UNC0638 is a potent and selective inhibitor of G9a and GLP with IC50 values of < 15 nM and 19 ± 1 nM, respectively [1].
GLP forms a heterodimer with G9a. Both G9a and GLP can mono- and dimethylate histone H3 Lys9 (H3K9), and dimethylate Lys373 of p53 and hence inactivate the transcriptional activity of p53 [1].
UNC0638 showed balanced physicochemical properties and potency aiding cell penetration in vitro, had high potency in cellular assays. It was much less toxic than BIX01294 to cells. In MDA-MB-231 cells, in a concentration-dependent manner, exposure to UNC0638 for 48 h reduced H3K9me2 levels with an IC50 value of 81 ± 9 nM (n= 3), which showed considerably higher potency than BIX01294 (IC50= 500 ± 43 nM (n= 3)). In reducing H3K9me2 levels, UNC0638 was of greater maximum effect than BIX01294. This effect is close, but not equal, to the effect on the double knockdown of G9a and GLP via shRNA [1].
In 6-week-old male athymic nude mice subcutaneously inoculated with BON cells, UNC0638 decreased H3K9me2 level [2]. In organotypic cochlear cultures, rapid increase of H3K9me2 upon the damage of hair cells was observed. Both ex vivo and in vivo, UNC0638 effectively prevented aminoglycosides-induced hair cell damage [3].
References:
[1]. Vedadi M., Barsyte-Lovejoy D., Liu F., et al. A chemical probe selectively inhibits G9a and GLP methyltransferase activity in cells. Nature Chemical Biology, 2011, 7:566-574.
[2]. Kim J.T., Li J., Jang E.R., et al. Deregulation of Wnt/β-catenin signaling through genetic or epigenetic alterations in human neuroendocrine tumors. Clin. Carcinogenesis, 2013, 00(00):1-9.
[3]. Yu H., Lin Q., Wang Y., et al. Inhibition of H3K9 methyltransferases G9a/GLP prevents ototoxicity and ongoing hair cell death. Cell Death and Disease, 2013, 4:e506.