Melanoma targeting with α-melanocyte stimulating hormone analogs labeled with fac-[99mTc(CO)3]+:: effect of cyclization on tumor-seeking properties
Melanoma targeting with α-melanocyte stimulating hormone analogs labeled with fac-[99mTc(CO)3]+:: effect of cyclization on tumor-seeking properties
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DOI：
10.1007/s00775-007-0338-3
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发表时间：
2008-03-01
影响因子：
3
通讯作者：
Santos, Isabel
中科院分区：
文献类型：
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作者：
Raposinho, Paula D.;Xavier, Catarina;Santos, Isabel
原发性黑色素瘤的早期检测至关重要，因为转移性黑色素瘤没有有效的治疗方法。几种线性和环状放射性标记的α-黑素细胞刺激激素（α-MSH）类似物已被提议用于靶向黑色素瘤中过度表达的黑皮质素1型受体（MC1R）。铼环化 α-MSH 类似物 (Re-CCMSH) 的紧凑结构显着增强了其在体内肿瘤的摄取和保留。 Melanotan II (MT-II) 是 α-MSH (Ac-Nle-cyclo[Asp-His-DPhe-Arg-Trp-Lys]-NH2]) 的环状内酰胺类似物，是一种非常有效且稳定的激动剂肽，主要用于黑皮质素受体的表征。利用与 MT-II 环肽相关的优异生物学特性，我们通过比较 (99)mTc 标记的环肽 β Ala-Nle-cyclo[Asp-His-DPhe-Arg-Trp-Lys]-NH2 与线性类似物 β 的药代动力学特征，评估了基于内酰胺的环化对 α-MSH 类似物寻瘤特性的影响患有黑色素瘤的小鼠中的 Ala-Nle-Asp-His-DPhe-Arg-Trp-Lys-NH2。我们合成了线性和环状肽，并将其通过 β Ala 的氨基与含有吡唑基二胺主链 (pz) 的双功能螯合剂偶联，所得 pz-肽缀合物与 fac-[Tc-99m(CO)(3)](+) 部分反应。 Tc-99m(CO)(3) 标记的缀合物产量高、比活性高、放射化学纯度高。环状 Tc-99m(CO)(3) 标记的缀合物在鼠黑色素瘤 B16F1 细胞中表现出显着的内化作用（37℃ 6 小时后，受体结合示踪剂的 87.1% 和总应用活性的 50.5%）和细胞保留（5 小时后仅从细胞释放 24.7%）。循环放射性结合物在携带黑色素瘤的 C57BL6 小鼠中获得了显着的肿瘤摄取和保留[注射后 1 小时和 4 小时分别为 9.26 +/- 0.83 和 11.31 +/- 1.83% ID/g]。线性 Tc-99m(CO)(3)-pz-肽的细胞内化和肿瘤摄取值均较低。使用强效 (Nle(4),DPhe(7))-α MSH 激动剂进行的受体阻断研究证明了放射性缀合物对 MC1R 的特异性（注射环状和线性放射性缀合物后 4 小时，肿瘤摄取分别减少 74.8% 和 44.5%）。
Early detection of primary melanoma tumors is essential because there is no effective treatment for metastatic melanoma. Several linear and cyclic radiolabeled alpha-melanocyte stimulating hormone (alpha-MSH) analogs have been proposed to target the melanocortin type 1 receptor (MC1R) overexpressed in melanoma. The compact structure of a rhenium-cyclized alpha-MSH analog (Re-CCMSH) significantly enhanced its in vivo tumor uptake and retention. Melanotan II (MT-II), a cyclic lactam analog of alpha-MSH (Ac-Nle-cyclo[Asp-His-DPhe-Arg-Trp-Lys]-NH2]), is a very potent and stable agonist peptide largely used in the characterization of melanocortin receptors. Taking advantage of the superior biological features associated with the MT-II cyclic peptide, we assessed the effect of lactam-based cyclization on the tumor-seeking properties of alpha-MSH analogs by comparing the pharmacokinetics profile of the (99)mTc-labeled cyclic peptide beta Ala-Nle-cyclo[Asp-His-DPhe-Arg-Trp-Lys]-NH2 with that of the linear analog beta Ala-Nle-Asp-His-DPhe-Arg-Trp-Lys-NH2 in melanoma-bearing mice. We have synthesized and coupled the linear and cyclic peptides to a bifunctional chelator containing a pyrazolyl-diamine backbone (pz) through the amino group of beta Ala, and the resulting pz-peptide conjugates were reacted with the fac-[Tc-99m(CO)(3)](+) moiety. The Tc-99m(CO)(3)-labeled conjugates were obtained in high yield, high specific activity, and high radiochemical purity. The cyclic Tc-99m(CO)(3)-labeled conjugate presents a remarkable internalization (87.1% of receptor-bound tracer and 50.5% of total applied activity, after 6 h at 37 degrees C) and cellular retention (only 24.7% released from the cells after 5 h) in murine melanoma B16F1 cells. A significant tumor uptake and retention was obtained in melanoma-bearing C57BL6 mice for the cyclic radioconjugate [9.26 +/- 0.83 and 11.31 +/- 1.83% ID/g at 1 and 4 h after injection, respectively]. The linear Tc-99m(CO)(3)-pz-peptide presented lower values for both cellular internalization and tumor uptake. Receptor blocking studies with the potent (Nle(4),DPhe(7))-alpha MSH agonist demonstrated the specificity of the radioconjugates to MC1R (74.8 and 44.5% reduction of tumor uptake at 4 h after injection for cyclic and linear radioconjugates, respectively).