Influence of polyamine architecture on the transport and topoisomerase II inhibitory properties of polyamine DNA-intercalator conjugates

The potential role of c-MYC and polyamine metabolism in multiple drug resistance in bladder cancer investigated by metabonomics

Bladder cancer has a high incidence worldwide accompanies by high recurrent rate after treatment. The emergence of primary or acquired chemotherapy resistance leads to poor efficacy in many cases. To explore the underlying mechanisms of drug resistance, we firstly established a drug-resistant cell model T24/THP by repeated exposure of T24 cells to pirarubicin (THP) whose concentration increases gradually. Non-targeted metabolomics was performed to identify metabolic changes and key metabolism pathways variance in T24/THP cells. Pathway enrichment analysis demonstrated that the arginine and proline metabolic pathway was the most significantly changed pathway, where two representative members of polyamine, putrescine and spermidine were remarkably down regulated in T24/THP. Subsequent experiments further confirmed that ornithine decarboxylase (ODC1) and spermidine synthase (SRM), the key enzymes involved in the synthesis of these compounds, also showed a stable low expression in T24/THP. However, knocking down of ODC1 and SRM sensitized cells to chemotherapy treatment while overexpression of these two enzymes enhances chemotherapy resistance. This leaded to the point that ODC1 and SRM themselves are more likely to promote the drug resistance, which appears to contradict their low expression in T24/THP. We hypothesize that their diminished levels were due to the declined activity of genes upstream. According to this line of thought, we found that c-MYC was also down-regulated in T24/THP and its content could be significantly affected by drug administration. In addition, c-MYC could not only regulate the expression levels of ODC1 and SRM but also influence drug resistance in T24/THP. In conclusion, alterations in gene expression of ODC1 and SRM in drug resistance cell line is probably mediated by some upstream regulators rather than antineoplastic agents alone. Exploration of upstream signals and research on detailed regulatory mechanism, thereby understanding the actual role of c-MYC and polyamine in response to chemotherapy, can become a potential field direction to overcome drug resistance in bladder cancer.

Polyamine transport inhibitors: design, synthesis, and combination therapies with difluoromethylornithine

The development of polyamine transport inhibitors (PTIs), in combination with the polyamine biosynthesis inhibitor difluoromethylornithine (DFMO), provides a method to target cancers with high polyamine requirements. The DFMO+PTI combination therapy results in sustained intracellular polyamine depletion and cell death. A series of substituted benzene derivatives were evaluated for their ability to inhibit the import of spermidine in DFMO-treated Chinese hamster ovary (CHO) and L3.6pl human pancreatic cancer cells. Several design features were discovered which strongly influenced PTI potency, sensitivity to amine oxidases, and cytotoxicity. These included changes in (a) the number of polyamine chains appended to the ring system, (b) the polyamine sequence, (c) the attachment linkage of the polyamine to the aryl core, and (d) the presence of a terminal N-methyl group. Of the series tested, the optimal design was N(1),N(1'),N(1″)-(benzene-1,3,5-triyltris(methylene))tris(N(4)-(4-(methylamino)butyl)butane-1,4-diamine, 6b, which contained three N-methylhomospermidine motifs. This PTI exhibited decreased sensitivity to amine oxidases and low toxicity as well as high potency (EC50 = 1.4 μM) in inhibiting the uptake of spermidine (1 μM) in DFMO-treated L3.6pl human pancreatic cancer cells.

Mononaphthalimide spermidine conjugate induces cell proliferation inhibition and apoptosis in HeLa cells

Developing polyamine-drug conjugates that are capable of specific entry to tumor cells is attractive in improving chemotherapeutic efficacy. Currently, the exact cytotoxic mechanism of these conjugates is not well known. Here, our research revealed the effect of a mononaphthalimide-spermidine (MNISpd) conjugate on the growth and survival of HeLa cells and possible mechanisms. In characterizing the mechanism of MNISpd cytotoxicity, inhibition of proliferation is observed in the 0.5-6 μM range and there is evidence of apoptosis at equal or greater than 6 μM, but with less toxicity on HELF cell. The lower concentrations of MNISpd induced a cell cycle arrest correlated with enhanced p21 expression and decreased cdc2 but not Cdk2 expression. MNISpd-induced apoptosis was correlated with caspase-3 activation, decreased XIAP expression and a loss of mitochondrial membrane potential. Apoptosis but not cell cycle arrest was susceptible to N-acetyl-L-cysteine (NAC) treatment. It is proposed that MNISpd-induced apoptosis in HeLa cells is related to oxidative stress and that at lower exposure concentrations effects on cell proliferation predominate while at higher concentrations apoptosis develops.

Synthesis and in vitro biological evaluation of new polyamine conjugates as potential anticancer drugs

The synthesis of new polyamine derivatives containing dimeric quinoline (3a-c), cinnoline (4a-c) and phthalimide (7a-c and 8a-c) moieties is described. Three different polyamines: (1,4-bis(3-aminopropyl)piperazine (a), 4,9-dioxa-1,12-dodecanediamine (b), 3,3'-diamino-N-methyldipropylamine (c) were used as linkers. The new compounds were obtained according to known procedures. Their biological activity was assessed in vitro in a highly aggressive melanoma cell line A375. Polyamine diimides containing phthalimide moieties demonstrated no inhibitory activities against melanoma cells. Quinoline diamides were more efficient than cinnoline ones. Mainly cytostatic activity exerted as altered cell cycle profiles was observed at the concentrations causing about 50% reduction of adherent cell proliferation. Based on their structure as well as their biological activity, we assume that some of the newly synthesized compounds may act as DNA bisintercalators. This study might be useful for further designing and developing anticancer drugs with potent activities.

Preclinical activity of F14512, designed to target tumors expressing an active polyamine transport system

We have exploited the polyamine transport system (PTS) to deliver selectively a spermine-drug conjugate, F14512 to cancer cells. This study was aimed to define F14512 anticancer efficacy against tumor models and to investigate whether fluorophor-labeled polyamine probes could be used to identify tumors expressing a highly active PTS and that might be sensitive to F14512 treatments. Eighteen tumor models were used to assess F14512 antitumor activity. Cellular uptake of spermine-based fluorescent probes was measured by flow cytometry in cells sampled from tumor xenografts by needle biopsy. The accumulation of the fluorescent probe within B16 tumors in vivo was assessed using infrared fluorescence imaging. This study has provided evidence of a major antitumor activity for F14512. Significant responses were obtained in 67% of the tumor models evaluated, with a high level of activity recorded in 33% of the responsive models. Complete tumor regressions were observed after i.v., i.p. or oral administrations of F14512 and its antitumor activity was demonstrated over a range of 2-5 dose levels, providing evidence of its good tolerance. The level of cellular fluorescence emitted by the fluorescent probes was higher in cells sampled from tumors sensitive to F14512 treatments than from F14512-refractory tumors. We suggest that these probes could be used to identify tumors expressing a highly active PTS and guide the selection of patients that might be treated with F14512. These results emphasize the preclinical interest of this novel molecule and support its further clinical development.

Effect of spermine conjugation on the interaction of acridine with alternating purine-pyrimidine oligodeoxyribonucleotides studied by CD, fluorescence and absorption spectroscopies

We studied by electronic spectroscopies the interaction between double-stranded oligonucleotides containing either adenine-thymine or guanine-cytosine alternating sequences and N(1)-(acridin-9-yl)-1,16-diamino-4,8,13-triazahexadecane, which is a conjugated molecule formed by the covalent binding of spermine and 9-aminoacridine moieties via a trimethylene chain. Solutions containing the oligonucleotides and the conjugate, at different molar ratios, were studied by using electronic absorption, fluorescence emission and circular dichroism. Calculated association constants and fluorescence emission spectra showed that spermine conjugation induces sequence selectivity. The orientation of the intercalated acridine rings with respect to the oligonucleotide base planes was deduced from the electronic circular dichroism spectra. Evidence of the formation of spermine-induced aggregated structures, with potential applications to DNA packaging, gene therapy and anti-tumor therapy, was also achieved. Our data demonstrates that this spermine-acridine conjugate adds several specific characteristics provided by the polyamine moiety, as sequence selectivity, to the interesting properties of acridine derivatives.

Designing the polyamine pharmacophore: influence of N-substituents on the transport behavior of polyamine conjugates

N-Ethylated N-arylmethyl polyamine conjugates were synthesized and evaluated for their ability to target the polyamine transporter (PAT). To understand the effect of N-ethylation upon PAT selectivity, ethyl groups were appended onto a PAT-selective N (1)-anthracenenylmethyl homospermidine derivative, 1b. Bioevaluation in L1210 murine leukemia cells and in two Chinese hamster ovary cell lines (PAT-active CHO and PAT-deficient CHO-MG) revealed a dramatic decrease in PAT targeting ability upon N (1) or N (5) ethylation of the pharmacophore 1b. Experiments using the amine oxidase inhibitor, aminoguanidine (AG, 2 mM), revealed that the N (9)-ethyl and N (9)-methyl analogues were able to retain their PAT selectivity and cytotoxicity properties in the presence or absence of AG. In contrast, the lead compound 1b (containing a terminal NH 2 group) revealed a dramatic reduction in both its PAT-targeting ability and cytotoxicity in the absence of AG. An improved balance between these three properties of PAT-targeting, cytotoxicity and metabolic stability can be attained via N-methylation at the N (9)-position.

Study by optical spectroscopy and molecular dynamics of the interaction of acridine-spermine conjugate with DNA

We report a spectroscopic and theoretical study of the interaction between double-stranded oligonucleotides containing either adenine-thymine or guanine-cytosine alternating sequences and N1-(Acridin-9-ylcarbonyl)-1,5,9,14,18-pentazaoctadecane, or ASC, which is formed by the covalent bonding of spermine and 9-amidoacridine moieties via a trimethylene chain. Solutions containing the oligonucleotides and the conjugate at different molar ratios were studied using complementary spectroscopic techniques, including electronic absorption, fluorescence emission, circular dichroism, and Raman spectroscopy. The spectroscopical properties of ASC at both the vibrational and the electronic levels were described by means of ab initio quantum-chemical calculations on 9-amidoacridine, used as a model compound. Molecular dynamics calculations, based on the QM/MM methodology, were also performed using previously docked structures of two oligonucleotide-ASC complexes containing the A-T and the G-C sequence. Our data, taken all together, allowed us to demonstrate that conjugation of spermine to acridine modulates and gives additional properties to the interaction of the latter with DNA. As the ASC molecule has a high affinity by the polyamine transport system, these results are promising for their application in the development of new anti-tumour drugs.

Targeting polyamine metabolism and function in cancer and other hyperproliferative diseases

The polyamines spermidine and spermine and their diamine precursor putrescine are naturally occurring, polycationic alkylamines that are essential for eukaryotic cell growth. The requirement for and the metabolism of polyamines are frequently dysregulated in cancer and other hyperproliferative diseases, thus making polyamine function and metabolism attractive targets for therapeutic intervention. Recent advances in our understanding of polyamine function, metabolic regulation, and differences between normal cells and tumour cells with respect to polyamine biology, have reinforced the interest in this target-rich pathway for drug development.

Structure-activity investigations of polyamine-anthracene conjugates and their uptake via the polyamine transporter

A series of polyamine conjugates were synthesized and evaluated for their ability to target the polyamine transporter (PAT) in two Chinese hamster ovary (CHO) cell lines (PAT-active CHO and PAT-inactive CHOMG). This systematic study identified salient features of the polyamine architecture required to target and enter cells via the PAT. Indeed, the separation of charges, the degree of N-alkylation, and the spacer unit connecting the N(1)-terminus to the appended cytotoxic component (anthracene) were found to be key contributors to optimal delivery via the PAT. Using the CHO screen, the homospermidine motif (e.g., 4,4-triamine) was identified as a polyamine vector, which could enable the selective import of large N(1)-substituents (i.e., naphthylmethyl, anthracenylmethyl and pyrenylmethyl), which were cytotoxic to cells. The cell selectivity of this approach was demonstrated in B-16 murine melanoma cells and normal melanocytes (Mel-A). Three polyamine areas (recognition and transport, vesicle sequestration and polyamine-target interactions) were identified for future research.

Acenaphtho[1,2-b]pyrrole derivatives as new family of intercalators: Various DNA binding geometry and interesting antitumor capacity

A series of acenaphtho[1,2-b]pyrrole derivatives were synthesized and their intercalation geometries with DNA and antitumor activities were investigated in detail. From combination of SYBR Green-DNA melt curve, fluorescence titration, absorption titration, and circular dichroism (CD) studies, it was identified that to different extent, all the compounds behaved as DNA intercalators and transformed B form DNA to A-like conformation. The different intercalation modes for the compounds were revealed. The compounds containing a methylpiperazine substitution (series I) intercalated in a fashion that the long axis of the molecule paralleled to the base-pair long axis, while the alkylamine- substituted compounds (series II and III) located vertically to the long axis of DNA base pairs. Consequently, the DNA binding affinity of these compounds was obtained with the order of II>III>I, which attributed to the role of the substitution in binding geometry. Further, cell-based studies showed all the compounds exhibited outstanding antitumor activities against two human tumor cell lines with IC(50) ranging from 10(-7) to 10(-6)M. Interestingly, compound (1)a (a compound in series I), whose binding affinity was one of the lowest but altered DNA conformation most significantly, showed much lower IC(50) value than other compounds. Moreover, it could induce tumor cells apoptosis, while the compounds (2)a and (3)a (in series II and III, respectively) could only necrotize tumor cells. Their different mechanism of killing tumor cells might lie in their different DNA binding geometry. It could be concluded that the geometry of intercalator-DNA complex contributed much more to the antitumor property than binding affinity.

Bisindenoisoquinoline Bis-1,3-{(5,6-dihydro-5,11-diketo-11H-indeno[1,2-c]isoquinoline)-6-propylamino}propane bis(trifluoroacetate) (NSC 727357), a DNA Intercalator and Topoisomerase Inhibitor with Antitumor Activity

Indenoisoquinolines are topoisomerase (Top) I inhibitors developed to overcome some of the limitations of camptothecins and expand their anticancer spectrum. Bis-1,3-{(5,6-dihydro-5,11-diketo-11H-indeno[1,2-c]isoquinoline)-6-propylamino}-propane bis(trifluoroacetate) (NSC 727357) is a novel dimeric indenoisoquinoline derivative with potent antiproliferative activity in the NCI-60 cell line panel, promising hollow fiber activity (score of 32) and activity against xenografts. Submicromolar concentrations of the bisindenoisoquinoline NSC 727357 induce Top1 cleavage complexes at specific sites in biochemical assays. At higher concentrations, inhibition of Top1 catalytic activity and DNA intercalation is observed. NSC 727357 also induces a limited number of Top2-DNA cleavage complexes. In contrast to the effect of other Top1 inhibitors, cells treated with the bisindenoisoquinoline NSC 727357 show an arrest of cell cycle progression in G(1) with no significant inhibition of DNA synthesis after a short exposure to the drug. Moreover, unlike camptothecin and the indenoisoquinoline MJ-III-65 (NSC 706744, 6-[3-(2-hydroxyethyl)aminopropyl]-5,6-dihydro-5,11-diketo-2,3-dimethoxy-(methylenedioxy)-11H-indeno[1,2-c]isoquinoline hydrochloride), the cytotoxicity of bisindenoisoquinoline NSC 727357 is only partially dependent on Top1 and p53, indicating that this drug has additional targets besides Top1 and Top2.

Synthesis and DNA-binding affinities of monomodified berberines

Four new monomodified berberines have been synthesized in moderate to good yields starting from berberine and fully characterized by HRMS and 1H NMR. Spectrometric titration and ethidium bromide displacement experiments indicate that these berberine derivatives, especially the one having primary amino group, strongly bind with calf-thymus DNA, presumably via an intercalation mechanism.

Impact of Topoisomerase II alpha and spermine on the clinical outcome of children with acute lymphoblastic leukemia

It has been reported in the literature that a leukemic cell may be (or become) resistant to anti-cancer treatment because many mechanisms, such as efflux membrane pump (multi-drug resistance, MDR-P170), intracellular transport (LRP, MRP), or different detoxification systems (glutathione transferases, methallothioneines) may be implicated. Topoisomerase II alpha (TopoII) are also reported as responsible for resistance since their main action is to repair DNA breakage. Polyamines are described as having a protective DNA action by stabilizing the double stranded DNA helix. For these reasons we investigated 65 children with acute lymphoblastic leukemia using an immunocytochemical method to elucidate the potential role of Topoisomerase and polyamines in drug resistance. Most children (60/65) were treated with the French (acute lymphoblastic leukemia, ALL) protocol (FRALLE-93) in which B and C arms include (at least) VP16. Children with cytoplasmic TopoII positivity (18 cases) were more resistant since their overall survival was 34 months compared to more than 110 months for negative cases ( P = 0.0003). Polyamines may be associated with drug resistance since the overall survivals were 51 months and 92 months for positive and negative patients, respectively, but the P-value is only 0.13. We conclude that Topoisomerase and polyamines must be tested at diagnosis as new possible markers for chemo-resistance. Larger series are needed to confirm these preliminary results and to verify if the use of anti epipodophillotoxin agents (as it is the case for FRALLE B or C) should be excluded for positive cases.

Synthesis of a novel nitroimidazole-spermidine derivative as a tumor-targeted hypoxia-selective cytotoxin

A four-step synthesis of (R,S)-N(4)-[3-(2-nitro-1-imidazolyl)-2-hydroxypropyl]-spermidine trihydrochloride (4) is described and the utilization of the polyamine active transport system for the uptake of this compound in cells is demonstrated. Thus, V79 cells pretreated with an inhibitor of spermidine biosynthesis, alpha-difluoromethylornithine (DFMO), are ca. 2-fold more sensitive to 4 under hypoxic conditions, compared to untreated cells. Similarly, radiosensitization of hypoxic V79 cells by 4 is improved in DFMO-pretreated cells.