Furoxans and tocopherol analogs–furoxan hybrids as anticancer agents

Contributions of viral oncogenes of HPV-18 and hypoxia to oxidative stress and genetic damage in human keratinocytes

Infection with high-risk human papillomaviruses like HPV-16 and HPV-18 is highly associated with the development of cervical and other cancers. Malignant transformation requires viral oncoproteins E5, E6 and E7, which promote cell proliferation and increase DNA damage. Oxidative stress and hypoxia are also key factors in cervical malignant transformation. Increased levels of reactive species of oxygen (ROS) and nitrogen (RNS) are found in the hypoxic tumor microenvironment, promoting genetic instability and invasiveness. In this work, we studied the combined effect of E5, E6 and E7 and hypoxia in increasing oxidative stress and promoting DNA damage and nuclear architecture alterations. HaCaT cells containing HPV-18 viral oncogenes (HaCaT E5/E6/E7-18) showed higher ROS levels in normoxia and higher levels of RNS in hypoxia compared to HaCaT parental cells, as well as higher genetic damage in hypoxia as measured by γH2AX and comet assays. In hypoxia, HaCaT E5/E6/E7-18 increased its nuclear dry mass and both cell types displayed marked heterogeneity in nuclear dry mass distribution and increased nuclear foci. Our results show contributions of both viral oncogenes and hypoxia to oxidative stress, DNA damage and altered nuclear architecture, exemplifying how an altered microenvironment combines with oncogenic transformation to promote tumor progression.

Recent progress in synthesis and application of furoxan

This review highlights recent developments in the synthesis and application of furoxan. The chemistry of furoxan is relatively underdeveloped compared to that of other heterocycles owing to its difficult synthesis, which is ascribed to the labile nature of this molecule under various reaction conditions. Nevertheless, recent studies have conducted a variety of bond-forming reactions on the furoxan ring via a post-ring introduction of substituents (PRIS) strategy. This strategy enables the synthesis of furoxan molecules of interest more directly than the conventional methods that rely on the pre-installation of substituents on the furoxan ring precursors. In this review, the PRIS strategy for furoxan synthesis is classified and discussed according to the type of bond formed. Additionally, recent progress in the application of furoxan molecules, predominantly facilitated by the development of new synthetic methods, is covered in this review.

New Nitric Oxide-Releasing Compounds as Promising Anti-Bladder Cancer Drugs

Bladder cancer is a worldwide problem and improved therapies are urgently needed. In the search for newer strong antitumor compounds, herein, we present the study of three nitric oxide-releasing compounds and evaluate them as possible therapies for this malignancy. Bladder cancer cell lines T24 and 253J were used to evaluate the antiproliferative, antimigratory, and genotoxic effects of compounds. Moreover, we determined the NF-κB pathway inhibition, and finally, the survivin downregulation exerted by our molecules. The results revealed that compounds 1 and 3 exerted a high antiproliferative activity against bladder cancer cells through DNA damage and survivin downregulation. In addition, compound 3 reduced bladder cancer cell migration. We found that nitric oxide donors are promising molecules for the development of a new therapeutic targeting the underlying mechanisms of tumorigenesis and progression of bladder cancer.

Photo-repair effect of a bacterial Antarctic CPD-photolyase on UVC-induced DNA lesions in human keratinocytes

Exposure to ultraviolet radiation from sunlight induces oxidative DNA lesions and bipyrimidine photoproducts that can lead to photo-aging and skin carcinogenesis. CPD-photolyases are flavoproteins that repair cyclobutane pyrimidine dimers using blue light as an energy source. In the present work, we evaluated the photo-repair effect of the recombinant CPD-photolyase PhrAHym from the Antarctic bacterium Hymenobacter sp. UV11 on DNA lesions in human keratinocytes induced by UVC light. By performing immunochemistry assays we observed that PhrAHym repairs in a highly efficient way the CPD-photoproducts and reduces the γH2AX formation. Since this enzyme is non-cytotoxic and repairs UVC-induced DNA lesions in human keratinocytes, we propose that PhrAHym could be used as a biotherapeutic agent against UV-induced skin cancer, photoaging, and related diseases.

Synthesis of harmine-nitric oxide donor derivatives as potential antitumor agents

To further improve the anti-tumor activity of Harmine (HM), we took the hybridization approach and synthesized harmine derivatives-furoxan hybrids containing nitric oxide (NO) releasing parts by connecting NO donors with anti-tumor active fragments to harmine. Then, the synthesized compounds were evaluated for their in vitro cytotoxicity against five human cancer cell lines. Among them, compound 10 was found to have the strongest antiproliferative activity against HepG2 (IC₅₀ = 1.79 µM). In addition, compound 10 produced high levels of NO in vitro, verifying that the release of NO was closely correlated to the antiproliferative activity. In addition, Compound 10 also showed good plasma stability. Finally, we also preliminarily investigated the acute toxicity of compound 10 in mice and assessed the absorption of compound 10 by Caco-2 cell permeability assay. In brief, the remarkable biological characteristics of the new harmine derivatives-furoxan hybrids may make them promising candidates for human cancer intervention.

Greener Synthesis of Antiproliferative Furoxans via Multicomponent Reactions

Prostate and bladder cancers are commonly diagnosed malignancies in men. Several nitric oxide donor compounds with strong antitumor activity have been reported. Thus, continuing with our efforts to explore the chemical space around bioactive furoxan moiety, multicomponent reactions were employed for the rapid generation of molecular diversity and complexity. We herein report the use of Ugi and Groebke-Blackburn-Bienaymé multicomponent reactions under efficient, safe, and environmentally friendly conditions to synthesize a small collection of nitric-oxide-releasing molecules. The in vitro antiproliferative activity of the synthesized compounds was measured against two different human cancer cell lines, LNCaP (prostate) and T24 (bladder). Almost all compounds displayed antiproliferative activity against both cancer cell lines, providing lead compounds with nanomolar GI₅₀ values against the cancer bladder cell line with selectivity indices higher than 10.

Assessment of the cytoprotective effect of the homeopathic compound Canova® on African green monkey kidney (VERO) cell line exposed to the drug dipyrone sodium

Dipyrone or metamizole is one of the most frequently used analgesic worldwide. Despite its widespread use, this drug may exert genotoxic and cytotoxic effects on lymphocytes. Therefore, studies with therapeutic agents that may provide protection against these effects are important. The homeopathic compound Canova® (CA) appears to be a beneficial candidate for preventing DNA damage and cellular lethality, since this compound acts as an immunomodulator associated with cytoprotective actions. Hence, the aim of the present investigation was to determine the potential cytoprotective effects of CA using cell line VERO as a model. VERO cells were incubated with sodium dipyrone and subsequently subject to the comet, apoptosis and immunocytochemistry assays. Data demonstrated that sodium dipyrone induced an increase in DNA damage index (DI) employing the comet assay. However, when VERO cells were co-treated with CA at the three concentrations studied, a significant reduction in DI was observed, indicating an antigenotoxic effect attributed to CA. Further dipyrone induced an elevation in %apoptosis at 24 and 48 hr. However, when dipyrone was co-incubated with CA, a significant reduction in %apoptosis was noted at the three concentrations of CA employed. Results from immunocytochemical analysis showed a rise in the expression of caspase 8 and cytochrome C when cells were exposed to dipyrone. In contrast, co-treatment of dipyrone and CA significantly reduced the effect of dipyrone. Therefore, evidence indicated that CA acted as an anticytotoxic and antigenotoxic agent counteracting damage induced by dipyrone.

4,6-Dinitro-7-(thiazol-2-ylamino)benzo[c][1,2,5]oxadiazole 1-oxide

4,6-Dinitro-7-(thiazol-2-ylamino)benzo[c][1,2,5]oxadiazole 1-oxide was synthesized by a SNAr reaction between 7-chloro-4,6-dinitrobenzofuroxan and 2-aminothiazole. The structure of the newly synthesized compound (45% yield) was elucidated based on 1H-NMR, 13C-NMR, NOESY-1D, ESI-MS, UV-Vis, and FT-IR techniques.

A natural occurring bifunctional CPD/(6-4)-photolyase from the Antarctic bacterium Sphingomonas sp. UV9

Photolyases are flavoproteins that repair ultraviolet-induced DNA lesions (cyclobutane pyrimidine dimer or CPD, and pyrimidine (6-4) pyrimidone photoproducts or (6-4)-PPs), using blue light as an energy source. These enzymes are substrate specific, meaning that a specific photolyase repairs either a CPD or a (6-4)-PP. In this work, we produced a class II CPD-photolyase (called as PhrSph98) from the Antarctic bacterium Sphingomonas sp. UV9 by recombinant DNA technology and we purified the enzyme using immobilized metal affinity chromatography. By using an immunochemistry assay, with monoclonal antibodies against CPD and (6-4)-PP, we found that PhrSph98 repairs both DNA lesions. The result was confirmed by immunocytochemistry using immortalized non-tumorigenic human keratinocytes. Results from structure prediction, pocket computation, and molecular docking analyses showed that PhrSph98 has the two expected protein domains (light-harvesting antenna and a catalytic domain), a larger catalytic site as compared with photolyases produced by mesophilic organisms, and that both substrates fit the catalytic domain. The results obtained from predicted homology modeling suggest that the electron transfer pathway may occur following this pathway: Y389-W369-W390-F376-W381/FAD. The evolutionary reconstruction of PhrSph98 suggests that this is a missing link that reflects the transition of (6-4)-PP repair into the CPD repair ability for the class II CPD-photolyases. To the best of our knowledge, this is the first report of a naturally occurring bifunctional, CPD and (6-4)-PP, repairing enzyme. KEY POINTS: • We report the first described bifunctional CPD/(6-4)-photoproducts repairing enzyme. The bifunctional enzyme reaches the nuclei of keratinocyte and repairs the UV-induced DNA damage. The enzyme should be a missing link from an evolutionary point of view. The enzyme may have potential uses in the pharmaceutical and cosmetic industries.

Improved antiproliferative activity of novel Pulsatilla saponin D/α-hederin derivatives containing nitric oxide donors

Conjugates of PSD and furoxan exhibited synergetic effects on enhancing antiproliferative activity and reducing hemolytic toxicity.