Synthesis And Anticancer Activity Of New Hybrid 3-Methylidene-2,3-Dihydro-1,8-Naphthyridinones.

Synthesis of molecular hybrids, obtained by combination of two or more pharmacophoric groups of different bioactive substances in order to produce more efficient drugs, is now a frequently used approach in medicinal chemistry. Following this strategy, we synthetized a library of 3-methylidene-1-tosyl-2,3-dihydro-1,8-naphthyridin-4(1H)-ones, combining a 1,8-naphthyridin-4-one motif with an exo-methylidene bond conjugated with a carbonyl group, pharmacophoric units that are present in many natural, biologically active compounds with anticancer potential. We reasoned that such bifunctional conjugates may have enhanced cytotoxic activity. The title compounds were synthesized in a four step reaction sequence. ß-Ketophosphonate, obtained from methyl N-tosylnicotinate and diethyl methylphosphonate, was reacted with various aldehydes giving 3-diethoxyphosphoryl-2,3-dihydro-1,8-naphthyridin-4(1H)-ones as keto-enol tautomers. Later, these compounds were transformed into 3-methylidene-1-tosyl-2,3-dihydro-1,8-naphthyridin-4(1H)-ones applying the Horner-Wadsworth-Emmons methodology. Then, the cytotoxicity of the new compounds was assessed on two cancer cell lines, promyelocytic leukemia HL-60 and breast cancer adenocarcinoma MCF-7, and for comparison, on human umbilical vein endothelial cells HUVEC. The most active and selective analog, 2-ethyl-3-methylidene-1-tosyl-2,3-dihydro-1,8-naphthyridin-4(1H)-one 4 a was chosen for more detailed studies on HL-60 cell line, to determine molecular mechanisms of its anticancer activity. It was shown that 4 a strongly inhibited proliferation and induced apoptosis which could be attributed to its ability to cause DNA damage.

Trifluoromethylated 4,5-Dihydro-1,2,4-triazin-6(1H)-ones via (3+3)-Annulation of Nitrile Imines with α-Amino Esters.

The synthesis of two series of monocyclic and bicyclic trifluoromethylated 4,5-dihydro-1,2,4-triazin-6(1H)-one derivatives based on (3+3)-annulation of methyl esters derived from natural α-amino acids with in situ generated trifluoroacetonitrile imines has been described. The devised protocol is characterized by a wide scope, easily accessible substrates, remarkable functional group tolerance, and high chemical yield. In reactions with chiral starting materials, no racemization at the stereogenic centers was observed and the respective enantiomerically pure products were obtained. Selected functional group interconversions carried out under catalytic hydrogenation and mild PTC oxidation conditions were also demonstrated.

Synthesis and Anticancer Properties of New 3-Methylidene-1-sulfonyl-2,3-dihydroquinolin-4(1H)-ones.

Quinolinones have been known for a long time as broad-spectrum synthetic antibiotics. More recently, the anticancer potential of this group of compounds has been investigated. Following this direction, we obtained a small library of 3-methylidene-1-sulfonyl-2,3-dihydroquinolin-4(1H)-ones with various substituents at positions 1, 2, 6, and 7 of the quinolinone ring system. The cytotoxic activity of the synthesized analogs was tested in the MTT assay on two cancer cell lines in order to determine the structure-activity relationship. All compounds produced high cytotoxic effects in MCF-7, and even higher in HL-60 cells. 2-Ethyl-3-methylidene-1-phenylsulfonyl-2,3-dihydroquinolin-4(1H)-one, which was over 5-fold more cytotoxic for HL-60 than for normal HUVEC cells, was selected for further tests. This analog was shown to inhibit proliferation and induce DNA damage and apoptosis in HL-60 cells.

Thapsigargin-From Traditional Medicine to Anticancer Drug.

A sesquiterpene lactone, thapsigargin, is a phytochemical found in the roots and fruits of Mediterranean plants from Thapsia L. species that have been used for centuries in folk medicine to treat rheumatic pain, lung diseases, and female infertility. More recently thapsigargin was found to be a potent cytotoxin that induces apoptosis by inhibiting the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) pump, which is necessary for cellular viability. This biological activity encouraged studies on the use of thapsigargin as a novel antineoplastic agent, which were, however, hampered due to high toxicity of this compound to normal cells. In this review, we summarized the recent knowledge on the biological activity and molecular mechanisms of thapsigargin action and advances in the synthesis of less-toxic thapsigargin derivatives that are being developed as novel anticancer drugs.

Molecular mechanisms of apoptosis induced by a novel synthetic quinolinone derivative in HL-60 human leukemia cells.

The mortality rates for acute myeloid leukemia are very high, necessitating the search for novel chemotherapeutic candidates. Herein, we investigated the anticancer potential of a new synthetic compound, 2-ethyl-3-methyliden-1-tosyl-2,3-dihydroquinolin-4-(1H)-one (AJ-374) against myeloid leukemia HL-60 cell line. This analog was selected from the small library of synthetic dihydroquinolinones on the basis of its strong antiproliferative activity against HL-60 cells and 30-fold lower cytotoxicity towards healthy HUVEC cells. AJ-374 promoted the arrest of the cells in the subG0/G1 phase of the cell cycle in the first 24 h. Treatment of HL-60 cells with AJ-374 caused an increase in annexin-V positive cells, activation of caspase-8, -9 and -3, dissipation of the mitochondrial membrane potential and enhancement of FAS protein level. Apoptosis induction triggered by this quinolinone was blocked by the pre-treatment of the cells with caspase-8, -9 and -3 inhibitors. The obtained results indicated that AJ-374-induced apoptosis was executed by both, the extrinsic and intrinsic pathways. The cytotoxic activity of AJ-374 was also associated with down-regulation of the mitogen-activated protein kinase (MAPK) pathway and was independent of reactive oxygen species generation. Taken together, these results suggest that AJ-374 exerts a potent anticancer effect on leukemia cells, with a wide safety margin, which makes this analog an attractive drug candidate for further testing.

Rearrangements within the U6 snRNA Core during the Transition between the Two Catalytic Steps of Splicing.

The RNA catalytic core of spliceosomes as visualized by cryoelectron microscopy (cryo-EM) remains unchanged at different stages of splicing. However, we demonstrate that mutations within the core of yeast U6 snRNA modulate conformational changes between the two catalytic steps. We propose that the intramolecular stem-loop (ISL) of U6 exists in two competing states, changing between a default, non-catalytic conformation and a transient, catalytic conformation. Whereas stable interactions in the catalytic triplex promote catalysis and their disruptions favor exit from the catalytic conformation, destabilization of the lower ISL stem promotes catalysis and its stabilization supports exit from the catalytic conformation. Thus, in addition to the catalytic triplex, U6-ISL acts as an important dynamic component of the catalytic center. The relative flexibility of the lower U6-ISL stem is conserved across eukaryotes. Similar features are found in U6atac and domain V of group II introns, arguing for the generality of the proposed mechanism.