Heat shock protein 90 (HSP90) has been recognized as a crucial target in cancer cells. However, various toxic reactions targeting the ATP binding site of HSP90 may not be the best choice for HSP90 inhibitors. In this paper, an ellagic acid derivative, namely, okicamelliaside (OCS), with antitumor effects was found. To identify potential anti-cancer mechanisms, an OCS photosensitive probe was applied to target fishing and tracing. Chemical proteomics and protein-drug interaction experiments have shown that HSP90 is a key target for OCS, with a strong binding affinity (K_D = 6.45 μM). Mutation analysis of the target protein and molecular dynamics simulation revealed that OCS could competitively act on the key Glu-47 site at the N-terminal chaperone pocket of HSP90, where the co-chaperone CDC37 binds to HSP90, affect its stability and reduce the ∆G_bind of HSP90-CDC37. It was demonstrated that OCS destroys the protein–protein interactions of HSP90-CDC37; selectively affects downstream kinase client proteins of HSP90, including CDK4, P-AKT⁴⁷³, and P-ERK1/2; and exerts antitumor effects on A549 cells. Furthermore, tumor xenograft experiments demonstrated high antitumor activity and low toxicity of OCS in the same way. Our findings identified a novel N-terminal chaperone pocket natural inhibitor of HSP90, that is, OCS, which selectively inhibits the formation of the HSP90-CDC37 protein complex, and provided further insight into HSP90 inhibitors for anti-cancer candidate drugs.

热休克蛋白 90 (HSP90) 已被认为是癌细胞的关键靶点。然而，针对 HSP90 的 ATP 结合位点的各种毒性反应可能不是 HSP90 抑制剂的最佳选择。在本文中，发现了一种具有抗肿瘤作用的鞣花酸衍生物，即 okicamelliaside (OCS)。为了确定潜在的抗癌机制，将 OCS 光敏探针应用于目标捕捞和追踪。化学蛋白质组学和蛋白质-药物相互作用实验表明，HSP90 是 OCS 的关键靶点，具有很强的结合亲和力（K _D = 6.45 微米）。目标蛋白的突变分析和分子动力学模拟表明，OCS 可以竞争性地作用于 HSP90 N 端伴侣袋的关键 Glu-47 位点，其中辅助伴侣 CDC37 与 HSP90 结合，影响其稳定性并降低 Δ HSP90-CDC37 的G_结合。已证明 OCS 破坏了 HSP90-CDC37 的蛋白质-蛋白质相互作用；选择性影响 HSP90 的下游激酶客户蛋白，包括 CDK4、P-AKT ⁴⁷³, 和 P-ERK1/2; 对 A549 细胞具有抗肿瘤作用。此外，肿瘤异种移植实验以同样的方式证明了 OCS 的高抗肿瘤活性和低毒性。我们的研究结果确定了一种新型的 HSP90 N 端分子伴侣口袋天然抑制剂，即 OCS，它选择性地抑制 HSP90-CDC37 蛋白复合物的形成，并为抗癌候选药物的 HSP90 抑制剂提供了进一步的见解。