Investigation of protein induction in tumour vascular targeted strategies by MALDI MSI

Characterising the protein signatures in tumours following vascular-targeted therapy will help determine both treatment response and resistance mechanisms. Here, mass spectrometry imaging and MS/MS with and without ion mobility separation have been used for this purpose in a mouse fibrosarcoma model following treatment with the tubulin-binding tumour vascular disrupting agent, combretastatin A-4-phosphate (CA-4-P). Characterisation of peptides after in situ tissue tryptic digestion was carried out using Matrix-Assisted Laser Desorption/Ionisation-Mass Spectrometry (MALDI-MS) and Matrix-Assisted Laser Desorption/Ionisation-Ion Mobility Separation-Mass Spectrometry Imaging (MALDI IMS-MSI) to observe the spatial distribution of peptides. Matrix-Assisted Laser Desorption/Ionisation-Ion Mobility Separation-Tandem Mass Spectrometry (MALDI-IMS-MS/MS) of peaks was performed to elucidate any pharmacological responses and potential biomarkers. By taking tumour samples at a number of time points after treatment gross changes in the tissue were indicated by changes in the signal levels of certain peptides. These were identified as arising from haemoglobin and indicated the disruption of the tumour vasculature. It was hoped that the use of PCA-DA would reveal more subtle changes taking place in the tumour samples however these are masked by the dominance of the changes in the haemoglobin signals.     

Sterically induced conformational restriction: Discovery and preclinical evaluation of novel pyrrolo[3,2-d]pyrimidines as microtubule targeting agents

The discovery, synthesis and biological evaluations of a series of nine N5-substituted-pyrrolo[3,2-d]pyrimidin-4-amines are reported. Novel compounds with microtubule depolymerizing activity were identified. Some of these compounds also circumvent clinically relevant drug resistance mechanisms (expression of P-glycoprotein and βIII tubulin). Compounds 4, 5, and 8–13 were one to two-digit nanomolar (IC₅₀) inhibitors of cancer cells in culture. Contrary to recent reports (Banerjee et al. J. Med. Chem.2018, 61, 1704–1718), the conformation of the most active compounds determined by ¹H NMR and molecular modeling are similar to that reported previously and in keeping with recently reported X-ray crystal structures. Compound 11, freely water soluble as the HCl salt, afforded statistically significant inhibition of tumor growth in three xenograft models [MDA-MB-435, MDA-MB-231 and NCI/ADR-RES] compared with controls. Compound 11 did not display indications of animal toxicity and is currently slated for further preclinical development.     

Biological and anti-vascular activity evaluation of ethoxy-erianin phosphate as a vascular disrupting agent

The effects of ethoxy-erianin phosphate (EBTP) on cell proliferation, mitotic cell arrest, migration, infiltration, and endothelial tubular structures were evaluated in this study. The antiproliferative activity of EBTP and combretastatin A-4P (CA4P) was analyzed on several tumor cells (including MCF-7, HeLa, 2LL, and 2LL-IDO) and on an endothelial cell (human umbilical vein endothelial cells [HUVECs]) as well as a human normal liver cell (L02). The results showed that EBTP possessed antiproliferative activity in the micromole range and was relatively less toxic than CA4P. Treating HUVECs with EBTP caused cell accumulation in the G2/M phase, and wound-healing assays indicated that EBTP inhibited cell migration. Furthermore, EBTP and CA4P destroyed the vasculature in endothelial cells and showed vascular disrupting activity of the chorioallantoic membrane in fertilized chicken eggs. In addition, we found that EBTP suppressed the expression of indoleamine 2,3-dioxygenase (IDO) and significantly inhibited IDO-induced migration and infiltration of 2LL-IDO cells. Administration of EBTP blocked vasculogenic mimicry in 2LL-IDO cells, which was typically observed in tube formation assays of 2LL-IDO cells. Moreover, the results of Lewis lung carcinoma in mice showed a high inhibition rate of EBTP. EBTP is an effective vascular disrupting agent that is superior to CA4P and may prevent and treat malignancy by inhibiting the expression of IDO.     

Targeted-nanoliposomal combretastatin A4 (CA-4) as an efficient antivascular candidate in the metastatic cancer treatment

A number of antiangiogenic drugs have been approved by the Food and Drug Administration which are used in cancer therapy, and variety of other agents in several stages of clinical development or in preclinical assessment. Among these, combretastatin A4 (CA-4) is an under-researched inhibitor of angiogenesis that shows potential activity in the treatment of advanced tumors with migration capacity. However, its clinical application has been limited due to poor water solubility, low bioavailability, rapid metabolism, and systemic elimination. During the last decade, numerous investigations have been done to overcome these problems by using different CA-4 delivery systems or developing produgs of CA-4 or its structural analogs. Nevertheless, these strategies could not be efficient out of the undesired side effects on normal tissues. Nanoliposomal CA-4 not only benefits from the advantage of using liposomal drugs as opposed to free drugs but also can accumulate in the tumor site via specific targeting ligands, which leads to efficient targeting and enhancement of bioavailability. To the best of our knowledge, we consider an important attempt to understand different factors that might influence the CA-4 loading and release pattern of liposomes and the consequent results in tumor therapy. In this review, we shed light on various studied liposomal CA-4 formulations showing application thereof in cancer treatment.     

Design,synthesis and preclinical evaluation of 5-methyl-N4-aryl-furo[2,3-d]pyrimidines as single agents with combination chemotherapy potential

The design, synthesis and biological evaluation of 4-substituted 5-methyl-furo[2,3-d]pyrimidines is described. The Ullmann coupling of 5-methyl-furo[2,3-d]pyrimidine with aryl iodides was successfully optimized to synthesize these analogs. Compounds 6–10 showed single-digit nanomolar inhibition of EGFR kinase. Compounds 1 and 6–10 inhibited VEGFR-2 kinase better than or equal to sunitinib. Compounds 1 and 3–10 were more potent inhibitors of PDGFR-β kinase than sunitinib. In addition, compounds 4–11 had higher potency in the CAM angiogenesis assay than sunitinib. Compound 1 showed in vivo efficacy in an A498 renal xenograft model in mice. Multiple RTK and tubulin inhibitory attributes of 1, 4, 6 and 8 indicates that these compounds may be valuable preclinical single agents targeting multiple intracellular targets.     

A tumor vasculature targeted liposome delivery system for combretastatin A4: Design, characterization, and in vitro evaluation

The objective of this study was to develop an efficient tumor vasculature targeted liposome delivery system for combretastatin A4, a novel antivascular agent. Liposomes composed of hydrogenated soybean phosphatidylcholine (HSPC), cholesterol, distearoyl phosphoethanolamine-polyethylene-glycol-2000 conjugate (DSPE-PEG), and DSPE-PEG-maleimide were prepared by the lipid film hydration and extrusion process. Cyclic RGD (Arg-Gly-Asp) peptides with affinity for αvβ3-integrins expressed on tumor vascular endothelial cells were coupled to the distal end of PEG on the liposomes sterically stabilized with PEG (long circulating liposomes, LCL). The liposome delivery system was characterized in terms of size, lamellarity, ligand density, drug loading, and leakage properties. Targeting nature of the delivery system was evaluated in vitro using cultured human umbilical vein endothelial cells (HUVEC). Electron microscopic observations of the formulations revealed presence of small unilamellar liposomes of ∼120 nm in diameter. High performance liquid chromatography determination of ligand coupling to the liposome surface indicated that more than 99% of the RGD peptides were reacted with maleimide groups on the liposome surface. Up to 3 mg/mL of stable liposomal combretastatin A4 loading was achieved with ∼80% of this being entrapped within the liposomes. In the in vitro cell culture studies, targeted liposomes showed significantly higher binding to their target cells than non-targeted liposomes, presumably through specific interaction of the RGD with its receptors on the cell surface. It was concluded that the targeting properties of the prepared delivery system would potentially improve the therapeutic benefits of combretastatin A4 compared with nontargeted liposomes or solution dosage forms.     

3-(3-Methoxyphenyl)-6-(3-amino-4-methoxyphenyl)-7H-[1,2,4] triazolo [3,4-b][1,3,4] thiadiazine,a novel tubulin inhibitor,evokes G2/M cell cycle arrest and apoptosis in SGC-7901 and HeLa cells

Gastric cancer and cervical cancer are two major malignant tumors that threaten human health. The novel chemotherapeutic drugs are needed urgently to treat gastric cancer and cervical cancer with high anticancer activity and metabolic stability. Previously we have reported the synthesis, characterization and identification of a novel combretastatin A-4 analog, 3-(3-methoxyphenyl)-6-(3-amino-4- methoxyphenyl) -7H-[1,2,4]triazolo[3,4-b][1,3,4] thiadiazine (XSD-7). In this study, we sought to investigate its anticancer mechanisms in a human gastric cancer cell line (SGC-7901 cells) and human cervical carcinoma cell line (HeLa cells). The 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay showed that XSD-7 induced cytotoxicity in SGC-7901 and HeLa cells with inhibitory concentration 50 values of 0.11 ± 0.03 and 0.12 ± 0.05 µM, respectively. Immunofluorescence studies proved that XSD-7 inhibited microtubule polymerization during cell division in SGC-7901 and HeLa cells. Then, these cells were arrested at G2/M cell cycle and subsequently progressed into apoptosis. In further study, mitochondrial membrane potential analysis and Western blot analysis demonstrated that XSD-7 treatment-induced SGC-7901 cell apoptosis via both the mitochondria-mediated pathway and the death receptor-mediated pathway. In contrast, XSD-7 induced apoptosis in HeLa cells mainly via the mitochondria-mediated pathway. Hence, our data indicate that XSD-7 exerted antiproliferative activity by disrupting microtubule dynamics, leading to cell cycle arrest, and eventually inducing cell apoptosis. XSD-7 with novel structure has the potential to be developed for therapeutic treatment of gastric cancer and cervical cancer.     

New Combretastatin Analogs as Anticancer Agents: Design,Synthesis, Microtubules Polymerization Inhibition,and Molecular Docking Studies

A new series of 4-(4-methoxyphenyl)-5-(3,4,5-trimethoxyphenyl)-4H-1,2,4-triazole-3-thiol derivatives were synthesized as analogs for the anticancer drug combretastatin A-4 ( CA-4 ) and characterized using FT-IR, ¹H-NMR, ¹³CNMR, and HR-MS techniques. The new CA-4 analogs were designed to meet the structural requirements of the highest expected anticancer activity of CA-4 analogs by maintaining ring A 3,4,5-trimethoxyphenyl moiety, and at the same time varying the substituents effect of the triazole moiety (ring B ). In silico analysis indicated that compound 3 has higher total energy and dipole moment than colchicine and the other analogs, and it has excellent distribution of electron density and is more stable, resulting in an increased binding affinity during tubulin inhibition. Additionally, compound 3 was found to interact with three apoptotic markers, namely p53, Bcl-2, and caspase 3. Compound 3 showed strong similarity to colchicine , and it has excellent pharmacokinetics properties and a good dynamic profile. The in vitro anti-proliferation studies showed that compound 3 is the most cytotoxic CA-4 analog against cancer cells (IC₅₀ of 6.35 μM against Hep G2 hepatocarcinoma cells), and based on its selectivity index (4.7), compound 3 is a cancer cytotoxic-selective agent. As expected and similar to colchicine , compound 3 -treated Hep G2 hepatocarcinoma cells were arrested at the G2/M phase resulting in induction of apoptosis. Compound 3 tubulin polymerization IC₅₀ (9.50 μM) and effect on V_max of tubulin polymerization was comparable to that of colchicine (5.49 μM). Taken together, the findings of the current study suggest that compound 3 , through its binding to the colchicine-binding site at β-tubulin, is a promising microtubule-disrupting agent with excellent potential to be used as cancer therapeutic agent.