Search

Dithiocarbamate has been tested for its effective anti-tumor activity, but the underlying mechanism remains unclear. We previously prepared a novel diththiocarbamate derivative, DpdtC with an ability of catalase inhibition. Here, we for the first time investigated the growth inhibition effects of DpdtC on HER2-amplified cancer cells and elucidated its mechanism of action. Results showed that DpdtC exerted the potent anti-tumor effects against HER2-overexpressed SK-OV-3 and SK-BR-3 cells, especially on SK-OV-3 cells with a higher NDRG1 level, which was also confirmed in the SK-OV-3 xenograft model. Interestingly, we observed that NDRG1 was up-regulated, while membrane expression of HER2 was regressed in SK-OV-3 cells upon DpdtC treatment. In agreement, silencing endogenous NDRG1 also increased the expression of HER2 in SK-OV-3 cells, while overexpressing NDRG1 decreased HER2 expression in SK-BR-3 cells. Furthermore, our results showed the formation of the EGFR/HER2 heterodimer was attenuated and phosphorylation of ERK1/2 was inhibited in SK-OV-3 cells when treated with DpdtC. Collectively, these observations demonstrated that NDRG1 plays an important role in mediating the inhibition effects of DpdtC in HER2-overexpressed cancer cells via selective targeting of the HER2-ERK1/2 pathway. Hence, our investigation suggests that up-regulation of NDRG1 by DpdtC is a promising therapeutic approach in HER2-overexpressed cancers.

Cancer cells have higher demand of iron and copper ions for growth, disturbing the metal's homeostasis can inhibit proliferation of cancer cell. Dithiocarbamates possessing excellent metal chelating ability and antitumor activity are considered as candidates in chelation therapy, however, their antitumor molecular mechanisms remain to be elucidated. In the present study, a dithiocarbamate derivative, di-2-pyridylhydrazone dithiocarbamate s-acetic acid (DpdtaA) was prepared to address the issue whether the molecular mechanism behind biological behavior showed by dithiocarbamate was p53 mediated. The proliferation inhibition assay showed that DpdtaA exhibited excellent antiproliferative effect for hepatocellular carcinoma (IC50= 3.0±0.4 µM for HepG2, 6.1±0.6 µM for Bel-7402 cell). However, in the presence of copper ion, the antiproliferative activity of DpdtaA significantly attenuated (~3-fold for HepG2) due to formation of copper chelate. The ROS assay revealed that the antiproliferative activity of DpdtaA correlated with ROS generation. Western blotting demonstrated that DpdtaA could upregulate p53 via down-regulating the Mdm2, accordingly leading to changes of bcl family proteins, indicating that a p53-dependent intrinsic apoptosis was partly involved. Simulation from molecular docking hinted that DpdtaA could disrupt interaction between p53 and Mdm2, indicating the disruption might also contribute to the upregulation of p53. The alternations in lysosome membrane permeability and acidic vacuoles as well as LC3-II upregulation indicated that autophagy was involved. The copper addition led to significantly attenuate biological activity of DpdtaA, with few dithiocarbamates, but the mechanism in apoptosis induction was not altered except for weaker ability.

Thiosemicarbazones display significant antitumor activity and their copper complexes also exhibit enhanced biological activities in most situations, but the underlying mechanism is poorly understood. Therefore, investigation of the mechanism involved in the change upon chelation is required to extend our understanding of the effects of thiosemicarbazones. In the present study, the inhibitory effect of 2-pyridinecarboxaldehyde thiosemicarbazone (PCT) and its copper complex (PCT-Cu) on cell proliferation was investigated. The copper chelate exhibited a 3- to 10-fold increase in antitumor activity (with an IC50

The bioactivity of drugs is attributed to their interaction with biological molecules, embodied in either their direct or indirect influence on enzyme activity and conformation. Di-2-pyridylketone hydrazine dithiocarbamate (DpdtC) exhibits significant antitumor activity in our preliminary study. We speculated that its activity may partly stem from enzyme inhibition due to strong metal chelating ability. To this end, we assessed its effect on catalase from erythrocytes and found evidence of inhibition, which was further confirmed by ROS determination in vivo. Thus, detailing the interaction between the agent and catalase via spectroscopic methods and molecular docking was required to obtain information on both the dynamics and thermodynamic parameters. The Lineweaver-Burk plot implied an uncompetitive pattern between DpdtC and catalase from beef liver, and IC50 = ∼7 μM. The thermodynamic parameters from fluorescence quenching measurements indicated that DpdtC could bind to catalase with moderate affinity (Ka = approximately 104 M-1). CD spectra revealed that DpdtC could significantly disrupt the secondary structure of catalase. Docking studies indicated that DpdtC bound to a flexible region of catalase, involving hydrogen bonds and salt bond; this was consistent with thermodynamic results from spectral investigations. Our data clearly showed that catalase inhibition of DpdtC was not due to direct chelation of iron from heme (killing), but through an allosteric effect. Thus, it can be concluded that the antiproliferative activity of DpdtC is partially attributed to its catalase inhibition.

To promote targeting specificity of anti-CD47 agents, we have constructed a novel bispecific antibody fusion protein against EGFR and CD47, which may minimize the “off-target” effects caused by CD47 expression on red blood cells. The novel bispecific antibody fusion protein, denoted as Bi-SP could simultaneously bind to EGFR and CD47 and exhibited potent phagocytosis-stimulation effects in vitro. Bi-SP treatment with a low dose more effectively inhibited tumor growth than either EGFR-targeting antibody, Pan or the SIRPα variant-Fc (SIRPαV-Fc) in the A431 xenograft tumor model. In addition, the treatment with Bi-SP produced less red blood cell (RBC) losses than the SIRPαV-Fc treatment, suggesting its potential use for minimizing RBC toxicity in therapy. Bi-SP with improved therapeutic index has the potential to treat CD47+ and EGFR+ cancers in clinics.

As a result of a recent letter to the editor [1], we would like to make several corrections to ourmanuscript [2].We would like to correct the sentence on page 1: “no studies have examined the effects ofthe interaction between Dp44mT and biological molecules, such as proteins and nucleic acids”.This sentence should read: “information related to the effects of the interaction between Dp44mTand biological molecules such as human serum albumin (HSA) or DNA has not yet been fully andsystematically studied”.Furthermore, we provide information on the correctness and purity of the synthesized Dp44mT.

Di-2-pyridylketone-4,4,-dimethyl-3-thiosemicarbazone (Dp44mT) exhibits significant antitumor activity. However, the mechanism of its pharmacological interaction with human serum albumin (HSA) and DNA remains poorly understood. Here, we aimed to elucidate the interactions of Dp44mT with HSA and DNA using MTT assays, spectroscopic methods, and molecular docking analysis. Our results indicated that addition of HSA at a ratio of 1:1 did not alter the cytotoxicity of Dp44mT, but did affect the cytotoxicity of the Dp44mT-Cu complex. Data from fluorescence quenching and UV-VIS absorbance measurements demonstrated that Dp44mT could bind to HSA with a moderate affinity (Ka = approximately 10⁴ M(-1)). CD spectra revealed that Dp44mT could slightly disrupt the secondary structure of HSA. Dp44mT could also interact with Ct-DNA, but had a moderate binding constant (KEB = approximately 10⁴ M(-1)). Docking studies indicated that the IB site of HSA, but not the IIA and IIIA sites, could be favorable for Dp44mT and that binding of Dp44mT to HSA involved hydrogen bonds and hydrophobic force, consistent with thermodynamic results from spectral investigations. Thus, the moderate binding affinity of Dp44mT with HSA and DNA partially contributed to its antitumor activity and may be preferable in drug design approaches.

The drug, di-2-pyridylketone-2-pyridine carboxylic acid hydrazone (DPPCAH) and its copper complex (DPPCAH-Cu) exhibit significant antitumor activity. However, the mechanism of their pharmacological interaction with the biological molecule bovine serum albumin (BSA) remains poorly understood. The present study elucidates the interactions between the drug and BSA through MTT assays, spectroscopic methods and molecular docking analysis. Our results indicate that BSA could attenuate effect on the cytotoxicity of DPPCAH, but not DPPCAH-Cu. Data from fluorescence quenching measurements demonstrated that both DPPCAH and DPPCAH-Cu could bind to BSA, with a reversed effect on the environment of tryptophan residues in polarity. CD spectra revealed that the DPPCAH-Cu exerted a slightly stronger effect on the secondary structure of BSA than DPPCAH. The association constant of DPPCAH with BSA was greater than that of DPPCAH-Cu. Docking studies indicated that the binding of DPPCAH to BSA involved a greater number of hydrogen bonds compared to DPPCAH-Cu. The calculated distances between bound ligands and tryptophans in BSA were in agreement with fluorescence resonance energy transfer results. Thus, the binding affinity of the drug (DPPCAH or DPPCAH-Cu) with BSA partially contributes to its antitumor activity; the greater the drug affinity is to BSA, the less is its antitumor activity.

Many anticancer drugs used in the clinical have potent metal chelating ability. The formed metal complex(es) may exhibit improved (or antagonistic) antitumor activity. However, the underlying mechanism has received limited attention. Therefore, investigation of the mechanism involved in the change upon chelation is required to extend our understanding of the effects of various drugs. In the present study, the proliferation inhibition effect of benzaldehyde nitrogen mustard-2-pyridine carboxylic acid hydrazone (BNMPH) and its copper complex on tumor cell lines was investigated. The copper chelate exhibited almost a 10-fold increase in antitumor activity (with IC50

This response refers to:Xu, Z.; Liu, Y.; Zhou, S.; Fu, Y.; Li, C. Analysis of the Interaction of Dp44mT with Human SerumAlbumin and Calf Thymus DNA Using Molecular Docking and Spectroscopic Techniques. Int. J.Mol. Sci. 2016 , 17, 1042.Merlot, A.M.; Sahni, S.; Lane, D.J.R.; Richardson, V.; Huang, M.L.H.; Kalinowski, D.S.;Richardson, D.R. Letter to the Editor: Analysis of the Interaction of Dp44mT with Human SerumAlbumin and Calf Thymus DNA Using Molecular Docking and Spectroscopic Techniques and. Int. J.Mol. Sci. 2016 , 17, 1916. Keywords: Dp44mT; fluorescence quenching; molecular docking; human serum albumin;cytotoxicity; MTT; spectroscopy; circular dichroism Dear Editors, Thank you for forwarding the concerns (or comments) from Dr. Richardson [1] regarding ourpaper “Analysis of the Interaction of Dp44mT with Human Serum Albumin and Calf Thymus DNAUsing Molecular Docking and Spectroscopic Techniques” [2], which was recently published in theInternational Journal of Molecular Sciences. We are aware of the fact that Dr. Richardson in a leadingresearcher in the field and both respect Dr. Richardson and regularly refer to the many publicationsfrom his group.Nonetheless, we would like to respond to the specific concerns raised by Dr. Richardson.In reading the article by Xu, Z., et al. entitled “Analysis of the Interaction of Dp44mT with Human SerumAlbumin and Calf Thymus DNA Using Molecular Docking and Spectroscopic Techniques” [Int. J. Mol. Sci.2016, 17, 1042], there is evidence that some of the key methods and comparisons utilized in this study arenon-optimal and problematic.We would also like to bring to the attention of readers a number of important flaws and factually incorrectstatements in this article.The paper examines the binding of the anti-cancer agent, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), to human serum albumin (HSA) and DNA and states (page 1, Introduction

The use of chelators for cancer treatment has been an alternative option. Dithiocarbamates have recently attracted considerable attention owning to their diverse biological activities; thus, the preparation of new dithiocarbamate derivatives with improved antitumor activity and selectivity as well as probing the underlying molecular mechanism are required. In this study, di-2-pyridylhydrazone dithiocarbamate S-propionic acid (DpdtpA) and its copper complex were prepared and characterized, and its antiproliferative activity was evaluated. The proliferation inhibition assay showed that DpdtpA exhibited excellent antiproliferative effect in hepatocellular carcinoma (IC50 = 1.3 ± 0.3 μM for HepG2, and 2.5 ± 0.6 μM for Bel-7402). However, in the presence of copper ion, the antiproliferative activity of DpdtpA was dramatically attenuated (20-30 fold) owing to the formation of copper chelate. A preliminarily mechanistic study revealed that reactive oxygen species (ROS) generation mediated the antiproliferative activity of DpdtpA, and accordingly induced apoptosis, DNA cleavage, and autophagy. Surprisingly, the cytotoxicity of DpdtpA copper complex (DpdtpA-Cu) was also involved in ROS generation; however, a paradoxical relation between cellular ROS level and cytotoxicity was observed. Further investigation indicated that DpdtpA could induce cell cycle arrest at the S phase; however, DpdtpA-Cu lacked this effect, which explained the difference in their antiproliferative activity.