Chaetocin

In SL-2 Drosophila tissue culture cells, Chaetocin causes the inhibition of SU(VAR)3-9 and the number of H3 molecules dimethylated at Lys9, and also inhibits cell growth. ^[1]

In HepG2, Hep3B, and Huh7 human hepatoma cells, Chaetocin inhibits HIF-1-Mediated hypoxic responses. ^[2]

Chaetocin also potently inhibits proliferation and colony formation in a broad range of cancer cell lines with IC50 of 2-10 nM. ^[3]

In Hepa 1c1c-7 tumor-bearing mice, Chaetocin (0.25 mg/kg, i.p.) inhibits tumor growth by deregulating HIF-1[alpha]-mediated angiogenesis. ^[2]

In SKOV3 tumor-bearing nude mice, chaetocin treatment (0.25 mg/kg, i.p.) significantly delays the tumor growth with minimal evidence of toxicities. ^[3]

• Methylation assays

  Unless otherwise stated, reactions are performed as followed: 1 g of purified enzyme (dSU(VAR)3-9 213; GST-hSUV39H1(82-412); GST-ncDIM5(19-318) and GSTmG9a(621-1000); dPRSET7(1-691); His-SET7/9(109-366) or enzyme complex expressed in a baculoviral expression system (dE(z), dSU(Z)12, dp55, dESC) were incubated for 30 minutes with 1 g of a peptide containing the first 19 amino acids of H3 plus an additional cystein residue (ARTKQTARKSTGGKAPRKQC) in a total volume of 40μl in BC25 (10mM HEPES pH7.6, 25mM NaCl, 1mM EDTA, 10%glycerol). All enzymes except for the E(z) complex had a similar specific activity between 5-10 nmole/min/mg. For the E(z) complex, the specific activity is approximately 5-10 fold lower, which is probably due to an incomplete formation of the full complex that is required for the highest activity. As a methyl donor S-Adenosyl [methyl-3H] methionine (SAM) is present in the reaction at a final concentration of 40 M with a specific activity of 0.3Ci/mmole. Reactions are stopped by adding 1/10 volume of 100% acetic acid and the incorporation of radioactivity is measured by spotting 30 l of the reaction on P81 filter paper and subsequent scintillation counting. For the inhibitor screening, 1 l of inhibitor with a concentration of 10 g/l is added to each reaction. In the cases where PRSET7 or the E(z) complex is used as enzyme either recombinant nucleosomes (1 g) or recombinant H3 (1 g) respectively replaced the H3 peptide as a substrate.

• Cell lines

  HEK293T

• Concentrations

  125 nM

• Incubation Time

  24 h

• Method

  Cells were treated with chaetocin (125 nM) or DMSO for 24 h.

• Animal Models

  Hur7 tumor-bearing mice, Hepa 1c1c-7 tumor-bearing mice

• Dosages

  0.25 mg/kg

• Administration

  i.p.