Evaluating soluble Axl as a biomarker for glioblastoma: A pilot study

• Published in: PloS one Vol. 19; no. 7; p. e0301739
• Main Authors: Raymond, Daniel, Fukui, Melanie, Zwernik, Samuel, Kassam, Amin, Rovin, Richard, Akhtar, Parvez
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 05.07.2024; Public Library of Science (PLoS)
• Subjects: Adenocarcinoma; Adult; Aged; Angiogenesis; Antibodies; Axl protein; Axl Receptor Tyrosine Kinase; Biology and Life Sciences; Biomarkers; Biomarkers, Tumor - blood; Biomarkers, Tumor - metabolism; Brain cancer; Brain Neoplasms - blood; Brain Neoplasms - metabolism; Brain Neoplasms - pathology; Breast cancer; Cancer; Case-Control Studies; Cell culture; Chemotherapy; Colorectal cancer; Datasets; Development and progression; Enzyme-Linked Immunosorbent Assay; Enzymes; Female; Glioblastoma; Glioblastoma - metabolism; Glioblastoma multiforme; Glioma; Hepatocellular carcinoma; Humans; Immunotherapy; Infrared imaging systems; Kidney cancer; Kinases; Ligands; Liver cancer; Magnetic Resonance Imaging - methods; Male; Medicine and Health Sciences; Melanoma; Middle Aged; Oncolysis; Pancreatic cancer; Pancreatic carcinoma; Patients; Pilot Projects; Prostate cancer; Protein-tyrosine kinase receptors; Proto-Oncogene Proteins - blood; Proto-Oncogene Proteins - metabolism; Receptor Protein-Tyrosine Kinases - metabolism; Review boards; Stem cells; Surgery; Tumors; Tyrosine
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0301739

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 the 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.