Department of Radioactive Materials, Instituto Nacional de Investigaciones Nucleares, Ocoyoacac 52750, Mexico.
Cátedras, CONACyT, Instituto Nacional de Investigaciones Nucleares, Ocoyoacac 52750, Mexico.
Int J Mol Sci. 2023 Aug 3;24(15):12382. doi: 10.3390/ijms241512382.
Current cancer therapies focus on reducing immunosuppression and remodeling the tumor microenvironment to inhibit metastasis, cancer progression, and therapeutic resistance. Programmed death receptor 1 (PD-1) is expressed on immune T cells and is one of the so-called checkpoint proteins that can suppress or stop the immune response. To evade the immune system, cancer cells overexpress a PD-1 inhibitor protein (PD-L1), which binds to the surface of T cells to activate signaling pathways that induce immune suppression. This research aimed to synthesize PD-L1 inhibitory peptides (PD-L1-i) labeled with lutetium-177 (Lu-DOTA-PD-L1-i) and actinium-225 (Ac-HEHA-PD-L1-i) and to preclinically evaluate their potential as radiopharmaceuticals for targeted radiotherapy at the tumor microenvironment level. Using PD-L1-i peptide as starting material, conjugation with HEHA-benzene-SCN and DOTA-benzene-SCN was performed to yield DOTA-PD-L1-i and HEHA-PD-L1-I, which were characterized by FT-IR, UV-vis spectroscopy, and HPLC. After labeling the conjugates with Ac and Lu, cellular uptake in HCC827 cancer cells (PD-L1 positive), conjugate specificity evaluation by immunofluorescence, radiotracer effect on cell viability, biodistribution, biokinetics, and assessment of radiation absorbed dose in mice with in duced lung micrometastases were performed. Ac-HEHA-PD-L1-i and Lu-DOTA-PD-L1-i, obtained with radiochemical purities of 95 ± 3% and 98.5 ± 0.5%, respectively, showed in vitro and in vivo specific recognition for the PD-L1 protein in lung cancer cells and high uptake in HCC287 lung micrometastases (>30% ID). The biokinetic profiles of Lu-DOTA-PD-L1-i and Ac-DOTA-PD-L1-i showed rapid blood clearance with renal and hepatobiliary elimination and no accumulation in normal tissues. Ac-DOTA-PD-L1-i produced a radiation dose of 5.15 mGy/MBq to lung micrometastases. In the case of Lu-DOTA-PD-L1-i, the radiation dose delivered to the lung micrometastases was ten times (43 mGy/MBq) that delivered to the kidneys (4.20 mGy/MBq) and fifty times that delivered to the liver (0.85 mGy/MBq). Therefore, the radiotherapeutic PD-L1-i ligands of Ac and Lu developed in this research could be combined with immunotherapy to enhance the therapeutic effect in various types of cancer.
当前的癌症疗法侧重于减少免疫抑制并重塑肿瘤微环境，以抑制转移、癌症进展和治疗抵抗。程序性死亡受体 1 (PD-1) 表达在免疫 T 细胞上，是所谓的检查点蛋白之一，可抑制或停止免疫反应。为了逃避免疫系统，癌细胞过度表达 PD-1 抑制剂蛋白 (PD-L1)，该蛋白与 T 细胞表面结合，激活诱导免疫抑制的信号通路。这项研究旨在合成标记镥-177 (Lu-DOTA-PD-L1-i) 和锕-225 (Ac-HEHA-PD-L1-i) 的 PD-L1 抑制肽 (PD-L1-i)，并对其作为针对肿瘤微环境水平的靶向放射治疗的放射性药物的潜在价值进行临床前评估。使用 PD-L1-i 肽作为起始材料，与 HEHA-苯-SCN 和 DOTA-苯-SCN 进行缀合，得到 DOTA-PD-L1-i 和 HEHA-PD-L1-i，并通过傅里叶变换红外光谱 (FT-IR)、紫外可见光谱和高效液相色谱 (HPLC) 进行表征。用 Ac 和 Lu 标记缀合物后，在 HCC827 癌细胞（PD-L1 阳性）中进行细胞摄取，通过免疫荧光评估结合物的特异性，研究放射性示踪剂对细胞活力的影响，进行生物分布、生物动力学以及在诱导的肺微转移小鼠中评估辐射吸收剂量。分别获得放射性化学纯度为 95±3%和 98.5±0.5%的 Ac-HEHA-PD-L1-i 和 Lu-DOTA-PD-L1-i，在体外和体内均特异性识别肺癌细胞中的 PD-L1 蛋白，并在 HCC287 肺微转移灶中摄取率高 (>30% ID)。Lu-DOTA-PD-L1-i 和 Ac-DOTA-PD-L1-i 的生物动力学谱显示快速血液清除，具有肾和肝胆消除途径，且无正常组织蓄积。Ac-DOTA-PD-L1-i 对肺微转移灶的辐射剂量为 5.15 mGy/MBq。对于 Lu-DOTA-PD-L1-i，肺微转移灶的辐射剂量是肾脏的十倍 (43 mGy/MBq)，是肝脏的五十倍 (0.85 mGy/MBq)。因此，本研究中开发的 Ac 和 Lu 的放射性治疗性 PD-L1-i 配体可与免疫疗法结合，以增强各种类型癌症的治疗效果。
