Expression of Salivary Secretory Leukocyte Protease Inhibitor in Smokers, Leukoplakia and OSCC

Introduction: The unsatisfactory prognosis and morbidity by contemporary treatment modality of carcinoma and late diagnosis due to lack of simple non-invasive early marker has driven researchers to explore and identify new molecules which can be used as markers or for targeted therapy for cancer. Secretory Leucocyte Protease Inhibitor (SLPI) is one such molecule of interest, whose association with smoking and cancer is controversial and less researched. Aim: To estimate and compare the salivary levels of SLPI in healthy control, smokers with and without leukoplakia and oral squamous cell carcinoma. Materials and Methods: A prospective, case-control study was conducted in which whole unstimulated saliva samples were collected from total of 80 participants which included 20 controls, 20 smokers without leukoplakia, 20 smokers with leukoplakia and 20 cases of Oral Squamous Cell Carcinoma (OSCC). Salivary SLPI levels were measured using enzyme-linked immunosorbent assay and comparison of SLPI levels between groups was done using Mann Whitney Test. Results: The study results showed a higher concentration of SLPI in controls than leukoplakia and OSCC. The median SLPI of controls was 144 ng/mL, while concentration of SLPI in smokers without leukoplakia, with leukoplakia and squamous cell carcinoma were 101 ng/mL, 112 ng/mL and 113 ng/mL, respectively. Conclusion: Results from this study suggest that smoking, premalignancy and OSCC are associated with lower concentrations of salivary SLPI compared to controls. Hence, salivary SLPI could be a potent biomarker in cancer diagnosis and can have a great value in immune therapy of OSCC.