 3.7 µM).

Salvianolic acid B modulates the expression of drug-metabolizing enzymes in HepG2 cells.

BACKGROUND: Enzymes involved in drug and xenobiotic metabolism have been considered to exist in two groups: phase I and phase II enzymes. Cytochrome P450 isoenzymes (CYPs) are the most important phase I enzymes in the metabolism of xenobiotics. The products of phase I metabolism are then acted upon by phase II enzymes, including glutathione S-transferases (GSTs). Herbs that inhibit CYPs such as CYP3A4 or that induce GSTs may have the potential to protect against chemical carcinogenesis since the mutagenic effects of carcinogens are often mediated through an excess of CYP-generated reactive intermediates. This study was designed to investigate the effects of salvianolic acid B (Sal B), a pure compound extracted from Radix Salviae Miltiorrhizae, a Chinese herb, on cell proliferation and CYP1A2 and CYP3A4 mRNA expression in the presence or absence of rifampicin, a potent inducer of CYPs and GST protein expression in HepG2 cells. METHODS: HepG2 cells were incubated with different concentrations of Sal B. Cell proliferation was determined by SYTOX-Green nucleic acid staining. CYP3A4 and CYP1A2 mRNA expression was assayed by real-time PCR. GST protein expression was analyzed by Western blotting. RESULTS: Low concentrations of Sal B (0-20 µmol/L) had no significant effects on cell proliferation, while higher concentrations (100-250 µmol/L) significantly inhibited proliferation in a concentration-dependent manner. Ten µmol/L Sal B, but not 1 µmol/L, down-regulated CYP3A4 and CYP1A2 mRNA expression after 24 hours of incubation, whereas both 1 and 10 µmol/L Sal B down-regulated CYP3A4 mRNA expression after 96 hours of incubation; moreover, 1 and 10 µmol/L Sal B inhibited CYP3A4 mRNA expression induced by rifampicin. Both 1 µmol/L and 10 µmol/L Sal B increased GST expression. CONCLUSION: Sal B inhibits CYP3A4 and CYP1A2 mRNA expression and induces GST expression in HepG2 cells.

S-glycosyl primary sulfonamides--a new structural class for selective inhibition of cancer-associated carbonic anhydrases.

In this paper, we present a new class of carbonic anhydrase (CA) inhibitor that was designed to selectively target the extracellular domains of the cancer-relevant CA isozymes. The aromatic moiety of the classical zinc binding sulfonamide CA inhibitors is absent from these compounds and instead they incorporate a hydrophilic mono- or disaccharide fragment directly attached to the sulfonamide group to give S-glycosyl primary sulfonamides (1-10). The inhibition properties of these compounds at the physiologically abundant human CA isozymes I and II and cancer-associated IX and XII were determined, and all compounds had moderate potency with K(i)s in the micromolar range. We present the crystal structures of anomeric sulfonamides 4, 7, and 10 and the sugar sulfamate drug topiramate in complex with human recombinant CA II. From these structures, we have obtained valuable insights into ligand-protein interactions of these novel carbohydrate-based sulfonamides with CA.

Berry phenolic extracts modulate the expression of p21(WAF1) and Bax but not Bcl-2 in HT-29 colon cancer cells.

Previous studies have shown that anthocyanin-rich berry extracts inhibit the growth of cancer cells in vitro. The objective of this study was to compare the effects of berry extracts containing different phenolic profiles on cell viability and expression of markers of cell proliferation and apoptosis in human colon cancer HT-29 cells. Berry extracts were prepared with methanol extraction, and contents of the main phenolic compounds were analyzed using HPLC. Anthocyanins were the predominant phenolic compounds in bilberry, black currant, and lingonberry extracts and ellagitannins in cloudberry extract, whereas both were present in raspberry and strawberry extracts. Cells were exposed to 0-60 mg/mL of extracts, and the cell growth inhibition was determined after 24 h. The degree of cell growth inhibition was as follows: bilberry > black currant > cloudberry > lingonberry > raspberry > strawberry. A 14-fold increase in the expression of p21WAF1, an inhibitor of cell proliferation and a member of the cyclin kinase inhibitors, was seen in cells exposed to cloudberry extract compared to other berry treatments (2.7-7-fold increase). The pro-apoptosis marker, Bax, was increased 1.3-fold only in cloudberry- and bilberry-treated cells, whereas the pro-survival marker, Bcl-2, was detected only in control cells. The results demonstrate that berry extracts inhibit cancer cell proliferation mainly via the p21WAF1 pathway. Cloudberry, despite its very low anthocyanin content, was a potent inhibitor of cell proliferation. Therefore, it is concluded that, in addition to anthocyanins, also other phenolic or nonphenolic phytochemicals are responsible for the antiproliferative activity of berries.