With current imaging, discriminating tumor progression from treatment effect following immunotherapy or oncolytic virotherapy of glioblastoma (GBM) is challenging. A blood based diagnostic biomarker would therefore be helpful. Axl is a receptor tyrosine kinase that is highly expressed by many cancers including GBM. Axl expression is regulated through enzymatic cleavage of its extracellular domain. The resulting fragment can be detected in serum as soluble Axl (sAxl). sAxl levels can distinguish patients with melanoma, hepatocellular carcinoma, and pancreatic ductal adenocarcinoma from healthy controls. This is a pilot study to determine if sAxl is a candidate biomarker for GBM. The sAxl levels in the serum of 40 healthy volunteers and 20 GBM patients were determined using an enzyme-linked immunosorbent assay (ELISA). Pre- and post- operative sAxl levels were obtained. Volumetric MRI evaluation provided GBM tumor volume metrics. There was no significant difference in the sAxl levels of volunteers (30.16+/-1.88 ng/ml) and GBM patients (30.74+/-1.96 ng/ml) p=0.27. The postoperative sAxl levels were significantly higher than preoperative levels (32.32+/-2.26 ng/ml vs 30.74+/-1.96 ng/ml, p=0.03). We found no correlation between tumor volume and sAxl levels. Axl expression was low or absent in 6 of 11 (55%) patient derived GBM cell lines. Given the wide range of Axl expression by GBM tumors, sAxl may not be a reliable indicator of GBM. However, given the small sample size in this study, a larger study may be considered.

中文翻译：

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评估可溶性 Axl 作为胶质母细胞瘤生物标志物：一项初步研究

利用目前的成像技术，区分胶质母细胞瘤（GBM）免疫疗法或溶瘤病毒疗法后的肿瘤进展与治疗效果具有挑战性。因此，基于血液的诊断生物标志物会有所帮助。 Axl 是一种受体酪氨酸激酶，在包括 GBM 在内的许多癌症中高度表达。 Axl 表达通过其胞外结构域的酶裂解来调节。所得片段可在血清中作为可溶性 Axl (sAxl) 进行检测。 sAxl 水平可以区分黑色素瘤、肝细胞癌和胰腺导管腺癌患者与健康对照。这是一项初步研究，旨在确定 sAxl 是否是 GBM 的候选生物标志物。使用酶联免疫吸附测定 (ELISA) 测定 40 名健康志愿者和 20 名 GBM 患者血清中的 sAxl 水平。获得术前和术后 sAxl 水平。体积 MRI 评估提供了 GBM 肿瘤体积指标。志愿者（30.16+/-1.88 ng/ml）和GBM患者（30.74+/-1.96 ng/ml）的sAxl水平没有显着差异，p=0.27。术后sAxl水平显着高于术前水平（32.32+/-2.26 ng/ml vs 30.74+/-1.96 ng/ml，p=0.03）。我们发现肿瘤体积和 sAxl 水平之间没有相关性。 11 个患者来源的 GBM 细胞系中有 6 个 (55%) 的 Axl 表达较低或不表达。鉴于 GBM 肿瘤中 Axl 表达范围广泛，sAxl 可能不是 GBM 的可靠指标。然而，鉴于本研究的样本量较小，可以考虑进行更大的研究。