Purpose

Radiopharmaceutical therapies targeting fibroblast activation protein (FAP) have shown promising efficacy against many tumor types. But radiopharmaceuticals alone in most cases are insufficient to completely eradicate tumor cells, which can partially be attributed to the protective interplay between tumor cells and cancer-associated fibroblasts (CAFs). The C-X-C chemokine receptor type 4/C-X-C motif chemokine 12 (CXCR4/CXCL12) interaction plays an important role in orchestrating tumor cells and CAFs. We hereby investigated the feasibility and efficacy of [¹⁷⁷Lu]Lu-DOTAGA.(SA.FAPi)₂, a FAP-targeting radiopharmaceutical, in combination with AMD3100, a CXCR4 antagonist, in a preclinical murine model of triple-negative breast cancer (TNBC).

Methods

Public database was first interrogated to reveal the correlation between CAFs’ scores and the prognosis of TNBC patients, as well as the expression levels of FAP and CXCR4 in normal tissues and tumors. In vitro therapeutic efficacy regarding cell proliferation, migration, and colony formation was assessed in BALB/3T3 fibroblasts and 4T1 murine breast cancer cells. In vivo therapeutic efficacy was longitudinally monitored using serial ¹⁸F-FDG, [¹⁸F]AlF-NOTA-FAPI-04, and [⁶⁸Ga]Ga-DOTA-Pentixafor PET/CT scans and validated using tumor sections through immunohistochemical staining of Ki-67, α-SMA, CXCR4, and CXCL12. Intratumoral abundance of myeloid-derived suppressive cells (MDSCs) was analyzed using flow cytometry in accordance with the PET/CT schedules. Treatment toxicity was evaluated by examining major organs including heart, lung, liver, kidney, and spleen.

Results

CAFs’ scores negatively correlated with the survival of TNBC patients (p < 0.05). The expression of CXCR4 and FAP was both significantly higher in tumors than in normal tissues. The combination of [¹⁷⁷Lu]Lu-DOTAGA.(SA.FAPi)₂ and AMD3100 significantly suppressed cell proliferation, migration, and colony formation in cell culture, and exhibited synergistic effects in 4T1 tumor models along with a decreased number of MDSCs. PET/CT imaging revealed lowest tumor accumulation of ¹⁸F-FDG and [¹⁸F]AlF-NOTA-FAPI-04 on day 13 and day 14 after treatment started, both of which gradually increased at later time points. A similar trend was observed in the IHC staining of Ki-67, α-SMA, and CXCL12.

Conclusion

The combination of [¹⁷⁷Lu]Lu-DOTAGA.(SA.FAPi)₂ and AMD3100 is a feasible treatment against TNBC with minimal toxicity in main organs.

中文翻译：

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在三阴性乳腺癌中使用 CXCR4 拮抗剂通过 [177Lu]Lu-DOTAGA.(SA.FAPi)2 靶向 CXCR4/CXCL12 轴

目的

针对成纤维细胞激活蛋白（FAP）的放射性药物疗法已显示出针对多种肿瘤类型的良好疗效。但在大多数情况下，单独使用放射性药物不足以完全根除肿瘤细胞，这部分归因于肿瘤细胞和癌症相关成纤维细胞（CAF）之间的保护性相互作用。 CXC 趋化因子受体 4 型/CXC 基序趋化因子 12 (CXCR4/CXCL12) 相互作用在协调肿瘤细胞和 CAF 中发挥着重要作用。我们特此研究了 [ ¹⁷⁷ Lu]Lu-DOTAGA.(SA.FAPi) ₂（一种 FAP 靶向放射性药物）与 AMD3100（一种 CXCR4 拮抗剂）联合在三阴性乳腺癌临床前小鼠模型中的可行性和有效性（三全国广播公司）。

方法

首先通过公共数据库揭示了 CAF 评分与 TNBC 患者预后之间的相关性，以及正常组织和肿瘤中 FAP 和 CXCR4 的表达水平。在 BALB/3T3 成纤维细胞和 4T1 鼠乳腺癌细胞中评估了细胞增殖、迁移和集落形成的体外治疗效果。使用连续¹⁸ F-FDG、[ ¹⁸ F]AlF-NOTA-FAPI-04 和 [ ⁶⁸ Ga]Ga-DOTA-Pentixafor PET/CT 扫描纵向监测体内治疗效果，并通过 Ki 的免疫组织化学染色使用肿瘤切片进行验证-67、α-SMA、CXCR4 和 CXCL12。根据 PET/CT 方案，使用流式细胞术分析瘤内骨髓源性抑制细胞 (MDSC) 的丰度。通过检查心脏、肺、肝、肾和脾等主要器官来评估治疗毒性。

结果

CAF 评分与 TNBC 患者的生存率呈负相关（p  < 0.05）。 CXCR4和FAP在肿瘤中的表达均显着高于正常组织。 [ ¹⁷⁷ Lu]Lu-DOTAGA.(SA.FAPi) ₂和 AMD3100的组合显着抑制细胞培养中的细胞增殖、迁移和集落形成，并在 4T1 肿瘤模型中表现出协同效应，同时减少 MDSC 数量。 PET/CT成像显示治疗开始后第13天和第14天¹⁸ F-FDG和[ ¹⁸ F]AlF-NOTA-FAPI-04的肿瘤积累最低，两者在以后的时间点逐渐增加。 Ki-67、α-SMA 和 CXCL12 的 IHC 染色也观察到类似的趋势。

结论

^{[ 177} Lu]Lu-DOTAGA.(SA.FAPi) ₂和 AMD3100的组合是针对 TNBC 的可行治疗方法，且对主要器官的毒性最小。