Preliminary study on relationship between DNA immortal strands and tumor stem cells

    ZHANG Feng£¬LI Qing, ZHU Xiaoª²Hui, ZHAO Yiª²Ling£¬MA Fuª²Cheng, WANG Wenª²Yong, ZHANG Liª²Ying, NIE Lei, HONG Liu

    Department of Pathology, Xijing Hospital, Fourth Military Medical University, Xi¬ðan 710033, China

    ¡¾Abstracts¡¿ AIM: To study the relationship between DNA immortal strands and tumor stem cells. METHODS: Initiation and promotion twoª²stage chemical carcinogenesis method was used to induce cutaneous tumors in the mouse back skin. DNA label retaining method and immunolabelling assay were used to chase the changes of BrdU positive cells in mouse skin and tumor tissues. DNA ploidy image analysis was performed to detect the karyotype of tumor cells. RESULTS: Four months after tumor induction, there were 1-3 tumors in the back of 17 mice. During the chase period, immunolabelling results showed that an extremely high percentage of keratinocytes and cutaneous tumor cells incorporated the BrdU at 24 h after final BrdU labeling. Some keratinocytes of mice labeled with BrdU during juvenile period were BrdU positive for at least 60 d after the final BrdU injection. Most of these cells were located within the bulge of hair follicle and some scattered in the basal layer of skin. In contrast, the keratinocytes labeled with BrdU during adult period were BrdU negative completely at 30 d after the final BrdU injection. BrdU positive cells were observed in tumor tissues for at least 30 d but not more than 60 d after the final BrdU injection. DNA ploidy image analysis showed that all the tumor cells were aneuploidy. CONCLUSION: We have confirmed both the existence of immortal DNA strands and the cosegregation of chromosomes that bear them in mouse epidermal stem cells. Our findings suggest that there may be immortal DNA strands which intend to distribute randomly in tumor stem cells. ......