Background: Oral cancer (OC) is the sixteenth most prevalent cancer worldwide . More importantly, 8% of OC arises from oral potentially malignant disorders (OPMD). Despite the high incidence, there are no biomarkers for the early detection of OC, and patients are often diagnosed at their advanced stages (5-year overall patient survival is approximately 50%). When OC is detected at an early stage (Stage I or II), the overall five-year survival rate exceeds 80%, whereas late-stage diagnosis (Stage III or IV) results in a survival rate of only 20% . miRNAs are small non-coding RNA molecules that can regulate multiple genes and are involved in various biological processes, including cell differentiation, development, and disease. Therefore, this study aimed to discover, develop and validate novel saliva-based microRNA signatures to early diagnose OC and predict the risk of developing OC in patients with oral potentially malignant disorders (OPMD).
Methods: Eight candidate miRNAs (miR-A, B, C, D, E, F, G, H) were discovered when considering The Cancer Genome Atlas (TCGA) miRNA sequencing data and in-house small RNA sequencing of saliva samples (OC: n=8, and controls: n=8). Expression levels of candidate miRNAs were validated in saliva samples of OC (n=50), OPMD (n=52), and controls (n=60) using quantitative real-time PCR. Further, validation was carried out in tumour tissue and normal oral cavity tissue samples of OC (n=6) and controls (n=5), respectively.
Results: We have developed miRNA signatures for the early detection of OC and discrimination of OC from OPMD patients. The discriminative efficiency of our eight-miRNA signature between OC and controls was based on Area Under Curve (AUC): 0.954, sensitivity: 86%, specificity: 90%, positive predictive value (PPV) of 87.8%, and negative predictive value (NPV) of 88.5% whereas between OC and OPMD was based on AUC: 0.911, sensitivity: 90%, specificity: 82.7%, PPV of 74.2% and NPV of 89.6%. More importantly, we have developed a risk probability score to stratify OPMD patients at risk of developing OC.
Conclusions: Our results highlight that salivary miRNAs can be used as biomarkers to diagnose OC and predict OC risk in OPMD patients early. Especially the risk probability score provides promising results in stratifying the OPMD patients at high risk of developing OC. However, validating the above signatures in larger cohorts and high-risk populations may benefit their clinical translation.