Characterization of human embryonic stem cells with features of neoplastic progression

Cultured human embryonic stem (hES) cells can acquire genetic and epigenetic changes that make them vulnerable to transformation. As hES cells with cancer-cell characteristics share properties with normal hES cells, such as self-renewal, teratoma formation and the expression of pluripotency markers, they may be misconstrued as superior hES cells with enhanced ‘stemness’. We characterize two variant hES cell lines (v-hESC-1 and v-hESC-2) that express pluripotency markers at high levels and do not harbor chromosomal abnormalities by standard cytogenetic measures. We show that the two lines possess some features of neoplastic progression, including a high proliferative capacity, growth-factor independence, a 9- to 20-fold increase in frequency of tumor initiating cells, niche independence and aberrant lineage specification, although they are not malignant. Array comparative genomic hybridization revealed an amplification at 20q11.1-11.2 in v-hESC-1 and a deletion at 5q34a-5q34b;5q3 and a mosaic gain of chromosome 12 in v-hESC-2. These results emphasize the need for functional characterization to distinguish partially transformed and normal hES cells. Custom oligonucleotide array gene expression analysis was performed on total RNA from low passage normal and variant human embryonic stem cell (hESC) lines, all cultured in our laboratory under the same conditions. Furthermore, array-based comparative genomic hybridization was also performed on the normal and variant hESC lines. v-hESC-1 and v-hESC-2 represent two independent lines that display neoplastic characteristics with distinctive copy number alterations. v-hESC-1_A2B5 represents neural precursor cultures differentiated from variant hES cells. GSM349016-GSM349022: Gene expression analysis GSM351500-GSM351511: aCGH analysis