Céline Bruyère

Lycorine, the main phenanthridine Amaryllidaceae alkaloid, exhibits significant antitumor activity in cancer cells that display resistance to proapoptotic stimuli: an investigation of structure-activity relationship and mechanistic insight.

Twenty-two lycorine-related compounds were investigated for in vitro antitumor activity using four cancer cell lines displaying different levels of resistance to proapoptotic stimuli and two cancer cell lines sensitive to proapoptotic stimuli. Lycorine and six of its congeners exhibited potency in the single-digit micromolar range, while no compound appeared more active than lycorine. Lycorine also displayed the highest potential (in vitro) therapeutic ratio, being at least 15 times more active against cancer than normal cells. Our studies also showed that lycorine exerts its in vitro antitumor activity through cytostatic rather than cytotoxic effects. Furthermore, lycorine provided significant therapeutic benefit in mice bearing brain grafts of the B16F10 melanoma model at nontoxic doses. Thus, the results of the current study make lycorine an excellent lead for the generation of compounds able to combat cancers, which are naturally resistant to proapoptotic stimuli, such as glioblastoma, melanoma, non-small-cell-lung cancers, and metastatic cancers, among others.

Novel Trisubstituted Harmine Derivatives with Original in Vitro Anticancer Activity

To overcome the intrinsic resistance of cancer cells to apoptotic stimuli, we designed and synthesized approximately 50 novel β-carbolines structurally related to harmine. Harmine is known for its anticancer properties and is a DYRK1A inhibitor. Of the synthesized compounds, the most active in terms of growth inhibition of five cancer cell lines are cytostatic and approximately 100 times more potent than harmine but demonstrated no DYRK1A inhibitory activity. These novel β-carbolines display similar growth inhibitory activity in cancer cells that are sensitive and resistant to apoptotic stimuli. Using ChemGPS-NP, we found that the more active β-carbolines are all more lipophilic and larger than the less active compounds. Lastly, on the basis of the NCI human tumor cell line anticancer drug screen and the NCI COMPARE algorithm, it appears that some of these compounds, including 5a and 5k, seem to act as protein synthesis inhibitors.

Targeting cyclin-dependent kinases in anti-neoplastic therapy

Cell cycle progression is controlled by sequential activation of cyclin-dependent kinases (CDKs), which are often deregulated in cancer. Consequently numerous pharmacological inhibitors of CDKs have been developed with the aim of treating cancers. The article briefly reviews CDK inhibitors and their use to treat cancers, with specific focus on the use of biomarkers and drugs combination to improve their therapeutic efficacy.

CDK/CK1 inhibitors roscovitine and CR8 downregulate amplified MYCN in neuroblastoma cells

To understand the mechanisms of action of (R)-roscovitine and (S)-CR8, two related pharmacological inhibitors of cyclin-dependent kinases (CDKs), we applied a variety of ‘-omics’ techniques to the human neuroblastoma SH-SY5Y and IMR32 cell lines: (1) kinase interaction assays, (2) affinity competition on immobilized broad-spectrum kinase inhibitors, (3) affinity chromatography on immobilized (R)-roscovitine and (S)-CR8, (4) whole genome transcriptomics analysis and specific quantitative PCR studies, (5) global quantitative proteomics approach and western blot analysis of selected proteins. Altogether, the results show that the major direct targets of these two molecules belong to the CDKs (1,2,5,7,9,12), DYRKs, CLKs and CK1s families. By inhibiting CDK7, CDK9 and CDK12, these inhibitors transiently reduce RNA polymerase 2 activity, which results in downregulation of a large set of genes. Global transcriptomics and proteomics analysis converge to a central role of MYC transcription factors downregulation. Indeed, CDK inhibitors trigger rapid and massive downregulation of MYCN expression in MYCN-amplified neuroblastoma cells as well as in nude mice xenografted IMR32 cells. Inhibition of casein kinase 1 may also contribute to the antitumoral activity of (R)-roscovitine and (S)-CR8. This dual mechanism of action may be crucial in the use of these kinase inhibitors for the treatment of MYC-dependent cancers, in particular neuroblastoma where MYCN amplification is a strong predictor factor for high-risk disease.

Investigations of fungal secondary metabolites with potential anticancer activity.

Fourteen metabolites, isolated from phytopathogenic and toxigenic fungi, were evaluated for their in vitro antigrowth activity for six distinct cancer cell lines, using the MTT colorimetric assay. Bislongiquinolide (1) and dihydrotrichodimerol (5), which belong to the bisorbicillinoid structural class, displayed significant growth inhibitory activity against the six cancer cell lines studied, while the remaining compounds displayed weak or no activity. The data show that 1 and 5 have similar growth inhibitory activities with respect to those cancer cell lines that display certain levels of resistance to pro-apoptotic stimuli or those that are sensitive to apoptosis. Quantitative videomicroscopy analysis revealed that 1 and 5 exert their antiproliferative effect through cytostatic and not cytotoxic activity. The preliminary results from the current study have stimulated further structure-activity investigations with respect to the growth inhibitory activity of compounds belonging to the bisorbicillinoid group.

Growth inhibitory activity for cancer cell lines of lapachol and its natural and semi-synthetic derivatives.

A series of 17 selected natural and semisynthetic 1,4-naphthoquinones were synthesized, and their growth inhibitory activity was evaluated in vitro. The compounds were tested on six human cancer cell lines using the MTT colorimetric assay. The data revealed that of the chemicals under study only lapachol, its acetate and 3-geranyllawsone displayed the highest activity, recording mean IC50 values ranging from 15 to 22 μM.

Secondary Metabolites from a Culture of the Fungus Neosartorya pseudofischeri and Their In Vitro Cytostatic Activity in Human Cancer Cells

Four known (1, 2, 3, and 6) and three new compounds including a 1,4-diacetyl-2,5-dibenzylpiperazine derivative (4), a quinazolinone-containing indole derivative (5), and a new ester of 2,4-dihydroxy-6-methylbenzoic acid (7) were isolated from the fungus Neosartorya pseudofischeri S. W. Peterson. Compound 2 displayed in vitro growth inhibitory activity that ranged between the activities of etoposide and carboplatin, chosen as reference compounds, in six distinct cancer cell lines. Compound 1 displayed less activity than 2. Computer-assisted phase-contrast microscopy-related analysis revealed that 2 displayed cytostatic, not cytotoxic, effects in human U373 glioblastoma and A549 non-small cell lung cancer apoptosis-resistant cells with marked inhibition of mitotic rates. Cancer cells in the remaining phases of the cell cycle were unchanged. Flow cytometry analysis further confirmed that 2 does not induce apoptotic features in U373 or A549 cancer cells. Thus, 2 represents a novel chemical scaffold from which derivatives for anticancer cytostatic compounds can be derived.

N-(2-{3-[3,5-Bis(trifluoromethyl)phenyl]ureido}ethyl)-glycyrrhetinamide (6b): A Novel Anticancer Glycyrrhetinic Acid Derivative that Targets the Proteasome and Displays Anti-Kinase Activity.

18-β-Glycyrrhetinic acid (GA; 1) and many of its derivatives are cytotoxic in cancer cells. The current study aims to characterize the anticancer effects of 17 novel 1 derivatives. On the basis of these studies, N-(2-{3-[3,5-bis(trifluoromethyl)phenyl]ureido}ethyl)-glycyrrhetinamide (6b) appeared to be the most potent compound, with IC(50)in vitro growth inhibitory concentrations in single-digit micromolarity in a panel of 8 cancer cell lines. Compound 6b is cytostatic and displays similar efficiency in apoptosis-sensitive versus apoptosis-resistant cancer cell lines through, at least partly, the inhibition of the activity of a cluster of a dozen kinases that are implicated in cancer cell proliferation and in the control of the actin cytoskeleton organization. Compound 6b also inhibits the activity of the 3 proteolytic units of the proteasome. Compound 6b thus represents an interesting hit from which future compounds could be derived to improve chemotherapeutic regimens that aim to combat cancers associated with poor prognoses.

Structure and in vitro antitumor activity evaluation of brominated diterpenes from the red alga Sphaerococcus coronopifolius

A novel bromoditerpene methyl ketone (1), two new bromoditerpene alcohols featuring a neodolastane (2), and a bromocorodienol skeleton (3), along with 13 previously reported metabolites (4-16) were isolated from the organic extract of Sphaerococcus coronopifolius collected from the rocky coasts of Corfu island in the Ionian Sea. The structures of the new natural products, as well as their relative stereochemistry, were elaborated on the basis of extensive spectral analysis, including 2D NMR experiments. The absolute stereochemistry of metabolite 3 was determined using the modified Moshers method. The isolated metabolites were evaluated for their antitumoral activity against four human apoptosis-resistant (U373, A549, SKMEL-28, OE21) and two human apoptosis-sensitive (PC-3, LoVo) cancer cell lines with IC(50) in vitro growth inhibitory concentrations in the range 3-100 microM.

Synthesis and anticancer activity evaluation of 2(4-alkoxyphenyl)cyclopropyl hydrazides and triazolo phthalazines.

A series of new 2(4-alkoxyphenyl)cyclopropyl hydrazide- and triazolo-derivatives were synthesized starting from 4-hydroxycinnamic acid (1) in a clean, mild, efficient and straightforward synthetic protocol. These compounds consisting of different alkoxy substitution, phenylcyclopropyl backbone and different heterocyclic groups were evaluated for in vitro anticancer activity against 4 cell lines displaying certain levels of resistance to pro-apoptotic stimuli and 2 cell lines sensitive to pro-apoptotic compounds. Compounds 7f and 8e were most active and displaying moderate in vitro cytostatic effect through different mechanisms. Significantly, chemically modified derivatives could be obtained in order to develop novel types of compounds aiming to combat apoptosis-resistant cancers, for example, those cancers associated with dismal prognoses.