Potential inhibitors of RPS6KB2 and NRF2 in head and neck squamous cell carcinoma.

Among the major altered pathways in head and neck squamous cell carcinoma, AKT/mTORC1/S6K and NRF2/KEAP1 pathway are quite significant. The overexpression and overstimulation of proteins from both these pathways makes them the promising candidates in cancer therapeutics. Inhibiting mTOR has been in research from past several decades but the tumour heterogeneity, and upregulation of several compensatory feed-back mechanisms, encourages to explore other downstream targets for inhibiting the pathway. One such downstream effectors of mTOR is S6K2. It is reported to be overexpressed in cancers such as head and neck cancer, breast cancer and prostate cancer. In case of NRF2/KEAP1 pathway, nuclear factor erythroid 2-related factor 2 (NFE2L2 or NRF2) is overexpressed in ∼90% of head and neck squamous cell carcinoma (HNSCC) cases. It associates with poor survival rate and therapeutic resistance in HNSCC treatment. NRF2 pathway is the primary antioxidant pathway in the cell which also serves pro-tumorigenic functions, such as repression of apoptosis, cell proliferation support and chemoresistance. The aim of this work was to explore S6K2 and NRF2 and identify novel and potential inhibitors against them for treating head and neck squamous cell carcinoma. Since the crystal structure of S6K2 was not available at the time of this study, we modelled its structure using homology modelling and performed high throughput screening, molecular dynamics simulations, free energy calculations and protein-ligand interaction studies to identify the inhibitors. We identified natural compounds Crocin and Gypenoside XVII against S6K2 and Chebulinic acid and Sennoside A against NRF2. This study provides a significant in-depth understanding of the two studied pathways and therefore can be used in the development of potential therapeutics against HNSCC.Communicated by Ramaswamy H. Sarma.

Exploring GPR109A Receptor Interaction with Hippuric Acid Using MD Simulations and CD Spectroscopy.

Previous research has indicated that various metabolites belonging to phenolic acids (PAs), produced by gut microflora through the breakdown of polyphenols, help in promoting bone development and protecting bone from degeneration. Results have also suggested that G-protein-coupled receptor 109A (GPR109A) functions as a receptor for those specific PAs such as hippuric acid (HA) and 3-(3-hydroxyphenyl) propionic acid (3-3-PPA). Indeed, HA has a molecular structural similarity with nicotinic acid (niacin) which has been shown previously to bind to GPR109A receptor and to mediate antilipolytic effects; however, the binding pocket and the structural nature of the interaction remain to be recognized. In the present study, we employed a computational strategy to elucidate the molecular structural determinants of HA binding to GPR109A and GPR109B homology models in understanding the regulation of osteoclastogenesis. Based on the docking and molecular dynamics simulation studies, HA binds to GPR109A similarly to niacin. Specifically, the transmembrane helices 3, 4 and 6 (TMH3, TMH4 and TMH6) and Extracellular loop 1 and 2 (ECL1 and ECL2) residues of GRP109A; R111 (TMH3), K166 (TMH4), ECL2 residues; S178 and S179, and R251 (TMH6), and residues of GPR109B; Y87, Y86, S91 (ECL1) and C177 (ECL2) contribute for HA binding. Simulations and Molecular Mechanics Poisson-Boltzmann solvent accessible area (MM-PBSA) calculations reveal that HA has higher affinity for GPR109A than for GPR109B. Additionally, in silico mutation analysis of key residues have disrupted the binding and HA exited out from the GPR109A protein. Furthermore, measurements of time-resolved circular dichroism spectra revealed that there are no major conformational changes in the protein secondary structure on HA binding. Taken together, our findings suggest a mechanism of interaction of HA with both GPR109A and GPR109B receptors.

Identification of potent and novel inhibitors against RAC1: a Rho family GTPase.

Head and Neck Squamous Cell Carcinoma (HNSCC) is one of the most common form of cancer worldwide. It has high incidence and mortality rate making it one of the top causes of cancer related deaths. Tremendous efforts have being made towards treatment of HNSCC but still the overall survival rate hasn't improved much. Unregulated activation of Rho GTPase Ras-related C3 botulinum toxin substrate 1 or Rac1 has been reported in various tumor such as HNSCC, breast cancer, pancreatic cancer, etc. Rac1 is significant in activation and regulation of multiple signaling pathways and it's aberrant activation leads to uncontrolled proliferation, invasion and metastasis which contributes to the hallmarks of cancer. Therefore for treating proliferative disorders such as cancer, inhibition of Rac1 could be a viable approach. Rho GTPases were earlier considered "undruggable" due to their picomolar binding affinity for their guanine nucleotides. In addition presence of high micromolar concentrations of GDP (> 30 µm) and GTP (> 300 µm) in the cell, led to unsuccessful attempts in identification of potent or selective nucleotide competitive GTPase inhibitors. Therefore we identified small molecule inhibitors that target the GEF binding site of the Rho GTPase instead of nucleotide binding site by performing high throughput screening, molecular dynamics simulations, free energy calculations and protein-ligand interaction studies. As a result of this study, we identified four potential inhibitors against RAC1. This study provides a significant in-depth understanding of the Rho GTPases and can prove beneficial in the development of potential therapeutics against HNSCC.

In-silico prediction of potential inhibitors against phosphatidylinositol 3-kinase catalytic subunit alpha involved in head and neck squamous cell carcinomas.

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers, globally. Its high mortality rates remained unaltered in the last three decades, therefore, there is an enormous need for novel therapeutics. The most frequent somatically mutated oncogenic pathway in HNSCC tumors is the Phosphatidylinositol-3-kinases (PI3K) pathway. PI3Ks are lipid kinases involved in the regulation of cell survival, growth and metabolism. PI3Ks phosphorylates PI (4,5) P2 (PIP2) converting it to PI (3, 4, 5) P3 (PIP3). Alterations such as mutation, gene amplification and overexpression in PIK3CA, encoding the catalytic subunit p110α of PI3K pathway were found to be prevalent. The aberrant activation leads to irregulated cell growth due to improper p110α enzymatic activity. p110α is therefore, considered a potential oncogenic target for cancer therapy. The only FDA approved specific inhibitor of p110α is Alpelisib (BYL719). Therefore, designing more effective and specific p110α inhibitors could be a promising strategy in the treatment of HNSCC. The present study aims to find out the potent and novel inhibitors of p110α using High Throughput Screening (HTS) of huge databases (National Cancer Institute (NCI), Life Chemicals, ChemDiv and ChEMBL) and Molecular Dynamic Simulations. As a result, from more than 400,000 compounds, a total of 3 best candidate compounds (Echinacoside, Isoacteoside, K284-4402) were selected and validated for their binding to catalytic site of p110α and stability during Molecular Dynamics (MD) simulations. The binding free energy (calculated from MM-PBSA) of the selected compounds, Echinacoside, Isoacteoside, K284-4402 were -23.43 kcal/mol, -33.02 kcal/mol and -30.57 kcal/mol, respectively, which suggested these compounds bind to p110α with higher affinity than Alpelisib which has binding free energy -20.9 kcal/mol. This study provides a significant in-depth understanding of p110α inhibitors that can be used in the development of potential therapeutics against HNSCC.Communicated by Ramaswamy H. Sarma.

Current and Future Therapeutic Targets: A Review on Treating Head and Neck Squamous Cell Carcinoma.

Head and neck squamous cell carcinoma (HNSCC) continues to be a global public health burden even after a tremendous development in its treatment. It is a heterogeneous cancer of upper aero-digestive tract. The contemporary strategy to treat cancer is the use of anticancer drugs against proteins possessing abnormal expression. Targeted chemotherapy was found successful in HNSCC, but, there is still a stagnant improvement in the survival rates and high recurrence rates due to undesirable chemotherapy reactions, non-specificity of drugs, resistance against drugs and drug toxicity on non-cancerous tissues and cells. Various extensive studies lead to the identification of drug targets capable to treat HNSCC effectively. The current review article gives an insight into these promising anticancer targets along with knowledge of drugs under various phases of development. In addition, new potential targets that are not yet explored against HNSCC are also described. We believe that exploring and developing drugs against these targets might prove beneficial in treating HNSCC.