Paper Title
In Silico Identification of Potential Inhibitor for TP53-Induced Glycolysis and Apoptosis Regulator in Head and Neck Squamous Cell Carcinoma

Abstract
Introduction: The TP53-induced glycolysis and apoptosis regulator (TIGAR) is a downstream target of TP53, which inhibits the process of aerobic glycolysis and facilitates the protection of tumor cells from the apoptotic processes. The over expression of TIGAR have been reported in head and neck cancer patients samples and their association with head and neck tumor progression. Therefore, the aim of our study identifies a novel FDA approved anticancer inhibitor against mutated TP53-induced glycolysis and apoptosis regulator (TIGAR) through drug repurposing approach. Materials and Methods: The library of 105 FDA approved anticancer compounds were screened using molecular docking approach against Wild-Type (WT) TIGAR (PDB:3DCY) and mutated (Mut) TIGAR. Specific mutations in TIGAR were identified using cBioPortal, a cancer genomics database and mutated structure was generated using SWISS-MODEL. Molecular Docking study of TIGAR with the selected Food and Drug Administration (FDA) approved anti-cancer drugs was performed using AutoDock-Vina and AutoDock-Tools. Molecular dynamics simulation were performed for 100ns to validate the results obtained from Molecular Docking. Protein- Protein network analysis was done using String database to identify interactions of TIGAR with other associated genes. Results: Detection of TIGAR (TIGARWT and TIGARMut (R88W)) in Head and Neck cancer patient samples showed that out of 510 sequenced cases/patients there is alteration in 17(3%) patients. The virual drug screening results showed that out of 105, 45 drugs exhibited high binding affinity with TIGAR and Trabectedin showed highest binding affinity with both TIGARWT (-13.3 Kcal/mol) as well as TIGARMut (R88W) (-13.8 Kcal/mol). Molecular Docking analysis of Trabectedin with receptors showed electrostatic interactions with the amino acid residues ARG10, ASN17, ILE22, TYR92, ARG203, THR230 and PRO231 present at the active site of TIGARMut (R88W). Our findings suggest that Trabectedin can be used as an inhibitor for TIGARMut (R88W)) and can be used as an anti-glycolytic agent which may be used as a novel therapeutic agent for head and neck cancer. String analysis revealed that metabolic related genes, HK2, PFKFB1, PFKM, PFKP, PFKL, FBP1 are closely associated with TIGAR in HNSCC. The MD Simulation study of Trabected in with TIGARMut was found to be more stable as compared to TIGARWT. Therefore, Trabectedin can be a promising agent to target TIGARMut in HNSCC. However, further investigation and validation to understand the molecular mechanisms of regulation of Trabectedin in Head and Neck cancer need to be investigated. Conclusion: In normal cells, TIGAR functions to promote antioxidative activities and inhibit glycolysis, in order to maintain the levels of intracellular ROS. The elevated levels of TIGAR have been shown for several human malignancies including head and neck cancer. The down-regulation of TIGAR in HNSCC has been shown to be correlated with HNSCC growth inhibition. However, the majority of functions of TIGAR in HNSCC so far remain unclear. In the present study, we reveal the expression and mutational profile of TIGAR in HNSCC through TCGA database. In TIGAR, R88W was found to be the most common mutation in HNSCC. Molecular docking studies revealed trabectedin as an effective anti-cancer inhibitor against TIGAR. Molecular dynamics simulation results validated the docking results that suggests that the mutated TIGAR and trabectedin forms a very stable complex. Therefore, in our study, trabectedin through in-silico bioinformatics analysis and drug repurposing approach revealed to be a promising candidate against mutated TIGAR in HNSCC.