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Objective:To ascertain the variations of mitochondrion DNA（mtDNA） in mouse tumors and to inquire into the relationship between mutations of mtDNA and carcinogenesis.Methods:The variations of D-loop

ND3 and tRNA

Met+Glu+Ile

gene fragments of mtDNA from six tumor cell lines of mice were analyzed by PCR technology with restriction fragment length polymorphism analysis（polymerase chain reaction-restriction fragment length polymorphism

PCR-RFLP） and single strand conformation polymorphism analysis（SSCP-PCR） method.Results:ND3 and tRNA

Met+Glu+Ile

gene fragments of mtDNA from the tumors showed no variation in 27 endonuclease sites;D-loop of mtDNA from Hca-F had an additional endonuclease sites of HinfⅠin contrast to that of the inbred mouse.Deeply analyzed by PCR-SSCP

the D-loop of mtDNA was found to possess mutations in 4 of 6 tumors.Conclusion:D-loop is the hot spot of tumor mtDNA mutation which can act as contributors to the carcinogenic process.