Epigenetic priming by EHMT1/EHMT2 in acute lymphoblastic leukemia induces TP53 and TP73 overexpression and promotes cell death

GLP and G9a histone methyltransferases as potential therapeutic targets for lymphoid neoplasms

Histone methyltransferases (HMTs) are enzymes that regulate histone methylation and play an important role in controlling transcription by altering the chromatin structure. Aberrant activation of HMTs has been widely reported in certain types of neoplastic cells. Among them, G9a/EHMT2 and GLP/EHMT1 are crucial for H3K9 methylation, and their dysregulation has been associated with tumor initiation and progression in different types of cancer. More recently, it has been shown that G9a and GLP appear to play a critical role in several lymphoid hematologic malignancies. Importantly, the key roles played by both enzymes in various diseases made them attractive targets for drug development. In fact, in recent years, several groups have tried to develop small molecule inhibitors targeting their epigenetic activities as potential anticancer therapeutic tools. In this review, we discuss the physiological role of GLP and G9a, their oncogenic functions in hematologic malignancies of the lymphoid lineage, and the therapeutic potential of epigenetic drugs targeting G9a/GLP for cancer treatment.

Molecular and functional anticancer effects of GLP/G9a inhibition by UNC0646 in MeWo melanoma cells

In recent years, histone methyltransferases (HMTs) have emerged as important therapeutic targets in cancer due to their oncogenic role. Herein, we used the GLP/G9a inhibitor UNC0646 to assess whether the inhibition of such HMTs could induce cell death in MeWo melanoma cells. Furthermore, we investigated the cellular and molecular mechanisms involved in the observed cell death events. Finally, we performed a functional genomics analysis of 480 melanoma samples to characterize G9a/GLP involvement in melanoma. Interestingly, after UNC0646 treatment, MeWo cells underwent apoptosis, followed by loss of mitochondrial membrane potential and the generation of reactive oxygen species (ROS). Furthermore, MeWo cells treated with UNC0646 showed cell cycle arrest and inhibition of proliferation. At the molecular level, UNC0646 treatment increased the transcriptional levels of CDK1 and BAX, and decreased BCL-2 mRNA levels. Finally, we performed a functional enrichment analysis, which demonstrated that dozens of biological pathways were enriched in melanoma samples according to GLP and G9a expression, including apoptosis and necrosis. Taken together, our data show that inhibition of GLP/G9a using UNC0646 exerts anticancer effects on melanoma cells by controlling their proliferation and inducing apoptosis.

How CBX proteins regulate normal and leukemic blood cells

Hematopoietic stem cell (HSC) fate decisions are dictated by epigenetic landscapes. The Polycomb Repressive Complex 1 (PRC1) represses genes that induce differentiation, thereby maintaining HSC self-renewal. Depending on which chromobox (CBX) protein (CBX2, CBX4, CBX6, CBX7, or CBX8) is part of the PRC1 complex, HSC fate decisions differ. Here, we review how this occurs. We describe how CBX proteins dictate age-related changes in HSCs and stimulate oncogenic HSC fate decisions, either as canonical PRC1 members or by alternative interactions, including non-epigenetic regulation. CBX2, CBX7, and CBX8 enhance leukemia progression. To target, reprogram, and kill leukemic cells, we suggest and describe multiple therapeutic strategies to interfere with the epigenetic functions of oncogenic CBX proteins. Future studies should clarify to what extent the non-epigenetic function of cytoplasmic CBX proteins is important for normal, aged, and leukemic blood cells.

Drivers of de novo Serine/Glycine synthesis in acute leukemia

Cancer cells hijack metabolic pathways in order to provide themselves with building blocks to support their proliferation and survival. Upregulation and addiction to de novo serine/glycine synthesis is an example of metabolic rewiring in cancer cells whereby serine and glycine are synthesised via a side branch of glycolysis. In this review, we focus on upregulation of endogenous serine/glycine production in acute leukemia, namely T-cell acute leukemia (T-ALL) and acute myeloid leukemia (AML). Several genetic lesions directly driving the serine/glycine addiction in acute leukemia have been established. Additionally, indirect regulation of de novo serine/glycine synthesis is observed in acute leukemia.

Integrated analysis and identification of nine-gene signature associated to oral squamous cell carcinoma pathogenesis

Oral squamous cell carcinoma (OSCC) is one of the leading cancers with poor disease survival rate. Herein, we explored molecular basis, in silico identification and in vitro verification of genes associated with OSCC. Five gene expression series including, GSE30784, GSE13601, GSE9844, GSE23558 and GSE37991 were screened for differentially expressed genes (DEGs). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were enriched by cluster Profiler. Further, protein-protein interaction network was analysed and hub genes were verified. A total of 6476 (up-regulated: 2848; down-regulated: 3628) DEGs were identified among OSCC patients and healthy controls. Gene Ontology analysis indicated DEGs enrichment in cellular motility, invasion and adhesion processes. KEGG analysis revealed enrichment of PI3K-Akt signalling, focal adhesion and regulation of actin cytoskeleton pathways. Subsequently, nine DEGs including APP, EHMT1, ACACB, PCNA, PLAU, FST, HMGA2, LAMC2 and SPP1 were correlated with TCGA expression data along with significant association towards patient's survival, recognized as hub genes. This dysregulated mRNA signature of genes was validated in two OSCC cell lines with an anti-cancer agent, fisetin. Fisetin inhibited the expression of APP, EHMT1, PCNA, PLAU, FST, HMGA2, LAMC2, SPP1 and upregulated the expression of ACACB gene which were associated with growth inhibition of both the OSCC cell lines. The regulatory effect of fisetin supported crucial role of nine hub genes identified in OSCC. This study signified that hub genes and pathways might influence the aggressiveness of OSCC. Thus, the proposed hub genes could be potential diagnostic biomarker and drug targets for OSCC.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02737-4.