Folate Receptor-Positive Circulating Tumor Cells as a Novel Diagnostic Biomarker in Non-Small Cell Lung Cancer

Abstract

The study aims to determine the efficacy and feasibility of a novel folate receptor (FR)-based circulating tumor cell (CTC) detection method in the diagnosis of non-small cell lung cancer (NSCLC). CTCs were collected from 3 ml of blood based on negative enrichment by immunomagnetic beads and then labeled by a conjugate of a tumor-specific ligand folate and an oligonucleotide. After washing off redundant conjugates, the bound conjugates were removed and analyzed by quantitative polymerase chain reaction. The captured cells were validated as tumor cells by immunofluorescence staining. In the evaluation of clinical utility, the results showed that the CTC levels of 153 patients with NSCLC were significantly higher than the controls (49 healthy donors and 64 patients with benign lung diseases; P < .001). With a threshold of 8.64 CTC units, the method showed a sensitivity of 73.2% and a specificity of 84.1% in the diagnosis of NSCLC, especially a sensitivity of 67.2% in stage I disease. Compared with the existing clinical biomarkers such as neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), cancer antigen 125 (CA125), cyfra21-1, and squamous cell carcinoma antigen (SCC Ag), the method showed the highest diagnostic efficiency (area under the curve, 0.823; 95% confidence interval, 0.773-0.874). Together, our results demonstrated that FR-positive CTCs were feasible diagnostic biomarkers in patients with NSCLC, as well as in early-stage tumors.

Clinical utility of circulating tumor cells in patients with non-small-cell lung cancer

“…These studies have shown that by using folate receptor as a marker it is possible to discriminate between NSCLC patients, individuals with benign lung disease and healthy subjects. A sensitivity up to 77.7% and a specificity up to 89.5% for the diagnosis of NSCLC was reported (7,9). However, it must be emphasized that the sensitivity was higher for stage IV patients, while it was <70% in stage I.…”

“…Different studies have used the folate receptor transcript as a marker to identify the CTC (7)(8)(9). In fact, folate receptor is often expressed in NSCLC cells whereas its levels of expression are usually low in blood cells.…”

Detection of circulating tumor cells in non-small cell lung cancer

“…Thus, LT-PCR would allow enumeration of CTCs in NSCLC patients at high sensitivity, especially at early stage. In a similar trial by Yu et al, CTC levels of 153 patients with NSCLC were found to be significantly higher than that of controls (17). With a threshold of 8.64 CUs, the method showed a sensitivity of 73% and a specificity of 84% in the diagnosis of NSCLC.…”

“…Recent estimates suggest that many human carcinomas overexpress FOLR1, including >90% of ovarian and endometrial cancers, >85% of kidney cancers and approximately 80% of NSCLCs, among others. Therefore, FOLR1 may be a potential target for capturing CTCs in patients with NSCLC (17). With the advent of targeted therapies directed towards FOLR1, with several such agents in late stage clinical development, the detection of FOLR1 in tissues is of import for patient selection and possibly prognosis and prediction of response.…”

Novel method for the detection and quantification of malignant cells in the CSF of patients with leptomeningeal metastasis of lung cancer

“…Previous studies demonstrated that circulating tumor cells (CTCs), particularly deciduous solid tumor cells, in the blood are associated with tumor metastasis, drug resistance (6), prognosis and recurrence (7,8). CTCs may also associate with non-hematogenous epithelial cells, and the majority of CTCs express cytokeratin (CK) in epithelial cells.…”