Triple-negative breast cancer (TNBC) represents one of the most aggressive subtypes of breast cancer. Glioblastoma (GBM) is the most lethal primary brain tumor, characterized by poor prognosis. Both malignancies frequently overexpress the epidermal growth factor receptor (EGFR), which contributes to tumor progression by promoting proliferation, angiogenesis, and resistance to apoptosis. The GE11 peptide, YHWYGYTPQNVI, exhibits high affinity for EGFR and has been explored as a targeting ligand in molecular imaging strategies. Here, a modified GE11-derived peptide, YHAYGYTPQNVI, was employed, in which tryptophan was substituted by alanine to reduce photosensitivity.

To evaluate the in vitro effects of the YHAYGYTPQNVI peptide on cell proliferation and viability in TNBC (MDA-MB-231) and GBM (U-87 MG) cells.

MDA-MB-231 and U-87 MG cells were cultured in RPMI-1640 or DMEM, respectively, supplemented with 10% fetal bovine serum (37°C; 5% CO2). Cell proliferation was assessed by growth curve analysis. Cells were seeded in 6-well plates (5 × 104 cells/well) and treated with YHAYGYTPQNVI (56.1 µM). Viable cell counts were performed on days 1, 3, 5, and 7, comparing with untreated control (CT). Cell viability was evaluated by the MTT assay in MDA-MB-231 cells seeded in 96-well plates (5 × 10³ cells/well) and treated with YHAYGYTPQNVI (5.61 µM). MTT measurements were obtained on days 1, 5, and 7, and viability was expressed as a percentage relative to CT. Data are presented as mean ± SD. Statistical analyses were performed using Student’s t-test or ANOVA followed by Tukey’s test, with significance set at p<0.05.

Growth curve analysis of MDA-MB-231 cells revealed no statistically significant differences between the GE11-derived peptide-treated and CT groups, as illustrated on day 7: YHAYGYTPQNVI = (3.18 ± 0.40) × 105 versus CT = (3.43 ± 0.58) × 105 [p = 0.4501; n = 6]. Consistently, MTT assays indicated a moderate reduction in cell viability (∼15–25%); however, this reduction was not statistically significant over time, with viabilities of 83.66 ± 6.24% (day 1), 74.11 ± 12.24% (day 5), and 79.76 ± 8.02% (day 7) [p = 0.1885; n = 7]. In contrast, growth curve analysis of U-87 MG cells demonstrated a significant inhibition of cell proliferation following treatment with the anti-EGFR peptide. On day 5, treated cells reached (0.87 ± 0.11) × 105 cells compared with (1.67 ± 0.21) × 105 in the CT group [p = 0.0001; n = 6]. This inhibitory effect persisted on day 7, with counts of (1.83 ± 0.23) × 105 versus (3.20 ± 0.66) × 105 for treated and CT cells, respectively [p = 0.0019; n = 6]. MTT assays for the U-87 MG cell line are currently ongoing. The differential responses observed between MDA-MB-231 and U-87 MG cells suggest that EGFR expression alone does not fully predict sensitivity to GE11-derived peptides, indicating the influence of tumor-specific receptor dynamics and downstream signaling mechanisms.

The YHAYGYTPQNVI peptide exhibited a significant antiproliferative effect in the U-87 MG cells, whereas no comparable response was observed in MDA-MB-231 cells. These findings highlight the heterogeneity of EGFR-mediated interactions across tumor types and support further investigations to elucidate the underlying biological mechanisms. Additional radiolabeling studies may help clarify the potential of this peptide as a targeting molecular imaging probe in EGFR-expressing tumors.