The Therapeutic Potential of Imidazole or Quinone-Based Compounds as Radiosensitisers in Combination with Radiotherapy for the Treatment of Head and Neck Squamous Cell Carcinoma

Recent drug design strategies and identification of key heterocyclic scaffolds for promising anticancer targets

Cancer, a noncommunicable disease, is the leading cause of mortality worldwide and is anticipated to rise by 75% in the next two decades, reaching approximately 25 million cases. Traditional cancer treatments, such as radiotherapy and surgery, have shown limited success in reducing cancer incidence. As a result, the focus of cancer chemotherapy has switched to the development of novel small molecule antitumor agents as an alternate strategy for combating and managing cancer rates. Heterocyclic compounds are such agents that bind to specific residues in target proteins, inhibiting their function and potentially providing cancer treatment. This review focuses on privileged heterocyclic pharmacophores with potent activity against carbonic anhydrases and kinases, which are important anticancer targets. Evaluation of ongoing pre-clinical and clinical research of heterocyclic compounds with potential therapeutic value against a variety of malignancies as well as the provision of a concise summary of the role of heterocyclic scaffolds in various chemotherapy protocols have also been discussed. The main objective of the article is to highlight key heterocyclic scaffolds involved in recent anticancer drug design that demands further attention from the drug development community to find more effective and safer targeted small-molecule anticancer agents.

Tolerable treatment of glioblastoma with redox-cycling 'mitocans': a comparative study in vivo

Objectives: The present study describes a pharmacological strategy for the treatment of glioblastoma by redoxcycling 'mitocans' such as quinone/ascorbate combination drugs, based on their tumor-selective redox-modulating effects and tolerance to normal cells and tissues.Methods: Experiments were performed on glioblastoma mice (orthotopic model) treated with coenzyme Q0/ascorbate (Q0/A). The drug was injected intracranially in a single dose. The following parameters were analyzed in vivo using MRI orex vivo using conventional assays: tumor growth, survival, cerebral and tumor perfusion, tumor cell density, tissue redox-state, and expression of tumor-associated NADH oxidase (tNOX).Results: Q0/A markedly suppressed tumor growth and significantly increased survival of glioblastoma mice. This was accompanied by increased oxidative stress in the tumor but not in non-cancerous tissues, increased tumor blood flow, and downregulation of tNOX. The redox-modulating and anticancer effects of Q0/A were more pronounced than those of menadione/ascorbate (M/A) obtained in our previous study. No adverse drug-related side-effects were observed in glioblastoma mice treated with Q0/A.Discussion: Q0/A differentiated cancer cells and tissues, particularly glioblastoma, from normal ones by redox targeting, causing a severe oxidative stress in the tumor but not in non-cancerous tissues. Q0/A had a pronounced anticancer activity and could be considered safe for the organism within certain concentration limits. The results suggest that the rate of tumor resorption and metabolism of toxic residues must be controlled and maintained within tolerable limits to achieve longer survival, especially at intracranial drug administration.

In-silico and in-vitro functional validation of imidazole derivatives as potential sirtuin inhibitor

Introduction

Epigenetic enzymes can interact with a wide range of genes that actively participate in the progression or repression of a diseased condition, as they are involved in maintaining cellular homeostasis. Sirtuins are a family of Class III epigenetic modifying enzymes that regulate cellular processes by removing acetyl groups from proteins. They rely on NAD+ as a coenzyme in contrast to classical histone deacetylases (HDACs) (Class I, II, and IV) that depend on Zn+ for their activation, linking their function to cellular energy levels. There are seven mammalian sirtuin isoforms (Sirt1-7), each located in different subcellular compartments. Sirtuins have emerged as a promising target, given that inhibitors of natural and synthetic sources are highly warranted. Imidazole derivatives are often investigated as sirtuin regulators due to their ability to interact with the binding site and modulate their activity. Imidazole bestows many possible substitutions on its ring and neighboring atoms to design and synthesize derivatives with specific target selectivity and improved pharmacokinetic properties, optimizing drug development.

Materials and methods

Ligand preparation, protein preparation, molecular docking, molecular dynamics, density function theory (DFT) analysis, and absorption, distribution, metabolism, and excretion (ADME) analysis were performed to understand the interacting potential and effective stability of the ligand with the protein. RT-PCR and Western blot analyses were performed to understand the impact of ligands on the gene and protein expression of Class III HDAC enzymes.

Results and discussion

We evaluated the sirtuin inhibition activity of our in-house compound comprised of imidazole derivatives by docking the molecules with the protein data bank. ADME properties of all the compounds used in the study were evaluated, and it was found that all fall within the favorable range of being a potential drug. The molecule with the highest docking score was analyzed using DFT, and the specific compound was used to treat the non-small cell lung cancer (NSCLC) cell lines A549 and NCI-H460. The gene and protein expression data support the in-silico finding that the compound Ethyl 2-[5-(4-chlorophenyl)-2-methyl-1-H-Imidazole-4-yl) acetate has an inhibitory effect on nuclear sirtuins. In conclusion, targeting sirtuins is an emerging strategy to combat carcinogenesis. In this study, we establish that Ethyl 2-[5-(4-chlorophenyl)-2-methyl-1-H-Imidazole-4-yl) acetate possesses a strong inhibitory effect on nuclear sirtuins in NSCLC cell lines.

Redox-Cycling "Mitocans" as Effective New Developments in Anticancer Therapy

Our study proposes a pharmacological strategy to target cancerous mitochondria via redox-cycling "mitocans" such as quinone/ascorbate (Q/A) redox-pairs, which makes cancer cells fragile and sensitive without adverse effects on normal cells and tissues. Eleven Q/A redox-pairs were tested on cultured cells and cancer-bearing mice. The following parameters were analyzed: cell proliferation/viability, mitochondrial superoxide, steady-state ATP, tissue redox-state, tumor-associated NADH oxidase (tNOX) expression, tumor growth, and survival. Q/A redox-pairs containing unprenylated quinones exhibited strong dose-dependent antiproliferative and cytotoxic effects on cancer cells, accompanied by overproduction of mitochondrial superoxide and accelerated ATP depletion. In normal cells, the same redox-pairs did not significantly affect the viability and energy homeostasis, but induced mild mitochondrial oxidative stress, which is well tolerated. Benzoquinone/ascorbate redox-pairs were more effective than naphthoquinone/ascorbate, with coenzyme Q0/ascorbate exhibiting the most pronounced anticancer effects in vitro and in vivo. Targeted anticancer effects of Q/A redox-pairs and their tolerance to normal cells and tissues are attributed to: (i) downregulation of quinone prenylation in cancer, leading to increased mitochondrial production of semiquinone and, consequently, superoxide; (ii) specific and accelerated redox-cycling of unprenylated quinones and ascorbate mainly in the impaired cancerous mitochondria due to their redox imbalance; and (iii) downregulation of tNOX.

Targeting PI3K/AKT/mTOR Signaling Pathway as a Radiosensitization in Head and Neck Squamous Cell Carcinomas

Globally, there are over half a million new patients with head and neck squamous cell carcinomas (HNSCC) every year. The current therapeutic approaches to HNSCC are surgery and adjuvant radiotherapy. These approaches carry a high incidence of metastasis or recurrence from HNSCC cells' radioresistance. Recent studies have revealed that a combination with radiosensitizers can be used to improve the radioresistance in HNSCC; however, few agents are approved as radiosensitizers. The constitutive activation of phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is a vitally oncogenic type of signaling that promotes tumorigenesis, metastasis, and radiotherapy resistance in HNSCC. Pharmacological targeting of PI3K/AKT/mTOR signaling pathway is considered a promising strategy of radiosensitization in HNSCC. In this review, we summarize the oncogenic significance of PI3K/AKT/mTOR signaling in HNSCC with radiotherapy resistance and highlight the therapeutic potential of small molecule inhibitors against PI3K/AKT/mTOR signaling for the radiosensitization in HNSCC treatment. It provides a mechanistic framework for the development of new drugs for radiosensitization in HNSCC radiotherapy via targeting PI3K/AKT/mTOR signaling pathway.