Targeting the protein-protein interaction between p53 and MDM2/MDMX (MDM4) represents an attractive anticancer strategy for the treatment of p53-competent tumors. Several selective and potent MDM2 inhibitors have been developed and entered the clinic; however, the repertoire of MDMX antagonists is still limited. The arylmethylidenepyrazolinone SJ-172550 has been reported as a selective MDMX antagonist; yet, uncertainties about its mechanism of action have raised doubts about its use as a chemical probe. Here, we show that, in addition to its unclear mode of action, SJ-172550 is unstable in aqueous buffers, giving rise to side products of unknown biological activity. Using an SJ-172550-derived affinity probe, we observed promiscuous binding to cellular proteins whereas cellular thermal shift assays did not reveal a stabilizing effect on MDMX. Overall, our results raise further questions about the interpretation of data using SJ-172550 and related compounds to investigate cellular phenotypes.

中文翻译：

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芳基亚甲基吡唑啉酮基MDMX抑制剂的化学稳定性和混杂性。

靶向p53和MDM2 / MDMX（MDM4）之间的蛋白质相互作用代表了一种有吸引力的抗癌策略，可用于治疗p53能力强的肿瘤。已经开发了几种选择性有效的MDM2抑制剂并进入临床。但是，MDMX拮抗剂的功能仍然很有限。据报道，芳基亚甲基吡唑啉酮SJ-172550是一种选择性的MDMX拮抗剂。然而，由于其作用机理的不确定性，人们对其用作化学探针的方法产生了怀疑。在这里，我们表明，除了其作用方式不清楚之外，SJ-172550在水性缓冲液中也是不稳定的，从而产生了生物学活性未知的副产物。使用SJ-172550衍生的亲和探针，我们观察到与细胞蛋白的混杂结合，而细胞热位移分析未显示对MDMX的稳定作用。