P38 MAPK pathway and its interaction with TRF2 in cisplatin induced chemotherapeutic response in head and neck cancer

TRF2 is a telomere binding protein, a component of the shelterin complex that plays a major role in maintaining the integrity of the genome. TRF2 is over-expressed in a number of human cancers including Head and Neck cancer and might play a key role in tumor initiation and development. p38 MAPK signaling pathway is strongly activated in response to various environmental and cellular stresses and thus overexpressed in most of the Head and Neck cancer cases. In this study, we investigated potential interactions of TRF2 with p38 in HNSCC cells and patient samples. Using in silico experiments, we identified interface polar residue Asp-354 of p38 and Arg-492, Arg-496 of TRF2 as protein-protein interaction hotspots. In addition to these interactions, Arg-49 residue of p38 was also found to interact with Glu-456 of TRF2. A detailed understanding of how phosphorylated and unphosphorylated state of p38 protein can influence the stability, specificity and to some extent a conformational change of p38-TRF2 binding is presented. Silencing of TRF2 significantly decreased the phosphorylation of p38 in HNSCC cells which was confirmed by western blot, immunofluorescence and co-immunoprecipitation and alternatively inhibiting p38 using p38 inhibitor (SB 203580) decreased the expression of TRF2 in HNSCC cells. Furthermore, we checked the effect of TRF2 silencing and p38 inhibition in cisplatin induced chemosensitivity of SCC-131 cells. TRF2 silencing and p38 inhibition chemosensitize HNSCC cells to cisplatin. Thus, targeting TRF2 in combinatorial therapeutics can be a treatment modality for Head and Neck cancer which involves inhibition of p38 MAPK pathway.