Selective inhibition of p300 by a novel small molecule EPS496 promotes cell death in vemurafenib-resistant BRAFV600E mutated melanoma cells

Abstract

Background: Melanoma, a highly aggressive skin cancer is frequently driven by the BRAF^V600E mutation. Vemurafenib initially offers clinical benefits but often encounters resistance due to secondary mutations and compensatory signaling pathways. Targeting p300, a histone acetyltransferase involved in transcriptional regulation and resistance mechanisms, presents a potential strategy to overcome this therapeutic challenge.

Methods: A virtual screening was conducted to identify small molecules targeting p300. Molecular dynamics simulations (MDS), Root Mean Square Deviation (RMSD), and Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) were employed for computational predictions. Normal (A2058, A375, and SK-MEL-28) and vemurafenib-resistant A2058^VR, A375 ^VR, and SK-MEL-28 ^VR melanoma cells were used for cell-based assays.

Results: EPS496 was identified as a p300 inhibitor, demonstrating high binding stability with a low RMSD value during the MDS. MMPBSA analysis revealed highly favorable binding energy, indicating strong and stable interaction with p300. EPS496 effectively inhibited the proliferation of normal melanoma cells with GI₅₀ values of 367.8 nM, 986.4 nM, and 642.1 nM in A375, SK-MEL-28, and A2058 respectively. The compound retained the anti-proliferative efficacy in the resistant A375^VR, SK-MEL-28^VR, and A2058^VR with respective GI₅₀ values of 345.6 nM, 1018 nM, and 708.5 nM. Whereas vemurafenib was less active several folds in the resistant cells. EPS496 promoted early, and phase apoptosis and reduced p300-positive populations in the vemurafenib-resistant melanoma cells.

Conclusion: EPS496, through its inhibition of p300, provides a novel approach to counteract vemurafenib resistance in melanoma. Results highlight its potential to be developed as an effective therapeutic agent for combating melanoma.

Keywords: BRAF (V600E) mutation; EPS496; Melanoma; P300 inhibition; Vemurafenib resistance.