Analysis of G-banding in tumor cell lines derived from human neural stem cells

BACKGROUND： The application of neural stem cell （NSC） is restricted because of its tumorigenesis, and the possible pathogenesis needs investigation. OBJEETIVE： To compare the differences of chromosomal G-banding between human NSCs （hNSCs） derived tumor cell line and hNSCs derived normal cell lines. DESIGN： A randomized controlled observation SETTING ： Building of Anatomy, Peking University Health Science Center MATERIALS ①The hNSC lines and hNSC-derived tumor cell lines were provided by the Research Center of Stem Cells, Peking University; DMEM/F12 （1：1） medium, N2 additive, B27 additive epidermal growth factor （EGF） and basic fibroblast growth factor （bFGF） were produced by GIBCO BRL Company （USA）; fetal bovine serum by HYCLONE Company （USA）. METHODS： The experiments were carried out in the Department of Genetics, Peking University Health Science Center from February 2003 to July 2004. Human fetal striatal NSCs were inoculated hypodermically on the right scapular of nude mice; Normal human fetal striatal NSCs were cultured to 5-8 passages as controls. Karyotyping was performed on the 5^th passage of hNSC-derived tumor cells at 6 weeks after hNSC transplantation into nude mice （T1） and tumor cells at 15 weeks after transplantation （T2）. Metaphase chromosomes were examined with microscope, G-banding cytogenetic analysis and karyotyping were performed according to the Cytoscan Karyotyping FISH and CGH software system （United biotechnology USA Corporation）. MAIN OUTCOME MEASURES： G-banded analytical results of human fetal striatal nerve stem cells derived tumor cell lines （T1 and T2） of metaphase chromosomes were observed. RESULTS： ① Chromosome analysis of hNSC-derived tumor cell lines 1 （T1）： Twenty-five well-spread metaphases were randomly selected for analysis. The karyotypes were 64, XX （8, 32%）; 65, XX （1, 4%）; 67, XX （5, 20%）; 68, XX （11, 44%）. The modal number of chromosomes in this cell lines was 68, which were all hypotriploid. The analysis of 8 G-banded karyotypes showed that about （70.2±3.4）% of the chromosomes lost normal figures in each karyotype, and the chromosomes with structural rearrangements, including deletion and translocation, were observed, most of which changed in a random way.② Chromosome analysis of hNSC-derived tumor cell lines 2（T2）： Twenty-five well-spread metaphases were randomly selected for analysis. The karyotypes were 64, XX （2, 8%）; 65, XX （1, 4%）; 66, XX （2, 8%）; 67, XX （5, 20%）; 68, XX （9, 36%）; 69, XX （6, 24%）. The modal number of chromosomes in this cell lines was 68, which were hypotriploid and triploid. The analysis of 8 G-banded karyotypes indicated that about （75.1±4.5）% of the chromosomes were abnormal in each karyotype. Chromosomes with structure alterations were observed, including deletion, translocation and dicentric. ③ Chromosome analysis of human fetal striatal NSC-derived normal cell lines： Twenty-five well-spread metaphases were analyzed randomly and the karyotypes were all 46, XX. Eight randomly selected G-banded karyotypes were analyzed and found no chromosome aberrations, and hNSC cells were all normal diploid. CONCLUSION： Chromosomal abnormalities are preferentially involved in numerical and structural rearrangements in the hNSC-derived tumor cell lines that derived from the same hNSC cell line, which suggest us to disclose intrinsic mechanisms of tumorigenesis of NSCs.