Designed novel nuclear localizing anticancer peptide targets p53 negative regulator MDM2 protein

Intracellular protein-protein interactions provide a major therapeutic target for the development of peptide-based anticancer therapeutic agents. MDM2 is the 491-residue protein encoded by the MDM2 oncogene. Being a ubiquitin-protein ligase, MDM2 represses the transcription ability of the tumor suppressor p53 by proteasome-mediated degradation. Under typical cellular circumstances, a sustained p53 expression level is maintained by negative regulation of MDM2, whereas under stress conditions, this is alleviated to increase the p53 level. Modulation of MDM2-p53 interaction via fabrication of an MDM2-interacting peptide could be a useful strategy to inhibit subsequent proteasomal degradation of p53 and initiation of p53 signaling leading to the initiation of p53-mediated apoptosis of tumor cells. Here, in this research work, a novel anticancer peptide mPNC-NLS targeting the nucleus and the MDM2 protein (p53 negative regulator) was designed to promote the p53 protein activity for the prevention of cancer. It induces effective apoptosis in both A549 and U87 cells and remains non-cytotoxic to normal lung fibroblast cells (WI38). Further, immunocytochemistry and Western blot results confirm that the designed mPNC-NLS peptide induces the apoptotic death of lung cancer cells via activation of p53 and p21 proteins and remarkably stifled the in vitro growth of 3D multicellular spheroids composed of A549 cells.

Prospecting the cancer therapeutic edge of chitosan-based gold nanoparticles through conformation selective binding to the parallel G-quadruplex formed by short telomeric DNA sequence: A multi-spectroscopic approach

The biological relevance of G4 structures formed in telomere & oncogenes promoters make them extremely crucial therapeutic target for cancer treatment. Herein, we have synthesized chitosan-based gold nanoparticles (CH-Au NPs) through green method and have investigated their interaction with G4 structures formed by short telomeric sequences to evaluate their potential for targeting G4 structures. Firstly, we have characterized morphological/physical attributes of synthesized CH-Au NPs and salt dependent structural aspects of model G-rich DNA sequence, 12-mer d(T2G4)2 [TETRA] using spectroscopic and biophysical techniques. The molecular interactions between CH-Au NPs and parallel/antiparallel TETRA G4 structures were evaluated using UV-Visible, CD, Fluorescence, CD melting, DLS and Zeta potential studies. The experimental data indicated that CH-Au NPs showed strong binding interactions with Parallel TETRA G4 and provided thermal stabilization to the structure, whereas their interactions with Antiparallel TETRA G4 DNA and Ct-DNA (DNA duplex) were found to be negligible. Further, CH-Au NPs were also investigated for their selectivity aptitude for different G4 structures formed by human telomeric sequences; d(T2AG3)3 [HUM-12] and d(T2AG3)4T [HUM-25]. Our findings suggested that CH-Au NPs exhibited topology specific binding aptitude towards G4 structure, which can be utilized to inhibit/modulate crucial biological functions for potential anticancer activity.

Targeting aloe active compounds to c-KIT promoter G-quadruplex and comparative study of their anti proliferative property

Small molecules targeting G-quadruplex of oncogene promoter is considered as a promising anticancer therapeutics approach. Natural aloe compounds aloe emodin, and its glycoside derivative aloe emodin-8-glucoside and aloin have anticancer activity and also have potential DNA binding ability. These three compounds have promising binding ability towards quadruplex structures particularly c-KIT G-quadruplex. Here, this study demonstrates complete biophysical study of these compounds to c-KIT quadruplex structure. Aloe emodin showed highest binding stabilization with c-KIT which has been proved by absorbance, fluorescence, dye displacement, ITC and SPR studies. Moreover, comparative study of these compounds with HCT 116 cells line also agreed to their anti proliferative property which may be helpful to establish these aloe compounds as potential anticancer drugs. This study comprises a complete biophysical study along with their anti proliferative property and demonstrates aloe emodin as a potent c-KIT binding molecule.

Mechanistic investigation into the binding property of Yohimbe towards natural polymeric DNAs

DNA interactions with multivalent ligand(s) have increasingly become the subject of substantial research. For several small molecules with therapeutic potential, nucleic acids serve as their primary molecular target. Such interaction has been shown to affect transcription or replication, ultimately leading to apoptotic cell death. As a result, researchers are becoming increasingly interested in understanding how small molecules interact with DNA making it possible to develop new, DNA-specific drugs. The bioactive indole alkaloid, Yohimbe (Yohimbine; Yh) has been broadly studied in pharmacological properties while its binding mode to DNA has not been explicated so far. This study adopted molecular modelling and multi-spectroscopic methods to investigate the interaction between Yohimbine and herring testes (HT DNA) in physiological conditions. Minor hypochromic and bathochromic shifts of fluorescence intensity were observed, suggesting the binding of Yh to HT DNA. The Scatchard plot analyses using the McGhee-von Hipple method revealed non-cooperative binding and affinities in the range of 105 M-1. The thermodynamic parameters suggested exothermic binding, which was favoured by negative enthalpy and positive entropy changes from temperature-dependent fluorescence experiments. Salt-dependent fluorescence suggested that the interaction between the ligand and DNA was governed by non-polyelectrolytic forces. The results of iodide quenching, urea denaturation assay, dye displacement, and in silico molecular docking, suggested groove binding of Yh to HT DNA. Thus, the groove binding mechanism of interaction was validated by both biophysical and computational techniques. The structural elucidation and energetic profiling of Yh's interaction with naturally occurring polymeric DNA can be useful to the development of DNA-targeted therapeutics.

Binding characterization of anthraquinone derivatives by stabilizing G-quadruplex DNA leads to an anticancerous activity

G-quadruplex is a non-canonical secondary structure identified in the telomeric region and the promoter of many oncogenes. Anthraquinone derivatives, a well-known inducer of telomere disruption in malignant cells and activate the apoptotic pathway. We used biophysical and biochemical studies to confirm the interaction of synthesized anthraquinone derivatives with the human telomeric G-quadruplex sequence. The binding affinity of N-2DEA and N-1DEA are K _b = 4.8 × 10⁶ M^-1 and K _b = 7.6 × 10⁵ M^-1, respectively, leading to hypochroism, fluorescence quenching with minor redshift and ellipticity variations indicating ligand binding in the external groove. We found that sodium ions induced stabilization more rather than potassium ions. Molecular docking of complex demonstrates a molecule's exterior binding to a quadruplex. The investigation of ROS activity indicated that the cell initiates mortality in response to the IC₅₀ concentration. Cellular morphology, nuclear condensation, and fragmentation were altered in the treated cell, impairing cellular function. Finally, the transcriptional regulatory study paves the way for drug design as an anti-cancer agent because of the tremendous possibilities of changing substituent groups on anthraquinones to improve efficacy and selectivity for G-quartet DNA. Our research focused on how ligand binding to telomere sequences induces oxidative stress and inhibits the growth of malignant cells.

Structural basis for stabilization of human telomeric G-quadruplex [d-(TTAGGGT)]4 by anticancer drug adriamycin

Besides inhibiting DNA duplication, DNA dependent RNA synthesis and topoisomerase-II enzyme action, anticancer drug adriamycin is found to cause telomere dysfunction and shows multiple strategies of action on gene functioning. We present evidence of binding of adriamycin to parallel stranded intermolecular [d-(TTAGGGT)]₄ G-quadruplex DNA comprising human telomeric DNA by proton and phosphorus-31 nuclear magnetic resonance spectroscopy. Diffusion ordered spectroscopy shows formation of complex between the two molecules. Changes in chemical shift and line broadening of DNA and adriamycin protons suggest participation of specific chemical groups/moieties in interaction. Presence of sequential nuclear Overhauser enhancements at all base quartet steps and absence of large downfield shifts in ³¹P resonances give clear proof of absence of intercalation of adriamycin chromophore between base quartets. Restrained molecular dynamics simulations using observed 15 short intermolecular inter proton distance contacts depict stacking of ring D of adriamycin with terminal G6 quartet by displacing T7 base and external groove binding close to T1-T2-A3 bases. The disappearance of imino protons monitored as a function of temperature and differential scanning calorimetry experiments yield thermal stabilization of 24 °C, which is likely to come in the way of telomerase association with telomeres. The findings pave the way for design of alternate anthracycline based drugs with specific modifications at ring D to enhance induced thermal stabilization and use alternate mechanism of binding to G-quadruplex DNA for interference in functional pathway of telomere maintenance by telomerase enzyme besides their well known action on duplex DNA. Communicated by Ramaswamy H. Sarma.

Dual mode of binding of anti cancer drug epirubicin to G-quadruplex [d-(TTAGGGT)]4 containing human telomeric DNA sequence induces thermal stabilization

Epirubicin exerts its anti cancer action by blocking DNA/RNA synthesis and inhibition of topoisomerase-II enzyme. Recent reports on its influence on telomere maintenance, suggest interaction with G-quadruplex DNA leading to multiple strategies of action. The binding of epirubicin with parallel stranded inter molecular G-quadruplex DNA [d-(TTAGGGT)]₄ comprising human telomeric DNA sequence TTAGGG was investigated by absorption, fluorescence, circular dichroism and nuclear magnetic resonance spectroscopy. The epirubicin binds as monomer to G-quadruplex DNA with affinity, K_b1 = 3.8 × 10⁶ M^-1 and K_b2 = 2.7 × 10⁶ M^-1, at two independent sites externally. The specific interactions induce thermal stabilization of DNA by 13.2-26.3 °C, which is likely to come in the way of telomere association with telomerase enzyme and contribute to epirubicin-induced apoptosis in cancer cell lines. The findings pave the way for drug designing in view of the possibility of altering substituent groups on anthracyclines to enhance efficacy using alternate mechanism of its interaction with G4 DNA, causing interference in telomere maintenance pathway by inducing telomere dysfunction.

Recent advances in allelopathy for weed control: from knowledge to applications

Allelopathy is the biological phenomenon of chemical interactions between living organisms in the ecosystem, and must be taken into account in addressing pest and weed problems in future sustainable agriculture. Allelopathy is a multidisciplinary science, but in some cases, aspects of its chemistry are overlooked, despite the need for a deep knowledge of the chemical structural characteristics of allelochemicals to facilitate the design of new herbicides. This review is focused on the most important advances in allelopathy, paying particular attention to the design and development of phenolic compounds, terpenoids and alkaloids as herbicides. The isolation of allelochemicals is mainly addressed, but other aspects such as the analysis and activities of derivatives or analogs are also covered. Furthermore, the use of allelopathy in the fight against parasitic plants is included. The past 12 years have been a prolific period for publications on allelopathy. This critical review discusses future research areas in this field and the state of the art is analyzed from the chemist's perspective. © 2019 Society of Chemical Industry.

Molecular recognition of 3+1 hybrid human telomeric G-quadruplex DNA d-[AGGG(TTAGGG)3] by anticancer drugs epirubicin and adriamycin leads to thermal stabilization

Recent reports suggest influence of anti-cancer anthracyclines on telomere dysfunction and their possible interaction with G-quadruplex (G4) DNA as an alternate pathway to apoptosis. We have investigated interaction of epirubicin and adriamycin with G4 DNA [d-AGGG(TTAGGG)₃] comprising human telomeric DNA sequence by surface plasmon resonance, absorption, fluorescence, circular dichroism and thermal denaturation. Epirubicin and adriamycin bind with affinity, K_b, = 2.5×10⁵ and 5.2×10⁵M^-1, respectively in monomeric form leading to decrease in absorbance, fluorescence quenching and ellipticity changes without any significant shift in absorption emission maxima with corresponding induced thermal stabilization by 13.0 and 11.6°C in K⁺ rich solution. Na⁺ ions did not induce any thermal stabilization. Molecular docking confirmed external binding at grooves and loops of G4 DNA involving 4OCH₃ of ring D, 9COCH₂OH of ring A, 4'OH/H and 3'NH₃⁺ of daunosamine sugar. Thermal stabilization induced by specific interactions is likely to hamper telomere association with telomerase enzyme and contribute to drug-induced apoptosis in cancer cell lines besides causing damage to duplex DNA. The findings pave the way for drug designing in view of immense possibilities of altering substituent groups on anthracyclines for enhancement of efficacy, reduced cell toxicity as well as specificity towards G-quadruplex DNA.

Molecular Recognition of Parallel G-quadruplex [d-(TTGGGGT)]₄ Containing Tetrahymena Telomeric DNA Sequence by Anticancer Drug Daunomycin: NMR-Based Structure and Thermal Stability

The anticancer drug daunomycin exerts its influence by multiple strategies of action to interfere with gene functioning. Besides inhibiting DNA/RNA synthesis and topoisomerase-II, it affects the functional pathway of telomere maintenance by the telomerase enzyme. We present evidence of the binding of daunomycin to parallel-stranded tetramolecular [d-(TTGGGGT)]₄ guanine (G)-quadruplex DNA comprising telomeric DNA from Tetrahymena thermophilia by surface plasmon resonance and Diffusion Ordered SpectroscopY (DOSY). Circular Dichroism (CD) spectra show the disruption of daunomycin dimers, suggesting the end-stacking and groove-binding of the daunomycin monomer. Proton and phosphorus-31 Nuclear Magnetic Resonance (NMR) spectroscopy show a sequence-specific interaction and a clear proof of absence of intercalation of the daunomycin chromophore between base quartets or stacking between G-quadruplexes. Restrained molecular dynamics simulations using observed short interproton distance contacts depict interaction at the molecular level. The interactions involving ring A and daunosamine protons, the stacking of an aromatic ring of daunomycin with a terminal G6 quartet by displacing the T7 base, and external groove-binding close to the T1–T2 bases lead to the thermal stabilization of 15 °C, which is likely to inhibit the association of telomerase with telomeres. The findings have implications in the structure-based designing of anthracycline drugs as potent telomerase inhibitors.