Fusion Cell Markers in Circulating Tumor Cells from Patients with High-Grade Ovarian Serous Carcinoma

Abstract

Cancer is primarily a disease in which late diagnosis is linked to poor prognosis, and unfortunately, detection and management are still challenging. Circulating tumor cells (CTCs) are a potential resource to address this disease. Cell fusion, an event discovered recently in CTCs expressing carcinoma and leukocyte markers, occurs when ≥2 cells become a single entity (hybrid cell) after the merging of their plasma membranes. Cell fusion is still poorly understood despite continuous evaluations in in vitro/in vivo studies. Blood samples from 14 patients with high-grade serous ovarian cancer (A.C. Camargo Cancer Center, São Paulo, Brazil) were collected with the aim to analyze the CTCs/hybrid cells and their correlation to clinical outcome. The EDTA collected blood (6 mL) from patients was used to isolate/identify CTCs/hybrid cells by ISET. We used markers with possible correlation with the phenomenon of cell fusion, such as MC1-R, EpCAM and CD45, as well as CEN8 expression by CISH analysis. Samples were collected at three timepoints: baseline, after one month (first follow-up) and after three months (second follow-up) of treatment with olaparib (total sample = 38). Fourteen patients were included and in baseline and first follow-up all patients showed at least one CTC. We found expression of MC1-R, EpCAM and CD45 in cells (hybrid) in at least one of the collection moments. Membrane staining with CD45 was found in CTCs from the other cohort, from the other center, evaluated by the CellSearch® system. The presence of circulating tumor microemboli (CTM) in the first follow-up was associated with a poor recurrence-free survival (RFS) (5.2 vs. 12.2 months; p = 0.005). The MC1-R expression in CTM in the first and second follow-ups was associated with a shorter RFS (p = 0.005). CEN8 expression in CTCs was also related to shorter RFS (p = 0.035). Our study identified a high prevalence of CTCs in ovarian cancer patients, as well as hybrid cells. Both cell subtypes demonstrate utility in prognosis and in the assessment of response to treatment. In addition, the expression of MC1-R and EpCAM in hybrid cells brings new perspectives as a possible marker for this phenomenon in ovarian cancer.

Intrinsic signalling factors associated with cancer cell-cell fusion

“…Beside the importance of physiological cell fusion, there is profound scientific consensus that cell-cell fusion events also occur in human cancers and that disease progression can be related to the formation of tumour hybrids [ 16 , 124 , 150 – 158 ]. However, precise regulatory mechanisms to control e.g.…”

Adopted neoplastic cells and the consequences of their existence

“…Circulating tumor cells (CTC), discovered a century and a half ago [74], are neoplastic cells present in the blood of patients with solid tumors and are thought to include the precursors of metastases [75]. Paradoxically, a fraction or, in some cases, most of CTC released by some non-hematological tumors, such as melanoma, breast, ovarian, and pancreatic cancers, were found to carry CD45, a protein whose expression is normally restricted to bone-marrow derived cells [30,51,[76][77][78]. Hence, these cells (CTC-CD45) were viewed as a persistent artifact until an appeal to give them a closer look [77] revealed that they indeed exist [79] and that their concentration inversely correlates with the survival of patients with pancreatic cancer [30,51].…”

“…The presence of a lymphocyte protein on the cells of non-hematological tumors prompted a hypothesis that CTC-CD45 are hybrids between tumor cells and leukocytes [79]. As a result, these cells have been reported as macrophage-tumor cell fusions [80], circulating hybrid cells [30], or simply hybrids [78]. However, genomic evidence for the hybrid origin of these cells is still unavailable, leaving open other explanations: that CD45 is present due to aberrant gene expression, which is common in cancer, or that cancer cells acquire this protein through trogocytosis [81], a process that enables the intercellular exchange of membrane proteins [82], or by a similar phenomenon termed vampirization [83].…”

Cancer Associated Macrophage-like Cells Are Prognostic for Highly Aggressive Prostate Cancer in Both the Non-Metastatic and Metastatic Settings

“…Independent of cancer etiology, engorged CAMLs (≥50 µm) have shown clinical utility as a prognostic and predictive biomarker for worse outcomes in breast, non-small-cell lung, esophageal, and pancreatic cancers [36,37,[40][41][42]. Further, the presence of CAMLs and their size association to clinical outcomes have been investigated and independently validated by a number of groups [43][44][45][46][47]. While ≥50 µm CAMLs appear to predict decreased survival across multiple solid-tumor types, there is an unexplained phenomenon in which hyper-engorged CAMLs (≥100 µm) appear to predict multi-organ-site metastatic spread and even poorer survival [40,48].…”