Jacques Lacroix

Antiangiogenic and Antitumoral Activity of Phenyl-3-(2-Chloroethyl)Ureas A Class of Soft Alkylating Agents Disrupting Microtubules That Are Unaffected by Cell Adhesion-Mediated Drug Resistance

The development of new anticancer agents with lower toxicity, higher therapeutic index, and weaker tendency to induce resistant phenotypes in tumor cells is a continuous challenge for the scientific community. Toward that end, we showed previously that a new class of soft alkylating agents designed as phenyl-3-(2-chloroethyl)ureas (CEUs) inhibits tumor cell growth in vitro and that their efficiency is not altered by clinically relevant mechanisms of resistance such as overexpression of multidrug resistance proteins, increase in intracellular concentration of glutathione and/or glutathione S-transferase activity, alteration of topoisomerase II, and increased DNA repair. Mechanistic studies have showed recently that the cytotoxic activity of several CEUs was mainly related to the disruption of microtubules. Here, we present results supporting our assumption that 4-tert-butyl-[3-(2-chloroethyl)ureido]phenyl (tBCEU) (and its bioisosteric derivative 4-iodo-[3-(2-chloroethyl)ureido]phenyl (ICEU) are potent antimicrotubule agents both in vitro and in vivo. They covalently bind to β-tubulin, leading to a microtubule depolymerization phenotype, consequently disrupting the actin cytoskeleton and altering the nuclear morphology. Accordingly, tBCEU and ICEU also inhibited the migration and proliferation of endothelial and tumor cells in vitro in a dose-dependent manner. It is noteworthy that ICEU efficiently blocked angiogenesis and tumor growth in three distinct animal models: (a) the Matrigel plug angiogenesis assay; (b) the CT-26 tumor growth assay in mice; and (c) the chick chorioallantoic membrane tumor assay. In addition, we present evidence that CEU cytotoxicity is unaffected by additional resistance mechanisms impeding tumor response to DNA alkylating agents such as cisplatin, namely the cell adhesion mediated-drug resistance mechanism, which failed to influence the cytocidal activity of CEUs. On the basis of the apparent innocuousness of CEUs, on their ability to circumvent many classical and recently described tumor cell resistance mechanisms, and on their specific biodistribution to organs of the gastrointestinal tract, our results suggest that CEUs represent a promising new class of anticancer agents.

Design, synthesis, biological evaluation, and structure-activity relationships of substituted phenyl 4-(2-oxoimidazolidin-1-yl)benzenesulfonates as new tubulin inhibitors mimicking combretastatin A-4.

Sixty-one phenyl 4-(2-oxoimidazolidin-1-yl)benzenesulfonates (PIB-SOs) and 13 of their tetrahydro-2-oxopyrimidin-1(2H)-yl analogues (PPB-SOs) were prepared and biologically evaluated. The antiproliferative activities of PIB-SOs on 16 cancer cell lines are in the nanomolar range and unaffected in cancer cells resistant to colchicine, paclitaxel, and vinblastine or overexpressing the P-glycoprotein. None of the PPB-SOs exhibit significant antiproliferative activity. PIB-SOs block the cell cycle progression in the G2/M phase and bind to the colchicine-binding site on β-tubulin leading to cytoskeleton disruption and cell death. Chick chorioallantoic membrane tumor assays show that compounds 36, 44, and 45 efficiently block angiogenesis and tumor growth at least at similar levels as combretastatin A-4 (CA-4) and exhibit low to very low toxicity on the chick embryos. PIB-SOs were subjected to CoMFA and CoMSIA analyses to establish quantitative structure–activity relationships.

Novel imidazo[1,2-a]naphthyridinic systems (part 1) : Synthesis, antiproliferative and DNA-intercalating activities

Novel imidazo[1,2-a]naphthyridinic systems 6a-15a and 6b-15b were obtained from Friedländers reaction in imidazo[1,2-a]pyridine series. Most of the compounds were evaluated for their antitumor activity in the NCIs in vitro human tumor cell line screening panel. Among them, pentacyclic derivatives 13b and 14a exhibited in vitro activity comparable to anticancer agent such as amsacrine. Their mechanism of cytotoxicity action was unrelated to poisoning or inhibiting abilities against topo1. On the contrary, we highlighted a direct intercalation of the drugs into DNA by electrophoresis on agarose gel.

Synthesis and cytotoxic activity of new alkyl[3-(2-chloroethyl)ureido]benzene derivatives

Abstract Several alkyl[3-(2-chloroethyl)ureido] (CEU) benzene derivatives were prepared as potential anticancer agents. These new compounds were readily prepared in good yields by addition of anilines to 2-chloroethylisocyanate. Their cytotoxic activity was evaluated on human breast cancer (MDA-MB-231), human colon adenocarcinoma (LoVo) and mouse lymphocytic leukemia (P388D 1 ) tumor cell lines. Several new CEUs were significantly more cytotoxic than the nitrogen mustard chlorambucil. The biological activity of these aromatic urea derivatives seems to be related to the nature and position of the alkyl substituents on the aromatic ring. Substitution by branched alkyl groups on position 4 of the aromatic ring led to cytotoxic molecules which are up to 5 times more potent than the standard chlorambucil.

New Soft Alkylating Agents with Enhanced Cytotoxicity against Cancer Cells Resistant to Chemotherapeutics and Hypoxia

Chloroethylureas (CEU) are soft alkylating agents that covalently bind to beta-tubulin (betaTAC) and affect microtubule polymerization dynamics. Herein, we report the identification of a CEU subset and its corresponding oxazolines, which induce cell growth inhibition, apoptosis, and microtubule disruption without alkylating beta-tubulin (N-betaTAC). Both betaTAC and N-betaTAC trigger the collapse of mitochondrial potential (DeltaPsi(m)) and modulate reactive oxygen species levels, following activation of intrinsic caspase-8 and caspase-9. Experiments using human fibrosarcoma HT1080 respiratory-deficient cells (rho(0)) and uncoupler of the mitochondrial respiratory chain (MRC) showed that betaTAC and N-betaTAC impaired the MRC. rho(0) cells displayed an increased sensitivity toward N-betaTAC as compared with rho(+) cells but, in contrast, were resistant to betaTAC or classic chemotherapeutics, such as paclitaxel. Oxazoline-195 (OXA-195), an N-betaTAC derivative, triggered massive swelling of isolated mitochondria. This effect was insensitive to cyclosporin A and to Bcl-2 addition. In contrast, adenine nucleotide translocator (ANT) antagonists, bongkrekic acid or atractyloside, diminished swelling induced by OXA-195. The antiproliferative activities of the N-betaTACs CEU-025 and OXA-152 were markedly decreased in the presence of atractyloside. Conversely, pretreatment with cyclosporin A enhanced growth inhibition induced by betaTAC and N-betaTAC. One of the proteins alkylated by N-betaTAC was identified as the voltage-dependent anion channel isoform-1, an ANT partner. Our results suggest that betaTAC and N-betaTAC, despite their common ability to affect the microtubule network, trigger different cytotoxic mechanisms in cancer cells. The role of mitochondria in these mechanisms and the potential of N-betaTAC as a new therapeutic approach for targeting hypoxia-resistant cells are discussed.

Lack of cross-resistance to a new cytotoxic arylchloroethyl urea in various drug-resistant tumor cells

Abstract1-Aryl 3-(2-chloroethyl) ureas (CEUs), a new class of potent antineoplastic agents, were recently developed in our laboratory. These compounds were designed from the aromatic moiety of chlorambucil and the unnitrosated pharmacophore of carmustine. In the present study we investigated the effect of the potent CEU derivative 4-tert-butyl-[3-(2-chloroethyl)ureido] benzene (tBCEU) on tumor cell lines selected for resistance to a wide range of anticancer drugs. The resistance mechanisms found in these cells included increased expression of P-glycoprotein, increased intracellular concentration of glutathione and/or glutathione-S-transferase activity, alteration of topoisomerase II, and increased DNA repair. Whereas the resistant cell lines were found to be highly resistant to a panel of clinically known anticancer drugs, tBCEU was found to be equally cytotoxic to both resistant and parental cells. The nitrobenzylpyridine assay indicated that tBCEU is a weaker alkylating agent than chlorambucil. This lack of cross-resistance in various resistant tumor cells suggests that tBCEU could be potentially useful in the treatment of cancers resistant to conventional anticancer drugs.

Substituted phenyl 4-(2-oxoimidazolidin-1-yl)benzenesulfonamides as antimitotics. Antiproliferative, antiangiogenic and antitumoral activity, and quantitative structure-activity relationships

The importance of the bridge linking the two phenyl moieties of substituted phenyl 4-(2-oxoimidazolidin-1-yl)benzenesulfonates (PIB-SOs) was assessed using a sulfonamide group, which is a bioisostere of sulfonate and ethenyl groups. Forty one phenyl 4-(2-oxoimidazolidin-1-yl)benzenesulfonamide (PIB-SA) derivatives were prepared and biologically evaluated. PIB-SAs exhibit antiproliferative activities at the nanomolar level against sixteen cancer cell lines, block the cell cycle progression in G(2)/M phase, leading to cytoskeleton disruption and anoikis. These results were subjected to CoMFA and CoMSIA analyses to establish quantitative structure-activity relationships. These results evidence that the sulfonate and sulfonamide moieties are reciprocal bioisosteres and that phenylimidazolidin-2-one could mimic the trimethoxyphenyl moiety found in the structure of numerous potent antimicrotubule agents. Finally, compounds 16 and 17 exhibited potent antitumor and antiangiogenic activities on HT-1080 fibrosarcoma cells grafted onto chick chorioallantoic membrane similar to CA-4 without significant toxicity for the chick embryos, making this class of compounds a promising class of anticancer agents.

Synthesis and growth inhibition activity of fluorinated derivatives of tamoxifen

The design and synthesis of 11 fluorinated derivatives of tamoxifen are described. Growth inhibition values (GI50) on human HT-29, M21, MCF7, and MDA-MB-231 tumor cells are also reported. In general, the GI50 values are similar or slightly higher than tamoxifen with the most active compound on MCF7 cell line having a GI50=3.6μM. Surprisingly, as opposed to tamoxifen, both geometrical isomers behave similarly. We hypothesize that this behavior is due to in vitro isomerization of the compounds.

Synthesis, Biological Evaluation, and Structure–Activity Relationships of Novel Substituted N-Phenyl Ureidobenzenesulfonate Derivatives Blocking Cell Cycle Progression in S-Phase and Inducing DNA Double-Strand Breaks

Twenty-eight new substituted N-phenyl ureidobenzenesulfonate (PUB-SO) and 18 N-phenylureidobenzenesulfonamide (PUB-SA) derivatives were prepared. Several PUB-SOs exhibited antiproliferative activity at the micromolar level against the HT-29, M21, and MCF-7 cell lines and blocked cell cycle progression in S-phase similarly to cisplatin. In addition, PUB-SOs induced histone H2AX (γH2AX) phosphorylation, indicating that these molecules induce DNA double-strand breaks. In contrast, PUB-SAs were less active than PUB-SOs and did not block cell cycle progression in S-phase. Finally, PUB-SOs 4 and 46 exhibited potent antitumor activity in HT-1080 fibrosarcoma cells grafted onto chick chorioallantoic membranes, which was similar to cisplatin and combretastatin A-4 and without significant toxicity toward chick embryos. These new compounds are members of a promising new class of anticancer agents.

Imidazonaphthyridine systems (part 2): Functionalization of the phenyl ring linked to the pyridine pharmacophore and its replacement by a pyridinone ring produces intriguing differences in cytocidal activity.

We recently discovered that five- and pseudo-five-fused-ring derivatives in an imidazonaphthyridine series were promising hit compounds for the development of new DNA-intercalators. In this study, novel (dihydro)imidazo[1,6] and [1,7]naphthyridi(no)nes were prepared including pseudo-pentacycles. All the compounds synthesized were screened against four tumor cell lines. Compounds 3(b-d) showed significant in vitro cytotoxicity, and DNA intercalation properties were demonstrated at 25 μM. Imidazonaphthyridinones exhibited no DNA binding affinity despite significant growth inhibition activity. Interestingly, when a pyridinone pharmacophore was linked to the imidazo[1,2-a]pyridine scaffold, the geometric orientation of the link had a strong impact on the growth inhibition activity. From these results we conclude that the moderate cytotoxicity observed for these compounds is independent of their DNA-binding and topoisomerase inhibition activities.