Objective

Radioimmunotherapy (RIT) is a systemic therapy currently used in the treatment of patients with lymphoma. RIT complexes consist of a targeting molecule, commonly an antibody, radionuclide chelates and a linker which can be a nanoparticle platform. Nanoparticles facilitate the attachment of multiple radionuclides and targeting groups to a single complex. Here the target affinity, duration of target association and inhibition of colony formation of Cetuximab-resistant tumour cells with Cetuximab-targeted [¹⁷⁷Lu]-AuNPs were investigated. Dose distribution in xenografts derived from EGFR-overexpressing cells was also determined.

Methods

Cetuximab-targeted [¹⁷⁷Lu]-AuNPs were generated by functionalising 15nm AuNPs with the chelator DOTA and Cetuximab and radiolabelling with ¹⁷⁷LuCl₃. K_Dis, a measure of affinity, was determined by competitive binding to EGFR expressing cells. Radio-sensitivity was determined in EGFR expressing tumour cells including the Cetuximab resistant cell line HCT116 using a colony formation assay. Dose distribution was measured in sections from xenografts grown in nude mice using autoradiography.

Results

K_Dis for the complex binding to EGFR on MDA-MB-468 cells was 20 nM. Loss of cell associated [¹⁷⁷Lu] activity was biphasic with loss of about 50% of activity in about 4 h. Remaining activity dissociated over a period of about 4 days. HCT8 and MDA-MB-468, but not HCT116 cells were sensitive to the growth inhibitory effect of Cetuximab. However, treatment with Cetuximab-targeted [¹⁷⁷Lu]-AuNPs inhibited colony formation in all 3 cell lines. Dose distribution across sections from xenografts was found to demonstrate a co-efficient of variation of 15%.

Conclusion

Cetuximab-targeted [¹⁷⁷Lu]-AuNPs demonstrate high affinity for EGFR and could be an effective treatment for Cetuximab-resistant colorectal cancer cells. A strategy involving pre-treatment with receptor targeted[¹⁷⁷Lu] to improve RIT therapeutic ratios has the potential to enhance clinical outcomes.

中文翻译：

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[177Lu] 金纳米粒子的 EGFR 靶向结直肠和乳腺肿瘤细胞：西妥昔单抗耐药细胞的亲和力、结合持续时间和生长抑制

客观的

放射免疫疗法 (RIT) 是目前用于治疗淋巴瘤患者的全身疗法。RIT 复合物由靶向分子（通常是抗体）、放射性核素螯合物和可以是纳米颗粒平台的接头组成。纳米粒子有助于将多种放射性核素和靶向基团连接到单个复合物上。这里研究了靶亲和力、靶结合的持续时间和西妥昔单抗靶向的 [ ¹⁷⁷ Lu]-AuNPs对西妥昔单抗耐药肿瘤细胞集落形成的抑制。还确定了源自 EGFR 过表达细胞的异种移植物中的剂量分布。

方法

西妥昔单抗靶向的 [ ¹⁷⁷ Lu]-AuNP 是通过用螯合剂 DOTA 和西妥昔单抗功能化 15nm AuNP 并用¹⁷⁷ LuCl _{3 进行}放射性标记而产生的。K _Dis是亲和力的量度，通过与EGFR表达细胞的竞争性结合来确定。使用集落形成试验在表达 EGFR 的肿瘤细胞（包括西妥昔单抗抗性细胞系 HCT116）中确定放射敏感性。使用放射自显影法在裸鼠中生长的异种移植物切片中测量剂量分布。

结果

MDA-MB-468 细胞上与 EGFR 结合的复合物的K _Dis为 20 nM。细胞相关 [ ¹⁷⁷ Lu] 活性的丧失是双相的，在约 4 小时内丧失约 50% 的活性。剩余的活性在大约 4 天的时间内解离。HCT8 和 MDA-MB-468，但不是 HCT116 细胞对西妥昔单抗的生长抑制作用敏感。然而，用西妥昔单抗靶向的 [ ¹⁷⁷ Lu]-AuNPs 处理抑制了所有 3 种细胞系中的集落形成。发现来自异种移植物的切片的剂量分布证明变异系数为 15%。

结论

西妥昔单抗靶向的 [ ¹⁷⁷ Lu]-AuNP 显示出对 EGFR 的高亲和力，可能是对西妥昔单抗耐药的结直肠癌细胞的有效治疗方法。一种涉及用靶向受体进行预处理的策略 [ ¹⁷⁷ Lu]，以提高 RIT 治疗率，有可能提高临床结果。