Anti-Cancer Agents in Medicinal Chemistry (Formerly Current Medicinal Chemistry - Anti-Cancer Agents) - Volume 16, Issue 12, 2016

The partial efficacy and high toxicity of the current anticancer chemotherapeutics as well as the development of multiple drug resistance are the major problems in cancer therapy. Therefore, there is an emergency need for the development of novel well-tolerated anticancer agents with different mode of action that could be successfully used in combination with other drugs as an adjuvant therapy. The inhibition of intracellular signaling pathways associated with cancer growth and invasiveness is a main therapeutic approach in cancer treatment. It is well known that lipid metabolism is involved in the regulation of key cellular processes such as proliferation, differentiation and apoptosis. Statins and alkylphospholipids are both relatively new synthetic agents with considerable anticancer properties that disturb lipid metabolism and subsequently modulate proliferation and cell survival signaling pathways, leading to apoptosis. Numerous in vitro and in vivo studies have shown promising results for the use of statins and alkylphospholipids as potential therapeutic agents in the treatment of various human malignancies. However, more investigations and clinical trials are needed to assess their optimal safe dose and maximal efficacy and better understand the molecular mechanisms underlying the antitumor effects of these drugs.

Despite constant advances on breast cancer knowledge, the metastatic disease resulting from the spreading of this disease is still a challenge. This scenario is particularly critical in the more aggressive subtypes, as HER2-amplified and triple negative breast cancers, when often occurs the invasion of central nervous system (CNS) structures. In this situation, the survival of patients is drastically reduced, and the number of sequels and functional impairment is huge due to the small therapeutic arsenal available. In this context, it is necessary to understand the mechanisms involved in the process of metastasis of breast cancer to CNS, and how this process affects anatomically important structures for its functioning. This review aims to point out some mechanisms enrolled in the spread of breast cancer to CNS, discuss the clinical impact of such metastatisation and address the critical aspects related to the treatment of this condition.

As the ever more critical role of individualized therapy in the cancer treatment and management, circulating tumor cells (CTCs) have caught much attention for providing a promising way in metastases establishment, disease diagnosis and prognosis. Also, their presence has been generally considered as the rationale behind the application of systemic adjuvant chemotherapy. Therefore, CTCs open a new window for the clinical utility, especially for the diagnosis and evaluation of cancer, and move toward personalized medicine. In this review, we summarize the pros and cons of current available technologies for enrichment and detection of CTCs comprehensively. In addition, recent advances in the development of microfluidic and nanotechnology for isolation of CTCs are outlined. Furthermore, circulating tumor microemboli (CTM)-based and telomerase-based assays, the emerging methods for CTC detection and the application of CTCs in the clinic, have also been evaluated. Finally, perspectives and challenges of all these methods in the field of CTCs’ isolation and detection are presented.

Development of resistance in cancer cells results in a high failure rate in cancer chemotherapy in the clinic. Therefore, investigating the mechanisms by which cancer cells acquire the capability to avoid cell death upon exposure to antineoplastic agents is of great significance in cancer research. In this review article, we will provide an overview of the mechanisms and molecular machinery of drug resistance in cancer cells which include but may not be limited to altered membrane transport and drug metabolizing enzymes, genetic response, enhanced DNA repair and alternation in the target molecules. A special focus will be on describing the strategies and the rationale for exploitation of peroxisome proliferator-activated receptors for overcoming the observed resistance in cancer cells.

Marine ecosystem represents a wide and untapped reservoir of biologically active metabolites. Most of the sponges, seaweeds, crustaceans, fish species and their associated microorganisms have evolved chemical means in order to defend themselves against predation and to survive in the complex marine environment. Such chemical and biological adaptation produced many bioactive substances with beneficial effects on human health, including potential anticancer agents. With further exploration of sea and ocean environment, several marine bioactives have been identified with promising anticancer activity. More than one hundred novel bioactive compounds with antitumor activity and their synthetic derivative substances displayed in vitro cytotoxic property on neoplastic cell lines and are currently gaining great attention for further evaluations and in vivo applications. This review highlights novel marine molecules and compounds which have been able to inhibit different cancer species in the recent years and aims to describe research on new natural antineoplastic agents obtained from sea world.

The Ras/Raf/MEK/ERK signaling pathway involves various kinases in which each kinase is associated with one another through signals and regulates cell proliferation, differentiation and apoptosis. This pathway is dysregulated almost in all cancers due to the amplification and genetic mutation of various components of the pathway. The genetic mutations have been reported to cause drug resistance to the current chemotherapy of melanomas. B-Raf is one of the most commonly mutated proto-oncogenes and plays a significant role in the development of numerous cancers of high clinical impact. Therefore, mutant B-Raf kinase may be a promising therapeutic target for the development of novel anticancer drugs. Many BRAF inhibitors discovered during the last decade showed promising anticancer activity, especially on tumors that harbor BRAFV600E mutations. Currently, vemurafenib and dabrafenib are USFDA approved drugs used as B-Raf inhibitors. Few drugs which are under clinical development phases such as LGX818, GDC0879, XL281, ARQ736, PLX3603 (RO5212054), and RAF265 etc. pave the path for further designing of B-Raf inhibitors. The present review focuses primarily on the Ras/Raf/MEK/ERK signaling pathway with mutant B-Raf as a therapeutic target for anticancer drug development. The essential pharmacophoric features of B-Raf inhibitors, their structure activity relationships (SARs) and molecules under clinical trials have been highlighted.

Background: hepatocellular carcinoma (HCC) is the third cause of mortality due to cancer throughout the world. Objective: The main goal of the current research was to evaluate the selective toxicity of apigenin (APG) on hepatocytes and mitochondria obtained from the liver of HCC rats). Method: In this research, HCC induced by a single dose of diethylnitrosamine (DEN); 200 mg/kg, i.p, and 2-acetylaminofluorene (2-AAF) (0.02%, through dietary) for 14 days. For confirmation of HCC, histopathological evaluations and determination of serum concentrations of liver toxicity enzymes and specific liver cancer marker; alpha-fetoprotein (AFP) were performed. Then, cancerous and non- cancerous hepatocytes were isolated by using the collagen perfusion method. Eventually, mitochondria isolated from HCC and normal hepatocytes were tested for every eventual toxic effects of APG. Results: After confirmation of HCC, the results of this research showed that APG (10, 20 and 40 μM) increased mitochondrial parameters such as, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) level, mitochondrial swelling and cytochrome c expulsion only in cancerous hepatocytes. Apoptotic effect of APG on HCC cells was confirmed by caspase-3 activation and Annexin V-FITC and PI double staining analysis. Conclusion: These results propose the eligibility of the flavonoid APG as a complementary therapeutic agent for patients with hepatocellular carcinoma.

A series of 15 derivatives of xanthone were synthesized and evaluated for the anticancer activity. The structure of the tested compounds was diversified to establish structureactivity relationships. The following evaluations were carried out: cytotoxicity-proliferation tests, apoptosis detection, expression of apoptosis and proliferation-related genes, expression and activity of gelatinases A and B, wound migration assays, and cell adhesion to MatrigelTMcoated plates. Four compounds (7, 12, 13 and 15) displayed direct cytotoxicity at micromolar concentrations toward the studied cell lines. They also significantly affected the expression of proliferationapoptosis markers, and 13 demonstrated as strong influence as α-mangostin, that served as a natural standard in our study. These four compounds also decreased the expression and activity of gelatinases, and inhibited the migration-motility potential of cancer cells. The influence of compounds 7 and 12 on MMPs mRNA levels even exceeded the activity of α-mangostin and shRNA-mediated silencing; zymography revealed that 7, 13 and 15 were as equally active as α-mangostin, despite their higher IC50 values. The highest activity to inhibit motility and migration of cancer cells was demonstrated by 7, 12, 15, and by α-mangostin; and this was almost equal to shRNA-mediated silencing. Structural features predetermining compound activity were: substitution at position C4 instead of C2, and presence of a chlorine atom and allyl moiety. These results indicate that synthesis of aminoalkanol derivatives of xanthone may lead to successful establishment of new potential anticancer chemicals.

Inhibition of the 26S proteasome is an attractive approach for anticancer therapy. Proteasome inhibitors are known to selectively target cancer cells and make them more sensitive to chemotherapeutic agents. Murraya koenigii is a medicinally important herb of Asian origin and a rich source of bioactive compounds such as flavonoids and alkaloids. In the present study, we investigated the proteasome inhibitory and apoptotic effect of M. koenigii leaf extract in vivo in a xenograft tumor mouse model, and also assessed the toxicity if any in normal mice. M. koenigii extract did not lead to any toxicity in mice. Analysis of extract revealed the presence of flavonoid compounds which act as proteasome inhibitors. Quercetin treatment led to the decrease in the cell viability and arrest of cells in G2/M phase. Quercetin, Apigenin, Kaempferol and Rutin; flavonoids present in the leaf extract, dose-dependently inhibited the endogenous 26S proteasome activity in MDA-MB-231 cells. Reduction in tumor growth was associated with a decrease in proteasomal enzyme activities in the treated groups. Increased caspase-3 activity and TUNEL-positive cells indicated enhanced apoptosis with Murraya leaf extract treatment. Decreased expression of angiogenic and anti-apoptotic gene markers is indicative of inhibition of angiogenesis and promotion of apoptosis in the leaf extract treated tumors.

Thiol reagents were shown to act as potent inhibitors of L5178-Y murine leukemia cell proliferation. A series of aryl maleimides (AMI) was synthesized and evaluated theoretically for global and local reactivity, showing their selectivity for thiol groups, due to a reaction of the vinyl moiety (a soft acid) with thiols (a soft base). Two AMI that are benzoic acid derivatives (1f and 1h) were tested with an in vitro and ex vivo model to evaluate their reactivity with thiols and their activity in L5178-Y cells. The in vitro reactions clearly showed a selective Michael type 1,4-addition reaction between thiols (glutathione and N-acetylcysteine, which are nucleophiles) and the AMI (1f and 1h, which are electrophiles). In cell cultures, the compounds induced a decreasing cellular viability and an apoptotic effect of up to 59.8% at 48 h. The ex vivo experimental model showed an important reduction of thiol levels in cells treated with 1h. Decreased cellular viability and increased apoptosis were confirmed by flow cytometry, DNA fragmentation and microscopy analysis (cytological studies). The increase in apoptosis on L5178-Y cells probably occurred, at least in part, by a decrease in glutathione levels and an increase in free radicals concentration. The decreased glutathione levels seem to make cancer cells more susceptible to death by apoptosis, and should certainly make them more vulnerable to a less aggressive treatment.

A novel synthetic method of 4-substituted aryl-1H-1,2,3-triazoles from arylglyoxaldoxime semicarbazone with sodium dithionite and O2 was found to be safer than the Huisgen azide– alkyne dipolar cycloaddition. A total of 17 new structures of 4-substituted aryl-1H-1,2,3- triazoles were characterized by 1H NMR, 13C NMR, ESI-MS. Subsequently, their in vitro antihepatoma activities were evaluated on human hepatoma QGY-7703, Bel-7402 and SMMC-7721 cell lines and mouse fibroblast cells L-929 by MTS assay. Among them, 5k exhibited excellent activity against QGY-7703 (GI50 = 0.0232 μM), while 5p and 5q displayed good activity (GI50 = 0.103 μM and GI50 = 0.182 μM) against the growth of SMMC-7721 cell lines. Furthermore, 5k, 5p and 5q showed slight selectivity of inhibition on hepatoma cell lines over normal cell line L-929.

In vitro biological studies of four trans-platinum complexes of structural formulas trans-[PtCl2(n-acetylpyridine)2] (n = 3 or 4, complex 1 or 2) and [Pt(n-acetylpyridine)2Cl4] (n = 3 or 4, complex 3 or 4) were performed in human endothelial EA.hy 926 cells, in order to evaluate and compare their cytotoxic and antiangiogenic potential. MTT results revealed that trans-Pt(II) complexes exhibited significantly lower IC50 values: 4.0±0.9 μM (1) and 2.1±0.0 μM (2), than cisplatin (27.7±1.3 μM). Combinational drug treatment with N-Acetyl-L-cysteine and L-buthioninesulfoximine strongly counteracted effect of 1 and 2, while the same treatment rather enhanced cytotoxicity of Pt(IV) analogues. ICP-MS results suggested that differential endothelial toxicity of cisplatin and trans-platinum complexes correlated to the differences in their cellular accumulation, rather than to the different affinity of DNA binding. Intracellular accumulation of complexes (ng Pt/106 cells) for 24 h treatment, decreased in order: 1>2>4>3>CDDP, while ratio of DNA binding (pg Pt/μg DNA) decreased as following: 2>1>CDDP>4>3. FACS/Annexin-V-FITC analysis, and morphological study demonstrated that the enhanced cytotoxic and apoptotic potential (18.1%) of complex 2 was related to its highest affinity to bind nuclear DNA. Pt(IV) complexes exhibited the lowest reactivity to cellular DNA and proteins. Regardless of their antiproliferative action, 1-4 at subtoxic concentrations demonstrated in vitro inhibitory effect on tubulogenesis and matrix metalloproteinases (MMPs) 2 and 9 gelatinolitic activity, while 1 and 2 additionally downregulated MMP-2 gene expression.

Background: GW843682X is a publicly available anti-cancer compound by inhibiting Polo-like kinase. Previous studies revealed that GW843682X inhibited the proliferation of various tumor cell lines. In this study, the cytotoxic effect of GW843682X was investigated on cell proliferation, cell cycle and apoptosis of nasopharyngeal carcinoma 5-8F cells. Methods: Cell morphological changes were observed by inverted microscopy. Cell proliferation was tested by CCK8 assay. Cell cycle arrest and apoptosis were tested by flow cytometry. The mechanism of apoptosis was investigated by RT-PCR to determine the mRNA expression of IAP-1, IAP-2, XIAP, and survivin. Results: GW843682X resulted in remarkable cell morphological changes with the increase of drug concentrations. CCK8 assay revealed that GW843682X inhibited the proliferation and induced apoptosis of 5-8F cells in a dose-dependent manner (IC50=62.5-125nmol/L). After treating 5-8F cells with different doses of GW843682X for 12 h, G2/M phase cells significantly increased while G0/G1 phase cells remarkably decreased. Interestingly, GW843682X signi#129;cantly inhibited the mRNA expression of IAP-1 and survivin, which function as key regulators of mitosis and programmed cell death, and is overexpressed in many tumor types. The mechanism of cytotoxic effect is partially due to the inhibition of IAP gene expression. Conclusion: These findings indicated that GW843682X exhibited remarkable cytotoxic effects on nasopharyngeal carcinoma 5-8F cells by down-regulating IAP gene expression, suggesting that GW843682X may become a novel therapeutic agent for nasopharyngeal carcinoma.

Background: Chronic myeloid leukemia (CML), also recognized as chronic myelogenous leukemia, is initiated in some types of blood-forming cells of the bone marrow. The therapeutic approach to CML is usually chemotherapy; however, severe side effects and complications are major problems in the clinical research. Thus, recent efforts have focused on the search for compounds affecting apoptosis in this type of cancer. Objective: In this study, in vitro anticancer activity of two compounds (A and B) consisting of a hydrazide backbone with nitro-thiophen and furan substituents was assessed against K562 cell line displaying certain levels of sensitivity to pro-apoptotic compounds. Methods: The anticancer activity was assessed using MTT assay, flowcytometry, annexin-V and Western blot analysis. Results: Compounds A and B were both active and revealed a remarkable in vitro cytotoxic effect showing IC50 values of 0.09 and 0.07 μM, respectively, after 72 h of treatment. A significant increase in annexin-V/PI staining, sub-G1 population and Bax/Bcl-2 ratio revealed the apoptotic cell death of compounds A- and B-treated K562 cells. Conclusion: The results presented here could be used as a first step for the development of powerful chemotherapeutic agents to treat leukemia.

4-Anilinoquinazoline derivatives possess high anti-cancer activities. Many of them are highly selective tyrosine kinase inhibitors (TKI), particularly against epidermal growth factor receptor (EGFR). EGFRs are overexpressed or mutated in most carcinomas and are required for tumor progression. The efficacy of EGFR-targeted anti-tumor drugs is impaired by drug-induced acquired resistance. Therefore, there is urgency to find better anti-cancer agents with novel effects on EGFR. 4-Anilinoquinazolines are small molecule EGFR inhibitors that have been synthesized and assessed for their anti-tumor bioactivity. In this paper, we review the 4-anilinoquinazoline derivatives with EGFR inhibitor activity reported in recent years.

The binding mode analysis of Gefitinib revealed that 6-propylmorpholino group (sidechain) shows no interactions due to its weak electron density. In order to modify the electron density of Gefitinib’s sidechain, novel pyrrolidino analogs of Gefitinib where morpholino groups were replaced by substituted pyrrolidino groups were synthesized. Gefitinib derivatives with high electronegativity atoms or groups in the pyrrolidino moiety always exhibit high potent activity against EGFR and human cancer cell lines, A431, MDA-MB-231 and A549. Among these derivatives, 16 displayed the best pharmacokinetic properties that make it to be a promising candidate for developing drugs to replace Gefitinib.