Dimethyl fumarate inhibits ZNF217 and can be beneficial in a subset of estrogen receptor positive breast cancers.

PURPOSE: The oncogenic factor ZNF217 promotes aggressive estrogen receptor (ER)+breast cancer disease suggesting that its inhibition may be useful in the clinic. Unfortunately, no direct pharmacological inhibitor is available. Dimethyl fumarate (DMF) exhibits anti-breast cancer activities, in vitro and in pre-clinical in vivo models. Its therapeutic benefits stem from covalent modification of cellular thiols such as protein cysteines, but the full profile of molecular targets mediating its anti-breast cancer effects remains to be determined.

METHODS: ER+breast cancer cells were treated with DMF followed by cysteine-directed proteomics. Cells with modulated ZNF217 levels were used to probe the efficacy of DMF.

RESULTS: Covalent modification of ZNF217 by DMF identified by proteomics was confirmed by using a DMF-chemical probe. Inhibition of ZNF217's transcriptional activity by DMF was evident on reported ZNF217-target genes. ZNF217 as an oncogene has been shown to enhance stem-like properties, survival, proliferation, and invasion. Consistent with ZNF217 inhibition, DMF was more effective at blocking these ZNF217-driven phenotypes in cells with elevated ZNF217 expression. Furthermore, partial knockdown of ZNF217 led to a reduction in DMF's efficacy. DMF's in vivo activity was evaluated in a xenograft model of MCF-7 HER2 cells that have elevated expression of ZNF217 and DMF treatment resulted in significant inhibition of tumor growth.

CONCLUSION: These data indicate that DMF's anti-breast cancer activities in the ER+HER2+models, at least in part, are due to inhibition of ZNF217. DMF is identified as a new covalent inhibitor of ZNF217.