Adaptation to culture of human embryonic stem cells and oncogenesis in vivo

Abstract

The application of human embryonic stem cells (HESCs) to provide differentiated cells for regenerative medicine will require the continuous maintenance of the undifferentiated stem cells for long periods in culture. However, chromosomal stability during extended passaging cannot be guaranteed, as recent cytogenetic studies of HESCs have shown karyotypic aberrations. The observed karyotypic aberrations probably reflect the progressive adaptation of self-renewing cells to their culture conditions. Genetic change that increases the capacity of cells to proliferate has obvious parallels with malignant transformation, and we propose that the changes observed in HESCs in culture reflect tumorigenic events that occur in vivo, particularly in testicular germ cell tumors. Further supporting a link between culture adaptation and malignancy, we have observed the formation of a chromosomal homogeneous staining region in one HESC line, a genetic feature almost a hallmark of cancer cells. Identifying the genes critical for culture adaptation may thus reveal key players for both stem cell maintenance in vitro and germ cell tumorigenesis in vivo.

Screening of human pluripotent stem cells using CGH and FISH reveals low-grade mosaic aneuploidy and a recurrent amplification of chromosome 1q

“…Significant difference was found in our research between monosomy and trisomy rate, suggesting that chromosome loss is more common. Prior studies highlighted chromosomes 12, 17, 20 and X as involved in most of the genomic aberrations 12,13 and both chromosomal gains and losses were frequently reported in cells from different sources. It is notable that, trisomy 12 is known to take over the culture in a few passages 15,34 but in our study, aneuploid cells carrying additional copy of chromosome 12 do not seem to be enriched in culture over time.…”

“…11 Karyotypic abnormalities of hESCs in long-term cultures have been reported before. [12][13][14][15] In hESCs, most of the alteration have been attributed to chromosomes 12 and 17, but chromosomes X and 20 were also repeatedly described. 12,16 G-banding technique is extremely laborious, requires dividing cells in culture and metaphases of sufficient quality for analysis, which have already proven difficulties to obtain.…”

“…[12][13][14][15] In hESCs, most of the alteration have been attributed to chromosomes 12 and 17, but chromosomes X and 20 were also repeatedly described. 12,16 G-banding technique is extremely laborious, requires dividing cells in culture and metaphases of sufficient quality for analysis, which have already proven difficulties to obtain. Moreover, conventional karyotype is not sensitive enough and may not be effective in evaluating genome integrity, as many of the intrachromosomal rearrangements and submicroscopic alterations in the genome can be missed due to the low resolution of the technique.…”

CIN and Aneuploidy: Different Concepts, Different Consequences

“…[1] For example 25% of non-cancer mouse cell lines are aneuploid [49] and RPE-1 cells (a human, non-cancer cell line which was initially euploid when harvested) often display clonal gain of chromosome 10q and 12. [18] Gains of chromosomes 12 and 17 have also been reported to be quite common in human pluripotent stem cells (hPSCs), [56] with gain of chromosome 12 in hPSCs to cause a growth benefit. [1] …”

Les cellules souches embryonnaires humaines révèlent l’existence d’une région hautement instable du génome

“…Dès 2004, plusieurs études ont démontré que les conditions de culture classiques des cellules ES humaines in vitro permettant le maintien de leur état indifférencié, induisaient de façon non négligeable une instabilité chromosomique. Des trisomies des chromosomes 12, 17 ou X ont ainsi été mises en évidence très fréquemment [2,3]. L'hypothèse qui prévaut actuellement pour expliquer ce phénomène est que l'amplification de certains gènes portés par ces chromosomes confère un avantage sélec-tif aux cellules souches indifférenciées.…”