Purpose

Current clinical measurements for tumor treatment efficiency rely often on changes in tumor volume measured as shrinkage by CT or MRI, which become apparent after multiple lines of treatment and pose a physical and psychological burden on the patient. Detection of therapy-induced cell death in the tumor can be a fast measure for treatment efficiency. However, there are no reliable clinical tools for detection of tumor necrosis. Previously, we studied the necrosis avidity of cyanine-based fluorescent dyes, which suffered long circulation times before tumor necrosis could be imaged due to low hydrophilicity. We now present the application of radiolabeled 800CW, a commercially available cyanine with high hydrophilicity, to image tumor necrosis in a mouse model.

Procedures

We conjugated 800CW to DOTA via a PEG linker, for labeling with single-photon emission-computed tomography isotope indium-111, yielding [¹¹¹In]In-DOTA-PEG₄-800CW. We then investigated specific [¹¹¹In]In-DOTA-PEG₄-800CW uptake by dead cells in vitro, using both fluorescence and radioactivity as detection modalities. Finally, we investigated [¹¹¹In]In-DOTA-PEG₄-800CW uptake into necrotic tumor regions of a 4T1 breast tumor model in mice.

Results

We successfully prepared a precursor and developed a reliable procedure for labeling 800CW with indium-111. We detected specific [¹¹¹In]In-DOTA-PEG₄-800CW uptake by dead cells, using both fluorescence and radioactivity. Albeit with a tumor uptake of only 0.37%ID/g at 6 h post injection, we were able to image tumor necrosis with a tumor to background ratio of 7:4. Fluorescence and radioactivity in cryosections from the dissected tumors were colocalized with tumor necrosis, confirmed by TUNEL staining.

Conclusions

[¹¹¹In]In-DOTA-PEG₄-800CW can be used to image tumor necrosis in vitro and in vivo. Further research will elucidate the application of [¹¹¹In]In-DOTA-PEG₄-800CW or other radiolabeled hydrophilic cyanines for the detection of necrosis caused by chemotherapy or other anti-cancer therapies. This can provide valuable prognostic information in treatment of solid tumors.

中文翻译：

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对 Indium-111 标记的 800CW 作为坏死狂热对比剂的体内评价。

目的

当前对肿瘤治疗效率的临床测量通常依赖于通过 CT 或 MRI 测量的肿瘤体积变化，这些变化在多线治疗后变得明显，并给患者带来身心负担。检测肿瘤中治疗诱导的细胞死亡可以快速衡量治疗效率。然而，没有可靠的临床工具来检测肿瘤坏死。之前，我们研究了花青基荧光染料的坏死亲合力，由于亲水性低，在对肿瘤坏死进行成像之前，这种染料的循环时间很长。我们现在介绍放射性标记的 800CW（一种具有高亲水性的市售花青）在小鼠模型中对肿瘤坏死进行成像的应用。

程序

我们通过PEG 接头将800CW 与 DOTA 结合，用于用单光子发射计算机断层扫描同位素铟 111 进行标记，产生 [ ¹¹¹ In] In-DOTA-PEG ₄ -800CW。然后，我们使用荧光和放射性作为检测方式，研究了体外死细胞对 [ ¹¹¹ In] In-DOTA-PEG ₄ -800CW 的吸收。最后，我们研究了 [ ¹¹¹ In] In-DOTA-PEG ₄ -800CW 对小鼠 4T1 乳腺肿瘤模型坏死肿瘤区域的摄取。

结果

我们成功制备了一种前体，并开发了一种可靠的程序，用铟 111 标记 800CW。我们使用荧光和放射性检测到死细胞对[ ¹¹¹ In] In-DOTA-PEG ₄ -800CW 的吸收。尽管在注射后 6 小时肿瘤摄取仅为 0.37%ID/g，但我们能够以 7:4 的肿瘤与背景比对肿瘤坏死进行成像。通过 TUNEL 染色证实，来自解剖肿瘤的冷冻切片中的荧光和放射性与肿瘤坏死共存。

结论

[ ¹¹¹ In]In-DOTA-PEG ₄ -800CW 可用于在体外和体内对肿瘤坏死进行成像。进一步的研究将阐明 [ ¹¹¹ In] In-DOTA-PEG ₄ -800CW 或其他放射性标记的亲水花青在检测由化学疗法或其他抗癌疗法引起的坏死中的应用。这可以为实体瘤的治疗提供有价值的预后信息。