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Phthalocyanine-peptide conjugates for epidermal growth factor receptor targeting
Benson G Ongarora1, Krystal R Fontenot, Xiaoke Hu
1Louisiana State University, Department of Chemistry, Baton Rouge, Louisiana 70803, USA.
Abstract:
Four phthalocyanine (Pc)-peptide conjugates designed to target the epidermal growth factor receptor (EGFR) were synthesized and evaluated in vitro using four cell lines: human carcinoma A431 and HEp2, human colorectal HT-29, and kidney Vero (negative control) cells. Two peptide ligands for EGFR were investigated: EGFR-L1 and -L2, bearing 6 and 13 amino acid residues, respectively. The peptides and Pc-conjugates were shown to bind to EGFR using both theoretical (Autodock) and experimental (SPR) investigations. The Pc-EGFR-L1 conjugates 5a and 5b efficiently targeted EGFR and were internalized, in part due to their cationic charge, whereas the uncharged Pc-EGFR-L2 conjugates 4b and 6a poorly targeted EGFR maybe due to their low aqueous solubility. All conjugates were nontoxic (IC(50) > 100 μM) to HT-29 cells, both in the dark and upon light activation (1 J/cm(2)). Intravenous (iv) administration of conjugate 5b into nude mice bearing A431 and HT-29 human tumor xenografts resulted in a near-IR fluorescence signal at ca. 700 nm, 24 h after administration. Our studies show that Pc-EGFR-L1 conjugates are promising near-IR fluorescent contrast agents for CRC and potentially other EGFR overexpressing cancers.
Insights
New phthalocyanine-peptide conjugates target epidermal growth factor receptor (EGFR) for cancer imaging. These near-infrared fluorescent agents show promise for diagnosing colorectal cancer (CRC) and other EGFR-overexpressing tumors.
Area of Science:
- Bioconjugate Chemistry
- Molecular Imaging
- Cancer Therapeutics
Background:
- Epidermal growth factor receptor (EGFR) is a key target in several cancers.
- Phthalocyanine (Pc) conjugates offer potential as near-infrared (NIR) fluorescent contrast agents.
- Targeted delivery of imaging agents can improve diagnostic accuracy.
Purpose of the Study:
- To synthesize and evaluate novel phthalocyanine-peptide conjugates for EGFR targeting.
- To assess the in vitro and in vivo performance of these conjugates as NIR fluorescent contrast agents.
- To investigate the potential of these agents for diagnosing colorectal cancer (CRC) and other EGFR-overexpressing malignancies.
Main Methods:
- Synthesis of four Pc-peptide conjugates utilizing two EGFR-binding peptides (EGFR-L1 and -L2).
- In vitro evaluation using human carcinoma (A431, HEp2), colorectal (HT-29), and kidney (Vero) cell lines.
- Binding affinity and internalization studies using Surface Plasmon Resonance (SPR) and Autodock.
- In vivo imaging in nude mice bearing human tumor xenografts after intravenous administration.
Main Results:
- Pc-EGFR-L1 conjugates (5a, 5b) demonstrated efficient EGFR targeting and internalization, attributed to their cationic charge.
- Uncharged Pc-EGFR-L2 conjugates (4b, 6a) showed poor targeting, potentially due to low aqueous solubility.
- All synthesized conjugates exhibited no toxicity to HT-29 cells (IC(50) > 100 μM) under dark and light conditions.
- In vivo studies showed significant NIR fluorescence signal (ca. 700 nm) 24 hours post-administration of conjugate 5b in tumor xenografts.
Conclusions:
- Pc-EGFR-L1 conjugates are effective EGFR-targeted NIR fluorescent contrast agents.
- These conjugates show significant potential for the diagnosis of colorectal cancer (CRC).
- The developed agents may also be applicable to other cancers overexpressing EGFR.
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