PDT induced bystander effect on human xenografted colorectal tumors as evidenced by sodium MRI.

BACKGROUND: Previous in vivo studies on photodynamic therapy (PDT)-treated, high cellular density tumors showed evidences of a bystander effect accompanying the therapy, cellular death continuing beyond the limits of the photochemical reactions in time and space. This process is generated by the initially damaged cells on the light pathway. The aim of this study was to determine if the bystander effect may be induced as well in colorectal xenografted tumors (less compact structure) and if the cellular signaling depends primarily on cellular proximity or not. METHODS: The photosensitizer was a glycoconjugated, meso substituted porphyrin derivative synthesized at Institut Curie. The longitudinal follow-up of the tumors was carried out by (23)Na/(1)H MRI, ideal imaging modality for mapping the extracellular compartment. Two regimens were followed in order to target either blood vessels alone or blood vessels and cancer cells simultaneously. RESULTS: The antivascular PDT did not succeed to arrest the tumors growth at the end of the follow-up. For double targeting PDT, we managed to stop the tumoral evolution. Sodium MRI evidenced a bystander effect. CONCLUSION: The results obtained showed that the bystander effect is more difficult to induce for the type of colorectal tumors used in this work. It needs a double treatment, 4 days apart, in order to be promoted.

Synthesis of chiral ß-aminoalcohol palladium complexes exhibiting cytotoxic properties.

Original palladium complexes involving (-)-ephedrine, (-)-norephedrine, L-prolinol, L-valinol and L-isoleucinol have been rapidly prepared in neutral or basic medium and simply purified. They have been fully characterized by classical analytical methods and four of them were characterized by X-Ray analysis. In parallel with the experimental work, HF-DFT(B3LYP/PCM) computations were performed to obtain additional structural information. Their antiproliferative properties have been evaluated and some complexes showed small activities especially towards HT29 human cancer cells.

Unusual cellular uptake of cytotoxic 4-hydroxymethyl-3-aminoacridine.

Aminoacridine derivatives display interesting chemical and biological properties in the field of antitumor agents. The synthesis of 4-hydroxymethyl-3-aminoacridine and its iodo labelled analogue allows the study of cell distribution using two innovative, complementary and powerful techniques, real time fluorescence microscopy and dynamic secondary ion mass spectrometry (SIMS). All the data point to lysosomal localization of the active molecule.

Retrograde delivery of photosensitizer (TPPp-O-beta-GluOH)3 selectively potentiates its photodynamic activity.

Photodynamic therapy involves administration of a photosensitizing drug and its subsequent activation by visible light of the appropriate wavelength. Several approaches to increasing the specificity of photosensitizers for cancerous tissues and, in particular, through their conjugation to ligands that are directed against tumor-associated antigens have been investigated. Here, we have studied the delivery of the photocytotoxic porphyrin compound TPP(p-O-beta-D-GluOH)3 into tumor cells that overexpress the glycosphingolipid Gb3, using the Gb3-binding nontoxic B-subunit of Shiga toxin (STxB) as a vector. To allow for site-directed chemical coupling, an STxB variant carrying a free sulfhydryl moiety at its C-terminal end has been used. Binding affinity, cellular uptake, singlet oxygen quantum yield, and phototoxicity of the conjugate have been examined. Despite some effect of coupling on both the photophysical properties of TPP(p-O-beta-D-GluOH)3 and the affinity of STxB for its receptor, the conjugate exhibited a higher photocytotoxic activity than the photosensitizer alone and was exquisitely selective for Gb3-expressing tumor cells. Furthermore, our data strongly suggest that STxB-mediated retrograde delivery of the photosensitizer to the biosynthetic/secretory pathway is critical for optimal cytotoxic activity. In conclusion, a strong rationale for using retrograde delivery tools such as STxB in combination with photosensitizing agents for the photodynamic therapy of tumors is presented.

Amino- and glycoconjugates of pyrido[4,3,2-kl]acridine. Synthesis, antitumor activity, and DNA binding.

A series of amino- and glycoconjugates of pyrido[4,3,2-kl]acridine and pyrido[4,3,2-kl]acridin-4-one have been prepared. The most active molecules, the amino conjugates 7 and 11, display a cytostatic activity against HT-29 cancer cells at micromolar concentration. This activity correlates well with a strong DNA binding. The molecules, amino or glycoconjugates, bind DNA by intercalation, the amino or glyco substituent being located in one groove. None of the molecules inhibits topoisomerase activity.

3,4-Dihydro-1H-[1,3]oxazino[4,5-c]acridines as a new family of cytotoxic drugs.

A series of [1,3]oxazino fused acridines has been prepared as precursors of cytotoxic 3-amino-4-hydroxymethylacridine 2. Their cytotoxic activity has been evaluated against HT29 colon carcinoma cell line and was shown to be dependent on the nature of the substituent located on position 2 of the oxazine ring. Additionally, the nitrophenyl derivative 3f is activated by nitroreductase, indicating its potency as prodrug for either gene-directed or antibody-directed enzyme prodrug therapies.

Isoxazole-type derivatives related to combretastatin A-4, synthesis and biological evaluation.

Novel combretastatin analogues bearing various five-membered heterocycles with consecutive oxygen and nitrogen atoms, in place of the olefinic bridge of CA4, have been synthesized (isoxazole, isoxazoline, oxadiazole, etc). These compounds have been evaluated for cytotoxicity and their ability to inhibit the tubulin assembly. On the basis of the relative position of the aromatic A- and B-rings on the heterocyclic moiety, they could be split in two classes, the alpha,gamma- or alpha,beta-diaryl heterocyclic derivatives. In the first series, the 3,5-diaryloxadiazole 9a displayed comparable antitubulin activity to that of CA4, but was devoid of cytotoxic effects. Among the alpha,beta-diaryl heterocyclic derivatives, the 4,5-diarylisoxazole 35 exhibited greater antitubulin activity than that of CA4 (0.75 vs 1.2 microM), but modest antiproliferative activity. These data showed that minor alteration in the chemical structure of the heterocyclic ring and its relative orientation with regard to the two phenyl rings of CA4 could dramatically influence the tubulin binding properties.

Nitrobenzylcarbamate prodrugs of cytotoxic acridines for potential use with nitroreductase gene-directed enzyme prodrug therapy.

The synthesis, solvolytic behaviour and cytotoxicity of novel 4-nitrobenzyl carbamates and carbonates derived from 3-amino-4-hydroxymethylacridine 1 are described. Compounds 2 and 6 are both substrates for Escherichia coli nitroreductase and the highly active lead structure 1 is liberated upon incubation of the two compounds in the presence of NTR and its cofactor NADH. Additionally, the cytostatic activity of 2 and 6 against human HT29 colon carcinoma cell lines is decreased 80-fold and 360-fold, respectively, indicating their suitability and potency as prodrugs for either gene-directed enzyme prodrug therapy or antibody-directed enzyme prodrug therapy.

An alternative way of the synthesis of 1-substituted 9-methoxy-5-methyl-6H-pyrido[4,3-b]carbazole derivatives.

A keystone of this work was a modification of synthesis of the title compounds, which were used as substrates for the preparation of amides 5, 9-methoxyolivacine (4a) and ethyl 9-methoxy-5-methyl-6H-pyrido[4,3-b]carbazole-1-carboxylate (4b) were obtained in good overall yields (4a--72%, and 4b--31%) on alternative ways of the synthesis. The pilot results of the cytostatic activity of iminium salts 12a (IC50 = 8 microM) and 12b (IC50 = 2 microM) were determined on L1210 mouse leukaemia cells.

Cytostatic activity of 1,10-phenanthroline derivatives generated by the clip-phen strategy.

The cytostatic activities of a series of twelve 1,10-phenanthroline (Phen) derivatives and of their copper complexes were studied on L1210 murine leukemia cells. Large increases in the biological activity were observed for compounds of the 3-Clip-Phen series, in which two Phen moieties were bridged at their C3 positions by an alkoxy linker, the 3-pentyl-Clip-Phen derivative showing an IC(50) value of 130 nM while Phen shows an IC(50) value of 2500 nM under the same conditions. IC(50) values seemed to be modulated not only by the position, the nature, and the length of the linker of Clip-Phen but also by hydrophobicity. Since copper complexes of Phen are chemical nucleases and nucleic acids are thus a potential target for these compounds, the corresponding copper complexes were also studied. Copper complexation of the 3-Clip-Phen ligands did not increase their biological activities. Attempts to vectorize 3-Clip-Phen derivatives with a DNA binder such as spermine or with a cell-penetration peptide failed to increase their biological activity relative to the original 3-Clip-Phen series.

Synthesis, structure, and cytostatic properties of new olivacine derivatives.

Starting from 2-(6-methoxy-1-methyl-9H-carbazol-2-yl)ethylamine and 6-methylpicolinic acid, 9-methoxy-5-methyl-1-(6-methylpyridin-2-yl)-6H-pyrido[4,3-b]carbazole 10 and its 6-alkylderivatives 12-17 were obtained. The newly obtained compounds showed significant cytostatic activity against cultured L1210 cells and high cytotoxicity towards various human tumor cell lines.

Synthesis and cytostatic properties of some 6H-Indolo[2, 3-b][1, 8]naphthyridine derivatives.

The new and efficient synthesis of the title heterocyclic ring system is described starting from suitable 2-chloro-1, 8-naphthyridines. The synthesized 6H-indolo[2, 3-b][1, 8]naphthyridine derivatives were tested in vitro on 55 tumor cell lines for their anticancer properties. The presence of the acetylamino moiety at position 3 in the main ring system proved to be crucial for the cytostatic activity of this class of compounds.

4-Hydroxymethyl-3-aminoacridine derivatives as a new family of anticancer agents.

3-Amino- and 3-alkylamino-4-hydroxymethylacridines bearing various substituents on the C ring have been prepared by regioselective electrophilic aromatic substitution of the corresponding 3-aminoacridines and ring opening of the dihydrooxazinoacridine key intermediates. Most of the new compounds show potent cytotoxic activities against murine L1210 (leukemia), human A549 (lung), and HT29 (colon) cancer cell lines. The most cytotoxic molecules, 1 and 13, are active at nanomolar concentrations. As predicted for acridine derivatives, the new compounds intercalate in DNA, but interestingly they do not interfere with topoisomerase I and II activities. The mode of action remains uncertain because intracellular distribution indicated very different behaviors for 1 and 13. Compound 13 is uniformly distributed in the cell both in the cytoplasm and in the nucleus, whereas compound 1 is essentially localized in cytoplasmic granules.