EVALUATION OF THE AFFINITY OF RADIOLABELED PEPTIDE [¹³¹I]I-DEDEYFELV FOR EGFR-OVEREXPRESSING RECEPTORS IN ADULT-TYPE DIFFUSE GLIOMAS

Abstract

Introduction/Justification

Cancer remains one of the leading causes of death worldwide. Among the various tumor sites, the central nervous system is particularly significant, with gliomas accounting for the majority of primary brain tumors. In gliomas, alterations in the tyrosine kinase pathway lead to the overexpression of the Epidermal Growth Factor receptor (EGFr). Over the past decades, radiolabeled peptides with high affinity for EGFr have emerged as promising molecular targets with potential applications in both diagnosis and therapy.

Objectives

This study aimed to evaluate the affinity of the peptide DEDEYFELV, radiolabeled with iodine-131 (¹³¹I), for EGFr-overexpressing receptors in adult-type diffuse gliomas using tumor tissue samples.

Materials and Methods

The peptide was synthesized using solid-phase peptide synthesis following the Fmoc/tBu strategy. Upon completion of the synthesis, the peptide was characterized and purified via high-performance liquid chromatography (HPLC). DEDEYFELV (20 nmol) was radiolabeled with [¹³¹I]NaI (18.5 MBq) using the chloramine-T method. The radiochemical yield of [¹³¹I]I-DEDEYFELV was determined via chromatography on Whatman 3MM strips using a 95% MeOH / 5% H₂O eluent. Binding studies of [¹³¹I]I-DEDEYFELV with neoplastic tissue homogenates were conducted at 1 and 4 h of incubation and quantified using an automatic gamma counter. Tumor tissue homogenates were obtained from surgical resections performed by a designated neurosurgeon, following informed consent. Gliomas were confirmed through pathological analysis, and tumor samples were preserved at -80°C. All human protocols adhered to local ethical guidelines (Protocol number CEP – FCMSCSP: CAAE 79336124.7.0000.5479). Statistical analysis was conducted using ANOVA or Student's t-test.

Results

The peptide DEDEYFELV was successfully synthesized with a yield of approximately 92%. Mass spectrometry and HPLC analyses confirmed efficient synthesis, cleavage, and purification, as evidenced by a single peak and a molecular mass corresponding to the expected peptide. Radiolabeling was achieved with a radiochemical yield exceeding 95%. Binding studies of [¹³¹I]I-DEDEYFELV with neoplastic tissue homogenates showed values of 3.25 ± 0.31% for high-grade tumors, 2.62 ± 0.34% for low-grade tumors, and 1.61 ± 0.25% for tumors of unknown grade at 1 h of incubation (n = 5). At 4 h, the binding values increased to 6.45 ± 0.66% for high-grade tumors, 10.27 ± 1.58% for low-grade tumors, and 7.74 ± 1.21% for tumors of unknown grade (n = 5).

Conclusion

These findings demonstrate that the radiolabeled peptide [¹³¹I]I-DEDEYFELV exhibits specific binding to EGFr-overexpressing tumor tissues, with an increasing affinity over time. The higher binding observed at 4 h suggests favorable interaction dynamics, particularly in low-grade gliomas. These results highlight the potential of [¹³¹I]I-DEDEYFELV as a theranostic agent for EGFr-targeted imaging and therapy, warranting further investigations into its in vivo stability and clinical applicability.