PR-619 (2,6-Diamino-3,5-dithiocyanopyridine) is a DUB inhibitor that inhibits USP2/4/5/7/8 (EC50=7.2/3.93/8.61/6.86/4.9 μM). PR-619 induces endoplasmic reticulum stress and activates autophagy.

USP8:4.90 μM(EC50), SENP6 core:2.37 μM(EC50), UCHL3:2.95 μM(EC50), JOSD2:1.17 μM(EC50), USP4:3.93 μM(EC50)

METHODS: HEK293T cells were treated with PR-619 (5-50 µM) for 6 h. Target protein expression levels were measured by Western Blot.
RESULTS: PR-619 interfered with probe labeling at concentrations of 5 µM and above. PR-619 inhibited probe labeling of USP7, but also targeted many other DUBs in the same concentration range, consistent with its broader inhibitory profile. [1]
METHODS: The leukemia cell line K562 was treated with PR-619 (40 µM) for 2 h. Targeting was detected by Immunofluorescence.
RESULTS: PR-619 induced a different distribution of TOP2A and TOP2B fluorescence signals, consisting of large signal foci. FK2 ubiquitin fluorescence signals partially overlapped with those of TOP2A and TOP2B, as well as SUMO2/3. [2]

METHODS: To detect anti-tumor activity in vivo, PR-619 (10 mg/kg once daily) and cisplatin (10 mg/kg three times weekly) were intraperitoneally injected into Nude mice bearing T24 or BFTC-905 xenografts for three weeks.
RESULTS: The combination of cisplatin and PR-619 showed the most significant antitumor effects on T24 and BFTC-905 xenograft tumors compared to monotherapy. [3]

Ub-PLA2 assay: Recombinant enzymes in 20 mM Tris-HCl, pH 8.0, 2 mM CaCl2 and 2 mM β-mercaptoethanol (DUB assay buffer) are preincubated with single doses or dose ranges of PR-619 or P22077 for 30 minutes in a 96 well plate before the addition of Ub-PLA2 and NBD C6-HPC. The liberation of a fluorescent product within the linear range of the assay is monitored at room temperature using a fluorescence plate reader. Vehicle (2%(v/v) DMSO) and 10 mM N-ethylmaleimide are included as controls. Where ≥60% inhibition is observed, EC50 values are determined using a sigmoidal dose response equation.

72 h hours later, 0.2 mg/mL resazurin prepared in phosphate-buffered saline is added to each well and the cells are incubated for an additional 3-6 h. The fluorescence of the resazurin reduction product is measured using Ex=535 nm and Em=590 nm filters on a fluorimeter. The EC50 values are calculated in Prism.(Only for Reference)