Salivary microRNA: discovery, characterization, and clinical utility for oral cancer detection

Abstract

Purpose: We have previously shown that a transcriptome is found in saliva and subpanels of these mRNAs can be used as oral cancer biomarkers. In this study, we measured the presence of microRNAs (miRNA) in saliva and determined their potential as an additional set of oral cancer biomarkers.

Experimental design: A total of 314 miRNAs were measured using reverse transcriptase-preamplification-quantitative PCR in 12 healthy controls. Degradation pattern of endogenous and exogenous saliva miRNAs were measured at room temperature over time. Selected miRNAs were validated in saliva of 50 oral squamous cell carcinoma patients and 50 healthy matched control subjects.

Results: We detected approximately 50 miRNAs in both the whole and supernatant saliva. Endogenous saliva miRNA degraded much slower compared with exogenous miRNA. Two miRNAs, miR-125a and miR-200a, were present in significantly lower levels (P < 0.05) in the saliva of oral squamous cell carcinoma patients than in control subjects.

Conclusions: Both whole and supernatant saliva of healthy controls contained dozens of miRNAs, and similar to saliva mRNAs, these miRNAs are stable. Saliva miRNAs can be used for oral cancer detection.

Figure 1. Stability of endogenous and exogenous miRNA in saliva

At time 0, exogenous miR-124a was added to the supernatant phase of saliva to a final concentration of 50 μM. The saliva was incubated at room temperature for 30 min. At each time point, 400-μL saliva aliquots were removed in triplicate for RT-preamp-qPCR of miR-124a and miR-191. The amount of RNA quantified at each time point was normalized to time 0. Error bars represent standard deviation.