Department of Nuclear Medicine, Renji Hospital, School of Medicine, Shanghai Jiaotong University, 160 Pujian RD, Shanghai, 200127, China.
Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China.
Mol Imaging Biol. 2020 Jun;22(3):772-779. doi: 10.1007/s11307-019-01416-4.
There is currently no effective noninvasive method for accurate molecular typing of triple negative breast cancer (TNBC) except needle biopsy. Glucoregulated Protein 78 (GRP78) is overexpressed in TNBC cells and tumors which closely related to the invasion, metastasis, and drug resistance of cancer. Meanwhile, it has been verified that VAP peptide bind specifically to GRP78 in vitro and in vivo. In this study, we constructed a GRP78-targeted molecular probe Ga-68-radiolabeled DOTA-VAP conjugate ([Ga]DOTA-VAP) based on VAP peptide, and evaluated its potential to distinguish TNBC from non-TNBC tumors.
DOTA-VAP was synthesized and then radiolabeled with Ga-68 to obtain [Ga]DOTA-VAP. The expression of GRP78 in TNBC MDA-MB-231 and non-TNBC MCF-7 cells was validated by Western Blot, and cell binding or uptake experiments with both [Ga]DOTA-VAP and 2-deoxy-2-[F]fluoro-D-glucose ([F]FDG) were also performed. Biodistribution analysis and positron emission tomography (PET) imaging of [Ga]DOTA-VAP were carried out in subcutaneous MDA-MB-231 and MCF-7 human breast cancer tumor models with [F]FDG PET imaging as comparison.
[Ga]DOTA-VAP was prepared with high radiochemical purity which showed excellent stability in vitro. The MDA-MB-231 tumors were clearly visualized by [Ga]DOTA-VAP PET imaging with a low background, except for the relatively high liver uptake. Cells and tumors of MDA-MB-231 could be distinguished from MCF-7 by [Ga]DOTA-VAP instead of [F]FDG. Biodistribution results were consistent with the imaging results. The blocking study with excess cold peptide showed significantly reduced tumor uptake, which indicated the specificity of [Ga]DOTA-VAP targeting MDA-MB-231 tumors in vivo.
GRP78-targeted PET imaging with [Ga]DOTA-VAP provided an effective approach for the noninvasive accurate classification of TNBC from other breast cancer subtypes comparing with [F]FDG. GRP78 may be a potential target for the diagnosis and treatment of TNBC. For clinical transformation, efforts should be made to overcome deficiencies of [Ga]DOTA-VAP such as relative high uptake in normal tissues.
除了针吸活检外，目前尚无有效的非侵入性方法来准确对三阴性乳腺癌（TNBC）进行分子分型。葡萄糖调节蛋白 78（GRP78）在 TNBC 细胞和肿瘤中过度表达，与癌症的侵袭、转移和耐药性密切相关。同时，已经验证 VAP 肽在体外和体内特异性结合 GRP78。本研究基于 VAP 肽构建了一种 GRP78 靶向分子探针 Ga-68 放射性标记的 DOTA-VAP 缀合物（[Ga]DOTA-VAP），并评估了其将 TNBC 与非 TNBC 肿瘤区分开的潜力。
合成 DOTA-VAP，然后用 Ga-68 放射性标记以获得[Ga]DOTA-VAP。通过 Western blot 验证 TNBC MDA-MB-231 和非 TNBC MCF-7 细胞中 GRP78 的表达，并进行了[Ga]DOTA-VAP 和 2-脱氧-2-[F]氟-D-葡萄糖（[F]FDG）的细胞结合或摄取实验。用[F]FDG PET 成像作为比较，在皮下 MDA-MB-231 和 MCF-7 人乳腺癌肿瘤模型中进行了[Ga]DOTA-VAP 的生物分布分析和正电子发射断层扫描（PET）成像。
[Ga]DOTA-VAP 具有很高的放射化学纯度，在体外表现出优异的稳定性。除了相对较高的肝脏摄取外，[Ga]DOTA-VAP PET 成像可以清晰地显示 MDA-MB-231 肿瘤，背景较低。与[F]FDG 相比，[Ga]DOTA-VAP 可以区分 MDA-MB-231 细胞和肿瘤与 MCF-7。生物分布结果与成像结果一致。用过量冷肽进行阻断研究后，肿瘤摄取明显减少，这表明[Ga]DOTA-VAP 在体内对 MDA-MB-231 肿瘤的靶向性特异性。
与[F]FDG 相比，用[Ga]DOTA-VAP 进行 GRP78 靶向 PET 成像为从其他乳腺癌亚型无创准确分类 TNBC 提供了一种有效方法。GRP78 可能是 TNBC 诊断和治疗的潜在靶点。为了实现临床转化，应努力克服[Ga]DOTA-VAP 的一些缺陷，如正常组织摄取相对较高。
