Chen Yuehua, Su Yuan, Pang Xufeng, Song Xiaoxia, Zhao Wanjun, Yu Mingming
Department of Nuclear Medicine, The Affiliated Hospital of Qingdao University, Qingdao, China.
Front Oncol. 2022 Apr 21;12:869260. doi: 10.3389/fonc.2022.869260. eCollection 2022.
To prepare technetium-99m (Tc)-labeled pH (low) insertion peptide variant 7 [pHLIP (Var7)] and carry out small-animal single-photon-emission computed tomography (SPECT)/computed tomography (CT) imaging of tumor-bearing nude mice to study its value in the early diagnosis of triple-negative breast cancer (TNBC).
The pHLIP (Var7) sequence was synthesized solid-phase peptide synthesis. Four amino acids, Gly-(D)-Ala-Gly-Gly, were attached to the N-terminus of pHLIP (Var7) to form a strong chelating group containing an N4 structure. The peptide was labeled with Tc using a direct labeling method. We determined the binding fraction of Tc-pHLIP (Var7) to MDA-MB-231 cells. Serial biodistribution studies and small-animal SPECT/CT imaging in MDA-MB-231 TNBC-bearing mice were performed using Tc-pHLIP (Var7).
The radiochemical yield and purity of Tc-pHLIP (Var7) were 99.49 ± 0.17% and 99.63 ± 0.44%, respectively. The radiochemical purity was still more than 96% after 24 h in serum. The binding fraction of Tc-pHLIP (Var7) to MDA-MB-231 cells continuously increased in an acidic environment and was significantly higher than the cell-binding fraction (P < 0.01) at pH = 7.4 and the cell-binding fraction (P < 0.01) of Tc-kVar7 at different pH values (pH = 6.0, 6.5, 7.0 and 7.4) at each time point (P < 0.01). The distribution of Tc-pHLIP (Var7) in tumors at each time point was significantly greater than that of Tc-kVar7 (P < 0.01). SPECT/CT imaging was largely consistent with the biodistribution results; the tumor was clearly imaged at each time point after injection of Tc-pHLIP (Var7) but could not be imaged after injection of Tc-kVar7.
Tc-pHLIP (Var7) showed a high radiochemical yield and stability and was highly concentrated in tumor tissues. Although there was strong radioactive background in the abdomen of tumor-bearing nude mice, it did not hinder early diagnosis of TNBC.
制备99m锝（Tc）标记的pH（低）插入肽变体7 [pHLIP（Var7）]，并对荷瘤裸鼠进行小动物单光子发射计算机断层扫描（SPECT）/计算机断层扫描（CT）成像，以研究其在三阴性乳腺癌（TNBC）早期诊断中的价值。
采用固相肽合成法合成pHLIP（Var7）序列。在pHLIP（Var7）的N端连接4个氨基酸Gly-（D）-Ala-Gly-Gly，形成含N4结构的强螯合基团。采用直接标记法用Tc标记该肽。测定了Tc-pHLIP（Var7）与MDA-MB-231细胞的结合率。使用Tc-pHLIP（Var7）对荷MDA-MB-231 TNBC的小鼠进行系列生物分布研究和小动物SPECT/CT成像。
Tc-pHLIP（Var7）的放射化学产率和纯度分别为99.49±0.17%和99.63±0.44%。在血清中放置24 h后，放射化学纯度仍高于96%。在酸性环境中，Tc-pHLIP（Var7）与MDA-MB-231细胞的结合率持续升高，且在pH = 7.4时显著高于细胞结合率（P < 0.01），在每个时间点，其与不同pH值（pH = 6.0、6.5、7.0和7.4）下Tc-kVar7的细胞结合率相比也显著升高（P < 0.01）。各时间点Tc-pHLIP（Var7）在肿瘤中的分布均显著高于Tc-kVar7（P < 0.01）。SPECT/CT成像结果与生物分布结果基本一致；注射Tc-pHLIP（Var7）后各时间点肿瘤均清晰显影，而注射Tc-kVar7后肿瘤未显影。
Tc-pHLIP（Var7）具有较高的放射化学产率和稳定性，且在肿瘤组织中高度浓聚。虽然荷瘤裸鼠腹部有较强的放射性本底，但不影响TNBC的早期诊断。
