Medical Isotopes Research Center, Peking University, Beijing, China Department of Radiation Medicine, School of Basic Medical Sciences, Peking University, Beijing, China; and.
Department of Nuclear Medicine, Peking Union Medical College Hospital, Beijing, China.
J Nucl Med. 2014 Jun;55(6):1002-7. doi: 10.2967/jnumed.114.137000. Epub 2014 Apr 14.
Previous in vitro studies demonstrated that treating tumors expressing both epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 with trastuzumab resulted in increased EGFR homodimerization and subsequent rapid downregulation of EGFR. We investigated whether molecular imaging using near-infrared fluorescence (NIRF) imaging and PET probes could sensitively detect trastuzumab-induced EGFR downregulation in vivo.
The F(ab')2 antibody fragment PaniF(ab')2 was generated by digesting the anti-EGFR monoclonal antibody panitumumab. PaniF(ab')2 was labeled with either a NIRF dye or (68)Ga, and optical imaging and small-animal PET imaging of Dye-PaniF(ab')2 and (68)Ga-PaniF(ab')2, respectively, were performed in HT-29 tumor-bearing nude mice treated with trastuzumab or untreated control.
Longitudinal NIRF imaging studies revealed significantly reduced tumor uptake of Dye-PaniF(ab')2 on days 5 and 7 in trastuzumab-treated HT-29 tumors, compared with control. Western blotting confirmed the downregulation of EGFR after treatment with trastuzumab. Small-animal PET on day 5 after trastuzumab treatment also demonstrated decreased (68)Ga-PaniF(ab')2 uptake in trastuzumab-treated HT-29 tumors. The tumor uptake value of (68)Ga-PaniF(ab')2 obtained from PET imaging had an excellent linear correlation with the uptake value measured using biodistribution.
The downregulation of EGFR induced by trastuzumab treatment could be detected noninvasively using optical and PET imaging. This molecular imaging strategy could provide a dynamic readout of changes in the tumor signaling and may facilitate the noninvasive monitoring of the early tumor response to drug treatment.
先前的体外研究表明，用曲妥珠单抗治疗同时表达表皮生长因子受体（EGFR）和人表皮生长因子受体 2 的肿瘤会导致 EGFR 同源二聚化增加，并随后迅速下调 EGFR。我们研究了使用近红外荧光（NIRF）成像和 PET 探针的分子成像是否可以敏感地检测体内曲妥珠单抗诱导的 EGFR 下调。
通过消化抗 EGFR 单克隆抗体 panitumumab 生成 F(ab')2 抗体片段 PaniF(ab')2。用 NIRF 染料或 (68)Ga 标记 PaniF(ab')2，并用 Dye-PaniF(ab')2 和 (68)Ga-PaniF(ab')2 分别进行光学成像和小动物 PET 成像，在接受或未接受曲妥珠单抗治疗的 HT-29 荷瘤裸鼠中进行。
纵向 NIRF 成像研究显示，与对照组相比，曲妥珠单抗治疗的 HT-29 肿瘤在第 5 天和第 7 天 Dye-PaniF(ab')2 的肿瘤摄取明显减少。Western blot 证实曲妥珠单抗治疗后 EGFR 下调。曲妥珠单抗治疗后第 5 天的小动物 PET 也显示曲妥珠单抗治疗的 HT-29 肿瘤中 (68)Ga-PaniF(ab')2 的摄取减少。从 PET 成像获得的 (68)Ga-PaniF(ab')2 肿瘤摄取值与生物分布测量得到的摄取值具有极好的线性相关性。
曲妥珠单抗治疗诱导的 EGFR 下调可以通过光学和 PET 成像进行非侵入性检测。这种分子成像策略可以提供肿瘤信号变化的动态读数，并可能有助于非侵入性监测药物治疗早期肿瘤的反应。
