Tumor progression of culture‐adapted human embryonic stem cells during long‐term culture

Abstract

Human embryonic stem cells (hESCs) during long-term culture acquire chromosomal changes similar to those occurring in tumorigenesis. This was raised concerns about the progression from hESCs to malignant cells. This study aimed to investigate the changes in chromosomes, cell phenotype, and genes in culture-adapted hESCs to ascertain whether tumorigenic transformation occurred. By cytogenetic analysis we found progressive karyotypic changes from simple to complex in chHES-3, one of the hESC lines established in our laboratory, during a long-term suboptimal culture. We further compared chHES-3 cells at different karyotypic stages in cell surface markers, in vivo differentiation, cell cycle, apoptosis, and gene expression profiles. We found that the karyotypically aberrant chHES-3 had higher S-phase fraction in cell cycle distributions and antiapoptosis ability. In vivo differentiation of karyotypically normal chHES-3 resulted in relatively mature teratoma, whereas karyotypically aberrant chHES-3 formed immature teratoma (grade III), in which more primary neural epithelium was revealed by pathological analysis. The microarray analysis and real-time PCR results showed that some oncogenes were upregulated in karyotypically aberrant chHES-3 cells, whereas the genes related to differentiation were downregulated, and that Wnt signal pathway was activated. In conclusion, chHES-3 cells underwent deregulation of self-renewal and dysfunction of related genes in long-term culture adaptation, leading to malignant transformation.

Telomerase-mediated telomere elongation from human blastocysts to embryonic stem cells

“…The mean telomere length was 12.0261.01 kb and did not follow Gaussian distribution, with telomere lengths of 9.8-14.4 kb between the 2.5th and 97.5th percentiles (supplementary material Table S2). We noted that the chHES-3 line, which has an unstable genomic state and acquires progressive chromosomal abnormalities during in vitro culture (Yang et al, 2008;Yang et al, 2010), had significantly shorter telomeres (P,0.05) up to passage P60 (Fig. 7B).…”

Genomic Instability in Pluripotent Stem Cells: Implications for Clinical Applications

“…Also, hESC-like gene expression signatures have been found in some aggressive human tumors (47). Interestingly, there are few studies that directly show that genomically aberrant hPSCs actually cause tumors; however, there is a report that use of a karyotypically abnormal line in a teratoma assay caused immature teratoma formation, whereas injection of the karyotypically normal parental line caused only benign teratomas (48). This suggests that, in certain circumstances, genomic aberrations may alter the tumorigenic potential of hPSCs.…”

CIN and Aneuploidy: Different Concepts, Different Consequences

“…[1,42,53] Culture conditions have been shown to lead to low levels of aneuploidy, [54,55] and these low levels of aneuploidy can lead to the expansion of a clone with an advantageous karyotype. [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.…”