Human endogenous retrovirus K (HML-2) RNA and protein expression is a marker for human embryonic and induced pluripotent stem cells

Background Malignant human embryonal carcinoma cells (ECCs) rely on similar transcriptional networks as non-malignant embryonic stem cells (ESCs) to control selfrenewal, maintain pluripotency, and inhibit differentiation. Because re-activation of silenced HERV-K(HML-2) loci is a hallmark of ECCs, we asked if this HERV group was also reactivated in ESCs and induced pluripotent stem cells (iPSCs).