Reduced Level of Prolylhydroxyproline in the Nail Clippings of Oral Cancer Patients and its Role as an Activator of Phospholipase C-β2.

Background: The oral cancer microenvironment plays an important role in the development and progression of the disease which depicts the heterogeneous nature of diseases. Several cellular and non-cellular factors, including dipeptides, have been reported to drive tumor progression and metastasis. Among various secreted molecules in the tumor microenvironment, prolylhydroxyproline (Pro-Hyp) is a collagen-degraded product with specific relevance to fibrosis and oral cancer. However, the detection of Pro-Hyp in the nails of oral cancer patients is a potential biomarker, and our understanding of the biological relevance of Pro-Hyp is highly limited.

Methods: Here, the authors have attempted to use a novel and in-house vertical tube gel electrophoresis (VTGE) protocol to evaluate the level of Pro-Hyp in the nails of oral cancer patients and healthy subjects. Furthermore, we employed molecular docking and molecular dynamics (MD) simulations to predict the biological function of Pro-Hyp. ADME profiles such as the druglikeness and leadlikeness of Pro-Hyp and a known PLC-β2 activator, m-3M3FBS, were evaluated by the SWISS-ADME server.

Results: We report that among various key metabolites, Pro-Hyp, a dipeptide, is reduced in the nails of oral cancer patients. Molecular docking and MD simulations helped to suggest the potential role of Pro-Hyp as an activator of Phospholipase C-β2 (PLC-β2). Pro-Hyp displayed good binding affinity (-7.6 kcal/mol) with specific interactions by a conventional hydrogen bond with key residues, such as HIS311, HIS312, VAL641, and GLU743. MD simulations showed that the activator binding residues and stability of complexes are similar to the well-known activator m-3M3FBS of PLC-β2. ADME profiles such as the druglikeness and leadlikeness of Pro-Hyp were found to be highly comparable and even better than those of m-3M3FBS.

Conclusion: This study is one of the first reports on Pro-Hyp as a metabolite biomarker in the nails of oral cancer patients. Furthermore, the implications of Pro-Hyp are proposed to activate PLC-β2 as a pro-tumor signaling cascade. In the future, diagnostic and therapeutic approaches may be explored as biomarkers and mimetic of Pro-Hyp.