Introduction: Various subtypes of circulating cancerassociated cells in the blood are described. A unique circulating, large, and polymorphonuclear cell with a dual epithelial and myeloid phenotype has been suggested as a tumor-macrophage fusion cell (TMF). The goal of the study was to identify the impact of distinct TMFs on survival among patients with NSCLC.Methods: In this prospective trial, 7.5 mL of whole blood sample was collected. After microfilter enrichment, immunofluorescent staining was performed, identifying TMFs as greater than or equal to 30 mm in size and dual epithelial (cytokeratin 8, 18, or 19-, or epithelial cell adhesion molecule-positive) and myeloid-or macrophage-positive (CD14or CD45-positive) cells with at least one 4 0 ,6-diamidino-2phenylindoleþ nucleus.Results: Circulating TMFs were identified in 88 of 115 patients (76.5%) with NSCLC (mean 3.052 [SEM ± 0.306]; median 2 [range 0-17]) but were rare in long-term smokers without cancer (6 of 87 [6.9%]; 0.081 [±0.034]; 0 [0-2]), and absent in 20 healthy controls. Comparing the presence of TMFs in patients with NSCLC versus smokers without cancer, specificity was 93.1% (95% confidence interval: 85.6-97.4%) and sensitivity 76.5% (95% confidence interval: 67.7%-83.9%). TMF counts correlated with American Joint Committee on Cancer tumor stages. More importantly, more than one TMF and giant TMFs sizes greater than or equal to 50 mm were associated with statistically significantly shorter overall and cancer-specific disease-free (p < 0.05) survival after curative resection for stage I to IIIA. Giant TMFs greater than or equal to 50 mm size were an independent survival predictor by multivariate analysis.Conclusions: Circulating, in particular, giant TMFs are associated with aggressive clinical behavior in surgically treated patients with NSCLC. The biological role of unique TMFs will need to be further investigated, as these may have a potential impact on immune responses toward cancer.Published by Elsevier Inc. on behalf of International Association for the Study of Lung Cancer.
Although molecular mechanisms driving tumor progression have been extensively studied, the biological nature of the various populations of circulating tumor cells (CTCs) within the blood is still not well understood. Tumor cell fusion with immune cells is a longstanding hypothesis that has caught more attention in recent times. Specifically, fusion of tumor cells with macrophages might lead to the development of metastasis by acquiring features such as genetic and epigenetic heterogeneity, chemotherapeutic resistance, and immune tolerance. In addition to the traditional FDA-approved definition of a CTC (CD45-, EpCAM+, cytokeratins 8+, 18+ or 19+, with a DAPI+ nucleus), an additional circulating cell population has been identified as being potential fusions cells, characterized by distinct, large, polymorphonuclear cancer-associated cells with a dual epithelial and macrophage/myeloid phenotype. Artificial fusion of tumor cells with macrophages leads to migratory, invasive, and metastatic phenotypes. Further studies might investigate whether these have a potential impact on the immune response towards the cancer. In this review, the background, evidence, and potential relevance of tumor cell fusions with macrophages is discussed, along with the potential role of intercellular connections in their formation. Such fusion cells could be a key component in cancer metastasis, and therefore, evolve as a diagnostic and therapeutic target in cancer precision medicine.
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