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A useful EGFR-TK ligand for tumor diagnosis with SPECT: development of radioiodinated 6-(3-morpholinopropoxy)-7-ethoxy-4-(3'-iodophenoxy)quinazoline.

Hirata M, Kanai Y, Naka S, Yoshimoto M, Kagawa S, Matsumuro K, Katsuma H, Yamaguchi H, Magata Y, Ohmomo Y - Ann Nucl Med (2013)

Bottom Line: Six quinazoline derivatives were designed and synthesized, and among these, 6a-d were found to have relatively high EGFR-TK inhibitory potency.In contrast, [(125)I]PYK was rapidly cleared from peripheral tissues, resulting in a high tumor-to-tissue ratio 24 h after injection.Moreover, the EGFR-TK selectivity of [(125)I]PYK was confirmed by pretreatment experiments with specific EGFR-TK inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Osaka, Takatsuki 569-1094, Japan.

ABSTRACT

Objective: Epidermal growth factor receptor tyrosine kinase (EGFR-TK) represents an attractive target for tumor diagnosis agents. Previously, radioiodinated 4-(3-iodophenoxy)-6,7-diethoxyquinazoline (PHY) was reported to possess good characteristics as a tumor imaging agent. We have explored the feasibility of developing tumor diagnosis ligands superior to radioiodinated PHY.

Methods: New phenoxyquinazoline derivatives were designed with various side chains introduced to the 6th position of PHY. The IC50 values of the new derivatives to interrupt EGFR-TK phosphorylation were evaluated and compared to well-known EGFR-TK inhibitors. Tumor uptake studies of the new (125)I-labeled derivatives were conducted with A431 tumor-bearing mice. Selectivity and binding characteristics were analyzed by in vitro blocking studies and a binding assay. Furthermore, SPECT/CT scans were performed using A431 tumor-bearing mice.

Results: Six quinazoline derivatives were designed and synthesized, and among these, 6a-d were found to have relatively high EGFR-TK inhibitory potency. In tumor uptake studies, [(125)I]6a ([(125)I]PYK) was found to have the highest tumor uptake and longest retention in tumors. In contrast, [(125)I]PYK was rapidly cleared from peripheral tissues, resulting in a high tumor-to-tissue ratio 24 h after injection. Moreover, the EGFR-TK selectivity of [(125)I]PYK was confirmed by pretreatment experiments with specific EGFR-TK inhibitors. Furthermore, [(125)I]PYK provided clear SPECT images of tumors.

Conclusions: Radioiodinated PYK, one of the newly synthesized quinazoline derivatives, was found to be a desirable ligand for EGFR-TK SPECT imaging. [(125)I]PYK showed high tumor accumulation and selective EGFR-TK binding and also succeeded in delivering high contrast imaging of tumors. These favorable characteristics of [(125)I]PYK suggest that the (123)I-labeled counterpart, [(123)I]PYK, would have great potential for diagnostic SPECT tumor imaging.

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Binding assay of [125I]PYK to EGFR-TK in A431 cell membranes. a Binding curves of [125I]PYK; total binding (closed circle), specific binding (closed triangle), non-specific binding (closed square). b Scatchard plot of the binding. Data represent mean ± SD, n = 5
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Fig6: Binding assay of [125I]PYK to EGFR-TK in A431 cell membranes. a Binding curves of [125I]PYK; total binding (closed circle), specific binding (closed triangle), non-specific binding (closed square). b Scatchard plot of the binding. Data represent mean ± SD, n = 5

Mentions: The crude P2 membrane fraction from A431 or NAlM6 cells were used in further binding experiments for pharmacological characterization. The saturation binding of [125I]PYK was analyzed using Scatchard analysis (Fig. 6), and the resulting linear Scatchard plot indicated that [125I]PYK bound to a single population of binding site with high affinity. Kinetic parameters from the analysis were Bmax = 27.0 ± 3.43 pmol/mg protein and Kd = 51.3 ± 11.1 nM. While, in the NALM6 as a negative-EGFR leukemia cell line [24], [125I]PYK binding to cell membranes was undetectable.Fig. 6


A useful EGFR-TK ligand for tumor diagnosis with SPECT: development of radioiodinated 6-(3-morpholinopropoxy)-7-ethoxy-4-(3'-iodophenoxy)quinazoline.

Hirata M, Kanai Y, Naka S, Yoshimoto M, Kagawa S, Matsumuro K, Katsuma H, Yamaguchi H, Magata Y, Ohmomo Y - Ann Nucl Med (2013)

Binding assay of [125I]PYK to EGFR-TK in A431 cell membranes. a Binding curves of [125I]PYK; total binding (closed circle), specific binding (closed triangle), non-specific binding (closed square). b Scatchard plot of the binding. Data represent mean ± SD, n = 5
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3672506&req=5

Fig6: Binding assay of [125I]PYK to EGFR-TK in A431 cell membranes. a Binding curves of [125I]PYK; total binding (closed circle), specific binding (closed triangle), non-specific binding (closed square). b Scatchard plot of the binding. Data represent mean ± SD, n = 5
Mentions: The crude P2 membrane fraction from A431 or NAlM6 cells were used in further binding experiments for pharmacological characterization. The saturation binding of [125I]PYK was analyzed using Scatchard analysis (Fig. 6), and the resulting linear Scatchard plot indicated that [125I]PYK bound to a single population of binding site with high affinity. Kinetic parameters from the analysis were Bmax = 27.0 ± 3.43 pmol/mg protein and Kd = 51.3 ± 11.1 nM. While, in the NALM6 as a negative-EGFR leukemia cell line [24], [125I]PYK binding to cell membranes was undetectable.Fig. 6

Bottom Line: Six quinazoline derivatives were designed and synthesized, and among these, 6a-d were found to have relatively high EGFR-TK inhibitory potency.In contrast, [(125)I]PYK was rapidly cleared from peripheral tissues, resulting in a high tumor-to-tissue ratio 24 h after injection.Moreover, the EGFR-TK selectivity of [(125)I]PYK was confirmed by pretreatment experiments with specific EGFR-TK inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Osaka, Takatsuki 569-1094, Japan.

ABSTRACT

Objective: Epidermal growth factor receptor tyrosine kinase (EGFR-TK) represents an attractive target for tumor diagnosis agents. Previously, radioiodinated 4-(3-iodophenoxy)-6,7-diethoxyquinazoline (PHY) was reported to possess good characteristics as a tumor imaging agent. We have explored the feasibility of developing tumor diagnosis ligands superior to radioiodinated PHY.

Methods: New phenoxyquinazoline derivatives were designed with various side chains introduced to the 6th position of PHY. The IC50 values of the new derivatives to interrupt EGFR-TK phosphorylation were evaluated and compared to well-known EGFR-TK inhibitors. Tumor uptake studies of the new (125)I-labeled derivatives were conducted with A431 tumor-bearing mice. Selectivity and binding characteristics were analyzed by in vitro blocking studies and a binding assay. Furthermore, SPECT/CT scans were performed using A431 tumor-bearing mice.

Results: Six quinazoline derivatives were designed and synthesized, and among these, 6a-d were found to have relatively high EGFR-TK inhibitory potency. In tumor uptake studies, [(125)I]6a ([(125)I]PYK) was found to have the highest tumor uptake and longest retention in tumors. In contrast, [(125)I]PYK was rapidly cleared from peripheral tissues, resulting in a high tumor-to-tissue ratio 24 h after injection. Moreover, the EGFR-TK selectivity of [(125)I]PYK was confirmed by pretreatment experiments with specific EGFR-TK inhibitors. Furthermore, [(125)I]PYK provided clear SPECT images of tumors.

Conclusions: Radioiodinated PYK, one of the newly synthesized quinazoline derivatives, was found to be a desirable ligand for EGFR-TK SPECT imaging. [(125)I]PYK showed high tumor accumulation and selective EGFR-TK binding and also succeeded in delivering high contrast imaging of tumors. These favorable characteristics of [(125)I]PYK suggest that the (123)I-labeled counterpart, [(123)I]PYK, would have great potential for diagnostic SPECT tumor imaging.

Show MeSH
Related in: MedlinePlus