Objective To investigate the frequency of mitochondrial DNA（mtDNA） D-loop hypervariable region Ⅱ HVR Ⅱ） and hypervariable region Ⅲ（HVR Ⅲ） mutations in oral squamous cell carcinoma（OSCC） and their orrelation to provide the new targets for the prevention and treatment of OSCC. Methods The D-loop HVR Ⅱ and VR Ⅲ regions of mtDNA in seven cases with OSCC tissues, matched with paracancerous tissues and normal mucosa issues from the same case, were amplified by polymerase chain raction（PCR）, then were detected by direct equencing to find the mutantsites after the comparison of all sequencing results with the mtDNA Cambridge sequence n the GenBank database. Results 82（56 species） nucleotide changes, with 51（26 species） nucleotide polymor - hism, were found after the comparison of all sequencing results with the mtDNA Cambridge sequence in the Gen- ank database. 31（30 species） mutations, with 21 located within the HVR Ⅱ and HVR Ⅲ regions, were found in 3 umor tissue samples, their paracancerous and normal mucosa tissue were found more polymorphic changes but no utation. The mtDNA D-loop HVR Ⅱ and HVR Ⅲ regions mutation rate was 42.9%（3/7） in OSCC. Conclusion The tDNA D-loop HVR Ⅱ and HVR Ⅲ regions were highly polymorphic and mutable regions in OSCC． It suggested hat the D -loop HVR Ⅱ and HVR Ⅲ regions of mtDNA might play a significant role in the tumorigenesis f OSCC. It may become new targets for the gene therapy of OSCC by regulating the above indexes.
