Essentiality of CTNNB1 in Malignant Transformation of Human Embryonic Stem Cells under Long-Term Suboptimal Conditions.

Human embryonic stem cells (hESCs) gradually accumulate abnormal karyotypes during long-term suboptimal culture, which hinder their application in regenerative medicine. Previous studies demonstrated that the activation ofCTNNB1might be implicated in this process. Hence, the hESC line with stably silencedCTNNB1was established to further explore the role ofCTNNB1in the malignant transformation of hESCs. It was shown to play a vital role in the maintenance of the physiological properties of stem cells, such as proliferation, migration, differentiation, and telomere regulation. Furthermore, the malignant transformation of hESCs was induced by continuous exposure to 0.001 mu g/ml mitomycin C (MMC). The results showed thatCTNNB1and its target genes, including proto-oncogenesCCND1andC-MYC, were aberrantly upregulated in hESCs after MMC treatment. Moreover, the high expression ofCTNNB1accelerated cell transition from G0/G1 phase to the S phase and stimulated the growth of cells containing breakage-fusion-bridge (BFB) cycles. Conversely,CTNNB1silencing inhibited these effects and triggered a survival crisis. The current data indicated thatCTNNB1is intimately associated with the physiological properties of stem cells; however, the aberrant expression ofCTNNB1is involved in the malignant transformation of hESCs, which might advance the process by facilitating telomere-related unstable cell proliferation. Thus, the aberrant CTNNB1 level might serve as a potential biomarker for detecting the malignant transformation of hESCs.