Targeting LSD1 in tumor immunotherapy: rationale, challenges and potential

Novel pharmacologic inhibition of lysine-specific demethylase 1 as a potential therapeutic for glioblastoma

Lysine-specific demethylase 1 (LSD1/KDM1A) is a pivotal epigenetic enzyme that contributes to several malignancies including malignant glioma. LSD1 is a flavin adenine dinucleotide dependent histone demethylase that specifically targets histone H3 lysine (K) 4 mono- (me1) and di-methylation (me2) and H3K9me1/2 for demethylation. Herein we report the development of an LSD inhibitor, S2172, which efficiently penetrates the blood-brain barrier. S2172 effectively suppresses LSD1 enzymatic activity, resulting in the depletion of cell growth both in vitro in glioma stem cells (GSCs) (mean half-maximal inhibitory concentration (IC50) of 13.8 μM) and in vivo in a GSC orthotopic xenograft mouse model. Treatment with S2172 robustly reduced the expression of the stemness-related genes MYC and Nestin in GSC cells. Consistent with this, chromatin immunoprecipitation-sequencing revealed a significant S2172-dependent alteration in H3K4me2/H3K4me3 status. Furthermore, we identified 284 newly acquired H3K4me2 peak regions after S2172 treatment, which were encompassed within super-enhancer regions. The altered H3K4me2/H3K4me3 status induced by S2172 treatment affected the expression of genes related to tumorigenesis. Our data suggest that targeting LSD1 with S2172 could provide a promising treatment option for glioblastomas, particularly due to targeting of GSC populations.

The Roles of H3K9me3 Writers, Readers, and Erasers in Cancer Immunotherapy

The interplay between cancer and the immune system has captivated researchers for a long time. Recent developments in cancer immunotherapy have substantiated this interest with a significant benefit to cancer patients. Tumor and immune cells are regulated via a wide range of molecular mechanisms involving intricate transcriptional and epigenetic networks. Epigenetic processes influence chromatin structure and accessibility, thus governing gene expression, replication, and DNA damage repair. However, aberrations within epigenetic signatures are frequently observed in cancer. One of the key epigenetic marks is the trimethylation of histone 3 at lysine 9 (H3K9me3), confined mainly within constitutive heterochromatin to suppress DNA accessibility. It is deposited at repetitive elements, centromeric and telomeric loci, as well as at the promoters of various genes. Dysregulated H3K9me3 deposition disrupts multiple pathways, including immune signaling. Consequently, altered H3K9me3 dynamics may modify the efficacy of immunotherapy. Indeed, growing evidence highlights the pivotal roles of various proteins mediating H3K9me3 deposition (SETDB1/2, SUV39H1/2), erasure (KDM3, KDM4 families, KDM7B, LSD1) and interpretation (HP1 proteins, KAP1, CHD4, CDYL, UHRF1) in modulating immunotherapy effectiveness. Here, we review the existing literature to synthesize the available information on the influence of these H3K9me3 writers, erasers, and readers on the response to immunotherapy.

Research progress of LSD1-based dual-target agents for cancer therapy

Lysine-specific demethylase 1 (LSD1) is a histone lysine demethylase that is significantly overexpressed or dysregulated in different cancers and plays important roles in cell growth, invasion, migration, immune escape, angiogenesis, gene regulation, and transcription. Therefore, it is a superb target for the discovery of novel antitumor agents. However, because of their innate and acquired resistance and low selectivity, LSD1 inhibitors are associated with limited therapeutic efficacy and high toxicity. Furthermore, LSD1 inhibitors synergistically improve the efficacy of additional antitumor drugs, which encourages numerous medicinal chemists to innovate and develop new-generation LSD1-based dual-target agents. This review discusses the theoretical foundation of the design of LSD1-based dual-target agents and summarizes their possible applications in treating cancers.