Epigenetic Modifier SETD8 as a Therapeutic Target for High-Grade Serous Ovarian Cancer

Inhibition of protein arginine methyltransferase 6 activates interferon signaling and induces the apoptosis of endometrial cancer cells via histone modification

Histone modification, a major epigenetic mechanism regulating gene expression through chromatin remodeling, introduces dynamic changes in chromatin architecture. Protein arginine methyltransferase 6 (PRMT6) is overexpressed in various types of cancer, including prostate, lung and endometrial cancer (EC). Epigenome regulates the expression of endogenous retrovirus (ERV), which activates interferon signaling related to cancer. The antitumor effects of PRMT6 inhibition and the role of PRMT6 in EC were investigated, using epigenome multi‑omics analysis, including an assay for chromatin immunoprecipitation sequencing (ChIP‑seq) and RNA sequencing (RNA‑seq). The expression of PRMT6 in EC was analyzed using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and immunohistochemistry (IHC). The prognostic impact of PRMT6 expression was evaluated using IHC. The effects of PRMT6‑knockdown (KD) were investigated using cell viability and apoptosis assays, as well as its effects on the epigenome, using ChIP‑seq of H3K27ac antibodies and RNA‑seq. Finally, the downstream targets identified by multi‑omics analysis were evaluated. PRMT6 was overexpressed in EC and associated with a poor prognosis. PRMT6‑KD induced histone hypomethylation, while suppressing cell growth and apoptosis. ChIP‑seq revealed that PRMT6 regulated genomic regions related to interferons and apoptosis through histone modifications. The RNA‑seq data demonstrated altered interferon‑related pathways and increased expression of tumor suppressor genes, including NK6 homeobox 1 and phosphoinositide‑3‑kinase regulatory subunit 1, following PRMT6‑KD. RT‑qPCR revealed that eight ERV genes which activated interferon signaling were upregulated by PRMT6‑KD. The data of the present study suggested that PRMT6 inhibition induced apoptosis through interferon signaling activated by ERV. PRMT6 regulated tumor suppressor genes and may be a novel therapeutic target, to the best of our knowledge, in EC.

Functional Proteomics Characterization of the Role of SPRYD7 in Colorectal Cancer Progression and Metastasis

SPRY domain-containing protein 7 (SPRYD7) is a barely known protein identified via spatial proteomics as being upregulated in highly metastatic-to-liver KM12SM colorectal cancer (CRC) cells in comparison to its isogenic poorly metastatic KM12C CRC cells. Here, we aimed to analyze SPRYD7's role in CRC via functional proteomics. Through immunohistochemistry, the overexpression of SPRYD7 was observed to be associated with the poor survival of CRC patients and with an aggressive and metastatic phenotype. Stable SPRYD7 overexpression was performed in KM12C and SW480 poorly metastatic CRC cells and in their isogenic highly metastatic-to-liver-KM12SM-and-to-lymph-nodes SW620 CRC cells, respectively. Upon upregulation of SPRYD7, in vitro and in vivo functional assays confirmed a key role of SPRYD7 in the invasion and migration of CRC cells and in liver homing and tumor growth. Additionally, transient siRNA SPRYD7 silencing allowed us to confirm in vitro functional results. Furthermore, SPRYD7 was observed as an inductor of angiogenesis. In addition, the dysregulated SPRYD7-associated proteome and SPRYD7 interactors were elucidated via 10-plex TMT quantitative proteins, immunoproteomics, and bioinformatics. After WB validation, the biological pathways associated with the stable overexpression of SPRYD7 were visualized. In conclusion, it was demonstrated here that SPRYD7 is a novel protein associated with CRC progression and metastasis. Thus, SPRYD7 and its interactors might be of relevance in identifying novel therapeutic targets for advanced CRC.

Targeted inhibition of the methyltransferase SETD8 synergizes with the Wee1 inhibitor adavosertib in restraining glioblastoma growth

Despite intense research efforts, glioblastoma remains an incurable brain tumor with a dismal median survival time of 15 months. Thus, identifying new therapeutic targets is an urgent need. Here, we show that the lysine methyltransferase SETD8 is overexpressed in 50% of high-grade gliomas. The small molecule SETD8 inhibitor UNC0379, as well as siRNA-mediated inhibition of SETD8, blocked glioblastoma cell proliferation, by inducing DNA damage and activating cell cycle checkpoints. Specifically, in p53-proficient glioblastoma cells, SETD8 inhibition and DNA damage induced p21 accumulation and G1/S arrest whereas, in p53-deficient glioblastoma cells, DNA damage induced by SETD8 inhibition resulted in G2/M arrest mediated by Chk1 activation. Checkpoint abrogation, by the Wee1 kinase inhibitor adavosertib, induced glioblastoma cell lines and primary cells, DNA-damaged by UNC0379, to progress to mitosis where they died by mitotic catastrophe. Finally, UNC0379 and adavosertib synergized in restraining glioblastoma growth in a murine xenograft model, providing a strong rationale to further explore this novel pharmacological approach for adjuvant glioblastoma treatment.

SETD8 promotes glycolysis in colorectal cancer via regulating HIF1α/HK2 axis

Glycolysis is one of the factors influencing cancer cell growth and metastasis. Here, we aimed to investigate the role of SETD8 gene, which is a pro-oncogene. Using bioinformatics tools including Ualcan, Timer, GEPIA, and PrognoScan to study the expression of SETD8 in colorectal cancer, we found that SETD8 expression was higher in colon cancer tissues than that in normal tissues. Higher levels of SETD8 predicted poorer survival of patients. This piqued our interest, so we transfected SETD8 knockdown and overexpression plasmids into colorectal cancer cells and found that SETD8 overexpression enhanced proliferation and glycolysis in colon cancer cells, while SETD8 knockdown decreased cell proliferation and glycolysis. Mechanistically, we examined the expression of HIF1α and HK2 protein by western-blot assay and found that SETD8 activated the HIF1α/HK2 pathway. Then, we treated SETD8-overexpressed cells with HIF1α inhibitor and found that the pro-tumor growth and glycolytic effects of SETD8 were reversed, indicating that SETD8 promoted the growths of colorectal cancer cells by upregulating the HIF1α /HK2 pathway.

Novel insights into histone lysine methyltransferases in cancer therapy: From epigenetic regulation to selective drugs

The reversible and precise temporal and spatial regulation of histone lysine methyltransferases (KMTs) is essential for epigenome homeostasis. The dysregulation of KMTs is associated with tumor initiation, metastasis, chemoresistance, invasiveness, and the immune microenvironment. Therapeutically, their promising effects are being evaluated in diversified preclinical and clinical trials, demonstrating encouraging outcomes in multiple malignancies. In this review, we have updated recent understandings of KMTs' functions and the development of their targeted inhibitors. First, we provide an updated overview of the regulatory roles of several KMT activities in oncogenesis, tumor suppression, and immune regulation. In addition, we summarize the current targeting strategies in different cancer types and multiple ongoing clinical trials of combination therapies with KMT inhibitors. In summary, we endeavor to depict the regulation of KMT-mediated epigenetic landscape and provide potential epigenetic targets in the treatment of cancers.

The Histone Methyltransferase SETD8 Regulates the Expression of Tumor Suppressor Genes via H4K20 Methylation and the p53 Signaling Pathway in Endometrial Cancer Cells

The histone methyltransferase SET domain-containing protein 8 (SETD8), which methylates histone H4 lysine 20 (H4K20) and non-histone proteins such as p53, plays key roles in human carcinogenesis. Our aim was to determine the involvement of SETD8 in endometrial cancer and its therapeutic potential and identify the downstream genes regulated by SETD8 via H4K20 methylation and the p53 signaling pathway. We examined the expression profile of SETD8 and evaluated whether SETD8 plays a critical role in the proliferation of endometrial cancer cells using small interfering RNAs (siRNAs). We identified the prognostically important genes regulated by SETD8 via H4K20 methylation and p53 signaling using chromatin immunoprecipitation sequencing, RNA sequencing, and machine learning. We confirmed that SETD8 expression was elevated in endometrial cancer tissues. Our in vitro results suggest that the suppression of SETD8 using siRNA or a selective inhibitor attenuated cell proliferation and promoted the apoptosis of endometrial cancer cells. In these cells, SETD8 regulates genes via H4K20 methylation and the p53 signaling pathway. We also identified the prognostically important genes related to apoptosis, such as those encoding KIAA1324 and TP73, in endometrial cancer. SETD8 is an important gene for carcinogenesis and progression of endometrial cancer via H4K20 methylation.

KMT5A-methylated SNIP1 promotes triple-negative breast cancer metastasis by activating YAP signaling

Smad nuclear-interacting protein 1 (SNIP1) is a transcription repressor related to the TGF-β signaling pathway and associates with c-MYC, a key regulator of cell proliferation and tumor development. Currently, the mechanism by which SNIP1 regulates tumorigenesis and cancer metastasis is unknown. Here, we identify that SNIP1 is a non-histone substrate of lysine methyltransferase KMT5A, which undergoes KMT5A-mediated mono-methylation to promote breast cancer cell growth, invasion and lung metastasis. Mechanistically, we show KMT5A-mediated K301 methylation of SNIP1 represents a sensing signal to release histone acetyltransferase KAT2A and promotes the interaction of c-MYC and KAT2A, and the recruitment of c-MYC/KAT2A complex to promoter of c-MYC targets. This event ultimately inhibits the Hippo kinase cascade to enhance triple-negative breast cancer (TNBC) metastasis by transcriptionally activating MARK4. Co-inhibition of KMT5A catalytic activity and YAP in TNBC xenograft-bearing animals attenuates breast cancer metastasis and increases survival. Collectively, this study presents an KMT5A methylation-dependent regulatory mechanism governing oncogenic function of SNIP1.

SNIP1 methylation initiates its oncogenic functions. Here, the authors show that SNIP1 is methylated by KMT5A and this leads to downstream signalling that activates the YAP pathway, resulting in tumorigenesis and metastasis.

Abnormal 5-methylcytosine lncRNA methylome is involved in human high-grade serous ovarian cancer

Methylcytosine (m5C) is an important posttranscriptional RNA methylation modification. Studies have reported that aberrant RNA methylation can regulate tumorigenesis and development, indicating the importance of exploring the distribution and biological functions of m5C modification in human high-grade serous ovarian cancer (HGSOC) lncRNAs. In the current study, we identified 2,050 dysregulated m5C peaks, 1,767 of which were significantly upregulated, while 283 were significantly downregulated by performing methylated RNA immunoprecipitation sequencing on 3 pairs of human HGSOC tissues and paired normal tissues. GO enrichment analysis showed that genes altered by the m5C peak played a key role in phylogeny, protein metabolism, and gene mismatch repair. KEGG pathway analysis revealed that these genes were enriched in some important pathways in cancer regulation, such as the PI3K-Akt signalling pathway, transcriptional dysregulation in cancer, and mismatch repair pathways. In addition, through joint analysis of MeRIP-seq and RNA-seq data, we identified 1671 differentially methylated m5C peaks and synchronous differentially expressed genes. These genes play a key role in cell growth or maintenance, RNA metabolism and material transport. We analyzed expression of the m5C modification regulatory gene collagen type IV alpha 3 chain (COL4A3) in 80 HGSOC tissue samples by immunohistochemistry and found that high expression of COL4A3 was significantly correlated with CA125 level (P=0.016), lymph node metastasis (P<0.001), degree of interstitial invasion (P<0.001) and FIGO staging (P<0.001) and indicated a poorer prognosis. Our results revealed the critical role of m5C methylation of lncRNAs in HGSOC, and provided a reference for the prognostic stratification and treatment strategy of HGSOC.

Post-Translational Modifications of PCNA in Control of DNA Synthesis and DNA Damage Tolerance-the Implications in Carcinogenesis

The faithful DNA replication is a critical event for cell survival and inheritance. However, exogenous or endogenous sources of damage challenge the accurate synthesis of DNA, which causes DNA lesions. The DNA lesions are obstacles for replication fork progression. However, the prolonged replication fork stalling leads to replication fork collapse, which may cause DNA double-strand breaks (DSB). In order to maintain genomic stability, eukaryotic cells evolve translesion synthesis (TLS) and template switching (TS) to resolve the replication stalling. Proliferating cell nuclear antigen (PCNA) trimer acts as a slide clamp and encircles DNA to orchestrate DNA synthesis and DNA damage tolerance (DDT). The post-translational modifications (PTMs) of PCNA regulate these functions to ensure the appropriate initiation and termination of replication and DDT. The aberrant regulation of PCNA PTMs will result in DSB, which causes mutagenesis and poor response to chemotherapy. Here, we review the roles of the PCNA PTMs in DNA duplication and DDT. We propose that clarifying the regulation of PCNA PTMs may provide insights into understanding the development of cancers.

Histone lysine methyltransferase SET8 is a novel therapeutic target for cancer treatment

SET8 is the only lysine methyltransferase that can specifically monomethylate the histone H4K20. SET8-mediated protein modifications are largely involved in the regulation of cell cycle, DNA repair, gene transcription, cell apoptosis, and other vital physiological processes. The aberrant expression of SET8 is closely linked to the proliferation, invasion, metastasis, and prognosis of a variety of cancers. As a consequence, targeting SET8 could be an appealing strategy for cancer therapy. In this article, we introduce the molecular structure of SET8, followed by summarizing its roles in various biological pathways. Crucially, we highlight the potential functions of SET8 in tumors, as well as progress in the development of SET inhibitors for cancer treatment.

Integrated Analysis of Whole Genome and Epigenome Data Using Machine Learning Technology: Toward the Establishment of Precision Oncology

With the completion of the International Human Genome Project, we have entered what is known as the post-genome era, and efforts to apply genomic information to medicine have become more active. In particular, with the announcement of the Precision Medicine Initiative by U.S. President Barack Obama in his State of the Union address at the beginning of 2015, "precision medicine," which aims to divide patients and potential patients into subgroups with respect to disease susceptibility, has become the focus of worldwide attention. The field of oncology is also actively adopting the precision oncology approach, which is based on molecular profiling, such as genomic information, to select the appropriate treatment. However, the current precision oncology is dominated by a method called targeted-gene panel (TGP), which uses next-generation sequencing (NGS) to analyze a limited number of specific cancer-related genes and suggest optimal treatments, but this method causes the problem that the number of patients who benefit from it is limited. In order to steadily develop precision oncology, it is necessary to integrate and analyze more detailed omics data, such as whole genome data and epigenome data. On the other hand, with the advancement of analysis technologies such as NGS, the amount of data obtained by omics analysis has become enormous, and artificial intelligence (AI) technologies, mainly machine learning (ML) technologies, are being actively used to make more efficient and accurate predictions. In this review, we will focus on whole genome sequencing (WGS) analysis and epigenome analysis, introduce the latest results of omics analysis using ML technologies for the development of precision oncology, and discuss the future prospects.