Second-generation testosterone-platinum(II) hybrids for site-specific treatment of androgen receptor positive prostate cancer: Design, synthesis and antiproliferative activity.

Prostate cancer is the most diagnosed type of cancer in men in Canada. One out of eight men will be stricken with this disease during the course of his life. It is noteworthy that, at initial diagnoses 80-90% of cancers are androgen dependent. Hence, the androgen receptor is a viable biological target to be considered for drug targeting. We have developed a new generation of testosterone-Pt(II) hybrids for site-specific treatment of hormone-dependent prostate cancer. The hybrid molecules are made from testosterone using an eight-step reaction sequence with about 7% overall yield. They are linked with a stronger tether chain between the testosterone moiety and the Pt(II) moiety in comparison to our first generation hybrids. The new hybrids were tested on hormone-dependent and -independent prostate cancer cell lines. The hybrid 3a presents the best antiproliferative activity and was selective on hormone-dependent prostate cancer with IC50 of 2.2 µM on LNCaP (AR+) in comparison to 13.3 µM on PC3 (AR-) and 8.8 µM on DU145 (AR-) prostate cancer cells. On the same cell lines, CDDP displayed IC50 of 2.1 µM, 0.5 µM and 1.0 µM, respectively. Remarkably, hybrid 3a was inactive on both colon carcinoma (HT-29) and normal human adult keratinocyte cells (HaCat) with an IC50 of >25 µM. This is not the case for CDDP showing IC50 of 1.3 µM and 5.1 µM on HT-29 and HaCat cells, respectively. The potential for selective activity on androgen-receptor positive prostate cancer cells is confirmed with hybrid 3a giving new hope for an efficient and less toxic platinum-based treatment of prostate cancer patients.

Inactivation of the mTORC1-eukaryotic translation initiation factor 4E pathway alters stress granule formation.

Stress granules (SG) are cytoplasmic multimeric RNA bodies that form under stress conditions known to inhibit cap-dependent translation. SG contain translation initiation factors, RNA binding proteins, and signaling molecules. SG are known to inhibit apoptotic pathways, thus contributing to chemo- and radioresistance in tumor cells. However, whether stress granule formation involves oncogenic signaling pathways is currently unknown. Here, we report a novel role of the mTORC1-eukaryotic translation initiation factor 4E (eIF4E) pathway, a key regulator of cap-dependent translation initiation of oncogenic factors, in SG formation. mTORC1 specifically drives the eIF4E-mediated formation of SG through the phosphorylation of 4E-BP1, a key factor known to inhibit formation of the mTORC1-dependent eIF4E-eIF4GI interactions. Disrupting formation of SG by inactivation of mTOR with its specific inhibitor pp242 or by depletion of eIF4E or eIF4GI blocks the SG-associated antiapoptotic p21 pathway. Finally, pp242 sensitizes cancer cells to death in vitro and inhibits the growth of chemoresistant tumors in vivo. This work therefore highlights a novel role of the oncogenic mTORC1-eIF4E pathway, namely, the promotion of formation of antiapoptotic SG.

Inhibitory effects of cytoskeleton disrupting drugs and GDP-locked Rab mutants on bradykinin B2 receptor cycling.

The bradykinin (BK) B2 receptor (B2R) is G protein coupled and phosphorylated upon agonist stimulation; its endocytosis and recycling are documented. We assessed the effect of drugs that affect the cytoskeleton on B2R cycling. These drugs were targeted to tubulin (paclitaxel, or the novel combretastatin A-4 mimetic 3,4,5-trimethoxyphenyl-4-(2-oxoimidazolidin-1-yl)benzenesulfonate [IMZ-602]) and actin (cytochalasin D). Tubulin ligands did not alter agonist-induced receptor endocytosis, as shown using antibodies reactive with myc-tagged B2Rs (microscopy, cytofluorometry), but rather reduced the progression of the ligand-receptor-ß-arrestin complex from the cell periphery to the interior. The 3 fluorescent probes of this complex (B2R-green fluorescent protein [B2R-GFP], the fluorescent agonist fluorescein-5-thiocarbamoyl-D-Arg-[Hyp³, Igl5, Oic7, Igl8]-BK and ß-arrestin2-GFP) were condensed in punctuate structures that remained close to the cell surface in the presence of IMZ-602. Cytochalasin D selectively inhibited the recycling of endocytosed B2R-GFP (B2R-GFP imaging, [³H]BK binding). Dominant negative (GDP-locked)-Rab5 and -Rab11 reproduced the effects of inhibitors of tubulin and actin, respectively, on the cycling of B2R-GFP. GDP-locked-Rab4 also inhibited B2R-GFP recycling to the cell surface. Consistent with the displacement of cargo along specific cytoskeletal elements, Rab5-associated progression of the endocytosed BK B2R follows microtubules toward their (-) end, while its recycling progresses along actin fibers to the cell surface. However, tubulin ligands do not suppress the tested desensitization or resensitization mechanisms of the B2R.

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.

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.

Cation trapping by cellular acidic compartments: beyond the concept of lysosomotropic drugs.

"Lysosomotropic" cationic drugs are known to concentrate in acidic cell compartments due to low retro-diffusion of the protonated molecule (ion trapping); they draw water by an osmotic mechanism, leading to a vacuolar response. Several aspects of this phenomenon were recently reexamined. (1) The proton pump vacuolar (V)-ATPase is the driving force of cationic drug uptake and ensuing vacuolization. In quantitative transport experiments, V-ATPase inhibitors, such as bafilomycin A1, greatly reduced the uptake of cationic drugs and released them in preloaded cells. (2) Pigmented or fluorescent amines are effectively present in a concentrated form in the large vacuoles. (3) Consistent with V-ATPase expression in trans-Golgi, lysosomes and endosomes, a fraction of the vacuoles is consistently labeled with trans-Golgi markers and protein secretion and endocytosis are often inhibited in vacuolar cells. (4) Macroautophagic signaling (accumulation of lipidated and membrane-bound LC3 II) and labeling of the large vacuoles by the autophagy effector LC3 were consistently observed in cells, precisely at incubation periods and amine concentrations that cause vacuolization. Vacuoles also exhibit late endosome/lysosome markers, because they may originate from such organelles or because macroautophagosomes fuse with lysosomes. Autophagosome persistence is likely due to the lack of resolution of autophagy, rather than to nutritional deprivation. (5) Increased lipophilicity decreases the threshold concentration for the vacuolar and autophagic cytopathology, because simple diffusion into cells is limiting. (6) A still unexplained mitotic arrest is consistently observed in cells loaded with amines. An extended recognition of relevant clinical situations is proposed for local or systemic drug administration.

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.

N-4-iodophenyl-N'-2-chloroethylurea, a novel potential anticancer agent with colon-specific accumulation: radioiodination and comparative in vivo biodistribution profiles.

In a search for more selective anticancer drugs, we have designed nitrogen mustard and nitrosourea conjugates leading to a series of N-4-aryl-N'-2-chloroethylureas (CEUs). The iodinated derivative N-4-iodophenyl-N'-2-chloroethylurea (4-ICEU) has demonstrated significant antineoplastic and antiangiogenic potency in preclinical evaluations. In this study, 4-ICEU was radiolabelled with [(125)I]iodide in order to carry out a comparative study of its in vivo behavior profile. 4-[(125)I]-ICEU was synthesized by direct electrophilic radioiodination with 80% radiochemical yield and 97% radiopurity. Three different routes of administration (intraperitoneal (ip), intravenous (iv) and intratumoral (it)) were tested in mice bearing subcutaneously implanted CT-26 murine colon carcinoma. The results clearly established that 4-ICEU was more stable to biotransformation than previously studied CEUs congeners. It was readily bioavailable and reached the CT-26 colorectal tumor regardless of the route of administration. Additionally, the colon mucosa was an important target tissue where 4-ICEU accumulated and remained largely untransformed. In conclusion, these results justify further investigations for developing 4-ICEU as a new chemotherapeutic agent for colorectal cancer.

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 Friedländer's 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.

In vitro activity of novel dual action MDR anthranilamide modulators with inhibitory activity on CYP-450 (Part 2).

Synthesis and in vitro cytotoxicity assays of new anthranilamide MDR modulators have been performed to assess their inhibition potency on the P-glycoprotein (P-gp) transporter. Previous studies showed that the replacement of the aromatic spacer group between nitrogen atoms (N(1) and N(2)) in the P-gp inhibitor XR9576 with ethyl or propyl chain is optimal for P-gp inhibition potency. To confirm that observation, the ethyl or the propyl linker arm was replaced with a pyrrolidine or an alicyclic group such as cyclohexyl. In addition, an arylpiperazinyl group and two methoxyl groups onto the anthranilic part were introduced to assess their effect on the anti P-gp activity. Five molecules were prepared and evaluated on CEM/VLB500. All new anthranilamides were more potent than verapamil, most of them exhibited a lower cytotoxicity than XR9576. Compound 5 was the most potent and its inhibition activity was similar to XR9576. Interestingly, in vitro biotransformation studies of compounds 4 and 5 using human CYP-450 isoforms revealed, that conversely to XR9576, compounds 4 and 5 inhibited CYP3A4, an enzyme that colocalizes with P-gp in the intestine and contributes to tumor cell chemoresistance by enhancing the biodisposition of numerous drugs, notably paclitaxel. In that context, 5 might be suitable for further drug development.

A comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) of anthranilamide derivatives that are multidrug resistance modulators.

In a continuing effort to develop potent and selective modulators of P-glycoprotein (P-gp) activity overcoming the chemoresistance acquired by tumor cells during cancer chemotherapy, we developed 3D quantitative structure-activity relationship (3D QSAR) models using CoMFA and CoMSIA analyses. This study correlates the P-glycoprotein inhibitory activities of 49 structurally related anthranilamide derivatives to several physicochemical parameters representing steric, electrostatic, acceptor, donor, and hydrophobic fields. Both CoMFA and CoMSIA models using three different alignment conformations gave good internal predictions, and their cross-validated r2 values are between 0.503 and 0.644. These most comprehensive CoMFA and CoMSIA models are useful in understanding the structure-activity relationships of anthranilamide derivatives as well as aid in the design of novel derivatives with enhanced modulation of P-gp activity.

Synthesis of unique 17beta-estradiol homo-dimers, estrogen receptors binding affinity evaluation and cytocidal activity on breast, intestinal and skin cancer cell lines.

A rapid and efficient synthesis of a series of C2-symmetric 17beta-estradiol homo-dimers is described. The new molecules are linked at position 17alpha of the steroid nucleus with either an alkyl chain or a polyethylene glycol chain. They are made from estrone in only five chemical steps with an overall yield exceeding 30%. The biological activity of these compounds was evaluated in vitro on estrogen dependent and independent (ER+ and ER-) human breast tumor cell lines: MCF-7 and MDA-MB-231. Some of the dimers present selective cytotoxic activity against the ER+ cell line. However, they are not very cytotoxic when compared to the antiestrogen tamoxifen. Unfortunately, they show only weak affinity for the estrogen receptor alpha (ERalpha) and no affinity for the estrogen receptor beta (ERbeta). The new compounds were also tested on human intestinal (HT-29) cancer and on murine skin cancer (B16-F10) cell lines for further biological assessment. Interestingly, the dimers were found to be cytotoxic to the murine skin cancer cell line but were inactive towards the intestinal cancer cell line.

In vitro activity of novel dual action MDR anthranilamide modulators with inhibitory activity at CYP-450.

Synthesis and in vitro cytotoxicity assays of new anthranilamide MDR modulators have been performed to assess their inhibition potency of the P-glycoprotein (P-gp) transporter. The aromatic spacer group between nitrogen atoms (N1 and N2) in the known inhibitor XR9576 was replaced with a flexible alkyl chain of 2 to 6 carbon atoms in length. 6,7-Dimethoxy-1,2,3,4-tetrahydroisoquinoline and their open-chain N-methylhomoveratrylamine counterparts were shown to be potent P-gp inhibitors. The maximal inhibition was obtained when using an ethyl or propyl spacer. Several compounds were more potent than verapamil and intrinsically less cytotoxic than XR9576. In addition, in vitro metabolism studies of 23a with a subset of human CYP-450 isoforms revealed that, unlike XR9576, 23a inhibited CYP3A4, an enzyme that colocalizes with P-gp in the intestine and contributes to tumor cell chemoresistance by enhancing the biodisposition of anticancer drugs such as paclitaxel toward metabolism. In this context, 22a might be a suitable candidate for further drug development.

Alkylation of beta-tubulin on Glu 198 by a microtubule disrupter.

We have shown that beta-tubulin was alkylated by a microtubule disrupter, N-4-iodophenyl-N'-(2-chloroethyl)urea (ICEU), on a glutamic acid residue at position 198 and not on the previously proposed reactive cysteine 239. ICEU belongs to the 4-substituted-phenyl-N'-(2-chloroethyl) urea class that alkylates mainly cellular proteins. Previous studies have shown that the tert-butyl (tBCEU) and iodo (ICEU) derivatives induce microtubule disruption because of beta-tubulin alkylation. tBCEU was supposed to bind covalently to cysteine 239 of beta-tubulin, but this binding site was not clearly confirmed (Cancer Res 60:985-992, 2000). We have isolated and analyzed beta-tubulin after two-dimensional gel electrophoresis of proteins from B16 cells incubated with ICEU. Alkylated beta-tubulin had a lower apparent molecular weight and a more basic isoelectric point than the unmodified protein. Labeled N-4-[125I]CEU was effectively bound to the modified beta-tubulin but using matrix-assisted laser desorption ionization/time-of-flight mass spectrometry, we demonstrated that none of the cysteine residues of beta-tubulin was linked to the alkylating agent. In contrast, peptide masses at m/z 4883 and 1792 in trypsin or Asp-N digestions of beta-tubulin confirmed binding of iodophenylethylureido moiety to peptides [175-213] or [197-208] respectively. Fragmentation analyses by electrospray mass spectrometry using triply charged ions of peptide [175-213] identified a glutamic acid at position 198 as target for alkylation via an ester bond with ICEU. This amino acid located in the intermediate domain of the beta-tubulin should play an essential role in the conformational structure necessary for the interaction between dimers in the protofilament.

Engineering surfaces for bioconjugation: developing strategies and quantifying the extent of the reactions.

This study presents two-step and multistep reactions for modifying the surface of plasma-functionalized poly(tetrafluoroethylene) (PTFE) surfaces for subsequent conjugation of biologically relevant molecules. First, PTFE films were treated by a radiofrequency glow discharge (RFGD) ammonia plasma to introduce amino groups on the fluoropolymer surface. This plasma treatment is well optimized and allows the incorporation of a relative surface concentration of approximately 2-3.5% of amino groups, as assessed by chemical derivatization followed by X-ray photoelectron spectroscopy (XPS). In a second step, these amino groups were further reacted with various chemical reagents to provide the surface with chemical functionalities such as maleimides, carboxylic acids, acetals, aldehydes, and thiols, that could be used later on to conjugate a wide variety of biologically relevant molecules such as proteins, DNA, drugs, etc. In the present study, glutaric and cis-aconitic anhydrides were evaluated for their capability to provide carboxylic functions to the PTFE plasma-treated surface. Bromoacetaldehyde diethylacetal was reacted with the aminated PTFE surface, providing a diethylacetal function, which is a latent form of aldehyde functionality. Reactions with cross-linkers such as sulfo-succinimidyl derivatives (sulfo-SMCC, sulfo-SMPB) were evaluated to provide a highly reactive maleimide function suitable for further chemical reactions with thiolated molecules. Traut reagent (2-iminothiolane) was also conjugated to introduce a thiol group onto the fluoropolymer surface. PTFE-modified surfaces were analyzed by XPS with a particular attention to quantify the extent of the reactions that occurred on the polymer. Finally, surface immobilization of fibronectin performed using either glutaric anhydride or sulfo-SMPB activators demonstrated the importance of selecting the appropriate conjugation strategy to retain the protein biological activity.

Antineoplastic potency of arylchloroethylurea derivatives in murine colon carcinoma.

In a search for new antineoplastic agents the lead compound N-(4-tert-butylphenyl)-N'-(2-chloroethyl)urea (CEU-22) of a series of 1-aryl-3-(2-chloroethyl)ureas and its iodinated bioisostere CEU-98, were previously selected on the basis of their cytotoxicity and the potent tropism for the intestinal tract (evidenced for CEU-22). In this study, we investigated the antitumour profile of these two drugs for the indication of colon cancer. In vitro, we found that micromolar concentrations of both CEU-22 and CEU-98 inhibited proliferation of DLD-1, Caco-2, HT-29, SW-948 and CT-26 lines. In vivo, a high inhibition of tumour growth and a life span increase were observed when BALB/c mice grafted subcutaneously with CT-26 cells received 5 daily intratumoural injections of each drug. When administered by the intraperitoneal route according to an intermittent schedule starting Day 1 or Day 7 post-implant, only CEU-98 demonstrated antitumour activity ( T / C = 29% for the Day-1,5,9-treatment versus 40% for the Day-7,11,15-treatment) and a life span increase around 40% for the two protocols. These results make CEU-98 a candidate for further investigations with a view to developing an efficacious treatment of colorectal cancer.

Spectroscopic characterization of nanoErythrosomes in the absence and presence of conjugated polyethyleneglycols: an FTIR and (31)P-NMR study.

We have recently developed from red blood cells a new delivery system called nanoErythrosomes. These nanovesicles offer a high degree of versatility for the encapsulation of biological or nonbiological compounds and for the binding of targeting agents. In particular, polyethyleneglycols can be conjugated by a covalent link to the basic amino acid residues constitutive of the different proteins. The binding of polyethyleneglycols to the nanoErythrosome membrane could be interesting for the therapeutic use of this delivery system since it could overcome heterologous immunogenicity and reduce rapid clearance from circulation. In the present study, we have investigated the effect of temperature on the nanoErythrosome behavior in the absence and presence of conjugated polyethyleneglycols. More specifically, Fourier transform infrared (FTIR) spectroscopy has been used to evaluate the lipid order and dynamics, the hydration and the degree of protein aggregation of the nanoErythrosomes after covalent binding of polyethyleneglycols having molecular weights of 2000 and 5000 g mol(-1). The results indicate that the nanoErythrosome lipid chain order is not significantly affected by heating the nanoErythrosomes at temperatures up to 50 degrees C. They also indicate that the nanoErythrosome proteins aggregate irreversibly at temperatures above 37 degrees C, this effect being abolished in the presence of polyethyleneglycols. The presence of polyethyleneglycols decreases the accessibility of water to the lipid head groups. On the other hand, 31P-nuclear magnetic resonance (NMR) and electron microscopy results reveal that the presence of polyethyleneglycols prevents the aggregation of the nanoErythrosome structures.