Anti-Cancer Agents in Medicinal Chemistry (Formerly Current Medicinal Chemistry - Anti-Cancer Agents) - Volume 18, Issue 4, 2018

Background: Use of natural agents is an upcoming area of research in cancer biology. Caffeic acid phenethyl ester (CAPE) has received great attention because of its therapeutic potential in various conditions including cancer. It is an active/abundant component of propolis, a honey bee hive product produced by bees using their enzyme-rich digestive secretions on resinous mix, bee wax and pollen from plants. It is used to protect the beehive against bacteria and other infections. Therefore a literature survey was done to understand the therapeutic potential of this compound. Although a lot of work has been done on chemotherapeutic aspects of CAPE and many reviews were available, yet its role as a radiomodulator was not clear. Objective: The objective of the review was to collect data on role of Caffeic acid phenethyl ester as radioprotector and /or sensitizer to evaluate its potential as modulator of radiation effects during cancer therapy. Methods: For literature survey, Pubmed and Google search engines were used. Data were collected up to August 2017. PubMed advanced search builder showed 845 papers on CAPE. This search was further narrowed down to synthesis, bioavailability, CAPE derivatives, radioprotective and radiosensitizing effects of CAPE. Results: This review focused on the differential radiomodulatory effects of CAPE in normal and cancer cells. Besides chemistry and bioavailability, it's potential as a therapeutic agent against radiation induced damage was also evaluated. Conclusion: CAPE was found to act both as radioprotector and radiosensitizer. Depending on the tissue type it can modulate the radiation response by following different mechanisms.

The constant search for successful cancer therapies lasts for decades. Apart from the huge scientific effort and enormous sum of spent money, only a small amount of newly developed medicines move into clinical use (only 94 registered anticancer drugs in the last 12 years). Anticancer regimes are still overcome by drugs invented over 50 years ago such as cisplatin and doxorubicin. Significant progress in the development of improved anticancer drugs was made due to multiple studies on the relationship between the molecular structure of chemical compounds and their cytostatic activity. A number of ligands (mainly organic) with quite effective anticancer properties are known, but they show insufficient activity, selectivity and multidrug resistance. Formation of transition metal – ligand complexes (with proven anticancer effect) changes the properties of the latter. The factors that affect the cytotoxic properties of metal complexes are: the type of ligand and metal, the nature of the connection between metal and ligand, and the distribution of electronic charge density in the formed complexes. Here, we report the recent efforts to improve existing compounds with confirmed anticancer activity. They seem to be unappreciated as their effects appear to be less spectacular than that of targeted anticancer drugs (i.e. based on antibodies or small RNAs).

Cancer is the second leading cause of death worldwide. There is always a huge demand for novel anticancer drugs and diverse new natural or synthetic compounds are developed continuously by scientists. Presently, a large number of drugs in clinical practice have showed pervasive side effect and multidrug resistance. Sulfonyl or sulfonamide hybrids became one of the most attractive subjects due to their broad spectrum of pharmacological activities. Sulfonyl hybrids were broadly explored for their anticancer activities and it was found that they possess minimum side effect along with multi-drug resistance activity. This review describes the most recent applications of sulfonyl hybrid analogues in anticancer drug discovery and further discusses the mechanistic insights, structure-activity relationships and molecular docking studies for the potent derivatives.

Receptors of glutamic acid are known for over 30 years for their action and for about 20 years for their structure. Presence of at least three classes of ionotropic receptors was confirmed at the beginning of 80'. Recognition of the sequence and first cloning were done at the beginning of 90'. In 1994 ligand binding site was recognized at the junction of two subunits S1-S2 in the ligand-binding domain. Since then, many subtypes of ionotropic and metabotropic glutamate receptors were recognized, together with their localization and functions. In the meantime numerous orthosteric ligands, both agonists and antagonists were developed especially for NMDA ion channels. Their usefulness as drugs was rather low, due to the involvement in the excitatory tract. More interest was focused on metabotropic receptors, which are GPSR's and can be modulated both by orthosteric and allosteric modulators. It seems like allosterism could be considered as promising future for glutamate receptors and ion channels, especially when first allosteric negative modulators of the mGluR2 went close into the clinical trial.

Background: An ideal strategy for cancer treatment is the specific induction of tumor cell death, sparing normal cells. Marine sponges are rich biological reservoirs of biomolecules, especially lectins, which have attracted considerable attention due to potential biological effect on human cells. Lectins are proteins that bind specific carbohydrate signatures and some gained further interest for their capacity to bind tumor associated carbohydrates antigens and induce tumor cell apoptosis. Objective: This study aimed to evaluate the antitumor potential of H3, a lectin, recently reported from marine sponge Haliclona caerulea on the human breast cancer cell line MCF7. Results: H3 reduced MCF7 cell viability with an IC50 of 100 μg/ml, without a significant effect on normal cells. At 24 h, H3 induced a significant arrest in the G1 cell cycle phase. Consistently, almost 50% of the cells were in early apoptosis and showed remarkable increased expression of caspase-9 (CASP 9). H3 impaired dramatically the adhesiveness of MCF7 cells in culture. Assays conducted with Lysotracker Red probe showed increased organelle acidity, suggesting autophagic cell death, which was further supported by increased expression of microtubuleassociated protein light chain 3 (LC3) and observable conversion of LC3-I in LC3-II by western blot. Conclusion: The apoptotic effect of H3 may be related to a balance between apoptotic and autophagic cell death, mediated by increased expression of CASP 9 and LC3-II. To the best of our knowledge this is the first report about a sponge lectin triggering both apoptosis and autophagy in MCF7 cell.

Objective/Method: A group of 4-benzoyl-1-dichlorobenzoylthiosemicarbazides endowed with antibacterial activity was evaluated for its cytotoxic properties against breast cancer cells (MCF-7, MDA-MB-231) and head and neck squamous cell carcinomas (FaDu, SCC-25). Cytotoxicity of the investigated compounds was measured using MTT and [3H]-thymidine incorporation bioassays. Result: 1-(2,3-Dichlorobenzoyl)-4-(2-methylbenzoyl)thiosemicarbazide (TA-4), 1-(2,4-dichlorobenzoyl)- 4-(2-methylbenzoyl)thiosemicarbazide (TA-18), and 1-(2,4-dichlorobenzoyl)-4-(4-nitrolbenzoyl)- thiosemicarbazide (TA-20) were found to possess anticancer activity equipotent or even stronger than that of reference drug – etoposide. In order to clarify the molecular mode of action of the mentioned compounds, the relaxation assay kit for human DNA topoisomerase II was used. It turned out that reduction of viability of cancer cells was a result of inhibition of human DNA topoII. Molecular docking studies proved that 4-benzoyl-1-dichlorobenzoylthiosemicarbazides strongly interact with DNAdependent subunit of that enzyme.

Background: NF-ΚB is a transcription factor involved in the transcriptional regulation of a large number of genes related to tumorigenesis in several cancer cell types, and its inhibition has been related to anticancer effect. DHMEQ (Dehydroxymethylepoxyquinomicin) is a compound that blocks the translocation of NF-ΚB from the cytoplasm to the nucleus, thus inhibiting its activity as a transcriptional activator. Several studies have shown the antineoplastic effects of DHMEQ in numerous tumor types, however, there are no surveys that tested their effects in MB. Objectives: The aim of the present study was to evaluate the effects of DHMEQ as NF-ΚB inhibitor in pediatric MB cell lines. Method: We used the UW402, UW473 and ONS-76 medulloblastoma (MB) cell lines to verify the effect of DHMEQ on proliferation, clonogenic capacity, apoptosis, cell invasion and migration, and evaluated the effect of the combination with other drugs and the potential as a radiosensitizator. Results: A significant decrease in the cell growth, a strong inhibition of the clonogenic capacity, migration and cell invasion was observed after NF-ΚB inhibition in the three MB cell lines. Conversely, increased level of apoptosis rates were demonstrated. Additionally, treatments with DHMEQ combined with other chemotherapeutic agents were synergic in most points, and a strong radiosensitization by this compound was observed in the three MB cell lines. Conclusion: DHMEQ has potential antitumor effect on MB cells, and it may be considered a new therapeutic agent to improve treatment approaches in MB.

Background: Osimertinib (OSI), also known as AZD9291, is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that has been approved for the treatment of non-small cell lung cancer (NSCLC) patients. Objective: Establishment of the OSI-resistant HCC827/OSIR cell line and study of its resistant mechanism. Method: The anti-proliferative effect was studied through MTT and colony formation assays. The protein expression was detected by Western blot assay. The gene was silenced by small interfering RNA. The cellular morphology was observed by using an optical microscope. The viable cell numbers were counted by trypan blue staining assay. Results: The OSI-resistant HCC827/OSIR cells were established on HCC827 cells with naive EGFR-sensitive mutation, and the resistant effects of HCC827/OSIR cells were confirmed through MTT and colony formation assays. The IC50s of HCC827/OSIR cells to other EGFR TKIs, such as gefitinib, erlotinib, afatinib, and rociletinib was higher than that of the HCC827 cells. The anti-proliferative effects of paclitaxel, pemetrexed, doxorubicin, and fluorouracil in HCC827 and HCC827/OSIR cells were similar. The expression of inositolrequiring enzyme 1α (IRE1α) was increased after the cells developed resistance to OSI. The number of viable cells in both cell lines, particularly in HCC827/OSIR cells, was decreased through knockdown of IRE1α or pretreatment with STF-083010, an IRE1α inhibitor. Conclusion: An increased expression of IRE1α may be one of the resistant mechanisms for OSI-resistant NSCLC.

Background: Naphthalene is a good structural replacement for the isovanillin moiety (i.e. the 3- hydroxy-4-methoxyphenyl unit) in the combretastatin A-4 molecule, a natural product structurally related to resveratrol, which consistently led to the generation of highly cytotoxic naphthalene analogues when combined with a 3,4,5-trimethoxyphenyl or related aromatic system. Also, the naphthalene ring system is present in many current drug molecules that are utilized for anti-tumor, anti-arrhythmia and antioxidant therapy. Objective: In our continuing quest to improve the potencies of naturally occurring anti-cancer molecules through chemical modification, we have now synthesized a small library of 2-naphthaleno trans- stilbenes and cyanostilbenes that are structurally related to both resveratrol and DMU-212, and have evaluated these novel analogs against a panel of 54 human tumor cell lines. Method: A series of 2-naphthaleno-containing trans-stilbenes 3a-3h (Scheme 1) were synthesized by Wittig reaction of a variety of aromatic substituted benzyl-triphenylphosphonium bromide reactants with 2- naphthaldehyde using n-BuLi as a base in THF. A second series of 2-naphthaleno trans-cyanostilbenes analogs 5a-5h was synthesized by reaction of 2-naphthaldehyde (2; 1 mmol) with an appropriately substituted 2- phenylacrylonitrile 4a-4h; 1 mmol) in 5% sodium methoxide/methanol. The reaction mixture was stirred at room temperature for 2-3 hours and the reaction allowed to go to completion (TLC monitoring), during which time the desired product precipitated out of the solution as a solid. The resulting precipitate was filtered off, washed with water and dried to yield the desired compound in yields ranging from 70-95% (Scheme 2). Results: The percentage growth inhibition of 54 human cancer cell lines in a primary NCI screen after exposure to compounds 3a, 3d, 5b and 5c was carried out. The results showed that only compounds 5b and 5c met the criteria for subsequent testing to determine growth inhibition values (GI50) in dose-response studies. At 10-5 M concentration, compounds 5b and 5c exhibited cytotoxic activity against leukemia cell lines HL-60(TB) and SR, lung cancer cell line NCI-H522, colon cancer cell lines COLO 205 and HCT-116, CNS-cancer cell line SF-539, melanoma cell line MDA-MB-435, and breast cancer cell line BT-549. The naphthalene trans-stilbene analogue 3a, exhibited significant growth inhibition against only one cell line, melanoma cell line MDA-MB-435 (96 % growth inhibition). Compound 3d was inactive in the 10-5 M single dose screen. Conclusion: We have synthesized a small set of novel 2-naphthaleno stilbenes and cyanostilbenes and evaluated several of these compounds for their anticancer properties against a panel of 54 human tumor cell lines. The most active analogs, 5b and 5c, showed significantly improved growth inhibition against the human cancer cells in the NCI panel when compared to DMU-212. Of these compounds, analog 5c was found to be the most potent anticancer agent and exhibited significant growth inhibitory effects against COLO 205, CNS SF 539 and melanoma SK-MEL 5 and MDA-MB-435 cell lines with GI50 values ≤ 25 nM. Analog 5b also exhibited GI50 values in the range 25-41 nM against CNS SF 295 and melanoma MDA-MB-435 and UACC-62 cell lines. Compounds 5b and 5c were also cytotoxic towards the MV4-11 leukemia cell line with LD50 value of 450 nM and 200 nM, respectively, and demonstrated >50% inhibition of tubulin polymerization at concentrations below their LD50 values in these cells. In silico docking studies suggest that compounds 5b and 5c bind favorably at the colchicine- binding pocket of the tubulin dimer, indicating that both 5b and 5c may inhibit tubulin polymerization through a mechanism similar to that exhibited by colchicine. Derivative 5c demonstrated more favorable binding based on the docking score and buried surface area, as compared to compound 5b, in agreement with the higher observed potency of 5c against a broader range of tumor cell lines. Based on these results, analog 5c is considered to be a lead compound for further optimization as a clinical candidate for treating a variety of cancers.

Background: Regardless of contemporary improvements in cancer treatment, the results of drug treatment are not always efficacious. Thus, the development of novel approaches that affect cancer cell-specific metabolic pathways is needed. Since much evidence has shown that tumor cell proliferation and motility are stimulated by glutamate via activation of its receptors, use of antagonists to these receptors may be the key to control cancer cell progression. Riluzole noncompetitive metabotropic glutamate receptor 1 (mGluR1) antagonist, commonly used to treat patients with amyotrophic lateral sclerosis (ALS), has shown some antineoplastic properties against melanoma, breast and prostate cancer. Yet little is known about its molecular mode of action. Aims: The current study aims at evaluating the abilities of Riluzole to inhibit proliferation of several cancer cell lines, as well as resolve the mechanism of its action. Method: We demonstrated antiproliferative and antimigrative properties of Riluzole in rhabdomyosarcomamedulloblastoma, neuroblastoma, astrocytoma, glioma, colon cancer, lung cancer, thyroid carcinoma, leukemia, erythroleukemia and multiple myeloma. Our studies revealed apoptosis induction and G2-M cell cycle arrest in Riluzole treated A549, C6 and HT-29 cells. Result: At the molecular level, we found that these cells treated with Riluzole had a decrease of Cyclin B and an increase of p21 Waf1/Cip1 and p53 expression. We also observed an enhancement of CDK1 and Chk2 phosphorylation. Reported changes may suggest the involvement of these proteins in G2-M arrest, observed in flow cytometry analysis. These data indicated the potential use of Riluzole in the treatment of different types of cancers.

Background: Some 2-thioxoimidazolidinones have been reported as anti-prostate and anti-breast cancer agents through their inhibitory activity on topoisomerase I that is considered as a potential chemotherapeutic target. Objective: A new series of 3,5-disubstituted-2-thioxoimidazolidinone derivatives 10a-f and their S-methyl analogs 11a-f were designed, synthesized and evaluated for cytotoxicity against human prostate cancer cell line (PC-3), human breast cancer cell line (MCF-7) and non-cancerous human lung fibroblast cell line (WI-38). Results and Method: While compounds 10a-f showed a broad range of activities against PC-3 and MCF-7 cell lines (IC50 = 34.0 – 186.9 and 24.6 – 147.5 μM respectively), the S-methyl analogs 11a-f showed (IC50 = 22.7 – 198.5 and 16.9 – 188.2 μM respectively) in comparison with 5-fluorouracil (IC50 = 60.7 and 40.7 μM respectively). 11c (IC50 = 22.7 and 29.2 μM) and 11f (IC50 = 28.7 and 16.9 μM) were the most potent among all compounds against both PC-3 and MCF-7 respectively with no cytotoxicity against WI-38. Conclusion: The newly synthesized compounds showed good activity against PC-3 and MCF-7 cell lines in comparison with 5-fluorouracil. Compounds 11c and 11f bound with human topoisomerase I similar to its known inhibitors and significantly inhibited its DNA relaxation activity in a dose dependent manner which may rationalize their molecular mechanism as cytotoxic agents.

Background: Angiogenesis is a crucial process that regulated by multiple intracellular signaling pathways including MEK/ERK and JNK/SAPK. Thus, many inhibitors have developed to these pathways as anti-cancer therapeutic strategies. Oleanolic acid (OA) is a natural pentacyclic triterpenoic acid compound that present in various herbal medicines. It has been used as antitumor agent for various cancers including colorectal cancer (CRC), which attenuates angiogenesis. Objective: To study the molecular mechanism of OA suppressing angiogenesis. Method: The proliferation of human umbilical vein endothelial cells (HUVECs) was determined by MTT and the invasion and migration of them were measured by wound-healing Assay, transwell migration assay and tube formation assay. The xenograft mouse model was used to study the effect of OA blocking angiogenesis in vivo. The Western blot was used to checked the phosphorylation of VEGFR2. Results: OA attenuates HUVECs invasion, migration, tube formation and vascular sprouting. Moreover, OA suppresses HUVECs sprout and tube formation. Importantly, OA also blocks angiogenesis in HUVECs and colorectal cancer cells (HCT-116) both in vitro and in vivo. OA-dependent suppression of tumor angiogenesis mediated by blocking the phosphorylation of the vascular endothelial growth factor receptor-2 (VEGFR2) that results in inhibition of MEK/ERK/JNK pathway. Conclusion: Our results suggest that inhibition of tumor angiogenesis via the suppression VEGFR2 phosphorylation may be one of the underlying mechanisms by which OA exerts its anti-cancer effect.

Background: Glutamate receptors are widely expressed in different types of cancer cells. α-Amino-3- hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors are ionotropic glutamate receptors which are coupled to intracellular signaling pathways that influence cancer cell survival, proliferation, and migration. Blockade of AMPA receptors by pharmacologic compounds may potentially constitute an effective tool in anticancer treatment strategies. Method: Here we investigated the impact of the AMPA receptor antagonist CFM-2 on the expression of the protein survivin, which is known to promote cancer cell survival and proliferation. We show that CFM-2 inhibits survivin expression at mRNA and protein levels and decreases the viability of cancer cells. Using a stably transfected cell line which overexpresses survivin, we demonstrate that over-expression of survivin enhances cancer cell viability and attenuates CFM-2–mediated inhibition of cancer cell growth. Result: These findings point towards suppression of survivin expression as a new mechanism contributing to anticancer effects of AMPA antagonists.

Background: Liposomal doxorubicin is widely used for treating ovarian cancer and Kaposi's sarcoma. Encapsulation of doxorubicin in highly complex polyethylene glycol–coated (stealth) liposomes prolongs residence time and avoids the systemic toxicity associated with administration of the free drug. Small variations in physicochemical properties introduced during manufacture of liposomes can influence the payload of encapsulated drug, stability of liposomes under physiological conditions, and release of drug at the target tissue. Accordingly, the US Food and Drug Administration and the European Medicines Agency have issued guidance for manufacturers of generic liposomal doxorubicin that is designed to ensure that more than 30 physicochemical parameters that influence its safety and efficacy should be similar in the generic and reference listed drugs. Objective: This study aims to describe the physicochemical characterization procedures used to ensure consistency between batches of generic liposomal doxorubicin and with the reference listed drug. Methods: A range of spectroscopic, chromatographic, and other physicochemical tests was used to compare relative concentrations of liposome components, liposome morphology, ratios of free/entrapped doxorubicin, stability, and in vitro doxorubicin release rates in physiologically and clinically relevant media. Results: The tests established that generic and reference liposomes contained similar concentrations of drug, lipids, and excipients and that their physical forms were also similar. Conclusion: The results of the tests demonstrate the physicochemical equivalence of generic liposomal doxorubicin hydrochloride and the reference listed drug, Doxil®/Caelyx®. Biochemical and clinical equivalence must also be demonstrated to fully meet regulatory requirements for generic liposomal medicines, and these are the subjects of separate studies.

Introduction: In the present study, we analyzed anti-proliferative and apoptosis induction activity of five phenolic compounds: echisoside, pleoside, chlorogenic acid, 4,5-Di-O-caffeoylquinic acid, and cynarin on AGS (adenocarcinoma gastric) cell line. Method: These phenolic compounds were isolated from methanol extract of Dorema glabrum root. An MTT assay was conducted to evaluate the inhibitory effect on cancer cells. EB/AO staining was done to assess the mode of cell death and morphological changes of the cells' nuclei. Cell cycle distribution of the cells was analyzed by flow cytometry, and for further confirmation of the pathway, mRNA levels of apoptosis cascade players were quantified by qRT-PCR. Result: We found that echisoside, pleoside, chlorogenic acid, 4,5-Di-O-caffeoylquinic acid, and cynarin inhibited the proliferation of AGS cancer cells in vitro. Our data revealed that these compounds triggered morphological changes characteristic of apoptotic cell death. These compounds up-regulated bax and caspase3 expression and down-regulated cyclin D1, bcl2, VEGFA, c-myc and survivin. Moreover, cell population increased at the G1 phase, and a number of cells at the G2/M phase of the cell cycle decreased after treatment. Conclusion: All these data suggest that phenolic compounds have a cytotoxic effect on gastric cancer cells and could trigger apoptosis. Besides cytotoxic activity, they could potentially arrest the cell cycle at the G1 phase.

Background: Hypoxia renders tumor cells refractory to treatment. One way to overcome this problem is the design of drug delivery systems that contain the antitumor agent within an oxygen supply medium. Objective: to evaluate whether the perfluorocarbon liquids (capable of retaining up to 50% v/v amounts of O2 gas) can be tools for delivery of photosensitizers to hypoxic tumors. Method: We synthesized a series of compounds in which fluoroaliphatic or fluoroaromatic moieties were conjugated to the porphyrin ring in meso-positions. Two derivatives were tested as the solutions prepared either from a dimethylformamide stock (‘free’ formulation) or from a perfluorocarbon emulsion in which the photosensitizer is entrapped in the oxygenated medium. Results: In the emulsion the hydrophobic photosensitizer and the gas transporting liquid represented a biocompatible composition. Free formulations or perfluorocarbon emulsions of fluorinated porphyrins evoked little-to-null dark cytotoxicity. In contrast, each formulation triggered cell death upon light activation. Photodamage in the presence of fluorinated porphyrins was achievable not only at normoxic (20.9% O2 v/v) conditions but also in hypoxia (0.5% O2). With new compounds dissolved in the medium the cell photodamage in hypoxia was negligible whereas a significant photodamage was achieved with the emulsions of fluorinated porphyrins. The derivative with the fluoroalkyl substituent was more potent than its structurally close analog carrying the fluoroaryl moiety. Conclusion: Our new fluorinated porphyrin derivatives, especially their emulsions in which the photosensitizer and the oxygenated medium are coupled into one phase, can be perspective for photoelimination of hypoxic tumor cells.