Identification of BMI1 Promoter Inhibitors from Beaumontia murtonii and Eugenia operculata

3-Hydroxy-3-(2-oxopropyl)indolin-2-one, a product of a human-derived Enterocloster strain, is an inhibitor of nitric oxide production

When cultured anaerobically, Enterocloster sp. RD014215 was found to produce 1. Using nuclear magnetic resonance and mass spectroscopy, the planar structure of 1 was determined to be 3-hydroxy-3-(2-oxopropyl)indolin-2-one. The chirality of 1 was implied as S by comparing the optical rotation value of 1 with literature reports of the synthesized compounds. To our knowledge, this work represents the first discovery of the metabolite produced by Enterocloster strain. 1 exhibited inhibition of nitric oxide (NO) production, demonstrating a 50% inhibitory activity (IC50) of 34 µm for NO production by murine macrophage cells subjected to lipopolysaccharide stimulation.

Roles of BMI1 in the Initiation, Progression, and Treatment of Hepatocellular Carcinoma

Liver cancer has high rates of morbidity and mortality, and its treatment is a global health challenge. Hepatocellular carcinoma (HCC) accounts for 90% of all primary liver cancer cases. B-lymphoma Mo-MLV insertion region 1 (BMI1) has been identified as a proto-oncogene, which contributes to the initiation and progression of many malignant tumors. BMI1 expression is upregulated in HCC, and it influences the occurrence and development of HCC by various mechanisms, such as the INK4a/ARF locus, NF-κB signaling pathway, and PTEN/PI3K/AKT signaling pathway. In addition, the expression of BMI1 is related to prognosis and recurrence of HCC. Hence, there is clear evidence that BMI1 is a novel and valid therapeutic target for HCC. Accordingly, the development of therapeutic strategies targeting BMI1 has been a focus of recent research, providing new directions for HCC treatment. This review summarizes the role of BMI1 in the occurrence and treatment of HCC, which will provide a basis for using BMI1 as a potential target for the development of therapeutic strategies for HCC.

Natural Compounds with BMI1 Promoter Inhibitory Activity from Mammea siamensis and Andrographis paniculata

A new coumarin derivative (1) and 30 known compounds were isolated from Mammea siamensis and Andrographis paniculata, guided by B cell-specific Moloney murine leukemia virus insertion region 1 (BMI1) promoter inhibitory activity. Among the isolated compounds, 15 compounds showed BMI1 promoter inhibitory activity, and five compounds were found to be cytotoxic. 14-Deoxy-11,12-dehydroandrographolide (18) was highly cytotoxic to DU145 cells with an IC50 value of 25.4 µM. Western blotting analysis of compound 18 in DU145 cells suggested that compound 18 suppresses BMI1 expression.

Screening study of cancer-related cellular signals from microbial natural products

To identify bioactive natural products from various natural resources, such as plants and microorganisms, we investigated programs to screen for compounds that affect several cancer-related cellular signaling pathways, such as BMI1, TRAIL, and Wnt. This review summarizes the results of our recent studies, particularly those involving natural products isolated from microbial resources, such as actinomycetes, obtained from soil samples collected primarily around Chiba, Japan.

The Role of Polycomb Group Protein BMI1 in DNA Repair and Genomic Stability

The polycomb group (PcG) proteins are a class of transcriptional repressors that mediate gene silencing through histone post-translational modifications. They are involved in the maintenance of stem cell self-renewal and proliferation, processes that are often dysregulated in cancer. Apart from their canonical functions in epigenetic gene silencing, several studies have uncovered a function for PcG proteins in DNA damage signaling and repair. In particular, members of the poly-comb group complexes (PRC) 1 and 2 have been shown to recruit to sites of DNA damage and mediate DNA double-strand break repair. Here, we review current understanding of the PRCs and their roles in cancer development. We then focus on the PRC1 member BMI1, discussing the current state of knowledge of its role in DNA repair and genome integrity, and outline how it can be targeted pharmacologically.

Nonactic Acid Derivatives Isolated From Streptomyces werraensis IFM12104 in a Screening Program for BMI1 Promoter Inhibitory Activity

Upon screening for compounds with B cell-specific Moloney murine leukemia virus region 1 (BMI1) promoter inhibitory activity, 3 nonactic acid derivatives (1-3) were isolated from Streptomyces werraensis IFM12104. Although spectral data of compound 1 were identical with those reported in literature for 4α-(3, 5-dihydroxy-heptyl)-3α-methyl-2-oxetanone (4), compound 1 was revealed to be homononactic acid by X-ray analysis. Compounds 2 and 3 were identified as bishomononactic acid and nonactic acid using spectral data. The 3 compounds 1 to 3 inhibited BMI1 promoter activities with IC50 values of 240, 160, and 180 μM, respectively.

Identification of BMI1 promoter inhibitors from Streptomyces sp. IFM-11958

B-cell-specific Moloney murine leukemia virus region 1 (BMI1) is a central component of polycomb repressive complex 1 (PRC1), which maintains epigenetic repression of genes expression via chromatin condensation. BMI1 overexpression downregulates the expression of tumor suppressor genes, such as p16Ink4a and PTEN. BMI1 expression is upregulated in cancer stem cells (CSCs). Therefore, inhibitors of BMI1 expression have potential as therapeutic agents for cancer. This study aimed to identify BMI1 promoter inhibitors from actinomycetes. Using a recently constructed BMI1 promoter assay, we isolated three known compounds, elaiophylin (1), 2-methylelaiophylin (2), and nocardamin (3), from Streptomyces sp. IFM-11958 that inhibited BMI1 promoter activity with IC₅₀ values of 30 nM, 447 nM, 22 µM, respectively. Elaiophylin (1) was the most potent. Western blot and PCR analyses revealed that elaiophylin (1) inhibited BMI1 expression at the mRNA level in human prostate cancer cells (DU145). Elaiophylin (1) also inhibited the sphere-forming activity of human hepatocellular carcinoma cells (Huh7), indicating that elaiophylin (1) suppresses the self-renewal capacity of CSCs. Elaiophylin (1) is the first BMI1 promoter inhibitor isolated from actinomycete metabolites.

GLI1 Inhibitors Identified by Target Protein Oriented Natural Products Isolation (TPO-NAPI) with Hedgehog Inhibition

This report describes the development of a target-protein-oriented natural-products-isolation (TPO-NAPI) method for Hedgehog inhibitors and the direct GLI1 inhibitor, 5'- O-methyl-3-hydroxyflemingin A (3), which inhibited hedgehog (Hh) signal transduction and diminished characteristics of cancer stem cells. Eight natural products (including three newly described products) that directly bind to GLI1 were rapidly obtained via the TPO-NAPI method developed using GLI1 protein-immobilized beads. 5'- O-Methyl-3-hydroxyflemingin A (3) inhibited Hh signaling (IC₅₀ 7.3 μM), leading to decreasing production of the Hh target proteins BCL2, PTCH1, and BMI1. 5'- O-Methyl-3-hydroxyflemingin A (3) was cytotoxic to Hh-related cancer cells. CD experiments revealed that 5'- O-methyl-3-hydroxyflemingin A (3) directly bound GLI1 ( K_d = 7.7 μM). Moreover, 5'- O-methyl-3-hydroxyflemingin A (3) diminished cancer stem cell characters of Huh7 such as sphere formation and production of the cancer stem cell marker EpCAM. These results suggest that Hh inhibitors can efficiently suppress the activity of cancer stem cells.

Cytotoxic and NF-κB and mitochondrial transmembrane potential inhibitory pentacyclic triterpenoids from Syzygium corticosum and their semi-synthetic derivatives

Syzygium is a large genus of flowering plants, with several species, including the clove tree, used as important resources in the food and pharmaceutical industries. In our continuing search for anticancer agents from higher plants, a chloroform extract of the leaves and twigs of Syzygium corticosum collected in Vietnam was found to be active toward the HT-29 human colon cancer cell line. Separation of this extract guided by HT-29 cells and nuclear factor-kappa B (NF-κB) inhibition yielded 19 known natural products, including seven triterpenoids, three ellagic acid derivatives, two methylated flavonoids, a cyclohexanone, four megastigmanes, a small lactone, and an aromatic aldehyde. The full stereochemistry of (+)-fouquierol (2) was defined for the first time. Biological investigations showed that (+)-ursolic acid (1) is the major cytotoxic component of S. corticosum, which exhibited also potent activities in the NF-κB and mitochondrial transmembrane potential (MTP) inhibition assays conducted, with IC50 values of 31 nM and 3.5 µM, respectively. Several analogues of (+)-ursolic acid (1) were synthesized, and a preliminary structure-activity relationship (SAR) study indicated that the C-3 hydroxy and C-28 carboxylic acid groups and 19,20-dimethyl substitution are all essential in the mediation of the bioactivities observed for this triterpenoid.