Abstract 143: Novel HSP40 or J domain protein inhibitors that deplete misfolded mutant p53

Abstract Background: Accumulation of oncogenic mutant p53 (mutp53) greatly contributes to cancer progression. Heat shock protein 40 (HSP40), also known as J-domain proteins (JDPs), has been implicated in stabilization of misfolded mutp53. Specifically, knockdown of DNAJA1, a member of HSP40/JDPs, results in degradation of mainly misfolded mutp53, leading to inhibition of tumor progression. Since no DNAJA1 inhibitors are currently available in clinics, these findings prompted us to identify potential DNAJA1 inhibitors which can induce mutp53 degradation. Methods/Design: An in-silico docking study was performed for binding of the DNAJA1 J-domain to compounds in zinc data base, which identified compound Number7-3. Further analysis suggests three critical amino acids in DNAJA1 for the binding, including Y7, K44, and Q47. Results: Eighteen commercially available analogs of Number7-3 were further examined. Of these, a compound, namely A11, had the strongest activity to deplete both DNAJA1 and misfolded mutp53. A11 reduced protein levels of misfolded mutp53 in concentration- and time-dependent manners without affecting mRNA levels of DNAJA1 and mutp53. Importantly, A11 showed minimal effects on the levels of wild-type p53 and DNA contact mutp53. Treatment of cells expressing misfolded mutp53 with A11 resulted in reduced filopodia formation and cell migration, which was not observed in cells lacking DNAJA1. Moreover, protein levels of a triple mutant DNAJA1 (Y7A/K44A/Q47A) were not altered by A11. Intriguingly, A11 reduced protein levels of several other HSP40/JDPs. Conclusions: Our study, for the first time, has identified a small compound that depletes DNAJA1, leading to reduced levels of misfolded mutp53 and inhibited malignant properties of cancer cells. Citation Format: Tomoo Iwakuma, Shigeto Nishikawa, Atsushi Kaida, Atul Ranjan, Alejandro Parrales, Mohamed A. Alalem, David K. Johnson. Novel HSP40 or J domain protein inhibitors that deplete misfolded mutant p53 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 143.