Design, Synthesis, and Evaluation of Diazeniumdiolate-Based DNA Cross-Linking Agents Activatable by Glutathione S-Transferase

One Stone Two Birds: Redox-Sensitive Colocalized Delivery of Cisplatin and Nitric Oxide through Cascade Reactions

Bio-orthogonal bond-cleavage reactions have been used in cancer therapy for improving the biological specificity of prodrug activation, but the spatiotemporal consistency of reactants is still a huge challenge. Although, in most cases, the cleavage catalysts and caged prodrugs are administrated separately, it is difficult to avoid the reactions in advance before they meet at the tumor site. Herein, we design and construct novel coordinative nanoparticles, integrating two prodrugs A and B as ligands and ferric ions as coordinative centers. After nanoparticles accumulated in tumor through passive targeting, inert Pt(IV) prodrug A is specifically and spontaneously reduced into active Pt(II) cisplatin, which acts as the cleavage catalyst to subsequently initiate the in situ bio-orthogonal depropargylation of B, that is, O ²-propargyl nitric oxide (NO) donor. The unique structure of coordinative nanoparticles ensures the spatiotemporal consistency of reactants (prodrugs A and B) and products (cytotoxic cisplatin and tumoricidal NO) for the bio-orthogonal bond-cleavage reaction, which leads to an improved synergistic therapeutic activity for triple-negative breast cancer (TNBC). This new concept of bio-orthogonal dual-prodrug coordinative nanoparticles may inspire further applications in bio-orthogonal chemistry and drug delivery for combination chemotherapy.

Synthesis and evaluation of novel naphthol diazenyl scaffold based Schiff bases as potential antimicrobial and cytotoxic agents against human colorectal carcinoma cell line (HT-29)

BACKGROUND

In search of new antimicrobial and cytotoxic agents, a series of new naphthol diazenyl scaffold based Schiff bases (NS1-NS23) was efficiently synthesized by condensation of 2-hydroxy naphthaldehyde azo dyes with various substituted aromatic/heteroaromatic/aliphatic amines.

METHODOLOGY

The synthesized derivatives were characterized by various physicochemical and spectral techniques and assessed for in vitro antimicrobial and cytotoxic potential against human colorectal carcinoma cell line (HT-29). The active derivatives were further evaluated for their apoptotic potential by Annexin-V/propidium iodide double staining assay using flow cytometer and analyzed for cell-cycle arrest studies.

RESULTS AND CONCLUSION

The derivative NS-2 was found maximum active against E. coli, S. enterica and B. subtilis. The derivatives NS-12, NS-15, NS-21, and NS-23 showed maximum antifungal activity against A. fumigatus. The maximum cytotoxicity was observed from the derivatives NS-2, NS-8, NS-21, and NS-23 towards HT-29 cell line with IC50 between 4 and 19 μg/ml. More than 90% and 62% of the cells were found in the apoptotic phase on treatment with NS-2 and NS-21 respectively in comparison to the 68% for doxorubicin. Further, these derivatives arrested the cell growth in S and G2/M phase of the cell cycle.

Glutathione Transferases: Potential Targets to Overcome Chemoresistance in Solid Tumors

Multifunctional enzymes glutathione transferases (GSTs) are involved in the development of chemoresistance, thus representing a promising target for a novel approach in cancer treatment. This superfamily of polymorphic enzymes exhibits extraordinary substrate promiscuity responsible for detoxification of numerous conventional chemotherapeutics, at the same time regulating signaling pathways involved in cell proliferation and apoptosis. In addition to upregulated GST expression, different cancer cell types have a unique GST signature, enabling targeted selectivity for isoenzyme specific inhibitors and pro-drugs. As a result of extensive research, certain GST inhibitors are already tested in clinical trials. Catalytic properties of GST isoenzymes are also exploited in bio-activation of specific pro-drugs, enabling their targeted accumulation in cancer cells with upregulated expression of the appropriate GST isoenzyme. Moreover, the latest approach to increase specificity in treatment of solid tumors is development of GST pro-drugs that are derivatives of conventional anti-cancer drugs. A future perspective is based on the design of new drugs, which would selectively target GST overexpressing cancers more prone to developing chemoresistance, while decreasing side effects in off-target cells.

Glutathione S-transferase π: a potential role in antitumor therapy

Glutathione S-transferase π (GSTπ) is a Phase II metabolic enzyme that is an important facilitator of cellular detoxification. Traditional dogma asserts that GSTπ functions to catalyze glutathione (GSH)-substrate conjunction to preserve the macromolecule upon exposure to oxidative stress, thus defending cells against various toxic compounds. Over the past 20 years, abnormal GSTπ expression has been linked to the occurrence of tumor resistance to chemotherapy drugs, demonstrating that this enzyme possesses functions beyond metabolism. This revelation reveals exciting possibilities in the realm of drug discovery, as GSTπ inhibitors and its prodrugs offer a feasible strategy in designing anticancer drugs with the primary purpose of reversing tumor resistance. In connection with the authors' current research, we provide a review on the biological function of GSTπ and current developments in GSTπ-targeting drugs, as well as the prospects of future strategies.

Glutathione transferases: substrates, inihibitors and pro-drugs in cancer and neurodegenerative diseases

Glutathione transferase classical GSH conjugation activity plays a critical role in cellular detoxification against xenobiotics and noxious compounds as well as against oxidative stress. However, this feature is also exploited by cancer cells to acquire drug resistance and improve their survival. As a result, various members of the family were found overexpressed in a number of different cancers. Moreover several GST polymorphisms, ranging from null phenotypes to point mutations, were detected in members of the family and found to correlate with the onset of neuro-degenerative diseases. In the last decades, a great deal of research aimed at clarifying the role played by GSTs in drug resistance, at developing inhibitors to counteract this activity but also at exploiting GSTs for prodrugs specific activation in cancer cells. Here we summarize some of the most important achievements reached in this lively area of research.

Nitric Oxide Donor-Based Cancer Therapy: Advances and Prospects

The increasing understanding of the role of nitric oxide (NO) in cancer biology has generated significant progress in the use of NO donor-based therapy to fight cancer. These advances strongly suggest the potential adoption of NO donor-based therapy in clinical practice, and this has been supported by several clinical studies in the past decade. In this review, we first highlight several types of important NO donors, including recently developed NO donors bearing a dinitroazetidine skeleton, represented by RRx-001, with potential utility in cancer therapy. Special emphasis is then given to the combination of NO donor(s) with other therapies to achieve synergy and to the hybridization of NO donor(s) with an anticancer drug/agent/fragment to enhance the activity or specificity or to reduce toxicity. In addition, we briefly describe inducible NO synthase gene therapy and nanotechnology, which have recently entered the field of NO donor therapy.