Benzothiazolyl and Benzoxazolyl Hydrazones Function as Zinc Metallochaperones to Reactivate Mutant p53

We identified a set of thiosemicarbazone
(TSC) metal ion chelators
that reactivate specific zinc-deficient p53 mutants using a mechanism
called zinc metallochaperones (ZMCs) that restore zinc binding by
shuttling zinc into cells. We defined biophysical and cellular assays
necessary for structure–activity relationship studies using
this mechanism. We investigated an alternative class of zinc scaffolds
that differ from TSCs by substitution of the thiocarbamoyl moiety
with benzothiazolyl, benzoxazolyl, and benzimidazolyl hydrazones.
Members of this series bound zinc with similar affinity and functioned
to reactivate mutant p53 comparable to the TSCs. Acute toxicity and
efficacy assays in rodents demonstrated C1 to be significantly
less toxic than the TSCs while demonstrating equivalent growth inhibition.
We identified C85 as a ZMC with diminished copper binding
that functions as a chemotherapy and radiation sensitizer. We conclude
that the benzothiazolyl, benzoxazolyl, and benzimidazolyl hydrazones
can function as ZMCs to reactivate mutant p53 in vitro and in vivo.

我们筛选得到一类氨基硫脲（thiosemicarbazone, TSC）类金属离子螯合剂，该类化合物可通过锌金属伴侣（zinc metallochaperones, ZMCs）机制复活特定的锌缺陷型p53突变体——该机制通过将锌转运进入细胞，以恢复突变体的锌结合能力。我们明确了采用该机制开展构效关系研究所需的生物物理与细胞实验方法。我们研究了一类与TSC结构相异的锌骨架化合物，这类化合物将TSC中的硫代氨基甲酰基替换为苯并噻唑基、苯并恶唑基或苯并咪唑基腙。该系列化合物与锌的结合亲和力与TSC相当，且同样可复活突变型p53，效果与TSC类化合物相近。啮齿类动物的急性毒性与药效学实验结果显示，化合物C1的毒性显著低于TSC类化合物，但其生长抑制活性与TSC相当。我们还筛选得到C85这一锌金属伴侣，其铜结合能力减弱，可作为化疗与放射增敏剂发挥作用。综上，苯并噻唑基、苯并恶唑基及苯并咪唑基腙类化合物可作为锌金属伴侣，在体外与体内实现突变型p53的复活。