LSD1-mediated demethylation of OCT4 safeguards pluripotent stem cells by maintaining the transcription of PORE-motif-containing genes

Targeting Cancer Stem Cells through Epigenetic Modulation of Interferon Response

Cancer stem cells (CSCs) are a small subset of cancer cells and are thought to play a critical role in the initiation and maintenance of tumor mass. CSCs exhibit similar hallmarks to normal stem cells, such as self-renewal, differentiation, and homeostasis. In addition, CSCs are equipped with several features so as to evade anticancer mechanisms. Therefore, it is hard to eliminate CSCs by conventional anticancer therapeutics that are effective at clearing bulk cancer cells. Interferons are innate cytokines and are the key players in immune surveillance to respond to invaded pathogens. Interferons are also crucial for adaptive immunity for the killing of specific aliens including cancer cells. However, CSCs usually evolve to escape from interferon-mediated immune surveillance and to shape the niche as a “cold” tumor microenvironment (TME). These CSC characteristics are related to their unique epigenetic regulations that are different from those of normal and bulk cancer cells. In this review, we introduce the roles of epigenetic modifiers, focusing on LSD1, BMI1, G9a, and SETDB1, in contributing to CSC characteristics and discussing the interplay between CSCs and interferon response. We also discuss the emerging strategy for eradicating CSCs by targeting these epigenetic modifiers, which can elevate cytosolic nuclei acids, trigger interferon response, and reshape a “hot” TME for improving cancer immunotherapy. The key epigenetic and immune genes involved in this crosstalk can be used as biomarkers for precision oncology.

DNA repair proteins cooperate with SOX2 in regulating the transition of human embryonic stem cells to neural progenitor cells

SOX2, a well-established pluripotency factor supporting the self-renewal of pluripotent stem cells (PSCs), is also a crucial factor for maintaining the properties and functionalities of neural progenitor cells (NPCs). It regulates the transcription of target genes by forming complexes with its partner factors, but systematic comparison of SOX2 binding partners in human PSCs versus NPCs is lacking. Here, by deciphering and comparing the SOX2-protein interactomes in human embryonic stem cells (hESCs) versus the NPCs derived from them, we identified 23 proteins with high reproducibility that are most differentially associated with SOX2, of which 9 are DNA repair proteins (PARP1, PARP2, PRKDC, XRCC1, XRCC5, XRCC6, RPA1, LIG3, DDB1). Genetic knocking-down or pharmacological inhibiting two of the DNA repair proteins (PARP1 and PRKDC) significantly up-regulated certain NPC or ectodermal biomarkers that are transcriptionally-suppressed by the SOX2/DNA repair protein complexes. These findings point to a crucial role of DNA repair proteins in pluripotent state transition and neural induction.

LSD1: Expanding Functions in Stem Cells and Differentiation

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSC) provide a powerful model system to uncover fundamental mechanisms that control cellular identity during mammalian development. Histone methylation governs gene expression programs that play a key role in the regulation of the balance between self-renewal and differentiation of ESCs. Lysine-specific demethylase 1 (LSD1, also known as KDM1A), the first identified histone lysine demethylase, demethylates H3K4me1/2 and H3K9me1/2 at target loci in a context-dependent manner. Moreover, it has also been shown to demethylate non-histone substrates playing a central role in the regulation of numerous cellular processes. In this review, we summarize current knowledge about LSD1 and the molecular mechanism by which LSD1 influences the stem cells state, including the regulatory circuitry underlying self-renewal and pluripotency.