Synthesis and characterization of a novel iNOS/Akt inhibitor Se,Se'-1,4-phenylenebis(1,2-ethanediyl)bisisoselenourea (PBISe)--against colon cancer

Incorporating Selenium into Heterocycles and Natural Products─From Chemical Properties to Pharmacological Activities

Selenium (Se)-containing compounds have emerged as potential therapeutic agents for the treatment of a range of diseases. Through tremendous effort, considerable knowledge has been acquired to understand the complex chemical properties and biological activities of selenium, especially after its incorporation into bioactive molecules. From this perspective, we compiled extensive literature evidence to summarize and critically discuss the relationship between the pharmacological activities and chemical properties of selenium compounds and the strategic incorporation of selenium into organic molecules, especially bioactive heterocycles and natural products. We also provide perspectives regarding the challenges in selenium-based medicinal chemistry and future research directions.

The crystal structure of 2-(4-((carbamimidoylthio)methyl)benzyl)isothiouronium hexafluorophosphate monohydrate, C10H17F6N4OPS2

C10H17F6N4OPS2, monoclinic, P21/c (no. 14), a = 13.0455(12) Å, b = 12.6114(12) Å, c = 10.7642(10) Å, β = 99.546(8)°, V = 1746.4(3) Å3, Z = 4, R gt(F) = 0.0425, wR ref(F 2) = 0.1173, T = 150 K.

A Selenium Containing Inhibitor for the Treatment of Hepatocellular Cancer

Hepatocellular carcinoma (HCC) is the third most deadly cancer in the world. New treatment strategies are desperately needed due to limited standard therapies. Activation of the Erk, Akt, and STAT3pathways is implicated in the prognosis of HCC. The Se,Se'-1,4-phenylenebis(1,2-ethanediyl) bisisoselenourea (PBISe), is a selenium-containing MAPK and PI3 kinase inhibitor, effectively inhibit tumorigenesis in a variety of experimental models. The aim of our study is to demonstrate the potential role of PBISe in the treatment of HCC. The anti-proliferative and pro-apoptotic ability of PBISe is studied in vitro in four human HCC cell lines and in vivo in a spontaneous murine HCC model. Inhibition of cancer growth was performed by cell viability assay and apoptosis by caspase 3/7, PARP cleavage, annexin-V, and TUNEL assays. Role of PBISe on PI3 kinase, MAPK and STAT3 signaling is determined by Western blotting. In vivo effects of PBISe on tumor sizes were monitored using MRI in a spontaneous murine HCC. Liver tissues from the PBISe-treated mice are analyzed for angiogenesis, proliferation, and signaling pathway markers. Overall, PBISe activated caspase-3/7 and increased DNA fragmentation, which is positively correlated with the increased PARP cleavage. PBISe promoted apoptosis by inhibiting PI3K, MAPK, and STAT3 signaling with significant reduction in the tumor sizes (p < 0.007). PBISe-treated tumors reduced survival marker PCNA, and angiogenesis markers Vegf-A, Vegf-R3 and CD34. These results demonstrate the chemotherapeutic effects of PBISe, by inhibiting tumor growth and facilitating tumor apoptosis for HCC treatment.

Novel seleno- and thio-urea derivatives with potent in vitro activities against several cancer cell lines

A series of novel selenourea derivatives and corresponding thiourea analogs were synthesized and tested against a panel of six human cancer cell lines: melanoma (1205Lu), lung carcinoma (A549), prostatic carcinoma (DU145), colorectal carcinoma (HCT116), pancreatic epithelioid carcinoma (PANC-1) and pancreatic adenocarcinoma (BxPC3). In general, we found that the selenium-containing derivatives were more potent than their isosteric sulfur analogs. Four selenourea derivatives (1e, 1f, 1g and 1i) showed IC50 values below 10 μM in all of tested cell lines at 72 h. On the basis of its potent activity, compound 1g was selected for further biological evaluation in different colon cancer cell lines. Our results indicated that compound 1g induced apoptosis by caspase activation, along with inhibition of anti-apoptotic proteins.

Ferrocene incorporated selenoureas as anticancer agents

For a compound to be a best chemopreventive agent it should be a descent DNA binder and at the same time should be active against any of the three stages of carcinogenesis i.e. cancer initiation, cancer propagation and tumor growth. Most of the problems associated with chemotherapy can be overcome if the chemopreventive agent is active against all the three stages of cancer development. Cancer may be initiated by higher concentration of free radicals, inflammating agents and phase I enzymes (Cytochrome P450) in the body. Cancer propagation can be very efficiently controlled by inducing the phase II enzymes (glutathione S-transferases (GSTs), UDP-glucuronosyl transferases, and quinone reductases) in the body and cancer termination depends on the killing of the faulty cells i.e. cytotoxic actions. This article reports comprehensively the comparative DNA binding studies (with, cyclic voltammetry, UV-vis spectroscopy and viscometry), antioxidant activities (DPPH scavenging), anti-inflammatory activities (nitrite inhibition), phase I enzyme inhibition activities (aromatase inhibition), phase II enzyme induction studies (quinone reductase induction) and cytotoxic studies against neuroblastoma (MYCN2 and SK-N-SH), liver cancer (Hepa 1c1c7) and breast cancer (MCF-7) of seventeen ferrocene incorporated selenoureas.

Selenium substitution endows cystine with radiosensitization activity against cervical cancer cells

Selenium substitution could endow cystine the radiosensitization activity against cervical cancer HeLa cells through overproduction of ROS and activation of downstream signaling, which suggests this could be a novel strategy for design of cancer radiosensitizers.

Microwave-assisted synthesis of new selenazole derivatives with antiproliferative activity

New aryl-hydrazinyl-1,3-selenazole and aroyl-hydrazonyl-1,3-selenazoles were synthesized via Hantzsch type condensation reactions of selenosemicarbazides with α-halogenocarbonyl derivatives, under classical versus microwave heating conditions. Excellent yields and shorter reaction times were obtained under irradiation conditions. The structures of the synthesized compounds were assigned based on spectroscopic data (FT-IR, 1H-NMR), MS and elemental analysis. Selenazole derivatives were screened for their anti-proliferative effects against two leukemia cell lines (CCRF-CEM and HL60) and three carcinoma cell lines (MDA-MB231, HCT116 and U87MG).

NOS-2 signaling and cancer therapy

The role of NO and cGMP signaling in tumor biology has been extensively studied during the past three decades. However, whether the pathway is beneficial or detrimental in cancer is still open to question. We suggest several reasons for this ambiguity: first, although NO participates in normal signaling (e.g., vasodilation and neurotransmission), NO is also a cytotoxic or apoptotic molecule when produced at high concentrations by inducible nitric-oxide synthase (iNOS or NOS-2). In addition, the cGMP-dependent (NO/sGC/cGMP pathway) and cGMP-independent (NO oxidative pathway) components may vary among different tissues and cell types. Furthermore, solid tumors contain two compartments: the parenchyma (neoplastic cells) and the stroma (nonmalignant supporting tissues including connective tissue, blood vessels, and inflammatory cells) with different NO biology. Thus, the NO/sGC/cGMP signaling molecules in tumors as well as the surrounding tissue must be further characterized before targeting this signaling pathway for tumor therapy. In this review, we focus on the NOS-2 expression in tumor and surrounding cells and summarized research outcome in terms of cancer therapy. We propose that a normal function of the sGC-cGMP signaling axis may be important for the prevention and/or treatment of malignant tumors. Inhibiting NOS-2 overexpression and the tumor inflammatory microenvironment, combined with normalization of the sGC/cGMP signaling may be a favorable alternative to chemotherapy and radiotherapy for malignant tumors.

Chemoprevention of melanoma

Despite advances in drug discovery programs and molecular approaches for identifying drug targets, incidence and mortality rates due to melanoma continue to rise at an alarming rate. Existing preventive strategies generally involve mole screening followed by surgical removal of the benign nevi and abnormal moles. However, due to lack of effective programs for screening and disease recurrence after surgical resection, there is a need for better chemopreventive agents. Although sunscreens have been used extensively for protecting from UV-induced melanomas, results of correlative population-based studies are controversial, with certain studies suggest increased skin cancer risk in sunscreen users. Therefore, these studies require further authentication to conclusively confirm the chemoprotective efficacy of sunscreens. This chapter reviews the current understanding regarding melanoma chemoprevention and the various strategies used to accomplish this objective.

The Akt signaling pathway: an emerging therapeutic target in malignant melanoma

Studies using cultured melanoma cells and patient tumor biopsies have demonstrated deregulated PI3 kinase-Akt3 pathway activity in ~70% of melanomas. Furthermore, targeting Akt3 and downstream PRAS40 has been shown to inhibit melanoma tumor development in mice. Although these preclinical studies and several other reports using small interfering RNAs and pharmacological agents targeting key members of this pathway have been shown to retard melanoma development, analysis of early Phase I and Phase II clinical trials using pharmacological agents to target this pathway demonstrate the need for (1) selection of patients whose tumors have PI3 kinase-Akt pathway deregulation, (2) further optimization of therapeutic agents for increased potency and reduced toxicity, (3) the identification of additional targets in the same pathway or in other signaling cascades that synergistically inhibit the growth and progression of melanoma, and (4) better methods for targeted delivery of pharmaceutical agents inhibiting this pathway. In this review we discuss key potential targets in PI3K-Akt3 signaling, the status of pharmacological agents targeting these proteins, drugs under clinical development, and strategies to improve the efficacy of therapeutic agents targeting this pathway.

Melanoma prevention using topical PBISe

Malignant melanoma is the deadliest form of skin cancer, known for its drug resistance and high metastatic potential. Deregulated PI3 and mitogen activated protein (MAP) kinase pathways promote early melanocytic lesion development and confer drug resistance. No agent exists to target these deregulated pathways to prevent cutaneous noninvasive melanocytic cells or invasive melanomas from developing into more aggressive widely disseminated metastatic disease. In this study, a selenium containing isosteric analogue of PBIT [S, S'-1,4-phenylenebis(1,2-ethanediyl)bis-isothiourea] called PBISe [Se, Se'-1,4-phenylenebis(1,2-ethanediyl)bis-isoselenourea] is shown to moderate these 2 major signaling pathways to prevent cutaneous melanocytic lesion or melanoma development. Topical application of PBISe retarded melanocytic lesion development in laboratory-generated skin by 70% to 80% and in animal skin by approximately 50%. Mechanistically, prevention of lesion development occurred due to decreased Akt3 signaling, which increased MAP kinase pathway activity to inhibitory levels. The combined effect of targeting these pathways led to decreased cell proliferation and increased apoptotic cell death thereby preventing melanoma development. Thus, topically applied PBISe treatment has potential to prevent noninvasive melanocytic lesion and invasive metastatic melanoma development in skin.

Inducible nitric oxide synthase expression correlates with angiogenesis, lymphangiogenesis, and poor prognosis in gastric cancer patients

Increased nitric oxide synthase expression plays a key role in tumor progression. To examine inducible nitric oxide synthase expression and its correlation with clinical variables, such as tumor progression, angiogenesis, lymphangiogenesis, and prognosis in gastric cancer, we studied inducible nitric oxide synthase expression in gastric cancer samples from 211 patients with 5-year follow-up. CD105 and D2-40 were adopted as biomarkers for tumor angiogenesis and lymphangiogenesis, respectively. Inducible nitric oxide synthase staining was mainly found in the cytoplasm of gastric cancer tumor cells. Positive inducible nitric oxide synthase immunoreactivity was seen in 54.03% of gastric cancer specimens, which was correlated with lymph node metastasis, vascular invasion, distant metastasis, and TNM stage. Compared with inducible nitric oxide synthase negative patients, inducible nitric oxide synthase-positive patients had significantly shorter survival times and higher microvessel density and lymphatic vessel density. Intratumor and peritumor blood microvessel density and lymphatic vessel density correlated with inducible nitric oxide synthase expression (Spearman ρ test, P < .05). We conclude that inducible nitric oxide synthase expression correlates with lymph node metastasis, vascular invasion, distant metastasis, TNM stage, and poor survival rate in gastric cancer. We propose that synthesized inducible nitric oxide synthase increases angiogenesis, and lymphangiogenesis thus promotes tumor progression. Inducible nitric oxide synthase expression may be a good biomarker for poor prognosis in gastric cancer.

Synthesis and evaluation of the anti-inflammatory properties of selenium-derivatives of celecoxib

Celecoxib is a selective cyclooxygenase (COX)-2 inhibitor used to treat inflammation, while selenium is known to down-regulate the transcription of COX-2 and other pro-inflammatory genes. To expand the anti-inflammatory property, wherein celecoxib could inhibit pro-inflammatory gene expression at extremely low doses, we incorporated selenium (Se) into two Se-derivatives of celecoxib, namely; selenocoxib-2 and selenocoxib-3. In vitro kinetic assays of the inhibition of purified human COX-2 activity by these compounds indicated that celecoxib and selenocoxib-3 had identical K(I) values of 2.3 and 2.4μM; while selenocoxib-2 had a lower K(I) of 0.72μM. Furthermore, selenocoxib-2 inhibited lipopolysaccharide-induced activation of NF-κB leading to the down-regulation of expression of COX-2, iNOS, and TNFα more effectively than selenocoxib-3 and celecoxib in RAW264.7 macrophages and murine bone marrow-derived macrophages. Studies with rat liver microsomes followed by UPLC-MS-MS analysis indicated the formation of selenenylsulfide conjugates of selenocoxib-2 with N-acetylcysteine. Selenocoxib-2 was found to release minor amounts of Se that was effectively inhibited by the CYP inhibitor, sulphaphenazole. While these studies suggest that selenocoxib-2, but not celecoxib and selenocoxib-3, targets upstream events in the NF-κB signaling axis, the ability to effectively suppress NF-κB activation independent of cellular selenoprotein synthesis opens possibilities for a new generation of COX-2 inhibitors with significant and broader anti-inflammatory potential.

Synthesis and antiproliferative activity of novel symmetrical alkylthio- and alkylseleno-imidocarbamates

The study described here concerns the synthesis of a series of thirty new symmetrically substituted imidothiocarbamate and imidoselenocarbamate derivatives and their evaluation for antitumoral activity in vitro against a panel of five human tumor cell lines: breast adenocarcinoma (MCF-7), colon carcinoma (HT-29), lymphocytic leukemia (K-562), hepatocarcinoma (Hep-G2), prostate cancer (PC-3) and one non-malignant mammary gland-derived cell line (MCF-10A). The GI(50) values for eighteen of the compounds were below 10 μM in at least one cell line. Two cancer cells (MCF-7 and HT-29) proved to be the most sensitive to five compounds (1b, 2b, 3b, 4b and 5b), with growth inhibition in the nanomolar range, and compounds 1b, 3b, 7b, 8b and 9b gave values of less than 1 μM. In addition, all of the aforementioned compounds exhibited lower GI(50) values than some of the standard chemotherapeutic drugs used as references. The results also reveal that the nature of the aliphatic chain (methyl is better than benzyl) at the selenium position and the nature of the heteroatom (Se better than S) have a marked influence on the antiproliferative activity of the compounds. These findings reinforce our earlier hypothesis concerning the determinant role of the selenomethyl group as a scaffold for the biological activity of this type of compound. Considering both the cytotoxic parameters and the selectivity index (which was compared in MCF-7 and MCF-10A cells), compounds 2b and 8b (with a selenomethyl moiety) displayed the best profiles, with GI(50) values ranging from 0.34 nM to 6.07 μM in the five cell lines tested. Therefore, compounds 2b and 8b were evaluated by flow cytometric analysis for their effects on cell cycle distribution and apoptosis in MCF-7 cells. 2b was the most active, with an apoptogenic effect similar to camptothecin, which was used as a positive control. Both of them provoked cell cycle arrest leading to the accumulation of cells in either G(2)/M and S phase. These two compounds can therefore be considered as the most promising candidates for the development of novel generations of antitumor agents.

Electrophilic aromatic selenylation: new OPRT inhibitors

2-Ethoxyethaneseleninic acid reacts with electron-rich aromatic substrates to deliver, by way of the selenoxides, the (2-ethoxyethyl)seleno ethers, which can in turn be transformed into a diverse set of aryl-selenylated products. Among these, a family of 5-uridinyl derivatives shows submicromolar inhibition of human and malarial orotate phosphoribosyltransferase.

OGA inhibition by GlcNAc-selenazoline

The title compound, which differs from the powerful O-GlcNAcase (OGA) inhibitor GlcNAc-thiazoline only at the chalcogen atom (Se for S), is a much weaker inhibitor in a direct OGA assay. In human cells, however, the selenazoline shows comparable ability to induce hyper-O-GlcNAc-ylation, and the two show similar reduction of insulin-stimulated translocation of glucose transporter 4 in differentiated 3T3 adipocytes.