Smoking-induced shifts in salivary exosomal cytokines and amino acid profiles as potential early biomarkers for oral cancer.

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Chronic smoking is an established risk factor for oral cancer (OC). The role of tobacco in oral squamous cell cancer (OSCC) emphasizes the need for non-invasive diagnostic approaches to identify early molecular alterations and improve patient outcomes. Salivary exosomes, which contain proteins, lipids, and nucleic acids, accessible and rich in biological content, making them interesting candidate biomarkers. Saliva samples were collected from non-smokers (n=20), smokers (n=20), and patients with oral cancer (n=20). Salivary exosomes were isolated and characterized using various techniques, including estimation of protein concentrations and amino acid profiling using High-Performance Liquid Chromatography (HPLC). Fourier Transform Infrared (FTIR) spectroscopy analyzed protein and amino acid peaks, while enzyme-linked immunosorbent assay (ELISA) measured pro-inflammatory cytokines IL-6 and IL-8. Elevated levels of salivary exosomal proteins (p=0.017), IL-6 (p=0.008), and IL-8 (p=0.0004), along with significant alterations in amino acid profiles, were observed in smokers compared with non-smokers. Additionally, protein (p=0.005) and IL-6 (p=0.004) levels were significantly elevated in oral cancer compared to non-smoker group. FTIR spectroscopy revealed distinct molecular fingerprints in exosomes, highlighting changes in protein and amino acid concentrations and indicating altered metabolism. This comparative cross-sectional study demonstrated that chronic smoking induces significant biochemical changes in salivary exosomes, establishing them as promising non-invasive biomarkers for early oral cancer detection. Elevated pro-inflammatory cytokines IL-6 and IL-8, along with altered amino acid profiles, may create pre-cancerous conditions. Notably, along with altered amino acid profiles, IL-6 levels progressively increase from smoking to oral cancer, highlighting its potential role in cancer progression.