Targeting the Inactive Conformation of the Epidermal Growth Factor Receptor Identifies EG31: A Novel Small Molecule Inhibitor Effective Against Normal and 5-Fluorouracil-Resistant Triple Negative Breast Cancer Cells

Background: Triple-negative breast Cancer (TNBC) is an aggressive subtype of breast Cancer characterized by the absence of estrogen, progesterone, and HER2 receptors, making it difficult to treat with targeted therapies. The Epidermal Growth Factor Receptor (EGFR) is overexpressed in TNBC and is crucial in promoting tumor growth and survival. Despite chemotherapeutics like 5-fluorouracil (5-FU), resistance remains a clinical challenge, underscoring the need for novel therapeutic strategies.

Methods: High-throughput virtual screening (HTVS) was employed to identify inhibitors targeting the inactive conformation of EGFR. The top-ranked compounds underwent molecular dynamics (MD) simulations and binding free energy calculations using Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA). MDA-MB-231, Hs578T, and 5-FU resistant- MDA-MB-231/5-FU^R cells were utilized to assess the anti-proliferative, EGFR, and Apoptosis.

Results: HTVS identified EG31 showing strong binding affinities towards EGFR. MD simulations confirmed the stable binding of EG31 to EGFR, as indicated by consistent Root Mean Square Deviation and hydrogen bond patterns throughout the simulation. MMPBSA calculations revealed highly favorable binding free energies. EG31 inhibited MDA-MB-231 and Hs578T proliferations with GI₅₀ values of 498.90 nM and 740.73 nM, respectively. The compound decreased EGFR-positive populations and favored early and late-phase Apoptosis in these cells. Furthermore, EG31 retained the anti-proliferative efficacy in the MDA-MB-231/5-FU^R cells, while 5-FU lost its effectiveness by 6-fold.

Conclusion: This study identified EG31 targeting the inactive conformation of EGFR, offering a promising therapeutic approach to overcome 5-FU resistance in TNBC. Further research could enhance treatment efficacy and provide a new avenue for managing this challenging Cancer subtype.

5-fluorouracil resistance; epidermal growth factor receptor; molecular dynamics simulation; small molecule inhibitors; triple-negative breast cancer.