Deciphering Glutathione S-Transferase P1 Inhibition Mechanisms for Overcoming Cancer Chemoresistance: Insights From Computational Analysis.

Glutathione S-transferase P1 (GSTP1) plays a crucial role in detoxifying cytotoxic agents and contributes to cancer chemoresistance. Due to its key role in tumor progression and its impact on treatment efficacy, GSTP1 has emerged as a promising therapeutic target for anticancer therapies. Ethacrynic acid (EA) is a known GSTP1 inhibitor; however, the specific molecular mechanisms behind its inhibitory action remain unclear. To clarify the effects of EA and its glutathione conjugate (EA-GSH) on the GSTP1 dimer, we conducted a comparative molecular dynamics (MD) study of four enzymatic states: apo (unbound), holo (GSH-bound), the GSTP1-EA and GSTP1-EA-GSH complexes, to analyze both interchain and ligand-enzyme interactions. Our results showed that GSTP1 flexibility depends on the movement of the α2 helix, which appears essential for accommodating substrates. Ligand binding made the enzyme more rigid, and EA disrupted dynamic coordination within the dimer by altering secondary-structure elements, potentially impairing enzymatic activity. Additionally, EA influenced dimerization by reducing binding energy at the dimer interface, possibly interfering with GSTP1's nonenzymatic role in apoptosis signaling. Energy analysis demonstrated that while GSH conjugation enhanced EA's binding affinity through favorable electrostatic interactions, it also imposed a significant energetic penalty due to increased solvent exposure. These findings highlight the need to optimize the lipophilic/hydrophilic balance of future GSTP1 inhibitors to match the physicochemical properties of the binding pocket. Overall, this study offers a deeper understanding of the molecular mechanisms behind GSTP1 inhibition and provides a structural basis for designing targeted therapies to overcome cancer chemoresistance.