Novel thiazonaphthalimides as efficient antitumor and DNA photocleaving agents: Effects of intercalation, side chains, and substituent groups

A Comprehensive Review on Fused Heterocyclic as DNA Intercalators: Promising Anticancer Agents

Since the discovery of DNA intercalating agents (by Lerman, 1961), a growing number of organic, inorganic, and metallic compounds have been developed to treat life-threatening microbial infections and cancers. Fused-heterocycles are amongst the most important group of compounds that have the ability to interact with DNA. DNA intercalators possess a planar aromatic ring structure that inserts itself between the base pairs of nucleic acids. Once inserted, the aromatic structure makes van der Waals interactions and hydrogen-bonding interactions with the base pairs. The DNA intercalator may also contain an ionizable group that can form ionic interactions with the negatively charged phosphate backbone. After the intercalation, other cellular processes could take place, leading ultimately to cell death. The heterocyclic nucleus present in the DNA intercalators can be considered as a pharmacophore that plays an instrumental role in dictating the affinity and selectivity exhibited by these compounds. In this work, we have carried out a revision of small organic molecules that bind to the DNA molecule via intercalation and cleaving and exert their antitumor activity. A general overview of the most recent results in this area, paying particular attention to compounds that are currently under clinical trials, is provided. Advancement in spectroscopic techniques studying DNA interaction can be examined in-depth, yielding important information on structure-activity relationships. In this comprehensive review, we have focused on the introduction to fused heterocyclic agents with DNA interacting features, from medicinal point of view. The structure-activity relationships points, cytotoxicity data, and binding data and future perspectives of medicinal compounds have been discussed in detail.

Synthesis and in vitro evaluation of naphthalimide-benzimidazole conjugates as potential antitumor agents

A series of novel naphthalimide-benzimidazoles was designed and synthesized for the first time and studied for their effect on antiproliferative activity. Some of these compounds possessed good antitumor activity towards the tested cancer cell lines. Noticeably, (diethylamino)ethyl 15 and (dimethylamino)ethyl 23 derivatives displayed superior antiproliferative activity towards human cancer cell lines with MG_MID GI50 values of 1.43 and 1.83 μM, respectively. Preliminary investigation revealed that compounds 15 and 23 might bind with ct-DNA through the intercalation mode which is responsible for potent bioactivity. Moreover, transportation behaviour indicated that these molecules could efficiently bind to and be carried by bovine albumin, and the hydrogen bonding and hydrophobic interactions played important roles in interaction with serum albumin.

Design, Synthesis and Evaluation of Naphthalimide Derivatives as Potential Anticancer Agents for Hepatocellular Carcinoma

Two kinds of naphthalimide derivatives were synthesized and evaluated for in vitro their anti-hepatocellular carcinoma properties. Compound 3a with a fused thiazole fragment to naphthalimide skeleton inhibited cell migration of SMMC-7721 and HepG2, and further in vivo trials with two animal models confirmed that compound 3a moderately inhibited primary H22 tumor growth (52.6%) and potently interrupted lung metastasis (75.7%) without obvious systemic toxicity at the therapeutic dose. Mechanistic research revealed that compound 3a inhibited cancerous liver cell growth mostly by inducing G2/M phase arrest. Western blotting experiments corroborated that 3a could up-regulate the cell cycle related protein expression of cyclin B1, CDK1 and p21, and inhibit cell migration by elevating the E-cadherin and attenuating integrin α6 expression. Our study showed that compound 3a is a valuable lead compound worthy of further investigation.

Design, Synthesis, and Proticity Inclined Conformational Modulation in a Highly Fluorescent Bichromophoric Naphthalimide Derivative: Hint Directed from RICT Perspective

The present study embodies design, in silico DNA interaction, synthesis of benzothiazole containing naphthalimide derivative, 2-(6-chlorobenzo[d]thiazol-2-yl)-1H-benzo[de] isoquinoline-1,3(2H)-dione (CBIQD) along with its systematic photophysics, solvatochromic behavior, and solvation dynamics using an experimental and theoretical spectroscopic approach. Steady-state dual emission and biexponential fluorescence decay reveals the formation of two different excited species. Ground- and excited-state optimized geometry and the potential-energy curve obtained from DFT and TD-DFT calculation ascertained the existence of nonplanar and planar conformation. When the solvent polarity is changed from nonpolar to protic polar, the feebly emissive emission band highly intensifies probably due to the reversal of n, π*-π, π* emissive state along with consequent modulation of their energy gap that is induced by H-bonding. Excluding nonpolar solvents, in all other solvents, the Stokes shift correlates linearly with orientation polarizability, whereas in water, the story remains intriguing. With photoexcitation, intermolecular H-bonding stimulates the pyramidalization tendency of imide "N" with subsequent conformational change of GS nonplanar geometry to a coplanar one through acceptor rehybridization generating a rehybridized intramolecular charge transfer (RICT) state that caused a dramatic fluorescence upsurge. This allosteric modulation is promoted by excited-state H-bonding dynamics especially in strong H-bond donor water. A close interplay between preferential solvation and the proximity effect is evident in the emission behavior in a benzene (Bn)-ethanol (EtOH) binary mixture. Molecular docking analysis delineates considerable noncovalent sandwiched π-π stacking interactions of CBIQD with the pyrimidine rings as well as with imidazole rings of dG 6 and dG 2 base pairs of B-DNA double helix, which probably suffices the design strategy adopted. Overall, a strategic design to synthesize a highly fluorescent and potential bioactive agent is executed to revolutionize the fluorophore field due its enormous progressive importance in biochemical applications.

Visible-light-induced cleavage of 4-α-amino acid substituted naphthalimides and its application in DNA photocleavage

4-α-Amino acid substituted naphthalimides can be photocleaved at the C–N bond between the 4-amino and the amino acid residue under visible light irradiation, releasing a fluorophore, 4-aminonaphthalimide.

Cyclic aromatic imides as a potential class of molecules for supramolecular interactions

Prospects of stacking interactions of imides beneficial to generation of new soft materials are projected by analysing examples of primary building blocks that provide a basis for understanding at the molecular level.

Induction of apoptosis and suppression of ERCC1 expression by the potent amonafide analogue 8-c in human colorectal carcinoma cells

Previous studies have reported that 8-c [6-(2-(2-(dimethylamino)ethylamino)ethylamino)-2-octyl-1H-benzo[de]isoquinoline-1,3(2H)-dione], a novel amonafide analogue, was generated as a new anticancer candidate. However, little is known about its activity in chemoresistant cells. In this study, the antitumor effects of 8-c on the multi-drug-resistant human colorectal carcinoma cancer cell lines HCT-116/L-OHP and HCT-8/VCR have been investigated for the first time. 8-c showed similar concentration-dependent inhibitory activities against multi-drug-resistant cells and corresponding parental cell lines by the MTT assay after 48 h of treatment. 8-c treatment resulted in the induction of apoptosis, as evidenced by fluorescent staining analysis, comet assay data, and the increase in the number of apoptotic cells as detected by flow cytometry. Western blot, qPCR, and siRNA techniques were used to elucidate the molecular mechanism. Our study suggested that the apoptotic effect of 8-c can be attributed to the upregulation of p53, caspase-3, and cleaved poly(ADP-ribose) polymerase (PARP) and the downregulation of Bcl-2. Furthermore, ERCC1 is essential for nucleotide excision repair. ERCC1 expression was correlated with sensitivity to chemotherapy in various colon cancer cell lines. It is intriguing that decreases in ERCC1 protein and mRNA levels were also observed in the HCT-116/L-OHP and HCT-8/VCR cells after exposure to 8-c. Further transient transfection of multi-drug-resistant cells with ERCC1 siRNA enhanced 8-c-induced cytotoxicity. In contrast, epidermal growth factor-induced increase in ERCC1 protein levels was shown to rescue cell viability upon 8-c treatment. These findings suggest that 8-c has a strong potential to be developed as a new antitumor agent for the treatment of multi-drug-resistant colon cancer cells, and is worthy of further studies.

Synthesis and anticancer activity evaluation of N-[4-(2-methylthiazol-4-yl)phenyl]acetamide derivatives containing (benz)azole moiety

A new class of novel thiazole-(benz)azole derivatives was synthesized to investigate their anticancer activity. The structure of the compounds was confirmed by IR, (1)H-NMR, and MS spectral data and elemental analyses. Anticancer effect of the compounds was evaluated against A549 and C6 tumor cell lines. MTT, analysis of DNA synthesis, acridine orange/ethidium bromide staining method and analysis of caspase-3 activation assays were performed for anticancer activity investigations. Compounds 6f and 6g, which carry 5-chloro and 5-methylbenzimidazole groups showed significant anticancer activity. Potential of these compounds to direct tumor cells to apoptotic pathway, which is a precondition of anticancer action, was also observed.

A ROS-mediated lysosomal-mitochondrial pathway is induced by a novel Amonafide analogue, 7c, in human Hela cervix carcinoma cells

In this study, a novel naphthalimide derivative 7c was designed which is topo II inhibiting though owning weak DNA binders. It was shown that 7c could induce cancer cells apoptosis and have less cytotoxicity in normal human cell. Further investigations on Hela cells revealed that 7c could also induce ROS generation, lysosome rupture as well as cathepsin B release. Subsequent mitochondrial damages including mitochondrial membrane permeabilization and the release of cytochrome c were also found in 7c when treating with Hela cells. According to our data, 7c may act as a lead compound for potential anticancer drugs. The idea of naphthalimides modification may also provide a novel strategy for naphthalimides design.

Spectroscopic Studies on the Binding Properties of Ofloxacin and Human Telomeric G-Quadruplex DNA

The binding of ofloxacin with human telomeric G-quadruplex DNA, Htel-G4-DNA and Htel-3-G4-DNA were examined by Fluorescence and CD spectroscopic methods. In the Fluorescence emission spectral analysis, the addition of ofloxacin induced significant quenching on the fluorescence emission of TO-G4-DNA complex. The fluorescence spectral analysis indicated that ofloxacin exhibited higher binding affinity and binding intensity to Htel-G4-DNA than Htel-3-G4-DNA. In the CD spectral analysis, the interaction with ofloxacin did not disturb the characteristic absorption of Htel-G4-DNA at 290 nm corresponding to its antiparallel form, and only slightly increased the positive absorption at 270 nm as shoulder peak, which suggests the antiparallel structure of G-quadruplex can remain stable in the presence of ofloxacin

A new class of naphthalimide-based antitumor agents that inhibit topoisomerase II and induce lysosomal membrane permeabilization and apoptosis

Based on the advantages of multitarget drugs for cancer treatment, a new class of naphthalimides was designed, synthesized, and proved to inhibit topoisomerase II (topo II), induced lysosomal membrane permeabilization (LMP), and ultimately caused apoptosis and cell death. The majority of compounds 7a-d and 8a-d potently inhibited the growth of the five tested cancer cell lines with IC(50) values ranging from 2 to 10 microM and are more active than amonafide, a naphthalimide that was in phase III clinical trials. These compounds were tested for their interactions with DNA and their cell-free topo II inhibition activities, which demonstrated these compounds were weak DNA binders but modest topo II inhibitors. Furthermore, compounds 7b-d were found to notably induce LMP and exhibited better antiproliferative activity compared with their single-target analogues. All of the newly synthesized compounds were demonstrated to efficiently induce apoptosis via a mitochondrial pathway. Accordingly, a new paradigm was suggested for the design of novel multitarget anticancer drugs.

Sequence-dependent interactions of cationic naphthalimides and polynucleotides

The binding interactions of three naphthalimide derivatives with heteropoly nucleic acids have been evaluated using fluorescence, absorption and circular dichroism spectroscopies. Mono- and bifunctionalized naphthalimides exhibit sequence-dependent variations in their affinity toward DNA. The heteropoly nucleic acids, [Poly(dA-dT)]2 and [Poly(dG-dC)]2, as well as calf thymus (CT) DNA, were used to understand the factors that govern binding strength and selectivity. Sequence selectivity was addressed by determining the binding constants as a function of polynucleotide composition according to the noncooperative McGhee-von Hippel binding model. Binding affinities toward [poly(dA-dT)](2) were the largest for spermine-substituted naphthalimides (Kb = 2-6 x 10(6) M(-1)). The association constants for complex formation between the cationic naphthalimides and [poly(dG-dC)]2 or CT DNA (58% A-T content) were 2-500 times smaller, depending on the naphthalimide-polynucleotide pair. The binding modes were also assessed using a combination of induced circular dichroism and salt effects to determine whether the naphthalimides associate with DNA through intercalative, electrostatic or groove-binding. The results show that the monofunctionalized spermine and pyridinium-substituted naphthalimides associate with DNA through electrostatic interactions. In contrast, intercalative interactions are predominant in the complex formed between the bifunctionalized spermine compound and all of the polynucleotides.

Highly efficient antitumor agents of heterocycles containing sulfur atom: Linear and angular thiazonaphthalimides against human lung cancer cell in vitro

A novel series of aminothiazonaphthalimides, A(1-2) and B(1-2), has been regioselectively synthesized. The linear compounds B(1-2) were evaluated to be far more active than their angular isomers A(1-2) in antitumor evaluation. The linear compounds C-F, derived from compound B(1), all showed highly efficient antitumor activities against A549 and P388 cell lines. Also, cytotoxicities of these four analogues against two tumor cells were highly dependent on the length of the side chains. The compound A(1) or B(1), with two methylene units in the side chain, was more cytotoxic than its corresponding homologue A(2) or B(2), with one more methylene unit.

Synthesis and Anti-tumor Activities of Novel Methylthio-, Sulfinyl-, and Sulfonyl-8H-thieno[2,3-b]pyrrolizin-8-oximino Derivatives

A series of novel methylthio-, sulfinyl-, and sulfonyl-8H-thieno[2,3-b]pyrrolizin-8-oximino derivatives 7A-12P was designed and synthesized as anti-tumor agents. Their structures were confirmed by IR, (1)H-NMR, MS, and elemental analysis. The anti-tumor activities of all the target compounds were tested by the MTT method in vitro against Bel-7402 (human liver cancer) and HT-1080 (human fibro sarcoma) cell lines. Among them, compound 11N (IC(50) = 18.2 microM, 8.2 microM), was the most promising compound of all synthesized molecules, it was 2.5- and 3.3-times more active than cisplatin (IC(50) = 45.2 microM, 26.7 microM), respectively.

Molecular design, chemical synthesis, and biological evaluation of ‘4-1’ pentacyclic aryl/heteroaryl-imidazonaphthalimides

A novel series of '4-1' pentacyclic naphthalimides, where the chromophore consists of a naphthalimide moiety, fused to an imidazole ring containing an unfused aryl or heteroaryl ring, were synthesized and evaluated for in vitro antitumor activity. In general, the new derivatives showed an improved cytotoxic activity over amonafide. DNA binding experiments supported that this class of compounds behaves as effective DNA-intercalating agents.

Design, syntheses, and antitumor activity of novel chromone and aurone derivatives

A series of new chromone analogues bearing heterocyclic thioether moiety and aurone analogues bearing cyclic tertiary amine moiety were designed and synthesized under microwave irradiation. The synthetic protocol was found to present many advantages, such as higher yields, shorter reaction time (10-20 min), mild condition, and readily isolation of the products. The synthesized compounds were assayed for their antitumor activity against four kinds of human solid tumor cell lines including HCCLM-7, Hep-2, MDA-MB-435S, and SW-480. Two compounds, (Z)-2-((4-benzyl-piperazin-1-yl)methylene)benzofuran-3(2H)-one 5e and (Z)-2-((4-(bis(4-fluorophenyl)methyl)piperazin-1-yl)methylene)benzofuran-3(2H)-one 5f, were identified as the most promising candidates with the IC(50) values in the range of 4.1-13.1 microM. Further cell cycle studies revealed that compounds 5e and 5f arrest the cell cycle in G(0)/G(1) phase and displayed apoptosis-inducing effect on Hep-2 cells.

R16, a novel amonafide analogue, induces apoptosis and G2-M arrest via poisoning topoisomerase II

Amonafide, a naphthalimide derivative, although selected for exploratory clinical trials for its potent anticancer activity, has long been challenged by its unpredictable side effects. In the present study, a novel amonafide analogue, 2-(2-dimethylamino)-6-thia-2-aza-benzo-[def]-chrysene-1,3-diones (R16) was synthesized by substituting 5'-NH(2) of the naphthyl with a heterocyclic group to amonafide, with additional introduction of a thiol group. In a panel of various human tumor cell lines, R16 was more cytotoxic than its parent compound amonafide. It was also effective against multidrug-resistant cells. Importantly, the i.p. administration of R16 inhibited tumor growth in mice implanted with S-180 sarcoma and H(22) hepatoma. The molecular and cellular machinery studies showed that the R16 functions as a topoisomerase II (topo II) poison via binding to the ATPase domain of human topo IIalpha. The superior cytotoxicity of R16 to amonafide was ascribed to its potent effects on trapping topo II-DNA cleavage complexes. Moreover, using a topo II catalytic inhibitor aclarubicin, ataxia-telangiectasia-mutated (ATM)/ATM- and Rad3-related (ATR) kinase inhibitor caffeine and topo II-deficient HL-60/MX2 cells, we further showed that R16-triggered DNA double-strand breaks, tumor cell cycle arrest, and apoptosis were in a topo II-dependent manner. Taken together, R16 stood out by its improved anticancer activity, appreciable anti-multidrug resistance activities, and well-defined topo II poisoning mechanisms, as comparable with the parent compound amonafide. All these collectively promise the potential value of R16 as an anticancer drug candidate, which deserves further development.