Anti-Cancer Agents in Medicinal Chemistry (Formerly Current Medicinal Chemistry - Anti-Cancer Agents) - Volume 16, Issue 3, 2016

Heat shock protein 90 (Hsp90) is an important member of the chaperone protein family and it is involved in stabilization, regulation, and maintenance of oncogenic client proteins with co-chaperones. Cochaperones regulate the ATPase activity of Hsp90 and its interactions with oncogenic client proteins. Therefore, Hsp90 and its co-chaperones have become significant therapeutic targets for cancer treatment. Many chemical compounds have been evaluated for Hsp90 inhibition as well as significant results were obtained in clinical trials. In this paper, we emphasize on the key roles of Hsp90 and its co-chaperones in tumorigenesis and overview therapeutic strategies of Hsp90 inhibition in oncology.

The continuous activation of the mitogen-activated protein kinase signaling cascade, typified by the BRAFV600E mutation, is one of the key alterations in melanoma. Accordingly, two BRAF inhibitors (BRAFi), vemurafenib and dabrafenib are utilized to treat melanoma and resulted in an excellent clinical outcome. However, the clinical success is not long-lasting, and the BRAFi resistance and disease progression inevitably occurs in nearly all patients. Endoplasmic reticulum stress-induced unfolded protein response and autophagy have emerged as potential pro-survival mechanisms adopted by melanoma cells in response to BRAFi. In this review, we discuss the role of unfolded protein response and autophagy that are implicated in the development of BRAFi-resistant melanoma and the corresponding strategy aiming at overcoming the intractable clinical problem.

Core-shell structured aggregates of amphiphilic block copolymer are hopefully drug delivery system because of their ability to encapsulate hydrophobic drugs, and their hydrophilic shell can prolong retention time of drugs in the blood circulation system. Cyclodextrin is a kind of hydrophilic polysaccharide containing multiple hydroxyl groups, providing an inner hole that can load small molecule through host-guest interaction. These hydroxyl groups or their derived functional ones are utilized in conjugation with polymeric chains to form block copolymers. These copolymers can not only encapsulate hydrophobic drugs, but also encapsulate hydrophilic drugs (like DNA, protein, etc) through hydrophobic, host-guest or electrostatic interactions, which strengthen interaction between drugs and materials compared with general copolymers, indicating that formed drug delivery systems are more stable. By introduction of target molecule, they also achieve selective delivery of drugs to specific tissues or organs. So, several researchers are stimulated to carry out many studies for the development of cyclodextrin copolymeric drug delivery systems in recent. In this review, we focus the cyclodextrin copolymers’ application in the anticancer agents’ delivery.

The hedgehog (Hh) signaling pathway, which is almost completely silenced in normal adult tissues but highly activated in cancer, offers ideal drug targets for small molecule development. During the last few years, several studies have indicated that the Hh pathway plays a role in tumor development and maintenance, and novel drugs inhibiting Hh signaling have been discovered. Although results from clinical trials in patients harboring activating mutations of Hh have been promising, there are many controversies regarding the role of the pathway in tumors that demonstrate ligand over-expression without identified mutations. In this review, we focus on the function and expression of the Hh pathway in different tumors and discuss the targeting approaches tested in preclinical and clinical studies.

Although surgical resection is the standard curative therapy for gastric cancer, these tumors are often diagnosed at an advanced stage, when surgery is not recommended. Alternative treatments such as radiotherapy and chemotherapy achieve only very modest results. There is therefore an urgent need to advance in this field of oncologic gastroenterology. The poor response of gastric cancer to chemotherapy is usually due to a combination of mechanisms of chemoresistance (MOC), which may include a reduction in drug uptake (MOC-1a), enhanced drug efflux (MOC-1b), a reduced proportion of active agents in tumor cells due to a reduction in pro-drug activation or an enhancement in drug inactivation (MOC-2), changes in the expression/function of the molecular targets of anticancer drugs (MOC-3), an enhanced ability of cancer cells to repair anticancer drug-induced DNA damage (MOC-4), and decreased expression/function of pro-apoptotic factors or up-regulation of anti-apoptotic genes (MOC-5). Two major goals of modern pharmacology aimed at overcoming this situation are the prediction of a lack of response to chemotherapy and the identification of the underlying mechanisms accounting for primary or acquired refractoriness to anticancer drugs. These are important issues if we are to select the best pharmacological regime for each patient and develop novel strategies to overcome chemoresistance. The present review reports updated information regarding the mechanisms of chemoresistance (from MOC-1 to MOC-5) in gastric cancer, the advances made in the prediction of the failure of chemotherapeutic treatment, and novel strategies based on gene therapy currently being developed to treat these tumors.

The phosphorus-containing glycerolipid based antitumor drugs (edelfosine as a prototype) are currently in clinical trials. To avoid the use of potentially harmful phosphoric reagents in the preparation of biologically active glycerolipids, and to obtain the compounds without the phosphoester bond cleavable inside the cells, we developed the synthesis of non-phosphorous glycerolipids (NPGLs) with neutral or cationic polar ‘heads’. In this study, we analyzed the ability of novel NPGLs L1-L5 to interact with duplex DNA and interfere with the DNA modifying enzyme topoisomerase I (topo I). In cell-free systems, NPGLs formed highly affine complexes with DNA. Molecular docking revealed that NPGLs fitted very well into the DNA minor groove. Compounds L2 (with two long hydrophobic ‘tails’) and L4 (with ethylimidazolium cationic group), the most affine DNA binders, showed the best calculated energies of complex formation with DNA and topo I. The models demonstrated the binding of NPGLs to the topo I site known for interaction with conventional inhibitors. Each NPGL attenuated the topo I mediated unwinding of supercoiled DNA. Again, L2 and, to a lesser extent, L4 were the most potent topo I inhibitors. Thus, NPGLs with polar ‘heads’ emerge as a new class of DNA ligands and interfacial topo I antagonists.

Angiogenesis is the process of new blood vessel formation, regulated by a number of pro- and antiangiogenic factors and usually begins in response to hypoxia. Exogenous administration of melatonin has shown numerous anti-tumor effects and appears to inhibit tumor angiogenesis. However, many factors involved in the anti-angiogenic effect of melatonin are still under investigation. Here, we evaluate the effects of melatonin on cell viability and expression of angiogenic factors in MCF-7 and MDA-MB-231 breast cancer cells under hypoxic conditions. Cell viability was investigated by MTT and gene and protein expression of the hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF-A) were verified by qPCR and immunocytochemistry after melatonin treatment (1 mM) under hypoxic conditions. Additionally, a protein array with 20 different cytokines/factors was performed on tumor cell lysates. The results showed that 1 mM of melatonin reduced the viability of MCF-7 and MDA-MB-231 cells (p < .05). This treatment also decreased both gene and protein expression of HIF-1α and VEGF-A under hypoxic conditions (p < .05). Among the proteins evaluated by protein array, melatonin treatment during hypoxia reduced VEGF-C, VEGFR receptors (VEGFR2 and VEGFR3), matrix metalloproteinase 9 (MMP9) and Angiogenin in MCF-7 cells. In MDA-MB-231 cells, a significant decrease was observed in VEGFR2, epidermal growth factor receptor (EGFR) and Angiogenin (p < .05). Taken together, these results showed that melatonin acts in the regulation of angiogenic factors in breast tumor cells and suggests an anti-angiogenic activity, particularly under hypoxic conditions.

In vitro antitumor activity of various organogallium(III) complexes (1–8) has been tested against CT26CL25, HCT116, SW480 colon cancer cell lines. CV and MTT assays were used to assess on the antiproliferative effect of investigated organogallium(III) complexes. From the investigated complexes, the most active was found to be tetranuclear compound 8 against CT26CL25 cells. Flow cytometric analysis of the CT26CL25 cells upon the treatment with 8 was performed in order to determine the role of apoptosis, caspase activation, autophagy and proliferation rate on the cell death caused with this compound. Results indicate cytotoxic potential of the tetranuclear complex 8 by inducing caspase independent apoptosis and blocking most of the cells before first division.

In an attempt to improve the localized paclitaxel delivery, carrier based thermoresponsive chitosan hydrogel was exploited in the present study. Nanoliposomes as carrier for paclitaxel were prepared and optimized in strength of 6 mg/ml similar to marketed paclitaxel formulation. The chitosan solution (2% w/v) mixed with different concentrations of dibasic sodium phosphate (DSP) was evaluated as thermoresponsive systems in terms of gelling temperature and time. Finally, the drug loaded nanoliposomes were incorporated in optimized chitosan- DSP hydrogel base to form nanoliposomal in situ thermosensitive hydrogel formulations having dual mechanism of protection and release. The optimal formulation containing DSP was selected on the basis of minimal gelation temperature (37±0.8 ºC) and time (6.7±0.3 min). In vitro drug release experiment illustrated that developed formulation manifested sustained release action in which drug release was extended for more than 72 h compared to marketed formulation. In addition, optimized nanoliposomal hydrogel demonstrated enhanced biological half-life of 15.7±1.5h, depicting maintenance of constant plasma concentration in contrast to marketed formulation that showed the half-life (t1/2) of 3.6±0.4h. The in vivo anti tumor activity tested using EAC model also corroborated the above findings that developed formulation was having significant higher anti-tumor activity and reduced toxicity than the marketed formulation. Tumor volume was found to reduce upto 89.1±3.5% by treatment with in situ hydrogel formulation. The histopathological study of tumor also demonstrated the better safety and efficacy of developed formulation in comparison to marketed paclitaxel formulation. Our results suggest that carrier based chitosan hydrogel could be an efficacious vehicle for sustained and localized delivery of paclitaxel.

Twenty-four new dibenzo[b,d]furan–1H-1,2,4-triazole derivatives were synthesized and investigated for in vitro cytotoxic activity against five tumor cell lines. The results show that the substitution at 4-position of the 1,2,4-triazole with a benzyl, 4-bromophenacyl or naphthylacyl group could be crucial for prommoting cytotoxic activity. Especially, compound 28 was found to be the most powerful derivative with IC50 values lower than 3.50 μM against five investigated tumor cell lines, while compound 19 showed selective activity against leukemia (HL-60) and breast carcinoma (MCF-7) cell lines with IC50 values of 0.80 and 1.76 μM, respectively. Compound 19 can induce cell cycle arrest at G2/M phase and apoptosis in SMMC-7721 cells.

Background and Aim: The incidence of acute lymphoblastic leukemia (ALL) is highest in childhood malignant tumor in China. The high-dose methotrexate (HDMTX) treatment is very effective in ALL, and it can improve event-free survival rate. However, while executing the anti-tumor effect, it produces highly toxic effects on rapidly dividing cells which are normal. It seems probable that the HDMTX treatment injures intestinal mucosal barrier. The changes of intestinal mucosal barrier can be evaluated through measuring the level of plasma endotoxin and diamine oxidase (DAO). Method: Blood samples were collected from 30 normal children and 30 children with ALL at 1h, 24h, 44h and 68h after HDMTX. The levels of plasma endotoxin and DAO were measured at 1h, 24h, 44h and 68h after HDMTX with spectrophotometry. The levels of endotoxin and DAO were also measured in 4 different courses in 7 children with ALL. Results: The levels of plasma endotoxin and DAO at 1h, 24h, 44h and 68h after HDMTX were higher than in normal children (P<0.01). The levels of plasma endotoxin and DAO at 24h and 44h after HDMTX were both higher than at 1h and 68h (P<0.01). There was no significant difference found in the measured results of plasma endotoxin and DAO at 1h and 68h after HDMTX (P>0.05). There was no significant difference found in the increased levels of endotoxin and DAO at 1h, 24h, 44h and 68h after HDMTX in 4 different courses of 7 children with ALL(P>0.05). Conclusion: By measuring the level of plasma endotoxin and DAO in children with ALL and during HDMTX chemotherapy, the results suggest that there is increased intestinal permeability.

Purpose: Cisplatin as a platinum (Pt)-based chemotherapeutic compound is commonly applied for the treatment of several types of cancer. Nonetheless, drug resistance and severe adverse effects have been observed upon using cisplatin. Here, we have explored the cytotoxicity of novel Pt-based compounds on several cancer cell lines. Methods: Five synthetic Pt compounds as well as cisplatin were investigated by XTT assay to determine their cytotoxicity against cell lines originated from prostate, ovary, and breast cancers at different time periods at various concentrations. Additionally, the apoptosis rate in cell lines was determined using flow cytometry. Binding to DNA was investigated through spectrophotometric and viscometric studies. Results: With the exception of one compound, all of the Pt-complexes effectively killed the prostate cancer cell lines (i.e. PC-3 and DU 145). One compound, [Pt(2,2'- dipyridylamine)Cl4].DMF, was chosen as the most potent compound due to its high selective cytotoxic activity and its cytotoxicity was further tested and compared with that of cisplatin on SKOV-3, Caov-4, MDA-MB-231, and MCF7 cell lines. [Pt(2,2'-dipyridylamine)Cl4].DMF had a higher selective cytotoxic capacity in comparison with cisplatin at higher concentrations and longer culture periods. Furthermore, as related to apoptosis induction, treatment with [Pt(2,2'-dipyridylamine)Cl4 ].DMF was significantly more effective than that of cisplatin in five out of six examined cell lines. [Pt(2,2'-dipyridylamine)Cl4].DMF was shown to intercalate into DNA. Conclusions: The current study introduced a novel Pt-based complex with highly selective and potent in vitro anti-tumor impacts superior to those of cisplatin, a conventional chemotherapeutic agent. [Pt (2,2'-dipyridylamine)Cl4].DMF could be regarded as a promising antitumor agent in future investigations.