Method: We evaluated mutant mtDNA from normal and tumorous tissues and serum mtDNA obtained preoperatively and 4 weeks postoperatively,and of those, 46 were diagnosed postoperatively as having a good prognosis (r/m-), and 18 had a local recurrence and/or distant metastasis within 9 months postoperatively (r/m+). Overall, 256 clinical samples from 64 subjects with OSCC were analyzed using quantitative real-time PCR combined with high-resolution melting curve analysis (qPCR-HRMA).
Result: We detected three novel somatic mutations in the regions of D-loop (C:G to T:A at position 68), 12S-rRNA (A:T to G:C at position 1107) in Sa3 cell line, and 16S-rRNA (T:A to C:G at position 3190) in the HSC-4 cell line. All patients with a poor prognosis (recurrence and/or distant metastasis cases, r/m+) had significantly (P<0.05) higher amounts of mutant mtDNAs in the tumoral tissues compared with the r/m- group. More importantly, on the blood test with the cut-off point characterized by receiver operating characteristic (ROC) curve analysis, while the vast majority of serum mtDNA samples obtained 4 weeks postoperatively in the r/m+ cases maintained significantly higher amounts of mutant mtDNAs, the r/m- cases did not, and they had no recurrences and were disease free.
Conclusion: Our results supported the concept that measuring the circulating serum mtDNA could be an appropriate strategy for differential diagnosis in high-risk groups of patients with OSCC postoperatively.