Translational Research Imaging Center, Institute of Clinical Radiology, Medical Faculty, University of Muenster and University Hospital Muenster, Muenster, Germany.
Institute for Diagnostic and Interventional Radiology, University Hospital Cologne, Cologne, Germany.
Mol Imaging Biol. 2020 Feb;22(1):66-72. doi: 10.1007/s11307-019-01370-1.
Tumor development and metastasis are dependent on tumor infiltrating immune cells which form a characteristic tumor microenvironment (TME). Activated monocytes secrete the protein heterodimer S100A8/A9 promoting TME formation. Monocyte-dependent proteases facilitate local tumor cell invasion by degradation of the extracellular matrix. We aimed for target specific in vivo imaging of S100A8 and proteases to provide differentiating biomarkers for local tumor growth and metastatic potential.
Murine breast cancer cells of the 4T1 model with graduated metastatic potential (4T1 and 4T07: both hematogenous metastasis > 168FAR: lymph-node metastasis > 67NR: no metastasis) were orthotopically implanted into female BALB/c mice. At 4 mm size, tumors were investigated by injecting the protease-specific probe ProSense 750EX (PerkinElmer, 4T1 n = 7, 4T07 n = 10, 168FAR n = 16, 67NR n = 15) and anti-S100A8-Cy5.5 (n = 6 each) and performing fluorescence reflectance imaging at 0 and 24 h after injection. In vivo imaging was validated with immunohistochemistry.
At 24 h, S100A8-specific signals in 4T1 and 4T07 were significantly higher (1714.05/1683.45 AU) as compared to 168FAR and 67NR (174.85/167.95 AU, p = 0.0012/p = 0.0003), reflecting the capability of hematogenous spread. Protease-specific signals were significantly higher in 4T1 and 4T07 (348.01/409.93 AU) as compared to 168FAR (214.91 AU) and 67NR (129.78 AU p < 0.0001 each), reflecting local vessel invasion and tumor cell shedding. Immunohistology supported the in vivo imaging results.
Non-invasive in vivo imaging of S100A8 and monocytic proteases allows for differentiation of the tumors' local invasive and systemic metastatic potential in reflecting the TME formation. While proteases augment local tumor cell invasion, solid metastases seem to be dependent on a pro-tumoral microenvironment.
肿瘤的发生和转移依赖于浸润肿瘤的免疫细胞，这些细胞形成了特征性的肿瘤微环境（TME）。活化的单核细胞分泌蛋白异二聚体 S100A8/A9 促进 TME 的形成。单核细胞依赖性蛋白酶通过降解细胞外基质促进局部肿瘤细胞的侵袭。我们的目的是对 S100A8 和蛋白酶进行特异性体内成像，为局部肿瘤生长和转移潜能提供有区别的生物标志物。
具有不同转移潜能的 4T1 模型的鼠乳腺癌细胞（4T1 和 4T07：均为血源性转移>168FAR：淋巴结转移>67NR：无转移）被原位植入雌性 BALB/c 小鼠体内。在 4mm 大小的时候，通过注射蛋白酶特异性探针 ProSense 750EX（PerkinElmer，4T1 n=7，4T07 n=10，168FAR n=16，67NR n=15）和抗 S100A8-Cy5.5（n=6 个），并在注射后 0 和 24 小时进行荧光反射成像来研究肿瘤。体内成像用免疫组织化学进行验证。
在 24 小时时，与 168FAR 和 67NR 相比（174.85/167.95 AU，p=0.0012/p=0.0003），4T1 和 4T07 中的 S100A8 特异性信号明显更高（1714.05/1683.45 AU），反映了血源性播散的能力。与 168FAR（214.91 AU）和 67NR（129.78 AU，p<0.0001 各）相比，4T1 和 4T07 中的蛋白酶特异性信号明显更高（348.01/409.93 AU），反映了局部血管侵袭和肿瘤细胞脱落。免疫组织化学支持体内成像结果。
S100A8 和单核细胞蛋白酶的非侵入性体内成像允许区分肿瘤的局部侵袭和全身转移潜能，反映了 TME 的形成。虽然蛋白酶增强了局部肿瘤细胞的侵袭，但实体转移似乎依赖于促肿瘤微环境。
